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  Subjects -> COMPUTER SCIENCE (Total: 2016 journals)
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COMPUTER SCIENCE (1175 journals)                  1 2 3 4 5 6 | Last

Showing 1 - 200 of 872 Journals sorted alphabetically
3D Printing and Additive Manufacturing     Full-text available via subscription   (Followers: 16)
Abakós     Open Access   (Followers: 4)
ACM Computing Surveys     Hybrid Journal   (Followers: 24)
ACM Journal on Computing and Cultural Heritage     Hybrid Journal   (Followers: 9)
ACM Journal on Emerging Technologies in Computing Systems     Hybrid Journal   (Followers: 13)
ACM Transactions on Accessible Computing (TACCESS)     Hybrid Journal   (Followers: 4)
ACM Transactions on Algorithms (TALG)     Hybrid Journal   (Followers: 16)
ACM Transactions on Applied Perception (TAP)     Hybrid Journal   (Followers: 6)
ACM Transactions on Architecture and Code Optimization (TACO)     Hybrid Journal   (Followers: 9)
ACM Transactions on Autonomous and Adaptive Systems (TAAS)     Hybrid Journal   (Followers: 7)
ACM Transactions on Computation Theory (TOCT)     Hybrid Journal   (Followers: 12)
ACM Transactions on Computational Logic (TOCL)     Hybrid Journal   (Followers: 3)
ACM Transactions on Computer Systems (TOCS)     Hybrid Journal   (Followers: 19)
ACM Transactions on Computer-Human Interaction     Hybrid Journal   (Followers: 15)
ACM Transactions on Computing Education (TOCE)     Hybrid Journal   (Followers: 6)
ACM Transactions on Design Automation of Electronic Systems (TODAES)     Hybrid Journal   (Followers: 2)
ACM Transactions on Economics and Computation     Hybrid Journal  
ACM Transactions on Embedded Computing Systems (TECS)     Hybrid Journal   (Followers: 4)
ACM Transactions on Information Systems (TOIS)     Hybrid Journal   (Followers: 21)
ACM Transactions on Intelligent Systems and Technology (TIST)     Hybrid Journal   (Followers: 8)
ACM Transactions on Interactive Intelligent Systems (TiiS)     Hybrid Journal   (Followers: 4)
ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP)     Hybrid Journal   (Followers: 10)
ACM Transactions on Reconfigurable Technology and Systems (TRETS)     Hybrid Journal   (Followers: 7)
ACM Transactions on Sensor Networks (TOSN)     Hybrid Journal   (Followers: 9)
ACM Transactions on Speech and Language Processing (TSLP)     Hybrid Journal   (Followers: 10)
ACM Transactions on Storage     Hybrid Journal  
ACS Applied Materials & Interfaces     Full-text available via subscription   (Followers: 25)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Universitatis Cibiniensis. Technical Series     Open Access  
Ad Hoc Networks     Hybrid Journal   (Followers: 11)
Adaptive Behavior     Hybrid Journal   (Followers: 11)
Advanced Engineering Materials     Hybrid Journal   (Followers: 26)
Advanced Science Letters     Full-text available via subscription   (Followers: 9)
Advances in Adaptive Data Analysis     Hybrid Journal   (Followers: 7)
Advances in Artificial Intelligence     Open Access   (Followers: 16)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 6)
Advances in Computational Mathematics     Hybrid Journal   (Followers: 18)
Advances in Computer Science : an International Journal     Open Access   (Followers: 15)
Advances in Computing     Open Access   (Followers: 2)
Advances in Data Analysis and Classification     Hybrid Journal   (Followers: 52)
Advances in Engineering Software     Hybrid Journal   (Followers: 27)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 11)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 27)
Advances in Human-Computer Interaction     Open Access   (Followers: 21)
Advances in Materials Sciences     Open Access   (Followers: 16)
Advances in Operations Research     Open Access   (Followers: 12)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Remote Sensing     Open Access   (Followers: 41)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Advances in Technology Innovation     Open Access   (Followers: 4)
AEU - International Journal of Electronics and Communications     Hybrid Journal   (Followers: 8)
African Journal of Information and Communication     Open Access   (Followers: 8)
African Journal of Mathematics and Computer Science Research     Open Access   (Followers: 4)
Air, Soil & Water Research     Open Access   (Followers: 9)
AIS Transactions on Human-Computer Interaction     Open Access   (Followers: 6)
Algebras and Representation Theory     Hybrid Journal   (Followers: 1)
Algorithms     Open Access   (Followers: 11)
American Journal of Computational and Applied Mathematics     Open Access   (Followers: 5)
American Journal of Computational Mathematics     Open Access   (Followers: 4)
American Journal of Information Systems     Open Access   (Followers: 5)
American Journal of Sensor Technology     Open Access   (Followers: 4)
Anais da Academia Brasileira de Ciências     Open Access   (Followers: 2)
Analog Integrated Circuits and Signal Processing     Hybrid Journal   (Followers: 7)
Analysis in Theory and Applications     Hybrid Journal   (Followers: 1)
Animation Practice, Process & Production     Hybrid Journal   (Followers: 5)
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Data Science     Hybrid Journal   (Followers: 11)
Annals of Mathematics and Artificial Intelligence     Hybrid Journal   (Followers: 12)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of Software Engineering     Hybrid Journal   (Followers: 13)
Annual Reviews in Control     Hybrid Journal   (Followers: 6)
Anuario Americanista Europeo     Open Access  
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applied and Computational Harmonic Analysis     Full-text available via subscription   (Followers: 1)
Applied Artificial Intelligence: An International Journal     Hybrid Journal   (Followers: 13)
Applied Categorical Structures     Hybrid Journal   (Followers: 2)
Applied Clinical Informatics     Hybrid Journal   (Followers: 2)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 12)
Applied Computer Systems     Open Access   (Followers: 2)
Applied Informatics     Open Access  
Applied Mathematics and Computation     Hybrid Journal   (Followers: 33)
Applied Medical Informatics     Open Access   (Followers: 10)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Soft Computing     Hybrid Journal   (Followers: 15)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 5)
Applied System Innovation     Open Access  
Architectural Theory Review     Hybrid Journal   (Followers: 3)
Archive of Applied Mechanics     Hybrid Journal   (Followers: 5)
Archive of Numerical Software     Open Access  
Archives and Museum Informatics     Hybrid Journal   (Followers: 137)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 4)
Artifact     Hybrid Journal   (Followers: 2)
Artificial Life     Hybrid Journal   (Followers: 7)
Asia Pacific Journal on Computational Engineering     Open Access  
Asia-Pacific Journal of Information Technology and Multimedia     Open Access   (Followers: 1)
Asian Journal of Computer Science and Information Technology     Open Access  
Asian Journal of Control     Hybrid Journal  
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
Australian Educational Computing     Open Access   (Followers: 1)
Automatic Control and Computer Sciences     Hybrid Journal   (Followers: 4)
Automatic Documentation and Mathematical Linguistics     Hybrid Journal   (Followers: 5)
Automatica     Hybrid Journal   (Followers: 11)
Automation in Construction     Hybrid Journal   (Followers: 6)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 9)
Basin Research     Hybrid Journal   (Followers: 5)
Behaviour & Information Technology     Hybrid Journal   (Followers: 52)
Big Data and Cognitive Computing     Open Access  
Biodiversity Information Science and Standards     Open Access  
Bioinformatics     Hybrid Journal   (Followers: 287)
Biomedical Engineering     Hybrid Journal   (Followers: 15)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 14)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 18)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 34)
Briefings in Bioinformatics     Hybrid Journal   (Followers: 47)
British Journal of Educational Technology     Hybrid Journal   (Followers: 138)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
c't Magazin fuer Computertechnik     Full-text available via subscription   (Followers: 2)
CALCOLO     Hybrid Journal  
Calphad     Hybrid Journal  
Canadian Journal of Electrical and Computer Engineering     Full-text available via subscription   (Followers: 14)
Capturing Intelligence     Full-text available via subscription  
Catalysis in Industry     Hybrid Journal   (Followers: 1)
CEAS Space Journal     Hybrid Journal   (Followers: 2)
Cell Communication and Signaling     Open Access   (Followers: 2)
Central European Journal of Computer Science     Hybrid Journal   (Followers: 5)
CERN IdeaSquare Journal of Experimental Innovation     Open Access   (Followers: 1)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 14)
ChemSusChem     Hybrid Journal   (Followers: 7)
China Communications     Full-text available via subscription   (Followers: 7)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
CIN Computers Informatics Nursing     Full-text available via subscription   (Followers: 11)
Circuits and Systems     Open Access   (Followers: 15)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
CLEI Electronic Journal     Open Access  
Clin-Alert     Hybrid Journal   (Followers: 1)
Cluster Computing     Hybrid Journal   (Followers: 1)
Cognitive Computation     Hybrid Journal   (Followers: 4)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 14)
Communication Methods and Measures     Hybrid Journal   (Followers: 12)
Communication Theory     Hybrid Journal   (Followers: 20)
Communications Engineer     Hybrid Journal   (Followers: 1)
Communications in Algebra     Hybrid Journal   (Followers: 3)
Communications in Partial Differential Equations     Hybrid Journal   (Followers: 3)
Communications of the ACM     Full-text available via subscription   (Followers: 55)
Communications of the Association for Information Systems     Open Access   (Followers: 18)
COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering     Hybrid Journal   (Followers: 3)
Complex & Intelligent Systems     Open Access   (Followers: 1)
Complex Adaptive Systems Modeling     Open Access  
Complex Analysis and Operator Theory     Hybrid Journal   (Followers: 2)
Complexity     Hybrid Journal   (Followers: 6)
Complexus     Full-text available via subscription  
Composite Materials Series     Full-text available via subscription   (Followers: 9)
Computación y Sistemas     Open Access  
Computation     Open Access  
Computational and Applied Mathematics     Hybrid Journal   (Followers: 2)
Computational and Mathematical Methods in Medicine     Open Access   (Followers: 2)
Computational and Mathematical Organization Theory     Hybrid Journal   (Followers: 2)
Computational and Structural Biotechnology Journal     Open Access   (Followers: 2)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Astrophysics and Cosmology     Open Access   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 11)
Computational Chemistry     Open Access   (Followers: 2)
Computational Cognitive Science     Open Access   (Followers: 2)
Computational Complexity     Hybrid Journal   (Followers: 4)
Computational Condensed Matter     Open Access  
Computational Ecology and Software     Open Access   (Followers: 9)
Computational Economics     Hybrid Journal   (Followers: 9)
Computational Geosciences     Hybrid Journal   (Followers: 15)
Computational Linguistics     Open Access   (Followers: 22)
Computational Management Science     Hybrid Journal  
Computational Mathematics and Modeling     Hybrid Journal   (Followers: 8)
Computational Mechanics     Hybrid Journal   (Followers: 4)
Computational Methods and Function Theory     Hybrid Journal  
Computational Molecular Bioscience     Open Access   (Followers: 2)
Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computational Particle Mechanics     Hybrid Journal   (Followers: 1)
Computational Research     Open Access   (Followers: 1)
Computational Science and Discovery     Full-text available via subscription   (Followers: 2)
Computational Science and Techniques     Open Access  
Computational Statistics     Hybrid Journal   (Followers: 14)
Computational Statistics & Data Analysis     Hybrid Journal   (Followers: 30)
Computer     Full-text available via subscription   (Followers: 91)
Computer Aided Surgery     Hybrid Journal   (Followers: 5)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 8)
Computer Communications     Hybrid Journal   (Followers: 10)
Computer Engineering and Applications Journal     Open Access   (Followers: 5)
Computer Journal     Hybrid Journal   (Followers: 9)
Computer Methods in Applied Mechanics and Engineering     Hybrid Journal   (Followers: 22)
Computer Methods in Biomechanics and Biomedical Engineering     Hybrid Journal   (Followers: 12)
Computer Methods in the Geosciences     Full-text available via subscription   (Followers: 2)
Computer Music Journal     Hybrid Journal   (Followers: 18)
Computer Physics Communications     Hybrid Journal   (Followers: 6)
Computer Science - Research and Development     Hybrid Journal   (Followers: 8)
Computer Science and Engineering     Open Access   (Followers: 19)
Computer Science and Information Technology     Open Access   (Followers: 13)

        1 2 3 4 5 6 | Last

Journal Cover Advanced Engineering Materials
  [SJR: 0.81]   [H-I: 81]   [26 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1438-1656 - ISSN (Online) 1527-2648
   Published by John Wiley and Sons Homepage  [1592 journals]
  • Sound Transmission Loss Enhancement in an Inorganic-Organic Laminated Wall
           Panel Using Multifunctional Low-Density Nanoporous Polyurea Aerogels:
           Experiment and Modeling
    • Authors: Sadeq Malakooti; Habel Gitogo Churu, Alison Lee, Saman Rostami, Samuel John May, Suzie Ghidei, Fen Wang, Qun Lu, Huiyang Luo, Ning Xiang, Chariklia Sotiriou-Leventis, Nicholas Leventis, Hongbing Lu
      Abstract: Recently, the authors have reported an exceptional normal incidence sound transmission loss characteristic for a class of low density, highly porous, and mechanically strong polyurea aerogels. Herein, a laminated composite comprising the organic low-density aerogels bonded with an inorganic compound (e.g., gypsum materials) is considered to investigate the constrained damping effects of the aerogels on the airborne sound insulation behavior of the composite using the standard chamber-based diffuse sound field measurements. Huge improvement in the sound transmission loss is obtained due to the use of aerogel without a significant increase in the overall weight and thickness of the composite panel (e.g., more than 10 dB increase by reaching 40 dB sound transmission loss at 2 kHz after the implementation of only two 5 mm-thick aerogel layers at bulk densities 0.15 and 0.25 g cm−3). This uncommon behavior breaks the empirical “Mass Law” nature of the most conventional acoustic materials. In addition, an exact analytical time-harmonic plane-strain solution for the diffused wave propagation through the multilayered structure is provided using theories of linear elasticity and Biot's dynamic poroelasticity. The theoretical results are well supported by the experiments which can be utilized for the design of the future light-weight multifunctional composite structures.Herein, an uncommon sound transmission behavior for a composite panel containing low-density nanoporous polyurea aerogels is reported. In contrast with conventional mass-law obeyed materials, the aerogels can noticeably enhance the composite's sound transmission loss without a significant change in the overall weight and thickness of the panel.
      PubDate: 2018-02-20T09:30:50.636974-05:
      DOI: 10.1002/adem.201700937
  • Metallurgical Strategies for the Joining of Titanium Alloys with Steels
    • Authors: Iryna Tomashchuk; Pierre Sallamand
      Abstract: Welding of titanium alloys with steels presents a high risk of cold cracking because of the formation of extremely brittle intermetallic phases associated with residual stress. The use of solid state and diffusion-based methods as well as a high power beam welding allow so far to achieve good tensile properties through the control of a local phase content. This review summarizes existing approaches for the creation of defect-free joints between titanium alloys and steels: direct joining without a filler material, the use of insert having full metallurgical compatibility with titanium, the use of insert compatible with stainless steel, and multilayer engineering.For successful joining of titanium alloys with steels, different methods and approaches can be used to avoid the accumulation of brittle intermetallic phases. The present review summarizes existing possibilities to use different metallic interlayers as well as describes existing methods of direct joining. The most promising approach nowaday is to combine Ti-compatible and Fe-compatible materials into multilayer inserts.
      PubDate: 2018-02-20T09:20:44.833123-05:
      DOI: 10.1002/adem.201700764
  • High Entropy Alloys: Prospective Materials for Tribo-Corrosion
    • Authors: Rakesh Bhasakaran Nair; Harpreet Singh Arora, Aditya Ayyagari, Sundeep Mukherjee, Harpreet Singh Grewal
      Abstract: Tribo-corrosion is an issue of concern for marine and other fluid machinery. High entropy alloys (HEAs) represent a new category of materials possessing exceptional properties. We investigated the erosion-corrosion behavior of Al0.1CoCrFeNi HEA. For comparison, stainless steel SS316L is also evaluated. Results indicate that despite low hardness and yield strength, HEA exhibits high erosion-corrosion resistance compared to steel. The HEA also shows high pitting and passive potentials compared to steel. The superior erosion-corrosion resistance of HEA is due to high corrosion resistance, and work hardenability. The degradation mechanism investigated using SEM show ploughing as the primary material removal mode (MRM) for HEA at an oblique angle compared to micro-cutting for SS316L steel. At normal impingement, platelet mechanism is observed to be the dominant MRM.High entropy alloys (HEA) possess extraordinary mechanical and corrosion properties making it prospective material for tribo-corrosion applications. The Al0.1CoCrFeNi HEA shows around two times higher resistance tribo-corrosion resistance at an oblique angle along with several-folds lower corrosion rates than stainless steel used as reference materials. Higher corrosion resistance of the HEA also results in negative synergy highlighting superior tribo-corrosion performance.
      PubDate: 2018-02-20T08:45:36.98172-05:0
      DOI: 10.1002/adem.201700946
  • Back Cover: Advanced Engineering Materials 2∕2018
    • Abstract: The image shows Liquid PMMA a fast curing PMMA prepolymer which can be used as a negative photoresist. This new material enables direct structuring of optically transparent microfluidic chips using light and thereby offers a simple method for rapid prototyping in one of the most important industrial thermoplasts. Further details can be found in article 1700699 by Bastian E. Rapp and co-workers.
      PubDate: 2018-02-16T04:04:12.601004-05:
      DOI: 10.1002/adem.201870006
  • Front Cover: Advanced Engineering Materials 2∕2018
    • Abstract: Inspired by the responsive chromatophores on the skin of Cephalopods, novel hybrid auxetic chiral mechanical metamaterials are designed and fabricated via 3D printing to achieve dramatic volume change and a unique sequential cell opening mechanism. The new concepts can be applied in designing smart metamaterials for actuation, drug delivery and color change for camouflage. Further details can be found in article 1700744 by Yunyao Jiang and Yaning Li.
      PubDate: 2018-02-16T04:04:11.47279-05:0
      DOI: 10.1002/adem.201870004
  • Masthead: Adv. Eng. Mater. 2∕2018
    • PubDate: 2018-02-16T04:04:08.289623-05:
      DOI: 10.1002/adem.201870005
  • Chemically Modified Silk Proteins
    • Authors: Jianming Chen; Harun Venkatesan, Jinlian Hu
      Abstract: Silks are of central importance as smart natural biomaterials and are attracting increasing attention for their biomimetic potential due to their sophisticated molecular structure, self-assembly mechanism, impressive mechanical properties, biocompatibility, and biodegradability. The versatility of silk proteins (SP) allows the chemical modification of silk-based materials with diverse morphologies under harsh conditions. The chemical modification of amino acids within SP enables the expanded generation of new biomaterials and the extension of their potential functional applications. The authors review the current chemical modification strategies and routes for the functionalization of SP.This paper reviews recent advances in the development of chemically modified silk proteins for biomedical applications. Reactive groups in amino acids enable the chemical modification of silk proteins in various morphogies. Silk proteins are exemplified to show functionalization with peptides/enzymes, organic ligands, polymers, and minerals by the grafting reaction, coupling reaction, and amino acid modification.
      PubDate: 2018-02-15T07:50:48.254058-05:
      DOI: 10.1002/adem.201700961
  • Effect of Alumina Nanoparticles on the Microstructure, Texture, and
           Mechanical Properties of Ultrafine-Grained Aluminum Processed by
           Accumulative Roll Bonding
    • Authors: Konstantin V. Ivanov; Sergey V. Fortuna, Tatyana A. Kalashnikova, Elena A. Glazkova
      Abstract: An Al–0.05 vol% nAl2O3 (where nAl2O3 is alumina nanoparticles) composite has been fabricated using accumulative roll bonding with nanoparticle introduction. The microstructure, texture, fracture surfaces, and mechanical properties are investigated using transmission and scanning electron microscopy, electron back scatter diffraction (EBSD), microhardness measurement and tensile tests. The results show that nanoparticle introduction significantly affects the microstructure, texture, and fracture characteristics, but weakly influences the microhardness, strength, and ductility. The possible reasons for the different responses of the studied properties to nanoparticle introduction during accumulative roll bonding are discussed.It is shown that alumina nanoparticle introduction into aluminum during accumulative roll bonding significantly affects the microstructure, texture, and fracture characteristics but weakly influences the microhardness, strength, and ductility. Dynamic recrystallization during ARB is considered the main factor determining the different response of the material to nanoparticle introduction.
      PubDate: 2018-02-15T03:16:05.844357-05:
      DOI: 10.1002/adem.201701135
  • An Unusual Texture Evolution in Extruded Mg–14Gd–Based Alloy
           during Annealing
    • Authors: Rongguang Li; Jinghuai Zhang, Guangyan Fu, Lin Zong, Beitao Guo, Yongmei Yu, Shuguo Guo
      Abstract: Texture evolution during annealing in various wrought Mg alloys is still controversial and texture control is an effective way of reducing mechanical anisotropy and improving secondary formability for Mg alloys. In this study, the electron backscattered diffraction (EBSD) method is used to monitor the texture evolution during the annealing process of a Mg–14Gd–2Ag–0.5Zr extruded bar. The novel phenomenon, that is, the texture evolution from ⊥ED to ED, or rather, the increase fraction of grains with ED accompanied by the decrease fraction of grains with ⊥ED, is found and discussed in the high-RE containing Mg alloy for the first time. The effect factors, stored energy in different textured grains and grain boundary misorientation, are mentioned to analyze the texture evolution.The weak ED texture of extruded high-RE containing Mg alloy evolves into an unusual ED texture during annealing. The evolution accompanied with the increased fraction of ED grains and the decreased fraction of ⊥ED grains is mainly related to the different stored energy and the grain boundary misorientation.
      PubDate: 2018-02-13T07:00:52.492752-05:
      DOI: 10.1002/adem.201701129
  • Bilayer SiO2 Nanorod Arrays as Omnidirectional and Thermally Stable
           Antireflective Coating
    • Authors: Sadaf B. Khan; Hui Wu, Jianghao Li, Limin Chen, Zhengjun Zhang
      Abstract: Nature instigates researchers significantly in imitating to engender comparable properties using artificial methods, which unlocks developing trend in material science and engineering progress. Fabricating graded-index nanostructures is an effective approach to tune and generate similar properties artificially such as the moth's eye antireflectance (AR) or lotus like superhydrophobicity. Herein, Bilayer AR coatings with periodically arranged SiO2 hierarchical nanostructures resembling moth eyes are fabricated on dense SiO2 matrix base layer using the versatile route of glancing angle deposition technique (GLAD). The refractive indices of monolayer SiO2 are tuned from 1.46 to 1.08 by changing the deposition angle (α) from 0 to 88°. The fabricated bilayer SiO2 AR (BSAR) film possess high optical omnidirectional broadband transparency and tunability at a desired wavelength range showing
      PubDate: 2018-02-12T07:36:17.215941-05:
      DOI: 10.1002/adem.201700942
  • Design, Fabrication, and Characterization of Porous Yttria-Stabilized
           Zirconia Ceramics for Hot Gas Filtration Applications
    • Authors: Shayan Shahini; William D. Judge, Jason Tam, Gisele Azimi
      Abstract: Hot gas filtration is a lucrative target for a number of high temperature industrial operations, but new materials must be developed to withstand intense high temperature conditions. Here, the authors put the emphasis on porous yttria-stabilized zirconia (YSZ) ceramics for hot gas filtration, owing to their high thermodynamic stability and toughness. The authors design and fabricate porous YSZ ceramics using a pore-forming inclusion technique, where a polymeric pore former is mixed and compacted with YSZ powder. After burning off, the polymer leaves behind a controlled amount of porosity before sintering commenced. The authors systematically investigate the sintering temperature, polymer particle size, and polymer-to-ceramic ratio to optimize the open porosity, pore size, gas permeability, and hardness of porous YSZ ceramics. The authors then evaluate the performance of porous YSZ ceramics under industrial conditions by cyclic heating/cooling testing and high temperature exposure testing. The authors show, for the first time, porous YSZ ceramics can perform in hot gas filtration applications at 1400 °C for extended thermal cycling or at 1700 °C for limited periods of time.The authors present an approach to design and fabricate porous yttria-stabilized zirconia ceramics for applications in hot gas filtration. The authors use a pore-forming inclusion technique to engineer their open porosity, pore size, gas permeability, and hardness by controlling the fabrication conditions including sintering temperature, polymer particle size, and polymer-to-ceramic ratio. The authors demonstrate that the ceramic filters can perform in hot gas filtration at 1400 °C for extended thermal cycling and up to 1700 °C for limited periods of time.
      PubDate: 2018-02-12T07:25:50.128371-05:
      DOI: 10.1002/adem.201700941
  • Enhanced Tensile Properties and Fracture Reliability of Cu-Based Amorphous
           Wires via Pr-Doping
    • Authors: Jingshun Liu; Yun Zhang, Qixiang Wang, Mengjun Wu, Ding Nan, Hongxian Shen, Huaxin Peng
      Abstract: This paper proposed a novel wire-preparation technique integrated Pr-doping to improve the tensile properties of rotation-dipped Cu-based amorphous wires, and systematically investigates the fracture reliability and fracture mechanism of them. Meanwhile, the mechanical properties are evaluated through tensile tests, and their fracture reliability is estimated by using two- and three-parameter Weibull statistics and lognormal plotting. Experimental results indicate that the Cu-based wires have entirely amorphous microstructure, a smooth surface and circular cross-section, and exhibit a relatively higher working temperature. Both the Cu–Zr–Ti and Cu–Zr–Ti–Pr wires represent the higher tensile strengths. In comparison with Cu–Zr–Ti wires, Cu–Zr–Ti–Pr wires possess a maximum tensile strength and ductility of 2.07 GPa and 0.92%, respectively. Meanwhile, Cu–Zr–Ti–Pr wires also exhibit a larger Weibull modulus, which stand for the fracture reliability in Weibull statistics, and higher fracture threshold stress (≈1.42 GPa). Essentially, both fracture of two types of Cu-based wires take on a brittle fracture characteristic with crack extension region and shear deformation region, and the improved tensile property after Pr-doping is probably attributed to the strengthened interaction of shear bands and micropore gathering (vein-shaped pattern forming). Therefore, it can be concluded that the Cu-based microwires with enhanced tensile property as the ideal candidates including miniaturized components are used for potential electronics engineering and biomedical implantation applications.Tensile properties of Cu-based microwires are effectively enhanced by using Pr-doping in comparison with strain–stress curves. Fracture morphology of both side view and front view shows typical fracture regions. Moreover, tensile deformation process of Cu-based wires includes four stages: elastic deformation, free volume gathered and rheological defect fusion, growth of shear band and the formation of vein-shaped pattern, and fracture.
      PubDate: 2018-02-12T02:42:12.377916-05:
      DOI: 10.1002/adem.201700935
  • Interaction of NiAl Intermetallic During SHS Synthesis with Ta Substrate
    • Authors: Alexander S. Shchukin; Dominique Vrel, Аlexander E. Sytschev
      Abstract: NiAl intermetallic is obtained during exothermic reaction of mechanically activated Ni and Al powders, taking place by thermal explosion (TE) mode of self-propagating high-temperature synthesis (SHS). When a layer of Ni–Al blend is placed in contact with Ta substrate, the heat this exothermic reaction results in reaction multilayer with composition corresponding to intermetallic predicted by Ta–Ni–Al ternary phase diagram. The used approach is proposed for processing of oxidation resistant coating on Ta as well as for joining of parts from ta and its alloys.Ta substrate and Ni–Al powder mixtures are successfully joined via thermal explosion with the formation of a narrow multilayer transition zone. The layer nearest to the Ta substrate has a uniform composition and a thickness of 0.25–0.6 μm. The composition of this phase is close to Ta5Ni2Al3 phase. According to the EDS data, the composition of next layer with a thickness about 1 ÷ 2 μm is close to the ternary compound TaNiAl (Laves Phase), which has a wide range of Ni homogeneity.
      PubDate: 2018-02-12T02:41:31.119296-05:
      DOI: 10.1002/adem.201701077
  • The Solid Flame Phenomenon: A Novel Perspective
    • Authors: Alexander S. Mukasyan; Christopher E. Shuck, Joshua M. Pauls, Khachatur V. Manukyan, Dmitry O. Moskovskikh, Alexander S. Rogachev
      Abstract: In this paper, the authors overview previous publications and present novel results related to self-sustained solid-state reactions: the solid flame. Due to recent advances in the fabrication of nano-structured reactive media, this phenomenon, which is first reported fifty years ago, has found a new perspective for a wide variety of exothermic systems. These fundamental findings permit novel routes for synthesis of advanced engineering materials with controlled microstructure, as well as for design of high-energy density systems with tuned parameters for energy release.Short-term high-energy ball treatment of powder mixtures is an effective tool to achieve the necessary conditions for the solid flame phenomenon. It is important that this phenomenon can be accomplished in systems (Ta/C, Si/C, TiN/B, Ni/Al) with different thermodynamic characteristics and phase diagrams. These fundamental findings permit novel routes for synthesis of advanced materials with controlled microstructures.
      PubDate: 2018-02-12T02:41:25.153966-05:
      DOI: 10.1002/adem.201701065
  • Recent Advances of Low Biological Toxicity Ag2S QDs for Biomedical
    • Authors: Chenghao Lu; Guihuan Chen, Bing Yu, Hailin Cong
      Abstract: In this review, the synthesis and biomedical application of Ag2S quantum dots(QDs) are comprehensively summarized with a particular focus on biological imaging and nanomedicine. For the first, the authors introduce the optical properties of Ag2S QDs, and then, the auhtors summarize a range of synthetic methods for Ag2S QDs. The subsequent section provides the applications of Ag2S QDs in optical imaging, photoacoustic imaging, sensing, optical tracking, and photothermal therapy. Finally, the authors provide insights into the overall situation, challenges, and future directions in this field.In this review, the synthesis and biomedical application of Ag2S QDs are comprehensively summarized, with a particular focus on biological imaging and nanomedicine. Surface modification enables Ag2S QDs to be used in vivo imaging, photothermal therapy, photoacoustic(PA), drug therapy, and multi-functional diagnosis.
      PubDate: 2018-02-09T08:31:01.560536-05:
      DOI: 10.1002/adem.201700940
  • Atomic-Scale Insight into Structure and Interface of Al2Y Phase in an
           Mg–Al–Y Alloy
    • Authors: Z. Z. Peng; X. H. Shao, X. W. Guo, J. Wang, Y. J. Wang, X. L. Ma
      Abstract: Atomic-scale structure of Al2Y phase and its interface with magnesium matrix in an Mg–1Al–6.2Y (wt%) alloy have been investigated using scanning transmission electron microscopy (STEM) and density-functional theory (DFT). Apart from micro-sized Al2Y particles in the interior of grains or along grain boundaries, nano-sized Al2Y lamella with a large aspect ratio precipitates within the grains. Y − enriched stacking faults are introduced at the lamellar Al2Y/Mg interface due to 0.07% lattice misfit between (022)Al2Y and (01¯10)Mg planes. The first-principles simulation clarifies that Al2Y/Mg interface is energetically occupied by Al atoms other than Y atoms.Atomic-scale structure of Al2Y phase and its interface with magnesium matrix in an Mg–1Al–6.2Y (wt%) alloy have been investigated using scanning transmission electron microscopy (STEM) and density-functional theory (DFT). Some micro-sized Al2Y particles, as well as all the nano-sized Al2Y precipitates, have good orientation relationship with matrix. The interfacial structure of Al2Y with the magnesium matrix is further rationalized by First-principle simulation, demonstrating that Al2Y/Mg interface is energetically occupied by Al atoms other than Y atoms.
      PubDate: 2018-02-08T08:50:46.039799-05:
      DOI: 10.1002/adem.201701015
  • High-Cycle Fatigue Behavior and Damage Mechanism of Multiphase Al–Si
           Piston Alloy at Room and Elevated Temperatures
    • Authors: Haiquan Liu; Jianchao Pang, Meng Wang, Shouxin Li, Zhefeng Zhang
      Abstract: Microstructure evolution, tensile properties, fatigue crack initiation and propagation behaviors, and corresponding damage mechanisms of a multiphase cast Al–Si alloy used for pistons at room temperature (RT), 350 and 425 °C are investigated. The results show that tensile and fatigue strengths decrease with the increase of temperature. Casting defects such as pores and oxide films are the most preferential sites for fatigue initiation at all the temperatures. The preferential propagation path for fatigue crack is mainly through the Al matrix and second phases at room temperature, through Al matrix at 350 °C, and along grain boundary and phase/matrix interface at 425 °C. This may be attributed to the reduction of strengths of matrix and phase/matrix interface at elevated temperatures. Relationship between fatigue strength and defect size is also discussed using critical stress intensity factor and probability distribution of defect size.Casting defects are the most preferential sites for fatigue initiation both at room and elevated temperatures. The preferential propagation path for fatigue crack is mainly through the Al matrix and second phases at room temperature, through Al matrix at 350 °C, and along grain boundary and phase/matrix interface at 425 °C.
      PubDate: 2018-02-06T07:42:04.846708-05:
      DOI: 10.1002/adem.201700972
  • Processing Map and Hot Working Mechanism of As-Cast
           Ti–42Al–5Mn Alloy
    • Authors: Hao Xu; Xiaobing Li, Weiwei Xing, Lei Shu, Yingche Ma, Kui Liu
      Abstract: The research is focused on the hot deformation behavior of Ti–42Al–5Mn (at%) ingot produced by vacuum induction melting (VIM) and vacuum arc remelting (VAR). Firstly, the isothermal compression test is performed at the temperatures between 1100 and 1300 °C with the strain rates in the range of 0.001–10 s−1. The processing map is plotted on the base of the strain–stress curves, and the constitutive equation is also established by regression analysis based on the experimental results. Secondly, different deformation features in β, γ phase, and γ lath of lamellae are investigated by electron probe micro analyzer (EPMA) and transmission electron microscope (TEM). The results reveal that, the alloy can be hot worked from 1300 °C–10 s−1 to 1100 °C–0.1 s−1, and the stress exponent and apparent activation energy are calculated to be 2.71 and 597 kJ mole−1, respectively. It shows that, during the isothermal compression process, the γ phase usually has a higher dislocation density than β phase, and the γ lath of lamellae has generated both dislocation glide and deformation twinning.The paper is focused on the hot deformation behavior of as-cast Ti–42Al–5Mn alloy. The processing map and constitutive equation are conducted by isothermal compression test. It reveals that the alloy can be hot worked from 1300 °C–10 s−1 to 1100 °C–0.1 s−1. TEM results show γ phase has higher dislocation density than β phase, and γ lath generates both dislocation glide and deformation twinning.
      PubDate: 2018-02-06T03:06:08.160757-05:
      DOI: 10.1002/adem.201701059
  • Influence of Transient Liquid Phase Promoting Additives upon Reactive
           Plasma Spraying of AlN Coatings and Its Properties
    • Authors: Mohammed Shahien; Motohiro Yamada, Masahiro Fukumoto
      Abstract: The feasibility of using a transient liquid phase promoting agent upon reactive plasma spraying (RPS) of AlN coatings in atmospheric ambient is successfully investigated. Several sprayable fine AlN–Al2O3–Y2O3 mixtures with different compositions are prepared by spray-drying. Upon plasma spraying in N2/H2 plasma, thick and homogeneous AlN based coatings (h-AlN, c-AlN, γ-Al2O3, Al5O6N, α-Al2O3, and YAG) are fabricated. Fine Y2O3 acts as transient liquid phase promoting additive, and reacts with Al2O3 phase (from feedstock mixture and on AlN particles surface) to create wetting agent of yttrium aluminate Y–Al–O around solid AlN particles. However, due to rapid solidification rates of plasma, it is difficult to react with the interspersed oxygen in AlN grains. The Y2O3 addition significantly reduces the coatings oxide content due to the consumption of starting Al2O3 to form the YAG. Influence of Y2O3 significantly observes with increasing AlN feedstock and high AlN content coatings with small oxides are fabricated by RPS of 80AlN–10Al2O3–10Y2O3 mixture. Thermal conductivity is improved with using Y2O3 and increasing AlN feedstock. However, the conductivity is not so high compared to the AlN compacts, due to increased porosity, incomplete sintering of the formed initial liquid phase state, remaining oxide content, and low density of the coatings.Using transient liquid phase promoting additives upon reactive plasma spraying of AlN coatings was investigated. Several thick AlN coatings were fabricated via spraying AlN–Al2O3–Y2O3 mixtures in N2/H2 plasma. Y2O3 acts as transient liquid phase promoting additive, and reacts with A12O3 phase to create a wetting agent (Y–Al–O) around AlN solid particles. Y2O3 significantly affects the coating composition, microstructure, and properties..
      PubDate: 2018-02-05T10:26:39.316209-05:
      DOI: 10.1002/adem.201700917
  • A Review of Metal Fabricated with Laser- and Powder-Bed Based Additive
           Manufacturing Techniques: Process, Nomenclature, Materials, Achievable
           Properties, and its Utilization in the Medical Sector
    • Authors: Leonhard Hitzler; Markus Merkel, Wayne Hall, Andreas Öchsner
      Abstract: Additive manufacturing has multiple advantages over conventional fabrication techniques, such as the geometrical freedom and, to a great extent, the omission of tooling equipment. Hence, futuristic designs and non-standard topology-optimized structures can be fabricated without causing noteworthy extra cost, since the geometrical complexity is, exaggeratedly spoken, for free. The manufacturing time and the amount of required raw material are the key criteria, which determine the expenses. What at first glance appears as an engineer's dream, introduces its complexity in the description of the material's characteristics and their volatility to the manufacturing conditions. Within this study, the main properties (i.e., surface hardness, tensile, and compression strength, as well as fracture toughness) and their anisotropic and inhomogeneous nature are addressed. Detailed overviews of the progress to date for aluminum, iron, titanium, cobalt, and nickel based raw materials are provided. Furthermore, an overview about the state-of-the-art in the medical sector is included, comprising the areas of utilization and several trail studies.Powder-Bed-Fusion techniques are future orientated manufacturing processes, which allow the fabrication of custom designed components and fully unleash their potential when only low quantities are required. One of the current challenges is the prediction of the material properties, which are anisotropic due to the layer wise generation of the components with numerous tiny weld-tracks.
      PubDate: 2018-02-05T10:21:31.067806-05:
      DOI: 10.1002/adem.201700658
  • Metal Alloys for Fusion-Based Additive Manufacturing
    • Authors: Duyao Zhang; Shoujin Sun, Dong Qiu, Mark A. Gibson, Matthew S. Dargusch, Milan Brandt, Ma Qian, Mark Easton
      Abstract: Metal additive manufacturing (AM) is an innovative manufacturing technique, which builds parts incrementally layer by layer. Thus, metal AM has inherent advantages in part complexity, time, and waste saving. However, due to its complex thermal cycle and rapid solidification during processing, the alloys well suit and commercially used for metal AM today are limited. Therefore, it is important to understand the alloying strategy and current progress with materials performance to consider alloy development for metal AM. This review presents the current range of alloys available for metal AM, including titanium, steel, nickel, aluminum, less common alloys (including Mg alloys, metal matrix composites alloys, and low melting point alloys), and compositionally complex alloys (including bulk metallic glasses and high entropy alloys) with a focus on the relationship between compositions, processing, microstructures, and properties of each alloy system. In addition, some promising alloy systems for metal AM are highlighted. Approaches for designing and optimizing new materials for metal AM have been summarized.Additive manufacturing is characterized by rapid solidification and complex thermal cycles during processing, which means the alloys well suit and commercially used for additive manufacturing are limited. This review presents the current range of alloys available for metal additive manufacturing. More importantly, alloying design strategy and some promising alloy systems for metal additive manufacturing are highlighted.
      PubDate: 2018-02-01T08:15:32.925834-05:
      DOI: 10.1002/adem.201700952
  • Fe–Cu Nanocomposites by High Pressure Consolidation of Powders prepared
           by Electric Explosion of Wires
    • Authors: Marat I. Lerner; Sergey G. Psakhie, Aleksandr S. Lozhkomoev, Aliya F. Sharipova, Alexander V. Pervikov, Irena Gotman, Elazar Y. Gutmanas
      Abstract: In the present paper, preparation of nanocomposite powders of mutually immiscible Fe and Cu metals with different Fe-to-Cu ratios by electric explosion of wires and their processing into bulk materials are reported. Near-fully dense nanocrystalline Fe–Cu specimens with high compressive and bending strengths are obtained by high pressure consolidation/cold sintering of the electrically exploded powders at 3 GPa. Reduction treatment in an H2-flow prior to consolidation results in an intimate contact between the oxide free powder surfaces and in an excellent inter-particle bonding integrity. The Cu-rich composition exhibits an attractive combination of high strength and relatively low electrical resistivity.Production of bimetallic nanoparticles composed of two immiscible metals - Fe and Cu - by electric explosion of wires is reported. Bulk nanocomposites obtained by high pressure consolidation/cold sintering of the Fe–Cu nanopowders exhibit an attractive combination of high strength and low resistivity.
      PubDate: 2018-02-01T08:10:50.963786-05:
      DOI: 10.1002/adem.201701024
  • Strengthening Effect and Texture of Mg–3Li Alloys Strengthened by
           Various Rare-Earth Elements
    • Authors: Lei Bao; Qichi Le, Zhiqiang Zhang
      Abstract: Three Mg–3Li–0.4Zr alloys strengthened by various rare-earth elements (RE: Gd, Nd, and Ce) are prepared and studied to obtain the strengthening effect and texture. The results indicate that Gd exhibits a dramatic strength enhancement with minimum ductility decrease compared with Nd and Ce, which is primarily attributed to the effective pinning effect by the solid dissolved Gd atoms and a great amount of dispersing and homogeneously distributing precipitates with the size from nanometers to decades of nanometers. Moreover, the grain boundary segregated Gd is able to restrain the movement of grain boundaries, which is also the primary strengthening mechanism of Nd and Ce elements. Aging treatment shows improvement on mechanical properties of the three RE-containing alloys, but with little obvious effect. At last, Gd-containing Mg–3Li–0.4Zr alloy has good application potential as a kind of new superlight structural material. Pyramidal slip and tension twinning are the primary mechanisms in the early stage of the extrusion process. Basal slip becomes the primary mechanism accompanied by the transfer of texture from extrusion texture to RE-texture ( parallel to extrusion direction) when the complete dynamic recrystallization is achieved.This work deduces a strengthening mechanism resulting from effective pinning effect by the solid dissolved Gd atoms. The primary deformation mechanism transfers from pyramidal slip and tension twinning to basal slip accompanied by the transfer of texture from extrusion texture to RE-texture. Finally, mechanical properties examination shows the novel Mg–3Li–1Gd–0.4Zr alloy has good application potential as a kind of new superlight structural material.
      PubDate: 2018-01-31T07:20:46.92356-05:0
      DOI: 10.1002/adem.201700491
  • Introducing a ZnO–PTFE (Polymer) Nanocomposite Varistor via the Cold
           Sintering Process
    • Authors: Xuetong Zhao; Jing Guo, Ke Wang, Thomas Herisson De Beauvoir, Bo Li, Clive A. Randall
      Abstract: A ZnO–PTFE nanocomposite is formed from a cold sintering process with volume fractions of PTFE up to 40 vol%. The polymer is distributed along grain boundaries and used to limit current from across adjacent grains, enabling this varistor response, with α ≈ 7 being observed. The nanocomposite structure is verified to have polymer intergranular phase in a thickness range from 2 to 5 nm. The electrical characteristics are made to show nonlinear I–V behavior; the barrier-layer effective permittivity is established through an impedance spectroscopy analysis. The activation energies controlling resistance at the grain boundary is determined to range between 0.2 and 0.76 eV with volume fractions between 0 and 40 vol% PTFE. Under high fields and across a broad temperature ranges, the authors quantified of the non-linear conductions with a variety of voltages, the low field higher temperatures are consistent with a Schottky thermionic emission controlled conduction, and Fowler–Nordheim plots shows the current is transitioned to tunneling controlled. The authors also discuss the possibility of designing new types of nanocomposites with the process indicated here, and also having the possibility of taking advantage of interfacial size effects with thin polymer films between ceramic grains.A ZnO–PTFE (polymer) nanocomposite varistor is introduced from a cold sintering process (at 285 °C), and the varistor-like response is controlled by the homogeneously segregated polymer phase along the grain boundaries on a nanometer length scale 1–10 nm. It provides new design strategies of grain boundary engineering with polymer and ceramic composites.
      PubDate: 2018-01-30T07:55:53.353852-05:
      DOI: 10.1002/adem.201700902
  • Calorimetric Study with Uncertainty Analysis to Investigate the
           Precipitation Kinetics in a Nanostructured Al Composite
    • Authors: Ryan Cohn; Blake Fullenwider, Kaka Ma, Julie M. Schoenung
      Abstract: Nanostructured Al–Zn–Mg–Cu alloy and boron carbide/Al–Zn–Mg–Cu composite powders are fabricated through cryomilling. η'-MgZn2 precipitation in each material is characterized through differential scanning calorimetry. The activation energy of η' precipitation is derived through Kissinger analysis. The addition of boron carbide to nanostructured Al–Zn–Mg–Cu powder increases the onset and peak temperatures of η' precipitation, but do not significantly affect the activation energy. Further analysis of uncertainties in measurement indicates that weighted least squares linear regression is a more reliable method that supplements the use of differential scanning calorimetry as a method for rapid characterization of precipitation in materials.Precipitation kinetics in a nanostructured B4C reinforced Al–Zn–Mg composite powder is investigated for the first time. Two linear regression methods are applied to analyze the data from differential scanning calorimetry.
      PubDate: 2018-01-30T07:55:46.770532-05:
      DOI: 10.1002/adem.201700728
  • Nanoporous Superalloy Membranes: A Review
    • Authors: Joachim Rösler; Christian Voelter
      Abstract: The ability to produce metallic membrane materials with porosity on the nanoscale from Ni-based superalloys, hitherto used exclusively for high temperature applications, has been discovered 15 years ago. The basic principle is to first convert the initial γ/γ′ microstructure, containing isolated γ′-precipitates, into a bi-continuous network where both phases are in themselves continuous and interpenetrate each other. Then, one of the two phases is selectively removed, so that a rigid structure consisting of the remaining phase with pores on the location of the removed phase results. This article reviews the progress made so far. In that time period, a number of ways to fabricate these unique materials have emerged, utilizing 1) single crystals and polycrystals as precursor materials as well as 2) coarsening of coherent and incoherent γ′-precipitates to realize bi-continuity of the microstructure. Consequently, a family of superalloy membranes has emerged with specific microstructures, properties, advantages, and limitations. It is the intention of this article to give an overview on these various manufacturing routes, as well as on resulting microstructures and properties. Finally, possible fields of applications are outlined. It is demonstrated that the particular manufacturing process from a solid to the porous material leads to certain advantages, such as the ability to structure the material in porous and solid areas as required by the application.The ability to produce metallic membrane materials with porosity on the nanoscale from Ni-based superalloys, hitherto used exclusively for high temperature applications, has been discovered 15 years ago. This article reviews the progress made so far, illustrates different processing techniques, leading to a family of superalloy membranes with various microstructures and properties, and outlines possible fields of application.
      PubDate: 2018-01-26T03:41:25.855668-05:
      DOI: 10.1002/adem.201701011
  • Cu Nanospring Films for Advanced Nanothermal Interfaces
    • Authors: Dimitrios A. Antartis; Ryan N. Mott, Debashish Das, David Shaddock, Ioannis Chasiotis
      Abstract: An advanced thermal interface material comprised of dense and orderly arrays of 10-µm high Cu nanosprings with tunable normal and shear compliance, lateral stability due to spring intertwining, and thermal resistance below 1 mm2KW−1 is presented. The Cu nanospring films possess the compliance of soft polymers but up to 100 times higher thermal conductivity than materials with similar elastic modulus. This unique combination of mechanical and thermal properties makes it possible for the first time to populate the large empty space in the materials selection chart of thermal conductivity versus elastic modulus.Advanced thermal interface of dense arrays of 10 µm high Cu nanosprings, with tunable normal and shear compliance and lateral stability due to spring intertwining. The Cu nanospring films have the compliance of soft polymers but 10–100 times higher thermal conductivity. The unique combination of mechanical and thermal properties makes it possible to populate the large empty space in the materials selection chart of thermal conductivity versus elastic modulus.
      PubDate: 2018-01-23T06:45:55.643236-05:
      DOI: 10.1002/adem.201700910
  • Designing Stainless Steel Surfaces with Anti-Pitting Properties Applying
           Laser Ablation and Organofluorine Coatings
    • Authors: Elaine Armelin; Sona Moradi, Savvas G. Hatzikiriakos, Carlos Alemán
      Abstract: Long-lasting and superhydrophobic stainless steel with anti-pitting properties is achieved by modifying conventional AISI 304L through a two-step strategy: 1) application of a femtosecond surface laser ablation treatment to generate micro-nano structures on the surface; and 2) deposition of organofluorine nanometric coating. Samples with two different patterns, namely paraboloid- and cauliflower-like, are approached and investigated by means of contact angle hysteresis, X-ray photoelectron spectroscopy, and electrochemical techniques. Results indicate that the stainless steel surface acquires efficient anticorrosive properties due to the homogenization and refinement of the patterned microstructure into a magnetite rich phase, in combination with the formation of a carbonaceous and sol–gel layer. The adherent semiconducting oxide layer is stable over time in presence of an aggressive chloride environment. The prepared superhydrophobic surfaces prevent the steel substrates from getting wet with water, protecting them from the pitting corrosion caused by the electrolyte intrusion. The corrosion resistance is explained by a mechanism in which, in addition of the silane coating, the air trapped into the micro-nano patterned surfaces plays an important role.Long-lasting and superhydrophobic stainless steel with anti-pitting properties is achieved by modifying AISI 304L through a two-step strategy:1) application of a femtosecond surface laser ablation; and 2) deposition of a nanometric coating. The prepared surfaces prevent the steel substrates from getting wet with water, protecting them from the pitting corrosion caused by the electrolyte intrusion.
      PubDate: 2018-01-22T07:10:48.64583-05:0
      DOI: 10.1002/adem.201700814
  • Multiscale Modeling of Microstructure-Property Relationships of
           Polycrystalline Metals during Thermo-Mechanical Deformation
    • Authors: Marko Knezevic; Irene J. Beyerlein
      Abstract: The plastic deformation of polycrystalline metals is primarily carried by the crystallographic glide of dislocations and growth of deformation twins. According to the thermodynamic theory of slip, dislocation motion is thermally activated, while deformation twinning is an athermal process. Dislocations must overcome barriers in order to move, while twins must relax the stored energy while growing. These concepts define the critical activation stresses on a slip or twin crystallographic system and how they evolve with plastic strain. This article reviews recent advances in the development of a model for the critical activation stresses for thermally activated glide and the expansion of deformation twins, its implementation into polycrystal plasticity models, and several applications for predicting the constitutive response of polycrystalline metals. Calculations are performed for a range of polycrystalline metals differing in microstructural complexity and crystal structure. These examples include face-centered cubic AA6022-T4, IN718, Haynes 25, and pure Cu, body-centered cubic Nb, Ta, Ta-10W, and steel DP590, hexagonal close-packed pure Be, pure Zr, pure Ti, AZ31, Mg4Li, and orthorhombic U. Excellent agreement with experimental measurement are demonstrated in terms of texture, stress–strain response, and geometrical changes in the samples during deformation for all these metals.This article reviews recent advances in the development of a model for the critical activation stresses for thermally activated glide and the expansion of deformation twins, its implementation into meso-scale polycrystal plasticity models, and several applications for predicting the constitutive response of polycrystalline metals at the macro-scale within implicit finite element framework.
      PubDate: 2018-01-19T08:06:41.154591-05:
      DOI: 10.1002/adem.201700956
  • Improvement of the Electrical Conductivity between Electrode and Sheet in
           Spot Welding Process by Direct Laser Interference Patterning
    • Authors: Stefan Heilmann; Christoph Zwahr, Alexander Knape, Jörg Zschetzsche, Andrés Fabián Lasagni, Uwe Füssel
      Abstract: The effort of automotive industry is the increasingly use of aluminum alloys to reduce the weight of the car. Regarding the lifetime of electrodes and the process reliability resistance, spot welding is not applied for joining of aluminum sheets. Instead, more expensive processes must be used, like riveting with supplementary component. This is caused by the electric isolating oxide layer at the sheet surface. This layer normally shows an irregular topography, causing a locale temperature increase and therefore high electrode wear. In this study, a new concept to increase the electrode lifetime and process reliability is reported. Using Direct Laser Interference Patterning, periodic surface patterns are produced at the contact area between the electrode and the sheet for influencing the contact resistance. The resulting topography and morphology are analyzed by confocal microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The electrical resistance between the contact partners copper and aluminum is measured during spot welding tests and contact resistance studies. A reduction up to 50% of the electrical resistance by treating the electrodes or an increase of more than 100 times by treating the sheets can be achieved compared to the untreated references.Direct Laser Interference Patterning (DLIP) with picosecond pulses is used to structure copper electrodes and aluminum sheets used in spot welding process. Using DLIP, it is possible to decrease the contact resistance in spot welding process by 50% leading to lower wear of the welding electrodes. Thus, the lifetime of the welding electrodes increases, which could spare setup time in the construction of car bodies.
      PubDate: 2018-01-19T07:40:34.730946-05:
      DOI: 10.1002/adem.201700755
  • Polysilazane-Type Coatings on Mo–Si–B Alloys: A Thermodynamic
           Assessment of the Phase Composition
    • Authors: Iryna Smokovych; Michael Scheffler
      Abstract: Thermodynamic analysis is conducted to identify the most probable phase composition of a polysilazane-type coating system on Mo–Mo3Si(A15)–Mo5SiB2(T2) alloy. The Free Gibbs Energy of chemical reactions between these constituents and resulting phases are calculated. Silicon nitrides, silicon oxynitrides, and molybdenum silicides have been found in the phase equilibrium between the gas phase and condensed species of the proposed coating system. Silicon oxynitride and silica as components in the coating system are potential candidates for Mo–Si–B alloy oxidation protection in air at high temperatures.This paper combines a theoretical/thermodynamic assessment of the phase formation between MoSiB and a polymer derived ceramic coating, in which a polysilazane is used for coating of Mo–Mo3Si(A15)–Mo5SiB2(T2) alloy. Based on the phase equilibrium of the model systems, the predicted phase composition of the coatings may act as a protecting passivation layer on the surface of Mo–Si–B alloys.
      PubDate: 2018-01-16T05:55:53.775529-05:
      DOI: 10.1002/adem.201700936
  • Latent Heat Thermal Energy Storage Systems with Solid–Liquid Phase
           Change Materials: A Review
    • Authors: Nan Zhang; Yanping Yuan, Xiaoling Cao, Yanxia Du, Zhaoli Zhang, Yewei Gui
      Abstract: This paper provides a review of the solid–liquid phase change materials (PCMs) for latent heat thermal energy storage (LHTES). The commonly used solid–liquid PCMs and their thermal properties are summarized here firstly. Two major drawbacks that seriously limit the application of PCMs in an LHTES system, that is, low thermal conductivity and liquid leakage, are discussed. Various methods for enhancing the thermal conductivity and heat transfer of solid–liquid PCMs are explained. Previous studies regarding form-stable composite PCMs and microencapsulated PCMs are also presented. Furthermore, applications of the solid–liquid PCMs used in LHTES and thermal management systems are introduced and analyzed. Finally, future outlooks and research topics are proposed.This paper provides a review of the solid–liquid phase change materials (PCMs) for latent heat thermal energy storage. The thermal properties and shortcomings of the PCMs are summed up firstly. Then, performance improvements of PCMs are discussed. And the applications used for thermal energy storage and thermal management are analyzed. Finally, the future research hotspots of PCMs are proposed.
      PubDate: 2018-01-15T05:18:58.90993-05:0
      DOI: 10.1002/adem.201700753
  • Porous Titanium Implants: A Review
    • Authors: Krzysztof Pałka; Rafał Pokrowiecki
      Abstract: Titanium and its alloys are commonly used in almost all disciplines of medicine because of their sufficient biocompatibility and meeting of mechanical requirements. However, dense metallic biomaterials represent only an interfacial connection with host tissue, may develop stress shielding which causes ingrowth of the fibrous tissue, and are prone to microbial adhesion and development of biomaterial associated infections. Therefore, development of a new, porous titanium biomaterial is proposed to improve an implant's interconnection with bone, provide better stabilization, and reduce the risk of the loss of the implant. In this review, recent findings in porous titanium biomaterials engineering are discussed, including the structural and strengthening aspects of titanium alloys. The porosity and design of porous structures, as well as the optimization process are also described. An extensive part of this section is dedicated to manufacturing processes. The next section of the review is devoted to osseointegration of porous implants and surface treatment processes, whose purpose are antibacterial activity or local drug delivery. Summarizing the article, some future predictions have been presented.Recent findings in the engineering of porous titanium are discussed in this work, including materials aspects. The porosity and design of porous structures, as well as the optimization process and manufacturing are also described. The next part of the review is devoted to osseointegration of porous implants and surface treatment processes, whose purpose are antibacterial activity or local drug delivery.
      PubDate: 2018-01-15T05:18:35.706614-05:
      DOI: 10.1002/adem.201700648
  • Heterogeneous Strain Distribution and Saturation of Geometrically
           Necessary Dislocations in a Ferritic–Pearlitic Steel during Lubricated
    • Authors: Mathias Linz; Manel Rodríguez Ripoll, Christoph Pauly, Johannes Bernardi, Andreas Steiger-Thirsfeld, Friedrich Franek, Frank Mücklich, Carsten Gachot
      Abstract: The microstructural evolution of ferritic–pearlitic steel is studied during unidirectional sliding under boundary lubrication using a ball-on-flat configuration. Dislocation activity as a function of distance to surface is determined using orientation gradients by electron backscatter diffraction in logarithmic intervals up to one million of sliding cycles. The orientation gradient results show the formation of geometrically necessary dislocations and low-angle grain boundaries, followed by a consolidation of those grain boundaries as nanocrystalline grains. The density of geometrically necessary dislocations and low-angle grain boundaries is observed to reach a steady state after around 100 000 cycles. Plastic strain is not homogeneously distributed within both material phases, that is, ferrite and pearlite. Most of the plastic deformation is carried by the ferritic phase. The heterogeneous strain distribution between the ferritic and the pearlitic phase observed in the electron backscatter diffraction measurements is attributed to stress incompatibilities at the grain boundaries. Dislocation pile-up at the ferritic–pearlitic interface is observed at high resolution using transmission electron microscopy and transmission Kikuchi diffraction.The microstructural evolution in sliding contacts is an important aspect in tribology. In this research study, the microstructural changes in a ferritic/pearlitic steel are analyzed with high resolution techniques such as EBSD in a boundary lubricated contact up to 106 cycles. The plastic strain is not homogeneously distributed between ferrite and pearlite. Ferrite carries most of plastic strains.
      PubDate: 2018-01-15T05:18:26.881085-05:
      DOI: 10.1002/adem.201700810
  • Oxidation Behavior between 700 and 1300 °C of Refractory TiZrNbHfTa
           High-Entropy Alloys Containing Aluminum
    • Authors: Chia-Hsiu Chang; Michael S. Titus, Jien-Wei Yeh
      Abstract: Refractory alloys without Cr, Al, and Si additions exhibit very poor high temperature oxidation resistance and thus significantly limit their applications. With an aim to improve the poor oxidation resistance of strong and ductile refractory TiZrNbHfTa high-entropy alloys (HEAs), this study investigates the effect of Al additions on the oxidation behavior and mechanisms for Al0-1TiZrNbHfTa HEAs. Higher Al content renders the alloy more resistant to oxidation. The AlTiZrNbHfTa alloy exhibits a mass gain twice of that of conventional Ni-based alloys at 1100 °C for 1 h, but much less than Nb refractory alloys because an Al-containing oxide on the surface layer provides a partial barrier against oxidation between 700 and 1100 °C. But, at 1300 °C the Al-containing alloys exhibit poor oxidation resistance because the less dense oxide layers provide oxygen with an effective diffusional channel and enable oxygen to penetrate the substrate more easily.This study investigates the effect of Al additions on the oxidation behavior and mechanisms for strong and ductile Al0-1TiZrNbHfTa HEAs. Higher Al content provides the alloy more resistance to oxidation and pesting. The authors speculate that a partial barrier against oxidation is established between 700 and 900 °C; however, at 1300 °C the Al-containing alloys still exhibit poor oxidation resistance.
      PubDate: 2018-01-15T05:18:11.691154-05:
      DOI: 10.1002/adem.201700948
  • Grain Size Depending Dwell-Fatigue Crack Growth in Inconel 718
    • Authors: Jonas Saarimäki; Mattias Lundberg, Johan J. Moverare
      Abstract: Inconel 718 is a commonly used superalloy for turbine discs in the gas turbine industry. Turbine discs are normally subjected to dwell-fatigue as a result of long constant load cycles. Dwell-times have been shown to give rise to increased crack propagation rates in superalloys at elevated temperatures. Dwell-time crack propagation behavior in Inconel 718 has been tested at 550 °C using Kb test samples with 2160 s dwell-times at maximum load and “pure fatigue” tests. The dwell-time effect has been studied for differently processed Inconel 718, that is, fine grained bar, grain enlarged bar, and cast material. This has been done in order to investigate the effect of grain size on crack propagation. Microstructure characterization is conducted using scanning electron microscopy techniques such as electron channeling contrast imaging and electron backscatter diffraction. Time dependent crack propagation rates are strongly affected by grain size. Propagation rates increase with decreasing grain size, whereas crack tip blunting increased with increasing grain size.Dwell-fatigue testing has been conducted on Inconel 718 with three different grain sizes, ≈20 μm, ≈200 μm, and>700 μm. Time dependent crack propagation rates are strongly affected by grain size. Propagation rates increase with decreasing grain size, whereas crack tip blunting increases with increasing grain size.
      PubDate: 2018-01-15T05:18:01.940575-05:
      DOI: 10.1002/adem.201700930
  • On the Mechanical Properties of Aluminum Matrix Syntactic Foams
    • Authors: Imre Norbert Orbulov; Attila Szlancsik
      Abstract: Metal matrix syntactic foams (MMSFs, often referred as composite metal foams (CMFs)) are lightweight materials with high specific strength. MMSFs are on the borderline between metal matrix composites and metal foams. On one hand MMSFs are composites, because they are filled by hollow particles and the particles may add strength to the material. On the other hand, they are foams, because the hollow particles ensure porosity to the material. Among metallic foams, MMSFs exhibit outstanding specific mechanical properties due to the hollow inclusions that are typically made from ceramics or high strength alloys, therefore they can be applied as structural materials. The goal of this paper is to summarize the available data on the mechanical properties of MMSFs with aluminum matrix in order to give a strong support to the design engineers. Since the foams are most frequently loaded in compression, the main part of this paper is organized around the available standard related to the compressive properties of porous materials and metallic foams. The quasi-static results are complemented by properties measured at higher strain rates. Besides this, some insight into the basic fatigue properties as well as into the toughness of MMSFs is also provided.The aim of the manuscript is to summarize the available literature data on the mechanical properties of metal matrix syntactic foams, also called composite metal foams. As the most important mechanical property of the foams is the compressive strength, the figure represents the data survey on this property, highlighting the limits, and relationships to the relative densities.
      PubDate: 2018-01-11T12:42:28.433001-05:
      DOI: 10.1002/adem.201700980
  • Transformation Pathway upon Heating of Ti–Fe Alloys Deformed by
           High-Pressure Torsion
    • Authors: Mario J. Kriegel; Askar Kilmametov, Martin Rudolph, Boris B. Straumal, Alena S. Gornakova, Hartmut Stöcker, Yulia Ivanisenko, Olga Fabrichnaya, Horst Hahn, David Rafaja
      Abstract: The current work presents the results of a study of the thermal stability of metastable ω-Ti(Fe) produced by a high-pressure torsion process and describes the phase transformations of ω-Ti(Fe) upon heating. The titanium alloys under study contain between 1 and 7 wt% of iron, the phase transitions are investigated using a combination of in situ high-temperature X-ray diffraction and differential scanning calorimetry. The high-temperature X-ray diffraction reveals the phase sequence ω  α'  α + β  β upon heating. The differential scanning calorimetry shows that the first phase transformation is exothermal and that the temperature of this phase transition is independent of the iron concentration within the composition range under study. Subsequent phase transitions are endothermal and the respective transition temperatures depend on the iron concentration. The differences between the phase stabilities conclude from the phase diagram and the phase stabilities observe experimentally are explained by the partial coherence of the α/α′-Ti and β-Ti grains.This article presents a study of the thermal stability of metastable ω-Ti(Fe) produced by a high-pressure torsion process. The high-temperature X-ray diffraction reveals the phase sequence ω  α'  α + β  β upon heating. The differences between the phase stabilities concluded from the phase diagram and the phase stabilities observed experimentally are explained by the partial coherence of the α/α′-Ti and β-Ti grains.
      PubDate: 2018-01-05T07:57:55.426204-05:
      DOI: 10.1002/adem.201700933
  • Solid State Porous Metal Production: A Review of the Capabilities,
           Characteristics, and Challenges
    • Authors: Mark A. Atwater; Laura N. Guevara, Kris A. Darling, Mark A. Tschopp
      Abstract: Porous metals have been under development for nearly a century, but commercial adoption remains limited. This development has followed two primary routes: liquid state or solid state processing. Liquid state foaming introduces porosity to a liquid or semi-solid metal, and solid state foaming introduces porosity to a metal, which is fully solid. Either method may create pores by internal gas pressure or introducing metal around a template directly control porosity. Process optimization and commercial output has been primarily related to liquid state methods, as solid state processing is often more complex, diverse, and with lower throughput. Solid state methods, however, are often more versatile and offer greater control of pore characteristics. Ongoing advancements in solid state foaming have allowed for a wide array of metals and alloys to be made porous and the three-dimensional structure to be precisely tailored. In general, solid state processing remains limited to niche applications, often with modest dimensions (cm scale). “Traditional” solid state processes are being further refined and extended, and continuing developments to reduce cost, increase output, and control pore characteristics are likely to produce important advancements in coming years. The extensive variability of pore quantity and morphology makes solid state processes suitable, and often preferable, for an assortment of functional and structural applications, with electrodes and biomedical devices being among the most popular in current research. Various techniques for introducing porosity, the way these methods are applied, important considerations, typical outcomes, and current applications are reviewed.Porous metals have been studied for decades, but production challenges have limited widespread adoption. These are being addressed in an increasing number of publications, especially on solid state methods. Advancements, capabilities, and applications of these methods and materials are reviewed.
      PubDate: 2018-01-04T07:11:01.426069-05:
      DOI: 10.1002/adem.201700766
  • Impact Toughness of Ultrafine-Grained Commercially Pure Titanium for
           Medical Application
    • Authors: Alexander Vadimovich Polyakov; Irina Petrovna Semenova, Elena Vladimirovna Bobruk, Seung Mi Baek, Hyoung Seop Kim, Ruslan Zufarovich Valiev
      Abstract: This study aims at achieving the best combination of strength, ductility, and impact toughness in ultrafine-grained (UFG) Ti Grade 4 produced by equal-channel angular pressing via Conform scheme (ECAP-C) with subsequent cold drawing. UFG structures with various parameters (e.g., size and shape of grains, dislocation density, conditions of boundaries) are formed by varying the treatment procedures (deformation temperature and speed at drawing, annealing temperature). The tensile and impact toughness tests were performed on samples with a V-shaped notch and different structures of commercially pure Ti Grade 4 in the coarse-grained and UFG states. The results demonstrated that grain refinement, higher dislocation density, and their elongated shape were obtained as a result of drawing at 200 °С, which led to a decrease in both the uniform elongation at tension and the impact toughness of Ti Grade 4. Short-term annealing at 400–450 °C could improve the impact toughness of UFG Ti with a non-significant decrease in strength. This short-term annealing contributes to the dislocation density decrease without considerable grain growth as a result of the recovery and redistribution of dislocations. The dependence of impact toughness on the strain hardening ability of UFG Ti was discussed.This study is focused on possibility of achieving the high impact toughness in UFG Ti rods processed by ECAP-Conform with subsequent drawing. It is demonstrated that the annealing at 425–450 °C for 30 min can improve the impact toughness from 85 to 130 kJ m–2 of UFG Ti with a non-significant decrease in tensile strength.
      PubDate: 2018-01-04T07:10:39.521437-05:
      DOI: 10.1002/adem.201700863
  • The Hydride Precipitation Mechanisms in the Hydrogenated Weld Zone of
           Ti–0.3Mo–0.8Ni Alloy Argon-Arc Welded Joints
    • Authors: Quan-Ming Liu; Zhao-Hui Zhang, Shi-Feng Liu, Hai-Ying Yang
      Abstract: A review of the microstructural evolution and phase transformation in the hydrogenated weld zone of Ti–0.3Mo–0.8Ni alloy argon-arc welded joints has been considered. The role of crystallographic, microstructural, and precipitation mechanisms on the defect-free properties of the hydrogenated weld zone has been analyzed, and hydride phase formations have been revealed by the influence of hydrogen on the microstructural characteristics of the weld zone. The results show face-centered cubic (FCC) δ and face-centered tetragonal (FCT) γ hydride phase formations are found in the hydrogenated 0.21 wt% H weld zone. Large lamellar, slender plate δ and long needle γ hydrides can only precipitate from the alpha lamellae, and not from the transformed beta phase due to the high hydrogen solubility found in the beta phase. Formation of the δ and γ hydrides are the result of αH phase separation reaction: αH  α (H lean region) + δ (H rich region) and αH  γ (H rich region), respectively. The precipitation mechanisms and characteristics of the δ and γ hydrides formed in alpha phase are discussed in detail. Dislocation multiplication around the hydrides is promoted effectively by hydrogen addition, the fact that the quantity of dislocations around the δ hydride increased obviously compared to γ hydride indicated the αH  δ phase transformation result in a greater volume expansion rate.Based on the strong affinity of titanium alloys and hydrogen, the hydrogenated titanium alloys welded joints with a series of hydrogen contents as a high incidence area of hydrogen embrittlement have been used for the study of hydrides precipitation types, characteristics, and mechanisms in details.
      PubDate: 2018-01-04T07:05:53.144324-05:
      DOI: 10.1002/adem.201700679
  • Solid-State Supercapacitor Fabricated in a Single Woven Textile Layer for
           E-Textiles Applications
    • Authors: Sheng Yong; John Owen, Stephen Beeby
      Abstract: This paper presents for the first time a solid-state supercapacitor fabricated in just a single woven cotton textile layer. The controlled spray coating process enables the depth of the activated carbon electrodes to be precisely controlled from both sides of the textile. This leaves an uncoated region within the cotton textile layer that acts as the separator and also minimizes the effect of the added functional materials on the feel of the textile. The cotton electrode is then vacuum impregnated with the gel electrolyte to ensure good coverage of the electrode by the electrolyte. After drying, the single textile layer supercapacitor has been fully characterized and demonstrates good capacitance and excellent electrochemical cycling stability even after mechanically straining the textile.In this work, a single layer solid state cotton textile supercapacitor is fabricated by a combination of and inexpensive carbon solution, spray coating, and vacuum impregnation process. The dried device has been characterized and demonstrates good capacitance and excellent electrochemical cycling stability even after mechanically straining the textile.
      PubDate: 2018-01-04T07:05:35.795526-05:
      DOI: 10.1002/adem.201700860
  • Recent Advances on 3D Printing Technique for Thermal-Related Applications
    • Authors: Nam Nguyen; Jin Gyu Park, Songlin Zhang, Richard Liang
      Abstract: Advances in ink formulation and printing techniques make producing material systems with new and versatile characteristics and functionalities possible. Additive manufacturing or 3D printing enables fabricating complex structures at a faster production rate using different types of materials for various applications. Recently, 3D printing methods are being studied for thermal-related applications. In this paper, the authors review recent progress of materials and printing techniques for thermal application devices using composite materials.The authors summarize recent progress of materials and printing techniques for thermal-related application devices such as heat sink, heater, or thermal interface materials. Current challenges and opportunity related to the printing thermal-related devices are also discussed in the paper.
      PubDate: 2018-01-03T11:06:16.821007-05:
      DOI: 10.1002/adem.201700876
  • Transparency in Structural Glass Systems Via Mechanical, Adhesive, and
           Laminated Connections - Existing Research and Developments
    • Authors: Chiara Bedon; Manuel Santarsiero
      Abstract: The consistent architectural transparency demand in buildings is highly promoting the structural use of glass, in combination or to replace load-bearing components made of traditional constructional materials. Despite its huge application in facades, roofs, envelopes, frame components, however, glass still represents a rather innovative and not well-known material, requiring specific design conceptsm and further extended studies, toward the fulfillme nt of safe design requirements. A key role in glass systems and assemblies involving multiple components is given to connections. Major issues in their design, consequently, arise from restraining single glazing elements, as well as from ensuring their mechanical interaction with other constructional systems, as a part of full 3D buildings, including several materials, and various loading/boundary conditions. In this paper, an overview of typical connection types in use for glass systems is presented, with special consideration for mechanical, adhesive, and laminated adhesive connections, giving evidence of their typical applications, evolution, current design issues. Existing research and major projects are also discussed, both at the material/component level as well as at the assembly level.Structural glass is largely used in buildings, in combination or to replace load-bearing components made of traditional constructional materials. However, glass still represents a rather innovative and not well-known material, requiring specific design concepts and studies, especially in terms of connections. The paper presents an overview of typical connections in use for glazing systems, with special consideration for mechanical, adhesive and laminated adhesive solutions, giving evidence of typical applications, evolution, design issues.
      PubDate: 2018-01-03T06:48:17.962236-05:
      DOI: 10.1002/adem.201700815
  • Bioinspired Nacre-Like Ceramic with Nickel Inclusions Fabricated by
           Electroless Plating and Spark Plasma Sintering
    • Authors: Zhe Xu; Jiacheng Huang, Cheng Zhang, Soheil Daryadel, Ali Behroozfar, Brandon McWilliams, Benjamin Boesl, Arvind Agarwal, Majid Minary-Jolandan
      Abstract: Hybrid composites of layered brittle-ductile constituents assembled in a brick-and-mortar architecture are promising for applications requiring high strength and toughness. Mostly, polymer mortars have been considered as the ductile layer in brick-and-mortar composites. However, low stiffness of polymers does not efficiently transfer the shear between hard ceramic bricks. Theoretical models point to metals as a more efficient mortar layer. However, infiltration of metals into ceramic scaffold is non-trivial, given the low wetting between metals and ceramics. The authors report on an alternative approach to fabricate brick-and-mortar ceramic-metal composites by using electroless plating of nickel (Ni) on alumina micro-platelets, in which Ni-coated micro-platelets are subsequently aligned by a magnetic field, taking advantage of ferromagnetic properties of Ni. The assembled Ni-coated ceramic scaffold is then sintered using spark plasma sintering (SPS) to locally create Ni mortar layers between ceramic platelets, as well as to sinter the ceramic micro-platelets. The authors report on materials and mechanical properties of the fabricated composite. The results show that this approach is promising toward development of bioinspired ceramic-metal composites.Bioinspired ceramic-metal composite is fabricated by electroless-plating of Nickel (metal) on ceramic (aluminum oxide) microplates. The metal-coated platelets are subsequently aligned by magnetic field and sintered by spark plasma sintering process. The composite shows desirable crack-deflection properties.
      PubDate: 2018-01-02T04:20:34.141423-05:
      DOI: 10.1002/adem.201700782
  • Novel Antibacterial and Bioactive Silicate Glass Nanoparticles for
           Biomedical Applications
    • Authors: Ana Catarina Vale; Ana Luísa Carvalho, Ana Margarida Barbosa, Egídio Torrado, João F. Mano, Natália M. Alves
      Abstract: In this work, the authors propose a new quick sol–gel procedure for bioglass nanoparticles production containing 10% mol of silver (AgBGs). These new AgBGs are characterized by Zeta potential analysis, scanning electron microscopy with X-ray microanalysis (SEM/EDS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and microbiological tests to confirm their bioactive and antibacterial properties. SEM shows that the average particle size is less than 200 nm and EDS confirms the successful incorporation of Ag2O in the bioglass matrix. XRD confirms the amorphous nature of the AgBGs and, after SBF immersion, reveals their bioactive behavior with the presence of crystalline phase of calcium silicate and phosphorus oxide, which are also detected by FTIR analysis. FTIR also confirms the formation of typical siloxane bonds resulting from the condensation of silicate glass. Lastly, it is found that the developed AgBGs has an antibacterial effect against two different types of bacteria, thus demonstrating their ability to reduce the bacterial infection within 16 h.Bioglass nanoparticles with silver content are of interest, since they provide the combination of important properties. As the image shows, this work presents the production and characterization of new silver doped nanoparticles, confirming their bioactive and antibacterial properties, which are crucial for several biomedical applications.
      PubDate: 2017-12-27T02:25:30.534797-05:
      DOI: 10.1002/adem.201700855
  • The Occurrence of Ideal Plastic State in CP Titanium Processed by Twist
    • Authors: Aleksey Reshetov; Roman Kulagin, Alexander Korshunov, Yan Beygelzimer
      Abstract: This paper deals with the analysis of strength and plastic characteristics of commercially pure (CP) titanium as a function of equivalent plastic strain accumulated during Twist Extrusion (TE) process. It is shown experimentally that multipass TE leads to the saturation of the following characteristics of the material: yield stress, reduction in area, elongation to failure, and uniform elongation. This fact indicates the occurrence of an ideal plastic state in the processed material. The threshold value of accumulated plastic strain for ideal plastic behavior of CP titanium during TE is defined. The strain state and mechanical properties of CP titanium billets processed by TE are studied. An explanation for the hardening on the axis of a billet during TE is offered. The analysis of deformation modes on the billet axis during TE and High Pressure Torsion is carried out. It is shown that the differences in strain state on the axis are caused by the difference in symmetry of these processes.It is shown experimentally that multipass TE leads to the saturation of mechanical properties in the billet. This fact indicates the occurrence of an ideal plastic state. An explanation for the hardening central zone of the billet during TE is offered.
      PubDate: 2017-12-21T05:06:20.647846-05:
      DOI: 10.1002/adem.201700899
  • Additive Manufacturing of Titanium Alloys by Electron Beam Melting: A
    • Authors: Lai-Chang Zhang; Yujing Liu, Shujun Li, Yulin Hao
      Abstract: Electron beam melting (EBM), as one of metal additive manufacturing technologies, is considered to be an innovative industrial production technology. Based on the layer-wise manufacturing technique, as-produced parts can be fabricated on a powder bed using the 3D computational design method. Because the melting process takes place in a vacuum environment, EBM technology can produce parts with higher densities compared to selective laser melting (SLM), particularly when titanium alloy is used. The ability to produce higher quality parts using EBM technology is making EBM more competitive. After briefly introducing the EBM process and the processing factors involved, this paper reviews recent progress in the processing, microstructure, and properties of titanium alloys and their composites manufactured by EBM. The paper describes significant positive progress in EBM of all types of titanium in terms of solid bulk and porous structures including Ti–6Al–4V and Ti–24Nb–4Zr–8Sn, with a focus on manufacturing using EBM and the resultant unique microstructure and service properties (mechanical properties, fatigue behaviors, and corrosion resistance properties) of EBM-produced titanium alloys.Electron beam melting (EBM), a metal additive manufacturing technology, has the ability to produce high quality metal parts. This paper reviews recent progress in all types of titanium alloys in terms of solid and porous structures, with a focus on the microstructure and service properties (mechanical properties, fatigue behaviors, and corrosion resistance properties) of EBM-produced titanium alloys.
      PubDate: 2017-12-19T04:26:43.181635-05:
      DOI: 10.1002/adem.201700842
  • Finite Element Analysis as a Method to Study Molluscan Shell Mechanics
    • Authors: Robert Lemanis; Igor Zlotnikov
      Abstract: The clade Mollusca is a highly diverse and disparate group of terrestrial and aquatic invertebrates, the taxon containing over 100 000 known species including some of the most intelligent invertebrate animals. Their shells are exemplar systems in the study of biomechanics, biomineralization, and biomimetics. Research into understanding the superior biomechanical properties of the shell and how these properties relate to the animals ecology have required a diverse range of methods at multiple length scales; one particularly powerful method is finite element analysis. Finite element analysis is a robust engineering method that has a long-standing history in biomechanical research. This review summarizes the application of finite element analysis in the study of both the mechanical properties of different molluscan shell ultrastructures as well as macro-scale modeling of the shell. From the calculation of elastic constants to the origins of the strength of nacre and the relationship between shell folding and ecology, this article provides a window into how finite element analysis can further our understanding of mechanics and functional morphology.Decades of research have gone into the study of the molluscan shell using a variety of methods. Here, the authors review how one particular method, finite element analysis, has been used to further our understanding of the mechanical properties and functional morphology of the shell at both the ultrastructural and macro-structural levels.
      PubDate: 2017-12-18T07:42:13.035821-05:
      DOI: 10.1002/adem.201700939
  • Combined Microwave and Laser Heating for Glazing of 8Y–ZrO2 and
    • Authors: Christian Richter; Sebastian Lehmann, Jens Böckler, Monika Willert-Porada, Andreas Rosin
      PubDate: 2017-12-14T09:15:44.920659-05:
      DOI: 10.1002/adem.201700912
  • Modulation of Agglomeration of Vertical Porous Silicon Nanowires and the
           Effect on Gas-Sensing Response
    • Authors: Yuxiang Qin; Yunqing Jiang, Liming Zhao
      Abstract: Porous silicon nanowires (PSiNWs) array is a promising material for development of integrated gas sensors operating at room temperature. This work reports the fabrication of PSiNWs assembly with different structural features and its effect on gas-sensing performance. Bundling and well separating PSiNWs arrays are fabricated by MACE method, respectively, based on the effective modulation of surface wettability of the initial Si substrate. The HF pretreatment creates a hydrophobic surface favorable for deposition of irregular Ag nanoflakes and then for the formation of bundling PSiNWs array. In contrast, the PSiNWs with well lateral separation are formed based on the predeposited uniform Ag nanoparticles on a hydrophilic Si surface. The PSiNWs array featured by tip-clusters is proved to be highly effective in achieving highly sensitive and rapid response to NO2 gas at room temperature. Satisfying dynamic characteristic and selectivity are meanwhile observed for the bundling array. The formation of the bundling or separating of PSiNWs is discussed in terms of the force balance of individual nanowire, which is further correlated with non-uniform distribution of Ag nanoclusters caused by H-termination. Meanwhile, high sensing performance of bundling nanowires is analyzed based on the structural promotion of the unique configuration of tip-cluster to sensing response.Bundling and well separating porous silicon nanowires (PSiNWs) arrays are, respectively, fabricated based on the effective modulation of surface wettability of initial Si substrate. The PSiNWs array featured by tip-clusters is demonstrated as a highly effective configuration for gas-sensing application; highly sensitive and rapid response to NO2 gas is achieved at room temperature.
      PubDate: 2017-12-14T09:06:26.834812-05:
      DOI: 10.1002/adem.201700893
  • Preparations, Characteristics and Applications of the Functional Liquid
           Metal Materials
    • Authors: Qian Wang; Yang Yu, Jing Liu
      Abstract: As new generation functional materials, the recently emerging low-melting liquid metals have displayed many unconventional properties superior to traditional materials. Various methods, such as alloying, oxidizing, adding metals, or non-metallic materials and so on, have been developed to prepare desirable functional materials based on the gallium or more other metals. These methods could not only change the form of the materials, but also endow the original liquid metals with rather diversified performances, which have further expanded the application range of the low-melting liquid metals to meet various needs. This article aims to review and summarize on the fabrication methods, characteristics, and applications of the functional liquid metal materials. Furthermore, the future outlook in this field, including challenges, routes, and related efforts, has also been illustrated and interpreted.The low melting point liquid metals have recently been disclosed with many outstanding unconventional properties superior to traditional materials. This article comprehensively reviews and summarizes the most typical fabrication methods, unique characteristics, and important applications of such functional materials. The future outlook in this field, including challenges, developing routes, and related efforts has also been illustrated and interpreted.
      PubDate: 2017-12-13T06:03:22.20866-05:0
      DOI: 10.1002/adem.201700781
  • Composition Dependence on the Evolution of Nanoeutectic in CoCrFeNiNbx
           (0.45 ≤ x ≤ 0.65) High Entropy Alloys
    • Authors: Barnasree Chanda; Jayanta Das
      Abstract: The effect of Nb addition in arc-melted CoCrFeNiNbx (0.45 ≤ x ≤ 0.65) high entropy alloys (HEAs) on the phase evolution, stability, refinement of the microstructure, and mechanical properties are investigated. Minor fluctuation of Nb modifies the microstructure from hypoeutectic (x = 0.45) to eutectic (x = 0.5) and hypereutectic (x = 0.55) containing 134–200 nm thin nano-lamellar FCC γ-Ni and HCP Fe2Nb-type Laves phases. The nano-eutectic CoCrFeNiNb0.5 HEA shows high yield strength (2060 ± 5 MPa) and strain hardening up to 2200 ± 10 MPa with 17.0 ± 0.5% compressive plasticity. Transmission electron microscopic studies of partially deformed specimen has been revealed that the activity of dislocations is present in the eutectic FCC/Laves lamellae and at their interface. The stability of the phases in CoCrFeNiNbx and other eutectic HEAs as reported in the literature, has been assessed by estimating mixing entropy (ΔSmix), mixing enthalpy (ΔHmix), atomic size differences (δ), valence electron concentration, Pauling electronegativity (ΔχP), and Allen electronegativity (ΔχA) to predict the evolution and coexistence of eutectic phases.The microstructure of CoCrFeNiNbx (0.45 ≤ x ≤ 0.65) high entropy alloys contain proeutectic dendrites along with nanolamellar γ-Ni and Laves phases, which show high yield strength of 2060 MPa and large plasticity of 17% due to the movement of dislocations. The stability of the phases has been assessed using thermodynamic parameter, atomic size parameter, valance electron concentration, and electronegativity parameters.
      PubDate: 2017-12-13T05:36:18.715984-05:
      DOI: 10.1002/adem.201700908
  • Utilizing Low-Cost Eggshell Particles to Enhance the Mechanical Response
           of Mg–2.5Zn Magnesium Alloy Matrix
    • Authors: Gururaj Parande; Vyasaraj Manakari, Sripathi Dev Sharma Kopparthy, Manoj Gupta
      Abstract: The search for lightweight high-performance materials is growing exponentially primarily due to ever-increasing stricter environmental regulations and stringent service conditions. To cater to these requirements, the use of low-cost reinforcements has been explored in the Mg matrix to develop Economically Conscious Magnesium (ECo–Mg) composites. In this study, eggshell particles (3, 5, and 7 wt%) reinforced Mg–Zn composites are synthesized using blend-press-sinter powder metallurgy technique. The results reveal that the addition of eggshell particles enhances microhardness, thermal stability, damping, and yield strength with an inappreciable change in the density. In particular, Mg2.5Zn7ES composite do not ignite till ≈750 °C. The overall combination of properties exhibited by Mg–Zn–ES composites exceeds many of currently used commercial alloys in the transportation sector. An attempt is made, in this study, to interrelate microstructure and properties and to study the viability of compression and ignition properties with a comparison to commercially used Mg alloys.This work investigates the influence of low-cost reinforcement (eggshell) on the microstructural, mechanical and damping enhancement of Mg–Zn alloy using low-cost synthesis methodology (powder metallurgy technique). Mg–Zn–eggshell composites display superior property enhancement better than most commercially available Mg alloys and are a potential replacement material in several engineering and biomedical applications.
      PubDate: 2017-12-13T04:56:38.58965-05:0
      DOI: 10.1002/adem.201700919
  • Additive Manufacturing of Advanced Multi-Component Alloys: Bulk Metallic
           Glasses and High Entropy Alloys
    • Authors: Xiaopeng Li
      Abstract: Bulk metallic glasses (BMGs) and high entropy alloys (HEAs) are both important multi-component alloys with novel microstructures and unique properties, which make them promising for applications in many industries. However, certain hindrances have been identified in the fabrication of BMGs and HEAs by conventional techniques due to the intrinsic requirements of BMGs and HEAs. With the advent of metal additive manufacturing, new opportunities have been perceived to fabricate geometrically complex BMGs and HEAs with tailorable microstructure theoretically at any site within the specimen, which are not achievable using conventional fabrication techniques. After providing some background and introducing the conventional fabrication techniques for BMGs and HEAs, this review will focus on the current status, development, and challenges in metal additive manufacturing of BMGs and HEAs including different additive manufacturing techniques being used, microstructure design and evolution, as well as properties of the fabricated BMGs and HEAs. A future outlook of metal additive manufacturing of BMGs and HEAs will also be provided at the end.Additive manufacturing has become a promising alternative for the fabrication of advanced multi-component alloys such as bulk metallic glasses (BMGs) and high entropy alloys (HEAs). Due to the intrinsic layer-wise fabrication process of additive manufacturing, more complex and large scale BMGs and HEAs components with controllable local microstructure and properties can be achieved.
      PubDate: 2017-12-12T08:28:01.13502-05:0
      DOI: 10.1002/adem.201700874
  • Super-High Strength Mg–7.5Al–0.8Zn Alloy Prepared by Rapidly
           Solidified Powder Metallurgy and Low Temperature Extrusion
    • Authors: Jian Zhu; Junxiu Liu, Yi Wang, Kuang Lu, Jinbin Chen, Zikui Liu, Xidong Hui
      Abstract: In this work, Mg–7.5Al–0.8Zn alloy with super-high tensile strength are fabricated by rapidly solidified powder metallurgy (RS/PM) and low temperature extrusion technology. By reducing extrusion temperature from 340 to 170 °C, the α-Mg grains are significantly refined and numerous nanoscale β-Mg17Al12 particles are obtained. The RS/PM alloy extruded at 170 °C possesses the lowest grain size of ≈550 nm. The nanoscale β-phase particles stimulate the nucleation of dynamically recrystallized (DRXed) grains and restrain the growth of DRXed grains. The RS/PM alloy extruded at 170 °C exhibits mechanical properties with a tensile yield strength of 448 MPa, an ultimate tensile strength of 480 Mpa, and a microhardness of 137 HV. These excellent mechanical properties result from low temperature extrusion are mainly attributed to the ultra-fine DRXed grains and the high-density dislocations and subgrains.The effects of extrusion temperatures are investigated on the microstructures and mechanical properties of RS/PM Mg–7.5Al–0.8Zn alloys. The mechanical properties of RS/PM alloys are remarkably improved by reducing extrusion temperatures from 340 to 170 °C.
      PubDate: 2017-12-12T08:26:40.746323-05:
      DOI: 10.1002/adem.201700712
  • Controlled Friction Behaviors of Porous Copper/Graphite Storing Ionic
           Liquid through Electrical Stimulation
    • Authors: Guoliang Zhang; Guoxin Xie, Jie Wang, Lina Si, Dan Guo, Shizhu Wen, Fan Yang
      Abstract: Porous copper/graphite composites storing stimuli-responsive lubricant can be used to fabricate a new kind of electrical contact friction materials. However, the synergetic lubricating effect of solid and liquid lubricants incorporated into the copper matrix is rarely discussed. In this work, neat copper and its composites storing ionic liquids (ILs) have been successfully prepared via a template-free strategy. The effect of frictional, electrical, and electro-frictional coupling stimulation on the tribological behavior of the copper filled with graphite has been investigated using ball-on-disk friction tests. Results show that a high voltage may accelerate the release of the ILs stored in the composite to the friction interface, thereby resulting in a low coefficient of friction (COF) (ca. 0.14) at the voltage of 0.5 V, which is superior to those of the pure copper without applying voltage. The COF is more stable in copper/graphite composite storing ILs (SI) than in copper-SI. Therefore, the graphite efficiently protects the surface of the sample from wear and electrochemical corrosion.The ionic liquids (ILs) stored in the pores of the copper matrix respond to the frictional, electrical, and electro-frictional coupling stimulation has been investigated using ball-on-disk friction tests under external electric fields. A proper voltage may accelerate the release of the ILs to the friction interface, thereby resulting in a low coefficient of friction.
      PubDate: 2017-12-11T07:26:26.768903-05:
      DOI: 10.1002/adem.201700866
  • Spin Valve Effect of 2D-Materials Based Magnetic Junctions
    • Authors: Muhammad Zahir Iqbal; Salma Siddique, Ghulam Hussain
      Abstract: The magnetotransport properties of spin valve structure are highly influenced by the type of intervening layer inserted between the ferromagnetic electrodes. In this scenario, spin filtering effect at the interfaces plays a crucial role in determining the magnetoresistance (MR) of such magnetic structures, which can be enhanced by using a suitable intervening layer. Here, the authors investigate the spin filtering effect of the two-dimensional layers such as hexagonal boron nitride (hBN), graphene (Gr), and Gr-hBN hybrid system for modifying the magnetotransport characteristics of the vertical spin valve architectures (Ni/hBN/Ni, Ni/Gr/Ni, and Ni/Gr-hBN/Ni). Compared to graphene, hBN incorporated magnetic junction reveals higher MR and spin polarizations (P) suggesting better spin filtering at the interfaces. The MR for hBN incorporated junction is calculated to be ≈0.83%, while that of graphene junction it is estimated to be ≈0.16%. Similar contrast is observed in the ‘P’ of ferromagnets (FMs) for the two junctions, that is, ≈6.4% for hBN based magnetic junction and ≈2.8% for graphene device. However, for Gr-hBN device, the signal not only get inverts, but it also suggests efficient spin filtering mechanism at the FM interfaces. Their results can be useful to comprehend the origin of spin filtering and the choice of non-magnetic spacer for magnetotransport characteristics.The authors investigate spin filtering mechanism by incorporating 2D materials in spin valve devices. Comparing to graphene, hBN device reveals pronounced spintronic features suggesting better spin filtering at the interfaces. Furthermore, graphene and hBN incorporated magnetic junctions reveal positive MR, while that for Gr-hBN heterostructure the signal not only becomes negative, but also facilitates efficient spin filtering at the interfaces.
      PubDate: 2017-12-11T07:25:58.015757-05:
      DOI: 10.1002/adem.201700692
  • Enhanced Mechanical Properties of Multilayered Cu with Modulated Grain
           Size Distribution
    • Authors: Bo Zheng; Xixun Shen, Huisheng Jiao, Qunjie Xu, Danhong Cheng
      Abstract: A bulk multilayered copper with nano-sized grains (NG) as hard layer and ultrafine grains (UFG) as soft layer with the thickness ratio of about 10:1 is synthesized by electrodeposition. Microstructural studies by scanning electron microscope (SEM) and transmission electron microscope (TEM) reveal the alternating growth of well-defined layers with either nano-grains or ultrafine-grains. Tensile tests reveal that the layered nanostructured Cu exhibits an enhanced ductility of near 17.5% and high ultimate tensile strength of about 700 MPa. The multilayered Cu exhibits a higher ductility without obvious loss of strength compared to the monolithic nano-grained Cu. The enhanced ductility is primarily attributed to two effects including the increased strain hardening ability and the effective adjustment to the local stress concentration brought by the periodic existence of the UFG layer in the NG matrix.A bulk multilayered Cu with the alternating growth of nano-grained layer and ultrafine grained layer with the thickness ratio of about 10:1 is synthesized by electrodeposition technique. The multilayered Cu exhibits a better combination of high ductility and high strength in comparison with the corresponding monolithic nano-grained and ultrafine-grianed Cu.
      PubDate: 2017-12-08T08:15:47.382134-05:
      DOI: 10.1002/adem.201700849
  • Fabrication of Metallic Fibers with High Melting Point and Poor
           Workability by Unidirectional Solidification
    • Authors: Yuui Yokota; Takayuki Nihei, Kunihiro Tanaka, Koichi Sakairi, Valery Chani, Yuji Ohashi, Shunsuke Kurosawa, Kei Kamada, Akira Yoshikawa
      Abstract: Innovative method acceptable for production of Iridium (Ir) and Ruthenium (Ru) metal fibers with high melting point and poor workability is developed using an alloy-micro-pulling-down (A-μ-PD) method and ceramic crucibles with sufficient mechanical and thermal shock resistance. As-grown (as-solidified) Ir and Ru fibers are approximately 1 mm in diameter and their lengths exceed 15 and 0.3 m, respectively. Both Ir and Ru fibers are composed of number of elongated grains oriented along a growth direction, which is attributable to the unidirectional solidification. The flexibility and oxidation resistance of the Ir fiber grown by the A-μ-PD method is considerably improved as compared to a commercial Ir wire made by wire-drawing process.Innovative method acceptable for production of Iridium and Ruthenium metal fibers with high melting point and poor workability are developed using an alloy-micro-pulling-down (A-μ-PD) method and ceramic crucibles with sufficient mechanical and thermal shock resistance. The Iridium and Ruthenium fibers are composed of number of elongated grains oriented along the growth direction, which is attributable to the unidirectional solidification.
      PubDate: 2017-12-07T08:08:41.149519-05:
      DOI: 10.1002/adem.201700506
  • Effect of Dynamically Recrystallized Grains on Rare Earth Texture in
           Magnesium Alloy Extruded at High Temperature
    • Authors: Rongguang Li; Guangyan Fu, Zeren Xu, Yong Su, Yongsheng Hao
      Abstract: This work investigates texture evolution in an Mg–3Gd–0.2Al alloy during extrusion and after annealing at 500 °C. It shows that the dynamically recrystallized (DRX) grains formed in grain boundaries and twins have different influence on texture evolution. After extrusion, the DRX grains that nucleated at grain boundaries have texture distributing from ED to ED, while these in twins do from ED to ED. After further annealing process, the ED component is strengthened and become the dominating texture component, which results in a strong rare earth (RE) texture. Thus, the RE texture is mainly attributed to the preferential nucleation at grain boundaries during extrusion and the privileged growth of the grains with ED orientation during annealing.A trace of {10–11}–{10–12} double-twin is identified. Orientation of double-twin is close to ED, and ones of DRX grains range from ED to ED. Thus, DRX grains within twins have orientations close to that of twins.
      PubDate: 2017-12-07T08:08:29.621419-05:
      DOI: 10.1002/adem.201700818
  • Effects of Initial δ Phase on Creep Behaviors and Fracture
           Characteristics of a Nickel-Based Superalloy
    • Authors: Y. C. Lin; Liang-Xing Yin, Shun-Cun Luo, Dao-Guang He, Xiao-Bin Peng
      Abstract: Uniaxial creep tensile experiments are performed to study the influences of initial δ phase (Ni3Nb) on the creep features and fracture behaviors of a nickel-based superalloy. Experimental results show that the creep features and fracture behaviors of the researched superalloy are closely relevant to the volume fraction of initial δ phase. The minimum creep rate increases with the increased volume fraction of initial δ phase. The appropriate volume fraction of initial δ phase can improve the creep resistance and plasticity. So, the rupture time and the elongation to fracture initially increase, when the volume fraction of initial δ phase is relatively low, and then decrease with the increase of volume fraction of initial δ phase. Additionally, with the increased initial δ phase, the failure mode changes from a typical intergranular fracture to the mixed fracture pattern of ductile intergranular and cleavage fracture.Effects of initial δ phase (Ni3Nb) on uniaxial creep behavior and fracture characteristics of a nickel-based superalloy are investigated. The appropriate initial δ phase fraction can improve the creep resistance and plasticity. The increased initial δ phase changes the failure mode from a typical intergranular fracture to the ductile intergranular/cleavage mixed fracture.
      PubDate: 2017-12-06T08:45:39.29225-05:0
      DOI: 10.1002/adem.201700820
  • Recent Progress on Piezotronic and Piezo-Phototronic Effects in III-Group
           Nitride Devices and Applications
    • Authors: Chunhua Du; Weiguo Hu, Zhong Lin Wang
      Abstract: Wurtzite-structured III-group nitrides, like GaN, InN, AlN, and their alloys, present both piezoelectric and semiconducting properties under straining owing to the polarization of ions in a crystal with non-central symmetry. The piezoelectric polarization charges are created at the interface when a strain is applied. As a result, a piezoelectric potential (piezopotential) is produced, which is used as a “gate” to tune/control the charge transport behavior across a metal/semiconductor interface or a p-n junction. This is called as piezotronic effect. A series of piezotronic devices and applications have been developed, such as piezotronic nanogenerators (NGs), piezotronic transistors, piezotronic logic devices, piezotronic electromechanical memories, piezotronic enhanced biochemical, and gas sensors and so on. With the flourished development of piezotronic effect, the piezo-phototronic effect, as the three-way coupling of piezoelectric polarization, semiconductor properties, and optical excitation, utilizes the piezopotential to modulate the energy band profile and control the carrier generation, transportation, separation, and/or recombination for improving performances of optoelectronic devices. This paper intends to provide an overview of the rapid progress in the emerging fields of piezotronics and piezo-phototronics, covering from the fundamental principles to devices and applications. This study will provide important insight into the potential applications of GaN based electronic/optoelectronic devices in sensing, active flexible/stretchable electronics/optoelectronics, energy harvesting, human-machine interfacing, biomedical diagnosis/therapy, and prosthetics.Wurtzite-structured III-group nitrides have been widely used for developing the revolutionary multifunctional electronics/optoelectronics based on heterojunction, quantum well and superlattice structures. Due to non-central symmetry of crystal lattice, piezopotential is generated by applying mechanical force/stress to tune/control the carriers' generation, transportation, and/or recombination, which is the core of the piezotronic and piezo-phototronic effects.
      PubDate: 2017-12-06T06:11:17.594249-05:
      DOI: 10.1002/adem.201700760
  • Toward High Strength and High Electrical Conductivity in Super-Aligned
           Carbon Nanotubes Reinforced Copper
    • Authors: Lunqiao Xiong; Kangwei Liu, Jing Shuai, Zecheng Hou, Lin Zhu, Wenzhen Li
      Abstract: The miniaturization of electronic products is drawing higher demand in the strength and conductivity of conductors. This work demonstrates the possibility of substantially increasing the dislocation density in copper to enhance the strength of super-aligned carbon nanotubes (SACNTs) reinforced copper matrix composites (SACNT/Cu) without compromising the electrical conductivity. High strain is introduced into pure copper and SACNT/Cu by accumulative roll-bonding (ARB) process up to 16 cycles at ambient temperature. SACNTs with initial laminated distribution turn out to be dispersed uniformly with maintained directional arrangement inside the copper matrix after ARB, which can then effectively block the motion of dislocations. Therefore, large number of dislocations propagated by large strains can be accumulated without subdivision. The accumulated dislocations will result into strain hardening, which is the major strengthening mechanism in SACNT/Cu after ARB. Furthermore, the contribution of dislocations to resistivity increase is little, thus maintaining high electrical conductivity. As a result, a high tensile strength (505 MPa) combined with a high electrical conductivity (90% IACS) is achieved in large-sized composite sheet.The strength of super-aligned carbon nanotubes (SACNTs) reinforced copper matrix composite is substantially enhanced without compromising the conductivity by increasing the dislocation density in copper. The dispersed distribution of SACNTs can effectively block dislocation motion, thus delaying grain refinement during accumulative roll-bonding process. High strength and high electrical conductivity copper matrix composite can, therefore, be mass-produced.
      PubDate: 2017-12-05T09:41:10.364439-05:
      DOI: 10.1002/adem.201700805
  • Enhanced Thermal Conductivity of 5A Molecular Sieve with BNs Segregated
    • Authors: Nan Sun; Quan-Ping Zhang, Hao-Ran Sun, Wen-Bin Yang, Yuan-Lin Zhou, Jiang-Feng Song, De-Li Luo
      Abstract: 5A molecular sieves have been widely used as adsorbents in cryogenic distillation for hydrogen isotope separation in fusion reactor engineering, but its low thermal conductivity is detrimental to the process stability. Improving the thermal conductivity of 5A molecular sieves is one of the most important goals for high-performance devices. Here, firm segregated structures with boron nitride sheets (BNs) are constructed around 5A molecular sieve particles. SEM results show 30 µm BNs tend to form the better networks in comparison with that of 0.12 µm BNs at 40 wt% loadings. It is further verified that BNs with the larger size promote the thermal conductivity. Meanwhile, the thermal conductivity increases with the increasing amounts of BNs. XRD and specific surface area results indicate that the sintering and the addition of BNs exert negligible effects on the structure of 5A molecular sieve. These results indirectly show 5A molecular sieve with BNs segregated structures is very likely to be used for the application of hydrogen isotopic separation. Besides, this work provides new insight into the construction of segregated structure in inorganic porous materials.Boron nitride sheets (BNs) are assembled on the surface of 5A molecular sieves via powder mixing. Firm segregated networks are successfully constructed by further compression and sintering for the mixed powders. This work provides a new insight into the fabrication of segregated structures in inorganic porous materials.
      PubDate: 2017-11-28T05:10:32.209911-05:
      DOI: 10.1002/adem.201700745
  • Smart Energetics: Sensitization of the Aluminum-Fluoropolymer Reactive
    • Authors: Sara L. Row; Lori J. Groven
      Abstract: The development of smart energetics is at the forefront of the research community. The desire is to have energetics that could have ON/OFF capability, tunable performance, and/or targeted energy delivery. Therefore, efforts have been focused on designing systems that respond to stimuli in a controlled manner. In this paper, nanoscale aluminum (nAl)/fluoropolymer reactive systems are studied and the piezoelectric nature of the fluoropolymers is used as a means to sensitize the system. Using a capacitor type setup, and drawing on our previous efforts, three fluoropolymer/nAl systems are studied and their sensitivities upon application of a DC voltage are quantified using BAM drop weight as the indicator. It is found, upon application of 1.0 kV, that for all three fluoropolymer/Al systems the sensitivity is greatly increased. For example, for the THV221/nAl system the impact energy required for ignition is reduced from 63 to 10 J. Further increasing the applied voltage is shown to further increase the sensitivity for all systems studied. The role of electroactive phase content and sensitization time is also discussed.Aluminum/fluoropolymer reactives are formulated and demonstrate switchable behavior upon application of a DC voltage. The drop weight sensitivity is on par with powdered RDX and PETN. This demonstrates that piezoelectric fluoropolymer bound reactives could be developed into smart energetics.
      PubDate: 2017-11-14T12:50:22.264431-05:
      DOI: 10.1002/adem.201700409
  • Mesoporous Silica Spheres Incorporated Aluminum/Poly (Vinylidene Fluoride)
           for Enhanced Burning Propellants
    • Authors: Haiyang Wang; Jeffery B. DeLisio, Scott Holdren, Tao Wu, Yong Yang, Junkai Hu, Michael R. Zachariah
      Abstract: In this paper, we demonstrate that preparation by electrospray deposition of mesoporous SiO2 particles can be employed as additives to Aluminum/Poly (Vinylidene Fluoride) (Al/PVDF) to enhance reaction velocity. We find that the reaction velocity of Al/PVDF with 5 wt% SiO2 is 3× higher. The presence of meso-SiO2 appears to accelerate the decomposition of PVDF, with a significant increase in HF release, resulting in higher heat release. We believe that hot-spots around meso-SiO2 may serve as multiple ignition points, with the multi-layered structure promoting heat convection to increase the propagation rate.With 5 wt% mesoporous silica, the burning rate of Al/PVDF film was 3× times higher. The meso-SiO2 appears to highly accelerate the decomposition of PVDF, with a significant increase in HF release and higher heat release. Hot-spots around meso-SiO2 may serve as multiple ignition points and the multi-layered structure promote the heat convection thus highly increase the spreading rate.
      PubDate: 2017-11-14T02:25:26.939421-05:
      DOI: 10.1002/adem.201700547
  • Ultra-Smooth, Chemically Functional Silica Surfaces for Surface
           Interaction Measurements and Optical/Interferometry-Based Techniques
    • Authors: Howard A. Dobbs; Yair Kaufman, Jeff Scott, Kai Kristiansen, Alex M. Schrader, Szu-Ying Chen, Peter Duda, Jacob N. Israelachvili
      Abstract: The study of interfacial phenomena is central to a range of chemical, physical, optical, and electromagnetic systems such as surface imaging, polymer interactions, friction/wear, and ion-transport in batteries. Studying intermolecular forces and processes of interfaces at the sub-nano scale has proven difficult due to limitations in surface preparation methods. Here, we describe a method for fabricating reflective, deformable composite layers that expose an ultra-smooth silica (SiO2) surface (RMS roughness
      PubDate: 2017-10-30T06:25:58.062495-05:
      DOI: 10.1002/adem.201700630
  • The Influence of Hydrogen on the Low Cycle Fatigue Behavior of Medium
           Strength 3.5NiCrMoV Steel Studied Using Notched Specimens
    • Authors: Qian Liu; Andrej Atrens
      Abstract: The influence of hydrogen on low cycle fatigue (LCF) of 3.5NiCrMoV steel electrochemically hydrogen charged in the acidified pH 2 0.1 M Na2SO4 solution is studied. In the presence of hydrogen, the fatigue life decreases significantly by ≈70 to ≈80% by: (i) the crack initiation period is decreased; and (ii) the crack growth rate is accelerated. SEM observation indicates that in the presence of hydrogen, the fracture surface shows flat transgranular fracture with vague striations and some intergranular fracture at lower stresses. The fatigue crack growth rate increases with increasing cyclic stress amplitude and with hydrogen fugacity. Once the fatigue crack reaches a critical length, the specimen becomes mechanical unstable and fracture due to ductile overload occurs. The hydrogen contribution to the final fracture process is not significant.The influence of hydrogen on low cycle fatigue of 3.5NiCrMoV steel electrochemically hydrogen charged is studied. In the presence of hydrogen, the fatigue life decreases significantly by ≈70–80% (as illustrated in the figure) by: (i) the crack initiation period is decreased; and (ii) the crack growth rate is accelerated.
      PubDate: 2017-10-23T08:05:45.765029-05:
      DOI: 10.1002/adem.201700680
  • Challenges of Diffusion Bonding of Different Classes of Stainless Steels
    • Authors: Thomas Gietzelt; Volker Toth, Andreas Huell
      Abstract: Solid state diffusion bonding is used to produce monolithic parts exhibiting mechanical properties comparable to those of the bulk material. This requires diffusion of atoms across mating surfaces at high temperatures, accompanied by grain growth. In case of steel, polymorphy helps to limit the grain size, since the microstructure is transformed twice. The diffusion coefficient differs extremely for ferritic and austenitic phases. Alloying elements may shift or suppress phase transformation until the melting range. In this paper, diffusion bonding experiments are reported for austenitic, ferritic, and martensitic stainless steels possessing varying alloying elements and contents. Passivation layers of different compositions are formed, thus affecting the local diffusion coefficient and impeding diffusion across faying surfaces. As a consequence, different bonding temperatures are needed to obtain good bonding results, making it difficult to control the deformation of parts, since strong nonlinearities exist between temperature, bonding time, and bearing pressure. For martensitic stainless steel, it is shown that it is very easy to obtain good bonding results at low deformation, whereas ferritic and austenitic stainless steels require much more extreme bonding parameters.Diffusion bonding is employed for full cross-sectional joining of complex geometries. The graphical abstract shows a part for ITER (International Thermonuclear Experimental Reactor) made of austenitic stainless steel, containing 3D cooling structures. Thermally stable passivation layers make it difficult to form a monolithic part. Employing a self-stabilizing design, the bonding area is increased with process time, allowing to control deformation.
      PubDate: 2017-10-23T00:20:58.312674-05:
      DOI: 10.1002/adem.201700367
  • Study of Fatigue Behavior of Epoxy-Carbon Composites under Mixed Mode I/II
    • Authors: Clara Rocandio; Jaime Viña, Antonio Argüelles, Silvia Rubiera
      Abstract: This paper presents an experimental assessment of the initiation and propagation of interlaminar cracks under mixed mode I/II dynamic fracture loading of a composite material with an MTM45-1 epoxy matrix and unidirectional IM7 carbon-fiber reinforcement. The aims of the experimental program developed for this purpose are to determine, on the one hand, the initiation curves of the fatigue delamination process, understood as the number of load cycles needed to generate a fatigue crack, and on the other, the crack growth rate (delamination rate) for different percentages of static Gc, in both cases for two mode mixities (0.2 and 0.4) and for a tensile ratio R = 0.1. All this with the goal of quantifying the influence of the degree of mode mixity on the overall behavior of the laminate under fatigue loading. The results show that the energy release rate increases with increasing loading levels for both degrees of mode mixity and that the fatigue limit is located around the same percentages. However, crack growth rate behavior differs from one degree of mode mixity to the other. This difference in the behavior of the material may be due to the varying influence of mode I loading on the delamination process.The initiation curves of the fatigue delamination process of a composite materials with an MTM45-1 epoxy matrix and unidirectional IM7 carbon-fiber reinforcements have been obtained for two mode mixities and for a tensile ratio. Crack growth rate behavior differs from one degree of mode mixity to the other, being the cause the varying of mode I loading on the delamination process.
      PubDate: 2017-10-18T06:30:40.214583-05:
      DOI: 10.1002/adem.201700569
  • Liquid PMMA: A High Resolution Polymethylmethacrylate Negative Photoresist
           as Enabling Material for Direct Printing of Microfluidic Chips
    • Authors: Frederik Kotz; Karl Arnold, Stefan Wagner, Werner Bauer, Nico Keller, Tobias M. Nargang, Dorothea Helmer, Bastian E. Rapp
      Abstract: Polymethymethacrylate (PMMA) is one of the most important thermoplasts and a commonly used material in microsystem fabrication, for example, microfluidics owning mainly to its optical transparency, biocompatibility, low autofluorescence, and low cost. However, being a thermoplastic material PMMA is typically structured using industrial replication techniques making PMMA unsuitable for rapid prototyping. The fact that neither material nor processing technique can be directly transferred from laboratory to industrial state makes the research-to-business conversion often extremely difficult in microfluidics since material properties have a major impact on the final system behavior. This paper presents “Liquid PMMA,” a fast curing viscous PMMA prepolymer which can be used as a negative photoresist and directly structured using ultraviolet or visible light with tens of micron resolution and smooth surfaces. Using this technique microfluidic chips in PMMA can be fabricated within minutes. The cured Liquid PMMA parts show the same high optical transparency, low autofluorescence, and surface properties like commercial PMMA. In this way, microfluidic chips can be rapidly developed and optimized on the laboratory scale in the same material which is later on used on the industrial scale.Polymethylmethacrylate (PMMA) is an important industrial material for microfluidics owing mainly to its optical transparency, biocompatibility, and low cost. We present “Liquid PMMA,” a fast curing PMMA prepolymer which can be used as a negative photoresist and directly structured by light. PMMA microchips can be structured within minutes.
      PubDate: 2017-10-17T07:45:40.963088-05:
      DOI: 10.1002/adem.201700699
  • Using Post-Deformation Annealing to Optimize the Properties of a ZK60
           Magnesium Alloy Processed by High-Pressure Torsion
    • Authors: Seyed A. Torbati-Sarraf; Shima Sabbaghianrad, Terence G. Langdon
      Abstract: A ZK60 magnesium alloy with an initial grain size of ≈10 µm is processed by high-pressure torsion (HPT) through 5 revolutions under a constant compressive pressure of 2.0 GPa with a rotation speed of 1 rpm. An average grain size of ≈700 nm is achieved after HPT with a high fraction of high-angle grain boundaries. Tensile experiments at room temperature show poor ductility. However, a combination of reasonable ductility and good strength is achieved with post-HPT annealing by subjecting samples to high temperatures in the range of 473–548 K for 10 or 20 min. The grain size and texture changes are also examined by electron back scattered diffraction (EBSD) and the results compared to long-term annealing for 2500 min at 450 K. The results of this study suggest that a post-HPT annealing for a short period of time may be effective in achieving a reasonable combination of strength and ductility.The production of ultrafine grained structure through the severe plastic deformation processes is of increasing interests in lightweight materials. Magnesium alloys show poor ductility at room temperature after severe plastic deformation. The results of this study suggest that a post-HPT annealing for a short period of time can be effective in achieving a reasonable combination of strength and ductility.
      PubDate: 2017-10-16T01:46:40.061658-05:
      DOI: 10.1002/adem.201700703
  • Nature-Inspired Lightweight Cellular Co-Continuous Composites with
           Architected Periodic Gyroidal Structures
    • Authors: Oraib Al-Ketan; Ahmad Soliman, Ayesha M. AlQubaisi, Rashid K. Abu Al-Rub
      Abstract: Shell-core cellular composites are a unique class of cellular materials, where the base constituent is made of a composite material such that the best distinctive physical and/or mechanical properties of each phase of the composite are employed. In this work, the authors demonstrate the additive manufacturing of a nature inspired cellular three-dimensional (3D), periodic, co-continuous, and complex composite materials made of a hard-shell and soft-core system. The architecture of these composites is based on the Schoen's single Gyroidal triply periodic minimal surface. Results of mechanical testing show the possibility of having a wide range of mechanical properties by tuning the composition, volume fraction of core, shell thickness, and internal architecture of the cellular composites. Moreover, a change in deformation and failure mechanism is observed when employing a shell-core composite system, as compared to the pure stiff polymeric standalone cellular material. This shell-core configuration and Gyroidal topology allowed for accessing toughness values that are not realized by the constituent materials independently, showing the suitability of this cellular composite for mechanical energy absorption applications.The figure shows designed and 3D printed architected co-continuous composites with rigid shell and soft core configuration. The proposed co-continuous composite employs a topology-property relationship that allows controlling the mechanical and physical properties by tuning its architecture.
      PubDate: 2017-10-16T01:05:42.596707-05:
      DOI: 10.1002/adem.201700549
  • Novel 3D-Printed Hybrid Auxetic Mechanical Metamaterial with
           Chirality-Induced Sequential Cell Opening Mechanisms
    • Authors: Yunyao Jiang; Yaning Li
      Abstract: New hybrid auxetic chiral mechanical metamaterial are designed and fabricated via multi-material 3D printing. Due to the chirality-induced rotation, the material have unique sequential cell-opening mechanisms. Mechanical experiments on the 3D printed prototypes and systematic FE simulations show that the effective stiffness, the Poisson's ratio and the cell-opening mechanisms of the new design can be tuned in a very wide range by tailoring two non-dimensional parameters: the cell size ratio and stiffness ratio of component materials. As example applications, sequential particle release mechanisms and color changing mechanisms of the new designs are also systematically explored. The present new design concepts can be used to develop new multi-functional smart composites, sensors and/or actuators which are responsive to external load and/or environmental conditions for applications in drug delivery and color changing for camouflage.Novel hybrid auxetic chiral mechanical metamaterial are designed and fabricated via multi-material 3D printing. Due to chirality-induced rotation, the new auxetic mechanical metamaterials have unique sequential cell-opening mechanisms under uni-axial tension. As demos, the present new design concepts are used to develop multi-functional smart materials for sequential particle release and color changing for camouflage.
      PubDate: 2017-10-11T08:10:42.053775-05:
      DOI: 10.1002/adem.201700744
  • Mechanical and Electromagnetic Interference Shielding Behavior of C/SiC
           Composite Containing Ti3SiC2
    • Authors: Xiaomeng Fan; Xiaowei Yin, Yanzhi Cai, Litong Zhang, Laifei Cheng
      Abstract: In order to obtain the composites with the integration of structural and functional properties, Ti3SiC2 is introduced into C/SiC due to its excellent damage tolerance and electromagnetic interference (EMI) shielding properties. C/SiC–Ti3SiC2 has the lower tensile strength, while the higher compressive strength than C/SiC. The penetration energy of C/SiC–Ti3SiC2 in the impact experiment is improved at least three times than that of C/SiC, resulting from the improved damage tolerance. With the introduction of Ti3SiC2, the EMI shielding effectiveness increases from 31 to 41 dB in X-band (8.2 to 12.8 GHz) due to the increase of electrical conductivity. C/SiC–Ti3SiC2 reveals the great potential as structural and functional materials based on the multi-functional properties.With the introduction of Ti3SiC2 by liquid silicon infiltration, the dense inter-bundle matrix with high damage-tolerance and electrical-conductivity can be obtained for C/SiC–Ti3SiC2, resulting in the better compressive strength, impact resistance, and electromagnetic interference shielding properties than those of C/SiC, which reveals the great potential as structural and functional materials.
      PubDate: 2017-10-11T08:01:15.82601-05:0
      DOI: 10.1002/adem.201700590
  • Influences of Friction Stir Welding and Post-Weld Heat Treatment on
           Al–Cu–Li Alloy
    • Authors: Yi Lin; Change Lu, Chengyang Wei, Ziqiao Zheng
      Abstract: In this paper, the influences of friction stir welding (FSW) and post-weld heat treatment (PWHT) on the microstructures and tensile properties of Al–Cu–Li alloy are investigated. After FSW, strengthen loss occurred in the welding area. Remarkable softening occurs in the thermo-mechanically affected zone (TMAZ) resulting from dissolution of Al3Li (δ′) phases. Recrystallization and precipitation of ultra-fine δ′ phases take place in the nugget zone (NZ) that lightens the softening degree of this zone. A noteworthy enhancement in the hardness and tensile strength of the joint is achieved after T8 re­aging treatment (3% − pre-deformation, 30 h at 152 °C). However, re-solution treatment coupled with re-aging treatment leads to ductility deterioration in the joint because coplanar slip of coarse Al3Li phases induces severe stress concentration during plastic deformation.The paper investigates the microstructure and mechanical properties evolution of Al–Cu–Li alloy during FSW and PHWTs. The results show that dissolution of strengthening phases induces the strength loss after FSW, and the T8 re-aging treatment can effectively enhances the strength of joint without the ductility being excessively deteriorated.
      PubDate: 2017-10-10T06:21:18.021152-05:
      DOI: 10.1002/adem.201700652
  • 3-D Printing and Development of Fluoropolymer Based Reactive Inks
    • Authors: Fidel D. Ruz-Nuglo; Lori J. Groven
      Abstract: Engineering reactive materials is an ever present goal in the energetics community. The desire is to have energetics configured in such a manner that performance is tailored and energy delivery can be targeted. Additive manufacturing (3-D printing) is one area that could significantly improve our capabilities in this area, if adequate formulations are developed. In this paper, fluoropolymer based reactive inks are developed with micron (mAl) and nanoscale aluminum (nAl) serving, as the fuel at high solids loading (up to 67 wt%) and their viscosity required for 3-D printing is detailed. For the pen-type technique and valves used in this work, it is required to have viscosities on the order of 104–105 cP. For printed traces with apparent diameters under
      PubDate: 2017-10-09T07:10:53.772388-05:
      DOI: 10.1002/adem.201700390
  • Galvanic Corrosion and Mechanical Behavior of Fiber Metal Laminates of
           Metallic Glass and Carbon Fiber Composites
    • Authors: Lee Hamill; Douglas C. Hofmann, Steven Nutt
      Abstract: The possibility of galvanic corrosion typically prohibits the pairing of carbon fiber and aluminum in a fiber metal laminate (FML). In this study, the authors describe a new type of FML comprised of alternating layers of bulk metallic glass (BMG) and carbon fiber reinforced polymer (CFRP) composite. The authors compare the galvanic coupling and mechanical behavior of an Al-based FML and a BMG-CFRP FML. Results show that when paired with CFRPs, BMG exhibits far less galvanic corrosion than aluminum paired with CFRP. In fact, the corrosion between BMG and CFRP is similar in magnitude to the corrosion between aluminum and glass fiber, the two constituent materials of GLARE, the most widely used FML. While interlaminar shear strength and flexural strength are similar for both FML types, the tensile strength and modulus of BMG-based FMLs are greater than those of Al-based FMLs.The galvanic corrosion resistance and mechanical performance of two fiber metal laminates are compared. Results show negligible galvanic corrosion and increased tensile strength and modulus in BMG-CFRP laminates when compared to AL-CFRP counterparts. To date, very few galvanic corrosion resistant options exist for CFRP-based FMLs, and the results of this study expand those options.
      PubDate: 2017-10-09T02:25:49.736964-05:
      DOI: 10.1002/adem.201700711
  • Optimization of Composite Foam Concept for Protective Helmets to Mitigate
           Rotational Acceleration of the Head in Oblique Impacts: A Parametric Study
    • Authors: Yasmine Mosleh; Leonard Pastrav, Aart Willem van Vuure, Bart Depreitere, Jos Vander Sloten, Jan Ivens
      Abstract: Rotational acceleration of the head is known to be the cause of traumatic brain injuries. It was hypothesized that by introducing anisotropy in a foam liner in head protection applications, for example, protective helmets, rotational acceleration transmitted to the head can be further mitigated. Therefore, composite foam with a cylinder/matrix configuration with anisotropy at “macro level” is proposed as a smart structural solution to replace single layer foam headliners of the same weight and thickness. In this paper, a parametric study on the cylinder/matrix configuration is performed and the results are compared with these of single layer expanded polystyrene foam. The structure is subsequently optimized for the best performance in mitigation of rotational acceleration and velocity. Oblique impact results show that the parameters such as the number of cylinders in a given structure, and the compliance of the matrix foam significantly affect the extent of rotational acceleration and velocity mitigation. Optimized composite foam configurations are subsequently proposed and they demonstrate a mitigation of rotational acceleration and velocity up to 44 and 19%, respectively. Moreover, relevant global head injury criteria such as HIC (Head Injury Criterion), RIC (Rotational Injury Criterion), HIPmax (Head Impact Power), GAMBIT (Generalised Acceleration Model for Brain Injury Threshold), and BrIC (Brain Injury Criterion) demonstrated reduction up to 27, 67, 31, 26, and 19%, respectively.In this paper, a parametric study on composite foam with cylinder/matrix configuration is performed to optimize the structure for mitigation of head rotational acceleration during oblique impact. The results show that parameters such as the number of cylinders in the structure, and the compliance of the matrix foam significantly affect the extent of mitigation of head rotational acceleration.
      PubDate: 2017-10-09T02:25:37.747543-05:
      DOI: 10.1002/adem.201700443
  • The Fabrication and Characterization of Bimodal Nanoporous Si with
           Retained Mg through Dealloying
    • Authors: Tyler L. Maxwell; T. John Balk
      Abstract: The fabrication and characterization of bimodal nanoporous silicon films with retained magnesium, achieved through a novel approach utilizing free corrosion dealloying of precursor Si–Mg films in distilled water, is studied. Investigation of film structure and chemical composition using various techniques reveals important characteristics potentially relevant to lithium-ion battery applications. Dealloying of precursor films results in a hierarchal structure, where larger ligaments have an average width of 83 nm and smaller ligaments an average width of 19 nm. A thin, porous surface layer is present on most dealloyed films and is largely composed of magnesium and silicon oxides, as verified by XPS surface analysis. TEM studies reveal that as-dealloyed films are amorphous, but nanocrystalline silicon grains form after vacuum annealing at 500 °C. EDS mapping and XPS reveal three distinct chemical composition regions through the film thickness, where residual magnesium generally increases as a function of film thickness, with the highest amount of retained magnesium at the surface. The ligament size, composition, and structure, combined with the simple, non-hazardous nature of the dealloying method, make this an attractive material and processing technique for efficient and scalable production of lithium-ion battery anode material.This paper presents a facile approach to create bimodal nanoporous silicon films with residual magnesium, by dealloying sputter-deposited silicon-magnesium precursors in distilled water. The microstructure of films before and after annealing is characterized with SEM and TEM, while chemical composition is analyzed with EDS and XPS surface analysis. This material's characteristics make it a promising candidate for lithium–ion battery applications.
      PubDate: 2017-10-09T01:25:42.579217-05:
      DOI: 10.1002/adem.201700519
  • Combined Microwave and Laser Heating for Glazing of 8Y–ZrO2 and
    • Authors: Sebastian Lehmann; Jens Böckler, Monika Willert-Porada, Andreas Rosin, Christian Richter
      Abstract: Sintered porous yttria-stabilized zirconia and zirconia composite ceramics with zirconium silicate are surface glazed by Laser-Assisted Microwave Plasma Processing (LAMPP). Suitable process parameters for surface glazing are determined for those ceramics. The plasma process is monitored by means of pyrometry and optical emission spectroscopy. In order to prove the quality of the surface glazing and to characterize hot corrosion resistance, tests with molten vanadium pentoxide are performed. After 4 h of exposure, the penetration depth of the molten salt is investigated as a function of ceramic composition and pre-treatment by glazing. Upon hot corrosion testing of glazed and non-glazed ceramics, the molten vanadium pentoxide reacts selectively with yttrium oxide, forming yttrium vanadate, and causes crack formation in the zirconia ceramics due to transition to monoclinic zirconia. The results for LAMPP-glazed ceramics show, that a surficial melting phase is achieved because process temperatures exceed 3000 °C. Hence, a dense, crack-free and hardness-enhanced surface layer achieves a better resistance to hot corrosion as compared to non-glazed ceramics. Due to LAMPP-glazing, the vanadium ingress is reduced from 33 to 7 μm for yttria-stabilized zirconia and from 104 to 17 μm for zirconia composite ceramic. Reactions and microstructural changes taking place upon LAMP-Processing are discussed.Suitable process parameters for surface glazing by Laser-Assisted Microwave Plasma Processing of sintered porous zirconia-based ceramics are determined. The plasma process is monitored by means of pyrometry and optical emission spectroscopy. Microstructural investigation and phase analysis is performed before and after hot corrosion test with molten vanadium pentoxide. The dense, crack-free surface layer provides a better resistance to hot corrosion.
      PubDate: 2017-10-04T02:56:26.085561-05:
      DOI: 10.1002/adem.201700615
  • Synthesis of Composite Nanosheets of Graphene and Boron Nitride and Their
           Lubrication Application in Oil
    • Authors: Yuchen Liu; Srikanth Mateti, Chao Li, Xuequan Liu, Alexey M. Glushenkov, Dan Liu, Lu Hua Li, Daniel Fabijanic, Ying Chen
      Abstract: Composite nanosheets of graphene and boron nitride have been produced in large quantities for the first time using high-energy ball milling in ammonia gas as an exfoliation agent. The anti-wear properties of the composite nanosheets as a lubricant additive are investigated via a four-ball method. The results show that the composite nanosheets are exfoliated from the commercial graphite and h-BN powders and combined into graphene/BN composite nanosheets during the ball milling process. The composite nanosheets formed have diameters larger than 200 nm and consist of heterostructures of approximately 10 monolayers of graphene and BN. The composite nanosheets exhibit better wear resistance and friction reduction properties than the homogeneous nanosheets because of the stronger interaction between graphene and BN nanosheets, which can effectively improve the anti-wear properties of mineral base oil as a lubricant additive.The graphene/BN composite nanosheets produced by gas-assisted ball milling process form a protection film on the testing material surface leading to a lower friction coefficient and improved anti-wear properties.
      PubDate: 2017-09-29T10:41:35.337143-05:
      DOI: 10.1002/adem.201700488
  • Understanding Wear Interface Evolution to Overcome Friction and Restrain
           Wear of TiAl–10 wt%Ag Composite
    • Authors: Kang Yang; Hongru Ma, Xiyao Liu, Qiang He
      Abstract: The main objective of this paper is to study wear interface evolution for analyzing the of friction and wear property of TiAl–10 wt%Ag composite. The results show that the friction coefficient and wear rate of TiAl–10 wt%Ag rapidly reduce at 0–25 min and rhythmically fluctuate at 25–60 min. TiAl–10 wt%Ag at 60–240 min obtains low friction and less wear. It is concluded that silver with the low shearing strength of about 125 MPa shows the eminent plastic deformation on wear interface. It effectively reduces friction resistance and material loss, cause TiAl–10 wt%Ag to obtain low friction coefficient, and less wear rate at 0–25 min. Increased silver content, reduces oxide content, and varies wear mechanisms cause the repeating variation of friction resistance and material loss, which results in the rhythmical fluctuation of friction coefficient and wear rate at 25–60 min. High silver contents exist on smooth wear interfaces, exhibit the eminent plastic deformation to lower friction and reduce wear. TiAl–10 wt%Ag obtains the low friction and less wear at 60–240 min.At 240 min, small plastic deformation body forms on smooth wear interface. It indicates that the main wear mechanism of TiAl–10 wt%Ag is plastic deformation. The FESEM surface micro-morphology of wear interface in rectangular region is clearly exhibited. Solid lubricant silver is uniformly distributed on wear interface, and exhibits excellent plastic deformation, leading to low friction and less wear.
      PubDate: 2017-09-28T11:27:37.882845-05:
      DOI: 10.1002/adem.201700637
  • A Combined Electromagnetic Levitation Melting, Counter-Gravity Casting,
           and Mold Preheating Furnace for Producing TiAl Alloy
    • Authors: Jieren Yang; Hu Wang, Yulun Wu, Xuyang Wang, Rui Hu
      Abstract: In this work, the authors describe the development of TiAl castings over a wide range of approaches. To overcome casting defects and cracks that appear in TiAl castings, a novel furnace is designed and constructed. The design combines induction skull melting, counter-gravity casting, and mold heating, which facilitates both filling and microstructure formation via a controllable process. This aim is to improve shaping capabilities and microstructural control for TiAl castings. Melting and casting experiments on TiAl alloys with a nominal composition corresponding to Ti–48Al–2Cr–2Nb (at%) are carried out and discussed. X-ray examinations indicate that the shaping of the TiAl components dose not contain macro casting defects, validating the advantages of this technique. The results are of interest to researchers devoted to technical innovations and modifications for TiAl casting at the industrial scale.The design combines induction skull melting, counter-gravity casting and mold heating a), which facilitates the shaping of the TiAl components b and c), and the decreasing of the defect d) via a controllable process. The results are of interest to researchers devoted to produce high-quality TiAl castings.
      PubDate: 2017-09-25T11:11:37.441471-05:
      DOI: 10.1002/adem.201700526
  • Tensile Strength Evolution and Damage Mechanisms of Al–Si Piston Alloy
           at Different Temperatures
    • Authors: Meng Wang; Jianchao Pang, Yu Qiu, Haiquan Liu, Shouxin Li, Zhefeng Zhang
      Abstract: The Al–Si piston alloys always bear different temperatures because of its peculiar component structure and service condition. Therefore, the tensile strength, elongation to fracture, and corresponding damage mechanisms of Al12SiCuNiMg piston alloys (ASPA) have been investigated with in situ technique at different temperatures. The tensile properties show two-stage tendencies: the former stage (25–280 °C) is determined by easily broken phases with inherent brittleness (such as primary Si), and the fracture behavior presents rapid brittle fracture after reaching the critical stress (about 430 MPa, based on in situ technique and the elastic stress field model). The later one (280–425 °C) is dominated by particles debonding and θphase coarsening. The plastic deformation behavior, dynamic recovery, and flow process become more significant on account of thermal activation. The Considère criterion h = K indicates that the transition of damage behaviors from insufficient local strength to insufficient matrix strength and the corresponding failure model shifts from brittle to ductile fracture. Based on the damage mechanisms, the elastic field model and thermal activation relation model have been established to characterize the strength of the ASPA at different temperature ranges.The tensile properties of Al-Si alloy show two-stage tendencies: the former stage is 25–280 °C and later one is 280–425 °C. Fracture mechanism changes from broken Si (insufficient local strength) at 25 °C to debonding particles (insufficient matrix strength) at 350 °C.The elastic field model and thermally activation relation model have been established to characterize the strength at different temperature ranges.
      PubDate: 2017-09-25T01:52:22.944493-05:
      DOI: 10.1002/adem.201700610
  • Nucleation Crystallography of Ni Grains on CrFeNb Inoculants Investigated
           by Edge-to-Edge Matching Model in an IN718 Superalloy
    • Authors: Wenchao Yang; Pengfei Qu, Lin Liu, Ziqi Jie, Taiwen Huang, Feng Wang, Jun Zhang
      Abstract: In this work, the nucleation crystallography of CrFeNb intermetallic particles as a grain refiner for Ni-based IN718 superalloys is studied using Edge-to-Edge Matching model. Three distinguishable orientation relationships between CrFeNb intermetallic particles and Ni grains are well predicted: [11¯0]Ni∖∖[1¯21¯0]CrFeNb, (111)Ni 1.28° from (0004)CrFeNb, [11¯0]Ni∖∖[1¯21¯0]CrFeNb, (111)Ni 1.32° from (202¯0)CrFeNb, and [11¯0]Ni//[0001]CrFeNb, (111)Ni 0.72° from (202¯0)CrFeNb. The results indicate that CrFeNb intermetallic particles have a strong nucleation potency as an effective grain refiner for Ni-based superalloy and the existence of semi-coherent interfaces between the CrFeNb intermetallic particles and Ni grains. Furthermore, the IN718 superalloy is used to experimentally validate the grain refinement effect of CrFeNb intermetallic particles, showing that its grain size is obviously refined from 8.60 to 1.23 mm. And, the corresponding heterogeneous nucleation mechanism of grain refinement at the atomic level is further identified.The nucleation crystallography of CrFeNb particle on Ni grain is studied using Edge-to-Edge Matching model. Three orientation relationships are predicted to indicate a semi-coherent interface. A relaxation of some atoms may be necessary to minimize the nucleation interface energy. IN718 superalloy is used to validate the grain refinement effect.
      PubDate: 2017-09-20T02:45:26.937527-05:
      DOI: 10.1002/adem.201700568
  • Mechanical Properties of a Novel Zero Poisson's Ratio Honeycomb
    • Authors: Yu Chen; Ming-Hui Fu
      Abstract: In this paper, a novel honeycomb is proposed by embedding a rib into every cell of the existing zero Poisson's ratio (ZPR) configuration, semi re-entrant honeycomb (SRH). Analytical model is developed to investigate the in-plane mechanical properties of the new honeycomb, and the resulting theoretical expressions are compared with the experimental tests and numerical results obtained from two different finite element (FE) models (3D beam model and 3D solid model), leading to a good correlation. FE analysis, analytical modeling, and experimental tests of the new honeycomb show that it can achieve ZPR effect in two principal directions. For further studies, parameters analyses are carried out to explore the dependence of the in-plane mechanical properties versus the geometric parameters. The results show that bending is the dominated deformation model when the new honeycomb is compressed along the x- direction, while stretch controlled in the y- directional compression. It is remarkable that the new proposed honeycomb features superior specific stiffness and more flexible in mechanical properties tailoring compared to the other ZPR honeycombs in the literature. Given these benefits, the new honeycomb may be promising in some practical applications.Honeycombs with zero Poisson's ratio (ZPR) are increasingly used in many important fields because of their unusual properties. A novel ZPR honeycomb is proposed by embedding a rib into every cell of the existing ZPR configuration, semi re-entrant honeycomb (SRH). The new proposed ZPR honeycomb exhibits superior specific stiffness and shows flexible in mechanical properties tailoring. Given these benefits, it may be promising in some applications.
      PubDate: 2017-09-19T01:20:37.058205-05:
      DOI: 10.1002/adem.201700452
  • ZnO Coated Anodic 1D TiO2 Nanotube Layers: Efficient Photo-Electrochemical
           and Gas Sensing Heterojunction
    • Authors: Siowwoon Ng; Petr Kuberský, Milos Krbal, Jan Prikryl, Viera Gärtnerová, Daniela Moravcová, Hanna Sopha, Raul Zazpe, Fong Kwong Yam, Aleš Jäger, Luděk Hromádko, Ludvík Beneš, Aleš Hamáček, Jan M. Macak
      Abstract: The authors demonstrate, in this work, a fascinating synergism of a high surface area heterojunction between TiO2 in the form of ordered 1D anodic nanotube layers of a high aspect ratio and ZnO coatings of different thicknesses, produced by atomic layer deposition. The ZnO coatings effectively passivate the defects within the TiO2 nanotube walls and significantly improve their charge carrier separation. Upon the ultraviolet and visible light irradiation, with an increase of the ZnO coating thickness from 0.19 to 19 nm and an increase of the external potential from 0.4–2 V, yields up to 8-fold enhancement of the photocurrent density. This enhancement translates into extremely high incident photon to current conversion efficiency of ≈95%, which is among the highest values reported in the literature for TiO2 based nanostructures. In addition, the photoactive region is expanded to a broader range close to the visible spectral region, compared to the uncoated nanotube layers. Synergistic effect arising from ZnO coated TiO2 nanotube layers also yields an improved ethanol sensing response, almost 11-fold compared to the uncoated nanotube layers. The design of the high-area 1D heterojunction, presented here, opens pathways for the light- and gas-assisted applications in photocatalysis, water splitting, sensors, and so on.Ultrathin and homogeneous ZnO coatings within high aspect ratio TiO2 nanotubular structure are demonstrated. ALD ZnO coatings within high surface area TiO2 nanotubes layer form a heterojunction with excellent photoelectrochemical activity and good ethanol sensing response. These enhancements are contributed by the passivated surface traps on tube wall, increased light absorption, close match of coating thickness, and Debye length.
      PubDate: 2017-09-19T01:20:26.109066-05:
      DOI: 10.1002/adem.201700589
  • Sub-Micron Anisotropic InP-based III–V Semiconductor Material Deep
           Etching for On-Chip Laser Photonics Devices
    • Authors: Doris Keh-Ting Ng; Chee Wei Lee, Vivek Krishnamurthy, Qian Wang
      Abstract: Two InP-based III–V semiconductor etching recipes are presented for fabrication of on-chip laser photonic devices. Using inductively coupled plasma system with a methane free gas chemistry of chlorine and nitrogen at a high substrate temperature of 250 °C, high aspect ratio, anisotropic InP-based nano-structures are etched. Scanning electron microscopy images show vertical sidewall profile of 90° ± 3°, with aspect ratio as high as 10. Atomic Force microscopy measures a smooth sidewall roughness root-mean-square of 2.60 nm over a 3 × 3 μm scan area. The smallest feature size etched in this work is a nano-ring with inner diameter of 240 nm. The etching recipe and critical factors such as chamber pressure and the carrier plate effect are discussed. The second recipe is of low temperature (−10 °C) using Cl2 and BCl3 chemistry. This recipe is useful for etching large areas of III–V to reveal the underlying substrate. The availability of these two recipes has created a flexible III–V etching platform for fabrication of on-chip laser photonic devices. As an application example, anisotropic InP-based waveguides of 3 μm width are fabricated using the Cl2 and N2 etch recipe and waveguide loss of 4.5 dB mm−1 is obtained.Two InP-based III-V semiconductor etching recipes are presented for fabrication of on-chip laser photonic devices using inductively coupled plasma system with a methane free gas chemistry. The smallest feature size etched in this work is a nano-ring with inner diameter of 240 nm. InP-based waveguides of 3 μm width fabricated give a waveguide loss of 4.5 dB mm–1.
      PubDate: 2017-09-18T08:06:10.535529-05:
      DOI: 10.1002/adem.201700465
  • Multi-Stable Mechanical Structural Materials
    • Authors: Lingling Wu; Xiaoqing Xi, Bo Li, Ji Zhou
      Abstract: Energy absorbing is an important and desirable property in mechanical and civil engineering. Here, a proof-of-concept method is presented as a new approach to achieve artificial mechanical materials with tunable compressive behavior for energy absorbing constructed from unit cells with a snap fit structure. The artificial structure undergoes a series of stable configurations derived from the sequential insertion of the plug into the groove of the snap fit. Both, experimental and simulation results manifest the multi-stable and tunable mechanical properties of the structure. The mechanical energy dissipated by the proposed structure is demonstrated to be dependent on the lead-in angle of the snap fit and the deflection ratio of the groove, as well as on the coefficient of friction between the plug and the groove of the snap fit. The system designed, herein, exhibits mechanical properties that can be tuned not only by adjusting the geometric parameters, but also by tuning the coefficient of friction between the plug and the groove, allowing the mechanical properties to be tailored post-fabrication. Furthermore, the proposed model can be extended to the macro-, micro-, or nanoscales. These findings provide a simple method to obtain artificial materials with tunable energy absorbing properties, which can be applied in areas such as the design of automobile bumpers and foldable devices that facilitate their transportation.In this paper, the authors proposed a new class of mechanical structural material with multi-stable mechanical properties for energy absorbing and demonstrated its fabrication using Sylgard® 184 silicone. The proposed model is constructed from unit cells having a snap fit structure, which has two stable configurations derived from the insertion of the plug into the groove of the snap fit. During the deformation, the tilting beams store a portion of energy, while the remaining energy is dissipated by the mechanical friction effect between the plug and groove of the snap fit. Besides, the energy absorbed (E_in) and the energy required to break the second equilibrium state (E_out) can be tuned independently. The relationships between the mechanical performance and the geometric parameters of the snap fit are investigated via both simulations and experiments. Adjustable energy absorption properties are obtained by changing the width ratio, the lead-in angle, and the coefficient of friction of the snap fit, which permits a more practicable method to tune the mechanical properties of the structural material. The mechanism proposed, herein, is theoretically scale-independent, that is, the manipulation of the mechanical properties can be extended to the micro- or nanoscale, if appropriate fabrication processes are available. This approach proves to be a low-cost, easily accessible, and reusable method that has a broad application potential in industry, such as in the design of automobile bumper beams, vibration isolation materials, and foldable instruments.
      PubDate: 2017-09-18T08:05:45.553865-05:
      DOI: 10.1002/adem.201700599
  • Antibacterial Efficacy of Sacrifical Anode Thin Films Combining Silver
           with Platinum Group Elements within a Bacteria-Containing Human Plasma
    • Authors: Adham Abuayyash; Nadine Ziegler, Jan Gessmann, Christina Sengstock, Thomas A. Schildhauer, Alfred Ludwig, Manfred Köller
      Abstract: Silver (Ag) dots arrays (64 and 400 dots per mm2) are fabricated on a continuous platinum (Pt), palladium (Pd), or iridium (Ir) thin film (sacrifical anode systems for Ag) and for comparison on titanium (Ti) film (non-sacrifical anode system for Ag) by sputter deposition and photolithographic patterning. The samples are embedded within a tissue-like plasma clot matrix containing Staphylococcus aureus (S. aureus), cultivated for 24 h. Bacterial growth is analyzed by fluorescence microscopy. Among platinum group sacrifical anode elements and a dense Ag sample, only the high Ag ion releasing Ag–Ir system is able to inhibit the bacterial growth within the adjacent plasma clot matrix. This study demonstrates that the antibacterial efficiency of Ag coatings is reduced under tissue-like conditions. However, the new sacrificial anode based Ag–Ir system can overcome this limitation.Sacrificial anode silver dot arrays, fabricated on continuous platinum, palladium, or iridium thin films by sputter deposition and photolithographic patterning are embedded within a tissue-like plasma clot matrix containing growing Staphylococcus aureus. Among these samples or a dense Ag film, only the Ag–Ir dot array is able to inhibit the bacterial growth within the plasma clot matrix.
      PubDate: 2017-09-18T08:00:22.123943-05:
      DOI: 10.1002/adem.201700493
  • Effect of Thermal Oxidation on Microstructure and Corrosion Behavior of
           the PVD Hf-Coated Mg Alloy
    • Authors: Dongfang Zhang; Zhengbing Qi, Binbin Wei, Zhoucheng Wang
      Abstract: Hafnium coatings are fabricated on magnesium alloys by magnetron sputtering and are further submitted to the thermal oxidation treatment at temperature of 200, 300, and 400 °C. The thin hafnium oxide film and new grain boundaries are observed on the hafnium coatings during the appropriate treatment temperature (300 °C). These changes in microstructure result in surface densification, oxidation, and low porosity of the treated coating that significantly decrease its susceptibility to corrosion. Consequently, the thermal oxidation treatment hafnium coating exhibits a more positive corrosion potential, lower corrosion current density, and higher polarization resistance than that of the as-deposited coating using an electrochemical system. Moreover, the enhanced adhesion of the treated coating produced by applying an appropriate treatment temperature facilitates an efficient long-term protection of magnesium alloy.Thermal oxidation as an effective yet feasible post-treatment is conducting on the PVD Hf coated Mg alloy. Surface densification, thin oxide film, and enhanced adhesion are obtained on the post treated coating. As a result, the treated coating exhibits more efficient barrier to corrosive media with positive corrosion potential, low corrosion current density, and high polarization resistance.
      PubDate: 2017-09-18T01:00:38.093829-05:
      DOI: 10.1002/adem.201700556
  • MWCNTs as Conductive Network for Monodispersed Fe3O4 Nanoparticles to
           Enhance the Wave Absorption Performances
    • Authors: Kaili Yu; Min Zeng, Yichao Yin, Xiaojun Zeng, Jue Liu, Ya Li, Wukui Tang, Yu Wang, Jing An, Jun He, Ronghai Yu
      Abstract: Magnetic oxides are widely used as electromagnetic (EM) wave absorbers. To promote the absorption efficiency, tremendous efforts have been contributed to adjusting the composite, structure, and size of magnetic loss materials. Employing carbon materials (CNTs, CF, graphene, PANI) is an efficient way to improve the dielectric loss of the matrix. Anchoring the tiny-monodispersed Fe3O4 nanoparticles (NPs) onto the lightweight multi − walled carbon nanotubes (MWCNTs) leads to improve dielectric loss and impedance matching characteristic. Magnetic Fe3O4 NPs along the one-dimensional nanotubes direction play a good synergetic role with MWCNTs due to the interfacial strong chemical and structure bonding. The as-synthesized Fe3O4/MWCNTs nanocomposites exhibit efficient EM wave absorption characteristics (RL av−10 dB) with a maximum reflection loss of −63.64 dB at 12.08 GHz and a diminutive thickness of only 1.6 mm. The magnetic Fe3O4 NPs show strong chemical and structure bonding with the one-dimensional MWCNTs. This work may show a way to broaden the application of such kinds of lightweight high-performance absorbing materials frameworks.Anchoring the tiny and monodispersed Fe3O4 NPs onto the lightweight MWCNTs results in a strong bonding in Fe3O4/MWCNTs nanocomposites, which exhibit excellent EM wave absorption properties. The MWCNTs can act as the conductive network to enhance the dielectric loss and balance the magnetic loss for good impedance matching.
      PubDate: 2017-09-18T01:00:29.878778-05:
      DOI: 10.1002/adem.201700543
  • Fused Deposition Modeling for Unmanned Aerial Vehicles (UAVs): A Review
    • Authors: Helge Klippstein; Alejandro Diaz De Cerio Sanchez, Hany Hassanin, Yahya Zweiri, Lakmal Seneviratne
      Abstract: Additive Manufacturing (AM) is a game changing production technology for aerospace applications. Fused deposition modeling is one of the most widely used AM technologies and recently has gained much attention in the advancement of many products. This paper introduces an extensive review of fused deposition modeling and its application in the development of high performance unmanned aerial vehicles. The process methodology, materials, post processing, and properties of its products are discussed in details. Successful examples of using this technology for making functional, lightweight, and high endurance unmanned aerial vehicles are also highlighted. In addition, major opportunities, limitations, and outlook of fused deposition modeling are also explored. The paper shows that the emerge of fused deposition modeling as a robust technique for unmanned aerial vehicles represents a good opportunity to produce compact, strong, lightweight structures, and functional parts with embedded electronic.Fused deposition modeling (FDM) and Unmanned Ariel vehicles (UAVs), are fast growing technologies, have attracted a great deal of attention. This review studies the process methodology challenges, opportunities, and outlook of FDM and its application in the development of high performance UAVs.
      PubDate: 2017-09-12T02:21:35.040109-05:
      DOI: 10.1002/adem.201700552
  • Hot Deformation Behavior, Dynamic Recrystallization, and Texture Evolution
           of Ti–22Al–25Nb Alloy
    • Authors: Yang Wu; Hongchao Kou, Bin Tang, Jinshan Li
      Abstract: The hot deformation behavior, dynamic recrystallization, and texture evolution of Ti–22Al–25Nb alloy in the temperature range of 950–1050 °C and strain rate range of 0.001–1 s−1 is investigated by plane-strain compression testing on the Gleeble-3500 thermo-mechanical simulator. The results show that the flow stress decreases with the increase of temperature and decrease of strain rate. Besides, the flow curves appear a serrate oscillation at a strain rate of 0.1 s−1 for all the temperature ranges, which may result from instability such as flow localization or micro-cracking. The flow behavior can be expressed by the conventional hyperbolic sine constitutive equation and the calculated deformation activation energy Q in the (α2 + B2) and B2 regions are 631.367 and 304.812 kJ mol−1, respectively. The microstructure evolution is strongly dependent on the deformation parameters, and dynamic recrystallization (DRX) is the dominant softening mechanism in the (α2 + B2) region, including discontinuous dynamic recrystallization (DDRX), and continuous dynamic recrystallization (CDRX). In addition, the ηbcc-fiber of {110} is the dominant texture component in deformed Ti–22Al–25Nb alloy. It is observed that the weakening of the deformation texture is accompanied by the occurrence of DRX, which can be attributed to the large misorientation between DRX grains and neighboring B2 matrix induced by the rotation of DRX grains toward the preferred slip systems.During the process of compression deformation, dynamic recrystallization (DRX) is the dominant softening mechanism in Ti–22Al–25Nb alloy, including discontinuous dynamic recrystallization (DDRX), and continuous dynamic recrystallization (CDRX). In addition, the ηbcc-fiber of {110} is the dominate texture component and the weakening of the deformation texture is accompanied by the occurrence of DRX.
      PubDate: 2017-09-11T01:45:53.110381-05:
      DOI: 10.1002/adem.201700587
  • A Combined Analytic, Numeric, and Experimental Investigation Performed on
           NiTi/NiTiCu Bi-Layer Composites under Tensile Loading
    • Authors: Milad Taghizadeh; Mahmoud Nili-Ahmadabadi, Mostafa Baghani, Mohammad Hassan Malekoshoaraei
      Abstract: Adjusting mechanical behavior and controlling deformation parameters are significant tasks in designing shape memory components. In this paper, an analytical model describes the deformation behavior of NiTi/NiTiCu bi-layer composites under tensile loading. Different deformation stages are considered based on single mechanical behavior at each stage. Closed-form equations are derived for stress–strain variations of bi-layer composites under uniaxial loading–unloading. Bi-layer composites made via the diffusion bonding method from single layers of NiTi alloy with a composition of Ti-50.7 at.% Ni, as an austenitic layer, and Ti-45 at% Ni-5 at% Cu, as a martensitic layer, are produced by the vacuum arc remelting technique. The tensile behavior of single- and bi-layers is investigated by using loading–unloading experiments to find the nominal stress–strain curves. Numerical simulations are also done by employing Lagoudas constitutive model to simulate stress–strain diagrams. The solutions of the analytical method presented are validated by using the numerical simulations as well as the experimental results. With regard to the results obtained from the analytical modeling, the numerical simulations, and the experiments, it is evident that the bi-layer composites with different thickness ratios provide adjustable mechanical behavior that can be considered in different application designs, for example, actuators equipped with shape memory components.In this paper, an analytical model describes the deformation behavior of NiTi/NiTiCu bi-layer composites under tensile loading. Bi-layer composites are made via diffusion bonding method and their tensile behavior is investigated by using loading-unloading experiments. Numerical simulations are also done by employing Lagoudas constitutive model. The model shows a good agreement with both the experimental and FEM results.
      PubDate: 2017-09-06T23:59:47.460143-05:
      DOI: 10.1002/adem.201700395
  • Printing Polymer Nanocomposites and Composites in Three Dimensions
    • Authors: Rouhollah Dermanaki Farahani; Martine Dubé
      Abstract: Recent advances in materials science and three-dimensional (3D) printing hold great promises to conceive new classes of multifunctional materials and components for functional devices and products. Various functionalities (e.g., mechanical, electrical, and thermal properties, magnetism) can be offered by the nano- and micro-reinforcements to the non-functional pure printing materials for the realization of advanced materials and innovative systems. In addition, the ability to print 3D structures in a layer-by-layer manner enables manufacturing of highly-customized complex features and allows an efficient control over the properties of fabricated structures. Here, the authors present a brief overview mainly over the latest progresses in 3D printing of multifunctional polymer nanocomposites and microfiber-reinforced composites including the benefits, limitations, and potential applications. Only those 3D printing techniques that are compatible with polymer nanocomposites and composites, that is, materials that have already been used as printing materials, are introduced. The very hot topic of 3D printing of thermoplastic composites featuring continuous microfibers is also briefly introduced.Various state-of-the-art 3D printing methods compatible with polymer nanocomposite/composite materials are briefly reviewed in this mini-review paper. The paper aims to show that the integration of nano- and micro-reinforcements into 3D printing leads to the realization of innovative functional micro- and macro-devices for various applications such as MEMS, microfluidics, engineered materials and composites, microelectronics, tissue engineering, and biosystems.
      PubDate: 2017-08-29T11:28:35.842624-05:
      DOI: 10.1002/adem.201700539
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