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  Subjects -> COMPUTER SCIENCE (Total: 1996 journals)
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    - COMPUTER SCIENCE (1162 journals)
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    - THEORY OF COMPUTING (8 journals)

COMPUTER SCIENCE (1162 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: 13)
Abakós     Open Access   (Followers: 4)
ACM Computing Surveys     Hybrid Journal   (Followers: 23)
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: 3)
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: 4)
ACM Transactions on Computer Systems (TOCS)     Hybrid Journal   (Followers: 18)
ACM Transactions on Computer-Human Interaction     Hybrid Journal   (Followers: 14)
ACM Transactions on Computing Education (TOCE)     Hybrid Journal   (Followers: 5)
ACM Transactions on Design Automation of Electronic Systems (TODAES)     Hybrid Journal   (Followers: 1)
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: 3)
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: 11)
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: 8)
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: 5)
Advances in Computational Mathematics     Hybrid Journal   (Followers: 15)
Advances in Computer Science : an International Journal     Open Access   (Followers: 14)
Advances in Computing     Open Access   (Followers: 2)
Advances in Data Analysis and Classification     Hybrid Journal   (Followers: 51)
Advances in Engineering Software     Hybrid Journal   (Followers: 26)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 10)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 26)
Advances in Human-Computer Interaction     Open Access   (Followers: 20)
Advances in Materials Sciences     Open Access   (Followers: 16)
Advances in Operations Research     Open Access   (Followers: 11)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Remote Sensing     Open Access   (Followers: 39)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Advances in Technology Innovation     Open Access   (Followers: 3)
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: 4)
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: 7)
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: 1)
Applied Informatics     Open Access  
Applied Mathematics and Computation     Hybrid Journal   (Followers: 33)
Applied Medical Informatics     Open Access   (Followers: 11)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Soft Computing     Hybrid Journal   (Followers: 16)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 4)
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: 134)
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: 8)
Basin Research     Hybrid Journal   (Followers: 5)
Behaviour & Information Technology     Hybrid Journal   (Followers: 52)
Biodiversity Information Science and Standards     Open Access  
Bioinformatics     Hybrid Journal   (Followers: 272)
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: 17)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 33)
Briefings in Bioinformatics     Hybrid Journal   (Followers: 45)
British Journal of Educational Technology     Hybrid Journal   (Followers: 128)
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: 1)
Cell Communication and Signaling     Open Access   (Followers: 1)
Central European Journal of Computer Science     Hybrid Journal   (Followers: 5)
CERN IdeaSquare Journal of Experimental Innovation     Open Access  
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: 12)
Circuits and Systems     Open Access   (Followers: 16)
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: 13)
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: 54)
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  
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: 23)
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: 13)
Computational Statistics & Data Analysis     Hybrid Journal   (Followers: 30)
Computer     Full-text available via subscription   (Followers: 87)
Computer Aided Surgery     Hybrid Journal   (Followers: 3)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 7)
Computer Communications     Hybrid Journal   (Followers: 10)
Computer Engineering and Applications Journal     Open Access   (Followers: 5)
Computer Journal     Hybrid Journal   (Followers: 8)
Computer Methods in Applied Mechanics and Engineering     Hybrid Journal   (Followers: 21)
Computer Methods in Biomechanics and Biomedical Engineering     Hybrid Journal   (Followers: 10)
Computer Methods in the Geosciences     Full-text available via subscription   (Followers: 1)
Computer Music Journal     Hybrid Journal   (Followers: 16)
Computer Physics Communications     Hybrid Journal   (Followers: 6)
Computer Science - Research and Development     Hybrid Journal   (Followers: 7)
Computer Science and Engineering     Open Access   (Followers: 17)
Computer Science and Information Technology     Open Access   (Followers: 12)
Computer Science Education     Hybrid Journal   (Followers: 13)
Computer Science Journal     Open Access   (Followers: 20)

        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  [1589 journals]
  • Robust Free-Standing Nano-Thin SiC Membranes Enable Direct
           Photolithography for MEMS Sensing Applications
    • Authors: Hoang-Phuong Phan; Tuan-Khoa Nguyen, Toan Dinh, Alan Iacopi, Leonie Hold, Muhammad J. A. Shiddiky, Dzung Viet Dao, Nam-Trung Nguyen
      Abstract: This work presents fabrication of micro structures on sub–100 nm SiC membranes with a large aspect ratio up to 1:3200. Unlike conventional processes, this approach starts with Si wet etching to form suspended SiC membranes, followed by micro-machined processes to pattern free-standing microstructures such as cantilevers and micro bridges. This technique eliminates the sticking or the under-etching effects on free-standing structures, enhancing mechanical performance which is favorable for MEMS applications. In addition, post-Si-etching photography also enables the formation of metal electrodes on free standing SiC membranes to develop electrically-measurable devices. To proof this concept, the authors demonstrate a SiC pressure sensor by applying lithography and plasma etching on released ultrathin SiC films. The sensors exhibit excellent linear response to the applied pressure, as well as good repeatability. The proposed method opens a pathway for the development of self-sensing free-standing SiC sensors.Utilizing the superior robustness in SiC, this work develops a fabrication process which applies photolithography directly on free-standing sub-100 nm membranes to form a variety of MEMS structures. This technique eliminates the sticking and under-etch effects and enables metallization on suspended SiC membranes for self-sensing applications.
      PubDate: 2017-12-15T04:31:49.305827-05:
      DOI: 10.1002/adem.201700858
       
  • Masthead: Adv. Eng. Mater. 12∕2017
    • PubDate: 2017-12-14T15:23:24.224558-05:
      DOI: 10.1002/adem.201770042
       
  • Contents: Adv. Eng. Mater. 12∕2017
    • PubDate: 2017-12-14T15:23:23.151888-05:
      DOI: 10.1002/adem.201770043
       
  • Front Cover: Advanced Engineering Materials 12∕2017
    • Abstract: Historic high speed photography from Eadweard Muybridge captures the motions of one of nature's most elegant large organisms. The soft robot represented is an early example of life-like motion from simple molding techniques. This review demonstrates what has been done and what still needs to be done to bridge the immense gap between natural and synthetic organisms. Further information can be found in the article 1700016 by Robert F. Shepherd.
      PubDate: 2017-12-14T15:23:22.868272-05:
      DOI: 10.1002/adem.201770041
       
  • Combined Microwave and Laser Heating for Glazing of 8Y–ZrO2 and
           8Y–ZrO2/ZrSiO4–Composites
    • 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
       
  • Illuminating Origins of Impact Energy Dissipation in Mechanical
           Metamaterials
    • Authors: Peter Vuyk; Shichao Cui, Ryan L. Harne
      Abstract: Elastomeric mechanical metamaterials have revealed striking ability to attenuate shock loads at the macroscopic level. Reports suggest that this capability is associated with the reversible elastic buckling of internal beam constituents observed in quasistatic characterizations. Yet, the presence of buckling members induces non-affine response at the microscale, so that clear understanding of the exact energy dissipation mechanisms remains clouded. In this report, the authors examine a mechanical metamaterial that exhibits both micro- and macroscopic deformations under impact loads and devise an experimental method to visualize the resulting energy dissipation mechanisms. By illuminating the dynamic distribution of strain in the metamaterial, the authors uncover a rational way to program the macroscopic deformation and enhance impact mitigation properties. The results emphasize that mechanical metamaterials clearly integrate materials science and structural engineering, encouraging future interdisciplinary studies to capitalize on the opportunities.Elastomeric mechanical metamaterials that include internal buckling beam members are effective to dissipate impact energy. The authors uncover the origins of the energy dissipation mechanisms by a digital image correlation technique that illuminates the strain distributions exemplified in the figure. With this knowledge, the authors explore and verify new ways to program mechanical metamaterials for enhanced impact mitigation properties.
      PubDate: 2017-12-05T09:26:27.103824-05:
      DOI: 10.1002/adem.201700828
       
  • Microstructure and Mechanical Properties of Ti2AlNb-Based Alloys
           Synthesized by Spark Plasma Sintering from Pre-Alloyed and Ball-Milled
           Powder
    • Authors: Mengchen Li; Qi Cai, Yongchang Liu, Zongqing Ma, Zumin Wang
      Abstract: Ti2AlNb-based alloys are synthesized by spark plasma sintering from pre-alloyed and ball-milled Ti–22Al–25Nb powder, and the structure of the alloys is regulated by aging at 800 °C for 0.5, 1, 2, and 3 h. Comparison of phase composition, microstructure, and mechanical properties are made in this study. Aging in the B2 + O phase region refers to the reversible transformation of B2  O. Complete B2 + O Widmanstätten structure is obtained in the aged alloys synthesized from pre-alloyed powder, and the ones from milled powder contain acicular O and B2 + O Widmanstätten structure. Ball milling eliminates the B2 + O colonies, facilitates the continuous transformation of O  B2, and induces acicular O in the alloys; however, the hardness of these alloys is decreased in contrast with that of the ones synthesized from pre-alloyed powder. Owing to the precipitation strengthening based on a large amount of fine O-phase precipitates, the 3 h aged alloy from pre-alloyed powder exhibits comprehensive mechanical properties with Vickers hardness of 448 ± 9 HV, ultimate tensile strength of 730 MPa, and elongation of 0.43%.Ti2AlNb alloys are synthesized by spark plasma sintering and aged at 800 °C. Besides Widmanstätten B2 + O, the typical microstructure is B2 + O colonies and acicular O for alloys from pre-alloyed and ball-milled powder, respectively. Due to precipitation strengthening of O phase, favorable mechanical properties are obtained with hardness of 448 ± 9 HV, ultimate tensile strength of 730 MPa, and elongation of 0.43%.
      PubDate: 2017-12-04T04:27:10.822908-05:
      DOI: 10.1002/adem.201700659
       
  • On the Wetting States of Low Melting Point Metal Galinstan® on
           Silicon Microstructured Surfaces
    • Authors: Ethan Davis; Sidy Ndao
      Abstract: The primary goal of this article is to measure the wetting characteristics of a low melting point metal to determine the efficacy of this type of material for possible use in thermal energy storage applications. Galinstan®, a commercially available alloy consisting of Gallium, Indium, and Tin is subjected to contact angle measurements on various silicon surfaces at varying temperatures. Due to the oxidation characteristics of Galinstan, all experiments are conducted in an inert nitrogen environment (
      PubDate: 2017-12-04T04:15:37.033303-05:
      DOI: 10.1002/adem.201700829
       
  • Toward Functional 3D Architectured Platform: Advanced Approach to Anchor
           Functional Metal Oxide onto 3D Printed Scaffold
    • Authors: Junghyun Choi; Patrick Joo Hyun Kim, Jihoon Seo, Jiseok Kwon, Sangkyu Lee, Taeseup Song
      Abstract: The authors first report the three-dimensional (3D) structured CeO2–PLA scaffold using a 3D printing methodology. The scaffold is prepared by decorating functional metal-oxide nanoparticles onto the 3D-printed polylactic acid (PLA) platform via an electrostatic interaction and is applied to the applications for photochemical degradation. As-designed CeO2–PLA scaffold shows high photocatalytic degradation performance toward methyl orange under a light irradation. Furthermore, the CeO2–PLA scaffold shows reasonable degradation performance even after it is washed and reevaluated; this result demonstrates the benefit of 3D-printed CeO2–PLA scaffold that it can be recycled several times without losing the catalysts.The authors fabricate the 3D printed scaffold with metal oxide decoration. Positive charged metal oxide nanoparticle electrostatically interacts with negative charged 3D printed polylactic acid scaffold. Metal oxide decorated scaffold is demonstrated as a photocatalyst. It shows reasonable photocatalytic performance and possibility of reusable. Our facile methodology is able to extend to the application fields of 3D printing.
      PubDate: 2017-12-04T04:05:52.040574-05:
      DOI: 10.1002/adem.201700901
       
  • Fabrication and Properties of Micro- and Nanoscale Metallic Glassy Wires:
           A Review
    • Authors: Jun Yi
      Abstract: A large number of metallic glasses (MGs) with high mechanical and functional performance that cannot be achieved by traditional metals in various alloy systems have been developed. At the same time, people realized that micro- and nanoscale wires can improve properties and extend functionality of bulk materials. Therefore, intensive effort has been made to fabricate micro- and nanoscale MG wires, and study their mechanical and physical behavior to achieve high performance. This article reviews fabrication, properties and applications of the wires, and presents technical and theoretical challenges, which must be tackled to achieve high-performance MG wire devices and understand physical mechanisms of mechanical and functional behaviors of the wires.This paper critically reviews fabrication, mechanical, and functional behavior of micro- and nanoscale metallic glassy wire wires and their physical mechanisms, and highlights the state of the art of the wires. In addition, this paper delineates technical and theoretical challenges, which will be tackled to achieve high-performance metallic glassy wire devices and further understanding of the physical mechanisms.
      PubDate: 2017-12-01T08:05:46.203661-05:
      DOI: 10.1002/adem.201700875
       
  • Initiated Chemical Vapor Deposition: A Versatile Tool for Various Device
           Applications
    • Authors: Seung Jung Yu; Kwanyong Pak, Moo Jin Kwak, Munkyu Joo, Bong Jun Kim, Myung Seok Oh, Jieung Baek, Hongkeun Park, Goro Choi, Do Heung Kim, Junhwan Choi, Yunho Choi, Jihye Shin, Heeyeon Moon, Eunjung Lee, Sung Gap Im
      Abstract: Advances in device technology have been accompanied by the development of new types of materials and device fabrication methods. Considering device design, initiated chemical vapor deposition (iCVD) inspires innovation as a platform technology that extends the application range of a material or device. iCVD serves as a versatile tool for surface modification using functional thin film. The building of polymeric thin films from vapor phase monomers is highly desirable for the surface modification of thermally sensitive substrates. The precise control of thin film thicknesses can be achieved using iCVD, creating a conformal coating on nano-, and micro-structured substrates such as membranes and microfluidics. iCVD allows for the deposition of polymer thin films of high chemical functionality, and thus, substrate surfaces can be functionalized directly from the iCVD polymer film or can selectively gain functionality through chemical reactions between functional groups on the substrate and other reactive molecules. These beneficial aspects of iCVD can spur breakthroughs in device fabrication based on the deposition of robust and functional polymer thin films. This review describes significant implications of and recent progress made in iCVD-based technologies in three fields: electronic devices, surface engineering, and biomedical applications.Considering device design, initiated chemical vapor deposition (iCVD) inspires innovation as a platform technology that extends the application range of a material or device. iCVD serves as a versatile tool for direct building of polymeric thin films on substrates from vapor phase monomers. This review describes significant implications of and recent progress made in iCVD-based technologies in three fields: electronic devices, surface engineering, and biomedical applications.
      PubDate: 2017-11-30T05:56:54.537649-05:
      DOI: 10.1002/adem.201700622
       
  • Drop-on-Demand Inkjet Printing of Thermally Tunable Liquid Crystal
           Microlenses
    • Authors: Ellis Parry; Serena Bolis, Steve J. Elston, Alfonso A. Castrejón-Pita, Stephen M. Morris
      Abstract: In this letter, the authors demonstrate Drop-on-Demand printing of variable focus, polarization-independent, liquid crystal (LC) microlenses. By carefully selecting the surface treatment applied to a glass substrate, the authors are able to deposit droplets with a well-defined curvature and contact angle, which result in micron-sized lenses with focal lengths on the order of 300–900 µm. Observations with an optical polarizing microscope confirm the homeotopic alignment of the LC director in the droplets, which is in accordance with the polarization independent focal length. Results show that microlenses of different focal lengths can be fabricated by depositing successive droplets onto the same location on the substrate, which can then be used to build up programmable and arbitrary arrays of microlenses of various lens sizes and focal lengths. Finally, the authors utilize the thermal dependency of the order parameter of the LC to demonstrate facile tuning of the focal length. This technique has the potential to offer a low-cost solution to the production of variable focus, arbitrary, microlens arrays.Tuneable microlens arrays are fabricated via the drop-on-demand inkjet printing of a nematic liquid crystal onto a polymer coated substrate. The programmable and arbitrary microlens arrays produced exhibit excellent polarization independent focussing properties with high numerical apertures.
      PubDate: 2017-11-29T07:45:29.485099-05:
      DOI: 10.1002/adem.201700774
       
  • Texture and Electromagnetic Coupling Properties
    • Authors: Luis Edmundo Fuentes-Cobas; María Cristina Grijalva-Castillo, Luis Fuentes-Montero, José Andrés Matutes-Aquino, Juan Méndez-Nonell
      Abstract: The estimation of physical properties in textured polycrystals is reviewed. “Principal” properties, which relate actions and responses within the same subsystem (electric, elastic, …), as well as “coupling” properties (e.g., piezomagnetism), linking actions, and responses associated with various subsystems (magneto-elastic, thermo-electric, …) are analyzed. Tensor ranks from 1 to 4, with polar and axial characteristics are considered. Virtual-time inversion (the case of magnetoelectricity) is taken into account. Matrix and surface representations are considered. Significant differences in the effect of texture on properties arise from the diversity of properties tensors ranks and polar/axial natures. To predict the effective values of coupling properties, precautions required for application of the Voigt, Reuss, and Hill approximations are pointed out. At all stages of the proposed methodology, a symmetrized spherical harmonics treatment of the orientation distribution functions, the inverse pole figures and (single- and polycrystals) physical properties is applied. For the case of magnetostriction, a functional program for estimating polycrystal performance is included as Supporting Information. The input data are the single-crystal property coefficients and the polycrystal inverse pole figure parameters. The coincidence of predicted magnetostriction coefficients with experimentally measured values is satisfactory. Recently established considerations regarding the characterization of coupling properties in complex materials are divulged.Crystallographic texture plays an important role in materials' performance. In this article, the authors review the diversity of texture properties relationships found in functional materials. Several coupling interactions are analyzed. The figure shows the case of galfenol magnetostriction as a function of axial texture.
      PubDate: 2017-11-29T07:11:02.798681-05:
      DOI: 10.1002/adem.201700827
       
  • Creep Behavior of High-Nb TiAl Alloy at 800–900 °C by
           Directional Solidification
    • Authors: Qi Wang; Ruirun Chen, Yaohua Yang, Jingjie Guo, Yanqing Su, Hongsheng Ding, Hengzhi Fu
      Abstract: Cold crucible directional solidification Ti44Al6Nb1.0Cr alloy is crept at 800–900 °C. Experimental results show that creep lifetime significantly decreases with the increasing creep temperature. When creeping at 900 °C under 130 MPa, the TQ twinning is activated in lamellar structures. The TQ twinning shows a strong dependency on temperature during creep under low creep-stress and it can overcome α2 lamellae and transfer into adjacent γ lamellae. The hardening by mechanical twinning and the softening by α2 lamellar dissolution take place at different zones in lamellar structures and the strain incompatibility between hardening zone and softening zone promotes the microcracks to form in lamellar structures. The deformation characteristic of hard and soft lamellae is studied. Moreover, recrystallization γ phase formed in lamellar structures near colony boundary during creep at 900 °C accelerates the creep failure.Ti-44Al-6Nb-1.0Cr alloy is crept at 800–900 ºC. TQ twinning is activated in lamellar structures during creep at 900 ºC/130 MPa and it overcomes α2 lamella and transfers into adjacent γ lamella. Hardening by mechanical twinning and softening by α2 lamellar dissolution tack place at different zones.
      PubDate: 2017-11-28T08:21:03.977748-05:
      DOI: 10.1002/adem.201700734
       
  • Effect of Sc and Zr on Microstructure and Mechanical Properties of As-Cast
           Al–Li–Cu Alloys
    • Authors: Yang Wang; Zheng Li, Tianfu Yu, Aboubakr Medjahed, Ruizhi Wu, Legan Hou, Jinghuai Zhang, Xinlin Li, Milin Zhang
      Abstract: Effect of Sc and Zr addition on microstructure and mechanical properties of as-cast Al–Li–Cu alloys are investigated. The results show that, a significant grain refinement can be caused by Sc and Zr. The coarse dendritic microstructure is transformed into equiaxed grains after adding Sc and Zr. The refinement can be attributed to the primary particles, Al3(Sc,Zr), of which the orientation is close to that of α-Al matrix. The primary particles prevent the unsuitable diffusion and act as heterogeneous nucleation sites for α-Al in the process of solidification. The model for the multi-layer structure evolution of primary particle is established. Moreover, the mechanical properties of as-cast Al–Li–Cu–Sc–Zr alloy are affected markedly because of the addition of Sc and Zr. The solid solution strengthening and Hall–Petch strengthening are primary strengthening mechanisms, YS = ΔσHPS + Δσsss + 104 (MPa).The coarse dendritic microstructure is transformed into equiaxed grains after adding Sc and Zr. The refinement can be attributed to the primary particles, Al3(Sc,Zr). The model for the multi-layer structure evolution of primary particle is established. The solid solution strengthening and Hall–Petch strengthening are primary strengthening mechanisms, YS = ΔσHPS+Δσsss+104(MPa).
      PubDate: 2017-11-28T05:11:17.308112-05:
      DOI: 10.1002/adem.201700898
       
  • Inorganic Thin Film Deposition and Application on Organic Polymer
           Substrates
    • Authors: Jitesh Hora; Colin Hall, Drew Evans, Eric Charrault
      Abstract: This review details the emerging area of inorganic thin film coatings on polymer substrates, from examples of applications through to the fabrication processes and the underlying growth mechanism(s). Of particular focus is the use of physical vapor deposition to deposit thin metal and/or metal oxide films onto polymeric materials. This primary focus highlights an area of research, that is, gaining in popularity, as researchers attempt to provide insight into the adaption of a well-established manufacturing process to be compatible with the ever expanding range of polymer substrates. The motivation for doing so comes from the evolution of existing industry (i.e., the semi-conductor sector) to fabricate new devices (i.e., flexible electronics). In addition, the research challenges faced in achieving evaporated and sputtered thin film coatings on polymeric substrates, such as mechanical and thermal considerations will be discussed.Regardless of chemistry, molecular weight and substrate type (thick solid polymer bulk, foil or thin layer deposited onto another substrate), the inherent properties of polymers present challenges throughout the whole PVD process. Overcoming these challenges and enhancing the resultant thin film performance is critical for the advancement of new technology, such as flexible electronics.
      PubDate: 2017-11-28T05:11:03.398898-05:
      DOI: 10.1002/adem.201700868
       
  • Enhanced Thermal Conductivity of 5A Molecular Sieve with BNs Segregated
           Structures
    • 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
       
  • Optimization Techniques for Improving the Performance of Silicone-Based
           Dielectric Elastomers
    • Authors: Anne Ladegaard Skov; Liyun Yu
      Abstract: Dielectric elastomers are possible candidates for realizing products that are in high demand by society, such as soft robotics and prosthetics, tactile displays, and smart wearables. Diverse and advanced products based on dielectric elastomers are available; however, no elastomer has proven ideal for all types of products. Silicone elastomers, though, are the most promising type of elastomer when viewed from a reliability perspective, since in normal conditions they do not undergo any chemical degradation or mechanical ageing/relaxation. Within this review, different pathways for improving the electro-mechanical performance of dielectric elastomers are highlighted. Various optimization methods for improved energy transduction are investigated and discussed, with special emphasis placed on the promise each method holds. The compositing and blending of elastomers are shown to be simple, versatile methods that can solve a number of optimization issues. More complicated methods, involving chemical modification of the silicone backbone as well as controlling the network structure for improved mechanical properties, are shown to solve yet more issues. From the analysis, it is obvious that there is not a single optimization technique that will lead to the universal optimization of dielectric elastomer films, though each method may lead to elastomers with certain features, and thus certain potentials.Different pathways for improving the performance of dielectric elastomers are highlighted. Various optimization methods for improved energy transduction are discussed, with special emphasis placed on the promise each method holds. It is shown that there is not one single optimization technique that will lead to the universal optimization, though each method may lead to elastomers with certain features and potentials.
      PubDate: 2017-11-27T09:55:50.215442-05:
      DOI: 10.1002/adem.201700762
       
  • Corrugation Reinforced Composites: A Method for Filling Holes in
           Material-Property Space
    • Authors: Mark Fraser; Hatem S. Zurob, Peidong Wu
      Abstract: Material-property space is filled with holes representing desirable combinations of properties, such as high strength and high necking strain. One way to fill those holes is to use architectured materials. In this work, Finite Element Modeling (FEM) simulations are performed to evaluate composites with a corrugated reinforcement architecture across a range of volume fractions and corrugation heights for a model copper-steel system. The corrugated reinforcement geometry shows large improvements in necking strain, which increases with corrugation height, without sacrificing strength, and fills a desirable region in material-property space. Additionally, it is found that the necking strain of a matrix material can be increased by adding a less ductile reinforcing material provided it has a highly corrugated geometry. The improvement in necking strain seen in these composites is attributed to a boost in work hardening that results from an evolving reinforcement alignment as the corrugation unbends.In this work, Finite Element Modeling simulations demonstrated that corrugation reinforced composites with different geometries and volume fractions can access the hole in material-property space characterized by high strength and high necking strain. These composites improve on the necking strain of straight reinforced composites by taking advantage of a boost in work hardening that results from the unbending corrugations.
      PubDate: 2017-11-27T09:50:45.984875-05:
      DOI: 10.1002/adem.201700834
       
  • Tailoring Microstructure and Properties of Fine Grained Magnesium Alloys
           by Severe Plastic Deformation
    • Authors: Alexei Vinogradov; Vladimir N. Serebryany, Sergey V. Dobatkin
      Abstract: Modern wrought magnesium alloys have poor formability at room temperature, which impedes the wider uptake of these alloys by the industry. Over the last decades, research activities in the area of magnesium alloy development have grown enormously and have produced a pallet of exciting findings, which the authors summarize in this concise review focused on the effect of the microstructure, primarily of grain size, on room temperature ductility of wrought Mg-based alloys. Well-established paths and modern strategies to control over the grain size distribution are discussed. It is demonstrated that the use of severe plastic deformation techniques for ultimate grain refinement in magnesium alloys opens new windows for improving their mechanical properties profile by managing both strength and ductility in a wide range. However, it is shown that grain size alone cannot be regarded as a key parameter controlling the mechanical behavior of Mg alloys. The effect of texture is of paramount importance for the overall mechanical response of Mg alloys and this may supersede the influence of grain size.The severe plastic deformation techniques possess great flexibility in tailoring microstructures for desired combination of mechanical properties in structural materials. Routes to obtain an excellent balance of high strength and ductility in wrought magnesium alloys through a combination of grain refinement and texture control in the course of severe plastic deformation are discussed.
      PubDate: 2017-11-27T02:06:17.909176-05:
      DOI: 10.1002/adem.201700785
       
  • Flexible Triboelectric Nanogenerator Based on High Surface Area TiO2
           Nanotube Arrays
    • Authors: Raheleh Mohammadpour
      Abstract: Triboelectric nanogenerators (TENGs) can harvest mechanical energy through coupling triboelectric effect and electrostatic induction. Typically, TENGs consist of organic materials, however on account of the potentially wide range of applications of TENGs as the self-powered portable/wearable electronics, biomedical devices, and sensors; semiconductor metal oxide materials can be promising candidates to be incorporating in TENG structure. Here, flexible TENG based on self-organized TiO2 nanotube arrays (TNTAs) is fabricated via anodization method. The introduced flexible large area nanotubular electrode is employed as the moving electrode in contact with Kapton film in vertical contact separation mode of TENG. The fabricated TENG can deliver output voltage of 40 V with the current density of 1 μA cm−2. To evaluate the role of nanostructured interface, its performance has been compared to the thin film flat compact TiO2 electrode. The results of extracted charge measurements under short circuit condition indicate that larger triboelectric charge density formed in TNTA-based electrode (about 110 nC per cycle of press and release) is in comparison to 15 nC in flat TiO2 electrode. Due to the extensive range of applications of TiO2, the introduced structure can potentially be applicable in various types of self-powered systems such as photo-detectors and environmental gas and bio-sensors.Large scale flexible tribolectric nanogenerator (TENG) based on TiO2 nanotube arrays (TNTAs) can deliver output voltage of 40 V with the current density of 1 µA cm–2.
      PubDate: 2017-11-27T02:06:08.225484-05:
      DOI: 10.1002/adem.201700767
       
  • Polyethylene Glycol–CaCl2 Coordination Compounds as a Novel Form-Stable
           Phase Change Material with Excellent Thermophysical Properties
    • Authors: Qinrong Sun; Haiquan Zhang, Yanping Yuan, Xiaoling Cao, Liangliang Sun
      Abstract: Polyethylene glycols (PEGs) have been extensively studied as phase change materials (PCMs). To overcome the problem of liquid leakage, the authors firstly report a novel form-stable phase change material (FSPCM) using coordination compound. The structure, morphology, thermal property, and thermal stability of the self-prepared samples are determined. The obtained results confirm the existence of coordination bonds between PEG and Ca2+ species, and no liquid leakage is observed for the synthesized PEG–CaCl2 composites at temperatures as high as 120 °C. The PEG8000–CaCl2 (1:2) FSPCM exhibits a relatively large latent heat of 147.7 J g−1, corresponding to 87.8% of that of pure PEG. From the dynamical viewpoint, the activation energy of crystallization process is increased by only 5.2% for the PEG8000–CaCl2 composite due to the formation of coordination bonds; however, the activation energy is reduced by 18.3% during melting process. After adding 3 wt% conductive carbon black, the heat storage performance of the PEG phase change material can be optimized. The PEG-CaCl2 composite would be a promising material for thermal energy storage applications and can be used in various engineering fields.Part of the PEG polymer is converted into a three-dimensional framework by using coordination chemical bonds between PEG and Ca. This method can be one-step preparation of form-stable phase change material (PEGX-CaCl2).
      PubDate: 2017-11-23T09:11:38.194905-05:
      DOI: 10.1002/adem.201700643
       
  • Intelligent Sensing System Based on Hybrid Nanogenerator by Harvesting
           Multiple Clean Energy
    • Authors: Yuhang Xie; Hulin Zhang, Guang Yao, Saeed Ahmed Khan, Min Gao, Yuanjie Su, Weiqing Yang, Yuan Lin
      Abstract: The inexhaustible mechanical kinetic energy can be extracted from wind and flowing water. Besides, flowing water also possesses electrostatic energy owing to the triboelectric charges caused by contacting with surrounding media, such as air. Here, a rotating hybridized triboelectric nanogenerator (TENG) has been established, by comprising of a water-TENG (W-TENG), a disk-TENG (D-TENG), and an electromagnetic generator (EMG), which has been explored for simultaneously harvesting energies from flowing water and wind. The W-TENG is fabricated by wheel blades, polyvinylidene fluoride (PVDF), superhydrophobic polytetrafluoroethylene (PTFE), and aluminum to harvest the electrostatic energy. Moreover, the flowing water and wind impact on the wheel blades also causes the rotation motion of D-TENG and EMG, resulting in being converted into electricity. At the rotation speed of 200 rpm, the short circuit current of D-TENG and EMG can reach 0.4 μA and 7 mA, respectively. The open circuit voltage of W-TENG can be up to 10 V at a flowing water rate of 60 ml s−1. Besides, the hybridized NG is demonstrated to harvest water and wind energy and to act as a power source to charge a lithium battery or capacitor, which can drive LEDs, PH monitoring system, and wireless temperature and humidity sensing system. All these results show the potentials of the hybridized NG for harvesting multiple types of energies from the environment and constructing different self-powered systems.In this work, the authors demonstrate a new hybrid nanogenerator, which have been developed for simultaneously harvesting mechanical energies from flowing water and wind. The hybrid device can be employed to fabricate a wireless self-powered system for temperature and humidity sensing. This work promotes the development of renewable energy and presents a promising application for self-powered remote sensing.
      PubDate: 2017-11-23T09:11:30.807325-05:
      DOI: 10.1002/adem.201700886
       
  • A Review on Piezoelectric, Magnetostrictive, and Magnetoelectric Materials
           and Device Technologies for Energy Harvesting Applications
    • Authors: Fumio Narita; Marina Fox
      Abstract: In the coming era of the internet of things (IoT), wireless sensor networks that monitor, detect, and gather data will play a crucial role in advancements in public safety, human healthcare, industrial automation, and energy management. Batteries are currently the power source of choice for operating wireless network devices due to their ease of installation; however, they require periodic replacement due to capacity limitations. Within the scope of the IoT, battery maintenance of the trillion sensor nodes that may be implemented will be practically infeasible from environmental, resource, and labor cost perspectives. In considering individual self-powered sensor nodes, the idea of harvesting energy from ambient vibrations, heat, and electromagnetic waves has recently triggered noticeable research interest in the academic community. This paper gives an overview of energy harvesting materials and systems. Three main categories are presented: piezoelectric ceramics/polymers, magnetostrictive alloys, and magnetoelectric (ME) multiferroic composites. State-of-the-art harvesting materials and structures are presented with a focus on characterization, fabrication, modeling and simulation, and durability and reliability. Some perspectives and challenges for the future development of energy harvesting materials are also highlighted.Recent progress in piezoelectric ceramics/polymers, magnetostrictive alloys, and magnetoelectric (ME) multiferroic composites for energy harvesting applications is systematically summarized. A survey of the challenges in characterization, fabrication, modeling and simulation, and durability and reliability is presented.
      PubDate: 2017-11-21T08:56:01.381003-05:
      DOI: 10.1002/adem.201700743
       
  • Optimization of Strength-Electrical Conductivity Properties in Al–2Fe
           Alloy by Severe Plastic Deformation and Heat Treatment
    • Authors: Andrey E Medvedev; Maxim Y Murashkin, Nariman A Enikeev, Ruslan Z Valiev, Peter D Hodgson, Rimma Lapovok
      Abstract: High-pressure torsion at room temperature followed by two processing routes, either 1) annealing at 200 °C for 8 h or 2) elevated temperature (200 °C) high-pressure torsion, are employed to obtain simultaneous increase in mechanical strength and electrical conductivity of Al–2 wt%Fe. The comparative study of microstructure, particle distribution, mechanical properties, and electrical conductivity for both processing routes gives the optimal combination of high mechanical strength and high electrical conductivity in Al–2Fe alloy. It is shown that while the mechanical strength is approximately the same for both processing routes (>320 MPa), high-pressure torsion at elevated temperature results in higher conductivity (≥52% IACS) due to reduction of Fe solute atom concentration in Al matrix compared to annealing treatment. High-pressure torsion at 200 °C has been demonstrated as a new and effective way for obtaining combination of high mechanical strength and electrical conductivity in Al–Fe alloys.The dynamic aging of UFG Al–Fe alloy (HPT at 200 °C) has been used to enhance the electrical conductivity. Comparison of observed results with static aging (annealing at 200 °C for 8 h), also performed in present work, shows superiority of dynamically aged alloy over statically aged. The increase of electrical conductivity by ≈3% IACS is accompanied by substantial decrease of heat treatment time from 8 h for static annealing to 5 min for high temperature deformation.
      PubDate: 2017-11-20T02:50:28.962728-05:
      DOI: 10.1002/adem.201700867
       
  • Microstructure and Texture Development in Al–3%Brass Composite
           Produced through ARB
    • Authors: Ehsan Tolouei; Mohammad Reza Toroghinejad, Hamed Asgari, Hossein Monajati Zadeh, Fakhreddin Ashrafizadeh, Jerzy A. Szpunar, Philippe Bocher
      Abstract: In the present work, aluminum-3% brass composite sheets are produced by accumulative roll bonding (ARB) process up to nine passes at ambient temperature. Evolution of rolling texture is studied by texture measurement using X-ray diffraction method. The results show that ARB process leads to the formation of copper ({112} ) and Dillamore ({4 4 11} ) as the major texture components. The intensity of copper and Dillamore components enhances to values as high as 19 times that of random with increasing number of passes to 9. It is observed that the 5th pass is a transition in development of the texture components, after which the intensities undergo a drop. The textures are comparable to ARB process of high purity aluminum, indicating that the addition of 3% brass particles do not cause any significant change in the deformation behavior. Electron backscatter diffraction (EBSD) technique is used to examine the microstructure; the results reveal formation of ultrafine grains (UFG), starting in the 3rd pass and covers the entire structure after the 5th pass. The major mechanisms involved are identified as rotation of the sub-grains, as well as grain boundary migration.Aluminum–brass composite is produced by ARB process up to nine passes. Recrystallization and formation of new grains start from the 3rd pass and continues to the 7th pass. Intensity of the textures decreases after recrystallization; Dillamore and Copper components are the main textures of the composite.
      PubDate: 2017-11-17T02:31:33.642186-05:
      DOI: 10.1002/adem.201700463
       
  • An Evaporative Initiated Chemical Vapor Deposition Coater for Nanoglue
           Bonding
    • Authors: Greg C. Randall; Luis Gonzalez, Ron Petzoldt, Fred Elsner
      Abstract: The authors present an evaporative initiated chemical vapor deposition (iCVD) coater and use it to establish a submicron bonding process for millimeter-scale foils with potentially rough surface features. The coater uses a simple benchtop design suited to research labs, with pre-heated metal pins instead of hot filaments, and direct evaporation of reactants within the chamber. Coatings of poly(glycidyl methacrylate) (pGMA) with thickness 100–800 nm are achieved at rates of 10–40 nm min−1 on substrates common in high energy laser compression experiments. Coating uniformities of 10–30 nm mm−1 are demonstrated in a ≈60 × 10 mm zone under the heated pins. As an aside, the authors further show the ability to coat intentionally non-uniform layers in a monomer vapor diffusion gradient. Coatings are formed on both plastics and solids ranging from smooth, non-burred silicon or lithium fluoride to rough and burred metals (aluminum and copper). These coated substrates are then chemically bonded under mild heat and pressure. Detailed surface, thickness, and cross-sectional characterization is performed to confirm a submicron bond gap and to troubleshoot the common clearance issues from burrs, roughness, and surface curvature. Peeling and dropping bond strength tests confirm the bonds are robust, when coated and assembled under conditions to mitigate clearance issues.A simplified evaporative initiated chemical vapor deposition (iCVD) coater is developed for submicron bond gaps in materials with potentially imperfect surfaces. A robust bonding process is designed to overcome the most common irregular surface features (curvature, roughness, and burrs) followed from contact elasticity analysis. Bond gaps of 0.2–1.5 µm are achieved in combinations of common plastics, metals, and ceramic-like foils.
      PubDate: 2017-11-16T10:00:30.304446-05:
      DOI: 10.1002/adem.201700839
       
  • Nanometer-Thick Ionic Liquids as Boundary Lubricants
    • Authors: Xiao Gong; Lei Li
      Abstract: Ionic liquids (ILs) are fascinating materials with unique combination of solid and liquid properties. Due to high thermal stability and promising tribological properties, there have been increasing research interests in applying ILs as boundary lubricants. In this review, the authors will discuss the recent progress on this topic with the emphasis on the relationship between the molecular arrangement of ILs confined to a solid and the tribological properties. First, the fundamentals on boundary lubrication and the state-of-the-art lubricants will be reviewed briefly. Second, the progress on the molecular structure of ILs confined to a solid surface will be discussed. Afterward, the experimental and computational efforts on the ILs as boundary lubricants will be discussed in details with emphasis on the effect of IL structure, solid substrates, and IL-soild interaction. Finally, the future research directions will be discussed.Ionic liquids (ILs) are fascinating materials with unique combination of solid and liquid properties. In this review, we discuss the recent progress on their potential application as boundary lubricants with the emphasis on the relationship between the molecular arrangement of ILs confined to a solid and the tribological properties.
      PubDate: 2017-11-15T11:58:30.954432-05:
      DOI: 10.1002/adem.201700617
       
  • Diversity in Addressing Reaction Mechanisms of Nano-Thermite Composites
           with a Layer by Layer Structure
    • Authors: Hongtao Sui; Lauren LeSergent, John Z. Wen
      Abstract: The reaction mechanisms and microstructures of various layered nano-thermite composites are investigated through characterization of their energetic properties. Migration of reactive components across the reaction zone is analyzed, which plays an important role in determining the process initiation, reaction propagation, and chemical stability at low temperatures. Distinct types of nanoparticles are deposited onto filter paper in a sequence, using the vacuum filtration method, which promotes intimate contact between neighboring reactive layers. Scanning Electron Microscopy (SEM) images demonstrate a well-defined contact region between the two layers in the Al/CuO or Al/NiO composites. Differential Scanning Calorimetry (DSC) data shows that the thermite reaction occurs below the melting temperature of Al, resulting in rapid heat release, and improves reaction initiation. Elemental mapping results reveal the migration of Al, Ni/Cu, and oxygen before and after the thermite reaction, which is arranged during thermogravimetric analysis (TGA). This analysis indicates the dominant pathway of the thermite reaction in each composite, through either decomposition of the CuO nanoparticles in the Al/CuO composite or through direct migration of reactive components across the conducting surface within the Al/NiO composite.Layer-by-layer structured Al–CuO and Al–NiO nanoparticles are investigated via characterization of their microstructures and elemental mapping. Experimental data indicates for Al–CuO the reaction involves decomposition of CuO into oxygen, while for Al–NiO migration of reactive species across the conducting surface is critical.
      PubDate: 2017-11-15T11:57:02.787975-05:
      DOI: 10.1002/adem.201700822
       
  • 3D Printing of Diamond Tools for Dental Ceramics Processing
    • Authors: Zhibo Yang; Junchen Hu, Kaiqiang Li, Aiju Liu, Shian Liu
      Abstract: This paper is focused on preparing diamond tools with orderly arranged abrasive particles for dental ceramics processing via 3D printing. This allows one to overcome such drawbacks of the existing methods of dental ceramics processing as weak bonding strength, short service life, and irregular diamond distribution in diamond tools. Firstly, the CAD model of the dental diamond tool is constructed using 3D cartographic software, with level-scan-path geometry information generated via hierarchcal slicing. Then, using Ni–Cr alloy powder and diamond as raw materials, the dental ceramics processing diamond tool with orderly arranged diamond particles is prepared via a 3D printer. Next, an X-ray diffractometer, energy dispersive spectrometer, and scanning electron microscope are used to analyze the microstructure of the Ni–Cr alloy and diamond particle interfaces, resulting in the identification of their bonding mechanism. Finally, the diamond grinding wheel produced by 3D printing is subjected to dental zirconia ceramics grinding performance tests. The results obtained confirm that diamond particles experience normal wear, while no abrasive falling off occurs on the 3D printed diamond tool surface.In this paper, diamond tools for dental ceramics processing are manufactured using the 3D printing technology. Laser fast scanning is utilized to make the 3D distribution of diamond particles more regular, thus, significantly improving the manufacturing performance of grinding wheels.
      PubDate: 2017-11-15T11:56:27.324339-05:
      DOI: 10.1002/adem.201700747
       
  • Smart Energetics: Sensitization of the Aluminum-Fluoropolymer Reactive
           System
    • 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
       
  • Impact of Cement Hydration on Durability of Cellulosic Fiber-Reinforced
           Cementitious Composites in the Presence of Metakaolin
    • Authors: Jianqiang Wei
      Abstract: Degradation of cellulosic fiber in the alkaline environment of concrete generated in the process of cement hydration is the primary reason for the low durability of such composites. However, the impact of cement hydration on cellulosic fiber's degradation in cementitious systems has not been thoroughly understood. This paper presents the dependence of deterioration behavior of cellulosic fiber-cement systems on cement hydration in the presence of metakaolin. Experimental investigations, such as isothermal calorimetry, thermogravimetric analysis and energy dispersive X-ray spectroscopy, and thermodynamic simulations are carried out to investigate cement hydration kinetics and hydration products. Durability of cellulosic fiber-reinforced cement composite is assessed based on the degradation in flexural properties. The results indicate that, in the presence of metakaolin, the hydration of cement is enhanced accompanied by consumption of calcium hydroxide, low release of hydration heat, decreased Ca/Al and Ca/Si ratios of C–S–H phase, and reduced OH- and Ca2+ amounts in pore solution. A cement substitution by 30 wt% metakaolin results in an improvement of flexural toughness and durability of cellulosic fiber-reinforced cement composites by 42 and 269%, respectively. The correlations between composite durability and hydration of Portland cement are established.Hydration of cement is identified as a crucial factor in understanding the deterioration behavior of cellulosic fibers-reinforced cementitious composites. Effect of metakaolin, on durability of cellulosic fiber-reinforced cement composites are evaluated by means of degradation in flexural properties. Based on the experimental and simulation observations, correlations between durability of cellulosic fiber-cement system and cement chemistry are established.
      PubDate: 2017-11-14T02:27:19.086803-05:
      DOI: 10.1002/adem.201700642
       
  • Production and Anisotropic Tensile Behavior of Resin-Metal
           Interpenetrating Phase Composites
    • Authors: Bibo Yao; Zhaoyao Zhou, Liuyang Duan, Jie Qin
      Abstract: Metal-polymer composites can be used to synthesize material properties. A variety of interpenetrating phase composites have been produced by spontaneously infiltrating porous short-fiber preforms with unsaturated polyester resin under vacuum conditions. Porous preforms are fabricated by compacting and sintering short 304 stainless steel fibers from cutting stainless steel fiber ropes. Tensile experiments are conducted, and fractographs are examined via scanning electron microscopy. The results reveal that the tensile strength, elongation at maximum stress, and elasticity modulus of the IPCs increase with the increasing fiber fractions and exhibit anisotropy in different directions. The tensile strength and elongation at maximum stress are significantly improved compared with the consistent preforms. A nonlinear elastic behavior and sawtooth-like fluctuation during yield deformation are noted. Compared with the through-thickness direction, a higher tensile strength and larger elongation at maximum stress are observed in the in-plane direction. Finer-diameter fibers can improve the strength and increase the elongation at maximum stress. The tensile fracture surfaces show a mixture of brittle and plastic fracture characteristics.Metal-resin IPCs are produced by vacuum-infiltration of unsaturated polyester resin into the stainless steel preforms and their tensile properties are analyzed. The tensile strength and elongation at maximum stress increase with the increasing fiber fractions and exhibit anisotropy. Finer diameter fibers can improve the strength and increase the elongation at maximum stress. The tensile fracture surfaces show a mixture of brittle and plastic fracture characterizations.
      PubDate: 2017-11-14T02:25:36.705722-05:
      DOI: 10.1002/adem.201700669
       
  • 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
       
  • Microstructure-Dependent Local Fatigue Cracking Resistance of Bimodal
           Ti–6Al–4V Alloys
    • Authors: Ling-Rong Zeng; Li-Ming Lei, Jia Yang, Xue-Mei Luo, Guang-Ping Zhang
      Abstract: The fatigue crack growth behavior of the bimodal Ti–6Al–4V alloys with two different volume fractions of the primary α phase (αp) of 76 and 36% is investigated by the in situ testing technique. The experimental results show that the crack growth rate of the αp = 36% Ti–6Al–4V alloy is lower than that of the αp = 76% one. The local fatigue crack growth rate is evidently decreased by the various boundaries including αp grain boundaries, boundaries between the αp phase and basketweave microstructure, and α/β lamellar interfaces. A criterion associated with the boundary characteristics is obtained to evaluate the grain boundary resistance to the fatigue crack growth in the engineering alloys.Local crack growth rate and fatigue cracking resistance of the Ti–6Al–4V alloys with different volume fractions of primary α phases are investigated in situ in SEM. Local resistance to fatigue cracking related to the boundary characteristics is evaluated quantitatively by EBSD. A criterion for the grain boundary resistance to the crack growth is proposed.
      PubDate: 2017-11-13T03:15:37.565735-05:
      DOI: 10.1002/adem.201700702
       
  • Influence of Ingot and Powder Metallurgy Production Route on the Tensile
           Creep Behavior of Mo–9Si–8B Alloys with Additions of Al and Ge
    • Authors: P. M. Kellner; R. Völkl, U. Glatzel
      Abstract: Refractory metals and their alloys show potential for high temperature applications, due to the elevated melting points often paired with very good creep resistance. Spark plasma sintering (SPS) as well as arc-melting is used here to prepare quaternary and quinternary Mo–9Si–8B–xAl–yGe (x is 0 or 2; y is 0 or 2, all numbers in at%) samples. All samples consist of a Mo solid solution (Moss) and two intermetallic phases: Mo3Si (A15) and Mo5SiB2 (T2). Aluminum and germanium reduce the melting point and slightly decrease the density of the material. The specimens are homogenized and coarsened by a subsequent heat-treatment in vacuum at 1850 °C for 24 h. The resulting microstructure is investigated using scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and inductively coupled plasma optical emission spectrometry (ICP-OES) analysis. A vacuum creep testing device for small tensile creep specimens is presented. It is heated by graphite radiation heaters usable up to 1500 °C in vacuum of 2 · 10-4 Pa with an oil diffusion pump. Tensile creep tests are performed at 1250 °C and stresses from 50 MPa up to 250 MPa. Specimens produced by ingot metallurgy feature superior creep properties compared to powder metallurgy samples.In this study, tensile creep tests are performed for Mo–Si–B alloys at 1250 °C and stresses from 50 to 250 MPa manufactured by argon arc melting and powder metallurgy. Specimens produced by argon arc melted feature superior creep properties compared to powder metallurgy ones, due to grain size.
      PubDate: 2017-11-13T02:46:55.570691-05:
      DOI: 10.1002/adem.201700751
       
  • Macroporous SiOC Ceramics with Dense Struts by Positive Sponge Replication
           Technique
    • Authors: Abhisek Choudhary; Swadesh K. Pratihar, Ashish K. Agrawal, Shantanu K. Behera
      Abstract: Highly porous SiOC ceramics (≥90% open porosity) containing dense struts have been prepared following positive sponge replication technique using silsesquioxane based preceramic polymer. The morphological features including cell size, cell window size, and strut size of the macroporous SiOC ceramics have been analyzed using electron microscopy. Subtle variation in the crosslinking condition of the preceramic polymer infiltrated polyurethane template enables the formation of hollow as well as dense struts, which has a profound influence on compressive strength of the macroporous bodies. Synchrotron radiation micro computed tomography is used to construct the three dimensional images of the macroporous ceramics that indicate isotropy of the pores and excellent interconnectivity.Control of slurry viscosity and crosslinking temperature in the processing of preceramic polymer infiltrated PU sponge affords macroporous SiOC ceramics with 90% open porosity, dense struts, and excellent mechanical strength. Synchrotron X-ray microtomography exhibits excellent interconnectivity, homogeneity, and isotropy of the pores.
      PubDate: 2017-11-09T12:02:36.46478-05:0
      DOI: 10.1002/adem.201700586
       
  • Key Factors Achieving Large Recovery Strains in Polycrystalline
           Fe–Mn–Si-Based Shape Memory Alloys: A Review
    • Authors: Huabei Peng; Jie Chen, Yongning Wang, Yuhua Wen
      Abstract: Fe–Mn–Si-based shape memory alloys are the most favorable for large-scale applications owing to low cost, good workability, good machinability, and good weldability. However, polycrystalline Fe–Mn–Si-based shape memory alloys have low recovery strains of only 2–3% after solution treatment, although monocrystalline ones reach a large recovery strain of ≈9%. This review gives an overview of the improvement of recovery strains for polycrystalline Fe–Mn–Si-based shape memory alloys. It is proposed that two fundamental aspects, that is, composition design and microstructure design, shall be satisfied for obtaining large recovery strains of above 6%. Alloying compositions determining the ceiling of recovery strains shall follow three guidelines: (i) Si content is 5–6 wt%; (ii) 20 wt% ≤ Mn ≤ 32 wt%; (iii) addition of elements strongly strengthening austenite matrix. Microstructure design includes coarsening austenitic grains and reducing twin boundaries as far as possible together with introducing a high density of stacking faults and second phases of strengthening austenite.Low cost Fe–Mn–Si-based shape memory alloys are suitable for large-scale applications. However, their recovery strains are only 2–3% in solution-treated polycrystalline status. This review summarizes the origin of shape memory effect and the improvement history of recovery strains. It is concluded that two fundamental aspects, that is, composition design and microstructure design, shall be followed to achieve a large recovery strain of above 6%.
      PubDate: 2017-11-09T11:56:27.165908-05:
      DOI: 10.1002/adem.201700741
       
  • Mechanical Properties and Interlaminar Fracture Toughness of
           Glass-Fiber-Reinforced Epoxy Composites Embedded with Shape Memory Alloy
           Wires
    • Authors: Li-Dan Xu; Ming-Fang Shi, Xiao-Yu Sun, Zhen-Qing Wang, Bin Yang
      Abstract: The effects of the content and position of shape memory alloy (SMA) wires on the mechanical properties and interlaminar fracture toughness of glass-fiber-reinforced epoxy (GF/epoxy) composite laminates are investigated. For this purpose, varying numbers of SMA wires are embedded in GF/epoxy composite laminates in different stacking sequences. The specimens are prepared by vacuum-assisted resin infusion (VARI) processing and are subjected to static tensile and three-point-bending tests. The results show that specimens with two SMA wires in the stacking sequence of [GF2/SMA/GF1/SMA/GF2] and four SMA wires in the stacking sequence of [GF4/SMA/GF2/SMA/GF4] exhibit optimal performance. The flexural strength of the optimal four-SMA-wire composite is lower than that of the pure GF/epoxy composite by 5.76% on average, and the flexural modulus is improved by 5.19%. Mode-I and II interlaminar fracture toughness tests using the SMA/GF/epoxy composite laminates in the stacking sequence of [GF4/SMA/GF2/SMA/GF4] are conducted to evaluate the mechanism responsible for decreasing the mechanical properties. Scanning electron microscopy (SEM) observations reveal that the main damage modes are matrix delamination, interfacial debonding, and fiber pullout.The effects of the content and position of shape memory alloy (SMA) wires on the mechanical properties and interlaminar fracture toughness of glass-fiber-reinforced epoxy (GF/epoxy) composite laminates are investigated. The main damage modes are studied by Scanning electron microscopy (SEM).
      PubDate: 2017-11-09T11:55:52.804025-05:
      DOI: 10.1002/adem.201700646
       
  • Stress Reduction of 3D Printed Compliance-Tailored Multilayers
    • Authors: Shanmugam Kumar; Brian L. Wardle, Muhamad F. Arif, Jabir Ubaid
      Abstract: Multilayered multi-material interfaces are encountered in an array of fields. Here, enhanced mechanical performance of such multi-material interfaces is demonstrated, focusing on strength and stiffness, by employing bondlayers with spatially-tuned elastic properties realized via 3D printing. Compliance of the bondlayer is varied along the bondlength with increased compliance at the ends to relieve stress concentrations. Experimental testing to failure of a tri-layered assembly in a single-lap joint configuration, including optical strain mapping, reveals that the stress and strain redistribution of the compliance-tailored bondlayer increases strength by 100% and toughness by 60%, compared to a constant modulus bondlayer, while maintaining the stiffness of the joint with the homogeneous stiff bondlayer. Analyses show that the stress concentrations for both peel and shear stress in the bondlayer have a global minimum when the compliant bond at the lap end comprises ≈10% of the bondlength, and further that increased multilayer performance also holds for long (relative to critical shear transfer length) bondlengths. Damage and failure resistance of multi-material interfaces can be improved substantially via the compliance-tailoring demonstrated here, with immediate relevance in additive manufacturing joining applications, and shows promise for generalized joining applications including adhesive bonding.By crafting a spatially compliance-tailored bondlayer utilizing additive manufacturing, mechanical performance can be increased significantly compared to the homogeneous stiff or compliant bondlayer, imparting greater strength, strain to break, and toughness, while maintaining stiffness of the homogeneous stiff bondlayer.
      PubDate: 2017-11-08T08:15:47.562197-05:
      DOI: 10.1002/adem.201700883
       
  • Effect of Laser Shock Peening on the Microstructures and Properties of
           Oxide-Dispersion-Strengthened Austenitic Steels
    • Authors: Xueliang Yan; Fei Wang, Leimin Deng, Chenfei Zhang, Yongfeng Lu, Michael Nastasi, Marquis A. Kirk, Meimei Li, Bai Cui
      Abstract: Oxide-dispersion-strengthened (ODS) austenitic steels are promising materials for next-generation fossil and nuclear energy systems. In this study, laser shock peening (LSP) has been applied to ODS 304 austenitic steels, during which a high density of dislocations, stacking faults, and deformation twins are generated in the near surface of the material due to the interaction of laser-driven shock waves and the austenitic steel matrix. The dispersion particles impede the propagation of dislocations. The compressive residual stress generated by LSP increases with successive LSP scans and decreases along the depth, with a maximum value of −369 MPa. The hardness on the surface can be improved by 12% using LSP. In situ transmission electron microscopy (TEM) irradiation studies reveal that dislocations and incoherent twin boundaries induced by LSP serve as effective sinks to annihilate irradiation defects. These findings suggest that LSP can improve the mechanical properties and irradiation resistance of ODS austenitic steels in nuclear reactor environments.Laser shock peening (LSP) has been applied to oxide-dispersion-strengthened (ODS) austenitic steels in order to improve the mechanical properties and irradiation resistance. Significant plastic deformation and compressive residual stress are generated by LSP in the near surface, improving the hardness. Dislocations and incoherent twin boundaries induced by LSP can serve as effective sinks to annihilate irradiation defects.
      PubDate: 2017-11-07T11:46:29.396414-05:
      DOI: 10.1002/adem.201700641
       
  • Effect of High-Energy Ball Milling on Mechanical Properties of the Mg–Nb
           Composites Fabricated through Powder Metallurgy Process
    • Authors: Alireza Vahid; Peter Hodgson, Yuncang Li
      Abstract: New biocompatible and biodegradable Mg–Nb composites used as bone implant materials are fabricated through powder metallurgy process. Mg–Nb mixture powders are prepared through mechanical milling and manual mixing. Then, the Mg–Nb composites are fabricated through cold press and sintering processes. The effect of mechanical milling and Nb particles as reinforcements on the microstructures and mechanical properties of Mg–Nb composites are investigated. The mechanical milling process is found to be effective in reducing the size of Mg and Nb particles, distributing the Nb particles uniformly in the Mg matrix and obtaining Mg–Nb composite particles. The Mg–Nb composite particles can be bound together firmly during the sintering process, result in Mg–Nb composite structures with no intermetallic formation, lower porosity, and higher mechanical properties compared to composites prepared through manual mixing. Interestingly, the mechanical properties of manually mixed Mg–Nb composites appear to be even lower than that of pure Mg.New biodegradable Mg–Nb composites are fabricated through powder metallurgy process. The effect of mechanical milling and Nb particles as reinforcements on the microstructures and mechanical properties of the composites are investigated. The mechanical milling reduces the size of Mg and Nb particles and distributes the Nb particles uniformly in the Mg matrix, produces composites with low porosity and high mechanical properties.
      PubDate: 2017-11-06T04:27:47.527067-05:
      DOI: 10.1002/adem.201700759
       
  • Vibration Damping of Carbon Nanotube Assembly Materials
    • Authors: Jingna Zhao; Fulin Wang, Xin Zhang, Linjie Liang, Xueqin Yang, Qingwen Li, Xiaohua Zhang
      Abstract: Vibration reduction is of great importance in various engineering applications, and a material that exhibits good vibration damping along with high strength and modulus has become more and more vital. Owing to the superior mechanical property of carbon nanotube (CNT), new types of vibration damping material can be developed. This paper presents recent advancements, including our progresses, in the development of high-damping macroscopic CNT assembly materials, such as forests, gels, films, and fibers. In these assemblies, structural deformation of CNTs, zipping and unzipping at CNT connection nodes, strengthening and welding of the nodes, and sliding between CNTs or CNT bundles are playing important roles in determining the viscoelasticity, and elasticity as well. Toward the damping enhancement, strategies for micro-structure and interface design are also discussed.Carbon nanotube (CNT) assembly materials are superior vibration damping materials, with performance better than conventional metal and polymer materials. The interface engineering between CNTs and at CNT connection nodes is the key to tune the damping performance. This review addresses the recent progresses on the vibrational properties of CNT forests, gels, films, and fibers.
      PubDate: 2017-11-06T04:26:51.449241-05:
      DOI: 10.1002/adem.201700647
       
  • Microstructure and Tribological Behavior of Stripe Patterned TiN Film
           Prepared with Filtered Cathodic Vacuum Arc Deposition (FCVAD)
    • Authors: Ping Chen; Yingqian La
      Abstract: This paper describes an experimental investigation into the influence of the stripe interspace and applied load on the tribological behavior of stripe patterned TiN films. The stripe patterned TiN films are deposited on an H13 steel surface by masked deposition with the filtered cathodic vacuum arc discharge (FCVAD) technique. The surface micro morphology, chemical composition, crystal structure, and mechanical properties of the films is characterized using 3D white light interferometry, scanning electron microscopy (SEM), X-ray diffractometry (XRD), and a nano-indentation tester, respectively. The tribological performance of patterned TiN is measured using a UMT-5 tribometer, and the friction and wear mechanisms are analyzed, compared with that of the full TiN film and H13 steel substrate. The results show that the stripe patterned TiN films has better tribological properties than the full TiN film. These results are attributed to the synergistic effect between the surface pattern and the TiN film. The stripe interspace and the applied load has a more significant effect on the wear rate of the stripe patterned TiN films than the coefficient of friction of their friction pairs. A further study, however, is needed to analyze the relationship between the applied load and the wear rates of the stripe patterned TiN films.This paper describes an experimental investigation into the influence of the stripe interspace and applied load on the tribological behavior of stripe patterned TiN films. The stripe patterned TiN films are prepared by masked deposition using filtered cathodic vacuum arc discharge technique.
      PubDate: 2017-11-02T08:51:05.514755-05:
      DOI: 10.1002/adem.201700700
       
  • Compositional and Tribo-Mechanical Characterization of Ti-Ta Coatings
           Prepared by Confocal Dual Magnetron Co-Sputtering
    • Authors: Amin Bahrami; Jonatán Pérez Álvarez, Osmary Depablos-Rivera, Roberto Mirabal-Rojas, Agustin Ruíz-Ramírez, Stephen Muhl, Sandra E. Rodil
      Abstract: Titanium-Tantalum coatings are deposited by magnetron co-sputtering technique, using independently driven titanium and tantalum targets. The effect of the Ta content on the structure, mechanical, and wear properties of Ti films is investigated. It is found that the percentage of the added Ta varies linearly from 3.7 to 31.3 at% by increasing the power applied to the Ta target from 10 to 100 W. The XRD results show that the coatings are crystalline, and there is no evidence of the formation of intermetallic phases, instead formation of metastable phases of α″ and β depending on Ta content are observed, though the samples are deposited at low temperature (150 °C). It is shown that the elastic strain to failure (H/Er; hardness to reduced elastic moduli ratio) can be increased by 40% through the formation of crystalline phases with a lower E, while the hardness remains constant. The tribological study shows that increasing the Ta content up to 14.9 at% causes a significant improvement in adhesion of the coating to a soft metallic substrate.The production of nanostructured, hard, and tough metallic coatings using vapor deposition method is of increasing interests in the coating of metallic substrates. The results in this study show that addition of Ta to the Ti coatings improves the toughness and adhesion of coatings to the substrate, although it has not significant effect on the hardness of coatings.
      PubDate: 2017-11-02T04:05:58.465537-05:
      DOI: 10.1002/adem.201700687
       
  • Directly Verifiable Neutron Diffraction Technique to Determine Retained
           Austenite in Steel
    • Authors: Tatiana Lychagina; Alexander Zisman, Ekaterina Yashina, Dmitry Nikolayev
      Abstract: Conventional procedures for quantitative analysis of retained austenite in steels by neutron diffraction ignore the effect of crystallographic texture and rely on a-priori parameters rather than a direct calibration with appropriate etalons. As the main drawback, this method is not directly verified by independent data. In order to get over the verification problem, that is, to calibrate the method, reference sandwich-like samples with predefined amounts of austenite have been prepared. Neutron diffraction allows to measure large samples from one hand and to get rid of the texture influence from the other. Application of the proposed method was illustrated by volume fractions of retained austenite determination in medium-carbon martensitic steel tempered at various temperatures. Main result of our work is the developed method based on complete orientation averaging by means of neutron diffraction and usage of the calibration samples. It allowed to refine the austenite detectability limit to about 0.1% (vol.). Based on the method calibration, low fractions of retained austenite (0.13–2.9%) have been determined in the medium-carbon martensitic steel tempered at various temperatures.The new method of the quantitative analysis for retained austenite in steels by neutron diffraction is proposed. This approach is based on the calibration with reference samples in order to reliably evaluate low fractions of retained austenite in textured steels with detectability limit refined to 0.1%. The suggested method implies direct verification of the results.
      PubDate: 2017-10-30T07:41:46.467493-05:
      DOI: 10.1002/adem.201700559
       
  • 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
       
  • Experimental Study on the Effect of Cooling Rate on the Secondary Phase in
           As-Cast Mg–Gd–Y–Zr Alloy
    • Authors: Keyan Wu; Xuyang Wang, Lv Xiao, Zhongquan Li, Zhiqiang Han
      Abstract: The effect of cooling rate on the composition, morphology, size, and volume fraction of the secondary phase in as-cast Mg–Gd–Y–Zr alloy is investigated. In the study, a casting containing five steps with thickness of 10–50 mm is produced, in which cooling rate ranging from 2.6 to 11.0 K s−1 is created. The secondary phase is characterized using optical microscope (OM), scanning electron microscope (SEM), and electron probe micro-analyzer (EPMA). The volume fraction of the secondary phase is determined using OM and quantitative metallographic analysis, and Vickers hardness test is conducted to verify the analysis results. The effect of the cooling rate on the volume fraction of the secondary phase is discussed in detail. The result shows that with the increase of the cooling rate, the size of the secondary phase decreases. The effect of the cooling rate on the volume fraction of the secondary phase is complicated somewhat. A comprehensive analysis on the experimental data shows that a critical cooling rate may exist, over which the volume fraction of the secondary phase decreases with the increase of the cooling rate, however under which the volume fraction increases with the increase of the cooling rate.The effect of cooling rate on the composition, morphology, size, and volume fraction of the secondary phase in as-cast Mg–Gd–Y–Zr alloy is investigated. The mechanisms governing the variation of the volume fraction of the secondary phase with cooling rates are revealed.
      PubDate: 2017-10-30T01:41:32.854279-05:
      DOI: 10.1002/adem.201700717
       
  • Friction Reduction Induced by Elliptical Surface Patterns under Lubricated
           Conditions
    • Authors: Andreas Rosenkranz; Adam Szurdak, Philipp G. Grützmacher, Gerhard Hirt, Frank Mücklich
      Abstract: Recording Stribeck-like curves is an efficient way to evaluate the frictional performance and efficiency of patterned surfaces. Elliptical patterns with varying area density and structural depth are fabricated by micro-coining on steel substrates (AISI 304). A ball-on-disc tribometer is used to perform unidirectional sliding experiments for the polished reference and the elliptical patterns dependent on the sliding velocity. In this study, a clear connection between structural parameters such as length of long and short axis, aspect ratio, and pitch with the frictional behavior can be found. Comparing patterns with comparable depth and area density underlines that elliptical patterns having larger individual features (increased length of both axes) separated by a larger pitch reduce the COF more significantly. The number of tribologically active individual elliptical structures, recirculation effects of the lubricant, as well as the pattern geometry that may lead to undesired edge effects and stress concentrations need to be taken into consideration to explain those findings. The sample with the smallest structural depth, the smallest area density, and the lowest aspect ratio (A1) leads to the maximum friction reduction (4-fold) for all velocities which underlines the enormous potential of elliptical structures in terms of friction reduction.The frictional performance of elliptical surface patterns fabricated by hot micro-coining is investigated by recording Stribeck-like curves. The sample with the smallest structural depth, the smallest area density, and the lowest aspect ratio lead to the maximum friction reduction by a factor of 4, which underlines the enormous potential of elliptical structures in terms of friction reduction.
      PubDate: 2017-10-25T09:55:36.549437-05:
      DOI: 10.1002/adem.201700731
       
  • Graphene Oxide/Polymer-Based Biomaterials
    • Authors: Duygu Ege; Ali Reza Kamali, Aldo R. Boccaccini
      Abstract: Since its discovery in 2004, derivatives of graphene have been developed and heavily investigated in the field of tissue engineering. Among the most extensively studied forms of graphene, graphene oxide (GO), and GO/polymer-based nanocomposites have attracted great attention in various forms such as films, 3D porous scaffolds, electrospun mats, hydrogels, and nacre-like structures. In this review, the most actively investigated GO/polymer nanocomposites are presented and discussed, these nanocomposites are based on chitosan, cellulose, starch, alginate, gellan gum, poly(vinyl alcohol) (PVA), poly(acrylamide), poly(ϵ-caprolactone) (PCL), poly(lactic acid) (PLLA), poly(lactide-co-glycolide) (PLGA), gelatin, collagen, and silk fibroin (SF). The biological and mechanical performance of such nanocomposites are comprehensively scrutinized and ongoing research questions are addressed. The analysis of the literature reveals overall the great potential of GO/polymer nanocomposites in tissue engineering strategies and indicates also a series of challenges requiring further research efforts.In this review paper, the mechanical and biological performance of graphene oxide/polymeric nanocomposites are analyzed in detail and discussed. Additionally, useful graphics are provided which lead researchers to compare the mechanical properties of films, electrospun mats, fibers, nacre-like structures, and hydrogels of graphene oxide/polymeric nanocomposites at first glance. Finally, the potential of these nanocomposites in tissue engineering are reported with suggestions for future research.
      PubDate: 2017-09-14T07:41:13.801311-05:
      DOI: 10.1002/adem.201700627
       
  • Microstructures and Tensile Properties of AZ91 Magnesium Alloys with Ca,
           Sm, and La Elements Additions
    • Authors: Li Fu; Xi Bo Wang, Pei Li Gou, Qi Chi Le, Wei Tao Jia, Yan Tang
      Abstract: Microstructures and tensile properties of as-cast and as-extruded AZ91 magnesium alloys with individual and combined additions of Ca, Sm, and La elements are investigated. The results show that Al2Ca, Al2Sm, and Al11La3 new phases form after adding Ca, Sm, La elements, decreasing the amount of Mg17Al12 phases and refining the microstructures. Microstructures of as-cast and as-extruded alloys with combined additions are significant refined. The Al2Ca and Al11La3 intermetallic compounds are crushed into granules because of severe deformation during hot extrusion, while the Al2Sm intermetallic compounds are not. Tensile tests results at room temperature indicate that individual additions of Ca, Sm, and La elements could increase the elongation of as-extruded alloys, and tensile tests results at 150 °C indicate that individual additions of Sm and La elements could increase the ultimate tensile strength and yield strength of as-extruded alloys. AZ91–0.3La alloy exhibits the best comprehensive tensile properties both at room temperature and 150 °C. However, combined additions in AZ91 alloys leads to coarseness and aggregation of Al2Sm phases, resulting in slightly decline of tensile properties both at room temperature and 150 °C.As-cast and as-extruded AZ91 alloys with additions of Ca, Sm, La elements are investigated to determine formation process of new phases, refinement in microstructures and improvement in tensile properties by analyzing the XRD patterns, optical metallurgical images, SEM images, and results of tensile tests both at room temperature and 150 °C. The refinement mechanisms in microstructure and tensile properties of these alloys after adding Ca, Sm, La elements are also discussed.
      PubDate: 2017-08-29T03:10:50.700461-05:
      DOI: 10.1002/adem.201700230
       
  • A Triboelectric Self-Powered Sensor for Tire Condition Monitoring:
           Concept, Design, Fabrication, and Experiments
    • Authors: Hassan Askari; Zia Saadatnia, Amir Khajepour, Mir Behrad Khamesee, Jean Zu
      Abstract: This paper presents a novel type of triboelectric-based self-powered sensor for tire condition monitoring. The triboelectric based sensor is made of highly flexible, mechanically and thermally durable, and cost-effective polymeric materials. The authors firstly report the location inside of a tire for attaching the sensor to monitor tire conditions. Then, the authors analyze the performance of the sensor under different frequencies and stroke displacements to show the capability of the fabricated device as a self-powered sensor. Furthermore, the authors evaluate the durability and performance of the sensor to delineate its potential for tire condition monitoring. The results show that the fabricated self-powered sensor has the potential of measuring the tire forces and pressure. The use of the proposed sensor for tire condition monitoring systems (TCMS) can be considered as a significant step toward developing smart tires, improving vehicles control strategy, and accordingly, enhancing passengers safety.Triboelectric Nano Generator for Tire Condition Monitoring: As the figure shows, with attaching a new sensory device to a tire, we can obtain crucial information pertinent to its dynamics. The use of the proposed sensor for tire condition monitoring systems (TCMS) is a significant step toward developing smart tires, improving vehicles control strategy, and accordingly, enhancing passengers safety and reduction of disastrous accidents.
      PubDate: 2017-08-24T13:10:27.538505-05:
      DOI: 10.1002/adem.201700318
       
  • Small Y Addition Effects on Hot Deformation Behavior of Copper-Matrix
           Alloys
    • Authors: Yi Zhang; Huili Sun, Alex A. Volinsky, Bingjie Wang, Baohong Tian, Zhe Chai, Yong Liu, Kexing Song
      Abstract: Hot deformation behavior of two alloys, Cu–Zr and Cu–Zr–Y is studied by compression tests using the Gleeble-1500D thermo-mechanical simulator. Experiments are conducted at 550–900 °C temperature and 0.001–10 s−1 strain rate. The true stress–true strain curves are analyzed, and the results show that the flow stress strongly depends on the temperature and the strain rate. Furthermore, both alloys behave similarly when the flow stress increases with higher strain rate and lower temperature. Based on the dynamic material model, the processing maps are obtained at strains of 0.4 and 0.5. The optimal processing parameters for the Cu–Zr and Cu–Zr–Y alloys are determined. In addition, the constitutive equations for the alloys are established to characterize the flow stress as a function of strain rate and deformation temperature. Based on the microstructure evolution analysis, the results show that the addition of Y can effectively promote dynamic recrystallization. Moreover, the processability of the alloy can be optimized. Thermal deformation activation energy and the peak power dissipation efficiency for the alloys are obtained. It is observed that the addition of Y effectively improves thermal deformation activation energy and has considerable influence on the peak power dissipation efficiency.The addition of Y to the Cu–Zr alloy effectively promotes dynamic recrystallization and improves thermal deformation activation energy, having a considerable influence on the peak power dissipation efficiency.
      PubDate: 2017-08-14T01:51:17.283951-05:
      DOI: 10.1002/adem.201700197
       
  • Indentation Response and Structure-Property Correlation in a Bimodal
           Ti–6Al–4V Alloy
    • Authors: Indrani Sen; Shibayan Roy, Martin F.-X. Wagner
      Abstract: Understanding the deformation behavior of multi-phase alloys under external loading requires careful mechanical characterization of the individual constituent phases at various length scales. The present study first evaluates the elastic moduli and hardness of the microstructural constituents viz. primary α (αp) and transformed β (secondary α (αs) plus retained prior β) phases in a bimodal Ti–6Al–4V alloy by nano-indentation using different loads. The bulk mechanical properties of the overall microstructure are then determined by grid wise nano-indentation, as well as micro-indentation. The alloy shows a pronounced indentation size effect; the hardness increases with the decrease in indentation load, or depth of penetration. Assuming an iso-stress condition for individual constituents (αp and transformed β) in the rule of mixture approach, the bulk mechanical properties of the Ti–6Al–4V alloy are reasonably predicted. Such prediction of bulk properties, however, is not possible when a similar calculation is performed using iso-strain condition. The transformed β phase shows disparity between the estimated and experimental values, while considering the αs and β phases individually, on both iso-stress and iso-strain assumptions. From these results, the influence of individual microstructural phases (size, distribution, volume fraction, morphology) and the interfaces between them, is found key in controlling the overall bulk mechanical response of the alloy system.The study evaluates mechanical properties of microstructural constituents in a bimodal Ti–6Al–4V alloy by nano- and micro-indentation. The role of size, distribution, morphology, volume fraction, and interfaces of these constituents in controlling the bulk mechanical response is rationalized by a rule of mixture based theoretical calculation.
      PubDate: 2017-08-14T01:50:38.91002-05:0
      DOI: 10.1002/adem.201700298
       
  • Work of Adhesion Measurements of MoS2 Dry Lubricated 440C Stainless Steel
           Tribological Contacts
    • Authors: Simo Pajovic; Guillaume Colas, Aurélien Saulot, Mathieu Renouf, Tobin Filleter
      Abstract: The tribological behavior of dry lubricants depends on their mechanical and physicochemical environment, making it difficult to predict in practice. Discrete Element Method-based modeling has been one successful approach to provide valuable insight into the tribology of dry lubricated contacts. However, it requires well-defined interactions between discrete elements, in particular between those simulating different materials. Measuring the properties governing those interactions, such as the work of adhesion (W), is therefore critical. The present work describes a method for measuring the W between AISI440C steel and MoS2-based coatings used in spacecraft. Using Atomic Force Microscopy local asperity and adhesion measurements, the W between steel microbeads and MoS2 coatings is determined at different stages in its wear life. The distributions of W values in the worn coatings and pristine coatings agree well with earlier Time-of-Flight Secondary Ion Mass Spectroscopy studies on the physicochemistry of the samples, as well as contact angle measurements. Additional measurements between the same materials on a ball bearing from a real life-test unit of a spacecraft instrument also show a similar W distribution, suggesting that the approach used here provides relevant data for use in numerical simulations.The study describes a method for measuring the work of adhesion (W) between AISI440C steel and MoS2-based coatings. After morphological and chemical studies of the surfaces, W is determined at different stages of the coating's wear life by using Atomic Force Microscopy (AFM), local asperity detection, and adhesion measurements with steel microbeads.
      PubDate: 2017-08-10T08:44:24.551971-05:
      DOI: 10.1002/adem.201700423
       
  • Nanoporous Metals with Structural Hierarchy: A Review
    • Authors: Theresa Juarez; Juergen Biener, Jörg Weissmüller, Andrea M. Hodge
      Abstract: Nanoporous (np) metals have generated much interest since they combine several desirable material characteristics, such as high surface area, mechanical size effects, and high conductivity. Most of the research has been focused on np Au due to its relatively straightforward synthesis, chemical stability, and many promising applications in the fields of catalysis and actuation. Other materials, such as np-Cu, Ag, and Pd have also been studied. This review discusses recent advances in the field of np metals, focusing on new research areas that implement and leverage structural hierarchy while using np metals as their base structural constituents. First, we focus on single-element porous metals that are made of np metals at the fundamental level, but synthesized with additional levels of porosity. Second, we discuss the fabrication of composite structures, which use auxiliary materials to enhance the properties of np metals. Important applications of these hierarchical materials, especially in the fields of catalysis and electrochemistry, are also reviewed. Finally, we conclude with a discussion about future opportunities for the advancement and application of np metals.This review discusses developments in the field of nanoporous metals, focusing on research areas that implement and leverage structural hierarchy while using nanoporous metals as the base structural constituents. Fabrication methods for both single elemental materials and composites are reviewed followed by a discussion of emerging applications.
      PubDate: 2017-08-09T06:25:58.3624-05:00
      DOI: 10.1002/adem.201700389
       
  • Enhancing the Strength and Ductility in Mg–Zn–Ce Alloy through
           Achieving High Density Precipitates and Texture Weakening
    • Authors: Yuzhou Du; Mingyi Zheng, Xiaoguang Qiao, Bailing Jiang
      Abstract: The microstructure with weak fiber texture and dense precipitates is designed and produced through extrusion and subsequent ageing treatment of Mg–6Zn–0.2Ce (wt%) alloy. Results show that ageing treatment improves the strength of the as-extruded Mg–6Zn–0.2Ce (wt%) alloy and retains the ductility. The peak-aged alloy exhibits a good combination of strength and ductility, which is superior to the commercial Mg alloy. The yield strength and elongation to fracture of the peak-aged Mg–6Zn–0.2Ce (wt%) alloy are 225 MPa and 32.1%, respectively. The strength improvement of the peak-aged alloy is attributed to dense rod-like precipitates, and the superior ductility is mainly due to weaker texture and homogeneous microstructure.The microstructure with weak fiber texture and dense precipitates is produced through extrusion and subsequent ageing treatment of Mg–6Zn–0.2Ce (wt%) alloy. The peak-aged alloy exhibits a good combination of strength and ductility with the yield strength of 225 MPa and elongation to fracture of 32.1%, which is attributed to dense rod-like precipitates and weaker texture.
      PubDate: 2017-08-08T07:01:55.226185-05:
      DOI: 10.1002/adem.201700487
       
  • Effect of Trace B on the Microstructure and Mechanical Properties of a
           Newly Near α High Temperature Titanium Alloy
    • Authors: Chongxiao Guo; Changjiang Zhang, Jianchao Han, Shuzhi Zhang, Fei Yang, Lihua Chai, Ziyong Chen
      Abstract: In this study, the microstructural evolution and mechanical properties of a newly near α titanium alloy with trace additions of B by in situ casting route are investigated. The results show that the coarse prior β grain and α lath within matrix alloy are gradually refined with increasing of B addition. The relative refinement mechanism of prior β grain and α lath width is analyzed and discussed. In addition, it is shown that both of ultimate compressive strength (UCS) and yield strength (UYS) increase with B addition, which is mainly attributed to microstructural refinement. However, the compressive ductility and fracture toughness decrease with increasing of B addition, which is due to the cracking of TiB, leading to the acceleration of crack extension.A newly near α titanium alloy with trace addition of B are discussed. Necklace-like of TiB locates at the grain boundary of prior β–Ti. According to the solidification path of B-containing alloys, refinement mechanism is elaborated. Ultimate compressive strength and yield strength increase, while the compressive ductility and fracture toughness decrease with B addition.
      PubDate: 2017-08-08T07:01:50.525811-05:
      DOI: 10.1002/adem.201700490
       
  • Remarkable Improvement of Damping Capacity of Mn–20Cu–5Ni–2Fe (at%)
           Alloy by Zinc Element Addition
    • Authors: Dong Li; Wenbo Liu, Ning Li, Jiazhen Yan, Sanqiang Shi
      Abstract: In this paper, the effect of Zn element addition on martensitic transformation and damping capacity of Mn–20Cu–5Ni–2Fe (at%, M2052) alloy has been investigated systematically by using X-ray diffraction, optical microscopy, and dynamic mechanical analyzer. The results show that martensitic transformation and damping capacity have a crucial dependence on the addition of Zn element. It not only can markedly enhance the damping capacity of M2052 alloy at room temperature (internal friction Q−1 increases by ≈23% compared to M2052 without Zn as strain amplitude reaches 4 × 10−4), but also reduces the attenuation of damping capacity effectively at elevated temperatures. This is mainly because the addition of Zn element can evidently increase the Gibbs free energy difference between γ parent phase and γ' phase produced by face centered cubic to face centered tetragonal (f.c.c-f.c.t) phase transformation, and then raises the martensitic transformation and its reverse transformation temperatures, eventually leading to the apparent increase of amount of f.c.t γ' phase micro-twins as damping source and the significant enhancement of damping capacity. It will be of great value for design and optimization of high-performance M2052 damping alloy toward practical applications.In this paper, the effect of Zn addition on martensitic transformation and damping capacity of M2052 alloy is investigated. Results show that it not only can markedly enhance the damping capacity of M2052 at room temperature, but reduces the attenuation of damping capacity effectively at elevated temperatures. This is because the Zn addition can raises the Ms from 50° C up to 58° C, thus leading to the increase of amount of f.c.t γ′ phase micro-twins as damping source.
      PubDate: 2017-08-07T06:55:31.118121-05:
      DOI: 10.1002/adem.201700437
       
  • Fracture Mode Transition in Nb–1Si Alloys Triggered by Annealing
           Heat Treatment
    • Authors: Bin Kong; Lina Jia, Songxin Shi, Yueling Guo, Hu Zhang
      Abstract: The concentration of Si plays a crucial role in the ductile-brittle transition of Nb solid solution (NbSS) alloys, and an appropriate annealing treatment contributes to controlling the Si concentration in NbSS alloy. In this paper, Nb–1Si (at%) alloy is arc-melted and annealed at different temperature (1300, 1400, and 1500 °C) for 10 h. After annealing, both the strength and ductility increase. Particularly, after annealing at 1300 °C, the fracture feature transforms from cleavage to dimples, and the alloy possesses good strength and retains decent ductility due to the low Si concentration and small-sized intragranular Nb3Si particles precipitating in the NbSS. The significant effect of annealing on the fracture mechanism of Nb–1Si provides guidance for the design of Nb–Si based alloys.The arc-melted Nb–1Si (at%) alloy (AM) fails in a brittle cleavage manner, mainly due to the embrittlement of Si and the plastic constraint imposed by the large silicides present in the eutectic compositions. After annealing at 1300 °C for 10 h (HT1300), the Si concentration in the NbSS decreases and submicron Nb3Si particles precipitate. As a result, the strength and elongation improve, and transition from a cleavage fracture to a dimple fracture occurs.
      PubDate: 2017-08-07T01:20:57.567511-05:
      DOI: 10.1002/adem.201700442
       
  • Temperature Effect on Performance of Triboelectric Nanogenerator
    • Authors: Cun Xin Lu; Chang Bao Han, Guang Qin Gu, Jian Chen, Zhi Wei Yang, Tao Jiang, Chuan He, Zhong Lin Wang
      Abstract: The triboelectric nanogenerator (TENG) is a promising energy harvesting technology that can convert mechanical energy into electricity and can be used as self-powered active sensors. However, previous studies are mostly carried out at room temperature without considering the temperature effect on the electrical performance of TENGs, which is critical for the application of electronics powered by TENGs in different regions in the world. In the present work, a TENG that worked in the single-electrode and contact-separation mode is utilized to reveal the influence of environment temperature on the electrical performance of TENG. The electrical performance of the TENG shows a decreasing tendency, as the temperature rises from −20 to 150 °C, which is controlled by the temperature-induced changes in the ability of storing and gaining electrons for polytetrafluoroethylene (PTFE). The storing electron ability change of PTFE is attributed to two aspects: one is the reduction of relative permittivity of PTFE sheet as the temperature increases, and the other is the variations of effective defects such as the escape of trapped charges in shallow traps and surface oxidation under the effect of temperature perturbation. This work can provide useful information for the application of TENG in both electric power generation and self-powered sensors in the harsh environment.We propose the temperature-induced effect on performance of triboelectric nanogenerator (TENG). The electrical performance of TENG is found to decrease with the increase of temperature. This temperature-induced effect on electrical performance of TENG is caused by following two reasons. 1) The changes of relative permittivity of the PTFE sheet. 2) The variation of electron traps such as the escape of trapped electric charges in shallow traps and surface oxidation under the effect of temperature perturbation.
      PubDate: 2017-08-07T01:20:28.765891-05:
      DOI: 10.1002/adem.201700275
       
  • Active Control of Microstructure in Powder-Bed Fusion Additive
           Manufacturing of Ti6Al4V
    • Authors: Guglielmo Vastola; Gang Zhang, Qing Xiang Pei, Yong-Wei Zhang
      Abstract: Because of the complex interactions among the energy beam, the powder bed, and the material phase transformations, powder-bed fusion additive manufacturing is very sensitive to process parameters, such as beam power and scan speed. As a result, the process window to produce fully-dense, ASTM-grade components is narrow. In such scenario, envisioning further control of mechanical properties is very challenging. As a departure from traditional attempts to control microstructure by changing the process parameters, the authors propose the introduction of a thermoelectric module (TEM) as an active device inside the build chamber. Using process modeling, the authors show that by altering the heat flow into the material through the TEM device, the volume fraction of martensite can be controlled in its entire range. In particular, the authors show that modern TEM modules can deliver sufficient thermal power to block the formation of martensite. As a result, microstructure can be controlled locally while retaining the beam power and scan speed optimal for part density and surface finish. While the results are demonstrated for Ti6Al4V and the electron beam melting process, the concept is general and, in principle, applicable to other materials and machines systems such as IN781 and selective laser melting.As a departure from traditional attempts to control microstructure, the authors propose the introduction of a thermoelectric module (TEM) as an active device inside additive manufacturing. The authors show that by altering the heat flow into the material through the TEM device, the volume fraction of martensite can be controlled. The concept is general and applicable to other materials and machines systems.
      PubDate: 2017-08-07T01:10:24.174339-05:
      DOI: 10.1002/adem.201700333
       
  • Investigation on the Controllable Microstructures of High Iron Content
           Al–Fe Alloys Fabricated via Solid–Liquid Mixture Method Combining with
           Plasma Arc Heating Approach
    • Authors: Yuli Zhou; Jian Wang, Mingyang He, Lin Gu, Peihua Wangyang
      Abstract: Al–Fe alloys, with large amounts of sphere-like structures, few plate-like structures, and little needle-like structures of micron scale second phase have been successfully prepared via a new type of solid–liquid mixture approach combined with plasma arc heating (PAH). The authors have obtained Al–Fe alloys with iron content of 0–15%, which is of extremely significance that thermal plasma jet (TPJ) breaks through the limitation of low iron content in Al–Fe alloys. Microstructures characterization indicates that not only the microstructures of Al–Fe alloys are refined, but also the morphologies are optimized. Meanwhile, sharp corners of iron powders are rounded off and impurities are removed under the action of PAH, which is important for improving mechanical property of Al–Fe alloys. And then, the effects of various parameters including PAH, iron content, and melt temperature on the microstructures and mechanical performance are systematically investigated. The possible influence mechanisms of parameters are investigated and put forward, and appropriate parameters have been obtained during the processing of Al–Fe alloys via TPJ.Al–Fe alloys with sphere-like Al3Fe, which own excellent mechanical performance, have been fabricated via solid–liquid mixture method combined with plasma arc heating approach. Meanwhile, the effects of various parameters involving PAH, iron content, and melt temperature on the microstructures and mechanical performance are systematically investigated. The possible influence mechanism of parameters in fabricating Al–Fe alloys have been further investigated.
      PubDate: 2017-08-04T06:45:35.837-05:00
      DOI: 10.1002/adem.201700426
       
  • A Review of Gold and Silver Nanoparticle-Based Colorimetric Sensing Assays
    • Authors: Myalowenkosi Sabela; Sebastien Balme, Mikhael Bechelany, Jean-Marc Janot, Krishna Bisetty
      Abstract: The nanoparticle colorimetric-based methods have been extensively used for rapid detection, however there are few limitations which can be kept under control or avoided by understanding the crucial parameters involved in these reactions. This review addresses the main parameters that influence colorimetric-based methods and provides a rational classification of the current approaches, by focusing particularly on gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs). The AgNP and AuNP-based colorimetric assays can be very efficient and sensitive especially for biomolecule identification and for metal ion detection in environmental screening. Specifically, this review highlights the detection of metal ions through their coordination with nanoparticle stabilizing ligands. The review also addresses various approaches based on label-free aptasensors to better understand their role as smart colorimetric sensing devices.This review addresses the main parameters that influence the nanoparticle colorimetric-based methods for rapid detection of biomolecules and metal ion in environmental screening. It provides a rational classification of the current approaches by focusing particularly on gold and silver nanoparticles.
      PubDate: 2017-08-03T06:06:07.945763-05:
      DOI: 10.1002/adem.201700270
       
  • Strengthening Nickel by In Situ Graphene Synthesis
    • Authors: Kaihao Zhang; Matthew Poss, Ping-Ju Chen, Sameh Tawfick
      Abstract: Owing to the superior strength and atomic thickness of graphene, it can in theory reinforce metals beyond the usual rule of mixtures bounds by constraining dislocations motion and strain localization at the grain boundaries. This unusual enhancement relies on the graphene's ability to conform to and wrap metal grains. This study experimentally probes the limits of this behavior and investigates the role of interface in designing superior graphene composites. Free-standing nickel–multilayer graphene (Ni–MLG) nanomembranes are fabricated by in situ chemical vapor deposition. Using nanoindentation, elastic modulus (285.16 GPa), maximum stress (2.35 GPa), and toughness (1407.26 Jm−2) are measured, and these values exceed the rule of mixtures bounds. The multi-frequency atomic force microscopy (AFM) is used to spatially map the elastic properties and topography of the MLG on Ni grain boundaries. This emerging characterization reveals that effective reinforcement is achieved when graphene conforms and bridges the grain texture. Nanoindentation and AFM confirm that these mechanisms are ineffective in non-conformally attached Ni–MLG composites, which exhibit significantly weaker mechanical behavior. These results guide the design of effective graphene composites by highlighting the importance of nanoscale roughness and interfaces, and clearly demonstrate the superiority of composite processing routes based on in situ graphene synthesis.Multi-functional nickel–multilayer graphene (Ni–MLG) composite thin film with ultra-high elastic modulus, strength, and toughness are readily synthesized via in situ chemical vapor deposition. The nanoscale surface roughness and the resulting conformal interface between nickel and graphene renders the strengthening and toughening of composite thin film.
      PubDate: 2017-08-02T07:10:36.835059-05:
      DOI: 10.1002/adem.201700475
       
  • Ferromagnetic Film − Substrate Decoupling for Sensor Applications
    • Authors: Stefan Beirle; Klaus Seemann, Harald Leiste, Sven Ulrich
      Abstract: This study presents the decoupling of ferromagnetic properties of Fe–Co–Hf–N films with an in-plane uniaxial anisotropy from ferromagnetic cemented carbide (WC–Co) substrates by predepositing a non-ferromagnetic buffer layer between the substrate and the film. Due to the ferromagnetic Co content in the substrate, a magnetic coupling effect arises which suppresses the natural ferromagnetic resonance of the Fe32Co45Hf11N12 film at a frequency of 2.13 GHz. The deposition of a non-ferromagnetic, electrically conductive TiN layer, or a non-ferromagnetic, electrically insulating SiO2 layer between the substrate and the soft ferromagnetic film shows decoupling regarding the static ferromagnetic properties, so that the formation of an in-plane uniaxial anisotropy is possible. With regard to the application as a high-frequency sensor the paper shows that with increasing the thickness of the electrically insulating SiO2 buffer layer the full width at half maximum (FWHM) of the resonance line becomes much sharper, in contrast to the electrically conductive TiN. The explanation was attributed to the formation of eddy-currents in the electrically conductive material causing a magnetic field which disturbs the uniform precession of the magnetic moments. The high-frequency properties of the decoupled film system are promising for a thermal and mechanical stress sensor system on cutting tools.Decoupling the soft ferromagnetic properties of Fe–Co–Hf–N films with an in-plane uniaxial anisotropy from hard ferromagnetic cemented carbide substrates (WC–Co) is promising for the realization of a thermal and/or mechanical stress sensor system on cutting tools. One part is to provide a magnetostrictive film system which allows to measure the natural ferromagnetic resonance. The present paper shows a way to decouple the ferromagnetic film from the substrate and demonstrates how the FWHM of the resonance line can be tuned.
      PubDate: 2017-08-02T01:55:54.274601-05:
      DOI: 10.1002/adem.201700397
       
  • Processing Induced Flaws in Aluminum–Alumina Interpenetrating Phase
           Composites
    • Authors: Michał Basista; Justyna Jakubowska, Witold Węglewski
      Abstract: This review paper deals with flaws in aluminum–alumina composites and FGMs induced by their manufacturing processes. Aluminum–alumina composites have been studied for many years as potentially interesting materials for applications, for example, in the automotive sector due to their enhanced mechanical strength, wear resistance, good heat conductivity and low specific weight. The focus here is on the interpenetrating phase composites (IPCs) manufactured by infiltration of porous alumina preforms with molten aluminum alloys. The primary objective is to provide an updated overview of research findings on a variety of flaws occurring at different stages of the manufacturing processes. Some precautions on how to avoid processing induced flaws in aluminum–alumina bulk composites and FGMs are mentioned.This review addresses potential flaws in metal ceramic interpenetrating phase composites (IPCs) and FGMs at different stages of their manufacturing processes. For aluminum–alumina IPCs the impact of process parameters, selection of pore forming technique, pore network morphology and wettability of ceramic preform by molten metal are discussed. The paper helps identify potential risks when considering the infiltration route for Al/Al2O3 manufacturing.
      PubDate: 2017-08-01T09:22:58.595422-05:
      DOI: 10.1002/adem.201700484
       
  • Tensile and High-Cycle Fatigue Properties of Steel Sheet with Trace
           Silicon
    • Authors: Meng Xiao Zhang; Jian Chao Pang, Li Bei Zhu, Long Pan, Liang Liang Nie, Yun Xian Mao, Man Chen, Zhe Feng Zhang
      Abstract: The tensile properties, high-cycle fatigue properties, fracture surface morphologies, corresponding damage mechanisms, and dislocation patterns of two steels with trace silicon, 550TG and SD320, are investigated. It is found that the SD320 has a higher tensile strength than 550TG, but lower plasticity. In general, some deep cracks appear along the direction of rolling in all the tensile specimens and the fatigue limit of SD320 is higher. In particular, the 550TG shows a continuously decreasing S–N characteristic without fatigue limit at the higher cycle region, which can be explained by their differences of dislocation morphologies. Furthermore, the tensile and fatigue damage mechanisms are deeply analyzed and discussed.Due to the different evolutions of dislocations, there is a typical yielding plateau in 550TG and no similar phenomenon in SD320. Meanwhile, among the HCF region, the 550TG shows a continuously decreasing S–N characteristic; but for SD320, the knee point starts at 5 × 105 cycles. The fatigue limit is closely related to the yield strength.
      PubDate: 2017-07-28T06:16:04.263511-05:
      DOI: 10.1002/adem.201700476
       
  • Microstructure and Mechanical Properties of Al–12.6Si Eutectic Alloy
           Modified with Al–5Ti Master Alloy
    • Authors: Shuo Wang; Ya Liu, Haoping Peng, Xiaowang Lu, Jianhua Wang, Xuping Su
      Abstract: The Al–12.6Si eutectic alloy has been modified via the Al–5Ti master alloy to improve both microstructure and mechanical properties. The results show that the fraction of the primary α–Al phase in the Al–12.6Si alloy and the mechanical properties of the resulting alloy vary considerably after modification with the Al–5Ti master alloy at different temperatures. With increasing modification temperature, the fraction of primary α–Al in the Al–12.6Si alloy increases, varying with the amount of added Al–5Ti. For an added amount of 0.2 wt.% Al–5Ti, the fraction of primary α–Al in the Al–12.6Si alloy reaches a maximum. The tensile strength and elongation of an Al–12.6Si alloy modified with 0.2 wt.% Al–5Ti at different temperatures evidently increase compare with unmodified alloys.The eutectic point of Al–Si alloy moves to the right with increasing temperature, resulting in increase of the fraction of primary α–Al. Adding 0.2 wt.% Al–5Ti causes maximal moving distance of the eutectic point to the right, leading to the formation of maximal fraction of primary α–Al, and remarkable increase of mechanical properties of Al–12.6 wt.% Si alloy.
      PubDate: 2017-07-28T04:00:29.051838-05:
      DOI: 10.1002/adem.201700495
       
  • Compressive Response and Energy Absorption Characteristics of In Situ
           Grown CNT-Reinforced Al Composite Foams
    • Authors: Xudong Yang; Kunming Yang, Jiwei Wang, Chunsheng Shi, Chunnian He, Jiajun Li, Naiqin Zhao
      Abstract: Carbon nanotube (CNT) reinforced Al composite foams with different CNT contents are fabricated through an improved powder metallurgy approach by combining in-situ chemical vapor deposition (CVD), short time ball-milling, and space-holder method. The CNTs are uniformly dispersed on the surface of Al particles by in-situ CVD process, followed by a short time ball-milling process enabling an excellent interfacial bonding between CNTs and the Al matrix. The pore size and microstructures of the composite foams can be well tailored by the carbamide particle templates. The yield strength and energy absorption capacity of composite foams reach 18.1 MPa and 15.8 MJ m−3 with 3.0 wt% CNT addition, which are ≈1.3 and ≈3.6 times higher than those of pure Al foam, respectively. The energy absorption efficiency of the CNT/Al composite foams achieves a maximum of ≈0.86, when the CNT content is up to 3.0 wt%. Additionally, compressive and energy absorption properties of the CNT/Al composite foams increase with the increment of relative density. The failure mode of the Al foam changes from plastic mode to brittle mode combined with ductile mode, as a result of CNT addition.Uniformly dispersed CNTs reinforced Al composite foams are successfully fabricated by the combination of an in situ chemical vapor deposition, short-time ball-milling, and space-holder method. Besides, the pores well replicate the shape and size of the original spherical carbamide particles.
      PubDate: 2017-07-26T07:45:35.038967-05:
      DOI: 10.1002/adem.201700431
       
  • Direct Liquid Injection − Low Pressure Chemical Vapor Deposition of
           Silica Thin Films from Di-t-butoxydiacetoxysilane
    • Authors: Mattias Vervaele; Bert De Roo, Jolien Debehets, Marilyne Sousa, Luman Zhang, Bart Van Bilzen, Stephanie Seré, Herve Guillon, Markku Rajala, Jin Won Seo, Jean-Pierre Locquet
      Abstract: In this work, an unusual silicon chemical vapor deposition precursor is used, which allows the safe deposition of thin silica films in a controlled and reproducible manner at a lower thermal budget with a newly developed direct liquid injection − low pressure chemical vapor deposition system. The deposition is controlled by parameters such as deposition temperature, partial pressure of the gases, and flow rate of the precursor solution. X-ray reflectivity and spectroscopic ellipsometry of the deposited samples show that the thickness of the layers is well controlled by deposition temperature, time, and oxygen flow. A growth rate of 4.5 Å min−1 is obtained without the addition of oxygen, which can be increased to 10.2 Å min−1 by the addition of oxygen. Atomic force microscopy, Rutherford backscattering spectroscopy, Fourier transform infrared spectroscopy, and drop shape analysis are used to measure roughness, composition, and hydrophobicity. Thin films of silicon dioxide are successfully grown. In addition, this newly developed system can be used for a wide range of films by varying the precursors or by co-injecting nanoparticles suspension mixed with the chemical vapor deposition precursor in the direct liquid injection vaporizer.This work describes the use of the unusual silicon chemical vapor deposition precursor di-t-butoxydiacetoxysilane (DADBS), which allows the safe deposition of thin silica films in a controlled and reproducible manner at a lower thermal budget with a newly developed direct liquid injection – low pressure chemical vapor deposition system.
      PubDate: 2017-07-17T04:11:31.246894-05:
      DOI: 10.1002/adem.201700425
       
  • Mass Transfer Performance of Porous Nickel Manufactured by Lost Carbonate
           Sintering Process
    • Authors: Pengcheng Zhu; Yuyuan Zhao
      Abstract: Open cell porous metals are excellent electrode materials due to their unique electrochemical properties. However, very little research has been conducted to date on the mass transport of porous metals manufactured by the space holder methods, which have distinctive porous structures. This paper measures the mass transfer coefficient of porous nickel manufactured by the Lost Carbonate Sintering process. For porous nickel samples with a porosity of 0.55–0.75 and a pore size of 250–1500 μm measured at an electrolyte flow velocity of 1–12 cm s−1, the mass transfer coefficient is in the range of 0.0007–0.014 cm s−1, which is up to seven times higher than that of a solid nickel plate electrode. The mass transfer coefficient increases with pore size but decreases with porosity. The porous nickel has Sherwood numbers considerably higher than the other nickel electrodes reported in the literature, due to its high real surface area and its tortuous porous structure, which promotes turbulent flow.Porous nickel manufactured by the Lost Carbonate Sintering (LCS) process has higher Sherwood numbers than many other nickel electrodes in the modest range of Reynolds number due to its high real surface area and tortuous structures.
      PubDate: 2017-07-05T04:31:56.334266-05:
      DOI: 10.1002/adem.201700392
       
  • Synthesis and Vacuum Cold Spray Deposition of Biofunctionalized
           Nanodiamond/Hydroxyapatite Nanocomposite for Biomedical Applications
    • Authors: Deyan Li; Xiuyong Chen, Yongfeng Gong, Botao Zhang, Yi Liu, Peipeng Jin, Hua Li
      Abstract: Insufficient biological performances of titanium alloys have been the long-standing problems for their clinical applications. Here, we report synthesis of novel hydroxyapatite/nanodiamond-bone morphogenetic protein 2 (HA-ND/BMP2) composite powder and their coatings deposited by vacuum cold spray operated at room temperature. The microstructure and chemistry of the HA-ND/BMP2 powder and coatings are characterized by transmission electron microscopy, field-emission scanning electron microscopy, thin-film X-ray diffraction, Raman spectrometry, and X-ray photoelectron spectroscopy. In vitro growth assay of osteoblasts on the coatings showed that the biofunctionalized nanodiamonds promoted cell adhesion and proliferation. This study provides a promising technical route for constructing biofunctionalized nanocomposites coatings for potential biomedical applications.Novel hydroxyapatite/nanodiamond-bone morphogenetic protein 2 (HA-ND/BMP2) coatings are fabricated on titanium substrates for biomedical applications by VCS processed at room temperature. The nanocomposite coatings offer significantly promoted biological properties for the titanium substrates by the presence of NDs and BMP2.
      PubDate: 2017-06-28T08:05:42.049826-05:
      DOI: 10.1002/adem.201700363
       
  • In Situ Study of Deformation Twinning and Detwinning in Helium Irradiated
           Small-Volume Copper
    • Authors: Wei-Zhong Han; Ming-Shuai Ding, R. Lakshmi Narayan, Zhi-Wei Shan
      Abstract: The influence of nanoscale helium bubbles on the deformation twinning and detwinning behavior of submicron-sized Cu is investigated under tension, compression, and cyclic loading. In situ nanomechanical tests performed inside a transmission electron microscope reveal that twinning and detwinning occur readily in helium irradiated copper under both tension and compression. Continuous shearing of helium bubbles by Shockley partials leads to twin formation, whereas the residual back-stress accumulated from dislocation-bubble interactions assist in detwinning. These interactions also elevate the critical shear stress for partial dislocation slip in helium irradiated Cu compared to that in fully dense Cu. The growth twin boundaries can significantly enhance the twinning stress in helium irradiated Cu pillar, and deformation twin-growth twin boundary interaction promotes the formation of internal crack and thus accelerates failure. The effect of crystallographic orientation and sample size on the overall deformation characteristics of helium irradiated Cu is briefly discussed. The current studies show that deformation twinning and detwinning are also active deformation models in helium irradiated small-volume copper.In situ nanomechanical tests performed inside a transmission electron microscope reveal that twinning and detwinning occur readily in helium irradiated copper under both tension and compression. Continuous shearing of helium bubbles by Shockley partials leads to twin formation whereas the residual back-stress accumulated from dislocation-bubble interactions assist in detwinning.
      PubDate: 2017-06-16T01:00:29.347648-05:
      DOI: 10.1002/adem.201700357
       
  • Soft Robotics: Review of Fluid-Driven Intrinsically Soft Devices;
           Manufacturing, Sensing, Control, and Applications in Human-Robot
           Interaction 
    • Authors: Panagiotis Polygerinos; Nikolaus Correll, Stephen A. Morin, Bobak Mosadegh, Cagdas D. Onal, Kirstin Petersen, Matteo Cianchetti, Michael T. Tolley, Robert F. Shepherd
      Abstract: The emerging field of soft robotics makes use of many classes of materials including metals, low glass transition temperature (Tg) plastics, and high Tg elastomers. Dependent on the specific design, all of these materials may result in extrinsically soft robots. Organic elastomers, however, have elastic moduli ranging from tens of megapascals down to kilopascals; robots composed of such materials are intrinsically soft − they are always compliant independent of their shape. This class of soft machines has been used to reduce control complexity and manufacturing cost of robots, while enabling sophisticated and novel functionalities often in direct contact with humans. This review focuses on a particular type of intrinsically soft, elastomeric robot − those powered via fluidic pressurization.This manuscript presents a comprehensive review of the materials, design, and manufacturing of fluidically pressurized intrinsically soft robotics, and set a historical context for their development. The authors then discuss their applications for human interaction and speculate on future composition and use cases.
      PubDate: 2017-05-31T08:57:19.925404-05:
      DOI: 10.1002/adem.201700016
       
 
 
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