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COMPUTER SCIENCE (1160 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: 3)
Academy of Information and Management Sciences Journal     Full-text available via subscription   (Followers: 72)
ACM Computing Surveys     Hybrid Journal   (Followers: 22)
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: 11)
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: 13)
ACM Transactions on Computing Education (TOCE)     Hybrid Journal   (Followers: 4)
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: 20)
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: 8)
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: 22)
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: 7)
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: 13)
Advances in Computing     Open Access   (Followers: 2)
Advances in Data Analysis and Classification     Hybrid Journal   (Followers: 52)
Advances in Engineering Software     Hybrid Journal   (Followers: 25)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 10)
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: 37)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Advances in Technology Innovation     Open Access   (Followers: 2)
AEU - International Journal of Electronics and Communications     Hybrid Journal   (Followers: 8)
African Journal of Information and Communication     Open Access   (Followers: 7)
African Journal of Mathematics and Computer Science Research     Open Access   (Followers: 4)
Air, Soil & Water Research     Open Access   (Followers: 8)
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: 7)
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: 9)
Annals of Mathematics and Artificial Intelligence     Hybrid Journal   (Followers: 6)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of Software Engineering     Hybrid Journal   (Followers: 12)
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: 2)
Applied Artificial Intelligence: An International Journal     Hybrid Journal   (Followers: 14)
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: 128)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 4)
Artifact     Hybrid Journal   (Followers: 2)
Artificial Life     Hybrid Journal   (Followers: 6)
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  
Automatic Control and Computer Sciences     Hybrid Journal   (Followers: 3)
Automatic Documentation and Mathematical Linguistics     Hybrid Journal   (Followers: 5)
Automatica     Hybrid Journal   (Followers: 9)
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)
Bioinformatics     Hybrid Journal   (Followers: 302)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 17)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 32)
Briefings in Bioinformatics     Hybrid Journal   (Followers: 44)
British Journal of Educational Technology     Hybrid Journal   (Followers: 123)
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)
Catalysis in Industry     Hybrid Journal   (Followers: 1)
CEAS Space Journal     Hybrid Journal  
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: 15)
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: 11)
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: 53)
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: 12)
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: 14)
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: 31)
Computer     Full-text available via subscription   (Followers: 85)
Computer Aided Surgery     Hybrid Journal   (Followers: 3)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 6)
Computer Communications     Hybrid Journal   (Followers: 10)
Computer Engineering and Applications Journal     Open Access   (Followers: 5)
Computer Journal     Hybrid Journal   (Followers: 7)
Computer Methods in Applied Mechanics and Engineering     Hybrid Journal   (Followers: 22)
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: 11)
Computer Science Education     Hybrid Journal   (Followers: 12)
Computer Science Journal     Open Access   (Followers: 20)
Computer Science Master Research     Open Access   (Followers: 10)
Computer Science Review     Hybrid Journal   (Followers: 10)

        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  [1579 journals]
  • Using Post-Deformation Annealing to Optimize the Properties of a ZK60
           Magnesium Alloy Processed by High-Pressure Torsion
    • Authors: Seyed A. Torbati-Sarraf; Shima Sabbaghianrad, Terence G. Langdon
      Abstract: A ZK60 magnesium alloy with an initial grain size of ≈10 µm is processed by high-pressure torsion (HPT) through 5 revolutions under a constant compressive pressure of 2.0 GPa with a rotation speed of 1 rpm. An average grain size of ≈700 nm is achieved after HPT with a high fraction of high-angle grain boundaries. Tensile experiments at room temperature show poor ductility. However, a combination of reasonable ductility and good strength is achieved with post-HPT annealing by subjecting samples to high temperatures in the range of 473–548 K for 10 or 20 min. The grain size and texture changes are also examined by electron back scattered diffraction (EBSD) and the results compared to long-term annealing for 2500 min at 450 K. The results of this study suggest that a post-HPT annealing for a short period of time may be effective in achieving a reasonable combination of strength and ductility.The production of ultrafine grained structure through the severe plastic deformation processes is of increasing interests in lightweight materials. Magnesium alloys show poor ductility at room temperature after severe plastic deformation. The results of this study suggest that a post-HPT annealing for a short period of time can be effective in achieving a reasonable combination of strength and ductility.
      PubDate: 2017-10-16T01:46:40.061658-05:
      DOI: 10.1002/adem.201700703
  • Nature-Inspired Lightweight Cellular Co-Continuous Composites with
           Architected Periodic Gyroidal Structures
    • Authors: Oraib Al-Ketan; Ahmad Soliman, Ayesha M. AlQubaisi, Rashid K. Abu Al-Rub
      Abstract: Shell-core cellular composites are a unique class of cellular materials, where the base constituent is made of a composite material such that the best distinctive physical and/or mechanical properties of each phase of the composite are employed. In this work, the authors demonstrate the additive manufacturing of a nature inspired cellular three-dimensional (3D), periodic, co-continuous, and complex composite materials made of a hard-shell and soft-core system. The architecture of these composites is based on the Schoen's single Gyroidal triply periodic minimal surface. Results of mechanical testing show the possibility of having a wide range of mechanical properties by tuning the composition, volume fraction of core, shell thickness, and internal architecture of the cellular composites. Moreover, a change in deformation and failure mechanism is observed when employing a shell-core composite system, as compared to the pure stiff polymeric standalone cellular material. This shell-core configuration and Gyroidal topology allowed for accessing toughness values that are not realized by the constituent materials independently, showing the suitability of this cellular composite for mechanical energy absorption applications.The figure shows designed and 3D printed architected co-continuous composites with rigid shell and soft core configuration. The proposed co-continuous composite employs a topology-property relationship that allows controlling the mechanical and physical properties by tuning its architecture.
      PubDate: 2017-10-16T01:05:42.596707-05:
      DOI: 10.1002/adem.201700549
  • Novel 3D-Printed Hybrid Auxetic Mechanical Metamaterial with
           Chirality-Induced Sequential Cell Opening Mechanisms
    • Authors: Yunyao Jiang; Yaning Li
      Abstract: New hybrid auxetic chiral mechanical metamaterial are designed and fabricated via multi-material 3D printing. Due to the chirality-induced rotation, the material have unique sequential cell-opening mechanisms. Mechanical experiments on the 3D printed prototypes and systematic FE simulations show that the effective stiffness, the Poisson's ratio and the cell-opening mechanisms of the new design can be tuned in a very wide range by tailoring two non-dimensional parameters: the cell size ratio and stiffness ratio of component materials. As example applications, sequential particle release mechanisms and color changing mechanisms of the new designs are also systematically explored. The present new design concepts can be used to develop new multi-functional smart composites, sensors and/or actuators which are responsive to external load and/or environmental conditions for applications in drug delivery and color changing for camouflage.Novel hybrid auxetic chiral mechanical metamaterial are designed and fabricated via multi-material 3D printing. Due to chirality-induced rotation, the new auxetic mechanical metamaterials have unique sequential cell-opening mechanisms under uni-axial tension. As demos, the present new design concepts are used to develop multi-functional smart materials for sequential particle release and color changing for camouflage.
      PubDate: 2017-10-11T08:10:42.053775-05:
      DOI: 10.1002/adem.201700744
  • Mechanical and Electromagnetic Interference Shielding Behavior of C/SiC
           Composite Containing Ti3SiC2
    • Authors: Xiaomeng Fan; Xiaowei Yin, Yanzhi Cai, Litong Zhang, Laifei Cheng
      Abstract: In order to obtain the composites with the integration of structural and functional properties, Ti3SiC2 is introduced into C/SiC due to its excellent damage tolerance and electromagnetic interference (EMI) shielding properties. C/SiC–Ti3SiC2 has the lower tensile strength, while the higher compressive strength than C/SiC. The penetration energy of C/SiC–Ti3SiC2 in the impact experiment is improved at least three times than that of C/SiC, resulting from the improved damage tolerance. With the introduction of Ti3SiC2, the EMI shielding effectiveness increases from 31 to 41 dB in X-band (8.2 to 12.8 GHz) due to the increase of electrical conductivity. C/SiC–Ti3SiC2 reveals the great potential as structural and functional materials based on the multi-functional properties.With the introduction of Ti3SiC2 by liquid silicon infiltration, the dense inter-bundle matrix with high damage-tolerance and electrical-conductivity can be obtained for C/SiC–Ti3SiC2, resulting in the better compressive strength, impact resistance, and electromagnetic interference shielding properties than those of C/SiC, which reveals the great potential as structural and functional materials.
      PubDate: 2017-10-11T08:01:15.82601-05:0
      DOI: 10.1002/adem.201700590
  • Influences of Friction Stir Welding and Post-Weld Heat Treatment on
           Al–Cu–Li Alloy
    • Authors: Yi Lin; Change Lu, Chengyang Wei, Ziqiao Zheng
      Abstract: In this paper, the influences of friction stir welding (FSW) and post-weld heat treatment (PWHT) on the microstructures and tensile properties of Al–Cu–Li alloy are investigated. After FSW, strengthen loss occurred in the welding area. Remarkable softening occurs in the thermo-mechanically affected zone (TMAZ) resulting from dissolution of Al3Li (δ′) phases. Recrystallization and precipitation of ultra-fine δ′ phases take place in the nugget zone (NZ) that lightens the softening degree of this zone. A noteworthy enhancement in the hardness and tensile strength of the joint is achieved after T8 re­aging treatment (3% − pre-deformation, 30 h at 152 °C). However, re-solution treatment coupled with re-aging treatment leads to ductility deterioration in the joint because coplanar slip of coarse Al3Li phases induces severe stress concentration during plastic deformation.The paper investigates the microstructure and mechanical properties evolution of Al–Cu–Li alloy during FSW and PHWTs. The results show that dissolution of strengthening phases induces the strength loss after FSW, and the T8 re-aging treatment can effectively enhances the strength of joint without the ductility being excessively deteriorated.
      PubDate: 2017-10-10T06:21:18.021152-05:
      DOI: 10.1002/adem.201700652
  • 3-D Printing and Development of Fluoropolymer Based Reactive Inks
    • Authors: Fidel D. Ruz-Nuglo; Lori J. Groven
      Abstract: Engineering reactive materials is an ever present goal in the energetics community. The desire is to have energetics configured in such a manner that performance is tailored and energy delivery can be targeted. Additive manufacturing (3-D printing) is one area that could significantly improve our capabilities in this area, if adequate formulations are developed. In this paper, fluoropolymer based reactive inks are developed with micron (mAl) and nanoscale aluminum (nAl) serving, as the fuel at high solids loading (up to 67 wt%) and their viscosity required for 3-D printing is detailed. For the pen-type technique and valves used in this work, it is required to have viscosities on the order of 104–105 cP. For printed traces with apparent diameters under
      PubDate: 2017-10-09T07:10:53.772388-05:
      DOI: 10.1002/adem.201700390
  • Galvanic Corrosion and Mechanical Behavior of Fiber Metal Laminates of
           Metallic Glass and Carbon Fiber Composites
    • Authors: Lee Hamill; Douglas C. Hofmann, Steven Nutt
      Abstract: The possibility of galvanic corrosion typically prohibits the pairing of carbon fiber and aluminum in a fiber metal laminate (FML). In this study, the authors describe a new type of FML comprised of alternating layers of bulk metallic glass (BMG) and carbon fiber reinforced polymer (CFRP) composite. The authors compare the galvanic coupling and mechanical behavior of an Al-based FML and a BMG-CFRP FML. Results show that when paired with CFRPs, BMG exhibits far less galvanic corrosion than aluminum paired with CFRP. In fact, the corrosion between BMG and CFRP is similar in magnitude to the corrosion between aluminum and glass fiber, the two constituent materials of GLARE, the most widely used FML. While interlaminar shear strength and flexural strength are similar for both FML types, the tensile strength and modulus of BMG-based FMLs are greater than those of Al-based FMLs.The galvanic corrosion resistance and mechanical performance of two fiber metal laminates are compared. Results show negligible galvanic corrosion and increased tensile strength and modulus in BMG-CFRP laminates when compared to AL-CFRP counterparts. To date, very few galvanic corrosion resistant options exist for CFRP-based FMLs, and the results of this study expand those options.
      PubDate: 2017-10-09T02:25:49.736964-05:
      DOI: 10.1002/adem.201700711
  • Optimization of Composite Foam Concept for Protective Helmets to Mitigate
           Rotational Acceleration of the Head in Oblique Impacts: A Parametric Study
    • Authors: Yasmine Mosleh; Leonard Pastrav, Aart Willem van Vuure, Bart Depreitere, Jos Vander Sloten, Jan Ivens
      Abstract: Rotational acceleration of the head is known to be the cause of traumatic brain injuries. It was hypothesized that by introducing anisotropy in a foam liner in head protection applications, for example, protective helmets, rotational acceleration transmitted to the head can be further mitigated. Therefore, composite foam with a cylinder/matrix configuration with anisotropy at “macro level” is proposed as a smart structural solution to replace single layer foam headliners of the same weight and thickness. In this paper, a parametric study on the cylinder/matrix configuration is performed and the results are compared with these of single layer expanded polystyrene foam. The structure is subsequently optimized for the best performance in mitigation of rotational acceleration and velocity. Oblique impact results show that the parameters such as the number of cylinders in a given structure, and the compliance of the matrix foam significantly affect the extent of rotational acceleration and velocity mitigation. Optimized composite foam configurations are subsequently proposed and they demonstrate a mitigation of rotational acceleration and velocity up to 44 and 19%, respectively. Moreover, relevant global head injury criteria such as HIC (Head Injury Criterion), RIC (Rotational Injury Criterion), HIPmax (Head Impact Power), GAMBIT (Generalised Acceleration Model for Brain Injury Threshold), and BrIC (Brain Injury Criterion) demonstrated reduction up to 27, 67, 31, 26, and 19%, respectively.In this paper, a parametric study on composite foam with cylinder/matrix configuration is performed to optimize the structure for mitigation of head rotational acceleration during oblique impact. The results show that parameters such as the number of cylinders in the structure, and the compliance of the matrix foam significantly affect the extent of mitigation of head rotational acceleration.
      PubDate: 2017-10-09T02:25:37.747543-05:
      DOI: 10.1002/adem.201700443
  • The Fabrication and Characterization of Bimodal Nanoporous Si with
           Retained Mg through Dealloying
    • Authors: Tyler L. Maxwell; T. John Balk
      Abstract: The fabrication and characterization of bimodal nanoporous silicon films with retained magnesium, achieved through a novel approach utilizing free corrosion dealloying of precursor Si–Mg films in distilled water, is studied. Investigation of film structure and chemical composition using various techniques reveals important characteristics potentially relevant to lithium-ion battery applications. Dealloying of precursor films results in a hierarchal structure, where larger ligaments have an average width of 83 nm and smaller ligaments an average width of 19 nm. A thin, porous surface layer is present on most dealloyed films and is largely composed of magnesium and silicon oxides, as verified by XPS surface analysis. TEM studies reveal that as-dealloyed films are amorphous, but nanocrystalline silicon grains form after vacuum annealing at 500 °C. EDS mapping and XPS reveal three distinct chemical composition regions through the film thickness, where residual magnesium generally increases as a function of film thickness, with the highest amount of retained magnesium at the surface. The ligament size, composition, and structure, combined with the simple, non-hazardous nature of the dealloying method, make this an attractive material and processing technique for efficient and scalable production of lithium-ion battery anode material.This paper presents a facile approach to create bimodal nanoporous silicon films with residual magnesium, by dealloying sputter-deposited silicon-magnesium precursors in distilled water. The microstructure of films before and after annealing is characterized with SEM and TEM, while chemical composition is analyzed with EDS and XPS surface analysis. This material's characteristics make it a promising candidate for lithium–ion battery applications.
      PubDate: 2017-10-09T01:25:42.579217-05:
      DOI: 10.1002/adem.201700519
  • Rationally Designed Silicon Nanostructures as Anode Material for
           Lithium-Ion Batteries
    • Authors: Tong Shen; Zhujun Yao, Xinhui Xia, Xiuli Wang, Changdong Gu, Jiangping Tu
      Abstract: Silicon (Si) is promising for high capacity anodes in lithium-ion batteries due to its high theoretical capacity, low working potential, and natural abundance. However, there are two main drawbacks that impede its further practical applications. One is the huge volume expansion generating during lithiation and delithiation progresses, which leads to severe structural pulverization and subsequently rapid capacity fading of the electrode. The other is the relatively low intrinsic electronic conductivity, therefore, seriously impacting the rate performance. In the past decades, numerous efforts have been devoted for improving the cycling stability and rate capability by rational designs of different nanostructures of Si materials and incorporations with some conductive agents. In this review, the authors summarize the exciting recent research works and focus on not only the synthesis techniques, but also the composition strategies of silicon nanostructures. The advantages and disadvantages of the nanostructures as well as the perspective of this research field are also discussed. We aim to give some reference for engineering application on Si anodes in lithium ion batteries.The authors summarize the strategies that developed lately for improving the electrochemical performance of Si materials. Special focus in this review is the recent progresses in the rational fabrication of Si nanostructures with multiple morphologies, including nanoparticles, nanowires, thin films, and porous structures. Moreover, further improvement tactics, such as collaborating with carbonaceous materials, conductive polymers, and alloy materials are also discussed.
      PubDate: 2017-10-05T08:32:53.56802-05:0
      DOI: 10.1002/adem.201700591
  • Combined Microwave and Laser Heating for Glazing of 8Y–ZrO2 and
    • Authors: Sebastian Lehmann; Jens Böckler, Monika Willert-Porada, Andreas Rosin, Christian Richter
      Abstract: Sintered porous yttria-stabilized zirconia and zirconia composite ceramics with zirconium silicate are surface glazed by Laser-Assisted Microwave Plasma Processing (LAMPP). Suitable process parameters for surface glazing are determined for those ceramics. The plasma process is monitored by means of pyrometry and optical emission spectroscopy. In order to prove the quality of the surface glazing and to characterize hot corrosion resistance, tests with molten vanadium pentoxide are performed. After 4 h of exposure, the penetration depth of the molten salt is investigated as a function of ceramic composition and pre-treatment by glazing. Upon hot corrosion testing of glazed and non-glazed ceramics, the molten vanadium pentoxide reacts selectively with yttrium oxide, forming yttrium vanadate, and causes crack formation in the zirconia ceramics due to transition to monoclinic zirconia. The results for LAMPP-glazed ceramics show, that a surficial melting phase is achieved because process temperatures exceed 3000 °C. Hence, a dense, crack-free and hardness-enhanced surface layer achieves a better resistance to hot corrosion as compared to non-glazed ceramics. Due to LAMPP-glazing, the vanadium ingress is reduced from 33 to 7 μm for yttria-stabilized zirconia and from 104 to 17 μm for zirconia composite ceramic. Reactions and microstructural changes taking place upon LAMP-Processing are discussed.Suitable process parameters for surface glazing by Laser-Assisted Microwave Plasma Processing of sintered porous zirconia-based ceramics are determined. The plasma process is monitored by means of pyrometry and optical emission spectroscopy. Microstructural investigation and phase analysis is performed before and after hot corrosion test with molten vanadium pentoxide. The dense, crack-free surface layer provides a better resistance to hot corrosion.
      PubDate: 2017-10-04T02:56:26.085561-05:
      DOI: 10.1002/adem.201700615
  • Synthesis of Composite Nanosheets of Graphene and Boron Nitride and Their
           Lubrication Application in Oil
    • Authors: Yuchen Liu; Srikanth Mateti, Chao Li, Xuequan Liu, Alexey M. Glushenkov, Dan Liu, Lu Hua Li, Daniel Fabijanic, Ying Chen
      Abstract: Composite nanosheets of graphene and boron nitride have been produced in large quantities for the first time using high-energy ball milling in ammonia gas as an exfoliation agent. The anti-wear properties of the composite nanosheets as a lubricant additive are investigated via a four-ball method. The results show that the composite nanosheets are exfoliated from the commercial graphite and h-BN powders and combined into graphene/BN composite nanosheets during the ball milling process. The composite nanosheets formed have diameters larger than 200 nm and consist of heterostructures of approximately 10 monolayers of graphene and BN. The composite nanosheets exhibit better wear resistance and friction reduction properties than the homogeneous nanosheets because of the stronger interaction between graphene and BN nanosheets, which can effectively improve the anti-wear properties of mineral base oil as a lubricant additive.The graphene/BN composite nanosheets produced by gas-assisted ball milling process form a protection film on the testing material surface leading to a lower friction coefficient and improved anti-wear properties.
      PubDate: 2017-09-29T10:41:35.337143-05:
      DOI: 10.1002/adem.201700488
  • Understanding Wear Interface Evolution to Overcome Friction and Restrain
           Wear of TiAl–10 wt%Ag Composite
    • Authors: Kang Yang; Hongru Ma, Xiyao Liu, Qiang He
      Abstract: The main objective of this paper is to study wear interface evolution for analyzing the of friction and wear property of TiAl–10 wt%Ag composite. The results show that the friction coefficient and wear rate of TiAl–10 wt%Ag rapidly reduce at 0–25 min and rhythmically fluctuate at 25–60 min. TiAl–10 wt%Ag at 60–240 min obtains low friction and less wear. It is concluded that silver with the low shearing strength of about 125 MPa shows the eminent plastic deformation on wear interface. It effectively reduces friction resistance and material loss, cause TiAl–10 wt%Ag to obtain low friction coefficient, and less wear rate at 0–25 min. Increased silver content, reduces oxide content, and varies wear mechanisms cause the repeating variation of friction resistance and material loss, which results in the rhythmical fluctuation of friction coefficient and wear rate at 25–60 min. High silver contents exist on smooth wear interfaces, exhibit the eminent plastic deformation to lower friction and reduce wear. TiAl–10 wt%Ag obtains the low friction and less wear at 60–240 min.At 240 min, small plastic deformation body forms on smooth wear interface. It indicates that the main wear mechanism of TiAl–10 wt%Ag is plastic deformation. The FESEM surface micro-morphology of wear interface in rectangular region is clearly exhibited. Solid lubricant silver is uniformly distributed on wear interface, and exhibits excellent plastic deformation, leading to low friction and less wear.
      PubDate: 2017-09-28T11:27:37.882845-05:
      DOI: 10.1002/adem.201700637
  • Porous Polymer Membranes by Hard Templating – A Review
    • Authors: Mario Stucki; Michael Loepfe, Wendelin J. Stark
      Abstract: Membranes are designed to bridge a precise separation process at the nanoscale with industrial applications running at cubic meters per hour. This review outlines materials applied in membrane production with a particular focus on polymers. Membrane performance and created value are directly linked to controlled pore formation. Their economic relevance has created a number of large companies and associated academic research at top institutions. The authors review, therefore, starts from well-established techniques applied in products and then moves on to evolving concepts from academia. Pore formation through hard templating is a versatile field for separation processes. A more detailed view is given on the two known concepts for nanopore formation, namely colloidal templates and random hard salt templating. A comparison between these two concepts underlines their relevance to combine a process specific separation with large scale manufacturing requirements (i.e., upscale possibility, flexible process control and environmental impact).Membranes bridge nanoscale separation with high volume throughput. The development of membranes has resulted in a large variety of materials used for porous separators. This article introduces the relevant membrane processes and focuses on porous polymer membranes. Its main body explains sacrificial hard templating. Ordered colloidal crystals are compared to random templates with respect to their scalability and application.
      PubDate: 2017-09-28T00:05:53.544922-05:
      DOI: 10.1002/adem.201700611
  • A Combined Electromagnetic Levitation Melting, Counter-Gravity Casting,
           and Mold Preheating Furnace for Producing TiAl Alloy
    • Authors: Jieren Yang; Hu Wang, Yulun Wu, Xuyang Wang, Rui Hu
      Abstract: In this work, the authors describe the development of TiAl castings over a wide range of approaches. To overcome casting defects and cracks that appear in TiAl castings, a novel furnace is designed and constructed. The design combines induction skull melting, counter-gravity casting, and mold heating, which facilitates both filling and microstructure formation via a controllable process. This aim is to improve shaping capabilities and microstructural control for TiAl castings. Melting and casting experiments on TiAl alloys with a nominal composition corresponding to Ti–48Al–2Cr–2Nb (at%) are carried out and discussed. X-ray examinations indicate that the shaping of the TiAl components dose not contain macro casting defects, validating the advantages of this technique. The results are of interest to researchers devoted to technical innovations and modifications for TiAl casting at the industrial scale.The design combines induction skull melting, counter-gravity casting and mold heating a), which facilitates the shaping of the TiAl components b and c), and the decreasing of the defect d) via a controllable process. The results are of interest to researchers devoted to produce high-quality TiAl castings.
      PubDate: 2017-09-25T11:11:37.441471-05:
      DOI: 10.1002/adem.201700526
  • Tensile Strength Evolution and Damage Mechanisms of Al–Si Piston Alloy
           at Different Temperatures
    • Authors: Meng Wang; Jianchao Pang, Yu Qiu, Haiquan Liu, Shouxin Li, Zhefeng Zhang
      Abstract: The Al–Si piston alloys always bear different temperatures because of its peculiar component structure and service condition. Therefore, the tensile strength, elongation to fracture, and corresponding damage mechanisms of Al12SiCuNiMg piston alloys (ASPA) have been investigated with in situ technique at different temperatures. The tensile properties show two-stage tendencies: the former stage (25–280 °C) is determined by easily broken phases with inherent brittleness (such as primary Si), and the fracture behavior presents rapid brittle fracture after reaching the critical stress (about 430 MPa, based on in situ technique and the elastic stress field model). The later one (280–425 °C) is dominated by particles debonding and θphase coarsening. The plastic deformation behavior, dynamic recovery, and flow process become more significant on account of thermal activation. The Considère criterion h = K indicates that the transition of damage behaviors from insufficient local strength to insufficient matrix strength and the corresponding failure model shifts from brittle to ductile fracture. Based on the damage mechanisms, the elastic field model and thermal activation relation model have been established to characterize the strength of the ASPA at different temperature ranges.The tensile properties of Al-Si alloy show two-stage tendencies: the former stage is 25–280 °C and later one is 280–425 °C. Fracture mechanism changes from broken Si (insufficient local strength) at 25 °C to debonding particles (insufficient matrix strength) at 350 °C.The elastic field model and thermally activation relation model have been established to characterize the strength at different temperature ranges.
      PubDate: 2017-09-25T01:52:22.944493-05:
      DOI: 10.1002/adem.201700610
  • Front Cover: Advanced Engineering Materials 9∕2017
    • Abstract: The cover shows a special filter component (200 mm × 200 mm) tested in a steel casting simulator in terms of transfer project T01 before the application in a real steel plant. (Photo credit: Steffen Dudczig, Institute of Ceramic, Glass and Construction Materials, TU Bergakademie Freiberg).
      PubDate: 2017-09-22T01:29:21.384686-05:
      DOI: 10.1002/adem.201770030
  • Editorial
    • Authors: Tobias Fey
      PubDate: 2017-09-22T01:29:21.326738-05:
      DOI: 10.1002/adem.201700707
  • Back Cover: Advanced Engineering Materials 9∕2017
    • PubDate: 2017-09-22T01:29:19.280082-05:
      DOI: 10.1002/adem.201770033
  • Masthead: Adv. Eng. Mater. 9∕2017
    • PubDate: 2017-09-22T01:29:17.502886-05:
      DOI: 10.1002/adem.201770031
  • Editorial
    • Authors: Christos Aneziris
      PubDate: 2017-09-22T01:29:17.427716-05:
      DOI: 10.1002/adem.201700732
  • Contents: Adv. Eng. Mater. 9∕2017
    • PubDate: 2017-09-22T01:29:16.948602-05:
      DOI: 10.1002/adem.201770032
  • High-Entropy Alloy (HEA)-Coated Nanolattice Structures and Their
           Mechanical Properties
    • Authors: Libo Gao; Jian Song, Zengbao Jiao, Weibing Liao, Junhua Luan, James Utama Surjadi, Junyang Li, Hongti Zhang, Dong Sun, Chain Tsuan Liu, Yang Lu
      Abstract: Nanolattice structure fabricated by two-photon lithography (TPL) is a coupling of size-dependent mechanical properties at micro/nano-scale with structural geometry responses in wide applications of scalable micro/nano-manufacturing. In this work, three-dimensional (3D) polymeric nanolattices are initially fabricated using TPL, then conformably coated with an 80 nm thick high-entropy alloy (HEA) thin film (CoCrFeNiAl0.3) via physical vapor deposition (PVD). 3D atomic-probe tomography (APT) reveals the homogeneous element distribution in the synthesized HEA film deposited on the substrate. Mechanical properties of the obtained composite architectures are investigated via in situ scanning electron microscope (SEM) compression test, as well as finite element method (FEM) at the relevant length scales. The presented HEA-coated nanolattice encouragingly not only exhibits superior compressive specific strength of ≈0.032 MPa kg−1 m3 with density well below 1000 kg m−3, but also shows good compression ductility due to its composite nature. This concept of combining HEA with polymer lattice structures demonstrates the potential of fabricating novel architected metamaterials with tunable mechanical properties.High entropy alloy (HEA)-coated nanolattice structures with tunable mechanical properties have been developed, with the characteristics feature sizes spanning from 5 nm to 20 μm.
      PubDate: 2017-09-20T03:11:21.139452-05:
      DOI: 10.1002/adem.201700625
  • Nucleation Crystallography of Ni Grains on CrFeNb Inoculants Investigated
           by Edge-to-Edge Matching Model in an IN718 Superalloy
    • Authors: Wenchao Yang; Pengfei Qu, Lin Liu, Ziqi Jie, Taiwen Huang, Feng Wang, Jun Zhang
      Abstract: In this work, the nucleation crystallography of CrFeNb intermetallic particles as a grain refiner for Ni-based IN718 superalloys is studied using Edge-to-Edge Matching model. Three distinguishable orientation relationships between CrFeNb intermetallic particles and Ni grains are well predicted: [11¯0]Ni∖∖[1¯21¯0]CrFeNb, (111)Ni 1.28° from (0004)CrFeNb, [11¯0]Ni∖∖[1¯21¯0]CrFeNb, (111)Ni 1.32° from (202¯0)CrFeNb, and [11¯0]Ni//[0001]CrFeNb, (111)Ni 0.72° from (202¯0)CrFeNb. The results indicate that CrFeNb intermetallic particles have a strong nucleation potency as an effective grain refiner for Ni-based superalloy and the existence of semi-coherent interfaces between the CrFeNb intermetallic particles and Ni grains. Furthermore, the IN718 superalloy is used to experimentally validate the grain refinement effect of CrFeNb intermetallic particles, showing that its grain size is obviously refined from 8.60 to 1.23 mm. And, the corresponding heterogeneous nucleation mechanism of grain refinement at the atomic level is further identified.The nucleation crystallography of CrFeNb particle on Ni grain is studied using Edge-to-Edge Matching model. Three orientation relationships are predicted to indicate a semi-coherent interface. A relaxation of some atoms may be necessary to minimize the nucleation interface energy. IN718 superalloy is used to validate the grain refinement effect.
      PubDate: 2017-09-20T02:45:26.937527-05:
      DOI: 10.1002/adem.201700568
  • Mechanical Properties of a Novel Zero Poisson's Ratio Honeycomb
    • Authors: Yu Chen; Ming-Hui Fu
      Abstract: In this paper, a novel honeycomb is proposed by embedding a rib into every cell of the existing zero Poisson's ratio (ZPR) configuration, semi re-entrant honeycomb (SRH). Analytical model is developed to investigate the in-plane mechanical properties of the new honeycomb, and the resulting theoretical expressions are compared with the experimental tests and numerical results obtained from two different finite element (FE) models (3D beam model and 3D solid model), leading to a good correlation. FE analysis, analytical modeling, and experimental tests of the new honeycomb show that it can achieve ZPR effect in two principal directions. For further studies, parameters analyses are carried out to explore the dependence of the in-plane mechanical properties versus the geometric parameters. The results show that bending is the dominated deformation model when the new honeycomb is compressed along the x- direction, while stretch controlled in the y- directional compression. It is remarkable that the new proposed honeycomb features superior specific stiffness and more flexible in mechanical properties tailoring compared to the other ZPR honeycombs in the literature. Given these benefits, the new honeycomb may be promising in some practical applications.Honeycombs with zero Poisson's ratio (ZPR) are increasingly used in many important fields because of their unusual properties. A novel ZPR honeycomb is proposed by embedding a rib into every cell of the existing ZPR configuration, semi re-entrant honeycomb (SRH). The new proposed ZPR honeycomb exhibits superior specific stiffness and shows flexible in mechanical properties tailoring. Given these benefits, it may be promising in some applications.
      PubDate: 2017-09-19T01:20:37.058205-05:
      DOI: 10.1002/adem.201700452
  • ZnO Coated Anodic 1D TiO2 Nanotube Layers: Efficient Photo-Electrochemical
           and Gas Sensing Heterojunction
    • Authors: Siowwoon Ng; Petr Kuberský, Milos Krbal, Jan Prikryl, Viera Gärtnerová, Daniela Moravcová, Hanna Sopha, Raul Zazpe, Fong Kwong Yam, Aleš Jäger, Luděk Hromádko, Ludvík Beneš, Aleš Hamáček, Jan M. Macak
      Abstract: The authors demonstrate, in this work, a fascinating synergism of a high surface area heterojunction between TiO2 in the form of ordered 1D anodic nanotube layers of a high aspect ratio and ZnO coatings of different thicknesses, produced by atomic layer deposition. The ZnO coatings effectively passivate the defects within the TiO2 nanotube walls and significantly improve their charge carrier separation. Upon the ultraviolet and visible light irradiation, with an increase of the ZnO coating thickness from 0.19 to 19 nm and an increase of the external potential from 0.4–2 V, yields up to 8-fold enhancement of the photocurrent density. This enhancement translates into extremely high incident photon to current conversion efficiency of ≈95%, which is among the highest values reported in the literature for TiO2 based nanostructures. In addition, the photoactive region is expanded to a broader range close to the visible spectral region, compared to the uncoated nanotube layers. Synergistic effect arising from ZnO coated TiO2 nanotube layers also yields an improved ethanol sensing response, almost 11-fold compared to the uncoated nanotube layers. The design of the high-area 1D heterojunction, presented here, opens pathways for the light- and gas-assisted applications in photocatalysis, water splitting, sensors, and so on.Ultrathin and homogeneous ZnO coatings within high aspect ratio TiO2 nanotubular structure are demonstrated. ALD ZnO coatings within high surface area TiO2 nanotubes layer form a heterojunction with excellent photoelectrochemical activity and good ethanol sensing response. These enhancements are contributed by the passivated surface traps on tube wall, increased light absorption, close match of coating thickness, and Debye length.
      PubDate: 2017-09-19T01:20:26.109066-05:
      DOI: 10.1002/adem.201700589
  • Strategies for Drug Encapsulation and Controlled Delivery Based on
           Vapor-Phase Deposited Thin Films
    • Authors: Alberto Perrotta; Oliver Werzer, Anna Maria Coclite
      Abstract: Vapor-phase deposition methods allow the synthesis and engineering of organic and inorganic thin films, with high control on the chemical composition, physical properties, and conformality. In this review, the recent applications of vapor-phase deposition methods such as initiated chemical vapor deposition (iCVD), plasma enhanced chemical vapor deposition (PE-CVD), and atomic layer deposition (ALD), for the encapsulation of active pharmaceutical drugs are reported. The strategies and emergent routes for the application of vapor-deposited thin films on the drug controlled release and for the engineering of advanced release nanostructured devices are presented.Vapor-phase deposition methods allow the synthesis of (in)organic thin films, with high control on the chemical-physical properties and conformality. In this review, the encapsulation strategies of active drug molecules by means of vapor phase deposition processes are reported. The effects of (pre-) treatment and thin film deposition on controlled drug release and morphology are also reviewed, together with future perspectives and ‘smart’ device applications.
      PubDate: 2017-09-19T00:16:03.700173-05:
      DOI: 10.1002/adem.201700639
  • Sub-Micron Anisotropic InP-based III–V Semiconductor Material Deep
           Etching for On-Chip Laser Photonics Devices
    • Authors: Doris Keh-Ting Ng; Chee Wei Lee, Vivek Krishnamurthy, Qian Wang
      Abstract: Two InP-based III–V semiconductor etching recipes are presented for fabrication of on-chip laser photonic devices. Using inductively coupled plasma system with a methane free gas chemistry of chlorine and nitrogen at a high substrate temperature of 250 °C, high aspect ratio, anisotropic InP-based nano-structures are etched. Scanning electron microscopy images show vertical sidewall profile of 90° ± 3°, with aspect ratio as high as 10. Atomic Force microscopy measures a smooth sidewall roughness root-mean-square of 2.60 nm over a 3 × 3 μm scan area. The smallest feature size etched in this work is a nano-ring with inner diameter of 240 nm. The etching recipe and critical factors such as chamber pressure and the carrier plate effect are discussed. The second recipe is of low temperature (−10 °C) using Cl2 and BCl3 chemistry. This recipe is useful for etching large areas of III–V to reveal the underlying substrate. The availability of these two recipes has created a flexible III–V etching platform for fabrication of on-chip laser photonic devices. As an application example, anisotropic InP-based waveguides of 3 μm width are fabricated using the Cl2 and N2 etch recipe and waveguide loss of 4.5 dB mm−1 is obtained.Two InP-based III-V semiconductor etching recipes are presented for fabrication of on-chip laser photonic devices using inductively coupled plasma system with a methane free gas chemistry. The smallest feature size etched in this work is a nano-ring with inner diameter of 240 nm. InP-based waveguides of 3 μm width fabricated give a waveguide loss of 4.5 dB mm–1.
      PubDate: 2017-09-18T08:06:10.535529-05:
      DOI: 10.1002/adem.201700465
  • Multi-Stable Mechanical Structural Materials
    • Authors: Lingling Wu; Xiaoqing Xi, Bo Li, Ji Zhou
      Abstract: Energy absorbing is an important and desirable property in mechanical and civil engineering. Here, a proof-of-concept method is presented as a new approach to achieve artificial mechanical materials with tunable compressive behavior for energy absorbing constructed from unit cells with a snap fit structure. The artificial structure undergoes a series of stable configurations derived from the sequential insertion of the plug into the groove of the snap fit. Both, experimental and simulation results manifest the multi-stable and tunable mechanical properties of the structure. The mechanical energy dissipated by the proposed structure is demonstrated to be dependent on the lead-in angle of the snap fit and the deflection ratio of the groove, as well as on the coefficient of friction between the plug and the groove of the snap fit. The system designed, herein, exhibits mechanical properties that can be tuned not only by adjusting the geometric parameters, but also by tuning the coefficient of friction between the plug and the groove, allowing the mechanical properties to be tailored post-fabrication. Furthermore, the proposed model can be extended to the macro-, micro-, or nanoscales. These findings provide a simple method to obtain artificial materials with tunable energy absorbing properties, which can be applied in areas such as the design of automobile bumpers and foldable devices that facilitate their transportation.In this paper, the authors proposed a new class of mechanical structural material with multi-stable mechanical properties for energy absorbing and demonstrated its fabrication using Sylgard® 184 silicone. The proposed model is constructed from unit cells having a snap fit structure, which has two stable configurations derived from the insertion of the plug into the groove of the snap fit. During the deformation, the tilting beams store a portion of energy, while the remaining energy is dissipated by the mechanical friction effect between the plug and groove of the snap fit. Besides, the energy absorbed (E_in) and the energy required to break the second equilibrium state (E_out) can be tuned independently. The relationships between the mechanical performance and the geometric parameters of the snap fit are investigated via both simulations and experiments. Adjustable energy absorption properties are obtained by changing the width ratio, the lead-in angle, and the coefficient of friction of the snap fit, which permits a more practicable method to tune the mechanical properties of the structural material. The mechanism proposed, herein, is theoretically scale-independent, that is, the manipulation of the mechanical properties can be extended to the micro- or nanoscale, if appropriate fabrication processes are available. This approach proves to be a low-cost, easily accessible, and reusable method that has a broad application potential in industry, such as in the design of automobile bumper beams, vibration isolation materials, and foldable instruments.
      PubDate: 2017-09-18T08:05:45.553865-05:
      DOI: 10.1002/adem.201700599
  • Antibacterial Efficacy of Sacrifical Anode Thin Films Combining Silver
           with Platinum Group Elements within a Bacteria-Containing Human Plasma
    • Authors: Adham Abuayyash; Nadine Ziegler, Jan Gessmann, Christina Sengstock, Thomas A. Schildhauer, Alfred Ludwig, Manfred Köller
      Abstract: Silver (Ag) dots arrays (64 and 400 dots per mm2) are fabricated on a continuous platinum (Pt), palladium (Pd), or iridium (Ir) thin film (sacrifical anode systems for Ag) and for comparison on titanium (Ti) film (non-sacrifical anode system for Ag) by sputter deposition and photolithographic patterning. The samples are embedded within a tissue-like plasma clot matrix containing Staphylococcus aureus (S. aureus), cultivated for 24 h. Bacterial growth is analyzed by fluorescence microscopy. Among platinum group sacrifical anode elements and a dense Ag sample, only the high Ag ion releasing Ag–Ir system is able to inhibit the bacterial growth within the adjacent plasma clot matrix. This study demonstrates that the antibacterial efficiency of Ag coatings is reduced under tissue-like conditions. However, the new sacrificial anode based Ag–Ir system can overcome this limitation.Sacrificial anode silver dot arrays, fabricated on continuous platinum, palladium, or iridium thin films by sputter deposition and photolithographic patterning are embedded within a tissue-like plasma clot matrix containing growing Staphylococcus aureus. Among these samples or a dense Ag film, only the Ag–Ir dot array is able to inhibit the bacterial growth within the plasma clot matrix.
      PubDate: 2017-09-18T08:00:22.123943-05:
      DOI: 10.1002/adem.201700493
  • Effect of Thermal Oxidation on Microstructure and Corrosion Behavior of
           the PVD Hf-Coated Mg Alloy
    • Authors: Dongfang Zhang; Zhengbing Qi, Binbin Wei, Zhoucheng Wang
      Abstract: Hafnium coatings are fabricated on magnesium alloys by magnetron sputtering and are further submitted to the thermal oxidation treatment at temperature of 200, 300, and 400 °C. The thin hafnium oxide film and new grain boundaries are observed on the hafnium coatings during the appropriate treatment temperature (300 °C). These changes in microstructure result in surface densification, oxidation, and low porosity of the treated coating that significantly decrease its susceptibility to corrosion. Consequently, the thermal oxidation treatment hafnium coating exhibits a more positive corrosion potential, lower corrosion current density, and higher polarization resistance than that of the as-deposited coating using an electrochemical system. Moreover, the enhanced adhesion of the treated coating produced by applying an appropriate treatment temperature facilitates an efficient long-term protection of magnesium alloy.Thermal oxidation as an effective yet feasible post-treatment is conducting on the PVD Hf coated Mg alloy. Surface densification, thin oxide film, and enhanced adhesion are obtained on the post treated coating. As a result, the treated coating exhibits more efficient barrier to corrosive media with positive corrosion potential, low corrosion current density, and high polarization resistance.
      PubDate: 2017-09-18T01:00:38.093829-05:
      DOI: 10.1002/adem.201700556
  • MWCNTs as Conductive Network for Monodispersed Fe3O4 Nanoparticles to
           Enhance the Wave Absorption Performances
    • Authors: Kaili Yu; Min Zeng, Yichao Yin, Xiaojun Zeng, Jue Liu, Ya Li, Wukui Tang, Yu Wang, Jing An, Jun He, Ronghai Yu
      Abstract: Magnetic oxides are widely used as electromagnetic (EM) wave absorbers. To promote the absorption efficiency, tremendous efforts have been contributed to adjusting the composite, structure, and size of magnetic loss materials. Employing carbon materials (CNTs, CF, graphene, PANI) is an efficient way to improve the dielectric loss of the matrix. Anchoring the tiny-monodispersed Fe3O4 nanoparticles (NPs) onto the lightweight multi − walled carbon nanotubes (MWCNTs) leads to improve dielectric loss and impedance matching characteristic. Magnetic Fe3O4 NPs along the one-dimensional nanotubes direction play a good synergetic role with MWCNTs due to the interfacial strong chemical and structure bonding. The as-synthesized Fe3O4/MWCNTs nanocomposites exhibit efficient EM wave absorption characteristics (RL av−10 dB) with a maximum reflection loss of −63.64 dB at 12.08 GHz and a diminutive thickness of only 1.6 mm. The magnetic Fe3O4 NPs show strong chemical and structure bonding with the one-dimensional MWCNTs. This work may show a way to broaden the application of such kinds of lightweight high-performance absorbing materials frameworks.Anchoring the tiny and monodispersed Fe3O4 NPs onto the lightweight MWCNTs results in a strong bonding in Fe3O4/MWCNTs nanocomposites, which exhibit excellent EM wave absorption properties. The MWCNTs can act as the conductive network to enhance the dielectric loss and balance the magnetic loss for good impedance matching.
      PubDate: 2017-09-18T01:00:29.878778-05:
      DOI: 10.1002/adem.201700543
  • 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
  • Hydrogen Trapping in Some Automotive Martensitic Advanced High-Strength
    • Authors: Jeffrey Venezuela; Qingjun Zhou, Qinglong Liu, Mingxing Zhang, Andrej Atrens
      Abstract: Hydrogen permeation experiments are used to investigate hydrogen trapping in commercial automotive martensitic advanced high-strength steels. Hydrogen trapping increases with increasing mechanical strength, as indicated by (i) the decrease in the hydrogen diffusion coefficient, and (ii) the increase in reversible hydrogen trap density. The measured trap densities are in the order of ≈1017– ≈ 1018 cm−3. The relationship between trapping characteristics and HE susceptibility of MS-AHSS is discussed in terms of Hydrogen Enhanced Macroscopic Plasticity (HEMP) and Hydrogen Assisted Micro-fracture (HAM).Reversible trapping of hydrogen by dislocations may explain the hydrogen-influenced behavior in the MS-AHSS: (i) the reduction of the yield strength by the Hydrogen Enhanced Macroscopic Plasticity (HELP) mechanism, and (ii) the occurrence of shear micro-fracture by the Hydrogen Assisted Micro-fracture (HAM) mechanism.
      PubDate: 2017-09-13T13:02:10.393178-05:
      DOI: 10.1002/adem.201700468
  • Fused Deposition Modeling for Unmanned Aerial Vehicles (UAVs): A Review
    • Authors: Helge Klippstein; Alejandro Diaz De Cerio Sanchez, Hany Hassanin, Yahya Zweiri, Lakmal Seneviratne
      Abstract: Additive Manufacturing (AM) is a game changing production technology for aerospace applications. Fused deposition modeling is one of the most widely used AM technologies and recently has gained much attention in the advancement of many products. This paper introduces an extensive review of fused deposition modeling and its application in the development of high performance unmanned aerial vehicles. The process methodology, materials, post processing, and properties of its products are discussed in details. Successful examples of using this technology for making functional, lightweight, and high endurance unmanned aerial vehicles are also highlighted. In addition, major opportunities, limitations, and outlook of fused deposition modeling are also explored. The paper shows that the emerge of fused deposition modeling as a robust technique for unmanned aerial vehicles represents a good opportunity to produce compact, strong, lightweight structures, and functional parts with embedded electronic.Fused deposition modeling (FDM) and Unmanned Ariel vehicles (UAVs), are fast growing technologies, have attracted a great deal of attention. This review studies the process methodology challenges, opportunities, and outlook of FDM and its application in the development of high performance UAVs.
      PubDate: 2017-09-12T02:21:35.040109-05:
      DOI: 10.1002/adem.201700552
  • Threshold Fluence Measurement for Laser Liftoof InP Thin Films by
           Selective Absorption
    • Authors: Antony Jan; Benjamin A. Reeves, Yoeri van de Burgt, Garrett J. Hayes, Bruce M. Clemens
      Abstract: We explore conditions for achieving laser liftoff in epitaxially grown heterojunctions, in which single crystal thin films can be separated from their growth substrates using a selectively absorbing buried intermediate layer. Because this highly non-linear process is subject to a variety of process instabilities, it is essential to accurately characterize the parameters resulting in liftoff. Here, we present an InP/InGaAs/InP heterojunction as a model system for such characterization. We show separation of InP thin films from single crystal InP growth substrates, wherein a ≈10 ns, Nd:YAG laser pulse selectively heats a coherently strained, buried InGaAs layer. We develop a technique to measure liftoff threshold fluences within an inhomogeneous laser spatial profile, and apply this technique to determine threshold fluences of the order 0.5 J cm−2 for our specimens. We find that the fluence at the InGaAs layer is limited by non-linear absorption and InP surface damage at high powers, and measure the energy transmission in an InP substrate from 0 to 8 J cm−2. Characterization of the ejected thin films shows crack-free, single crystal InP. Finally, we present evidence that the hot InGaAs initiates a liquid phase front that travels into the InP substrate during liftoff.In epitaxial laser liftoff, the selective absorption of a bright laser pulse by a buried layer results in the separation of the thin film above it from the substrate below, as shown in the accompanying figure. The wafer can be washed and reused for growth, lowering device costs. The resulting films are single crystal and crack free.
      PubDate: 2017-09-11T10:26:16.695208-05:
      DOI: 10.1002/adem.201700624
  • Grain Refinement through Shear Banding in Severely Plastic Deformed A206
           Aluminum Alloy
    • Authors: Parya Teymoory; Abbas Zarei-Hanzaki, Ehsan Farabi, Hossein Monajati, Hamid Reza Abedi
      Abstract: The present work is conducted to study the microstructure and texture evolutions in an as-cast A206 aluminum alloy after applying severe plastic deformation. Toward this end, the material is severely deformed through accumulative back extrusion (ABE) technique at 200 °C and followed by assessing the room temperature mechanical properties of the products. The macro shear-bands formation in the highly strained regions can result in grain refinement through the geometric dynamic recrystallization mechanism. A significant refinement is also characterized within the micro shear-bands; this is attributed to the intensified substructure development and the occurrence of continuous dynamic recrystallization. The corresponding inverse pole figure maps show similar orientation for these newly refined grains with the parent ones. A random texture is produced through sub-grain rotation to dissimilar orientation at the intersection of micro-bands. The assessment of mechanical properties of the processed materials reveal significant increase in both yield and ultimate tensile strength values. The hardness profiles also demonstrate a relatively homogenous microstructure after three and five ABE passes holding a mean hardness value of 183 Vickers.A206 alloy is severely deformed by accumulative back extrusion (ABE) technique at 200 °C and then the room temperature mechanical properties of the products are scrutinized. Enhancement of these properties is attributed to grain refinement that is caused by the presence of micro and macro-shear bands in the heavily deformed regions of the material.
      PubDate: 2017-09-11T01:46:20.782144-05:
      DOI: 10.1002/adem.201700502
  • Hot Deformation Behavior, Dynamic Recrystallization, and Texture Evolution
           of Ti–22Al–25Nb Alloy
    • Authors: Yang Wu; Hongchao Kou, Bin Tang, Jinshan Li
      Abstract: The hot deformation behavior, dynamic recrystallization, and texture evolution of Ti–22Al–25Nb alloy in the temperature range of 950–1050 °C and strain rate range of 0.001–1 s−1 is investigated by plane-strain compression testing on the Gleeble-3500 thermo-mechanical simulator. The results show that the flow stress decreases with the increase of temperature and decrease of strain rate. Besides, the flow curves appear a serrate oscillation at a strain rate of 0.1 s−1 for all the temperature ranges, which may result from instability such as flow localization or micro-cracking. The flow behavior can be expressed by the conventional hyperbolic sine constitutive equation and the calculated deformation activation energy Q in the (α2 + B2) and B2 regions are 631.367 and 304.812 kJ mol−1, respectively. The microstructure evolution is strongly dependent on the deformation parameters, and dynamic recrystallization (DRX) is the dominant softening mechanism in the (α2 + B2) region, including discontinuous dynamic recrystallization (DDRX), and continuous dynamic recrystallization (CDRX). In addition, the ηbcc-fiber of {110} is the dominant texture component in deformed Ti–22Al–25Nb alloy. It is observed that the weakening of the deformation texture is accompanied by the occurrence of DRX, which can be attributed to the large misorientation between DRX grains and neighboring B2 matrix induced by the rotation of DRX grains toward the preferred slip systems.During the process of compression deformation, dynamic recrystallization (DRX) is the dominant softening mechanism in Ti–22Al–25Nb alloy, including discontinuous dynamic recrystallization (DDRX), and continuous dynamic recrystallization (CDRX). In addition, the ηbcc-fiber of {110} is the dominate texture component and the weakening of the deformation texture is accompanied by the occurrence of DRX.
      PubDate: 2017-09-11T01:45:53.110381-05:
      DOI: 10.1002/adem.201700587
  • Influence of Stress-Aging Processing on Precipitates and Mechanical
           Properties of a 7075 Aluminum Alloy
    • Authors: Y. C. Lin; Yu-Qiang Jiang, Jin-Long Zhang, Xiao-Min Chen
      Abstract: Two-step stress-aging tests, as well as pre-treatment plus stress-aging experiments, are performed on a 7075 aluminum (Al–Zn–Mg–Cu) alloy. Influences of stress-aging parameters on mechanical behavior and fracture mechanism are investigated through uniaxial tensile test and fracture morphology analysis. It is revealed that the stress-aging dramatically influences the mechanical properties and fracture characteristics of the studied alloy, which is contributed to the sensitivity of microstructures to stress-aging. When the alloy undergoes two-step stress-aging, the ultimate tensile strength and yield strength first increase and then decrease with the increased first step stress-aging temperature, while the elongation first decreases and then increases. For the retrogression pre-treated plus stress-aged alloy, the yield strength first increases and then drops with the increased retrogression pre-treatment time, while the ultimate tensile strength almost remains stable. Furthermore, the elongation continuously increases with the increased retrogression pre-treatment time. The observation of fracture morphology indicates that the dimple-type intergranular fracture is the main fracture mechanism for the two-step stress-aged and retrogression pre-treated plus stress-aged alloys.Effects of stress-aging on mechanical behavior and fracture mechanisms of an Al–Zn–Mg–Cu alloy are investigated. It is found that the mechanical strengths of the two-step stress-aged alloy first increase and then decrease with the increased first step stress-aging temperature, while the elongation first decreases and then increases. The dimple-type intergranular fracture is the main fracture mechanism for stress-aged alloys.
      PubDate: 2017-09-07T08:00:52.278529-05:
      DOI: 10.1002/adem.201700583
  • Equivalent Hydrogen Fugacity during Electrochemical Charging of 980DP
           Steel Determined by Thermal Desorption Spectroscopy
    • Authors: Qinglong Liu; Evan Gray, Jeffrey Venezuela, Qingjun Zhou, Clotario Tapia-Bastidas, Mingxing Zhang, Andrej Atrens
      Abstract: Thermal desorption spectroscopy (TDS) is used to analyze hydrogen in 980DP after (i) electrochemical charging, and (ii) gaseous charging. The hydrogen concentration increases with (i) a more negative charging potential and (ii) an increasing hydrogen gas pressure. For charging in 0.1 M NaOH, the hydrogen fugacity for 980DP is similar to that for (i) low interstitial steel, and (ii) MS1500, and is greater than that for the 3.5NiCrMoV steel. This indicates an influence of steel chemistry on the hydrogen evolution reaction. The de-trapping activation energies are 40.5 and 50.2 kJ mol−1, indicating hydrogen traps at boundary defects.The figure shows that, for cathodic hydrogen charging in 0.1 M NaOH, the hydrogen fugacity is similar for the (i) 980DP steel (ii) low interstitial steel, and (iii) MS1500, and was greater than the fugacity for the 3.5NiCrMoV steel. This indicates an influence of steel chemistry, most likely, on the details of the hydrogen evolution reaction.
      PubDate: 2017-09-07T07:41:18.465735-05:
      DOI: 10.1002/adem.201700469
  • A Combined Analytic, Numeric, and Experimental Investigation Performed on
           NiTi/NiTiCu Bi-Layer Composites under Tensile Loading
    • Authors: Milad Taghizadeh; Mahmoud Nili-Ahmadabadi, Mostafa Baghani, Mohammad Hassan Malekoshoaraei
      Abstract: Adjusting mechanical behavior and controlling deformation parameters are significant tasks in designing shape memory components. In this paper, an analytical model describes the deformation behavior of NiTi/NiTiCu bi-layer composites under tensile loading. Different deformation stages are considered based on single mechanical behavior at each stage. Closed-form equations are derived for stress–strain variations of bi-layer composites under uniaxial loading–unloading. Bi-layer composites made via the diffusion bonding method from single layers of NiTi alloy with a composition of Ti-50.7 at.% Ni, as an austenitic layer, and Ti-45 at% Ni-5 at% Cu, as a martensitic layer, are produced by the vacuum arc remelting technique. The tensile behavior of single- and bi-layers is investigated by using loading–unloading experiments to find the nominal stress–strain curves. Numerical simulations are also done by employing Lagoudas constitutive model to simulate stress–strain diagrams. The solutions of the analytical method presented are validated by using the numerical simulations as well as the experimental results. With regard to the results obtained from the analytical modeling, the numerical simulations, and the experiments, it is evident that the bi-layer composites with different thickness ratios provide adjustable mechanical behavior that can be considered in different application designs, for example, actuators equipped with shape memory components.In this paper, an analytical model describes the deformation behavior of NiTi/NiTiCu bi-layer composites under tensile loading. Bi-layer composites are made via diffusion bonding method and their tensile behavior is investigated by using loading-unloading experiments. Numerical simulations are also done by employing Lagoudas constitutive model. The model shows a good agreement with both the experimental and FEM results.
      PubDate: 2017-09-06T23:59:47.460143-05:
      DOI: 10.1002/adem.201700395
  • Measurement of Texture Gradient in Heavily Cold-Drawn Pearlitic Wires
    • Authors: Aurélie Jamoneau; Jean-Hubert Schmitt, Denis Solas
      Abstract: It is well established that cold-drawing of pearlitic wire develops a strong anisotropy due to a preferential orientation of the ferrite phase parallel to the wire axis. The subsequent wire behavior during torsion, which mainly occurs during assembling of drawn wires, is correlated with the texture and its gradient along the wire radius. Although different attempts were made in the past to measure the texture after drawing, it is still challenging since the final wire diameter is on the order of 0.3 mm. The paper presents a simple and robust method to measure the texture gradient by X-ray diffraction. First, to overcome the problems of a composite sample made of parallel wires, an isotropic reference sample is prepared by cycles of austenite transformation and quenching. The texture gradient is measured at different thicknesses by dissolving the external surface of the wires. This allows the investigation of the first 40 μm of depth. Finally, the results are compared with EBSD measurements on a longitudinal cross-section to quantify the influence of the drawing conditions: A flat schedule with constant die angles favors a fiber texture with a weak gradient, while increasing the drawing angle for three dies increases the gradient.An isotropic pearlitic wire is used as a reference with which to correct pole figures obtained by X-ray diffraction on drawn wire surface (R). The textural evolution is measured along the radius via successive surface dissolutions (0.87R and 0.73R). Results are compared to EBSD maps at equivalent depths to quantify the effects of drawing conditions.
      PubDate: 2017-09-06T11:08:21.943881-05:
      DOI: 10.1002/adem.201700279
  • Mechanical Properties, Fatigue Life, and Electrical Conductivity of
           Cu–Cr–Hf Alloy after Equal Channel Angular Pressing
    • Authors: Daria V. Shangina; Vladimir F. Terent'ev, Dmitry V. Prosvirnin, Olga V. Antonova, Natalia R. Bochvar, Mikhail V. Gorshenkov, Georgy I. Raab, Sergey V. Dobatkin
      Abstract: Structure, mechanical, and service properties of a Cu–Cr–Hf alloy after quenching, equal-channel angular pressing (ECAP), and subsequent aging have been studied. The positive effects of ultrafine-grained structure formation (grain/subgrain size of ≈200 nm) during ECAP and strengthening particles precipitation upon subsequent aging at 450 °C on the mechanical and fatigue properties of the alloy are shown. Ultrafine-grained Cu–Cr–Hf alloy after aging shows increasing in the fatigue limit on the basis of 107 cycles from 185 to 375 MPa relative to that of the initial coarse-grained state. The alloy after ECAP and aging also exhibits sufficient elongation to failure (11.4%) and good electrical conductivity (78%IACS).Mechanical and service properties of a Cu–Cr–Hf alloy after equal channel angular pressing (ECAP) and aging have been studied. The positive effects of ultrafine-grained structure and precipitates on the tensile and fatigue properties of the material are shown. The alloy after ECAP and aging exhibits sufficient elongation and good electrical conductivity.
      PubDate: 2017-09-05T07:06:54.713546-05:
      DOI: 10.1002/adem.201700536
  • Uniting Strength and Toughness of Al Matrix Composites with Coordinated
           Al3Ni and Al3Ti Reinforcements
    • Authors: Frederick M. Heim; Yunya Zhang, Xiaodong Li
      Abstract: Hybrid aluminum composites are fabricated in a novel manner to characteristically induce a layer-wise aligned distribution of micro-scale Al3Ni and Al3Ti intermetallic particles that are formed in situ within a ductile Al matrix. The simple and unique Rolling of Randomly Orientated Layer-wise Materials (RROLM) manufacturing methodology enables microstructural tailoring of the intermetallic reinforcing particles to prescribe enhanced crack tip deflection caused by the complex interaction of local veins of reinforcement particles, in an effort to overshadow the classical loss of toughness in large-particle reinforced composites. The complimentary reinforcements and their interface with the Al matrix are revealed to have a gradual transition zone that functions to maintain critical cohesion with the particles and the matrix, empowering the superior load transfer capability of the particles, and reducing microvoid penetration into the matrix. In situ three-point bending observations combined with a local strain field analysis, demonstrate the distinctive crack deflection mechanisms exhibit by the composite. Deviating from the norm, this specialized particle reinforced composite exhibited both strengthening and toughening mechanisms simultaneously, over control samples. The investigated design strategy and model material will assist materials development toward light-weight, stronger, and tougher particle reinforced Al matrix composites.Specialized aluminum matrix composites microstructurally tailored with coordinated dual intermetallic reinforcement particles have been developed though a simple, yet original, methodology, which is specifically designed to enhance toughness and strength simultaneously. Bi-level microcracking and crack tip deflection are expected to have enabled the improved toughness. Hybrid materials like these are anticipated to enable future designs.
      PubDate: 2017-09-05T07:06:25.40406-05:0
      DOI: 10.1002/adem.201700605
  • Current Status and Recent Developments in Porous Magnesium Fabrication
    • Authors: Alicja Kucharczyk; Krzysztof Naplocha, Jacek W. Kaczmar, Hajo Dieringa, Karl U. Kainer
      Abstract: A significant number of studies have been dedicated to the fabrication and properties of metallic foams. The most recent research is focused on metals with low weight and good mechanical properties, such as titanium, aluminum, and magnesium. Whereas the first two are already fairly well studied and already find application in industry, magnesium currently remains at the research stage. The present review covers the studies conducted on fabrication techniques, surface modifications, and properties of porous structures made of magnesium and its alloys.Magnesium foams attract more and more interest due to their low weight, material availability, and mechanical properties. However, due to the flammability and reactivity of magnesium, not all metallic foam manufacturing methods can be used. Therefore, the article summarizes the latest production methods and modifications of already existing ones as well as information about mechanical properties and corrosion resistance.
      PubDate: 2017-09-05T07:00:47.509733-05:
      DOI: 10.1002/adem.201700562
  • Sliding and Migration of Tilt Grain Boundaries in a Mg–Zn–Y
    • Authors: Weiwei Hu; Zhiqing Yang, Hengqiang Ye
      Abstract: Sliding and migration of tilt grain boundaries in a Mg–Zn–Y alloy have been investigated on the atomic scale using aberration-corrected scanning transmission electron microscopy. Grain boundary sliding is accommodated by non-basal dislocations moving along the grain boundary; grain boundary migration is induced by the motion of grain boundary dislocations with synchronized grain boundary diffusion. Simultaneous sliding and migration of tilt boundaries take place in both Mg matrix and long period stacking ordered phases. These results provide evidence for occurrence of grain boundary motion, which may play a role in plasticity of this kind of Mg alloys.Tilt grain boundaries are formed widely as a result of basal slip in Mg alloys. Sliding and migration of tilt grain boundaries take place in both Mg matrix and long period stacking ordered phases in a Mg–Zn–Y alloy. Sliding and migration of tilt grain boundaries accommodated by non-basal dislocations or grain boundary dislocations motion may play important roles in formability of high-strength Mg alloys.
      PubDate: 2017-09-05T07:00:33.282776-05:
      DOI: 10.1002/adem.201700516
  • Reticulated Replica Ceramic Foams: Processing, Functionalization, and
    • Authors: Tobias Fey; Ulf Betke, Stefan Rannabauer, Michael Scheffler
      Abstract: Reticulated ceramic foams are used in a wide range of applications such as filters, catalyst supports, lightweight materials, energy absorptions materials, or as scaffolds for tissue engineering as the most common ones. Based on gaseous foaming processes of polymers, a stochastic distribution of closed pores is obtained. By reticulation processing thin foam windows are removed between cells turning a closed cell into an open cell structure. These foams are used as template for porous ceramics manufacturing: With different processing approaches, for example, with dip coating of a ceramic slurry and a subsequent (multistep) thermal treatment ceramic reticulate foams are obtained. A variety of material properties strongly depend on the cell and strut size, as well on material composition. Functionalization of ceramic foam surfaces (outer surface functionalization), for example, with zeolites or nanosized aggregates lead to an increase of the specific surface area or provides catalytic or heat storage functionality. Filling of struts (inner surface functionalization) may lead to improved mechanical stability or may provide functionalities such as electric conductivity. The present work summarizes the processing steps from the template foam to the final cellular ceramic, functionalization strategies, and the most common characterization techniques.This paper reviews reticulated porous ceramics resulting from a manufacturing process described first in 1963. The focus is set to processing parameters, slurry rheology, and porperties to modification strategies and to characterization methods of foam properties. It may help the readers to identify future research potential.
      PubDate: 2017-09-04T05:35:36.763837-05:
      DOI: 10.1002/adem.201700369
  • Effects of Multi-Scale Patterning on the Run-In Behavior of
           Steel–Alumina Pairings under Lubricated Conditions
    • Authors: Philipp G. Grützmacher; Andreas Rosenkranz, Adam Szurdak, Carsten Gachot, Gerhard Hirt, Frank Mücklich
      Abstract: In nature, many examples of multi-scale surfaces with outstanding tribological properties such as reduced friction and wear under dry friction and lubricated conditions can be found. To determine whether multi-scale surfaces positively affect the frictional and wear performance, tests are performed on a ball-on-disk tribometer under lubricated conditions using an additive-free poly-alpha-olefine oil under a contact pressure of around 1.29 GPa. For this purpose, stainless steel specimens (AISI 304) are modified by micro-coining (hemispherical structures with a structural depth of either 50 or 95 μm) and subsequently by direct laser interference patterning (cross-like pattern with 9 μm periodicity) to create a multi-scale pattern. The comparison of different sample states (polished reference, laser-patterned, micro-coined, and multi-scale) shows a clear influence of the fabrication technique. In terms of the multi-scale structures, the structural depth of the coarser micro-coining plays an important role. In case of lower coining depths (50 μm), the multi-scale specimens show an increased coefficient of friction compared to the purely micro-coined surfaces, whereas larger coining depths (95 μm) result in stable and lower friction values for the multi-scale patterns.The tribological effects of a multi-scale surface patterning technique are investigated. Steel specimens (AISI 304) are modified by micro-coining and subsequently by direct laser interference patterning to create a multi-scale pattern. Depending on the depth of the coined structures, the multi-scale patterns have positive (deep coined-structures) or negative frictional effects (shallow coined structures).
      PubDate: 2017-09-01T14:36:21.552081-05:
      DOI: 10.1002/adem.201700521
  • Electrically Assisted Ultrasonic Nanocrystal Surface Modification of
           Ti6Al4V Alloy
    • Authors: Jun Liu; Sergey Suslov, Shengxi Li, Haifeng Qin, Zhencheng Ren, Gary L. Doll, Hongbo Cong, Yalin Dong, Chang Ye
      Abstract: In this study, an innovative process, electrically assisted ultrasonic nanocrystal surface modification (EA-UNSM), is used to process Ti6Al4V alloy. As compared with traditional UNSM, EA-UNSM results in lower dislocation density and larger grains due to the thermal annealing effect caused by resistive heating. In addition, deeper plastic deformation layer is observed in the electrically assisted case. By supplying mechanical energy and thermal energy simultaneously, a strong dynamic precipitation effect is induced, which generates nanoscale precipitates in the EA-UNSM-treated Ti6Al4V alloy. These nanoscale precipitates can effectively pin dislocations during plastic deformation and thus significantly improve the surface hardness.Electrically assisted UNSM (EA-UNSM) takes advantages of high strain rate plastic deformation and dynamic precipitation, producing a unique structure with nanoscale grains and non-uniformly distributed nano-precipitates. It is observed that the pinning effect exerted by the nanoscale precipitates lead to stronger surfaces, though thermal annealing effect results in grain growth during EA-UNSM.
      PubDate: 2017-08-31T06:17:46.272777-05:
      DOI: 10.1002/adem.201700470
  • Characterization of Microstructure and Mechanical Properties of
           Mg–Y–Zn Alloys with Respect to Different Content of LPSO Phase
    • Authors: Klaudia Horváth; Daria Drozdenko, Stanislav Daniš, Gerardo Garcés, Kristián Máthis, Shae Kim, Patrik Dobroň
      Abstract: The Mg–Y–Zn alloys with different contents of alloying elements are extruded at an extrusion ratio of 4:1 at 350 °C. The microstructure of the alloys is of an inhomogeneous character showing fine grains produced due to dynamic recrystallization and coarse original grains elongated along the extrusion direction (ED). Moreover, Y and Zn form a long-period stacking-ordered (LPSO) phase whose volume fraction increases with their increasing content in the alloy. All investigated alloys exhibit distinct fiber textures with basal planes oriented parallel to ED. It is seen that increasing content of alloying elements leads to a weaker texture. Compression tests with concurrent acoustic emission (AE) measurements are performed along ED at room temperature and a constant strain rate in order to reveal active deformation mechanisms in the alloys and to relate them to their mechanical properties. The AE response is also discussed with respect to the volume fraction of the LPSO phase.Mg–Y–Zn alloys with a various content of alloying elements and thus a different volume fraction of the LPSO phase are investigated during compression along extrusion direction. Acoustic emission (AE) technique is applied for revealing the influence of the volume fraction of the LSPO phase on active deformation mechanisms. The volume fraction of the LPSO phase increases at the expense of the unrecrystallized grains what leads to suppressing the twinning activity.
      PubDate: 2017-08-31T06:10:35.967631-05:
      DOI: 10.1002/adem.201700396
  • Printing Polymer Nanocomposites and Composites in Three Dimensions
    • Authors: Rouhollah Dermanaki Farahani; Martine Dubé
      Abstract: Recent advances in materials science and three-dimensional (3D) printing hold great promises to conceive new classes of multifunctional materials and components for functional devices and products. Various functionalities (e.g., mechanical, electrical, and thermal properties, magnetism) can be offered by the nano- and micro-reinforcements to the non-functional pure printing materials for the realization of advanced materials and innovative systems. In addition, the ability to print 3D structures in a layer-by-layer manner enables manufacturing of highly-customized complex features and allows an efficient control over the properties of fabricated structures. Here, the authors present a brief overview mainly over the latest progresses in 3D printing of multifunctional polymer nanocomposites and microfiber-reinforced composites including the benefits, limitations, and potential applications. Only those 3D printing techniques that are compatible with polymer nanocomposites and composites, that is, materials that have already been used as printing materials, are introduced. The very hot topic of 3D printing of thermoplastic composites featuring continuous microfibers is also briefly introduced.Various state-of-the-art 3D printing methods compatible with polymer nanocomposite/composite materials are briefly reviewed in this mini-review paper. The paper aims to show that the integration of nano- and micro-reinforcements into 3D printing leads to the realization of innovative functional micro- and macro-devices for various applications such as MEMS, microfluidics, engineered materials and composites, microelectronics, tissue engineering, and biosystems.
      PubDate: 2017-08-29T11:28:35.842624-05:
      DOI: 10.1002/adem.201700539
  • High Efficiency Poly(acrylonitrile) Electrospun Nanofiber Membranes for
           Airborne Nanomaterials Filtration
    • Authors: Riyadh Al-Attabi; Ludovic F. Dumée, Lingxue Kong, Jürg A. Schütz, Yosry Morsi
      Abstract: The potential of poly(acrylonitrile) electrospun membranes with tuneable pore size and fiber distributions were investigated for airborne fine-particle filtration for the first time. The impact of solution concentration on final membrane properties are evaluated for the purpose of designing separation materials with higher separation efficiency. The properties of fibers and membranes are investigated systematically: the average pore distribution, as characterized by capillary flow porometry, and thermo-mechanical properties of the mats are found to be dependent on fiber diameter and on specific electrospinning conditions. Filtration efficiency and pressure drop are calculated from measurement of penetration through the membranes using potassium chloride (KCl) aerosol particles ranging from 300 nm to 12 μm diameter. The PAN membranes exhibited separation efficiencies in the range of 73.8–99.78% and a typical quality factor 0.0224 (1 Pa−1) for 12 wt% PAN with nanofibers having a diameter of 858 nm. Concerning air flow rate, the quality factor and filtration efficiency of the electrospun membranes at higher face velocity are much more stable than for commercial membranes. The results suggest that the structure of electrospun membranes is the best for air filtration in terms of filtration stability at high air flow rate.This work investigates the fabrication of poly(acrylonitrile) (PAN) electrospun structures by varying the fiber diameter to offer specific pore size distributions and fiber morphologies for the capture of aerosol fine particles. The influence of the fiber diameter and membrane properties on the pressure drop and penetration depth of the particles is systematically evaluated. The PAN membranes exhibit separation efficiencies in the range of 73.8 to 99.78% and quality factors up to 0.024546 (1 Pa−1) for uniform nanofiber membranes made from 12 wt% PAN solution having an average fiber diameter of 858 nm.
      PubDate: 2017-08-29T11:28:26.629843-05:
      DOI: 10.1002/adem.201700572
  • Effect of Initial Annealing Temperature on Microstructural Development and
           Microhardness in High-Purity Copper Processed by High-Pressure Torsion
    • Authors: Saleh N. Alhajeri; Abdulla I. Almazrouee, Khaled J. Al-Fadhalah, Terence G. Langdon
      Abstract: The effect of the initial annealing temperature on the evolution of microstructure and microhardness in high purity OFHC Cu is investigated after processing by HPT. Disks of Cu are annealed for 1 h at two different annealing temperatures, 400 and 800 °C, and then processed by HPT at room temperature under a pressure of 6.0 GPa for 1/4, 1/2, 1, 5, and 10 turns. Samples are stored for 6 months after HPT processing to examine the self-annealing effects. Electron backscattered diffraction (EBSD) measurements are recorded for each disk at three positions: center, mid-radius, and near edge. Microhardness measurements are also recorded along the diameters of each disk. Both alloys show rapid hardening and then strain softening in the very early stages of straining due to self-annealing with a clear delay in the onset of softening in the alloy initially annealed at 800 °C. This delay is due to the relatively larger initial grain size compared to the alloy initially annealed at 400 °C. The final microstructures consist of homogeneous fine grains having average sizes of ≈0.28 and ≈0.34 µm for the alloys initially annealed at 400 and 800 °C, respectively. A new model is proposed to describe the behavior of the hardness evolution by HPT in high purity OFHC Cu.The effect of the initial annealing temperature on the evolution of microstructure and microhardness in Cu is investigated after processing by HPT. Copper alloys show rapid hardening and then strain softening in the very early stages of straining due to self-annealing. The final microstructures consist of homogeneous fine grains.
      PubDate: 2017-08-29T03:16:15.769868-05:
      DOI: 10.1002/adem.201700503
  • 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
  • Effects of Cu on Microstructures, Mechanical, and Magnetic Properties of
           Fe–Ni–P Alloys Fabricated by Liquid Phase Sintering
    • Authors: Runjian Jiang; Yang Hu, Guodong Cui, Chengsong Zhang, Ai Li
      Abstract: The Fe–Ni–P–Cu alloys with different copper content (0, 0.5, 1, and 2 wt%) are fabricated by liquid phase sintering (LPS) at 950 °C. The nano-Cu powder is mechanically mixed for 90 min with Fe–Ni–P composite powder using the ethanol as the medium. The microstructure, microhardness and compressive properties of Fe–Ni–P–Cu alloys are investigated. The results indicate that the copper is beneficial to improve the mechanical properties of sintered specimens. The sample contains a small amount of γ-(Fe, Ni) phase when the copper content is 1 wt%, which results in its the highest compressive yield strength (948.1 MPa). The highest microhardness of 371 HV is accessible in Fe–Ni–P–Cu alloy with 2 wt% Cu. The fracture surface analysis indicates that sintered specimens with Cu addition exhibit a typical intergranular mode.Fe–Ni–P–Cu alloys are prepared by liquid phase sintering of Ni–P coated iron and Cu powders. Cu addition improves the hardness and compressive yield strength of Fe–Ni–P–Cu alloy. The alloy with 1 wt% Cu has the highest compressive property and magnetic property. Decrease on γ-(Fe,Ni) phase content enhances the property of Fe–Ni–P–1 wt% Cu alloy.
      PubDate: 2017-08-25T02:00:32.123541-05:
      DOI: 10.1002/adem.201700404
  • 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
  • Role of Grain Boundary Sliding in Texture Evolution for Nanoplasticity
    • Authors: Yajun Zhao; Laszlo S. Toth, Roxane Massion, Werner Skrotzki
      Abstract: A new crystal plasticity model is presented to account for the effect of grain boundary sliding (GBS) on texture evolution during large plastic deformation of nanocrystalline materials. In the model, 12 grain boundaries are assigned for each grain and their sliding rates are calculated using Newtonian viscoplasticity. The lattice rotation of the grain interior is computed by taking into account the deformation field modification produced by GBS. The model is employed for predicting the texture evolution in a nanocrystalline Pd–10 at%Au alloy subjected to large strain simple shear, up to a shear strain of 16.8. Two main texture effects due to increasing GBS are identified: high reduction in texture intensity, and tilts of the texture components from their ideal orientations. In the alloy considered, the contribution of GBS to the total strain is identified to be about 30%.A new crystal-plasticity model is proposed to study the effect of grain boundary sliding (GBS) on texture evolution for nanocrystalline materials under large plastic deformation. The GBs for each grain are modeled by flat planes, constructing a polyhedron (shown in the figure). Quantitatively, the role of GBS in texture evolution is found: the randomization of texture and the tilts of the texture components from their ideal positions.
      PubDate: 2017-08-23T12:36:21.474747-05:
      DOI: 10.1002/adem.201700212
  • A Hierarchically Porous Carbon Fabric for Highly Sensitive Electrochemical
    • Authors: Yuan Jiao; Seong Won Cho, Suyoun Lee, Sang Hoon Kim, Seung-Yeol Jeon, Kahyun Hur, Sun Mi Yoon, Myoung-Woon Moon, Aiying Wang
      Abstract: The hierarchically porous carbon fabrics with controlled conductivity and hydrophilicity have been fabricated by dual templating method of soft templates nested on hard templates. A non-woven fabric coated with a solution of F127/resol has been carbonized for the synthesis of both macro-porous structures of 10–15 µm in diameter having meso-porous carbon structures of 4–6 nm, respectively. After carbonization treatment, not only conductivity is significantly improved, the hierarchically porous carbon also shows superhydrophilicity or water-absorbing nature due to mild hydrophilic material and its dual scale roughness. The porous carbon becomes conductive with resistivity widely tuned from 5.4 × 103 Ωm to 3.1 × 10−3 Ωm by controlling the carbonization temperature. As the increased wettability for organic liquids could lead organic molecules deep into carbonized fabrics, the sensitivity of hierarchically porous carbon fabrics benefits the detection for methanol(CH3OH) or hydrogen peroxide (H2O2). This new design concept of hierarchically porous structures having the multi-functionality of high wettability and conductivity can be highly effective for electroanalytical sensors.Hierarchical porous carbon fabrics with controlled conductivity and hydrophilicity have been fabricated by dual templating. The hydrophilicity and conductivity work synergistically, making the porous carbon material a good candidate for electrochemical sensor.
      PubDate: 2017-08-23T12:35:25.573332-05:
      DOI: 10.1002/adem.201700608
  • Durable and Recyclable Superhydrophobic Fabric and Mesh for
           Oil–Water Separation
    • Authors: Shaher Bano; Usama Zulfiqar, Usama Zaheer, Muhammad Awais, Iftikhar Ahmad, Tayyab Subhani
      Abstract: The authors report durable and recyclable nanocomposite superhydrophobic coatings on two different substrates of fabric and mesh as prepared by titania nanoparticles and polydimethysiloxane (PDMS). The felted wool fabric and the steel mesh are initially coated with a thin layer of PDMS, which is followed by the deposition of nanocomposite coating of titania nanoparticles embedded in PDMS. The dual surface modification of two kinds of substrates generates highly hydrophobic surface character, which is retained after durability performance as measured in ultrasonication, sand, and emery paper abrasion tests. Oil–water separation experiments are performed using water mixtures with four oils, that is, n-hexane, toluene, kerosene, and diesel to ensure the industrial applications of prepared composite materials. Moreover, nanocomposite coatings are tested for several cycles of oil–water separation in harsh conditions such as hot water, sodium chloride, and hydrochloric acid. The adopted approach improves the separation performance by inducing durability of the prepared nanocomposite coatings along with introducing recyclable character.Durable, recyclable, and superhydrophobic nanocomposite coatings are prepared on fabric and steel mesh. The coatings comprise titania nanoparticles and polydimethylsiloxane (PDMS). The substrates are initially coated with PDMS, followed by deposition of titania/PDMS nanocomposite coating. The resulting highly hydrophobic materials are utilized for the separation of oil–water mixtures.
      PubDate: 2017-08-21T03:16:12.906094-05:
      DOI: 10.1002/adem.201700460
  • Ag@Sn Core-Shell Powder Preform with a High Re-Melting Temperature for
           High-Temperature Power Devices Packaging
    • Authors: Fuwen Yu; Bin Wang, Qiang Guo, Xin Ma, Mingyu Li, Hongtao Chen
      Abstract: In this paper, the authors propose a highly conductive die attach material based on Ag@Sn powder for power devices operating at high temperatures or in other harsh environments. The preform can be reflowed at 250 °C (18 °C above the Tm of Sn, 232 °C), but the resulting bondline can sustain high temperatures up to 400 °C with a high shear strength due to the high re-melting temperature of the formed Ag3Sn (Tm = 480 °C) after the complete consumption of the outer Sn layers. In addition, the formed bondline exhibits excellent electrical and thermal conductivities due to the embedded Ag particles in the interconnections. The interconnections also exhibit excellent reliability under thermal shock cycling from −55 to 200 °C because of the increased bondline thickness and inherent ductility of the Ag particles embedded in the Ag3Sn.Ag@Sn Core-shell Powder Preforms is successfully prepared, the preforms required only a short time (5 min) reflow processing at 250 °C, but the resulting interconnections can withstand a high temperature up to 480 °C and exhibit excellent electrical and thermal conductivities due to the high density and the embedded Ag particles in the interconnections.
      PubDate: 2017-08-17T08:00:42.206592-05:
      DOI: 10.1002/adem.201700524
  • Effect of Creep and Aging on the Precipitation Kinetics of an Al-Cu Alloy
           after ne Pass of ECAP
    • Authors: Markus Härtel; Philipp Frint, Kevin G. Abstoss, Martin F.-X. Wagner
      Abstract: Recent work shows that severe plastic deformation processes such as ECAP or HPT considerably accelerate the precipitation kinetics of Al-Cu alloys. In this study, the authors analyze how a combination of mechanical load, aging time (and increased plastic strain), and aging temperature affects the precipitation kinetics of an AA2017 alloy after ECAP. After solution annealing, the material is processed by one pass of ECAP (120°-channel angle) at 140 °C. Compressive creep tests are performed on the initial condition and the ECAP-deformed material. The resulting microstructures are studied in detail using electron microscopy. To investigate the influence of mechanical loading, interrupted compressive creep tests are performed and compared with aged samples (produced without any mechanical loading at the same temperature and after the same amount of time). By keeping time and load constant in another set of interrupted compressive creep tests, the influence of temperature is investigated. Our study shows that increasing mechanical loading further accelerates the precipitation kinetics. Temperature accelerates the precipitation kinetics as well, but results in coarser precipitates. The authors also find that different creep strains can lead to the formation of two different regions in the microstructure: regions with only a few coarsened θ-phase precipitates, and regions with numerous, finely dispersed precipitates.The authors analyze how a combination of mechanical load, aging time, and temperature affects the precipitation kinetics of AA2017 after ECAP. The authors find that different creep strains lead to the formation of two different regions in the microstructure: regions (A) with only a few coarsened θ-phase precipitates, and regions (B) with numerous, finely dispersed precipitates.
      PubDate: 2017-08-17T07:50:41.475951-05:
      DOI: 10.1002/adem.201700307
  • Influence of Ultrafine-Grained Layer on Gaseous Nitriding of Large-Sized
           Titanium Plate
    • Authors: Quantong Yao; Jian Sun, Guanglan Zhang, Weiping Tong, Liang Zuo
      Abstract: In this paper, mechanical shot blasting on a large sized titanium plate is conducted to induce severe plastic deformation, which generates an ultrafine-grained surface layer. The effect of an ultrafine-grained layer on nitriding is evaluated at nitriding temperatures from 600 to 850 °C. The structural phases and mechanical property improvements are investigated and compared to those of a coarse-grained specimen by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and mechanical property measurements. The results indicate that an ultrafine-grained layer enhances the nitriding kinetics and produces a thicker nitrided layer than that of a coarse-grained plate at the same gaseous nitriding temperatures. The improved kinetics are attributed to a greater number of grain boundaries and defects introduced into the titanium plate surface by the mechanical shot blasting treatment. Meanwhile, the surface and cross-sectional hardness values improve compared to the coarse-grained plate due to the thicker nitrided layer resulting from deeper nitrogen diffusion.The authors firstly investigat the effect of ultrafine-grained layer on gaseous nitriding of large titanium plate. The results show that the nitrided thickness of the ultrafine-grained plate is thicker than that of the coarse-grained plate at each nitriding temperature, and the greatest difference between the MSB treated and coarse-grained plates occur at 750 °C.
      PubDate: 2017-08-15T02:41:09.106979-05:
      DOI: 10.1002/adem.201700455
  • Phase-Field Modeling of Microstructural Evolution by Freeze-Casting
    • Authors: Tsung-Hui Huang; Tzu-Hsuan Huang, Yang-Shan Lin, Chih-Hsiang Chang, Po-Yu Chen, Shu-Wei Chang, Chuin-Shan Chen
      Abstract: Freeze-casting has attracted great attention as a potential method for manufacturing bioinspired materials with excellent flexibility in microstructure control. The solidification of ice crystals in ceramic colloidal suspensions plays an important role during the dynamic process of freeze-casting. During solidification, the formation of a microstructure results in a dendritic pattern within the ice-template crystals, which determines the macroscopic properties of materials. In this paper, the authors propose a phase-field model that describes the crystallization in an ice template and the evolution of particles during anisotropic solidification. Under the assumption that ceramic particles represent mass flow, namely a concentration field, the authors derive a sharp-interface model and then transform the model into a continuous initial boundary value problem via the phase-field method. The adaptive finite-element technique and generalized single-step single-solve (GSSSS) time-integration method are employed to reduce computational cost and reconstruct microstructure details. The numerical results are compared with experimental results, which demonstrate good agreement. Finally, a microstructural morphology map is constructed to demonstrate the effect of different concentration fields and input cooling rates. The authors observe that at particle concentrations ranging between 25 and 30% and cooling rate lower than −5° min−1 generates the optimal dendrite structure in freeze casting process.A phase-field model is developed to investigate microstructural evolution by the freeze-casting process. Under the assumption that the colloidal particles can be represented by a concentration field, the interfacial condition of mass conservation, the Gibbs-Thomson condition, and particle segregation can be naturally included in the model. The morphology of dendritic ice crystal and accumulation of ceramic particles are accurately captured.
      PubDate: 2017-08-14T01:56:18.93774-05:0
      DOI: 10.1002/adem.201700343
  • Small Y Addition Effects on Hot Deformation Behavior of Copper-Matrix
    • 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
  • Non-Isothermal Simulations of Aluminum Depth Filtration
    • Authors: Cornelius Demuth; Eric Werzner, Miguel A. A. Mendes, Hartmut Krause, Dimosthenis Trimis, Subhashis Ray
      Abstract: The present article addresses the modeling issues, related to the numerical simulation of aluminum depth filtration inside a real filter section in presence of non-negligible temperature variation. The filter structure is obtained by digitizing the computed tomography (CT) scanned data of a characteristic ceramic foam filter. The modeling takes the process conditions of a filtration trial in a pilot casting line into account. The incompressible flow of liquid aluminum is solved by the lattice Boltzmann method (LBM) and the heat transfer is solved by the finite volume method (FVM). The temperature dependences of the viscosity and the density of liquid metal are specifically considered. Although the consideration of buoyancy force significantly affects the fluid flow, the temperature-dependent viscosity plays only a minor role. A Lagrangian tracking of particles is performed for modeling the filtration of inclusions. In accordance with the depth filtration theory, the computational results confirm an exponential decrease in the particle concentration with the filter depth. The overall filtration efficiency is found to remain almost unaffected by both buoyancy and temperature-dependent viscosity. Using the numerically determined filtration coefficient, the filtration efficiency is extrapolated for a real filter of larger length, although the experimental data are underpredicted.This article concerns the numerical modeling of aluminum depth filtration in consideration of temperature variations. In particular, the effects of temperature-dependent density and viscosity of the melt on the flow, heat transfer, and the filtration of nonmetallic inclusions are investigated. The predictions are compared with the filtration efficiency measured during a filtration trial in a pilot casting line.
      PubDate: 2017-07-26T07:40:47.235094-05:
      DOI: 10.1002/adem.201700238
  • Comparative Phenomenological Study of Fracture Behavior of Ceramic and
           Glass Foams under Compressive Stress Using In Situ X-Ray Microtomography
    • Authors: Jana Hubálková; Claudia Voigt, Anne Schmidt, Kirsten Moritz, Christos G. Aneziris
      Abstract: This contribution is dealing with the phenomenological characterization of the cracking and damage of two different brittle foam materials (ceramic foams and glass foams) under compressive load. The compression tests were performed in situ in X-ray microtomograph in order to visualize the formation of single crack and crack patterns in 3D. Successive microtomographic scans at different levels of compression strain provide an insight into the stressed microstructure of the ceramic and glass foams. The linked evaluation of the microtomographic scans and registered load-displacement curves clarify the different mechanical response of ceramic and glass foams. Both, ceramic and glass foams show in the early stages of load nearly elastic response. The compressive loading above the elastic region induces different behavior. Ceramic foams response with local failure of single struts and edges to increasing loading. In case of glass foams, the response is depending on whether the cells are predominantly open or close. Predominantly open cell glass foams features very brittle behavior whereas close cell glass foams show pseudo-ductile behavior with a formation of a crushing band transversal to the loading direction.This study is concerned with the phenomenological characterization of damage of two different brittle foam materials (ceramic and glass foams) under compressive load performed in situ in X-ray microtomograph. The linked evaluation of the microtomographic scans at different levels of compression strain and stress–strain curves clarify the different mechanical response of ceramic and glass foams. While the ceramic foams are subject of successive damage process, the response of glass foams is depending on whether the cells are open or close. Predominantly open cell glass foams features very brittle behavior with a shear deformation band whereas close cell glass foams show pseudo-ductile behavior involving the formation of a compaction deformation band perpendicular to the loading direction.
      PubDate: 2017-07-05T04:31:26.356567-05:
      DOI: 10.1002/adem.201700286
  • Numerical Modeling of Flow Conditions during Steel Filtration Experiments
    • Authors: Amjad Asad; Eric Werzner, Cornelius Demuth, Steffen Dudczig, Anne Schmidt, Subhashis Ray, Christos G. Aneziris, Rüdiger Schwarze
      Abstract: In the present article, the performance and the efficiency of ceramic filters for continuous steel filtration in an induction crucible furnace, which is part of the steel casting simulator facility located at Technische Universität Bergakademie Freiberg, is investigated numerically. In order to achieve this objective, a macro-scale simulation for the melt flow in the crucible is coupled with a pore-scale simulation for the flow inside the ceramic filter that is adequately resolved by its detailed filter geometry, obtained from computed tomography scan images. The considerable influence of the filter on the flow field is indicated from the present results. Moreover, the efficiency of the employed filter is also determined and compared for two pore densities.Numerical simulations are performed in order to determine the filtration efficiency of ceramic filters in an induction crucible furnace. Both pore-scale and macro-scale simulations are coupled in order to achieve this task. The considerable influence of the filter on the flow field is shown in the present article. Moreover, it is indicated that the filtration efficiency of the filters depends on the pore density of the filters.
      PubDate: 2017-07-03T07:07:30.137184-05:
      DOI: 10.1002/adem.201700085
  • Influence of Foam Morphology on Effective Properties Related to Metal Melt
    • Authors: Eric Werzner; Martin Abendroth, Cornelius Demuth, Christoph Settgast, Dimosthenis Trimis, Hartmut Krause, Subhashis Ray
      Abstract: In this article, a numerical study on the sensitivity, related to the performance of open-cell foams used for the depth filtration of liquid metals, on two characteristic morphological properties is presented. Therefore, simulations of fluid flow and particle transport inside an artificial foam structure are carried out, whose porosity and strut shape is varied within a certain expected range. For comparison purposes, however, the simulations are also performed for three typical ceramic foam filters (CFF) with pore densities of 20 and 30 PPI, whose geometries are obtained from CT scans. In order to allow for a comparison between the different structures, a reference length is introduced that relies upon the actual ratio of pores per volume. The evaluation is mainly based on the comparison of the hydraulic tortuosity, the viscous and the inertial permeability coefficients as well as the initial filtration coefficient for alumina inclusions, with their size ranging from of 10 to 40 μm at process conditions typically encountered during the aluminum filtration. It is shown that the ratio of filtration coefficient and pressure drop increases with the porosity, while the material distribution between the struts and the joints is less influential. Finally, the article also provides information on the anisotropy of CFFs and on the transition behavior from steady to unsteady flow in open-cell foams.This article presents a numerical investigation on the sensitivity of permeability, hydraulic tortuosity, and filtration coefficient of open-cell foams used for metal melt filtration regarding their porosity and strut shape for conditions typically observed during the continuous casting of aluminum. The predicted results are compared against three samples of real ceramic foam filters obtained through CT scanning.
      PubDate: 2017-06-13T08:06:18.790058-05:
      DOI: 10.1002/adem.201700240
  • Intermetallic Sludge Formation in Fe Containing Secondary Al–Si Alloys
           Influenced by Cr and Mn as Preparative Tool for Metal Melt Filtration
    • Authors: Björn G. Dietrich; Hanka Becker, Michal Smolka, Andreas Keßler, Andreas Leineweber, Gotthard Wolf
      Abstract: In view of filtration of Fe-enriched intermetallics to decrease Fe content in secondary aluminum alloys, the formation of so-called sludge particles has been investigated depending on dwell time and chemical composition using an AlSi9Cu3 secondary alloy with high Fe content. To evaluate the dwell time dependency, samples are cast into ceramic crucibles and held at 620 °C for varying times. Furthermore, Mn and Cr have been added to the melt in different amounts and the alloys are treated for 6 h at 620 °C. The samples are analyzed using light optical micrographs and image analysis to reveal particle sizes and distribution as well as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD) for phase identification. It is found that the growth of Fe containing sludge particles stagnates after reaching a specific value and is not significantly affected by ultra-long dwell times. Mn addition has a minor effect on the the particle size distribution preserving large particle sizes, whereas Cr addition leads to a smaller sludge particles. Generally, the sludge consists of the cubic α-phase. Additionally in the presence of Cr, Fe, and Cr concentration gradients occur in the cubic α–Al–(Fe,Mn,Cr)–Si phase and the Al13Cr4Si4-phase is contained in the centers of the sludge particles. It is concluded that Mn addition is favored due to larger particle size and higher efficiency to bind Fe in the α-phase than by Cr or Cr and Mn addition.In view of a future application of novel filter materials for filtration of iron containing intermetallic phases so called “sludge” to reduce Fe-content in secondary aluminum alloys, the formation of sludge particles depending on melt treatment and varying amounts of Mn and Cr is investigated.
      PubDate: 2017-06-09T14:46:08.728656-05:
      DOI: 10.1002/adem.201700161
  • Effect of Crucible Material for Ingot Casting on Detrimental Non-Metallic
           Inclusions and the Resulting Mechanical Properties of 18CrNiMo7-6 Steel 
    • Authors: Sebastian Henschel; Johannes Gleinig, Tim Lippmann, Steffen Dudczig, Christos G. Aneziris, Horst Biermann, Lutz Krüger, Anja Weidner
      Abstract: The steel 18CrNiMo7-6 (AISI 4317) is treated in three different crucibles based on carbon-bonded alumina. Non-metallic inclusions in the steel are characterized by means of optical microscopy and scanning electron microscopy. Strength, ductility, and dynamic fracture toughness of the steel are evaluated at different temperatures. Furthermore, fatigue lifetimes in the very high cycle regime are determined. The treatment in a carbon-bonded alumina (A–C) crucible resulted in a relatively high inclusion content involving a high number of duplex inclusions consisting of MnS and Si–Al–O. In contrast, less but large pure MnS inclusions are observed when the steel is treated in carbon-bonded alumina-zirconia-titania crucibles – with or without a coating of carbon nanotubes (AZT–C–n and AZT–C). The steel treated in the A–C crucible exhibits the highest strength and fatigue lifetime, but the lowest energy dissipation. The relatively low inclusion content in the AZT–C treated steel results in high energy dissipation during tensile deformation. However, large MnS inclusions in the AZT–C and AZT–C–n treated steels act as crack initiation sites and reduce the fatigue lifetime. The dynamic fracture toughness is not affected by the different melt treatments. This result is explained by cell-like structures within the material that are characterized by a lower strength and an increased concentration of MnS inclusions.The effect of crucible material on the distribution of non-metallic inclusions in 18CrNiMo7-6 steel (AISI 4317) is studied. The resulting quasi-static strength and ductility, the dynamic fracture toughness, and the fatigue life time are evaluated. The treatment in a carbon-bonded alumina crucible results in lowest ductility due to a relatively high inclusion content. However, the highest fatigue strength is observed for this treatment.
      PubDate: 2017-05-24T08:55:39.10871-05:0
      DOI: 10.1002/adem.201700199
  • Formation of Corundum, Magnesium Titanate, and Titanium(III) Oxide at the
           Interface between Rutile and Molten Al or AlSi7Mg0.6 Alloy 
    • Authors: Anton Salomon; Claudia Voigt, Olga Fabrichnaya, Christos G. Aneziris, David Rafaja
      Abstract: For the filtration of oxide inclusions in aluminum melts, active materials covering the surface of ceramic filters are developed permanently. In this study, corundum (α-Al2O3) filters coated with rutile (TiO2) coatings are exposed to molten aluminum and to aluminum alloy AlSi7Mg0.6, respectively. For pure aluminum, the chemical reactions occurring at the interface between the metal melt and the filter surface are found to lead primarily to the formation of Al2O3 at the surface of the functionalized filter. Al3Ti and Ti2O3 are found as minor phases for long operation times. In the case of aluminum alloy AlSi7Mg0.6, the surface of the TiO2 coatings is covered by MgTiO3. Additional phases are Al2O3 and Al3Ti. One part of the interface reaction experiments is performed on powder mixtures to identify the reaction products, another one on functionalized filters to estimate the reaction kinetics. The experiments are performed in a Spark Plasma Sintering apparatus, which offers high heating rates that are comparable with those in standard cast processes, but impedes the macroscopic flow of the melt in case of the bulk samples. The equilibrium state is concluded from thermodynamic calculations using the CalPhaD method.Interfacial reactions between rutile and molten pure Al or molten AlSi7Mg0.6 alloy are studied. Microstructural analyses are verified by thermodynamic calculations. TiO2 is reduced leading to the formation of corundum with small amounts of intermediate Ti2O3 (pure Al) or intermediate MgTiO3 preceding corundum (AlSi7Mg0.6). Depending on the contact area, the respective oxide formation inhibits the formation of Al3Ti or (Al,Si)3Ti.
      PubDate: 2017-05-22T06:05:30.885238-05:
      DOI: 10.1002/adem.201700106
  • Impact of the Roughness of Alumina and Al2O3–C Substrates on the
           Adhesion Mechanisms in a Model System 
    • Authors: Lisa Ditscherlein; Anne Schmidt, Enrico Storti, Christos G. Aneziris, Urs A. Peuker
      Abstract: To improve metal purity by reducing solid and liquid inclusions, intelligent filters with a functionalized surface are studied for an application in metal melt filtration. Besides special coatings that increase the attraction of inclusions at the filter surface or react with gases inside the melt, also the filter roughness might increase the filtration efficiency. In this study, we investigate the influence of roughness on adhesion forces for hydrophilic and hydrophobic filter surfaces in a water-based model system with an atomic force microscope. In the case of hydrophilic filter substrates, adhesion forces decrease with an increase of roughness whereas on hydrophobic filter surfaces an inverse effect is observed. The primary cause for this is the formation of small cap-shaped bubbles due to poor wetting. To investigate the stability of these bubbles on smooth as well as rough samples of filter material, imaging in contact mode with increasing applied force is performed. On rough surfaces, the bubbles remain stable even at 30–50 nN because of pinning effects.To improve filter material for melt filtration, samples with varying roughness are investigated in a model system via atomic force microscopy. It is observed that the higher the roughness of the samples, the higher the adhesion forces for poor wetting surfaces. Adhesion forces are enlarged by small stable bubbles, which act as capillary bridges between filter and impurity.
      PubDate: 2017-05-18T07:19:10.80864-05:0
      DOI: 10.1002/adem.201700088
  • Functionalized Carbon-Bonded Filters with an Open Porous Alumina Coating:
           Impact of Time on Interactions and Steel Cleanliness 
    • Authors: Anne Schmidt; Anton Salomon, Steffen Dudczig, Harry Berek, David Rafaja, Christos G. Aneziris
      Abstract: Understanding interactions between filter and molten steel is essential to improve the purity of casted products by filtration. Characteristic, in situ formed layers on the surface of carbon-bonded alumina filters result from these interactions. To comprehend their formation, this study illustrates the time dependency of the layer buildup. Therefore, reactions at the filter/steel interface under quasi static conditions are examined using spark plasma sintering (SPS) equipment. Immersion tests in a steel casting simulator, which provides close-to-reality conditions, complement these investigations. Microstructure and phase analyses reveal that interfacial reactions between filter and steel lead to a thin in situ formed layer on the filter surface. During a “reactive” stage, large polycrystalline alumina structures are formed. Thereby, material is transported both from the carbon-bonded material underneath (i.e., gaseous reaction products) and from the molten steel (i.e., precipitating particles and endogenous inclusions) to the filter/steel interface. The formation of these alumina particles comes to an end as soon as the carbon supply, which triggers the dissolution and precipitation processes at the interface, is cut-off. From that point on, endogenous inclusions are deposited on them (“active” stage). The filters were most efficient during the reactive stage, that is, as long as the interfacial reactions take place.Interfacial reactions of molten steel and filter material distinctly influence the filtration performance. We observe that large polycrystalline alumina structures are formed in situ. The required material is supplied as well from the carbon-bonded material underneath (i.e., gaseous reaction products) as from the molten steel (i.e., precipitating particles and endogenous inclusions). During that stage, filtration is most efficient because endogenous inclusions from the steel are entrapped and strongly bound to the filter.
      PubDate: 2017-05-17T08:50:40.412949-05:
      DOI: 10.1002/adem.201700170
  • Interactions between Exogenous Magnesia Inclusions with Endogenous
           Inclusions in a High Alloyed Steel Melt 
    • Authors: Christina Schröder; Undine Fischer, Anne Schmidt, Gert Schmidt, Olena Volkova, Christos G. Aneziris
      Abstract: Interactions between exogenous MgO particles and endogenous inclusions on the surface of a high alloyed steel melt have been investigated in situ in a high temperature confocal laser scanning microscope. Exogenous magnesia particle forms immediately a liquid Mg–Si–Al–Ti–Cr phase surrounding the solid particle. The real attraction forces between the liquid layer surrounding MgO particles and endogenous Al2O3 inclusions are determined in the range of 6 × 10−18 N to 1 × 10−16 N. In contrast to earlier investigations with exogenous Al2O3 particles, lower real attraction forces between exogenous and endogenous particle pairs have been observed in comparison to endogenous inclusions pairs.Interactions between exogenous MgO particles and endogenous inclusions on the surface of a high alloyed steel melt have been investigated in situ in a high temperature confocal laser scanning microscope. Exogenous magnesia particle forms immediately a liquid Mg–Si–Al–Ti–Cr phase surrounding the solid particle. The real attraction forces between the liquid layer surrounding MgO particles and endogenous Al2O3 inclusions are determined in the range of 6 × 10–18 N to 1 × 10–16 N. In contrast to earlier investigations with exogenous Al2O3 particles, lower real attraction forces between exogenous and endogenous particle pairs have been observed in comparison to endogenous inclusions pairs.
      PubDate: 2017-05-11T03:31:02.701399-05:
      DOI: 10.1002/adem.201700146
  • Thermally Induced Formation of Transition Aluminas from Boehmite 
    • Authors: Martin Rudolph; Anton Salomon, Anne Schmidt, Mykhaylo Motylenko, Tilo Zienert, Hartmut Stöcker, Cameliu Himcinschi, Lilit Amirkhanyan, Jens Kortus, Christos G. Aneziris, David Rafaja
      Abstract: Structural changes occurring during the conversion of boehmite over the transient phases γ-, δ- and θ-Al2O3 to corundum were investigated. During the whole transition process, the specific surface area was reduced. The X-ray and electron diffraction experiments revealed that the transition from γ- to θ-Al2O3 is continuous and that it proceeds over different δ-states rather than over a distinct δ-Al2O3 phase. The reduction of the specific surface area was most pronounced prior to the onset of the phase transition from γ-Al2O3 to the first δ-state. In γ-Al2O3, approximately 45% of Al cations were found to be located on tetrahedral sites within a slightly tetragonal distorted oxygen sublattice.The results of selected area electron diffraction, X-ray diffraction, and thermal analysis have shown that the thermally induced phase transitions in metastable alumina phases, which are usually characterized by the sequence γ-, δ-, and θ-Al2O3, can alternatively be described as a continuous process.
      PubDate: 2017-05-02T10:36:38.482924-05:
      DOI: 10.1002/adem.201700141
  • An Approach Toward Numerical Investigation of the Mechanical Behavior of
           Ceramic Foams during Metal Melt Filtration Processes 
    • Authors: Martin Abendroth; Eric Werzner, Christoph Settgast, Subhashis Ray
      Abstract: This article demonstrates an approach for the numerical modeling of open cell ceramic foams, in order to investigate the thermo-mechanical behavior during metal melt filtration processes. The described methods include the creation of the geometric models, the fluid-dynamic simulations of the melt flow using the lattice boltzmann method, and finite element simulations of the ceramic foam under general loads. The paper mainly focuses on the representative geometry generation process, such that the modeled geometry replicates the real foam as far as possible, since high quality models are essential for the quantitative analyses to be reliable. The present parametric studies demonstrate the manner, in which the foam properties may be influenced by changing the geometric and the topological properties, in order to improve the behavior during filtration processes.This article describes a numerical modeling approach to investigate the thermomechanical behavior of ceramic foams during metal melt filtration processes. The described methods cover the creation of the geometric models, the fluiddynamic simulations of the melt flow using the lattice boltzmann method, and subsequent finite element simulations.
      PubDate: 2017-04-25T06:46:24.22171-05:0
      DOI: 10.1002/adem.201700080
  • Interaction of AlSi7Mg with Oxide Ceramics
    • Authors: Beate Fankhänel; Michael Stelter, Claudia Voigt, Christos G. Aneziris
      Abstract: The development of new active filters for the melt filtration in aluminum industry requires investigations of the interaction of aluminum and its alloys with novel filter materials. The requested filter effects require information about the wettability and potential chemical reactions between the filter material and the metal. Wetting experiments (sessile drop technique at 950 °C under vacuum) of an AlSi7Mg alloy on oxide ceramics (Al2O3, MgAl2O4, 3Al2O3 · 2SiO2, TiO2) in two different surface qualities are carried out. The results show that in all cases, the wettability determined in case of a polished substrate is in good agreement to those of the coated substrates representing real filters. The measured differences of the contact angles are caused by the increased roughness of the substrates’ surface primarily. All substrates but the pure Al2O3 form reactive systems in presence of the AlSi7Mg alloy.The results of wetting experiments of an AlSi7Mg alloy on different oxide ceramics (Al2O3, MgAl2O4, 3Al2O3 · 2SiO2, and TiO2) are shown. The ceramics are used in two different surface qualities to imitate the surface of a ceramic foam filter. A non-wetting behavior is detected in all cases. All ceramics but the pure Al2O3 react with the alloy to form an interface consisting of Al and oxygen. Therefore, the values of final contact angles are more influenced by the roughness than by the chemistry of the interface. The chemistry of the filter coatings influences the wetting process in itself.
      PubDate: 2017-04-24T02:05:45.477522-05:
      DOI: 10.1002/adem.201700084
  • Impact of Nanoengineered Surfaces of Carbon-Bonded Alumina Filters on
           Steel Cleanliness 
    • Authors: Enrico Storti; Steffen Dudczig, Jana Hubálková, Johannes Gleinig, Anja Weidner, Horst Biermann, Christos G. Aneziris
      Abstract: Using a special steel casting simulator, carbon-bonded alumina filters are immersed in a steel melt, which contains artificially-generated endogenous alumina particles. Uncoated and MWCNTs-coated ceramic filters are dipped and rotated for 10 and 300 s in the melt at 1 650 °C. Before and after the immersion test, the same samples are analyzed by means of computer tomography, in order to investigate the kinetic of inclusions deposition on the filter surface and possibly to measure the thickness of the in situ formed layers as a function of the immersion time. In addition, samples of the solidified steel are taken after the tests and analyzed by light and electron microscopy. The population of detected inclusions is classified in terms of size and chemistry in order to compare the filtration efficiency of the carbon-bonded filters.Carbon-bonded alumina filters are tested in contact with molten steel containing endogenous inclusions at 1650 °C. Investigations of the steel samples after the test suggest different filtration effects: the MWCNTs-coated filters deliver higher filtration efficiency and are more effective in removing alumina, Mn-spinel, and MnS inclusions than uncoated filters. However, these filters also generate new silicate inclusions and cause inclusion growth.
      PubDate: 2017-04-18T02:40:46.670788-05:
      DOI: 10.1002/adem.201700153
  • Prediction of High Temperature Behavior of Open-Cell Ceramic Foams Using
           an Experimental-Numerical Approach 
    • Authors: Christoph Settgast; Johannes Solarek, Yvonne Klemm, Martin Abendroth, Meinhard Kuna, Horst Biermann
      Abstract: Open-cell ceramic foam filters are used for the casting process of molten metal to reduce the amount of non-metallic inclusions and turbulence of the metal flow. These filters are exposed to high temperatures and loadings. The present work investigates the creep behavior for an artificial and stochastical filter structure, based on high temperature tests of carbon-bonded alumina.Open-cell ceramic foam filters are used for the casting process of molten metal to reduce the amount of non-metallic inclusions and turbulence of the metal flow. These filters are exposed to high temperatures and loadings. The present work investigates the creep behavior for an artificial and stochastical filter structure, based on high temperature tests of carbon-bonded alumina.
      PubDate: 2017-04-03T04:25:34.027481-05:
      DOI: 10.1002/adem.201700082
  • Influence of the Specimen Manufacturing Process on the Strength of
           Carbon-Bonded Alumina (Al2O3–C) 
    • Authors: Henry Zielke; Anne Schmidt, Martin Abendroth, Meinhard Kuna, Christos G. Aneziris
      Abstract: Open cell ceramic foam filters are used for metal melt filtration to reduce non-metallic inclusions. A new generation of multifunctional filters made of carbon-bonded alumina is investigated within the Collaborative Research Center CRC 920. These filters have to withstand high thermal and mechanical loads. Motivated by the problem of the filters integrity, a mechanical characterization of the bulk material is necessary. In the Ball On Three Balls Test (B3B) miniaturized disk-shaped specimens are loaded with a spherically tipped punch until failure occurs. With the help of the measured load displacement curve the fracture stress is calculated and analyzed by means of WEIBULL distribution.The influence of the specimen manufacturing process on the strength of the material and the microstructure has been investigated. The specimens are made of carbon-bonded alumina, which is used for open cell ceramic foam filters for metal melt filtration. The mechanical tests are performed by means of the ball on three balls test (B3B). The results are analyzed by means of Weibull distribution.
      PubDate: 2017-03-23T05:00:41.635574-05:
      DOI: 10.1002/adem.201700083
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