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  Subjects -> COMPUTER SCIENCE (Total: 1969 journals)
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    - COMPUTER SCIENCE (1147 journals)
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COMPUTER SCIENCE (1147 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: 11)
Abakós     Open Access   (Followers: 3)
Academy of Information and Management Sciences Journal     Full-text available via subscription   (Followers: 67)
ACM Computing Surveys     Hybrid Journal   (Followers: 23)
ACM Journal on Computing and Cultural Heritage     Hybrid Journal   (Followers: 8)
ACM Journal on Emerging Technologies in Computing Systems     Hybrid Journal   (Followers: 13)
ACM Transactions on Accessible Computing (TACCESS)     Hybrid Journal   (Followers: 4)
ACM Transactions on Algorithms (TALG)     Hybrid Journal   (Followers: 16)
ACM Transactions on Applied Perception (TAP)     Hybrid Journal   (Followers: 6)
ACM Transactions on Architecture and Code Optimization (TACO)     Hybrid Journal   (Followers: 9)
ACM Transactions on Autonomous and Adaptive Systems (TAAS)     Hybrid Journal   (Followers: 7)
ACM Transactions on Computation Theory (TOCT)     Hybrid Journal   (Followers: 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: 12)
ACM Transactions on Computing Education (TOCE)     Hybrid Journal   (Followers: 3)
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: 19)
ACM Transactions on Intelligent Systems and Technology (TIST)     Hybrid Journal   (Followers: 9)
ACM Transactions on Interactive Intelligent Systems (TiiS)     Hybrid Journal   (Followers: 4)
ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP)     Hybrid Journal   (Followers: 10)
ACM Transactions on Reconfigurable Technology and Systems (TRETS)     Hybrid Journal   (Followers: 7)
ACM Transactions on Sensor Networks (TOSN)     Hybrid Journal   (Followers: 8)
ACM Transactions on Speech and Language Processing (TSLP)     Hybrid Journal   (Followers: 10)
ACM Transactions on Storage     Hybrid Journal  
ACS Applied Materials & Interfaces     Full-text available via subscription   (Followers: 21)
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: 10)
Advanced Engineering Materials     Hybrid Journal   (Followers: 24)
Advanced Science Letters     Full-text available via subscription   (Followers: 5)
Advances in Adaptive Data Analysis     Hybrid Journal   (Followers: 8)
Advances in Artificial Intelligence     Open Access   (Followers: 14)
Advances in Artificial Neural Systems     Open Access   (Followers: 4)
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: 3)
Advances in Data Analysis and Classification     Hybrid Journal   (Followers: 53)
Advances in Engineering Software     Hybrid Journal   (Followers: 25)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 9)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 23)
Advances in Human-Computer Interaction     Open Access   (Followers: 19)
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: 35)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Advances in Technology Innovation     Open Access  
AEU - International Journal of Electronics and Communications     Hybrid Journal   (Followers: 8)
African Journal of Information and Communication     Open Access   (Followers: 6)
African Journal of Mathematics and Computer Science Research     Open Access   (Followers: 4)
Air, Soil & Water Research     Open Access   (Followers: 7)
AIS Transactions on Human-Computer Interaction     Open Access   (Followers: 6)
Algebras and Representation Theory     Hybrid Journal   (Followers: 1)
Algorithms     Open Access   (Followers: 9)
American Journal of Computational and Applied Mathematics     Open Access   (Followers: 3)
American Journal of Computational Mathematics     Open Access   (Followers: 4)
American Journal of Information Systems     Open Access   (Followers: 6)
American Journal of Sensor Technology     Open Access   (Followers: 2)
Anais da Academia Brasileira de Ciências     Open Access   (Followers: 2)
Analog Integrated Circuits and Signal Processing     Hybrid Journal   (Followers: 5)
Analysis in Theory and Applications     Hybrid Journal  
Animation Practice, Process & Production     Hybrid Journal   (Followers: 5)
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Data Science     Hybrid Journal   (Followers: 8)
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: 13)
Applied Categorical Structures     Hybrid Journal   (Followers: 2)
Applied Clinical Informatics     Hybrid Journal   (Followers: 1)
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: 31)
Applied Medical Informatics     Open Access   (Followers: 9)
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: 4)
Archive of Numerical Software     Open Access  
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 4)
Artifact     Hybrid Journal   (Followers: 2)
Artificial Life     Hybrid Journal   (Followers: 5)
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: 8)
Automation in Construction     Hybrid Journal   (Followers: 6)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 7)
Basin Research     Hybrid Journal   (Followers: 3)
Behaviour & Information Technology     Hybrid Journal   (Followers: 52)
Bioinformatics     Hybrid Journal   (Followers: 232)
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: 16)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 31)
Briefings in Bioinformatics     Hybrid Journal   (Followers: 45)
British Journal of Educational Technology     Hybrid Journal   (Followers: 119)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
c't Magazin fuer Computertechnik     Full-text available via subscription   (Followers: 1)
CALCOLO     Hybrid Journal  
Calphad     Hybrid Journal  
Canadian Journal of Electrical and Computer Engineering     Full-text available via subscription   (Followers: 12)
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)
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: 13)
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: 18)
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: 47)
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  
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computational Cognitive Science     Open Access   (Followers: 1)
Computational Complexity     Hybrid Journal   (Followers: 4)
Computational Condensed Matter     Open Access  
Computational Ecology and Software     Open Access   (Followers: 8)
Computational Economics     Hybrid Journal   (Followers: 9)
Computational Geosciences     Hybrid Journal   (Followers: 12)
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: 27)
Computer     Full-text available via subscription   (Followers: 78)
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: 8)
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: 13)
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: 10)
Computer Science Education     Hybrid Journal   (Followers: 12)
Computer Science Journal     Open Access   (Followers: 20)
Computer Science Master Research     Open Access   (Followers: 9)
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]   [24 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  [1582 journals]
  • Sandwich Structures Consisting of Aluminum Foam Core and Fiber Reinforced
           Plastic Top Layers 
    • Authors: Drebenstedt Claudia; Susi Rybandt, Drossel Welf-Guntram, Trautmann Maik, Wagner Guntram
      Abstract: Thinking of new approaches for light weight design with sandwiches, the combination of aluminum foam as core and fiber reinforced plastics as top layers can be a good way to increase the light weight aspect and combine advantages of both materials. For structural applications, often a high bending stiffness and a good damping capability in the combination with the lightweight aspect are needed. For these new sandwiches, especially, the bonding properties are crucial for later applications. Therefore, investigations regarding the bonding properties of the combination of the two components are carried out. The objective is to find a way of combining these materials without adhesives. Different ways of composite manufacturing are tested and compared according to DIN 53292: “testing of sandwiches; tensile test perpendicular to the faces”. Furthermore, different pretreatments of the foam core are compared. These include sandblasting with a chemically modified blasting material, a structure included by a modification of the foaming tool, and untreated foam for comparison reasons to the state of the art. It is found that the structure induced during the foaming step is suitable for adhesive bonding, but not for the other processes. Better results can be expected by further adaption of the implemented structure. The best results in the compression molding process are obtained with the sandblasted foam cores.Aluminum as core and fiber reinforced thermoplastic top layers are combined by compression molding to a new sandwich structure without additional adhesives. Evaluations by tensile tests regarding the bonding depending on the surface pretreatments are conducted. Finally, a demonstrator is realized.
      PubDate: 2017-05-23T04:05:57.298217-05:
      DOI: 10.1002/adem.201700066
       
  • 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
       
  • High-Speed Roll-to-Roll Hot Embossing of Micrometer and Sub Micrometer
           Structures Using Seamless Direct Laser Interference Patterning Treated
           Sleeves 
    • Authors: Andreas Rank; Valentin Lang, Andrés Fabián Lasagni
      Abstract: In this study, we present a seamless high-speed roll-to-roll hot embossing process using a direct laser interference patterned nickel sleeve as a mold. Line-like patterns with spatial periods of 5.0, 3.9, and 1.5 μm and structure heights of 572, 325, and 141 nm, respectively are used for imprinting PET-foils. The influence of the web speed on the cavity filling and consequently on the structure height and homogeneity of the fabricated patterns is studied. The web speed is varied between 2 and 50 m min−1. For the 5.0 and 3.9 μm periods, a decrease in structure height with the web speed occurs, while for the 1.5 μm period the structure height remains constant in the tested interval. Also a decrease in homogeneity is observed with increasing web speed. Finally, an analytical model, based on the Navier–Stokes equation and Hertzian contact pressure, is used to explain the experimental results. The experimental data are in good agreement with the calculated theoretical values.A seamless high-speed Roll-to-Roll hot embossing process using a direct laser interference patterned Nickel sleeve as a mold is presented. Line-like periodic patterns with spatial periods of 5.0, 3.9, and 1.5 µm are fabricated directly on metallic sleeves using a two-beam configuration interference set-up. The influence of the web speed on the cavity filling and consequently on the structure height of the patterns produced on the PET foils is analyzed, for web speeds between 2 and 50 m min–1. An analytical model, based on the Navier–Stokes equation and Hertzian contact pressure, is used to explain the experimental results.
      PubDate: 2017-05-22T06:00:40.806103-05:
      DOI: 10.1002/adem.201700201
       
  • On the Indentation Resistance of a PC Layer on PVC Foam Substrate 
    • Authors: Adam M. Boyce; Vikram S. Deshpande, Norman A. Fleck
      Abstract: The indentation response of a polycarbonate face sheet bonded to a PVC foam substrate is investigated experimentally and numerically. The deformation mode involves foam crushing, and membrane stretching of the PC layer at large indenter displacements; this is quantified using optical strain measurement techniques. The bottom corners of the foam substrate lifts off its underlying support when the foam layer is sufficiently thin. Peak load is dictated by tensile failure of the foam on the bottom face. Finite element simulations suggest that a deep foam core prevents this lift-off and results in a greater load carrying and energy absorption capacity.The indentation response of a polycarbonate face sheet bonded to a PVC foam substrate is investigated experimentally and numerically. The deformation mode involves foam crushing, and membrane stretching of the PC layer at large indenter displacements; this is quantified using optical strain measurement techniques. The bottom corners of the foam substrate lifts off its underlying support when the foam layer is sufficiently thin. A deep foam core prevents this lift-off and results in a greater load carrying and energy absorption capacity.
      PubDate: 2017-05-22T06:00:30.223866-05:
      DOI: 10.1002/adem.201700075
       
  • Front Cover: Advanced Engineering Materials 5∕2017
    • Abstract: The background of this cover image illustrates chemical vapor infiltration process of pyrocarbon deposited on the surface of carbon fiber. The diagram in the foreground shows the microstructure of carbon fiber and pyrocarbon at different infiltration temperatures observed by a polarized microscope. It can be seen that the texture of pyrocarbon deposited by pressuregradient chemical vapor infiltration is homogenous and can be controlled, as reported in article number 1600329 by Fu Qin Zhang and co-workers.
      PubDate: 2017-05-22T03:08:27.079123-05:
      DOI: 10.1002/adem.201770015
       
  • Masthead: Adv. Eng. Mater. 5∕2017
    • PubDate: 2017-05-22T03:08:21.773948-05:
      DOI: 10.1002/adem.201770016
       
  • Contents: Adv. Eng. Mater. 5∕2017
    • PubDate: 2017-05-22T03:08:21.672374-05:
      DOI: 10.1002/adem.201770017
       
  • Novel Composite Foam Concept for Head Protection in Oblique Impacts 
    • Authors: Yasmine Mosleh; Jos Vander Sloten, Bart Depreitere, Jan Ivens
      Abstract: Rotational acceleration experienced by the head during oblique impacts is known to cause traumatic brain injuries. It is hypothesized that shear properties of a foam layer, used for head protection (e.g., protective helmet liners, headliners in cars) can be related to the extent of rotational acceleration transmitted to the head. Furthermore, it is hypothesized that by introducing anisotropy in a foam layer, rotational acceleration can be mitigated. In this study, an anisotropic composite foam concept is proposed to mitigate head rotational acceleration, hence reducing the risk of traumatic brain injuries. The composite foam concept introduces anisotropy in a foam at the “macro level”, combining different densities of foam in layered and quasi-fiber/matrix configurations. The performance of expanded polystyrene (EPS) composite foams in quasi-static compression and combined shear-compression loading and also linear and oblique impact experiments, has been compared with the performance of single layer EPS foam of similar thickness and density. The results of oblique head impact have been analyzed by global head injury criteria such as HIC, HICrot, and HIP. The composite foam concept demonstrates a great potential to be utilized in applications such as protective helmets due to the significant mitigation of brain injury risk.In this study, an anisotropic composite foam concept is proposed to mitigate head rotational acceleration, hence reducing the risk of traumatic brain injuries in oblique impacts. The composite foam concept introduces anisotropy in a foam at the “macro level,” combining different densities of foam in layered and quasi-fiber/matrix configurations. This concept can be used, for example, for helmets with complex shapes.
      PubDate: 2017-05-19T06:10:37.998045-05:
      DOI: 10.1002/adem.201700059
       
  • 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
       
  • Size Effects in Continuous Drive Friction Welded Spray-Compacted
           Hypereutectic Al–Si Alloys 
    • Authors: Jian Feng; Marc Wettlaufer
      Abstract: Spray-compacted hypereutectic Al–Si alloy is one of the most important lightweight materials for casting components in electric vehicles. Size effects in such alloys jointed by continuous drive friction welding have been investigated by connecting the interfacial microstructure with the joint strength. The nature of phases present, the topology, and the dispersion of particles have been examined carefully. The mechanical properties of joints have been characterized by transverse tensile tests, microhardness tests, XRD residual stress measurements, and finite element simulations. Size effects on the strengthening of the joint strength and the fracture of particles have been evaluated qualitatively and quantitatively. It has been confirmed that the micromechanical strengthening, which is related to the average particle size d and proportional to d−0.5, and the residual stress together determine the joint strength. By means of the fracture-mechanical analysis, a lower and an upper limit of the particle size have been defined to assess whether a particle can be refined or not during continuous drive friction welding.Size effects in spray-compacted hypereutectic Al–Si alloys jointed by continuous drive friction welding have been investigated qualitatively and quantitatively by connecting the interfacial microstructure with the joint strength. The micromechanical strengthening, which is related to the average particle size d and proportional to d−0.5, and the residual stress evaluated by XRD residual stress measurements and finite element simulation, together determine the joint strength.
      PubDate: 2017-05-18T06:55:53.616329-05:
      DOI: 10.1002/adem.201700128
       
  • Fabrication of Copper Surfaces with Structures Mirroring Those of Wood via
           Electroplating and Their Hydrophobic Properties 
    • Authors: Tianchi Wang; Xu Feng, Jian Kong, Chingping Wong
      Abstract: Superhydrophobic metallic surfaces have a wide range of applications; therefore, their fabrication has drawn widespread attention. The cross-section of wood has a tubular porous structure and exhibits hydrophobic properties. In this study, inspired by the hydrophobic properties of wood, we electroplated copper on porous wood charcoal surfaces to obtain a superhydrophobic copper surface possessing a structure mirroring that of wood in areas in contact with the wood charcoal. This study used pinewood and Fraxinus mandschurica as templates, which are first sintered under oxygen-free conditions to obtain wood charcoal that retains the porous structure of wood. A thick layer of copper is then electroplated onto the surfaces of the porous carbon. After the copper layer is peeled off, it is found that the copper surface in contact with the porous carbon have formed a microstructure that is a mirror image of the natural structure of wood. This copper surface exhibited excellent levels of hydrophobicity after fluorosilane modification, with contact angles as high as 150°.Wood shows hydrophobic properties, which should be attributed to the porous structure of the wood. Inspired by wood, we electroplate copper on porous wood charcoal surface to obtain a copper surface possessing a structure mirroring that of wood. This mirror structure helps copper surface to obtain superhydrophobic property.
      PubDate: 2017-05-18T06:55:50.885917-05:
      DOI: 10.1002/adem.201700147
       
  • Regenerative Polymeric Coatings Enabled by Pressure Responsive Surface
           Valves 
    • Authors: Ryan C. R. Gergely; Nancy R. Sottos, Scott R. White
      Abstract: Protective coatings safeguard the underlying substrate material from environmental attack and are critical for operating in harsh conditions. Self-healing materials have been developed for the autonomous repair of damage in coatings. This work demonstrates a regenerative coating system that is a simplified synthetic analog of skin. A protective UV curable coating reforms with properties identical to the native coating after complete removal. An integrated surface valve prevents premature curing of healing agent contained within a vascular substrate prior to damage-triggered release, facilitating recovery from repeat damage. The protective coating reforms when exposed to simulated sunlight.A protective polymeric coating is regenerated in response to abrasive damage. Abrasion exposes the underlying vasculature, and UV curable epoxy healing agent is delivered to the site of damage via a pressure responsive surface valve. The protective coating is reformed when exposed to simulated sunlight.
      PubDate: 2017-05-18T01:39:04.90776-05:0
      DOI: 10.1002/adem.201700308
       
  • Simultaneous Fast Deformation and Solidification in Supercooled Liquid
           Gallium at Room Temperature 
    • Authors: Zhenwei W. Yu; Yuchen C. Chen, Frank F. Yun, Xiaolin L. Wang
      Abstract: The authors demonstrate that it is possible to transform a supercooled liquid metal at room temperature into a variety of shapes in solids by combined liquid metal deformation and induced crystallization from the supercooling state. The authors discover that both reversible deformation and irreversible deformation can be achieved simultaneously for supercooled liquid gallium in alkaline or acid electrolytes by using electrodes that are non-wetted or wetted with liquid gallium, respectively. Our findings on the simultaneous deformation and solidification offer a novel approach to controlled patterning and solidification of supercooled liquid gallium at room temperature.Controlling the shape of liquid metals is still a big challenge. Simultaneous deformation and solidification of supercooled liquid gallium is discovered by using an electric field in alkaline or acid electrolytes, which offer a novel approach to controlled patterning and solidification of supercooled liquid gallium at room temperature.
      PubDate: 2017-05-18T01:38:52.178836-05:
      DOI: 10.1002/adem.201700190
       
  • 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
       
  • Microstructural and Mechanical Characterization of Aluminum Matrix
           Composites Produced by Laser Powder Bed Fusion 
    • Authors: Alberta Aversa; Giulio Marchese, Massimo Lorusso, Flaviana Calignano, Sara Biamino, Elisa P. Ambrosio, Diego Manfredi, Paolo Fino, Mariangela Lombardi, Matteo Pavese
      Abstract: Laser powder bed fusion is one of the most widely used additive manufacturing process owing to its ability to produce functional near net shape metal components. This paper focuses on the microstructural and mechanical characterization of four aluminum matrix composites produced by laser powder bed fusion using AlSi10Mg as matrix with four different ceramic particles. On the basis of the building parameters, composites present specific microstructural features able to influence the strengthening mechanisms and, consequently, their mechanical and thermal properties. It is demonstrated that, in order to obtain dense materials, in composite processing, it is indispensable to use energy densities which are higher than that of the matrix. This change in process parameters probably implies a different heat profile in the part during the building process, with a consequent increase in cell size and decrease in yield strength of the MMCs with respect to the pure aluminum.This work investigates the feasibility and the properties of AlSi10Mg matrix composites produced by laser powder bed fusion. It is clarified that high energy densities are required in order to obtain dense composites. The building parameters strongly influence composite microstructures, with evident consequences on their mechanical properties.
      PubDate: 2017-05-17T08:50:36.636005-05:
      DOI: 10.1002/adem.201700180
       
  • Highly Selective Adsorbent and Photacatalytic Material for Industrial
           Wastewater Treatment 
    • Authors: Vassilios Binas; Aggelos Philippidis, Apostolos Zachopoulos, George Kiriakidis
      Abstract: Advanced multifunctional sponge-type materials are obtained following chemical treatment of a Visible Light Photocatalyst (VLP) with an alkali aqueous solution under selected conditions. The resulting multifunctional material is fully characterized by XRD, SEM/EDX, TEM, FT-IR, RAMAN, and UV-Vis. It is found that the resulting material has high affinity to cationic dyes such as methylene blue (MB) and rhodamine 6G (Rh6G) and, thus may be employed as an environmental selective adsorbant for industrial wastewaters consisted of different mixtures of anionic and cationic dyes. On the other hand, this “sponge” like material if activated under visible light irradiation exhibits high photocatalytic activity for the decomposition of methylene blue in a solid state.The paper investigates an advanced multifunctional sponge type material suitable for novel membranes for industrial wastewater treatment, which could selectively adsorb pollutants and then recovery the clean membrane with exposure to visible light irradiation.
      PubDate: 2017-05-17T08:40:40.85499-05:0
      DOI: 10.1002/adem.201600661
       
  • Impact of Slurry Composition on Properties of Cellular Alumina: A Computed
           Tomographic Study 
    • Authors: Ulf Betke; Sebastian Dalicho, Stefan Rannabauer, Alexandra Lieb, Franziska Scheffler, Michael Scheffler
      Abstract: Fine-pored, 45 ppi (pores per linear inch) alumina foams are prepared from ceramic slurries with varying contents of additives (deflocculant, binder) and solid loading following a standardized procedure. Rheological key parameters (yield stress, high-shear viscosity) of the respective slurries are determined by approximation of the experimental flow curves with appropriate rheological models. The resulting ceramic foams are characterized by computed tomography (CT) followed by a morphometric analysis of the reconstruction volume data. The main scope of the work involves the development of a procedure to reliably define the binarization threshold during these morphometric calculations, which is based on the analysis of the differential course of the total porosity results from calculations performed at varying binarization threshold values (“differential thresholding”). A very good match of the CT porosity results with experimental data is achieved, despite the unfavorable CT voxel resolution to foam structure fineness relation. The CT evaluation results are finally correlated to the rheological properties of the respective slurries used in foam manufacturing. The dominant slurry composition parameters are the weight fraction of the ceramic powder and the binder concentration. Increasing binder and solid content result in an increased yield stress and viscosity of the respective dispersion and consequently in a decreased porosity and cell size of the finally manufactured cellular ceramic.Fine-pored, 45 ppi alumina ceramic foams are prepared by the Schwartzwalder method from the respective ceramic dispersions. For these, the slurry composition is varied and its influence on the rheological parameters is investigated. The resulting foams are characterized by micro computed tomography including a new approach for the void  material segmentation. Finally, the µ-CT results are correlated to the rheological parameters of the slurries used in foam preparation.
      PubDate: 2017-05-17T08:40:28.317666-05:
      DOI: 10.1002/adem.201700138
       
  • Lamellar Ceramic Semicrystalline-Polymer Composite Fabricated by Freeze
           Casting 
    • Authors: Jiacheng Huang; Zhe Xu, Salvador Moreno, Seyedreza Morsali, Zhong Zhou, Soheil Daryadel, Mahmoud Baniasadi, Dong Qian, Majid Minary-Jolandan
      Abstract: Understanding the role of ductile polymer phase in mechanical behavior of bioinspired hybrid composites is an important step toward development of materials with damage tolerant properties. Herein, the authors report on fabrication and characterization of a bioinspired lamellar composite by incorporation of a semicrystalline polymer into a freeze casted scaffold. The elastic modulus and ductility of the polymer phase can be changed by more than three and 55 times, respectively, in addition to 42 folds decrease in modulus of toughness, by thermal annealing post-processing, after infiltration into the freeze casted ceramic scaffold. The results show that although polymer phase affects the fracture toughness and flexural behavior of the composite, the drastic changes in mechanical properties of the polymer phase has only marginal effect in the resulted properties of the composite. The authors use in situ SEM experiments and finite element simulation to investigate the deformation mechanism and the effect of the polymer phase on the distribution of stress in the fabricated composites.Directional freeze casting and vacuum infiltration is used to fabricate lamellar ceramic-polymer composites using ceramic micro-platelets and a semicrystalline polymer. Effect of thermal annealing on the morphology and properties of the polymer phase and its effect on mechanical properties of the fabricated composited is investigated.
      PubDate: 2017-05-15T11:50:45.997844-05:
      DOI: 10.1002/adem.201700214
       
  • Fatigue and Fracture Reliability of Shell-Mimetic PE/TiO2 Nanolayered
           Composites 
    • Authors: Y. J. Yang; B. Zhang, H. F. Tan, X. M. Luo, G. P. Zhang
      Abstract: Shell-mimetic (PE/TiO2)4 nanolayered composites stacked alternatively by 20 nm-thick PE layers and 55 nm-thick nanocrystalline TiO2 layers are synthesized by a combination of the layer-by-layer self-assembly and the chemical bath deposition methods. The critical cracking strain and the apparent fracture energy of the bio-mimetic nanolayered composites are determined as 0.56% and 0.98 J m−2, respectively, by the simply supported beam bending testing. Fatigue properties of the (PE/TiO2)4 nanolayered composites are evaluated by the dynamic bending testing method. The critical fatigue strain amplitude corresponding to the lowest strain amplitude for fatigue cracking of the present (PE/TiO2)4 NLCs is 0.0853%, which is much lower than the critical cracking strain (0.56%) under monotonic bending. The finding indicates that the potential fatigue threat to the long-term reliability of the bio-mimetic nanolayered composites needs to be concerned.Shell-mimetic (20 nm-PE/55 nm-TiO2)4 nanolayered composites are synthesized. The critical strain amplitude for cracking of the composites is 0.0853% under fatigue loading, being much lower than that (0.56%) under monotonic bending. The potential fatigue threat to the long-term reliability of the bio-mimetic nanolayered composites needs to be concerned.
      PubDate: 2017-05-15T01:40:51.431039-05:
      DOI: 10.1002/adem.201700246
       
  • Large Area One-Step Fabrication of Three-Level Multiple-Scaled Micro and
           Nanostructured Nickel Sleeves for Roll-to-Roll Hot Embossing 
    • Authors: Valentin Lang; Andreas Rank, Andrés F. Lasagni
      Abstract: Direct laser interference patterning enabled the fabrication of three level multiple-scaled microstructures on nickel surfaces using infrared picosecond laser pulses. While the largest spatial period (1.5 to 5.7 µm) could be controlled by adjusting the angle between the interfering laser beams and the laser wavelength, low and high spatial frequency laser induced periodic surface structures with pitches of approximately 800 nm and 160 nm, respectively, were also observed. Using a set of optimized processing parameters, large area Ni-sleeves were treated. These sleeves were later employed in preliminarily investigations of roll-to-roll high throughput hot-embossing of polymer foils.Direct Laser Interference Patterning is used to produce multiple-scaled microstructures on nickel surfaces using picosecond laser radiation. Using this method, structure depths up to 2 µm are achieved in a one-step process and even on the surface of large-area Ni-sleeves. Preliminary results on the use of the treated Ni-sleeves for roll-to-roll hot embossing processing are show for the first time.
      PubDate: 2017-05-12T08:47:42.578371-05:
      DOI: 10.1002/adem.201700126
       
  • A Novel Direct Liquid Injection Low Pressure Chemical Vapor Deposition
           System (DLI-LPCVD) for the Deposition of Thin Films 
    • Authors: Mattias Vervaele; Bert De Roo, Jolien Debehets, Marilyne Sousa, Luman Zhang, Bart Van Bilzen, Stephanie Seré, Herve Guillon, Markku Rajala, Jin Won Seo, Jean-Pierre Locquet
      Abstract: In this work, the use of a newly developed direct liquid injection low pressure chemical vapor deposition (DLI-LPCVD) system is described, which allows for the deposition of thin films in a controlled and reproducible manner. The capabilities of this system are described via silica thin films deposited using the precursor tetraethyl orthosilicate (TEOS). The deposition of thin films is controlled by parameters, such as deposition temperature, partial pressure of the gases, and flow rate of the precursor solution. The thickness of the deposited layer is varied simply by changing deposition temperature and time. X-ray reflectivity and spectroscopic ellipsometry of the deposited samples show that the thickness of the layers is well controlled by deposition temperature and time. Auger electron spectroscopy, in addition, motivates our choice to use cyclohexane as a solvent. A growth rate of 12.2 Å min−1 is obtained. Atomic force microscopy, Rutherford backscattering spectroscopy, Fourier transform infrared spectroscopy, and drop shape analysis are used to measure roughness, composition, and hydrophobicity. Thin films of silicon dioxide are successfully grown by the newly developed DLI-LPCVD system. This system can be used for a wide range of films by varying the precursors.This work describes the use of a newly developed direct liquid injection - low pressure chemical vapor deposition (DLI-LPCVD) system, which allows for the deposition of thin films in a controlled and reproducible manner. We describe the capabilities of this system via silica thin films deposited using the precursor tetraethyl orthosilicate (TEOS).
      PubDate: 2017-05-12T08:47:33.774192-05:
      DOI: 10.1002/adem.201700193
       
  • Study on the Compression Properties and Deformation Failure Mechanism of
           Open-Cell Copper Foam 
    • Authors: Jian Chen; Xiongfei Li, Wei Li, Jianjun He, Cong Li, Shuowei Dai, Jianlin Chen, Yanjie Ren
      Abstract: Uniaxial compression experiments on open-cell copper foams are conducted at strain rates of 10−2 s−1, 10−3 s−1, and 10−4 s−1 to obtain the true stress-strain curves. The effects of the strain rate, cell size, and porosity on the mechanical properties is studied. The deformation mechanism of the open-cell copper foams is investigated by experimental research and finite element analysis. The results showed that the compression strength, Young's modulus and yield strength increase with increasing strain rate and decreasing porosity and cell size. A lower strain rate results in higher strain sensitivity. Strain-hardening behavior occurred in the process of high-strain-rate loading. The experimental and simulation results indicate that the failure mechanism of the open-cell copper foam is the layer-by-layer collapse failure mechanism and that stress concentrations form easily at the weak pore struts. The simulation results are consistent with the experimental data at the first and second stages. However, the value of true stress predicted by the simulation at the third stage is slightly higher than that of the experiments.The failure mechanism of open-cell copper foam under compression loading is investigated. The bend of hollow struts in the compression process results in the propagation of cracks. Cracks in the hollow strut extend along the circumferential direction. Besides, the cracks appear at the convex of struts.
      PubDate: 2017-05-12T01:50:29.88125-05:0
      DOI: 10.1002/adem.201600861
       
  • 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
       
  • On the Breakdown of SiC during the Selective Laser Melting of Aluminum
           Matrix Composites 
    • Authors: Lachlan Connor Astfalck; Gemma Kaye Kelly, Xiaopeng Li, Timothy Barry Sercombe
      Abstract: Selective laser melting (SLM) is used to produce a SiC reinforced aluminum metal matrix composite (AMMC, Al–12Si plus 10 vol% SiC) with laser energy densities (Ep¯) between 20 and 80 J mm−3. Microstructural analysis shows that at lower energies, SiC is present in the Al–12Si matrix; however, at higher energies there is a distinct lack of SiC particles and the extensive formation of Al4C3 needles and primary Si particles. XRD analysis confirms a decrease in the volume of SiC and an increase in the amount of Al4C3 and primary Si with increasing Ep¯. This indicates that a reaction occurs between the Al and SiC during SLM. The underlying mechanism is attributed to the selective absorption of laser energy into the SiC particles, causing regions of extremely high temperatures. The formation of the reaction products cause errors in the theoretical density calculations. Therefore, X-ray micro tomography (XMT) is used to independently measure the relative density of the samples with a peak relative density ≈97.4%, which is much higher than that (relative density ≈93%) measured using the Archimedes method.Selective laser melting (SLM) is used to produce a SiC reinforced aluminum metal matrix composite. The content of SiC in the as-fabricated composites is influenced by the laser energy density. A reaction occurred between the Al and SiC during SLM due to extremely high local temperatures, which is attributed to the selective absorption of laser energy into the SiC particles.
      PubDate: 2017-05-11T03:16:12.679412-05:
      DOI: 10.1002/adem.201600835
       
  • Comment on “An Experimental Study on Evolution of Grain-Scale
           Stress/Strain and Geometrical Necessary Dislocations in Advanced TA15
           Titanium Alloy during Uniaxial Tension Deformation” 
    • Authors: Thomas Benjamin Britton
      Abstract: This is a brief comment to highlight and discuss issues with regards to the high resolution, cross correlation-based, electron backscatter diffraction (HR-EBSD) results presented within the work of He et al. (2016) Advanced Engineering Materials. In this comment, two specific concerns are raised: one, the stress measurements, reported to be as high as 20 GPa, are unreasonable and due to a known artefact in the form of HR-EBSD analysis, which has been corrected in state-of-the-art measurements by patterning remapping; and two, the GND field measurements are incorrectly calculated and show the variations in lattice rotation and are no derived from the gradient of the lattice rotation field, as required when following Nye's analysis. An example of reasonable data is presented to highlight how these artefacts can be avoided in practice using more appropriate analysis techniques.HR-EBSD measurements of one grain from deformed copper (the size of this grain is
      PubDate: 2017-05-11T03:10:29.988438-05:
      DOI: 10.1002/adem.201700051
       
  • Contribution of Ligand Oxidation Products to High Durability of Copper
           Films Prepared from Low-Sintering-Temperature Copper Ink on Polymer
           Substrates 
    • Authors: Yusuke Akiyama; Tomonori Sugiyama, Hideya Kawasaki
      Abstract: In electronic printing, ensuring high durability of sintered copper films on flexible substrates to obtain environmental stability and mechanical flexibility has become the most important task from a practical standpoint. In the study reported here, the authors develop solution synthesis of 2-amino-2-ethyl-1,3-propanediol (AEP)-protected copper nanoparticles (AEP–Cu NPs) with sizes of 3–8 nm in ethylene glycol, where the Cu NPs are stabilized via the metallacyclic coordination stability of the AEP ligands. The sintered Cu film exhibits a resistivity of 50 μΩ cm−1 after heating at 150 °C under a nitrogen atmosphere. Most importantly, the resulting Cu films on the polyethylene terephthalate (PET) substrates show excellent durability in terms of bending and adhesion without requiring any additives like nanotubes and nanowires. Furthermore, the authors successfully demonstrated the high environmental stability of the resulting Cu film even after it is exposed to harsh environmental conditions (RH 80%, 60 °C) for 1 month. The environmental durability is further improved by utilizing a composite ink of AEP–Cu NPs with copper microflakes. It is experimentally proven that oxidation products from AEP ligands originating in the sintering process contributed to the high durability of sintered copper films on flexible substrates.This study presents copper films prepared from copper ink with low sintering temperature on polymer substrates. They are highly durable in terms of bending and adhesion, without requiring any additives such as nanotubes and nanowires. Furthermore, the Cu film exhibits high environmental stability even after 1 month of storage under harsh environmental conditions (RH 80%, 60 °C).
      PubDate: 2017-05-10T06:10:45.638877-05:
      DOI: 10.1002/adem.201700259
       
  • Changing the Band Gaps by Controlling the Distribution of Initial Particle
           Size to Improve the Power Factor of N-Type Bi2Te3 Based Polycrystalline
           Bulks 
    • Authors: Chengcheng Zhang; Xi An Fan, Jie Hu, Chengpeng Jiang, Qiusheng Xiang, Guangqiang Li, Yawei Li, Zhu He
      Abstract: In this work, n-type Bi2Te2.7Se0.3 bulks are prepared by resistance pressure sintering technique from different particle sized powders, and the microstructure and electrical transport properties are investigated as function of the initial particle size distribution. With the initial particle size decreasing, more antisite defects, grain-boundaries and interface defects are introduced, and lead to a larger carrier concentration due to donor-like effect and a lower mobility due to the increasing grain boundary and carrier scattering, which results in a lower Seebeck coefficient and electrical resistivity. As a result, a maximum power factor of about 2.89 mW mK−2 at room temperature is achieved for the bulk sintered from the mix powders with different particle size distribution due to the optimization of the carrier concentration. The band gaps and the intrinsic excitation temperature are effectively adjusted by controlling the particle size in a narrow distribution. The sample sintered from the powders below 400 mesh has the highest average power factor above 2.44 mW mK−2 in the whole testing temperature range due to the improving band gaps and intrinsic excitation temperature.By controlling the particle size in a narrow range strictly, the carrier concentration and mobility are optimized. As a result, the average PF of about 2.44 mW mK−2 is achieved in the whole testing temperature range due to the improving band gaps and intrinsic excitation temperature.
      PubDate: 2017-05-10T06:10:32.884613-05:
      DOI: 10.1002/adem.201600696
       
  • Impact Testing of Polymer-filled Auxetics Using Split Hopkinson Pressure
           Bar 
    • Authors: Tomáš Fíla; Petr Zlámal, Ondřej Jiroušek, Jan Falta, Petr Koudelka, Daniel Kytýř, Tomáš Doktor, Jaroslav Valach
      Abstract: In this paper, impact testing of auxetic structures filled with strain rate sensitive material is presented. Two dimensional missing rib, 2D re-entrant honeycomb, and 3D re-entrant honeycomb lattices are investigated. Structures are divided into three groups according to type of filling: no filling, low expansion polyurethane foam, and ordnance gelatine. Samples from each group are tested under quasi-static loading and dynamic compression using Split Hopkinson Pressure Bar. Digital image correlation is used for assessment of in-plane displacement and strain fields. Ratios between quasi-static and dynamic results for plateau stresses and specific energy absorption in the plateau are calculated. It is found out that not only the manufactured structures, but also the wrought material exhibit strain rate dependent properties. Evaluation of influence of filling on mechanical properties shows that polyurethane increases specific absorbed energy by a factor of 1.05–1.4, whereas the effect of gelatine leads to increase of only 5–10%. Analysis of the Poisson's function reveals influence of filling on achievable (negative) values of Poisson's ratio, when compared to unfilled specimens. The results for the Poisson's function yielded apparently different values as the assessed minima of quasi-static Poisson's ratio in small deformations are constrained by a factor of 15.In this paper, additively manufactured auxetic lattices are subjected to impact loading using Split Hopkinson Pressure Bar (SHPB). Selected samples are filled with strain rate sensitive material. Digital image correlation is used for analysis of the deformation behavior of the samples. Influence of filling on the samples’ stress–strain curves, negative Poisson's ratio, and strain-rate sensitivity is investigated.
      PubDate: 2017-05-08T07:05:29.137599-05:
      DOI: 10.1002/adem.201700076
       
  • Mechanical Behavior of Particulate Aluminium-Epoxy Hybrid Foams Based on
           Cold-Setting Polymers 
    • Authors: Jörg Weise; André Felipe Queiroz Barbosa, Olga Yezerska, Dirk Lehmhus, Joachim Baumeister
      Abstract: New types of hybrid foams with cold-setting polymer foam matrix have been developed. These are based on AlSi10 foam granules and a cold-setting epoxy polymer foam phase. The mechanical characteristics of the hybrid foams like stiffness, compressive, and tensile strength were determined using quasi-static compression and tensile tests. Their overall mechanical behavior is compared to APM-(Advanced Pore Morphology)-based hybrid foams comprising similar aluminium foam granules in combination with single component hot setting epoxy foams. While the latter generally outperform the cold-setting variants at their present state of development, the ease of manufacturing in conjunction with promising levels of strength, and stiffness will support future application of the new material.Hybrid foam consisting of aluminium foam and cold-setting epoxy polymer foam can be used for the filling and reinforcement of hollow structures. While FoaminalTM aluminium foam outperforms the hybrid foam, the ease of manufacturing and promising level of strength and stiffness support future application of the new material.
      PubDate: 2017-05-08T01:29:38.371487-05:
      DOI: 10.1002/adem.201700090
       
  • Prediction of New Structure, Phase Transition, Mechanical, and
           Thermodynamic Properties of Nb3Si 
    • Authors: Yong Pan
      Abstract: Although Nb-based silicides are promising high temperature materials, the high temperature application of Nb-based silicides is markedly influenced by Nb3Si phase. However, the structure and relevant properties of Nb3Si are not completely clear. To solve these problems, in this paper, we systematically investigate the structure, elastic properties, brittle or ductile behavior, and thermodynamic properties of Nb3Si based on the first-principle calculations. Additionally, phase transition of Nb3Si under high pressure is studied in detail. The calculated results show that two new Nb3Si phases: Br3Sm-type (space group: Cmcm, No.63) and Sc3In-type (space group: P63/mmc, No.194) are predicted. Although Nb3Si with Ta3Si-type is the most stable structure, pressure leads to phase transition from Ta3Si-type structure to V3Si-type structure at ≈60 GPa. We further demonstrate that Nb3Si is a ductile material. Importantly, we find that the heat capacity of Nb3Si with tetragonal structure is about 190 J (mol K)−1, which is two times larger than that of other structures.Two new Nb3Si structures: Br3Sm-type (space group: Cmcm, No.63) and Sc3In-type (space group: P63/mmc, No.194) are predicted. We further demonstrated that tetragonal structure is more stable than that of other structure. In particular, pressure results in phase transition from Ta3Si-type structure to V3Si-type structure at ∼ 60 GPa.
      PubDate: 2017-05-08T01:29:29.990281-05:
      DOI: 10.1002/adem.201700099
       
  • Nitride, Zirconia, Alumina, and Carbide Coatings on Ti6Al4V Femoral Heads:
           Effect of Deposition Techniques on Mechanical and Tribological
           Properties 
    • Authors: Duygu Ege; İlayda Duru, Ali Reza Kamali, Aldo R. Boccaccini
      Abstract: Ti6Al4V has been extensively studied in orthopedic applications because of its biocompatibility, desirable mechanical strength, and fatigue resistance. A wide range of bioinert ceramics have been investigated to further develop the tribological and mechanical properties of Ti6Al4V for the production of potential femoral heads. However, an analysis of the literature indicates that the performance of the coatings produced has been inconsistent. In this review, for the first-time deposition techniques of the most widely studied bioinert ceramics namely nitrides, carbides, zirconia, and alumina on Ti6Al4V substrates and their relevant mechanical and tribological performance have been analyzed. Finally, graphene has also been suggested for use together with bioinert ceramics due to its excellent mechanical and physical properties for coating Ti6Al4V femoral heads.The materials provided enable the comparison of the relative performance of the various bioinertceramic-based coatings at a glance.
      PubDate: 2017-05-08T01:18:25.841651-05:
      DOI: 10.1002/adem.201700177
       
  • Is it Possible to Use Rolling Methods to Improve Textures on Fe–Mn–Si
           Shape Memory Alloys' 
    • Authors: Ana V. Druker; César Sobrero, Valeria Fuster, Jorge Malarría, Raúl Bolmaro
      Abstract: No uniform rolling deformation produces shear strains that give rise to textural and microstructural heterogeneities in processed metals and alloys. In this work, the authors investigate Fe–30Mn–4Si shape memory alloy sheets rolled in different conditions at 600 °C, in order to determine the process giving rise to the best structure and the strongest {100} shear texture. This crystallographic orientation is the most favorable for the γ ϵ martensitic transformation, which provides the shape memory effect in these alloys. In the current conditions, the authors find that unidirectional rolling produces a shear texture in sheet's surface layers. The authors compare the texture and microstructure from this process to those obtained from reverse rolling and single-roller drive rolling.The authors investigate Fe-30Mn-4Si shape memory alloy sheets rolled in different conditions, looking for the best structure and the strongest {100} shear texture. By comparison with reverse (RR) and single-roller drive rolling (SR), the authors concluded that only unidirectional rolling (UR) produces the necessary shear texture in sheet's surface layers.
      PubDate: 2017-05-02T10:37:00.340628-05:
      DOI: 10.1002/adem.201700062
       
  • 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
       
  • Investigation on Behavior of Elastoplastic Deformation for
           Ti–48Al–2Cr–2Nb Alloy by Micro-Indentation and FEM-Reverse
           Algorithm 
    • Authors: Zhanwei Yuan; Chunwei Wang, Fuguo Li, Yongbiao Hu, Yajie Guo, Qi Chen, Yingying Wang, Mengle Guo
      Abstract: The Young's modulus, microhardness, and plastic properties of Ti–48Al–2Cr–2Nb alloy were determined using the micro-indentation technique. Oliver–Pharr method was used to calculate Young's modulus and microhardness. The indentation load was inversely correlated to Young's modulus and microhardness. The decreased Young's modulus was associated with indentation damage, while decreasing hardness was due to indentation size effect. The plastic properties were determined using proposed FEM-reverse algorithm, which combine finite element method and Matlab GA optimization tools. We used uniaxial compression test to verify the plastic properties calculated from the indentation tests, and it was found that the stress–strain plots predicted by FEM-reverse algorithm was quite similar to the test results.In this study, the mechanical properties of Ti–48Al–2Cr–2Nb are investigated by micro-indentation experiments. A FEM-reverse algorithm, which combined FEM simulation with Matlab GA optimization tools is proposed. And the FEM-reverse algorithm has been verified with good prediction.
      PubDate: 2017-04-27T18:57:57.723039-05:
      DOI: 10.1002/adem.201700097
       
  • Effect of Room and High Temperature Compaction on Optical and Mechanical
           Properties of HIPed Transparent Spinel Ceramics  
    • Authors: Papiya Biswas; Pandu Ramavath, Chandrashekhar Sadasiv Kumbhar, Dinesh S. Patil, Tapas Kumar Chongdar, Nitin Madhusudan Gokhale, Roy Johnson, Mantravadi Krishna Mohan
      Abstract: Spinel specimens are processed through Hot Pressing at 1620 °C and 20 MPa (designated as HPS) and uniaxial pressing at room temperature with 80 MPa followed by pressure-less sintering at 1650 °C (designated as CS). HPS exhibit translucency with marginally higher density (99.8% of theoretical density (TD)) in comparison to CS with 99.5% of TD and negligible transmission value. HPS samples have shown a transmission of 40 and 76% in visible and midwave infrared (MWIR) region, respectively. Both HPS and CS samples are further subjected to Hot Isostatic Pressing (designated as HPS + HIP and CS + HIP, respectively), at identical conditions of 1800 °C and 195 MPa to achieve close to TD and transparency. HPS + HIP and CS + HIP samples enhance their transmission to 78 and 71% in visible region and 86 and 79% in MWIR region, respectively. Although most important parameter for transparent ceramics, i.e., transmission values are relatively high for HPS + HIP samples and exhibit substantially lower hardness and flexural strength values in comparison to CS + HIP samples at room and elevated temperature. Fractographic studies of samples fail under flexure at room and elevated temperature have exhibited cleavage fracture with longer facet length for HPS + HIP correlating well with microstructure. Difference in mechanical properties can be attributed to differences in grain size produced by two methodologies.MgAl2O4 spinel powder compacted under room and elevated temperature, are subjected to hot isostatic pressing followed by property evaluations. Though the samples, processed through both the routes have identical densities, mechanical properties are superior for cold compacted samples in comparison to hot compacted samples which have exhibits better optical transmission. Results are also correlated with processing conditions.
      PubDate: 2017-04-26T06:16:00.729072-05:
      DOI: 10.1002/adem.201700111
       
  • Response to Comment on “An Experimental Study on Evolution of
           Grain-Scale Stress/Strain and Geometrical Necessary Dislocations in
           Advanced TA15 Titanium Alloy during Uniaxial Tension Deformation”
    • Authors: Dong He; Stefan Zaefferer, Qiang Li
      Abstract: Britton criticizes the accuracy of the stress value and surmises that the rotation field is used during geometrical necessary dislocations (GND) calculation process. It is their opinion, however, that the topic of the absolute values of the stresses is not discussed at all in their paper. Their paper is focused rather on relative values (stress partitioning at different strains), but not on absolute values. It should, however, be mentioned that, due to the high orientation changes within grains, the error for stress measurements may be considerable, as pointed out by Britton. The stress measurements should, therefore, be regarded with care. The authors have checked the GND calculation code carefully and the authors confirm that the correct rotation gradient field data is adopted in the GND calculation process.Calculation processes of stress/strain obtained from electron backscatter diffraction and geometrical necessary dislocations (GND) density in TA15 titanium subjected to uniaxial tensile deformation are investigated. The similarity between kernel average misorientation (KAM) images and GND distribution images are compared and explained.
      PubDate: 2017-04-26T06:15:56.685694-05:
      DOI: 10.1002/adem.201700293
       
  • Ultrasonic Spot Welding of Nickel Foam Sheet and Aluminum Solid
           Sheet  
    • Authors: Yan Xie; Mengnan Feng, Yangchuan Cai, Zhen Luo
      Abstract: Nickel foam sheet composed of three-dimensional (3D) triangular struts and aluminum solid sheet are welded via ultrasonic spot welding. The foam underwent acceptable thickness reduction and deformation, whereas most of the porous structures remain intact. Energy dispersive spectroscopy (EDS) analysis shows that little interdiffusion is noticed across the welding interface, leading to the formation of only a small amount of solid solution, and intermetallic compounds. Infrared temperature measurements show that the joint-temperature variation of the welding interface is substantially lower than the solid-solution temperature of Al/Ni, and the welding process is in solid state. The resistance of the joints is measured, and the contact resistance is calculated. The specimen with excellent interface connection exhibits low contact resistance. As the welding energy increases, the failure mode transitions from interfacial fracture to pull-out fracture, with the tensile load and fracture energy reaching 58 and 69%, respectively, of those corresponding to the nickel foam base metal. Fracture occurs exclusively on the nickel foam sheet, and the fracture mode is ductile fracture.Nickel foam sheet and aluminum solid sheet for battery tab and catalyst support are successfully joined via ultrasonic spot welding. The foam undergoes acceptable thickness reduction and deformation, whereas most of the porous structures remain intact. The mechanical and electrical properties of joints welded at different energies are studied. The welding process is in solid state.
      PubDate: 2017-04-26T06:10:34.310364-05:
      DOI: 10.1002/adem.201700094
       
  • 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
       
  • Phase Stability of a Mechanically Alloyed CoCrCuFeNi High Entropy
           Alloy 
    • Authors: Shanmugasundaram Thangaraju; Thangaraju Emmanuel . Bouzy, Alain Hazotte
      Abstract: A CoCrCuFeNi high entropy alloy (HEA) is prepared from the high purity elemental Co,Cr, Cu,Fe, and Ni powders by mechanical alloying (MA) at different milling speed (200 or 350 rpm). Mechanically alloyed powder samples are subsequently annealed at different temperatures (300, 500, 700, and 800 °C). Microstructures, chemical composition, and phase stability of the powders are studied using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and energy dispersive X-ray spectrometry (EDS). The results show that, a single phase stable FCC solid solution is formed within 5 and 50 h of milling at 350 and 200 rpm, respectively. The single FCC phase is identified to be thermally stable upto 800 °C and then it is decomposed into two FCC phases. The second FCC phase is found to be rich in Cu. The precipitation of the Cu rich phase is likely due to the positive enthalpy of mixing of Cu with other alloying elements.Phase stability of a mechanically alloyed CoCrCuFeNi high entropy alloy is studied. A single phase FCC solid solution that formed within 5 h of alloying is retained upto 800 °C. Therefore, CoCrCuFeNi HEAs shall be heat treated or sintered below 800 °C to retain the single phase structure.
      PubDate: 2017-04-24T06:11:27.466596-05:
      DOI: 10.1002/adem.201700095
       
  • Stabilization of 2D Water Films in Porous Triple-Layer Membranes with a
           Hydrophilic Core: Cooling Textiles and Passive Evaporative Room Climate
           Control 
    • Authors: Mario Stucki; Wendelin J. Stark
      Abstract: Cooling and climate control are among the largest energy consuming processes in the world. By introducing passive systems, the energy consumption can be shifted to more renewable sources like sunlight. Combining hydrophobic and hydrophilic polymeric matrices in fully porous flat sheet membranes affords a triple-layer construct able of laterally transport water without energy input, while cooling and wetting the surrounding air by evaporation. In three subsequent coating steps, the material is assembled, the pore-forming template is released, and the materials are tested on their behavior in a passive cooling application. The straightforward and simple way of combining polymers with opposing chemical properties in a fully porous manner offers a wide range of new applications.Combining hydrophobic and hydrophilic polymeric matrices in fully porous flat sheet membranes affords a triple-layer construct able of laterally transport water without energy input, while cooling, and wetting the surrounding air by evaporation. In three subsequent coating steps, the material is assembled, the pore-forming template is released, and the materials is tested on their behavior in a passive cooling application.
      PubDate: 2017-04-24T06:11:23.900902-05:
      DOI: 10.1002/adem.201700134
       
  • 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 paper shows the results of wetting experiments of an AlSi7Mg alloy on different oxide ceramics (Al2O3, MgAl2O4, 3Al2O3 · 2SiO2, and TiO2). 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
       
  • Extreme-Value Statistics Reveal Rare Failure-Critical Defects in Additive
           Manufacturing 
    • Authors: Brad L. Boyce; Bradley C. Salzbrenner, Jeffrey M. Rodelas, Laura P. Swiler, Jonathan D. Madison, Bradley H. Jared, Yu-Lin Shen
      Abstract: Additive manufacturing enables the rapid, cost effective production of customized structural components. To fully capitalize on the agility of additive manufacturing, it is necessary to develop complementary high-throughput materials evaluation techniques. In this study, over 1000 nominally identical tensile tests are used to explore the effect of process variability on the mechanical property distributions of a precipitation hardened stainless steel produced by a laser powder bed fusion process, also known as direct metal laser sintering or selective laser melting. With this large dataset, rare defects are revealed that affect only ≈2% of the population, stemming from a single build lot of material. The rare defects cause a substantial loss in ductility and are associated with an interconnected network of porosity. The adoption of streamlined test methods will be paramount to diagnosing and mitigating such dangerous anomalies in future structural components.Arrays of tensile bars printed by laser powder bed fusion (additive manufacturing) are tested with a high-throughput mechanical test method. The resulting property distributions reveal within- and between-build variability as well as anomalous behavior associated with rare, failure-critical defects.
      PubDate: 2017-04-21T06:45:54.645985-05:
      DOI: 10.1002/adem.201700102
       
  • Net Shape 3D Printed NdFeB Permanent Magnet 
    • Authors: Jaćim Jaćimović; Federico Binda, Lorenz G. Herrmann, Felix Greuter, Jessica Genta, Micha Calvo, Tomaž Tomše, Reinhard A. Simon
      Abstract: Three dimensional printing enables realization of complex shape rare earth permanent magnet that enable unlocking the full potential of electrical devices for energy consumption and renewable energy production.
      PubDate: 2017-04-21T03:36:30.3748-05:00
      DOI: 10.1002/adem.201700098
       
  • Direct Catalyst-Free Chemical Vapor Deposition of ZnO Nanowire Array UV
           Photodetectors with Enhanced Photoresponse Speed 
    • Authors: Zhaoyao Zhan; Liping Xu, Jianing An, Hejun Du, Zhankun Weng, Wenqiang Lu
      Abstract: ZnO-based photodetectors (PDs) have long response times at magnitude of tens to hundreds of seconds, hampering their practical UV detection. The slow oxygen chemisorption/desorption process is the main cause of the slow response of UV PDs based on single ZnO nanowires (NWs). Here, the authors find the response speed of ZnO NW-based UV PDs could be improved by directly fabricating UV PDs on entangled ZnO NW array grown on SiO2 through a catalyst-free chemical vapor deposition (CVD) process. Specifically, the interconnections in ZnO NW array creates NW–NW junction barriers, which dominate the inter-wire charge transport. The switching of UV illumination induces fast tuning of NW–NW junction barrier height, which contributes to the enhanced response speed of the ZnO NW array UV PDs.Carrier generation and transport in ZnO NW array PD. The extra Nanowire–Nanowire junction barriers dominate charge transport in the ZnO NW array; the electrons must overcome the junction barriers to transport from one NW to another. Under UV illumination, the height of junction barriers is much reduced, and thus conductivity of ZnO NW array is greatly enhanced.
      PubDate: 2017-04-20T05:02:10.054229-05:
      DOI: 10.1002/adem.201700101
       
  • On the Influence of Ta and Ti on Heat-Treatability and
           γ/γ’-Partitioning of High W Containing Re-Free Nickel-Based
           Superalloys 
    • Authors: Nils C. Ritter; Ekaterina Schesler, Alexander Müller, Ralf Rettig, Carolin Körner, Robert F. Singer
      Abstract: Refractory elements like W are potent solid solution strengtheners, but they are also heavy and costly. They should be used as sparingly as possible. In the present paper, a series of single crystal alloys are prepared with varying amounts of Ta and Ti, but constant overall refractory concentration and γ’-volume fraction. Partitioning behavior of W and other elements after solutionizing and ageing treatment is investigated. Both, Ta and Ti are able to increase the W content in the γ-matrix. This provides an effective strategy to maximize solid solution strengthening potential for a given overall W content of the alloy. The experimentally determined phase characteristics and homogenization behavior are compared with numerical simulation. Good agreement is observed.The investigation deals with the direct comparison of Ta and Ti as well as Ta + Ti combination regarding heat-treatability, transformation-temperatures, and their influence on the partitioning behavior of solid solution strengthening element W. Ta is more effective in pushing W from γ'-phase into matrix compared to Ti. In all three alloys every element except W can be homogenized completely.
      PubDate: 2017-04-19T06:12:56.661104-05:
      DOI: 10.1002/adem.201700150
       
  • Numerical and Experimental Investigations on the Growth of the
           Intermetallic Mg2Si Phase in Mg Infiltrated Si-Foams 
    • Authors: Fei Wang; Alexander M. Matz, Oleg Tschukin, Johann Heimann, Bettina S. Mocker, Britta Nestler, Norbert Jost
      Abstract: The present work explores the growing behavior of the intermetallic layer in the Mg-Si system. Following achievements have been obtained in our investigation: (i) A complete wetting concept is proposed for the lateral spreading of the intermetallic layer. (ii) In contrast to the stoichiometric property for the intermetallic phase in the phase diagram, the authors show that concentration gradients are able to be established in the kinetic process. (iii) Contrary to the reported growth behavior, d ∝ t0.25–0.5 in other intermetallics, the authors find a transition from d ∝ t to d ∝ t with an increase of the temperature, where d is the thickness of the intermetallic layer and t is the time.The growth of the intermetallic Mg2Si layer in the Mg infiltrated Si-foam is investigated. The formation of the intermetallic layer in the earlier stage is attributed to a complete wetting effect. With time, the thickness of the intermetallic phase d increases. Depending on whether the process is reaction, bulk diffusion, or grain boundary diffusion dominated, the authors have different growth behaviors: d ∝ t, d t, or d ∝ t1/3.
      PubDate: 2017-04-19T05:00:36.907525-05:
      DOI: 10.1002/adem.201700063
       
  • Optimization of a Cellular Glass Ceramic Produced from Water
           Potabilization Sludge for Structural and Chemical Applications 
    • Authors: Rosa María Ramírez Zamora; Fabricio Espejel Ayala, Iván Emilio MartínezHerrera, Víctor Manuel Sánchez Orendain, Gabriela Díaz, Myriam Solís López López, Rafael Schouwenaars
      Abstract: Waste sludge generated in the potabilization of surface water is used to produce cellular materials by mixing with clay and firing at 1 250 °C. An iron-rich glassy matrix with crystals of mullite and albite is formed. Porosity is generated by the slow release of H2O, which originates from the dehydroxilation of lepidocrocite at high temperature. The sludge/clay ratio and the sludge granulometry determine the properties of the product: from highly porous cellular foams to denser materials with high strength. Laboratory tests for both kinds of products show that the latter can be used as aggregates for low-density structural concrete. The former serve as a support material for the catalytic reduction of NOx in exhaust gases. Deposition conditions for Fe- and Pt-nanoparticles are optimized by experimental design, resulting in NOx-conversion rates close to 100%.The technical feasibility of using cellular ceramics produced from waste sludge is demonstrated for high-strength as well as high-porosity variants of this material, which consists of a glassy matrix with crystalline inclusions. At short firing times, the fine-grained fraction of the sludge produces a product suitable as an aggregate for lightweight structural concrete. The coarse grained fraction, at longer firing times, allows producing a permeable ceramic foam for catalyst support in selective reduction of NOx. The Pt and Fe-based catalysts tested are found to provide very high conversion rates even at high space velocities in an experimental reactor.
      PubDate: 2017-04-19T04:57:23.447507-05:
      DOI: 10.1002/adem.201700074
       
  • Microstructure and Corrosion Behavior of the Friction Stir Welded Joints
           Made from Ultrafine Grained Aluminum 
    • Authors: Marta Lipińska; Ewa Ura-Bińczyk, Lech Olejnik, Andrzej Rosochowski, Małgorzata Lewandowska
      Abstract: Joints made from ultrafine grained aluminium alloy 1050 are investigated in order to examine the corrosion behavior and microstructural changes between base materials and stir zones. Samples in the initial state, after four and eight passes of Incremental ECAP (I-ECAP) process were joined with similar plates using Friction Stir Welding. Initially refined microstructure after I-ECAP transformed to homogenous few micron sized grains structure in stir zones. AlFeSi particles present in the microstructure became fragmented during plastic deformation and welding process. The observed minor differences in corrosion resistance include slightly higher values of corrosion potentials but more complex pits’ morphology for I-ECAP processed samples comparing to the stir zones.The changes in the microstructure and corrosion resistance between base materials (BM) and stir zones (SZ) are investigated. The number refers to the number of I-ECAP passes of base material. After the corrosion tests, the surface of the samples was examined using SEM. With increasing number of I-ECAP passes, the pits pose more developed structure with linked cavities. For SZ samples, which exhibit higher grain size, the number of pits is reduced. Pits are also less developed but deeper. The number of pits and surface covered by them is connected with size of AlFeSi particles.
      PubDate: 2017-04-18T06:35:59.395926-05:
      DOI: 10.1002/adem.201600807
       
  • Arbitrarily Shaped 2.5D Circuits using Stretchable Interconnects Embedded
           in Thermoplastic Polymers 
    • Authors: Bart Plovie; Yang Yang, Joren Guillaume, Sheila Dunphy, Kristof Dhaenens, Steven Van Put, Björn Vandecasteele, Thomas Vervust, Frederick Bossuyt, Jan Vanfleteren
      Abstract: A method to fabricate thermoplastically deformable electronic circuits is presented, with the intent of achieving low-cost 2.5D free-form rigid smart objects. This by utilizing existing flexible circuit technology based stretchable circuits, in combination with thermoplastic materials. After fabricating the circuit in a flat state, a thermoforming step shapes the device by heating it beyond its glass transition temperature, and pushing it against a mold. Preliminary tests show the feasibility to fabricate simple circuits using off-the-shelf circuit components; showing a minimal decrease in conductivity of the polyimide supported copper-based interconnects.An electronic device is fabricated in a flat state and deformed through a thermal process, after which it retains its shape. After analysis of existing technologies, their bottlenecks a novel method using existing flexible and stretchable circuit technology is proposed to achieve such devices. The feasibility is demonstrated using a series of demonstration devices.
      PubDate: 2017-04-18T02:45:32.975715-05:
      DOI: 10.1002/adem.201700032
       
  • Microstructure and Mechanical Properties of Fine Structured B4C/2024 Al
           Composites with High B4C Content 
    • Authors: Ruixiao Zheng; Fengmei Ma, Yitan Zhang, Chaoli Ma
      Abstract: In this study, bulk fine structured B4C/2024 Al composites with various B4C content are prepared by mechanical milling and subsequent hot consolidation. Scanning electron microscopy (SEM) observation revealed that the higher the B4C content, the finer the B4C particle size in the bulk composites. Transmission electron microscopy (TEM) observation indicates that the grain size of the Al matrix around the B4C particles is much finer compared to other, area due to the large difference in coefficients of thermal expansion (CTE) between the Al matrix and the B4C particles. Room temperature compression test reveals that with increasing B4C content, the compression strength of the bulk samples first increases and then decreases. The significant change of the mechanical properties is discussed based on the microstructure observed.Bulk fine grained B4C/2024 Al composites with various B4C content are prepared by mechanical milling and subsequent consolidation. The microstructure of the composites can be divided into three zones depending on the microstructural features, which significantly affect the global mechanical properties of the composites.
      PubDate: 2017-04-18T02:45:29.39602-05:0
      DOI: 10.1002/adem.201700047
       
  • 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
       
  • Graphene Platelet (GPL)/Nickel (Ni) Laminate Coatings for Improved Surface
           Properties 
    • Authors: Meng Li; Jian Liu, Xiaoping Zhang, Cunlong Zhou, Sai Priya Munagala, Yaqin Tian, Jie Ren, Kyle Jiang
      Abstract: In this paper, an investigation is reported on graphene platelet (GPL)/nickel (Ni) laminate coatings by electrochemical deposition. Nickel sulphamate baths with and without GPLs are used to produce GPL/Ni coatings with varied layers and pure Ni coatings for comparison. Microstructures, surface roughness, and mechanical performance of the coatings were examined. It is found that GPLs are homogeneously deposited in the Ni matrix. With the addition of GPLs, the surface roughness of the GPL/Ni composites increases while the average grain size of the Ni matrix decreases significantly. A higher hardness of coatings can be obtained by depositing more layers and introducing a higher content of GPLs. The microstructure of GPL/Ni composite coatings exhibits a preferred orientation at (111).In this paper, an investigation is reported on graphene platelet (GPL)/nickel (Ni) multilayer coatings by electrochemical deposition. The schematic of structure of coatings is shown in ToC figure. The research shows the potential of GPLs, as nano fillers for fabrication of composite coatings with excellent mechanical performance, and the preparation of multilayer composites can provide a new way to prepare new composite materials.
      PubDate: 2017-04-18T02:40:30.19909-05:0
      DOI: 10.1002/adem.201600795
       
  • Synthesis, Microstructure, and Catalytic Performance of Monolithic
           Low-Density Porous Au 
    • Authors: Qin Li; Lixian Lian, Ying Liu, Chaoqing Liu
      Abstract: A series of monolithic porous Au with different pore sizes are successfully synthesized by a facile template-dealloying corrosion method. Spherical Cu particles are employed as sacrificial templates, and a FeCl3–HNO3 two-step corrosion method is developed to dissolve the Cu components. The microstructure and phase evolution, as well as the effect of the corrosive media, are investigated in this study. As a result, the prepared monolithic porous Au possesses ultra-low density and a special hollow porous core-shell structure. When a small-sized template (≈1 μm) is adopted, the corresponding density is as low as 0.37 g cm−3 (1.8% of the full density of Au). In addition, due to the special structure, the monolithic porous Au exhibits good catalytic performance (Kapp = 0.43 min−1), that is, relatively higher than that of most traditional Au-based powder/slurry materials.A series of monolithic porous Au with different pore sizes are successfully synthesized using spherical cu particles, as a new kind of sacrificial templates. A Fecl3–HNO3 two-step corrosion method is developed to dissolve the Cu components. The prepared porous Au bulks possess ultra-low density as low as 0.3 g cm−3 and hollow porous core-shell structure, exhibiting excellent catalytic performance as monolithic catalysts.
      PubDate: 2017-04-18T02:35:40.548879-05:
      DOI: 10.1002/adem.201700045
       
  • Study of Interfacial Interactions in Physically Transient Soft Layered
           Structures: A Step toward Understanding Interfacial Bonding and Failure in
           Soft Degradable Structures 
    • Authors: Yuanfen Chen; Reihaneh Jamshidi, Wangyujue Hong, Nicole N. Hashemi, Reza Montazami
      Abstract: Soft multilayer structures have broad applications in transient electronics. Strain-mismatch-induced fracture is key in achieving physical transiency. Here, swelling-mismatch-induced fragmentation of physically transient electrodes is studied. The fragment size of the electrode layer as a function of initial defect distribution is investigated. The average fragment size is predicted and verified by a combination of experimental and FEM analysis. It is found that only large defects initiate fragmentation; this concept can be used to control disintegration of physically transient electronics by means of materials and design, and can be extended to study transiency of soft multilayer structures.Swelling-induced fragmentation of soft transient electrode and its dependency on the initial defect distribution are predicted by computational model and experimentally verified. Accumulation of swelling-induced stress facilitates crack initiation. Large defect initiate cracking earlier and merge small defect while propagating.
      PubDate: 2017-04-18T02:35:36.4696-05:00
      DOI: 10.1002/adem.201700139
       
  • Brazing Graphite to Aluminum Nitride for Thermal Dissipation
           Purpose 
    • Authors: Tsung-Te Chou; Wei-Hsing Tuan, Hiroshi Nishikawa, Biing-Jyh Weng
      Abstract: In the present study, graphite paper is joined to aluminum nitride (AlN) using an active Ag–Cu–Ti foil. The Ti in the brazing foil diffuses to AlN side to form titanium nitride, to graphite side to form titanium carbide during bonding. The thermal diffusivity of the AlN–AgCuTi graphite joint is double that of AlN substrate; the resulting thermal conductivity of the joint is, thus, higher. Though the flexural strength of the joint is half that of AlN substrate, it can deflect for 1 mm at a 28 mm span without failure. The large deflection capability can be related to the sliding between graphite sheets within the graphite paperIn the present study, graphite paper is joined to aluminum nitride (AlN) using an active Ag–Cu–Ti foil. The AlN–Ag–Cu–Ti graphite joint exhibits unique thermal and mechanical characteristics.
      PubDate: 2017-04-13T10:11:01.381013-05:
      DOI: 10.1002/adem.201600876
       
  • Twist Extrusion as a Potent Tool for Obtaining Advanced Engineering
           Materials: A Review 
    • Authors: Yan Beygelzimer; Roman Kulagin, Yuri Estrin, Laszlo S. Toth, Hyoung Seop Kim, Marat I. Latypov
      Abstract: Twist extrusion (TE) is one of the most popular techniques of severe plastic deformation, aiming at imparting to a material a tailored microstructure and the associated property improvement. The article provides a survey of the literature on the mechanics of TE and the effect it has on the structure, texture, and the attendant properties of various materials, including metals and alloys, powder materials, and polymers. Special emphasis is placed on vortex flow during TE and its hitherto unexplored potential for producing micro- and macrostructures that promise superior properties of the materials. In particular, the possibility of creating novel hybrid materials with chiral inner architecture is demonstrated. The survey is concluded by a presentation of examples of practical applications of TE.Twist extrusion is a process producing large strains under high pressure that gives rise to vortex fluxes within the billet, as illustrated by the figure. The resulting transformation of its inner structure at various length scales – from nano to macro – can be used to create novel high-performance materials.
      PubDate: 2017-04-10T07:16:49.205257-05:
      DOI: 10.1002/adem.201600873
       
  • Analysis of Geometrical and Process-Related Parameters on the Impregnation
           Quality of Advanced Cellular Composites 
    • Authors: Oliver Weißenborn; Sirko Geller, Maik Gude
      Abstract: Based on the well-established polyurethane (PUR) spray coat method, an integral manufacturing process is developed to simultaneously create textile-reinforced top and bottom layers as well as the cellular core in one single production step for advanced sandwich structures. Since the foaming matrix impregnates the textile layers during expansion and also serves as core material in the final part, these sandwich elements are connected cohesively with each other. Within this paper, impregnation studies are conducted to evaluate the influence of process parameters, such as mold temperature and dwelling time of the foam matrix, as well as part geometry and foam density on the local yarn impregnation. Evaluation of cell morphology is performed by measuring the cell size distribution inside impregnated yarns.Novel processing technologies for smart design concepts of structural lightweight parts are of high relevance for industrial applications. In this context, the PUR spray coat method is used to impregnate carbon fiber textiles with a cellular matrix material by using the expansion reaction of PUR rigid foams. The influence on the local impregnation quality and composite morphology is investigated comprehensively.
      PubDate: 2017-04-10T06:21:31.810797-05:
      DOI: 10.1002/adem.201700087
       
  • Continuous Casting of TiAlNb Alloys with Different Velocities by Mixing
           Binary TiAl Ingot and Nb Wire 
    • Authors: Hong-Ze Fang; Rui-Run Chen, Dong Chai, Yao-Hua Yang, Yan-Qing Su, Hong-Sheng Ding, Jing-Jie Guo, Heng-Zhi Fu
      Abstract: A method of continuous casting is used and the research investigates microstructure and mechanical properties under different drawing velocity (R, mm/min). The results show that microstructure and composition measurement of different zones are uniform. The smallest grain size is 25.93 μm and formability is good with 0.5R. Compressive strength is higher with 0.5R and maximum value is 1697MPa. Fracture toughness with 0.5R improves about 35.7% which is 21.7MPa·m1/2. The fracture morphology is trans-lamellar fracture and interface de-lamination. The method is a feasible way to continuously cast the TiAl-Nb alloys. The R is an important parameter to add high-melting-point element, which affects solidified temperature interval of solidification front and electromagnetic stirring.A method is used to add high-melting-point element into TiAl-based alloy. Microstructure and composition measurement are uniform of liquid phase zone, mushy zone and stability zone with 0.5R. Another image is compressive strength and fracture toughness with different drawing velocity.
      PubDate: 2017-04-10T06:21:24.318075-05:
      DOI: 10.1002/adem.201700058
       
  • Effects of Void Array Orientation on Compressive Properties of Cellular
           Structures 
    • Authors: Karl Laurence Dahm; Peter Norman McGavin, Ian Willian Murray Brown
      Abstract: Additively manufactured cellular materials enable customized structural implants with superior osseointegration potential and mechanical properties better matched to bone. In this investigation, the compression response of Ti–6Al–4V alloy cellular materials comprising a simple cubic array of 2.00 mm diameter spherical voids with a 1.90 mm inter-void spacing are studied. Finite element analysis (FEA) shows that the lattice exhibited cubic symmetry with values for Young's modulus (E), Poisson's ratio, and shear modulus in the range of 28.5–29.5 GPa, 0.18–0.20, and 5.4–6.0 GPa, respectively. Compression tests carried out on cylinders with the same cellular structure fabricated by selective laser melting also show a strong dependence of elastic and plastic properties on orientation. Compression normal to the {100} plane of the simple cubic cell gives the highest E and strength, while compression normal to the {110} and {111} planes give lower values. The experimental E values for the {100} and {111} orientations show good agreement with the FEA results, but the {110} orientation shows lower values of E compared to the FEA predictions. Ultimate compressive failure of the cylinders occurred by gross slip along the {100} planes of the void array – coinciding with the slip planes for the simple cubic system.The mechanical properties of a cellular material comprising a simple cubic array of interconnected spherical voids show cubic elastic symmetry and therefore depend not only on the overall void content but also on the orientation of the applied load to the void array. Qualitatively, the mechanical response can be understood in terms of the {100} slip planes which have low shear strength and stiffness and provide a preferential failure plane as shown in the figure.
      PubDate: 2017-04-07T03:42:20.307864-05:
      DOI: 10.1002/adem.201700060
       
  • Bubble Size Distribution in Foaming of Liquid Aluminum and the Role of
           Coarsening and Coalescence 
    • Authors: Shiba Narayan Sahu; Amol Anant Gokhale, Anurag Mehra
      Abstract: Evolution of bubble size distribution in liquid aluminum foam prepared by dissociation of TiH2 particles is studied by rapidly cooling samples during foam expansion and carrying out metallographic analysis of the solidified foam. Further, diameters of bubbles growing directly on TiH2 particles are calculated to arrive at volume expansion and bubble size distribution. The cells in the solidified foam are orders of magnitude coarser and fewer than those predicted by the “pure growth” based model at all stages of foam expansion. If bubble coarsening was accounted for, the calculated bubble sizes are less than, but the same order of magnitude as the experimentally observed cell sizes. The remaining discrepancy of cell size (and population) can be explained based on bubble coalescence, strongly supported by observations on early stages of foaming.The study identifies bubble growth mechanisms operative in “Alporas” type aluminum foams by analyzing cell structures during foam evolution. Bubble growth based on pure diffusion under-predicts the average bubble size, while the classical LSW theory of coarsening predicts kinetics similar to that of later stage of foaming. The initial higher growth rate is attributed to bubble coalescence driven by bubble motion and hydrogen release rate.
      PubDate: 2017-04-07T03:42:12.221816-05:
      DOI: 10.1002/adem.201600745
       
  • Reproducible Superhydrophobic PVC Coatings; Investigating the Use of
           Plasticizers for Early Stage Biofouling Control
    • Authors: Robert Brown; Sonia Russell, Salina May, Fiona Regan, James Chapman
      Abstract: Here we show an easy to synthesize superhydrophobic material using a solvent phase–separation process of poly vinyl chloride. It is found that solvents mixed in different ratios increase the dielectric value of the solvent and can be tuned to produce superhydrophobic PVC. The PVC solution is then spin-coated onto glass slides for characterization using scanning electron microscopy. Plasticizers are doped into the 70% (v/v) PVC to determine their overall effects; it is found that plasticizers reduce the water contact angle value. The final coatings were tested in a series of antifouling assays in a marine environment lab study; it is found that the superhydrophobic PVC material reduced marine biofouling.The paper investigates the influence of surface hydrophobicity as a mechanism to reduce early stage marine biofouling. A solvent phase separation process to produce superhydrophobic water contact angle values (>150°) is performed and the materials show less early stage marine biofouling.
      PubDate: 2017-04-07T03:42:05.577989-05:
      DOI: 10.1002/adem.201700053
       
  • Fusion-Based Additive Manufacturing for Processing Aluminum Alloys:
           State-of-the-Art and Challenges
    • Authors: Anne I. Mertens; Jocelyn Delahaye, Jacqueline Lecomte-Beckers
      Abstract: The fusion-based additive manufacturing of Al alloys has been developing at an ever faster pace since early 2015, after a comparatively slow start with respect to other metallic materials. This paper reviews the recent developments with the aim of identifying challenges and opportunities for future work. Additive Al components possess strongly out-of-equilibrium microstructures resulting in potentially enhanced mechanical properties. A deeper understanding of the thermal history during fabrication, the design of new high strength alloys and the development of better adapted post-processing procedures are still needed to take full advantages of the specificities of additive manufacturing.The fusion-based additive manufacturing of Al alloys has been developing at an ever faster pace since early 2015, after a comparatively slow start with respect to other metallic materials. This paper reviews the recent developments with the aim of identifying challenges and opportunities for future work. Additive Al components possess strongly out-of-equilibrium microstructures resulting in potentially enhanced mechanical properties. A deeper understanding of the thermal history during fabrication, the design of new high strength alloys and the development of better adapted post-processing procedures are still needed to take full advantages of the specificities of additive manufacturing.
      PubDate: 2017-04-06T08:16:34.62729-05:0
      DOI: 10.1002/adem.201700003
       
  • Nanoporous Surface Modifications through Dealloying of Al–Ti
           Alloy 
    • Authors: Wei Zhao, Nianqi Liu, Jiacheng Rong, Lei E; Dan Zhao
      Abstract: TiO2 nanoporous structure was formed on the surface of Al–Ti alloy through a facile chemical corrosion method. The alloy composition, NaOH concentration, reaction time, and temperature played important roles in determining the morphology, elemental composition, phase composition, and the hydrophilic properties of the as-dealloyed samples. A uniform pore size distribution of a three-dimensional network structure was obtained with the diameter ranged from 100 nm to 2 μm. The obtained TiO2-based crystalline material exhibited good surface hydrophilic activity and light absorbency, which opened avenues in formation of porous nanostructures with high performance and low cost.A facile method for modifying TiO2A facile method for modifying TiO2 nano-porous surface is presented by chemical corrosion of Al–Ti alloy. The pores with three-dimensional continuous network in surface can be developed through controlling the Al content and alkali concentration, which may lead to a good surface hydrophilicity and light absorbance.
      PubDate: 2017-04-06T08:16:29.395702-05:
      DOI: 10.1002/adem.201600866
       
  • Self-Stiffening Behavior of Reinforced Carbon Nanotubes Spheres 
    • Authors: Peter Samora Owuor; Chandra Sekhar Tiwary, Ryota Koizumi, Matias Soto, Amelia C. Hart, Enrique V. Barrera, Robert Vajtai, Jun Lou, Pulickel M. Ajayan
      Abstract: Strong van der Waals forces between individual carbon nanotubes pose a major hurdle for effective use of nanotubes as reinforcement in nanocomposite due to agglomeration. In this paper, the authors show that van der Waals forces in combination with functionalization of carbon nanotubes, can be utilized to design nanocomposites mimicking stiffening behavior normally observed in biological materials such as fibrin gels, health bones, actin filaments in cytoskeletons etc. Carbon nanotube spheres are used as reinforcement in an elastomer matrix and when subjected to dynamic loads exhibit significant self-stiffening. Increased stiffness is also observed in dynamic loading after every relaxation cycle. The authors further show high energy absorption of the nanocomposite in impact tests.
      Authors study shows that the rational design of macroscale materials from nano-scale constituents can be achieved utilizing simple methodology to produce multifunctional materials with broad applications.Carbon nanotube spheres synthesized by taking advantage of strong van der Waals forces in combination with functional groups, used as reinforcement in the polymer matrix, show a self-stiffening behavior under dynamic loads and high energy absorption. A detailed FEM (finite element method) analysis supports the experimental observation.
      PubDate: 2017-03-15T09:35:40.806287-05:
      DOI: 10.1002/adem.201600756
       
  • In vitro Evaluation of Tribocorrosion Induced Failure Mechanisms at the
           Cell-Metal Interface for the Hip Implant Application 
    • Authors: Maria Runa; Eik-lang (Jenny) Lau, Christos Takoudis, Cortino Sukotjo, Tolou Shokuhfar, Luis Rocha, Mathew Mathew
      Abstract: In a hip joint environment, the bone-metal implant interface of an implant is exposed to the combined effect of wear and corrosion (tribocorrosion). This may create mechanical instability and cause early failure of the implants. The aim of this work was to investigate the tribocorrosion behavior of Ti6Al4V alloys in the presence of bone-forming cells cultured on its surface (cell-metal interface), using an electrochemical and tribological approach. The results showed that at a cathodic potential (−0.9 V), the presence of osteoblast-like cells and serum proteins in the media might induce a higher passivation rate of the oxide film, enhancing the corrosion resistance. However, when the surface is in steady state (0.7 V) they show a lower resistant to corrosion, increasing the susceptibility to corrosion.This work reports the interactions of the femoral stem part of the hip implants with the bone cells, the bio-tribocorrosion testing methods. This findings may contribute to a better understanding on the reason why physicians advise their orthopedic patients to have some level of physical activity after the surgery.
      PubDate: 2017-03-10T10:52:30.974412-05:
      DOI: 10.1002/adem.201600797
       
  • Influence of Substrate Temperature and Film Thickness on Thermal,
           Electrical, and Structural Properties of HPPMS and DC Magnetron Sputtered
           Ge Thin Films 
    • Authors: Andrej Furlan; Dario Grochla, Quentin D'Acremont, Gilles Pernot, Stefan Dilhaire, Alfred Ludwig
      Abstract: Ge was deposited as thickness gradient films at temperatures up to 800 °C by direct current (DC) and high power pulsed magnetron sputtering (HPPMS). Structural characterization shows increased crystallization with increasing substrate temperature and film thickness. Thermal conductivity was measured by a novel high-throughput time-domain thermo-reflectance method. Thermo-electrical properties correlate to the degree of crystallization. Conductivities increase with increasing substrate temperature up to 500 °C. For higher temperatures the trend reverses. A room temperature deposited/annealed film displays smaller crystallites (10 nm) and lower thermal conductivity (5 Wm−1 K−1) compared to 25 Wm−1 K−1 for hot DC deposition. Compared to DC, HPPMS films show higher thermal conductivities up to 45 Wm−1 K−1.Transport properties of magnetron sputtered Ge thin films are investigated for DC and HPPMS deposition methods and different substrate temperatures. As-determined transport properties are correlated to the films’ structural characteristics.
      PubDate: 2017-03-01T07:55:28.607693-05:
      DOI: 10.1002/adem.201600854
       
  • Advanced Structural Materials by Bioinspiration 
    • Authors: Flavia Libonati; Markus J. Buehler
      Abstract: In the quest of increasing safety and efficiency in structural applications, learning from natural materials can be a promising approach. Nature has evolved for billions of years to develop elaborate strategies, achieving optimal material solutions. A brief review of exemplar natural materials is provided here, with a focus on their multiscale structures. The design motifs, common to biological structural materials, are summarized, with a highlight on the structure-property relationship. A review of recent advancement in the manufacturing of bio-inspired composites is given, followed by recent and successful case studies. Finally, a critical discussion, highlighting the limitations of the current techniques, and prospecting the future challenges for the design of novel materials for engineering applications.Nature uses several strategies to turn weakness into strength. By combining few universal building blocks confined to a specific size and arranged into different substructures interacting through carefully designed interfaces, Nature is able to produce a large variety of multiscale hierarchical materials, which are efficient, multifunctional and sustainable.
      PubDate: 2017-02-23T08:56:08.947168-05:
      DOI: 10.1002/adem.201600787
       
  • Fabricating Three-Dimensional Periodic Micro Patterns on Photo-Resists
           Using Laser Interference Lithography 
    • Authors: Florian Rößler; Valentin Lang, Denise Günther, Andrés Fabián Lasagni
      Abstract: Springtails are hexapods, which have a complex skin surface composed of periodically arranged mushroom-like features. This topography offers surface functionalities like non-wetting and preventing bacterial settlement. This study demonstrates a novel way of replicating the morphology of the springtail skin using interference lithography. The micro patterns are produced with an undercut contour in a multilayer resist system on Si-wafers consisting of a lower lift-off resist and an upper photo-sensitive resist. After irradiation, several developing and rinsing steps are carried out to produce cavities in the lift-off resist layer with an undercut geometry directly below the SU-8 top layer.Mushroom geometries demonstrate outstanding surface functionalities such as non-wetting and prevention of bacterial settlement. This study focus on the development of a laser-based fabrication method to produce three-dimensional periodic patterns with undercuts irradiating a multilayered system of SU-8 and LOR using interference patterns.
      PubDate: 2017-02-21T03:00:34.925309-05:
      DOI: 10.1002/adem.201600855
       
  • Microstructure, Texture, and Mechanical Properties of Alternate α/β
           Mg–Li Composite Sheets Prepared by Accumulative Roll Bonding 
    • Authors: Feng Zhong; Tianzi Wang, Ruizhi Wu, Legan Hou, Jinghuai Zhang, Xinlin Li, Milin Zhang, Anping Dong, Baode Sun
      Abstract: Mg–5Li–1Al sheet and Mg–12Li–1Al sheet are used to prepare α/β Mg–Li composite sheets with accumulative roll bonding (ARB). The microstructure, texture, and mechanical properties of the specimens are investigated. Results show that, Mg–5Li–1Al alloy and Mg–12Li–1Al alloy alternatively distribute with uniform deformations and a good continuity, during the ARB process. With the increase in ARB passes, the hardness values of α layer and β layer increase, and the strength of composite sheet first increases, then maintains in a stable range. During the initial several passes, the elongation decreases, and it increases again after five passes. As for the texture density, with the increase in ARB passes, it first increases, then decreases. In the interface areas between sheets, a cross shear zone exists.Mg–5Li–1Al sheet and Mg–12Li–1Al sheet are used to prepare α/β Mg–Li composite sheets with accumulative roll bonding. The microstructure of the specimens is investigated. The texture and mechanical properties are improved. In the interface areas between sheets, a cross shear zone exists.
      PubDate: 2017-02-20T02:10:39.767714-05:
      DOI: 10.1002/adem.201600817
       
  • High-Quality Epitaxial MgB2 Josephson Junctions Grown by Molecular Beam
           Epitaxy 
    • Authors: Lin Li; Hui Zhang, Yi-Hang Yang, Guo-Xing Miao
      Abstract: Epitaxial MgB2 films are grown with molecular beam epitaxy (MBE) and optimized with the assistance of in situ reflection high-energy electron diffraction (RHEED). The RHEED patterns clearly revealed the evolution of film structures with growth temperatures and Mg:B ratio, providing the most direct guidance on optimizing growth conditions. A threshold temperature is identified, below which excess Mg will physically condense into the film, and above which excess Mg vaporizes right away leading to a self-limiting growth process for chemically-bound MgB2 phases. Hetero-epitaxial (0001)-MgB2/(111)-MgO/(0001)-MgB2 stacks are deposited and fabricated into micro Josephson junctions, which revealed clear Fraunhofer patterns and Fiske steps, indicating superb materials quality.Epitaxial MgB2 films are grown with molecular beam epitaxy (MBE) and optimized with the assistance of in situ reflection high-energy electron diffraction (RHEED). Hetero-epitaxial (0001)-MgB2/(111)-MgO/(0001)-MgB2 stacks are deposited and fabricated into micro Josephson junctions, which reveal clear Fraunhofer patterns and Fiske steps, indicating superb materials quality.
      PubDate: 2017-02-20T02:10:32.305715-05:
      DOI: 10.1002/adem.201600792
       
  • Metamaterial Based Passive Wireless Temperature Sensor 
    • Authors: Hasanul Karim; Diego Delfin, Luis A. Chavez, Luis Delfin, Ricardo Martinez, Jose Avila, Carlos Rodriguez, Raymond C. Rumpf, Norman Love, Yirong Lin
      Abstract: This paper presents the fabrication, modeling, and testing of a metamaterial based passive wireless temperature sensor consisting of an array of closed ring resonators (CRRs) embedded in a dielectric material matrix. A mixture of 70 vol% Boron Nitride (BN) and 30 vol% Barium Titanate (BTO) is used as the dielectric matrix and copper washers are used as CRRs. Conventional powder compression is used for the sensor fabrication. The feasibility of wireless temperature sensing is demonstrated up to 200 °C. The resonance frequency of the sensor decreases from 11.93 GHz at room temperature to 11.85 GHz at 200 °C, providing a sensitivity of 0.462 MHz °C. The repeatability of temperature sensing tests is carried out to quantify the repeatability. The highest standard deviation observed is 0.012 GHz at 200 °C.A metamaterial-based passive wireless temperature sensor is presented. Boron nitride and barium titanate are the ceramic materials used for the matrix, with embedded copper rings acting as closed ring resonators. The feasibility of wireless temperature sensing is demonstrated up to 200 °C. An average sensitivity of 0.462 MHz °C was achieved.
      PubDate: 2017-02-14T06:55:32.397089-05:
      DOI: 10.1002/adem.201600741
       
  • Precipitation and Hardness of Carbonitrides in a CrMnFeCoNi High Entropy
           Alloy
    • Authors: Mathilde Laurent-Brocq; Xavier Sauvage, Alfiya Akhatova, Loïc Perrière, Eric Leroy, Yannick Champion
      Abstract: In order to explore precipitation hardening, carbonitrides precipitates are formed within a CrMnFeCoNi high entropy alloy (HEA). The matrix and the precipitates are independently characterized by electron probe microanalysis, atom probe tomography, transmission electron microscopy, and nanoindentation. The matrix is a face-centered cubic multi-component non-equimolar solid-solution, that is, Cr depleted, which is stable and interestingly as hard as its equimolar counterpart. The precipitates are stable chromium carbonitrides with a micron-scale platelets morphology. They exhibit a hexagonal structure, are semi-coherent with the matrixm and are harder than the matrix.Carbonitride precipitates can be formed within a CrMnFeCoNi high entropy alloy (HEA). The matrix and the precipitates are independently characterized by EPMA, APT, TEM and nanoindentation. The matrix is a fcc multi-component non-equimolar solid-solution, which is stable and as hard as its equimolar counterpart. The precipitates are stable chromium carbonitrides which are semi-coherent with the matrix and harder than the matrix.
      PubDate: 2017-02-13T03:30:30.863939-05:
      DOI: 10.1002/adem.201600715
       
  • Strength and Ductility Balance on an Extruded
           Mg–Zn–Ca–La Alloy 
    • Authors: Yuzhou Du; Mingyi Zheng, Xiaoguang Qiao, Hongjun Chen, Bailing Jiang
      Abstract: Mg–6Zn–0.7Ca–0.2La (wt%) alloy is cast and extruded in the present study. The microstructure of the as-extruded Mg–6Zn–0.7Ca–0.2La (wt%) alloy is investigated via scanning electron microscopy (SEM), transmission electron microscope (TEM) and electron backscattering diffraction (EBSD). Results show that the as-extruded Mg–6Zn–0.7Ca–0.2La (wt%) alloy exhibited a balanced strength and ductility with the yield strength of 261 MPa and elongation-to-fracture of 20.7%. The superior strength is mainly attributed to grain refinement and precipitates, whereas the plasticity is ascribed to fine homogenous microstructure and weaker texture. The fine microstructure is obtained in the as-extruded Mg–6Zn–0.7Ca–0.2La (wt%) alloy, mainly attributing to the dynamic recrystallization and pinning effects from precipitates.The as-extruded Mg–6Zn–0.7Ca–0.2La (wt%) alloy exhibits fine-homogeneously DRXed microstructure and precipitates. Such microstructural characteristic gives rise to a balanced strength and ductility with the yield strength of 261 MPa and elongation-to-fracture of 20.7%.
      PubDate: 2017-02-08T07:23:05.21945-05:0
      DOI: 10.1002/adem.201600842
       
  • Orthogonal Wettability of Hierarchically Textured Metal Meshes as a Means
           of Separating Water/Oil Emulsions 
    • Authors: Thomas E. O'Loughlin; Sean Martens, Suchang Roy Ren, Patrick McKay, Sarbajit Banerjee
      Abstract: The removal of submicrometer-sized oil droplets from water remains a key challenge in engineering the separation of emulsions and has emerged as an urgent imperative given the increasing use of unconventional extractive processes. In this work, the authors demonstrate that a substrate with hierarchical texturation shows pronounced differences in the wettability of water and hexadecane, thereby, facilitating the separation of these two disparate liquids at room temperature and pressure. The multiscale textured substrates are assembled using a facile and readily scalable process, wherein ZnO nanotetrapods are spray-deposited onto a steel mesh with micron-sized features. Separation efficiencies well over 99% are accessible by simply flowing emulsions across these hierarchically textured surfaces.Hierarchically textured surfaces comprising steel meshes coated with ZnO nanotetrapods effectively separate the oil and water components of emulsions based on differential wettability at ambient temperature and pressure in a facile flow process. A scalable method allowing for greater than 99% separation efficiency has been realized for mechanical resilient substrates, paving the way to largescale industrial applications.
      PubDate: 2017-02-08T07:22:31.066077-05:
      DOI: 10.1002/adem.201600808
       
  • Facile Fabrication, Structures, and Properties of Laser-Marked
           Polyacrylamide/Bi2O3 Hydrogels 
    • Authors: Zheng Cao; Yanchao Hu, Qiang Yu, Ying Lu, Dun Wu, An Zhou, Wenzhong Ma, Yanping Xia, Chunlin Liu, Katja Loos
      Abstract: Laser marking of wet and soft polyacrylamide/bismuth oxide (PAM/Bi2O3) hydrogel materials can be achieved by simply embedding Bi2O3 particles inside PAM hydrogels and a subsequent laser treatment with a Nd: YAG laser beam at 1064 nm. In comparison with the pure hydrogel, the marking properties of the laser-marked PAM/Bi2O3 hydrogel samples vary as the Bi2O3 content increase from 0.17 to 3.0 wt% and as the laser power increase from 23.5 to 47.0 W. SEM, XPS, XRD, TGA, Raman spectroscopy, water contact angle and mechanical property tests are performed to characterize the laser-marked PAM/Bi2O3 hydrogels. The results herein indicate that the marking contrast and visual appearance on the surface of the PAM/Bi2O3 hydrogels after laser irradiation are mainly due to the decomposition of Bi2O3 to black bismuth metal.Laser marking of wet and soft PAM/Bi2O3 hydrogel materials can be achieved by simply embedding Bi2O3 particles inside PAM hydrogels and a subsequent laser treatment. The marking properties of hydrogels are determined by the Bi2O3 content and the laser power employed. The facile method is very promising for applications including the marking and decoration of soft and wet hydrogel products.
      PubDate: 2017-02-08T07:15:29.92965-05:0
      DOI: 10.1002/adem.201600826
       
  • Carbon Nanoparticle-Reinforced Metal Matrix Composites: Microstructural
           Tailoring and Predictive Modeling 
    • Authors: Leander Reinert; Sebastian Suarez, Thomas Müller, Frank Mücklich
      Abstract: Nickel matrix composites are produced with concentrations of 0.5–10 vol% of carbon nanotubes (CNT), onion-like carbon (OLC), or nanodiamonds (nD) as reinforcement phase by hot pressing. The effect of the carbon nanoparticle (CNP) type and concentration on the microstructure is analyzed. Grain sizes are measured and a model is adapted to predict the observed grain refinement for all CNP. The individual saturation concentration and maximum achievable grain refinement differs (for CNT: 3 vol%, OLC: 6.5 vol% and nD: 10 vol%), which is correlated to the agglomerate diameter distribution. This can be traced back to different hybridization states and different particle geometries, therefore providing valuable information for CNP-reinforced Metal matrix composites to a general extent.This work studies the effect of different carbon nanoparticles (CNP) on the final microstructure in metal matrix composites. A model based on the Zener equation is adapted to predict the observed grain refinement for all CNP, which can be correlated to the mean CNP agglomerate diameter distribution. As information regarding hybridization state and particle morphology of CNP is considered, valuable information for CNP-reinforced MMC is provided to a general extent.
      PubDate: 2017-01-31T04:21:03.270072-05:
      DOI: 10.1002/adem.201600750
       
  • In situ Observation of the Initial Stage of γ Lamella Formation in
           Ti48Al2Cr2Nb Alloy 
    • Authors: Xiaolei Li; Jinshan Li, Hongchao Kou, Lin Song
      Abstract: In situ observation is carried out in Ti48Al2Cr2Nb (at%) alloy to obtain a comprehensive understanding on the growth mechanisms of γ lamellae. The results reveal that the grain-boundary nucleated γ embryos occur first and grow into the adjacent α grains. Both the γ lamellae nucleated at the grain boundary and within α grain prefer to grow in pair by nucleation of the new γ lamella adjacent to the precedent γ lamella or branching of the growth tip. The widening of γ lamellae is controlled by the migration of α/γ interface, and the distance between growth pairs directly influences the lamellar width. The EBSD results exhibit that the two γ lamellae in growth pairs have a true-twin or pseudo-twin relationship. The underlying growth mechanism of γ lamellae is discussed.The growth process of γ lamellae in a Ti48Al2Cr2Nb alloy during high-temperature heterogeneous transformation is investigated. It is shown that γ lamellae prefer to grow in pair and the distance between growth pairs directly influences the lamellar width. The EBSD and TEM results demonstrate that the two γ lamellae generated by branching have same stacking sequence.
      PubDate: 2017-01-30T04:01:00.482628-05:
      DOI: 10.1002/adem.201600670
       
  • Enhance the Bioactivity and Osseointegration of the
           Polyethylene-Terephthalate-Based Artificial Ligament via Poly(Dopamine)
           Coating with Mesoporous Bioactive Glass 
    • Authors: Bin Yu; Peng Pei, Baoqing Yu, Dejian Li, Xu Zhang, Jianming Huang, Huifeng Ding, Shiyi Chen, Yufang Zhu
      Abstract: The objective of this study is to study the bioactivity and osseointegration of polyethylene-terephthalate-based artificial ligament coated with mesoporous bioactive glass (MBG) via polydopamine (PDA) in vitro and in vivo. In vitro, the OD value of MC3T3-E1 cells on PDA-MBG modified grafts is around 108% higher than that on pure PET after 5 days of culturing. The ALP activity of the PDA-MBG group is about 1.5 times higher than that of the control group after 7 days of culturing. In the in vivo study, the results demonstrated that more newly formed bone tissue was found and the ultimate failure load increased in the PDA-MBG coating group. In conclusion, PDA and MBG coating improves the surface bioactivity of the polyethylene-terephthalate-based artificial ligament and enhances the osseointegration within a bone tunnel.A straightforward method of PDA-MBG modification on an artificial ligament is used to promote its biocompatibility and bioactivity in vitro and in vivo. And the modified PET artificial ligament is shown to be an efficient process for enhancing the bioactivity of the PET. The surface modification on PET-based artificial ligament may be a novel applied for ligament reconstruction.
      PubDate: 2017-01-19T05:25:51.39963-05:0
      DOI: 10.1002/adem.201600708
       
  • Tri-Modal Microstructure Evolution in Near-β and Two Phase Field Heat
           Treatments of Conventionally Forged TA15 Ti-Alloy 
    • Authors: Zhichao Sun; Huili Wu, Min Wang, Jing Cao
      Abstract: Conventional forging combined with subsequent near-β and two-phase field heat treatments (NTH) is an attractive method to obtain a tri-modal microstructure in TA15 Ti-alloy. However formation and evolution of tri-modal microstructure mainly depend on NTH and distortion energy caused by forging. In this paper, influences of NTH parameters on the volume fraction and size of equiaxed αp and lamellar αs in tri-modal microstructure are revealed and the appropriate NTH conditions to obtain tri-modal microstructure with excellent comprehensive mechanical properties are determined.Tri-modal microstructure with excellent comprehensive mechanical properties is obtained by conventional forging (940 °C/60%/0.1 s–1/WQ) combined with subsequent near-β and two-phase field heat treatments (HT1 + HT2, 975 °C 30 min–1/WQ + 935 °C 100–120 min–1/AC) in TA15 Ti-alloy. Enhancing the near-β temperature (T1) decreases the volume fraction of αp –(αp%) and extending two phase field holding time (t2) increases the thickness of lamellar αs (Tαs).
      PubDate: 2017-01-12T01:36:02.442618-05:
      DOI: 10.1002/adem.201600796
       
  • Microstructure, Mechanical Properties, and Oxidation Behavior of
           AlxCr0.4CuFe0.4MnNi High Entropy Alloys 
    • Authors: Ziyuan Rao; Xun Wang, Qinjia Wang, Ting Liu, Xiaohua Chen, Lu Wang, Xidong Hui
      Abstract: AlxCr0.4CuFe0.4MnNi (x = 0, 0.1, 0.2, 0.3, 0.4) high entropy alloys (HEAs) were prepared by copper-mold casting. The effects of Al were investigated on the microstructure, tensile properties and oxidation behavior of these HEAs. It was shown that the addition of Al resulted in the formation of BCC and ordered BCC phases. The compositional heterogeneity between dendrites and interdendrites was alleviated when the content of Al was small. The mechanical properties of HEAs have been remarkably improved by the addition of Al. Considering the low cost and good mechanical properties, this kind of HEAs is rather competitive among HEAs for engineering application as structural materials. In this work, it was also shown that the oxidation resistance of current HEAs was significantly improved by the addition of Al.The effects of Al are investigated on the microstructure, tensile properties, and oxidation behavior of Cr0.4CuFe0.4MnNiAlx (x = 0, 0.1, 0.2, 0.3, 0.4) high entropy alloys. The mechanical properties of HEAs are remarkably improved by the small addition of Al. The HEAs exhibit a significant enhanced oxidation resistance after the addition of Al.
      PubDate: 2017-01-11T05:45:29.30674-05:0
      DOI: 10.1002/adem.201600726
       
  • Role of Interfaces on Multi-length Scale Wear Mechanics of TaC-based
           Composites 
    • Authors: Ambreen Nisar; Kantesh Balani
      Abstract: In the current work, contact-mechanics at different length scale is utilized to correlate damage accumulation in TaC-based composites. Upon synergistic reinforcement with silicon carbide (SiC) and carbon nanotubes (CNTs), TaC has shown to reduce the wear rate from 10.5 × 10−7 to 4.1 × 10−7 mm3 N−1 m−1 upon fretting (micro-wear) and from 8.0 to 2.7 mm3 N−1 m−1 upon micro-scratching (meso-wear). Enhancement in the fracture toughness from 2.9 to 10.7 MPam1/2 with reinforcement is attributed to the processing induced defects (such as dislocation, stacking fault etc.) in SiC and strong interfacial bonding of CNTs with TaC, as revealed by transmission electron microscopy (TEM). Delineation of the synergistic contribution of SiC and CNT reinforcement in TaC establishes the wear mechanism to be abrasion (via fretting test), brittle tensile cracking, and fracture (via micro-scratch test).The synergistic reinforcement of SiC and carbon nanotubes (CNTs) in TaC, as T15S15C composite, provides an increased fracture toughness (KIC), and scratch- (SR) and tribological-resistance (WR), which is rationalized by comparing micro-scratching and fretting wear to elicit multi-length scale damage mechanics.
      PubDate: 2017-01-04T03:05:42.911267-05:
      DOI: 10.1002/adem.201600713
       
  • Rapid Densification of Carbon/Carbon Composites Plate by Pressure-Gradient
           Chemical Vapor Infiltration 
    • Authors: Li Hong Xia; Bo Yun Huang, Fu Qin Zhang, Lei Jin, Da Chen, Qian Tang
      Abstract: Carbon/carbon (C/C) composites plate is prepared in the temperature range 1 223–1 373 K by improved pressure-gradient chemical vapor infiltration (CVI). The bulk densities and pore distributions of C/C composites after different infiltration period are measured and the densification kinetics is investigated. The results show that C/C composites plate with 300 × 300 × 15 mm is able to be densified to 1.52 g cm−3 within 60 h by pressure-gradient CVI. The porosity of pores with a size larger than 60 µm reduces markedly and the large pores are able to be filled more effectively by pressure-gradient CVI. The densification kinetics depends on the temperature and competition between reaction and convection mass transport. The activation energy is about 366 kJ mol–1at 1 223–1 313 K and 43.2 kJ mol−1 above 1 313 K.A C/C composite plate sized 300 × 300 × 15 mm is fabricated efficiently and rapidly by improved pressure-gradient (CVI). For 60 h infiltration, the average bulk density is up to 1.52 g cm–3 and the densification rate is three times higher than that of isobaric CVI. In addition, the pore filling and kinetics analysis confirm the advantages of the new densification process.
      PubDate: 2016-09-26T06:35:39.81495-05:0
      DOI: 10.1002/adem.201600329
       
 
 
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