for Journals by Title or ISSN
for Articles by Keywords
  Subjects -> COMPUTER SCIENCE (Total: 1974 journals)
    - ANIMATION AND SIMULATION (29 journals)
    - AUTOMATION AND ROBOTICS (97 journals)
    - COMPUTER ARCHITECTURE (9 journals)
    - COMPUTER ENGINEERING (10 journals)
    - COMPUTER GAMES (16 journals)
    - COMPUTER PROGRAMMING (23 journals)
    - COMPUTER SCIENCE (1148 journals)
    - COMPUTER SECURITY (45 journals)
    - DATA BASE MANAGEMENT (12 journals)
    - DATA MINING (32 journals)
    - E-BUSINESS (22 journals)
    - E-LEARNING (27 journals)
    - IMAGE AND VIDEO PROCESSING (40 journals)
    - INFORMATION SYSTEMS (101 journals)
    - INTERNET (91 journals)
    - SOCIAL WEB (50 journals)
    - SOFTWARE (33 journals)
    - THEORY OF COMPUTING (8 journals)

COMPUTER SCIENCE (1148 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: 20)
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: 11)
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: 11)
Advanced Engineering Materials     Hybrid Journal   (Followers: 25)
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: 15)
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: 10)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 24)
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: 37)
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: 14)
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 and Museum Informatics     Hybrid Journal   (Followers: 124)
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: 8)
Basin Research     Hybrid Journal   (Followers: 3)
Behaviour & Information Technology     Hybrid Journal   (Followers: 52)
Bioinformatics     Hybrid Journal   (Followers: 236)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 17)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 32)
Briefings in Bioinformatics     Hybrid Journal   (Followers: 45)
British Journal of Educational Technology     Hybrid Journal   (Followers: 122)
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: 13)
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: 14)
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: 19)
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: 51)
Communications of the Association for Information Systems     Open Access   (Followers: 18)
COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering     Hybrid Journal   (Followers: 3)
Complex & Intelligent Systems     Open Access  
Complex Adaptive Systems Modeling     Open Access  
Complex Analysis and Operator Theory     Hybrid Journal   (Followers: 2)
Complexity     Hybrid Journal   (Followers: 6)
Complexus     Full-text available via subscription  
Composite Materials Series     Full-text available via subscription   (Followers: 9)
Computación y Sistemas     Open Access  
Computation     Open Access  
Computational and Applied Mathematics     Hybrid Journal   (Followers: 2)
Computational and Mathematical Methods in Medicine     Open Access   (Followers: 2)
Computational and Mathematical Organization Theory     Hybrid Journal   (Followers: 2)
Computational and Structural Biotechnology Journal     Open Access   (Followers: 2)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Astrophysics and Cosmology     Open Access   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computational Cognitive Science     Open Access   (Followers: 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: 13)
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: 28)
Computer     Full-text available via subscription   (Followers: 81)
Computer Aided Surgery     Hybrid Journal   (Followers: 3)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 6)
Computer Communications     Hybrid Journal   (Followers: 10)
Computer Engineering and Applications Journal     Open Access   (Followers: 5)
Computer Journal     Hybrid Journal   (Followers: 7)
Computer Methods in Applied Mechanics and Engineering     Hybrid Journal   (Followers: 22)
Computer Methods in Biomechanics and Biomedical Engineering     Hybrid Journal   (Followers: 10)
Computer Methods in the Geosciences     Full-text available via subscription   (Followers: 1)
Computer Music Journal     Hybrid Journal   (Followers: 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: 11)
Computer Science Education     Hybrid Journal   (Followers: 12)
Computer Science Journal     Open Access   (Followers: 20)
Computer Science Master Research     Open Access   (Followers: 10)

        1 2 3 4 5 6 | Last

Journal Cover Advanced Engineering Materials
  [SJR: 0.81]   [H-I: 81]   [25 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  [1583 journals]
  • Ceramic Fibers Reinforced Functionally Graded Thermal Barrier Coatings
    • Authors: Chang Wang; Xiufang Cui, Guo Jin, Zonghong Gao, Jiannong Jin, Zhaobing Cai, Yongchao Fang
      Abstract: The long-term durability is a considerable challenge for the use of thermal barrier coatings (TBCs). In order to solve this problem, introduction of yttria-stabilized zirconia (YSZ) short fibers in functionally graded system is employed to strengthen the durability of TBCs. Four coatings are deposited on In738LC substrate by atmospheric plasma spray (APS). Thermal cycling behaviors and fiber toughening mechanisms of coatings are systematically studied. Result shows that the thermal cycling lifetime of graded TBCs with the addition of fibers can reach 406 ± 21 at 850 °C, which increases by 60% compared to that of typical APS YSZ TBCs. Moreover, the improvement of lifetime mainly attributes to the fiber breakage, the fiber-matrix interface debonding, and the crack deflection.In this study, a novel method, namely, introduction of yttria-stabilized zirconia (YSZ) short fibers in functionally graded system, is used to solve the long-term durability of TBCs. Thermal cycling lifetime of this TBC is improved greatly. The improvement is mainly attributed to the fiber breakage, the fiber-matrix interface debonding, and the crack deflection.
      PubDate: 2017-06-23T03:32:30.183391-05:
      DOI: 10.1002/adem.201700149
  • Back Cover: Advanced Engineering Materials 6∕2017
    • Abstract: B2(ω) phase in TiAl alloy is unstable at evaluated temperatures involving complex stress, as reported in article number 1600844 by Jieren Yang and co-workers. The transition of B2 ω, and the ω B2 transition occur according to temperature and stress. The nature of the reversible transition is the collapse of atomic layer in B2 phase, and the ω phase can transfer to the B2 phase at higher temperatures. An additional pressure can play a positive role in the transition of B2 ω, and the ω B2 transition would be suppressed under external pressure.
      PubDate: 2017-06-21T07:19:21.304745-05:
      DOI: 10.1002/adem.201770021
  • Masthead: Adv. Eng. Mater. 6∕2017
    • PubDate: 2017-06-21T07:19:20.612112-05:
      DOI: 10.1002/adem.201770019
  • Contents: Adv. Eng. Mater. 6∕2017
    • PubDate: 2017-06-21T07:19:19.38974-05:0
      DOI: 10.1002/adem.201770020
  • Editorial: Titanium Alloys: Properties, Processing and Applications
    • PubDate: 2017-06-21T07:19:17.600141-05:
      DOI: 10.1002/adem.201700168
  • Front Cover: Advanced Engineering Materials 6∕2017
    • Abstract: By integrating parametric modeling with multi-material 3D printing, James C. Weaver, Henrik Birkedal and co-workers describe an effective approach for identifying design elements critical for mechanical performance in multiphase biological composites in article number 1600848. The cover image demonstrates one such example, with the background photograph of a transparent 3D-printed nacre structural analogue overlaid with a color SEM image of its fracture surface.
      PubDate: 2017-06-21T07:19:16.829696-05:
      DOI: 10.1002/adem.201770018
  • Hot Rectangular Extrusion Textures of Six Mg-Alloys Via Neutron
    • Authors: Heinz-Günter Brokmeier
      Abstract: Due to the high quality and statistics utilizing neutron diffraction for texture analyses, the crystallographic texture variation of six Mg-alloys is described in detail (AM20–AZ31–AZ61–AZ91–ZC71–WE43). More or less in all cases, the crystallographic texture is composed of some ideal texture components such as {0001} and {10–10} and fiber components such as  // ND and  // ED. There is a dependency of the existence and texture sharpness of texture components with alloying elements such as the amount of Al. ZC71 is special with one dominating texture component {10–10} . WE43 shows the split of the central pole in the basal pole figure but texture components are identical to other alloys without the tilt.Crystallographic texture of rectangular hot extruded Mg-alloys show a strong variation in texture type and texture sharpness. Examples show the (0002) and the (10–10) pole figures of Mg-AZ61 and MG-ZC71, first one with strong deformation texture and second one with strong recrystallization texture.
      PubDate: 2017-06-19T02:21:02.739758-05:
      DOI: 10.1002/adem.201700234
  • Improving Mechanical Properties of cp Titanium by Heat Treatment
    • Authors: Francis Wagner; Abdelouahab Ouarem, Thiebaud Richeton, Laszlo S. Toth
      Abstract: The yield stress and the ductility are very important mechanical quantities for materials selection. The paper deals with the question: how far is it possible to increase the yield stress without a significant loss of ductility by optimizing the final heat treatment in the elaboration stage. Commercially pure titanium sheets are subjected to different thermo-mechanical treatments to produce seven metallurgical states. The textures and the microstructures of the samples are studied by Electron Back Scattering Diffraction measurements, the mechanical behavior by tensile testing along the previous rolling, and the transverse directions of the sheet. The obtained microstructures display different grain sizes and varying fractions of recrystallized grains, together with slightly dissimilar textures. The yield stress increases with the decreasing grain size and obeys the classical Hall–Petch law. The grain size reduction results in a small decrease of ductility for extension along the rolling direction when the recrystallized volume fraction is higher than 80%. For extension along the transverse direction, however, the homogeneous deformation strongly decreases as soon as the material contains a small fraction of non-recrystallized grains. A good compromise between high yield stress and ductility is identified in a metallurgical state close to the end of primary recrystallization. This material state insures a relatively small grain size with all grains being in a recrystallized state.Mechanical properties are determined for cp titanium sheets after various heat treatments leading to different states (full or partial recrystallyzation). The YS increases without significant loss of ductility due to grain size and texture. Anisotropy is taken into account to define the best compromise.
      PubDate: 2017-06-19T02:20:42.877674-05:
      DOI: 10.1002/adem.201700237
  • Life-Cycle Assessment of Solar Charger with Integrated Organic
    • Authors: Gisele A. dos Reis Benatto; Nieves Espinosa, Frederik C. Krebs
      Abstract: Organic photovoltaics (OPV) applied in a commercial product comprising a solar charged power bank is subjected to a life cycle assessment (LCA) study. Regular power banks harvest electricity from the grid only. The solar power bank (called HeLi-on) is however, a power bank that includes a portable OPV panel, enabling the possibility to be charged from the sun, and not only from the grid. In this paper, two well-established power bank products using amorphous silicon solar panels (a-Si PV) and a regular power bank without any portable solar panel is compared to HeLi-on. The environmental impact of the products is quantified with the aim of indicate where eco-design improvements would make a difference and to point out performance of a portable solar panel depending on the context of use (Denmark and China), realistic disposal scenarios and the recycling relevance particularly concerning metals content.Ecodesign of electronic equipment as a key action supporting circular economy, reduce the energy consumption and other environmental impacts occurring throughout their life cycle. In this study, a new organic photovoltaic-based solar charger produced according to circular economy principles, is compared to well-established products in terms of environmental performance when used and disposed in Denmark or China, indicating ecodesign improvements.
      PubDate: 2017-06-16T07:56:03.278672-05:
      DOI: 10.1002/adem.201700124
  • Large-Scale Synthesis of Nanostructured Nitride Layer on Ti Plate Using
           Mechanical Shot Peening and Low-Temperature Nitriding
    • Authors: Quantong Yao; Jian Sun, Depeng Shen, Weiping Tong, Liang Zuo
      Abstract: A nanostructured nitride layer is produced on a large titanium plate using mechanical shot peening (MSP) followed by a low-temperature gaseous nitriding method. The combined effect of the MSP and low-temperature nitriding on the microstructural evolution and mechanical properties is investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, as well as hardness, wear resistance, and toughness tests. The results of the characterization are compared to a coarse-grained specimen produced by a standard nitriding process. The results show that a nitride layer with a thickness of 10–15 µm is produced on the MSP-treated Ti plate after nitriding at 550 °C for 5 h. The nitride layer is composed of nanostructured ϵ-TiN and γ-Ti2N phases with a high supersaturation of nitrogen. The nitriding kinetics is significantly enhanced by the nanocrystalline structure. The surface hardness, thickness of the hardened layer, and wear resistance of the nitrided MSP Ti plate are all enhanced relative to the coarse-grained nitrided sample. The toughness of the nanostructured nitrides is greatly improved compared with the conventional nitrided specimen.The authors firstly realize surface nanocrystallization technology in industrialization application. The gaseous nitriding can be performed on Ti plate at low nitriding temperature of 550 °C by nanocrystalline layer assistance. The nitrided layer thickness and toughness are significantly improved comparing with that of the coarse-grained nitrided specimen.
      PubDate: 2017-06-16T07:55:55.708924-05:
      DOI: 10.1002/adem.201700157
  • In Situ Study of Deformation Twinning and Detwinning in Helium Irradiated
           Small-Volume Copper
    • Authors: Wei-Zhong Han; Ming-Shuai Ding, R. Lakshmi Narayan, Zhi-Wei Shan
      Abstract: The influence of nanoscale helium bubbles on the deformation twinning and detwinning behavior of submicron-sized Cu is investigated under tension, compression, and cyclic loading. In situ nanomechanical tests performed inside a transmission electron microscope reveal that twinning and detwinning occur readily in helium irradiated copper under both tension and compression. Continuous shearing of helium bubbles by Shockley partials leads to twin formation, whereas the residual back-stress accumulated from dislocation-bubble interactions assist in detwinning. These interactions also elevate the critical shear stress for partial dislocation slip in helium irradiated Cu compared to that in fully dense Cu. The growth twin boundaries can significantly enhance the twinning stress in helium irradiated Cu pillar, and deformation twin-growth twin boundary interaction promotes the formation of internal crack and thus accelerates failure. The effect of crystallographic orientation and sample size on the overall deformation characteristics of helium irradiated Cu is briefly discussed. The current studies show that deformation twinning and detwinning are also active deformation models in helium irradiated small-volume copper.In situ nanomechanical tests performed inside a transmission electron microscope reveal that twinning and detwinning occur readily in helium irradiated copper under both tension and compression. Continuous shearing of helium bubbles by Shockley partials leads to twin formation whereas the residual back-stress accumulated from dislocation-bubble interactions assist in detwinning.
      PubDate: 2017-06-16T01:00:29.347648-05:
      DOI: 10.1002/adem.201700357
  • Densification and Crystallization in Fe–Based Bulk Amorphous Alloy Spark
           Plasma Sintered in the Supercooled Liquid Region 
    • Authors: Tanaji Paul; Ashish Singh, Sandip P. Harimkar
      Abstract: Spark plasma sintering of Fe48Cr15Mo14Y2C15B6 bulk amorphous alloy at a range of temperatures in the supercooled liquid region (SLR) and above yielded near fully dense compacts. Upon sintering in the temperature range of 570–630 °C in SLR, large increments in density are observed due to enhanced sintering resulting from drastic reduction in the viscosity of the alloy. Above 630 °C, the absence of sufficient driving force for sintering and stiffening of the amorphous matrix from partial crystallization leads to sluggish densification. Analysis of the temperature profile in the sample and the die reveals that the temperature at the center of the sample is higher than that at the inner wall of the die as recorded by the thermocouple and the difference between the two is estimated to be between 31 and 53 °C.Spark plasma sintering of Fe48Cr15Mo14Y2C15B6 bulk amorphous alloy in the supercooled liquid region and above results in large densification upto 630 °C, due to reduction in viscosity and sluggish thereafter upto 800 °C due to (Fe,Cr)23(C,B)6 nanocrystallization induced matrix stiffening. The difference between the temperature at the center of the sample and that measured by the thermocouple is 31–53 °C.
      PubDate: 2017-06-16T01:00:22.596788-05:
      DOI: 10.1002/adem.201700224
  • Mechanical Behavior and Adhesion of the Ti/Cr/Au Metallization Scheme on
           Diamond Substrate
    • Authors: Sabeur Msolli; Joel Alexis, Heungsoo Kim
      Abstract: The mechanical properties of a Ti/Cr/Au metallization system deposited on a heavily doped diamond substrate are evaluated, first using nano-indentation tests. Various kinds of conditions are adopted, such as small and high force loadings. These tests are completed by in situ scanning electron microscopy observations of the surface. The adhesion of such multilayer on the diamond substrate is assessed using nano-scratching tests. The profiles of the obtained scratches are analyzed to detect any singularities or defects. Finally, a cross-section topography is performed, in order to obtain the cross profile of the scratch, and to determine the scratch hardness parameter of the metallization system. The Ti/Cr/Au metallization system is a potential candidate to play the role of ohmic contact on diamond. Therefore, its adhesion to diamond is important, since the whole power electronic assembly is mainly subjected to thermal cycling during service. The metallization system must adhere well to diamond, so as to resist temperature gradients and thermal strains that are widely observed in extreme thermal conditions. Otherwise, debonding phenomena may occur, and the whole electronic packaging fail.After the deposition of Ti/Cr/Au metallization system on diamond, microstructural analyzes of the deposit using SEM observations, EDX analysis, and EDS mapping show no viewable defects on the deposit surface. Nano-indentation tests prove that the deposit has a good mechanical behavior under mechanical loading. Finally, nano-scratching tests attest of the good adhesion of the deposit on diamond (see figure).
      PubDate: 2017-06-14T15:32:00.481262-05:
      DOI: 10.1002/adem.201700109
  • Dynamic Corrosion and Material Characteristics of Mg–Zn–Zr Mini-Tubes:
           The Influence of Microstructures and Extrusion Parameters
    • Authors: Da-Jun Lin; Fei-Yi Hung, Heng-Jui Liu, Ming-Long Yeh
      Abstract: In this study, magnesium–zinc–zirconium (Mg–Zn–Zr) alloy mini-tubes that fit the diameter of cardiovascular stents are successfully fabricated using an isothermal extrusion method. The influence of extrusion temperature and ram speed on the microstructure are examined. In addition, this research develops a novel dynamic-corrosion apparatus for Mg alloy mini-tube examination, and supplemented with electrochemical, and biocompatibility tests, the optimal criteria for mini-tube extrusion are defined. The optimized specimen not only retains a homogeneous fine-grained structure with a grain size of about 2 µm, but also possesses 300 MPa yielding strength and nearly 15% elongation. Compared with a coarse-grained microstructure, the fine-grained specimens significantly reduces the corrosion and oxidation rates in a dynamic-flow field, resulting in favorable characteristics of degradation, cytocompatibility, and hemocompatibility. The results suggest that precisely controlling the extrusion process can improve the mechanical properties as well as the biocompatibility of Mg alloys for application in cardiovascular implants.The Mg mini-tube is developed for cardiovascular stent application. The extrusion parameter dominates the microstructure, which results in a significant increase in enhanced mechanical properties and corrosion resistance. A new dynamic corrosion test is performed in order to determine the practicability of fine-grained Mg mini-tube.
      PubDate: 2017-06-14T01:56:13.023829-05:
      DOI: 10.1002/adem.201700159
  • Influence of Foam Morphology on Effective Properties Related to Metal Melt
    • Authors: Eric Werzner; Martin Abendroth, Cornelius Demuth, Christoph Settgast, Dimosthenis Trimis, Hartmut Krause, Subhashis Ray
      Abstract: In this article, a numerical study on the sensitivity, related to the performance of open-cell foams used for the depth filtration of liquid metals, on two characteristic morphological properties is presented. Therefore, simulations of fluid flow and particle transport inside an artificial foam structure are carried out, whose porosity and strut shape is varied within a certain expected range. For comparison purposes, however, the simulations are also performed for three typical ceramic foam filters (CFF) with pore densities of 20 and 30 PPI, whose geometries are obtained from CT scans. In order to allow for a comparison between the different structures, a reference length is introduced that relies upon the actual ratio of pores per volume. The evaluation is mainly based on the comparison of the hydraulic tortuosity, the viscous and the inertial permeability coefficients as well as the initial filtration coefficient for alumina inclusions, with their size ranging from of 10 to 40 μm at process conditions typically encountered during the aluminum filtration. It is shown that the ratio of filtration coefficient and pressure drop increases with the porosity, while the material distribution between the struts and the joints is less influential. Finally, the article also provides information on the anisotropy of CFFs and on the transition behavior from steady to unsteady flow in open-cell foams.This article presents a numerical investigation on the sensitivity of permeability, hydraulic tortuosity, and filtration coefficient of open-cell foams used for metal melt filtration regarding their porosity and strut shape for conditions typically observed during the continuous casting of aluminum. The predicted results are compared against three samples of real ceramic foam filters obtained through CT scanning.
      PubDate: 2017-06-13T08:06:18.790058-05:
      DOI: 10.1002/adem.201700240
  • Intermetallic Sludge Formation in Fe Containing Secondary Al–Si Alloys
           Influenced by Cr and Mn as Preparative Tool for Metal Melt Filtration
    • Authors: Björn G. Dietrich; Hanka Becker, Michal Smolka, Andreas Keßler, Andreas Leineweber, Gotthard Wolf
      Abstract: In view of filtration of Fe-enriched intermetallics to decrease Fe content in secondary aluminum alloys, the formation of so-called sludge particles has been investigated depending on dwell time and chemical composition using an AlSi9Cu3 secondary alloy with high Fe content. To evaluate the dwell time dependency, samples are cast into ceramic crucibles and held at 620 °C for varying times. Furthermore, Mn and Cr have been added to the melt in different amounts and the alloys are treated for 6 h at 620 °C. The samples are analyzed using light optical micrographs and image analysis to reveal particle sizes and distribution as well as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD) for phase identification. It is found that the growth of Fe containing sludge particles stagnates after reaching a specific value and is not significantly affected by ultra-long dwell times. Mn addition has a minor effect on the the particle size distribution preserving large particle sizes, whereas Cr addition leads to a smaller sludge particles. Generally, the sludge consists of the cubic α-phase. Additionally in the presence of Cr, Fe, and Cr concentration gradients occur in the cubic α–Al–(Fe,Mn,Cr)–Si phase and the Al13Cr4Si4-phase is contained in the centers of the sludge particles. It is concluded that Mn addition is favored due to larger particle size and higher efficiency to bind Fe in the α-phase than by Cr or Cr and Mn addition.In view of a future application of novel filter materials for filtration of iron containing intermetallic phases so called “sludge” to reduce Fe-content in secondary aluminum alloys, the formation of sludge particles depending on melt treatment and varying amounts of Mn and Cr is investigated.
      PubDate: 2017-06-09T14:46:08.728656-05:
      DOI: 10.1002/adem.201700161
  • Effect of Directional Solidification Variables on the Microstructures of
           Single-Crystal Turbine Blades of Nickel-Based Superalloy
    • Authors: Fu Wang; Zining Wu, Dexin Ma, Andreas Bührig-Polaczek
      Abstract: Single-crystal turbine blades of nickel-based superalloy are directionally solidified at different withdrawal rates of 0.0017 cm s−1–0.01 cm s−1 aiming to investigate the evolution of as-cast microstructures. The results show that the average primary and secondary dendrite arm spacings, λ1¯ and λ2¯, decrease with increasing withdrawal rate, although the complicated geometry of the blades results in local nonhomogeneity of dendrite arm spacings. The experimentally achieved values of λ1¯ can be reasonably predicted by Ma and Sahm's theoretical model, in which the effect of the secondary dendrite on the primary dendrite arm spacing is considered. With increasing withdrawal rate, the shape of the γ/γ′ eutectic varies from a large block-like eutectic island to an interconnected small strip-like morphology. In addition to this, the average size of the γ/γ′ eutectic gradually decreases with increasing withdrawal rate. A reduction in the average sizes of the γ′ precipitates in the dendrite core and interdendritic region is also observed with increasing withdrawal rate. The microsegregation levels of Al, Ti, Ta, Cr, Co, and Mo are alleviated with increasing withdrawal rate.SC blades are directionally solidified at various withdrawal rates (V) to study the evolution of microstructures. The microstructures are refined with increasing V, although the geometry of blades results in local nonhomogeneous microstructures. λ1¯ can be predicted by Ma and Sahm's model. The microsegregation levels of alloying elements are alleviated with increasing V.
      PubDate: 2017-06-09T14:46:06.528927-05:
      DOI: 10.1002/adem.201700297
  • Influence of Torsion Route on the Microstructure and Mechanical Properties
           of Extruded AZ31 Rods
    • Authors: Bo Song; Xiaogang Shu, Hucheng Pan, Guoqiang Li, Ning Guo, Tingting Liu, Linjiang Chai, Renlong Xin
      Abstract: Torsion deformation is an effective and simple technique to tailor the mechanical properties of Mg alloys. In this study, the influences of torsion route on microstructure and mechanical properties of AZ31 rods are investigated. The maximum torsion angle is set as 180° and the two-pass torsion at different torsion routes, twice-successive unidirectional torsion (TA) and reciprocating torsion (TB), is used to process the Mg alloy rods. It is found that the mechanical properties and yield asymmetry are very sensitive to the torsion route. Route TA is more effective for the enhancement of compressive yield strength and the improvement of yield asymmetry, while route TB is more effective for the enhancement of tensile yield strength. It is mainly attributed to the different textural evolutions between the two torsion routes. The relevant mechanisms are addressed and discussed.Torsion deformation is an effective and simple technique to tailor the mechanical properties of Mg alloys. It is found that the mechanical properties and yield asymmetry are very sensitive to the torsion route. Route TA is more effective for the enhancement of compressive yield strength and the improvement of yield asymmetry, while route TB is more effective for the enhancement of tensile yield strength.
      PubDate: 2017-06-09T07:40:27.919944-05:
      DOI: 10.1002/adem.201700267
  • Increased Mechanical Stability and Thermal Conductivity of Alumina
    • Authors: Stefan Rannabauer; Gerrit-Maximilian Söffker, Marcel Scheunemann, Ulf Betke, Michael Scheffler
      Abstract: Infiltration processing of reticulated porous alumina ceramics (RPC) from reticulated foam manufacturing is investigated by micro computed tomography. Infiltration is carried out with colloidal alumina slurries. Successful infiltration is found to be a function of the RPCs starting microstructure and the particle size of the alumina in the colloidal infiltration system. Suitable infiltration conditions are specified. As a result, RPCs with a low relative density show a fivefold compressive strength after infiltration, as compared to their non-infiltrated RPC counterparts. The highest strength of infiltration processed alumina RPCs at a porosity of 90% is found to be 1.6 MPa, and besides a significant increase of the compressive strength, the thermal conductivity is improved to be 1.5 W m−1 K−1 after infiltration.Infiltration of RPC with colloidal alumina slurries is investigated with respect to the colloidal particle size. Classifying the RPCs’ pore system into different pore orders, the distribution of the colloidal particles is examined by micro computed tomography. The infiltration results in a significant improvement of the struts and thereby the RPC.
      PubDate: 2017-06-09T07:35:27.227864-05:
      DOI: 10.1002/adem.201700211
  • Accumulative Roll Bonding at Room Temperature of a Bi-Metallic
           AA5754/AA6061 Composite: Impact of Strain Path on Microstructure, Texture,
           and Mechanical Properties 
    • Authors: Kevin Verstraete; Hiba Azzedine, Anne-Laure Helbert, François Brisset, Djamel Bradai, Thierry Baudin
      Abstract: Accumulative roll bonding (ARB) is performed at room temperature on an aluminum composite up to five rolling cycles, using two different paths: the conventional one (ARB) and the cross ARB (CARB) one consisting of a 90° rotation of the rolling direction before each rolling pass. The microstructure is refined faster by CARB than by ARB occasioning higher yield strength of the elaborated samples. Besides, CARB has the ability to delay the loss of stratification of the composite. The resulting textures are different: while ARB promotes typical rolling components (Brass {011}, Goss {110}, Dillamore {4 4 11}), S {123}), CARB promotes the ND-rotated Brass {011} instead of Brass together with the S and Dillamore components. A Visco-Plastic Self-Consistent (VPSC) simulation highlights that the ND-rotated Brass had Brass and S components for origin. The ND-rotated Brass presence in the texture promotes a better mechanical isotropy of the composite sheet.Accumulative Roll Bonding (ARB) on dissimilar alloys leads to an enhancement of the strength, but the typical fracture of the hard phase interfere with this evolution. A rotation of the sample between each rolling (using CARB) may delay this issue. Besides, two consequences of this rotation are significant: an enhancement of the composite's strength and an original texture.
      PubDate: 2017-06-08T04:45:30.717688-05:
      DOI: 10.1002/adem.201700285
  • Novel Heating Elements for Induction Welding of Carbon Fiber/Polyphenylene
           Sulfide Thermoplastic Composites
    • Authors: Rouhollah Dermanaki Farahani; Martine Dubé
      Abstract: Conductive films of carbon nanofibers (CNFs) decorated/coated with metals, either silver (Ag) or nickel (Ni) are fabricated using a solution casting process and used as novel heating elements (HEs) for induction welding of carbon fiber/polyphenylene sulfide (CF/PPS) thermoplastic composites. Prior to making the films, the metal-coated CNFs are prepared by an electroless plating method using Ag or Ni precursors. A solution of the metal-coated CNFs is then casted onto a pure PPS film to give a robust conductive film upon solvent evaporation and annealing in an oven at 200 °C. SEM observation and electrical resistivity measurements reveal that the CNFs are successfully coated with the metals which result in a significant decrease of the films’ electrical resistivity. A third type of HE is also fabricated by solution mixing Ag-coated CNFs and magnetic Fe3O4 nanoparticles. The welding efficiency of the fabricated films is assessed for induction welding of two different types of thermoplastic composites, that is, unidirectional pre-impregnated 16 plies ​​of CF/PPS compression-molded in a quasi-isotropic stacking sequence and 8-ply of satin weave fabric CF/PPS compression-molded in a cross-ply stacking sequence. The mechanical apparent lap shear strength (LSS) of the induction-welded joints is evaluated for the fabricated HEs and compared with the LSS of joints welded using conventional stainless steel mesh susceptors. Under similar testing conditions, Ag-coated CNFs HEs lead to the highest LSS with an average value of ≈31.5 MPa. In general, the new HEs result in superior LSS and higher heating rates when compared to the metallic mesh counterparts. The present work offers a new perspective to push the boundaries toward high quality welding of thermoplastic composites using nanomaterials-based HEs.Novel heating element (HE) types are developed and used for induction welding of thermoplastic composites. The HEs are fabricated using carbon nanofibers (CNFs) that are coated/decorated with metals, either silver or nickel by an electroless plating method. The realization of such HEs leads to the achievement of high quality welding with mechanical apparent lap shear strength values exceeding that obtained for the commonly-used stainless steel mesh susceptors.
      PubDate: 2017-06-07T08:00:14.307129-05:
      DOI: 10.1002/adem.201700294
  • Surface Engineered Nanoparticles: Considerations for Biomedical
    • Authors: Angie S Morris; Aliasger K Salem
      Abstract: The development of reproducible methods for the fabrication of nanoparticles in the 21st century is a major scientific achievement. Currently, there are many well-established methods for the production of nanoparticles of different shapes, sizes, and compositions. Along with these advancements in nanotechnology, nanoparticles have emerged as excellent tools for a diverse range of applications and have become a focus of research globally. With fundamental research being established, efforts are now being directed toward intelligently designed nanoparticles in which the properties of the nanomaterial are finely tuned depending on the application of interest. Usually, this involves the functionalization of the nanoparticle surface with a ligand. In this review, the impact of nanoparticle surface chemistry is discussed as it applies to biological systems.This review summarizes the current approaches for modifying nanoparticle surfaces and the impact on biological systems. Contained in this writing is a wide variety of examples where ligands (such as drugs, polymers, or proteins) are used to tailor the properties of nanoparticles for various biologically-related applications. These applications include targeted drug delivery, biomedical imaging, or the design of safer and more biocompatible nanomaterials.
      PubDate: 2017-06-07T08:00:10.740916-05:
      DOI: 10.1002/adem.201700302
  • Cantilever with High Aspect Ratio Nanopillars on Its Top Surface for
           Moisture Detection in Electronic Products
    • Authors: Nguyen Van Toan; Masaya Toda, Takumi Hokama, Takahito Ono
      Abstract: This work reports the patterning silicon pillars by metal-assisted chemical etching (MACE) process as a post process on a silicon cantilever for a moisture detection. Although the cantilever is very fragile, the patterning of the pillar structures on the cantilever has been successfully demonstrated. The cantilever coated with a material absorbing water (such as polyimide and mesoporous silica) can use as a humidity sensor. Its bending is due to the surface stress change from water molecule absorption. However, the bending of the cantilever is usually at a small value. Here, the silicon cantilever with high aspect ratio pillars on its surface is proposed, which is expected for a larger bending of the cantilever during the water molecule absorption. The moisture detection utilizes the principle that the pillars stack together based upon the condensation behavior of a water vapor on their surfaces.Patterning high aspect ratio nanopillars on the AFM silicon cantilever for the moisture sensing application by metal assisted chemical etching are investigated. The moisture detection utilizes the principle that the pillars stack together based upon the condensation behavior of a water vapor on its surface.
      PubDate: 2017-06-07T08:00:05.077364-05:
      DOI: 10.1002/adem.201700203
  • A Microvascular System for the Autonomous Regeneration of Large Scale
           Damage in Polymeric Coatings 
    • Authors: Ryan C. R. Gergely; Michael N. Rossol, Sharon Tsubaki, Jonathan Wang, Nancy R. Sottos, Scott R. White
      Abstract: Self-healing polymers are capable of self-repair either in response to the damage or through external stimuli, but are limited in their ability to autonomously control the volume of healing agents released, in the length scale of damage they address, and in their ability to respond to multiple damage events. Here, the authors report a novel design for healing agent storage and release for vascular coating systems that allows for complete regeneration of a coating with precise and autonomous control of coating thickness. A variety of healing agent formulations that cure under ambient sunlight are explored and their cure profiles and mechanical properties are reported. In the proposed vascular coating system, the stored healing agent remains stable within the network until large-scale damage (e.g., abrasion) completely removes the protective coating. A precise volume within the network is then released, and cures when exposed to simulated sunlight to reform the protective coating. This coating system facilitates consistent coating thickness and hardness for several cycles of coating removal and regeneration.A new microvascular coating system enables fully autonomous regeneration and control of coating thickness. In response to damage, a prescribed amount of healing agent is released through a pressure responsive surface valve to the damaged surface. Exposure to simulated sunlight cures the healing agent to reform the coating.
      PubDate: 2017-06-07T06:54:32.276753-05:
      DOI: 10.1002/adem.201700319
  • Toward Functionally Graded Polymer Foams Using Microfluidics
    • Authors: Jonas Elsing; Aggeliki Quell, Cosima Stubenrauch
      Abstract: Functionally graded polymer foams are of great interest for safety components or interfacial tissue engineering. However, most production methods lack control of the pore size. With the microfluidic technique we are able to introduce a defined pore size gradient in polymer foams using foamed emulsions and emulsions, respectively, as templates.Polymer foams with a defined gradient in pore size and density can be produced using microfluidics. For this purpose, the production parameters of the liquid templates, such as liquid flow rate or gas pressure are varied with time. The graded liquid template can then be polymerized.
      PubDate: 2017-06-07T04:55:31.7294-05:00
      DOI: 10.1002/adem.201700195
  • Soft Robotics: Review of Fluid-Driven Intrinsically Soft Devices;
           Manufacturing, Sensing, Control, and Applications in Human-Robot
    • Authors: Panagiotis Polygerinos; Nikolaus Correll, Stephen A. Morin, Bobak Mosadegh, Cagdas D. Onal, Kirstin Petersen, Matteo Cianchetti, Michael T. Tolley, Robert F. Shepherd
      Abstract: The emerging field of soft robotics makes use of many classes of materials including metals, low glass transition temperature (Tg) plastics, and high Tg elastomers. Dependent on the specific design, all of these materials may result in extrinsically soft robots. Organic elastomers, however, have elastic moduli ranging from tens of megapascals down to kilopascals; robots composed of such materials are intrinsically soft − they are always compliant independent of their shape. This class of soft machines has been used to reduce control complexity and manufacturing cost of robots, while enabling sophisticated and novel functionalities often in direct contact with humans. This review focuses on a particular type of intrinsically soft, elastomeric robot − those powered via fluidic pressurization.This manuscript presents a comprehensive review of the materials, design, and manufacturing of fluidically pressurized intrinsically soft robotics, and set a historical context for their development. The authors then discuss their applications for human interaction and speculate on future composition and use cases.
      PubDate: 2017-05-31T08:57:19.925404-05:
      DOI: 10.1002/adem.201700016
  • Investigations of Corrosion Resistance of Laser Separated Open Cell
    • Authors: Robert Baumann; Patrick Herwig, Andreas Wetzig, Eckhard Beyer
      Abstract: Open cell metal foam contributes promising solutions to the light weight design, battery applications, and renewable energy. Still, challenges are present concerning the cutting into a defined shape. Mechanical processes like milling and grinding create surface smearing on the foam, which leads to a loss of their open cell behavior. Laser remote cutting offers a promising solution in order to overcome those challenges. Their investigations consider that this technique has a high potential concerning cutting speed, which is increased by more than 500% compared to state of the art laser separation techniques. Nevertheless, quality improvements regarding spatter formation and fouling or corrosion resistance has to be investigated. This paper offers insight into the viability of remote laser cutting and how quality aspects can be improved.Remote laser cutting offers cut velocities up to 300 m min–1 for open cell metal foam. Note, that the open cell character is still present after machining. In their investigations, salt spray test and alternating climate changing are executed. The laser influences areas exhibit less corrosion behavior. Remote laser cutting shows the best way for sizing open cell metal foams.
      PubDate: 2017-05-30T13:52:23.651528-05:
      DOI: 10.1002/adem.201700107
  • Influence of Mesostructure on Mechanical Property of Laminated Ti–Al
    • Authors: Shaoyuan Lyu; Yanbo Sun, Lei Ren, Wenlong Xiao, Chaoli Ma
      Abstract: Laminated Ti–Al composite sheets with different mesostructures have been fabricated through hot pressing. The influence of mesostructure on mechanical properties of the composite is investigated. The results indicate that with the increase of sintering temperature, different mesostructures of composite are obtained, that is, laminated Ti/Ti–Al composite, laminated Ti3Al/TiAl composite, and monolithic Ti3Al/TiAl composite. The mechanical properties tests reveal that laminated Ti/Ti–Al composite exhibits better comprehensive mechanical properties, including flexural strength, fracture toughness, and microhardness, than those of laminated Ti3Al/TiAl composite and monolithic Ti3Al/TiAl composite. The fracture analysis shows that the propagation route of crack is zigzag for Ti/Ti–Al composite, curving for laminated Ti3Al/TiAl composite, and approximately a straight line for monolithic Ti3Al/TiAl composite. The relevant strengthening and toughening mechanism of the composites is discussed.Incorporating one ductile layer into the brittle Ti–Al composite is a potential way to overcome low ductility and fracture toughness at room temperature. By controlling the mesostructures of the composite, three types of composites are obtained, among which, laminated Ti/Ti–Al composite exhibits better comprehensive mechanical properties than those of laminated Ti–Al composite and monolithic Ti–Al composite.
      PubDate: 2017-05-29T04:31:28.19734-05:0
      DOI: 10.1002/adem.201700070
  • Manufacturing and Characterization of Highly Porous Bioactive Glass
           Composite Scaffolds Using Unidirectional Freeze Casting 
    • Authors: Laura M. Henning; Sara Zavareh, Paul H. Kamm, Miriam Höner, Horst Fischer, John Banhart, Franziska Schmidt, Aleksander Gurlo
      Abstract: The aim of this work is the fabrication of bioactive and degradable scaffolds for bone tissue engineering. Freeze casting is used to obtain macropores. Alongside, highly bioactive 45S5 Bioglass, gelatin and chitosan are used as biocompatible binder and stabilizing agent, respectively. By varying the cooling rate between 2 and 4 K min−1 and whether the slurry is allowed to form a gelled network at 7 °C before freeze casting or not, samples with a porosity of 75% are achieved. X-ray tomography analysis shows smallest pore sizes between 73 and 77 µm and a rather lamellar structure parallel to the freezing direction for the non-gelled samples, whereas the gelled samples have smallest pores between 96 and 120 µm and show a rather cellular structure. Compression tests reveal compressive strengths from 2 (non-gelled) to 3 MPa (gelled), while the quasielastic moduli of the gelled samples (44–46 MPa) clearly exceed values of the non-gelled (20–23 MPa). Thus, it is concluded that the modified pore structure caused by the gelling process markedly improves the mechanical properties of the samples. After seven days in SBF under physiological conditions, a calcium phosphate rich layer is detected on the samples surface, revealing the bioactivity of the scaffolds.The combination of gel casting and freeze casting results in better mechanical properties compared to the sole use of the conventional freeze casting technique. Highly porous 45S5 Bioglass/gelatin/chitosan composite scaffolds, which are gel casted before freeze casting, show an increase in the quasielastic moduli by 100% and potentially sufficient pore sizes for applications in bone tissue engineering.
      PubDate: 2017-05-29T04:31:14.910719-05:
      DOI: 10.1002/adem.201700129
  • Identifying the Stages during Ultrasonic Processing that Reduce the Grain
           Size of Aluminum with Added Al3Ti1B Master Alloy 
    • Authors: Gui Wang; Matthew S. Dargusch, Dmitry G. Eskin, David H. StJohn
      Abstract: The combined application of UST and Al3Ti1B grain refiner changes the macrostructure of untreated commercial purity aluminum from large millimeter sized columnar grains to equiaxed grains of a few hundred microns. This research reveals three distinct stages that affect the grain size, while UST is applied during melting and solidification. Stage I applied well above the liquidus temperature improves the efficiency of the refiner, possibly by de-agglomeration and wetting of TiB2 particles, and their distribution throughout the melt by acoustic streaming. Stage I is followed by Stage II, where little further improvement occurs. Stage III causes additional grain refinement when applied at and below the liquidus temperature, where nucleation of grains maybe enhanced by cavitation, which can also facilitate fragmentation and detachment of grains formed on the sonotrode. Convection due to acoustic streaming creates a uniformly undercooled temperature in the melt, which ensures the survival of these new grains during transport, as well as assisting the transport of grains to produce a uniform fine grain size throughout the ingot.Termination of ultrasonic treatment of Al with Al3Ti1B master alloy addition at a range of temperatures reveals three stages affecting grain refinement. The grain density is increased by five to ten times during stages I and III, which are above and below the liquidus temperature, respectively. The grain size decreased from 278 to 115 microns after 110 s of treatment.
      PubDate: 2017-05-29T04:30:59.036537-05:
      DOI: 10.1002/adem.201700264
  • Effects of Phase Content and Evolution on the Mechanical Properties of
           Mg95Y2.5Zn2.5 and Mg93.1Y2.5Zn2.5Ti1.6Zr0.3 Alloys Containing LPSO and W
    • Authors: Shouzhong Wu; Zhe Zhang, Jinshan Zhang, Chunxiang Xu, Xiaofeng Niu, Wei Liu
      Abstract: The effects of phase content and evolution on mechanical properties of the alloys are investigated by extruding Mg95Y2.5Zn2.5 and Mg93.1Y2.5Zn2.5Ti1.6Zr0.3 alloys with different original microstructures. The 18R-LPSO phase plays a decisive role in the strength of as-extruded alloys. The spherical W-MgYZn2 phase enhances the deformability and ductility of the alloys. The dynamic recrystallization grains can be observed in all as-extruded alloys. However, the 14H-LPSO clusters and dynamic precipitates only form in the as-cast and T41-treated (solid-solution treatment at 530 °C for 3 h with water cooling) alloys after extrusion. Based on synergistic effects of these phases mentioned above, the T41-treated Mg93.1Y2.5Zn2.5Ti1.6Zr0.3 alloy exhibits good compressive mechanical properties after extrusion.The solid-solution treated Mg93.1Y2.5Zn2.5Ti1.6Zr0.3 alloy exhibits good comprehensive mechanical properties after extrusion, which can be attributed to the synergistic effects of these phases, including 18R-LPSO phase, spherical W-MgYZn2 phase, DRX grains, 14H-LPSO clusters, and dynamic precipitates.
      PubDate: 2017-05-26T00:46:22.974917-05:
      DOI: 10.1002/adem.201700185
  • Effect of Crucible Material for Ingot Casting on Detrimental Non-Metallic
           Inclusions and the Resulting Mechanical Properties of 18CrNiMo7-6 Steel 
    • Authors: Sebastian Henschel; Johannes Gleinig, Tim Lippmann, Steffen Dudczig, Christos G. Aneziris, Horst Biermann, Lutz Krüger, Anja Weidner
      Abstract: The steel 18CrNiMo7-6 (AISI 4317) is treated in three different crucibles based on carbon-bonded alumina. Non-metallic inclusions in the steel are characterized by means of optical microscopy and scanning electron microscopy. Strength, ductility, and dynamic fracture toughness of the steel are evaluated at different temperatures. Furthermore, fatigue lifetimes in the very high cycle regime are determined. The treatment in a carbon-bonded alumina (A–C) crucible resulted in a relatively high inclusion content involving a high number of duplex inclusions consisting of MnS and Si–Al–O. In contrast, less but large pure MnS inclusions are observed when the steel is treated in carbon-bonded alumina-zirconia-titania crucibles – with or without a coating of carbon nanotubes (AZT–C–n and AZT–C). The steel treated in the A–C crucible exhibits the highest strength and fatigue lifetime, but the lowest energy dissipation. The relatively low inclusion content in the AZT–C treated steel results in high energy dissipation during tensile deformation. However, large MnS inclusions in the AZT–C and AZT–C–n treated steels act as crack initiation sites and reduce the fatigue lifetime. The dynamic fracture toughness is not affected by the different melt treatments. This result is explained by cell-like structures within the material that are characterized by a lower strength and an increased concentration of MnS inclusions.The effect of crucible material on the distribution of non-metallic inclusions in 18CrNiMo7-6 steel (AISI 4317) is studied. The resulting quasi-static strength and ductility, the dynamic fracture toughness, and the fatigue life time are evaluated. The treatment in a carbon-bonded alumina crucible results in lowest ductility due to a relatively high inclusion content. However, the highest fatigue strength is observed for this treatment.
      PubDate: 2017-05-24T08:55:39.10871-05:0
      DOI: 10.1002/adem.201700199
  • A Combinatorial Approach for Assessing the Magnetic Properties of High
           Entropy Alloys: Role of Cr in AlCoxCr1–xFeNi 
    • Authors: Tushar Borkar; Varun Chaudhary, Bharat Gwalani, Deep Choudhuri, Calvin V. Mikler, Vishal Soni, Talukder Alam, Raju V. Ramanujan, Rajarshi Banerjee
      Abstract: A combinatorial assessment of composition-microstructure-magnetic property relationships in magnetic high entropy AlCoxCr1-xFeNi alloy (0 ≤ x ≤ 1) system has been carried out using compositionally graded alloys fabricated via laser additive manufacturing. At one end, the AlCoFeNi composition (x = 1) consisted of equiaxed B2 grains, exhibiting very early stages of phase separation (only compositional partitioning) into Ni–Al rich and Fe–Co rich regions within grains of the B2 phase. At the other extreme, the AlCrFeNi composition (x = 0) exhibited grains with pronounced spinodal decomposition, resulting in a B2 + bcc microstructure with the degree of spinodal decomposition progressively increasing with Cr content in these AlCoxCr1–xFeNi alloys. While the saturation magnetization (Ms) monotonically increases six times from x = 0 to x = 1, the coercivity (Hc) variation is non-monotonic, increasing seven times from x = 0 to x = 0.4, and subsequently decreasing fourteen times from x = 0.4 to x = 1.0. The magnetic phase transition temperature (Tc) for these alloys also increases monotonically with increasing Co content with a second phase transition exhibited in a certain range of compositions between x = 0.6 to x = 0.8. Such substantial changes in the magnetization behavior and properties of magnetic high entropy systems opens possibilities of tuning these alloys for specific soft or hard magnetic component applications.Laser Engineered Net Shaping (LENS™) process is used for making a compositionally graded magnetic AlCoxCr1–xFeNi HEA (0 ≤ x ≤1). The size scale of phase separation wave, which is affected by the composition, critically affects the magnetic properties like saturation magnetization and coercivity.
      PubDate: 2017-05-24T06:05:39.449627-05:
      DOI: 10.1002/adem.201700048
  • Activation Energy and High Temperature Oxidation Behavior of
           Multi-Principal Element Alloy
    • Authors: Harpreet Singh Grewal; Ramachandran Murali Sanjiv, Harpreet Singh Arora, Ram Kumar, Aditya Ayyagari, Sundeep Mukherjee, Harpreet Singh
      Abstract: Activation energy and diffusion kinetics are important in modulating the high temperature oxidation behavior of metals. Recently developed multi-principal element alloys, also called high entropy alloys (HEAs), are promising candidate material for high temperature applications. However, the activation energies and diffusion kinetics of HEAs have been limitedly explored. We investigate the diffusional activation energy for oxidation of Al0.1CoCrFeNi HEA. Compared to conventional steels and Ni-based super alloys, the HEA showed a significantly higher diffusion activation energy. This behavior is explained based on low potential energy of the lattice and interstitial sites which effectively trap the atoms, limiting their diffusion. The atomic mean jump frequency for interstitial diffusion of oxygen in the HEA is four-orders of magnitude lower than T22 and T91 steels and seven-orders of magnitude lower compared to pure iron. Al0.1CoCrFeNi HEA showed the lowest oxidation rate compared to conventionally used steels, super-alloys, and coatings.Al0.1CoCrFeNi high entropy alloy shows significantly high activation energy and oxidation resistance. High activation energy lowers the mean jump rate of oxygen atom resulting in sluggish diffusion.
      PubDate: 2017-05-24T06:05:31.354021-05:
      DOI: 10.1002/adem.201700182
  • 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
    • 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
  • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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 obtained from electron backscatter diffraction (HR-EBSD) and surmises that the rotation field rather than rotation gradient field was used during geometrical necessary dislocations (GND) calculation process. It is our opinion, however, that the topic of the absolute values of the stresses based on cross correlation and the HR-EBSD technique is not discussed at all in our paper. Our paper is focused rather on relative values (the evolution of stress/strain partitioning at different tensile 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. We have checked the GND calculation code carefully and we 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
    • 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
  • Effect of Meso-Scale Geometry on Piezoelectric Performances of Additively
           Manufactured Flexible Polymer-Pb(ZrxTi1−x)O3 Composites 
    • Authors: Yan-Zhou Ji; Zhuo Wang, Bo Wang, Yong Chen, Tu Zhang, Long-Qing Chen, Xuan Song, Lei Chen
      Abstract: By integrating phase-field model and finite element calculations, we demonstrate that the additively manufactured 3-3 polymer-Pb(ZrxTi1-x)O3 composite can attain superb d33 and significantly outperform its 0–3, 1–3, and 2–2 counterparts in terms of hydrostatic figure of merit (HFOM), showing great potential in underwater acoustic applications.
      PubDate: 2017-04-04T09:35:29.803928-05:
      DOI: 10.1002/adem.201600803
  • Polymer Derived Ceramics with β-Eucryptite Fillers: Filler-Matrix
    • Authors: Anna Fedorova; Ulf Betke, Michael Scheffler
      Abstract: Polymer derived ceramics with ß-eucryptite are manufactured and filler-matrix interactions in the temperature range between 800 and 1 100 °C are investigated. Pyrolysis temperatures above 1 000 °C led to changes of the β-eucryptite phase, due to a significant SiO2 amount in the polymer derived ceramic matrix. A new phase, β-spodumene, is formed; this is, confirmed by calculations of the lattice parameters. Scanning electron microscopy and energy dispersive x-ray spectroscopy of the microstructure allow to localize spots on the matrix-filler interface, where the described processes appear.The phase composition and microstructure of Si–O–C/β-eucryptite composites exhibiting a zero-expansion behavior is evaluated using p-XRD and SEM-EDX. The β-eucryptite filler consumes silica from the Si–O–C matrix above 1 000 °C and finally transforms into a new β-spodumene phase.
      PubDate: 2017-03-24T05:15:21.914742-05:
      DOI: 10.1002/adem.201700079
  • Microstructural Investigation of the Formation and Development of
           Topologically Close-Packed Phases in a 3rd Generation Nickel-Base Single
           Crystal Superalloy 
    • Authors: KeeHyun Kim; Paul A. Withey
      Abstract: Topologically close-packed (TCP) phases generally form during long period aging or in-service. In this study, however, the early stage formation and development of TCP phases, which has received relatively less attention, was extensively investigated from as-cast samples through to fully heat-treated ones. TCP phases were surrounded with a γ′ phase, and their compositions were slightly different due to the structural and compositional complexity. Most of all, extremely fine particles of about 100 nm containing large amounts of rhenium formed in the early processing. In addition, two different types of particles were detected at different formation stages: round-shaped particles at the starting point, and needle-like ones near the terminating point. Based on experimental observations, it was suggested that the needle-like particle probably showed the growth of a TCP phase by the diffusion of rhenium after nucleation from a point containing high amounts of rhenium.The University of Birmingham and Rolls-Royce plc investigate the early stage nucleation and development of the harmful TCP phases. Extremely fine particles (about 100 nm across) containing large amounts of rhenium formed in manufacturing stages for turbine components, that is, during casting, and heat treatment.
      PubDate: 2017-03-20T02:55:48.327475-05:
      DOI: 10.1002/adem.201700041
  • Enhanced Ductility of a Bimodal Grain Structure Ti–22Al–25Nb Alloy
           Fabricated by Spark Plasma Sintering 
    • Authors: Kyong-Ho Sim; Guofeng Wang, Yong-Min Li, Ju-Yong Jong
      Abstract: A bimodal grain structure Ti–22Al–25Nb alloy with enhanced ductility is fabricated from the blended powder mixture of argon gas atomized powder and mechanically alloyed powder by spark plasma sintering. The microstructure of the bimodal grain structure Ti–22Al–25Nb alloy and the effects of the argon gas atomized powder mass fraction on the compression properties are investigated. This alloy shows the bimodal microstructure, which the coarse grain regions are surrounded by the ultrafine grained matrix. Compared with the Ti–22Al–25Nb alloy sintered from 100% mechanically alloyed powder, this alloy sintered from the blended powder mixture containing 20% argon gas atomized powder exhibits the fracture elongation to improve 20.5%.A bimodal grain structure Ti–22Al–25Nb alloy with enhanced ductility is fabricated from the blended powder of argon gas atomized powder and mechanically alloyed powder by spark plasma sintering. When the mass fraction of the argon gas atomized powder is controlled well, the enhanced ductility is obtained without sacrificing much of the yield strength.
      PubDate: 2017-03-16T06:51:10.67336-05:0
      DOI: 10.1002/adem.201600804
  • On the Microstructure Homogeneity of AA6061 Alloy After Cross-Shear
    • Authors: Young Gun Ko; Kotiba Hamad
      Abstract: This work is presented to investigate the homogeneity of microstructures evolved after cross-shear deformations imposed by a differential speed rolling (DSR) process. For this purpose, transmission electron microscopy (TEM) microstructures and through-thickness hardness maps of AA6061 aluminum alloy samples deformed by the DSR process are investigated. The results reveal the evolution of ultrafine grained structures (≈0.3 µm) after DSR deformation. Additionally, it is found that the through-thickness homogeneity is clearly improved as the number of the cross-shear increases.This work is presented to study the effects of cross-shear deformations introduced by differential speed rolling process on microstructure and its homogeneity in AA6061 aluminum alloys.
      PubDate: 2017-03-16T02:41:09.29599-05:0
      DOI: 10.1002/adem.201700152
  • A Cycle-Etching Approach Toward the Fabrication of Superamphiphobic
           Stainless Steel Surfaces With Excellent Anticorrosion Properties 
    • Authors: Ni Wen; Shan Peng, Xiaojun Yang, Mengying Long, Wanshun Deng, Gongyun Chen, Jiaqi Chen, Wenli Deng
      Abstract: In this paper, a facile approach is developed for preparing superamphiphobic surfaces with excellent anticorrosion properties on 304 stainless steel (SS) substrates. This proposed methodology involves fabrication of micro/nano-scale binary structures on SS substrates by a cycle-etching approach (cycles of hydrofluoric acid etching and ultrasonic cleaning), and final fluoroalkylsilane modification. Wettability measurements reveal that the fabricated SS surfaces become super-repellent toward water and peanut oil. By varying the times of cycle-etching, the authors compare the relationship between morphological change and wettability. The potentiodynamic polarization curves and electrochemical impedance spectroscopy suggest that the fabricated SS surfaces have superior corrosion resistance.A cycle-etching approach is developed to fabricate the superamphiphobic stainless steel surfaces. The resulted stainless steel surfaces hold micro/nano binary structure even after ultrasonic cleaning, which become super-repellent toward water (72 mN m–1) and peanut oil (34 mN m–1), and show static water contact angles of 159° and peanut oil contact angles of 153°, respectively.
      PubDate: 2017-03-16T02:41:05.618027-05:
      DOI: 10.1002/adem.201600879
  • Ti/Ti3SiC2(/TiC) Bulk and Foam Composites by Pyrolysis of Polycarbosilane
           and TiH2 Mixtures 
    • Authors: Esther Molero; Begoña Ferrari, Antonio Javier Sanchez-Herencia, Elena Gordo, Paolo Colombo
      Abstract: A preceramic polymer, is mixed with TiH2 particles in different amounts and a MAX phase (Ti3SiC2) are produced by heating in inert atmosphere. Composites produced by mixing the reactive mixture with an excess of TiH2 powder, lead to Ti/Ti3SiC2/TiC bulk composites possessing greatly increased wear resistance and increased hardness in comparison to pure Ti. An emulsion-based colloidal processing and foaming technique is implemented together to produce cellular Ti composite foams containing TiC and Ti3SiC2 ceramic phases. The addition of methylcellulose enabled to suitably control the viscosity of the aqueous TiH2 slurry and to produce stable foams with homogeneous morphology.Colloidal processing and emulsion foaming have been implemented to fabricate cellular porous materials based on Ti reinforced with a MAX phase (Ti3SiC2). The foams are manufactured from stable aqueous suspensions of TiH2, with alkane phase in which a ceramic precursor (PSC) are dissolved. Obtained composites double hardness and improve wear resistance of Ti structures.
      PubDate: 2017-03-13T02:00:51.589469-05:
      DOI: 10.1002/adem.201600700
  • Investigations on Mechanical and Tribological Behavior of dcMS/HPPMS CrN
           and (Cr,Al)N Hard Coatings Using Nanoscratch Technique 
    • Authors: Kirsten Bobzin; Tobias Brögelmann, Nathan C. Kruppe, Mostafa Arghavani
      Abstract: In this paper, interfacial adhesion strength and tribological behavior of systems, consisting of CrN and (Cr,Al)N coatings and AISI 420 steel substrate are investigated. The coatings are deposited using a hybrid technology consisting of direct current and high power pulse magnetron sputtering dcMS/HPPMS. Conventional Rockwell and scratch tests as well as nanoscratch analyses are performed. For the nanoscratch tests, a Berkovich and a conical indenters are used. Damage mechanisms are analyzed using Scanning Electron Microscopy (SEM) and explained by the plastic work from the nanoindentation tests. Investigations show a stronger interfacial adhesion strength and a higher abrasion resistance of the system AISI 420/(Cr,Al)N compared to the AISI 420/CrN.Mechanical and tribological behavior of two compounds consisted of hard coatings CrN and (Cr,Al)N and AISI 420 substrate are investigated using nanoscratch analyses. Nanoscratch tests are performed using Berkovich and conical indenters. A stronger interfacial adhesion strength and higher abrasion resistance of compound can be achieved in case of compound AISI 420/(Cr,Al)N compared to AISI 420/CrN.
      PubDate: 2017-03-10T10:53:44.472551-05:
      DOI: 10.1002/adem.201600632
  • Microstructures and Properties of the Copper-Coated SiCp Reinforced
           Al–Si Alloy Composites 
    • Authors: Yan Feng; Jun Peng Ren, Cui Ge Dong, Chaoqun Peng, Richu Wang
      Abstract: Copper-coated silicon carbide (SiC) particles have been developed to improve the strength and wear resistance of Al–Si matrix composites, which are utilized in brake pads and, hence find applications in aerospace and automobile industries. Copper-coated SiC powder is prepared by electroless plating and is characterized by scanning electron microscopy and X-ray diffraction. Copper-coated SiCp reinforced Al–Si composites are prepared by a powder metallurgy method, and their microstructures and properties are compared with those of Al–Si and Al–Si–Cu matrix composites reinforced with SiCp without copper coating. Our results show that the copper-coated SiCp-reinforced Al–Si composite exhibits advantageous mechanical properties and better frictional wear resistance.High-density SiCp/Al–Si composites with good mechanical properties and wear resistance are fabricated by low-temperature hot-press sintering by using Cu-coated silicon carbide (SiC) particles. The copper coating changes the sintering system from SiC–Al to Cu–Al, since copper and aluminum can diffuse into each other at relatively low temperature to form a continual liquid film. Hence, defects such as flaws and holes in the matrix and at the interfaces can be filled, which favors the low-temperature densification of SiCp/Al–Si composites.
      PubDate: 2017-03-10T10:52:27.437853-05:
      DOI: 10.1002/adem.201600816
  • A Single-Chamber System of Initiated Chemical Vapor Deposition and Atomic
    • Authors: Bong Jun Kim; Hongkeun Park, Hyejeong Seong, Min Seok Lee, Byoung-Hwa Kwon, Do Heung Kim, Young Il Lee, Hyunkoo Lee, Jeong-Ik Lee, Sung Gap Im
      Abstract: A single-chamber system capable of depositing both organic and inorganic layers by initiated chemical vapor deposition (iCVD) and atomic layer deposition (ALD) is demonstrated to facilitate the fabrication of organic/inorganic hybrid thin film encapsulation (TFE). The chamber geometry and the process conditions of iCVD and ALD are similar to each other, which enabled the design of the single-chamber system. Both organic and inorganic films deposited via the single-chamber system produces films with their properties equivalent to those deposited in separate iCVD and ALD reactors. Alternating the deposition mode between iCVD and ALD produces organic/inorganic multilayers with outstanding barrier properties as well as optical transparency mechanical flexibility.A single-chamber system that can conduct both initiated chemical vapor deposition (iCVD) and atomic layer deposition (ALD) is demonstrated in this study. From the single-chamber system, thin film encapsulation (TFE) composed of alternating organic and inorganic layers is fabricated. The TFE exhibited outstanding properties suitable for encapsulation of organic light-emitting diodes.
      PubDate: 2017-03-10T10:52:23.821327-05:
      DOI: 10.1002/adem.201600819
  • Lead-Free Ceramics with High Energy Density and Reduced Losses for High
           Temperature Applications 
    • Authors: Tatiana Correia; Mark Stewart, Angela Ellmore, Knuth Albertsen
      Abstract: The major limiting factors for the use of ceramic capacitors in power electronics are size and temperature stability. Ferroelectric ceramics very often exhibit high energy density, but fail to provide stable and efficient performance at high temperatures. Here, the authors report on a lead-free BiFeO3-SrTiO3 ceramic capacitor exhibiting unprecedented low dielectric loss and high thermal stability, while maintaining high energy density and fast discharge rates up to 200 °C. These unique properties clearly outperform other state of the art ceramics and potentially create significant new markets for high capacity ceramic capacitors at high frequencies and high temperature operations.The major limiting factors for the use of ceramic capacitors in power electronics are size and temperature stability. Here, the authors report on a new lead-free BiFeO3–SrTiO3 multilayer ceramic capacitor, exhibiting unprecedented low dielectric loss, and high thermal stability while maintaining high energy density up to 200 °C, with the potential to create significant new markets for high capacity ceramic capacitors.
      PubDate: 2017-03-03T14:10:33.318407-05:
      DOI: 10.1002/adem.201700019
  • Uncovering Nature's Design Strategies through Parametric Modeling,
           Multi-Material 3D Printing, and Mechanical Testing 
    • Authors: Simon Frølich; James C. Weaver, Mason N. Dean, Henrik Birkedal
      Abstract: Nature produces a multitude of composite materials with intricate architectures that in many instances far exceed the performance of their modern engineering analogs. Despite significant investigations into structure-function relationships of complex biological materials, there is typically a lack of critical information regarding the specific functional roles of many of their components. To help resolve this issue, the authors present here a framework for investigating biological design principles that combines parametric modeling, multi-material 3D printing, and direct mechanical testing to efficiently examine very large parameter spaces of biological design. Using the brick and mortar-like architecture of mollusk nacre as a model system, the authors show that this approach can be used to effectively examine the structural complexity of biological materials and harvest design principles not previously accessible.A workflow for efficiently screening material design space based on parametric modeling, multi-material 3D printing and mechanical testing is presented (figure). It is used to explore bio-similar and hypothetical nacres to evaluate the impact of diverse structural features on materials performance.
      PubDate: 2017-03-02T08:30:29.942129-05:
      DOI: 10.1002/adem.201600848
  • Powder Metallurgy Strategies to Improve Properties and Processing of
           Titanium Alloys: A Review
    • Authors: Alexandra Amherd Hidalgo; Robert Frykholm, Thomas Ebel, Florian Pyczak
      Abstract: Powder metallurgy (PM) is an attractive technology for manufacturing net-shape titanium-based components. However, it is challenging to make PM titanium products competitive in terms of mechanical properties. This article gives an overview of the current challenges in PM titanium and the best strategies to overcome them by alloying. By adding suitable alloying elements the properties of PM titanium components can be enhanced. The use of sintering aids helps to control the typical residual porosity of PM titanium alloys. Furthermore, controlling microstructure by alloying offers the possibility to go for high performance applications. Moreover, ductility is improved by adding elements that scavenge oxygen. A favorable selection of alloying elements offers a practical and competitive approach to meet the mechanical requirements in future PM titanium applications.Powder metallurgy (PM) of titanium-based materials is of increasing interest as an economic net-shape production technique. However, industrial applications are still very limited. This review studies the current challenges in PM titanium and offers diverse strategies to overcome them by alloying.
      PubDate: 2017-02-28T02:45:33.548623-05:
      DOI: 10.1002/adem.201600743
  • The Effect of Pressure Stress on the Evolution of B2(ω) Phase in High Nb
           Containing TiAl Alloy 
    • Authors: Bei Cao; Jieren Yang, Xuyang Wang, Rui Hu
      Abstract: The thermal stability of the B2(ω) phase in high Nb containing TiAl alloy has attracted intense attention in recent years. This study focuses on the phase transformation between B2 and ω phases under the influence of thermal pressure stress in the Ti–45Al–8.5Nb–(W, B, Y) alloy. A large number of ω phases with the volume fraction of 42.3% exist within the B2 region in as-cast alloys. The as-cast samples were subjected to thermo-compressive loading at 850 and 900 °C under the stresses of 300 and 500 MPa. Results show that the transformation of B2  ω occurs at 850 °C, which can be promoted under a pressure stress. Further, the ω particles dissolved into the B2 matrix at 900 °C, and this transformation is suppressed by the role of thermal pressure. The mechanisms of the phase transformations mentioned above were discussed.The B2 phase is unstable at 850 °C and transfers to ω phase in high Nb–TiAl alloy, which can be promoted by press pressure. The ω fraction further increases to 65.2% under 500 MPa after 1 h. Also, pressure can suppress the transition of ω  B2 at 900 °C. The ω phase remains in B2 area as 34.1 vol% content under 300 MPa after 1 h.
      PubDate: 2017-02-20T02:10:35.984997-05:
      DOI: 10.1002/adem.201600844
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
Home (Search)
Subjects A-Z
Publishers A-Z
Your IP address:
About JournalTOCs
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016