关键词： Scandium alloys  

摘要： In this study, binary interdiffusivities of bcc titanium-scandium (Ti-Sc) alloys in the temperature range of 1273 K to 1473 K were determined by combining the diffusion couple technique and Boltzmann-Matano method. In addition, the composition-dependent Young's modulus and hardness of bcc Ti-Sc alloys were obtained using the nanoindentation technique. The results reveal that a small amount of Sc additive can be very beneficial to bio-Ti alloys with good properties. (C) The Minerals, Metals & Materials Society and ASM International 2019

关键词： defect   kaolinite   mechanical properties   molecular dynamics   temperature effect  

摘要： Molecular dynamics simulations of different defective kaolinites under tension were performed to reveal the effects of defect location, type, density and temperature on their mechanical properties. Four types of defective kaolinite with Si vacancies were constructed. Based on the atomic-scale deformation and failure processes of defective kaolinite and its stress-strain curves, the Young's moduli and tensile strengths in three crystal directions were obtained and compared with the existing theoretical values from the literature. The defect location at each layer does not affect the mechanical properties of kaolinite and the cracks initiated at the defective sites. The atom density of each model was calculated in order to investigate the defect-type effect on the mechanical properties of kaolinite. The simulation results also showed that kaolinite exhibits brittle failure behaviour and the mechanical properties degrade significantly with increasing defect density and temperature. The influence of temperature on the mechanical properties of defective kaolinite is discussed in detail.

关键词： Polychloroprene   Strain-induced crystallization   X-ray  

摘要： It is shown in the present paper how the addition of a moderate amount of carbon black filler to a poly-chloroprene gum modifies the local strain state and alters the ability of the polymer to strain-crystallize. The study combines mechanical and X-ray diffraction performed during classical mechanical cycling and tensile impact tests. It highlights the fact that the strain modification induced by the filler addition is highly inhomogeneous: the crystallization behavior and the local draw ratio state are affected differently. The partial relaxation of the amorphous fraction by the strain-induced crystallization evidenced in the pure gum is still present and should play a protective role. The effect of temperature on the crystallization correlates with the evolution of stress-strain curves. In particular the role of crystallization in stress-hardening is apparently amplified by the presence of the filler. Preliminary tensile tests reveal a drastic decrease of the induction time necessary for crystallization to develop. This implies a strain amplification effect higher than predicted from mechanical cycling analysis. It is proposed that carbon black particles have no time to relax during the fast stretching period. All these observations point to a synergistic effect between filler addition and strain-induced crystallization.

关键词： Drug release   Anatomy   Monomers   Therapeutics   Organic compounds  

摘要： To transform biologically inert poly(methyl methacrylate) (PMMA) bone cement into a tunable drug eluting biomaterial, we have employed polymerizable therapeutic methacrylic (TMA) comonomers that use the methacrylic carbonyl bond as a platform for hydrolytically controlled drug release. Changing the identity of the tether bond allows us to select release patterns ranging from rapid release (up to 6.5 times more efficient than drug-eluting cements based on passive diffusion) to long-term anchorage. Further, TMA cements retain their mechanical strength throughout drug release, outperforming both PMMA and diffusion-based cements in compressive strength after aging. We also found that certain factors exert secondary effects on the patterns of covalently controlled release from TMA cements, including TMA/methyl methacrylate (MMA) copolymer architecture (created by different reactivity ratios between each TMA/MMA pairing) and cement hydrophilicity. TMA comonomers represent a valuable tool for tuning the bioactivity and cure behavior of bone cement to meet a range of demands in the operating room.

关键词： FeNiCr austenitic stainless steels   chromium and nickel contents   thermal and mechanical properties   molecular dynamics   high pressure and temperature  

摘要： The effect of Cr and Ni content on thermo-mechanical properties of FeNiCr austenitic stainless steel under ambient and high pressure and temperature were investigated by MD simulations. The FCC structure was selected as optimum structure for FeNiCr system based on obtained MD results from Bonny EAM potential and valid experimental results. The structural and mechanical properties of pure Fe, Ni, and Cr were also estimated based on this potential, indicating good agreement with experimental results. These properties were computed for four experimental case studies which showed less than 10% error. Moreover, the elastic constants of the Fe-(8-18)Ni-(18-25)Cr systems were estimated. Results showed that bulk modulus increases by increasing the Ni and Cr contents, which can be connected to the changes in bonding electrons. The thermal properties of FeNiCr were calculated in ambient and high pressure. Although thermo-mechanical properties confirm good agreement with experimental results at the ambient condition, however, they indicate that FeNiCr Bonny potential is not applicable at high pressure. In order to tackle this issue, a hybrid potential was used at high Pressure/Temperature. The results illustrate enhanced mechanical properties, increase of melting point and reduction of LTE in high pressure and deteriorated mechanical properties at high temperature.

关键词： Amorphous alloy   Metallic glasses   Kinetics   Elasticity   Mechanical properties  

摘要： Most bulk metallic glass systems with high glass-forming ability are doped with precious metal(s) or toxic element(s), like palladium and beryllium, leading to relatively high cost or low safety in use. In this work, the glass-forming ability, crystallization kinetics and mechanical properties of the Zr55Co25Al20 and Zr52Co25Al23 bulk metallic glasses prepared by water-cooled copper mold suction casting are investigated in detail. The results show that Zr52Co25Al23 has a wider supercooled liquid region, a higher thermal stability and a higher glass-forming ability than the Zr55Co25Al20 amorphous alloy. At the same time, Zr52Co25Al23 has a higher activation energy of crystallization than Zr55Co25Al20 amorphous alloy, indicating that Zr52Co25Al23 has a higher resistance to crystallization than Zr55Co25Al20. Investigation of the mechanical properties reveals that Zr52Co25Al23 also has a higher fracture strength of up to 2308 MPa and a higher specific fracture strength of up to 3.78 x 10(5) N m kg(-1) compared with 316L stainless steel, Ti-6Al-4V, as well as Mg-, Ti-, and other Zr-based BMGs. (C) 2019 Elsevier B.V. All rights reserved.

关键词： H-bond network   Interlayer water dynamics   Aluminosilicate skeleton   Inhomogeneous calcium dynamics   Hydrolytic reaction pathway  

摘要： In order to gain a molecular-level insight on the structure and performance of cement-based materials in high temperature environment, this paper investigates the structure, dynamics and mechanical properties of their main hydration product, calcium aluminosilicate hydrate (C-A-S-H), at elevated temperatures by using reactive molecular dynamics simulation. The results show that rising temperature can destroy the H-bond network of interlayer water molecules in C-A-S-H, leading to pronounced expansion of the interlayer regions. Meanwhile, interlayer water molecules lose its glassy water dynamics and exhibit dramatically high diffusivity with rising temperature. In addition, the calcium atoms show inhomogeneous dynamics at high temperature. At 1500K, the interlayer calcium atoms can escape from their coordination "cages" and diffuse, while the motion of those located in the principal layer are restricted by the Si-O and Al-O bonds throughout the simulation. Furthermore, reactive force field couples the mechanical response and chemical reaction during the uniaxial tensile test for C-A-S-H gel. The de-polymerization and hydrolytic reaction happens frequently in the deformed C-A-S-H gel at high temperature, resulting in degradation of stiffness and strength. On the other hand, the atomic rearrangement at elevated temperature contributes to the re-connection of broken chemical bonds, enhancing ductility of C-A-S-H.

关键词： strain rate   Bone Fracture   Molecular Dynamics Simulation   Computer Programming Languages   ZIGZAG   armchairs   Elastic Modulus   impact factor   Mechanical properties   Fracture strength   STRAIN AT BREAK   kinetic simulation   Molybdenum   cracks   Support Vector Network  

摘要： Despite the spurring interests in two-dimensional transition metal dichalcogenide (TMDC) materials, knowledge on the mechanical properties of one of their important member, i. e., molybdenum diselenide (MoSe2) is scarce and remains an open topic. In this work, the mechanical properties of h-MoSe2 and t-MoSe2 were systematically investigated using classical molecular dynamics (MD) simulations combined with machine learning (ML) techniques. The effects of chirality, temperature and strain rate on fracture strain, fracture strength and Young's modulus were characterized in both armchair and zigzag directions. For h-MoSe2, the fracture strengths were 13.6 and 13.0 GPa for armchair and zigzag chiralities, respectively, at 1 K and strain rate of 5 x 10(-4) ps(-1);the corresponding fracture strains were 0.23 and 0.27. The Young's moduli in armchair and zigzag directions exhibited similar values of 100.9 and 99.5 GPa, respectively. For t-MoSe2, much lower fracture strengths of 6.1 and 6.3 GPa, fracture strains of 0.13 and 0.15, and Young's moduli of 83.7 and 83.0 GPa were predicted under the same conditions. A total of 700 MD simulation cases were calculated under different impact factors and initial conditions, which were subsequently fed into the support vector machine (SVM) algorithm for ML modeling. After training, the ML model could predict the mechanical properties of both MoSe2 types given only the input features such as chirality, temperature and strain rate.