In this work, the ultrafine nanoporous Ag ribbons were achieved through addition of 2 at.%–6 at.% Ce into the melt-spun Cu-Ag alloys and applying different electrochemical dealloying potentials. The dendritic morphology of the ligaments in the dealloyed Cu80Ag20 alloy varied to be equiaxial due to the addition of Ce, and the pore size reduced from 200 nm to less than 60 nm. The nanoporous Ag with an average pore size of ∼15 nm was obtained from the Cu74Ag20Ce6 alloy. The pore and ligament sizes of the nanoporous Ag prepared from the Cu76Ag20Ce4 alloy exhibited an increasing tendency with the increase of applied potentials, while the dealloyed Cu78Ag20Ce2 had an opposite variation. Moreover, the addition of Ce into the Cu-Ag alloys also promoted the dealloying. Nanoporous Ag exhibited the stronger enhancement of the surface enhanced Raman scattering effects with the increase of Ce contents in the precursory alloys.

The good quality single crystal ZnWO4:Yb3+ was grown by Czochralski method and the spectra were measured. The fluorescence lifetime at 1017 nm was measured to be 644 μs and the radiative lifetime was 209 μs. The laser parameters, βminIsat as well as Imin have been calculated to be 4.6%, 14.4 Kw/cm2, 0.66 Kw/cm2, respectively. The Stark-level components of the 2F7/2 and 2F5/2 were also determined. End-pumping crystal ZnWO4:Yb3+ with 975 nm laser diode, we investigated the laser output property. The highest output power at wavelength 1017 nm was obtained to be 0.5 W, corresponding to the pumping power of 10 W and the threshold was about 2 W.

PACS: 71.20.Eh; 78.20.-e; 65.60. +a, 42.55.Xi, 42.55.Ye, 42.60.Gd.

A dislocation–density-based model for slip transmission at variant boundaries and a microstructural failure criterion accounting for variant cleavage planes have been developed to determine optimal variant distributions for significantly improved ductility, through increased slip transmission, and fracture toughness, through increased resistance to crack propagation, in martensitic steels with refined blocks and packets. A crystal plasticity framework, accounting for variant morphologies and orientation relationships that are uniquely inherent to lath martensite, and specialized finite-element methodologies using overlapping elements to represent evolving fracture surfaces are used for a detailed analysis of fracture nucleation and intergranular and transgranular crack growth. The results indicate that the block sizes, variant orientations, and distributions are the key microstructural characteristics for toughening mechanisms, such as crack arrest and deflection, and for desired ductility, delayed crack nucleation, and greater fracture toughness. This approach can be the basis for validated design guidelines for the desired optimal behavior of high-strength and toughness steels.

We prepared hybrid aluminum oxide (Al2O3)/polymethyl methacrylate (PMMA) composites with tunable lamellae, produced through a two-step synthetic method: fabrication of inorganic scaffolds via ice-templating, followed by organic infiltration polymerization as a substitute for the sublimed ice. The final lamellar hybrid products show anisotropic physical properties. The thermal conductivity in both principal directions was determined for three different samples as a function of temperature (∼3 K–300 K). Typical room temperature thermal conductivities are in the range of 0.5–2.5 W/(m K), depending on the composition and direction. Across the lamellae, the thermal conductivity is well modeled by a linear series of thermal resistors, and along the lamellae it is well represented by parallel thermal resistors of continuous slabs of PMMA and ∼200-μm long slabs of Al2O3, joined by PMMA. From the thermal conductivity perspective, the Al2O3/PMMA composite is a nacre mimic.

In this article, we report the unique microstructural characteristics of YBa2Cu3O7-x (YBCO)/BaSnO3 (BSO) nanocomposite thin films on LaAlO3 (LAO) substrates. The BSO secondary phase grows as self-assembled vertically aligned nanopillars uniformly distributed in the superconducting YBCO matrix. Detailed microstructure and strain studies including x-ray diffraction, cross-section and plan-view transmission electron microscopy, and geometric phase analysis reveal that, as the BSO doping concentration varied from 2 mol% to 20 mol%, the nanopillar density increased from 0.26 × 1011/cm2 to 1.44 × 1011/cm2 while the diameter of the nanopillars remains relatively constant (7–8 nm in diameter). The strain state of the YBCO matrix is affected by both lateral and vertical lattice strains; while, the BSO lattice is strongly tuned by YBCO rather than the substrate. A high-density array of dislocations in the order of 1013/cm2 was observed along the vertical heterogeneous interfaces throughout the YBCO film thickness for all doping concentrations.

Two-micrometer-thick Pb0.97La0.02(Zr0.98Ti0.02)O3 (PLZT) antiferroelectric films, with the addition of different PbO insert layer, were successfully fabricated on LaNiO3/Si substrates through a sol–gel method, and their microstructure and the energy storage performance were investigated in detail. X-ray diffraction curves and scanning electron microscopy images indicated that all the PLZT films showed a strong (042)-preferred orientation and had a uniform surface microstructure. The electrical measurements illustrated that the capacitive density and saturation polarization values of the thick films were improved by the PbO insert layer. As a result, PLZT thick films with 0.4‐M/L PbO‐insert layer possessed an enhanced energy storage density and energy storage efficiency, which were 25.2 J/cm3 and 52.3% measured at 984 kV/cm, respectively. Moreover, after 106 switching, the Jreco values of the corresponding films were only declined from 17.5 to 16.1 J/cm3, indicating good fatigue endurance.

The piezoelectric β-phase of poly(vinylidene fluoride) (PVDF) has been synthesized through solution route in presence of varying percentage of silicon carbide (SiC). Various measurements were conducted to analyze the effect of SiC addition on structural, mechanical, and dielectric properties, as also the properties affecting hydrophilicity and morphology of PVDF. The x-ray diffraction, Fourier transform infrared spectroscopic and differential scanning calorimetry analyses confirm the presence of β-phase of PVDF on addition of SiC. The Young’s modulus of the composites increases as compared with pristine PVDF. The hydrophilic nature of the composites improves with increasing SiC content. Dielectric constant increases in composites, especially at lower frequency range and the relaxation pattern in the crystalline phase changes significantly causing reduction of relaxation frequency with increasing SiC concentration.

Lee and Radok [J. Appl. Mech.27, 438 (1960)] derived the solution for the indentation of a smooth rigid indenter on a linear viscoelastic half-space. They had pointed out that their solution was valid only for regimes where contact area did not decrease with time. In this article, a large number of finite element simulations and one typical experiment demonstrate that Lee-Radok solution is approximately valid for the case of reducing contact area. Based on this finding, three semiempirical methods, i.e., Step-Ramp method, Ramp-Ramp method and Sine-Sine method, are proposed for determination of shear creep compliance using the data of both loading and unloading segments. The reliability of these methods is acceptable within certain tolerance.

ZnO:Al and Zn1-xMgxO:Al films have been deposited by magnetron sputtering from ceramic targets at substrate temperatures from room temperature to 500 °C. We studied the relation between the electronic transport and the structural properties as a function of the deposition temperature. Films with the lowest resistivity (7·10−4 Ω cm for ZnO:Al and 3.6·10−3 Ω cm for Zn1-xMgxO:Al) can be prepared for deposition temperatures around 300 °C. This optimum is accompanied by the highest carrier concentration and the highest Hall mobility. Changes in crystalline quality and free carrier concentration are explained as a result of a bombardment of the films by high energetic negative oxygen ions during growth and by phase segregation for higher deposition temperatures. The dependence of the Hall mobility on the carrier concentration can be explained by grain barrier scattering for n <≈ 5·1020 cm−3 and by ionized impurity scattering for n >≈ 5·1020 cm−3. From the fit of the μ(n) dependence for both materials a trap density at grain boundaries of Nt ≈ 2.3·1013 cm−2 was determined.

First-principles fully relaxed tensile and shear test simulations were performed on tilt Fe grain-boundaries (GBs) with and without hydrogen (H) segregation, to investigate the mechanisms of GB embrittlement enhanced by H segregation. Premature fracture was found in the H-segregated GB, compared with the clean GB, in the tensile test simulations. The Fe–H bond showed covalent-like and ion-like characteristics. The covalent-like characteristics reinforced the Fe–Fe bonds, but the ion-like characteristics weakened the Fe–Fe bonds as a result of charge transfer. The effect of the latter increased with increasing strain, and prevailed over the former, resulting in GB embrittlement. In the shear test simulations, variation in the GB energy for the H-segregated GB was almost the same as that for the clean GB. This is because bond-breaking and rebonding occur concurrently in GB shearing and the variations in charge transfer during shear straining are less than those during tensile straining.

We discuss the relative complexity and computational cost of several popular many-body empirical potentials, developed by the materials science community over the past 30 years. The inclusion of more detailed many-body effects has come at a computational cost, but the cost still scales linearly with the number of atoms modeled. This is enabling very large molecular dynamics simulations with unprecedented atomic-scale fidelity to physical and chemical phenomena. The cost and scalability of the potentials, run in serial and parallel, are benchmarked in the LAMMPS molecular dynamics code. Several recent large calculations performed with these potentials are highlighted to illustrate what is now possible on current supercomputers. We conclude with a brief mention of high-performance computing architecture trends and the research issues they raise for continued potential development and use.