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41.
Electronic and structural properties of antiphase boundaries in group III-V semiconductor compounds have been receiving increased attention due to the potential to integration of optically-active III-V heterostructures on silicon or germanium substrates. The formation energies of {110}, {111}, {112}, and {113} antiphase boundaries in GaAs and GaP were studied theoretically using a full-potential linearized augmented plane-wave density-functional approach. Results of the study reveal that the stoichiometric {110} boundaries are the most energetically favorable in both compounds. The specific formation energy γ of the remaining antiphase boundaries increases in the order of γ{113} ≈ γ{112} < γ{111}, which suggests {113} and {112} as possible planes for faceting and annihilation of antiphase boundaries in GaAs and GaP. 相似文献
42.
Vladimir Brailovski Patrick Terriault Sergei Prokoshkin 《Journal of Materials Engineering and Performance》2002,11(6):614-621
Shape memory alloys (SMA) suffer from the same impairing mechanisms experienced during cycling loading by classic alloys.
Moreover, SMA fatigue behavior is greatly influenced by thermomechanical cycling through the zone of thermoelastic phase transformation,
which is the basis of shape memory and superelasticity effects. Since the fatigue resistance of any material can be improved
by an appropriate thermomechanical treatment, in the present work combined differential scanning calorimetry and microhardness
testing were used to determine an optimum annealing temperature for the cold-worked Ni-50.1%Ti alloy. The optimization is
based on the assumption that latent heat of transformation is proportional to the mechanical work generated by SMA upon heating,
while material hardness is related to the yield stress of the material. It is supposed that an optimum trade-off in these
two properties guarantees the best dimensional and functional stability of SMA devices. The level and stability of the mechanical
work generated by the material during low-cycle fatigue testing are considered criteria for the material performance and thus
of the validity of the proposed optimization procedure. 相似文献
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44.
Prof. Sergei S. Kruglikov Valeri I. Kharlamov Prof Tigran A. Vagramyan jr 《金属精饰学会汇刊》2013,91(6):189-192
Some features of microdistribution of copper-based binary alloys and their components have been studied. If the codeposition rate of the more electropositive component (copper) is at least partially controlled by diffusion, antilevelling takes place for the alloy as a whole. Considerable enrichment of the deposit with respect to the more electropositive component is observed on micropeaks, provided the electrodeposition rate of the more electronegative component is nearly constant at all points of the microprofile (electrodeposition of Cu-Ni alloy from pyrophosphate solution). If the more electropositive component produces a depolarizing effect on the deposition of the more electronegative component, microdistribution of the latter also becomes non-uniform in spite of the absence of diffusion control (Cu-Cd and Cu-Zn alloys). In this case an overall alloy microdistribution shows stronger antilevelling; however, the composition of the deposit becomes more uniform over the microprofile. 相似文献
45.
Tallison O. Abreu Roterdan F. Abreu Felipe F. do Carmo Wellington V. de Sousa Helenilson de O. Barros José E.V. de Morais João P.C. do Nascimento Marcelo A.S. da Silva Sergei Trukhanov Alex Trukhanov Larissa Panina Charanjeet Singh Antonio S.B. Sombra 《Ceramics International》2021,47(11):15424-15432
This work presents the dielectric properties of YNbO4 (YNO)–TiO2 composites in the microwave range. X-ray diffraction analysis demonstrates that the addition of TiO2 to YNO results in the formation of a Y(Nb0.5Ti0.5)2O6 phase. In the microwave range, the values of permittivity and dielectric loss did not present major changes with the increment of TiO2. Moreover, the addition of TiO2 results in an improvement in the thermal stability of YNO, with YNO63 demonstrating a resonant frequency of ?8.96 ppm.°C?1. We utilised numerical simulations to evaluate the behaviour of these materials as dielectric resonator antennae and it is found that they exhibit a reflection coefficient below ?10 dB at the resonant frequency, with a realised gain of 4.94 – 5.76 dBi, a bandwidth of 665–1050 MHz and a radiation efficiency above 84%. Our results indicate that YNO–TiO2 composites are interesting candidates for microwave operating devices. 相似文献
46.
Sergei F. Burlatsky Vadim V. Atrazhev Mallika Gummalla Dave A. Condit Fuqiang Liu 《Journal of power sources》2009,190(2):485-492
Proper water management in a hydrogen-fueled polymer electrolyte membrane (PEM) fuel cell is critical for performance and durability. A mathematical model has been developed to elucidate the effect of thermal conductivity and water vapor diffusion coefficient in the gas diffusion layers (GDLs). The fraction of product water removed in the vapor phase through the GDL as a function of GDL properties/set of material and component parameters and operating conditions has been calculated. The current model enables identification of conditions wherein condensation occurs in each GDL component. The model predicts the temperature gradient across various components of a PEM fuel cell, providing insight into the overall mechanism of water transport in a given cell design. The water condensation conditions and transport mode in the GDL components depend on the combination of water vapor diffusion coefficients and thermal conductivities of the GDL components. Different types of GDLs and water transport scenarios are defined in this work, based on water condensation in the GDL and fraction of water that the GDL removes through the vapor phase, respectively. 相似文献
47.
A wavelength-independent method for optical gating, based on the optical Kerr effect, has been demonstrated. Using this method, we produced 100-ps, 10-kW, two-wavelength pulses (10.3 and 10.6 microm) with a signal-to-background ratio contrast of 10(5) by slicing a long CO2 pulse. The capability of gating consecutive pulses separated on a picosecond time scale with this method is also shown. 相似文献
48.
49.
50.
K. N. Chakalev L. K. Belopukhov 《Journal of Engineering Physics and Thermophysics》1968,14(4):378-382
A method of determining the specific heat of liquids is described. The test liquid is placed in a special steel container. The sample is heated by electron bombardment with an electron beam focused by electrostatic lenses. 相似文献