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Temperature Dependence of the Lattice Parameters of Cu2?–?xSe (0.03 ≤ x ≤ 0.23) Powders Fabricated by Mechanochemical Synthesis
摘要： The Cu2 – xSe (0.03 ≤ x ≤ 0.23) powders fabricated by mechanochemical synthesis have been studied by X-ray diffraction. The in situ study has been carried out for the temperature dependences of the lattice parameters, the structures, and the phase compositions of the powders in the temperature range 25–350°C. The powder compositions are shown to differ from the charge compositions and are shifted to lower copper concentrations. The estimation of peak half-widths of the cubic β phase indicates an increase in the structure imperfection after the phase transition from the α phase to the β phase of Cu2 – xSe at ~140°C. It is shown that the superpositions of the subtraction solutions (copper vacancies) and interstitials solutions (copper atoms in interstitial sites), whose proportion is changed as a function of temperature and the deviation from stoichiometry, are in the thermodynamic equilibrium in the copper selenide solid solution at room temperature. The change in the slope of the dependence of the lattice parameter of the powder Cu2 – xSe samples on the composition (0.03 ≤ x ≤ 0.23) in the temperature range 25–350°C enables the suggestion that interstitial copper atom concentration increases with temperature and deviation from stoichiometry.
关键词： phase transition,lattice parameters,mechanochemical synthesis,Cu2 – xSe,X-ray diffraction,thermodynamic equilibrium
更新于2025-09-23 15:21:01
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Modeling radiative-shocks created by lasera??cluster interactions
摘要： Radiative-shocks induced by laser–cluster interactions are modeled using radiation-hydrodynamic simulations. A good agreement—in both shock velocity and density pro?les—is obtained between experiment and simulations, indicating that non-local thermodynamic equilibrium (NLTE) radiative effects are important in the experimental regime examined, particularly at early times ((cid:2)30 ns) due to the elevated temperatures ((cid:3)35 eV). The enhanced NLTE radiative emission causes the shock to be reduced in amplitude, increased in width, and reduced in propagation velocity, while the amplitude of the radiative precursor is increased. As the density and temperature conditions are relatively modest, this potentially has important implications for the scalings that are used in laboratory–astrophysics to transform between laboratory and astrophysical scales, which do not hold for non-LTE systems.
关键词： non-local thermodynamic equilibrium,laboratory–astrophysics,radiation-hydrodynamic simulations,radiative-shocks,laser–cluster interactions
更新于2025-09-23 15:19:57
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Comparative study of electron temperature in cascaded arc Ar/N <sub/>2</sub> plasma using laser Thomson scattering combined optical emission spectroscopy approach
摘要： The expanding cascaded arc Ar/N2 plasma has been investigated by both the active and passive optical diagnostic technologies. In the investigation, the laser Thomson scattering (LTS) and optical emission spectroscopy (OES) have been adopted to measure electron temperature (Te) and electron excitation temperature (Texc), respectively. The LTS measurements show that a remarkable nonlinear behavior of Te as a function of the N2/(Ar + N2) ratio is found, which is caused by the collective interaction between the superelastic collision and the electron-impact excitation. The superelastic collisions by the highly excited vibrational nitrogen molecules can effectively heat the free electrons, while the electron kinetic energy can be transferred to N2 molecular internal energy via the electron impact with N2 in the ground state. The difference between Texc and Te demonstrates that the cascaded arc Ar/N2 plasma significantly deviates from the local thermodynamic equilibrium. This would be useful for improving our further understanding of nonequilibrium plasma and extending applications of the cascaded arc Ar/N2 plasma.
关键词： cascaded arc Ar/N2 plasma,local thermodynamic equilibrium,laser Thomson scattering,electron temperature,optical emission spectroscopy
更新于2025-09-19 17:13:59
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Analytic Model of Spalling Technique for Thickness-Controlled Separation of Single-Crystalline Semiconductor Layers
摘要： Thickness-controlled separation of a thin layer of single-crystalline semiconductors from its bulk substrate is being developed for co-integration of compound semiconductors with silicon-based integrated-circuit (IC) chips and fabrication of high-performance flexible devices. Recently, a controlled spalling technique that can mechanically separate single-crystalline semiconductor layers has been actively demonstrated because of the process simplicity and the less limitation in materials. Here, we developed an analytic model that can precisely estimate the spalling depth. In this model, the spalling depth was calculated from the thermodynamic equilibrium condition in which total strain energy accumlated in a separated layer is balanced with the crystal binding energy. We empirically investigated the dependence of the spalling depth on the stressor layer thickness and stress, and we compared the empirical results with the suggested analytic model. We also verified that the crack initiation angle of the spalling process is determined by the binding energy contrast in the main crystal orientations in the semiconductor.
关键词： thermodynamic equilibrium condition,analytic model,spalling technique,thickness-controlled layer separation,crack initiation angle
更新于2025-09-12 10:27:22