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In situ high-pressure energy dispersive x-ray diffraction experiments on polycrystalline powder TiN with NaCltype structure have been conducted with the pressure up to 30.1 GPa by using a diamond anvil cell instrument with synchrotron radiation at room temperature. The experimental results suggest that an isostructural phase transition might exist at about 7 GPa as revealed by the discontinuity of V/Vo with pressure. 相似文献
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The crystal structure and electric properties of BaTiO3 nanocrystals are studied by in situ high-pressure synchrotron radiation x-ray powder diffraction. The phase transition takes place not only in the samples of BaTiO3 nanocrystals that are tetragonal phase with grain sizes more than 100nm, but also in the samples of BaTiO3 nanocrystals that are cubic phase with grain sizes less than 100nm. The pressures of phase transition are found to increase with decrease of the grain size from about 4 to 10GPa for crystallites ranging from 200 to 10nm in radius. The bulk moduli are calculated according to Birch-Murnaghan state equation before and after the phase transition. 相似文献
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Compression Behaviour and Equation of State of Zr44.4Nb7Cu13.5Ni10.9Be24.3 Bulk Metallic Glass up to 39 GPa 下载免费PDF全文
The compression of Zr44.4Nb7Cu13.5Ni10.8Be24.3 bulk metallic glass (BMG) is investigated at room temperature up to 39 GPa using in situ high-pressure energy dispersive x-ray diffraction with a synchrotron radiation source. The equation of state of the BMG is obtained by the calculation of the radial distribution function. Pressureinduced structural relaxation is exhibited. It is found that below about 6 GPa, the existence of excess free volume contributes to the rapid structural relaxation, which gives rise to rapid volumetric change, and the structural relaxation results in structural stiffness under higher pressure. 相似文献
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利用金刚石对顶砧高压装置和激光双面加热技术, 以经700°C热处理后的吉林长白山硅藻土作为非晶态SiO2样品,在0—4GPa, 1000—1300K温压条件下开展同步辐射X射线衍射原位测试(EDXD方法), 研究非晶态SiO2在高温高压条件下的结晶转变方式. 测试结果表明, 在0.8—2.4GPa, 1000—1300K温压条件下, 非晶态SiO2转变成α-石英而非β-石英或方石英, 其结晶温度较常压下非晶态SiO2晶化所需温度明显较低, 表明压力有利于降低非晶态SiO2转变的活化能, 并与常压下的结晶产物不同. 在3—4GPa, 1300K温压条件下, 非晶态SiO2和石英均转变成了柯石英. 相似文献
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利用高压原位角散X射线衍射实验研究了ZnSe纳米带的结构稳定性。发现样品在12.6 GPa 附近存在一个从立方闪锌矿型到立方岩盐矿型的结构相变,并且在相变点附近存在较大的体积收缩,相对体积变化率达13%。利用Birch-Murnaghan 状态方程拟合,得到了闪锌矿相的体弹模量约为56 GPa,略低于体材料的体弹模量(约67 GPa);并得到其立方岩盐矿相的体弹模量约为116 GPa。高压拉曼散射实验结果表明,横光学声子模散射峰在5.5 GPa压力附近发生劈裂,纵光学声子模散射峰在12.8 GPa压力以上逐渐消失。根据角散实验的体弹模量数据,计算得到了闪锌矿相中对应不同声子模式的格林爱森常数。 相似文献
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The compressibility and pressure-induced phase transition of β-Si_3N_4 were investigated by using an angle dispersive x-ray diffraction technique in a diamond anvil cell at room temperature. Rietveld refinements of the x-ray powder diffraction data verified that the hexagonal structure(with space group P63/m, Z = 2 formulas per unit cell) β-Si_3N_4 remained stable under high pressure up to 37 GPa. Upon increasing pressure, β-Si3 N4 transformed to δ-Si_3N_4 at about 41 GPa. The initial β-Si_3N_4 was recovered as the pressure was released to ambient pressure, implying that the observed pressureinduced phase transformation was reversible. The pressure–volume data of β-Si_3N_4 was fitted by the third-order Birch–Murnaghan equation of state, which yielded a bulk modulus K_0= 273(2) GPa with its pressure derivative K_0= 4(fixed)and K0= 278(2) GPa with K 0= 5. Furthermore, the compressibility of the unit cell axes(a and c-axes) for the β-Si_3N_4 demonstrated an anisotropic property with increasing pressure. 相似文献