FeMn粉末触媒对合成金刚石的影响

 利用FeMn粉末触媒在国产六面顶压机上进行了合成金刚石单晶的实验,研究了高温高压条件下（5.7 GPa、1 550 ℃）,石墨-FeMn粉末触媒体系中金刚石单晶的生长特性。通过光学成像显微镜观测表明：合成出的金刚石单晶呈浅黄色,晶形完整,且都是八面体,晶体里含有白色物质,粒度集中在0.3~0.5 mm;通过扫描电镜观测了晶体的表面形貌,表面有熔坑;通过穆斯堡尔谱,发现粉末触媒里主要是FeMn合金和独立状态的Fe,金刚石内部主要是Fe和Fe₃C;利用X射线荧光光谱,检测出样品里有Fe和Mn元素。     

Temperatures, pressures and stresses during laser shock processing

Mathematical models are developed to calculate the temperatures, pressures and stresses during laser shock processing for time-modulated (ramp-up, ramp-down and rectangular) laser pulses. Three different shock processing configurations are also considered: non-ablative exposure, ablative exposure and confined ablation with coating. The results for iron show that the plasma pressure reaches an average value of 9 GPa in direct ablation configuration and plays a dominant role for all three types of laser pulses. In the case of confined geometry, the plasma pressure reaches an average value of 20 GPa. All calculated pressures and stresses exceed the yield strength of the workpiece, indicating plastic deformation. It is also shown that pulses with short rise times yield higher plasma pressures.     

Effects of Hydrostatic and Chemical Pressures on Impurities Determined through Optical Parameters

A survey on the influence of hydrostatic and chemical pressures upon optical properties due to Transition-Metal impurities in insulators is offered in this article. Aside from recalling the theoretical framework where the properties of impurities in insulating materials are reasonably explained particular attention is paid to the dependence of crystal field and charge transfer transitions upon the impurity-ligand distance, R . By means of 10 Dq dependent d-.d transitions or the energy of charge transfer transitions it is pointed out that j R variations around 0.1 pm can be detected. The R dependence of 10 Dq is shown to determine also the corresponding dependence of Huang-Rhys factors and Stokes shift. The Huang-Rhys factor, S A , of the A 1 local mode is found to increase when R does a conclusion supported by recent experimental data on Cs 2 NaScCl 6 : Cr 3+ under hydrostatic pressure. The increase of the Stokes shift when R increases observed in the series of cubic fluoroperovskites doped with Mn 2+ is also discussed. It is pointed out that for the same j R variation, j y A changes produced by chemical pressures can be bigger than those produced through a hydrostatic pressure.     

Infrared Spectra of Benzene at High Pressures

Mid-infrared spectra in the ranges 400-1800 and 2700-4000 cm^-1 are reported for benzene samples in diamond anvil cells at ambient temperature and pressures up to 10 GPa. The freezing pressure is confirmed to be 0.1±0.05 GPa. Changes in the spectra and in the sample appearance indicate that sluggish solid state phase transitions occur near 2.0 and 4.0 GPa. The wave number shifts with pressure for 27 selected peaks are plotted. Their small increases show that only minor distortions of the molecules occur, and there is no evidence of any weakening of intramolecular bonds in this pressure range.     

浮压下马尾松的干燥特性及水分迁移机理初探

本文阐述了马尾松在浮压真空条件下的干燥特性．实验结果显示,浮压干燥比常压干燥能明显加快木材内水分迁移的速率,特别是在低含水率阶段（纤维饱和点以下）更明显．文中还对浮压条件下细胞壁内吸着水的迁移机理进行了初步的探讨分析．     

Raman Spectra of Selenium Dioxide at High Pressures

Raman spectra of selenium dioxide at ambient temperature and at pressures up to 10 GPa are reported. There is no evidence of any structural phase transitions in this pressure range, and only minor perturbations of the electronic states are observed. Shifts of normal mode wavenumbers with pressure are used to deduce percentage changes in the principal force constants. Interchain interactions sharply increase with pressure, whereas the stronger interchain forces show smaller increases. the Se-O bonds in side branches slightly weaken as a result of charge transfer to neighbouring bonds. the effects of pressure and temperature on the spectra are briefly compared.     

Effects of applied magnetic field and pressures on the magnetic properties of nanocrystalline CoFe2O4 ferrite

Nanocrystalline CoFe₂O₄ ferrite with crystallite sizes of 30 nm have been successfully prepared by an emulsion method. X-ray diffractometer (XRD) shows that nanocrystalline CoFe₂O₄ ferrite possesses face center cubic structure. Crystal structure of the CoFe₂O₄ nanocrystals will not be changed by the applied magnetic field and pressures. The obtained CoFe₂O₄ nanocrystalline powders were pressed into thin columns with different pressures. Meanwhile, the dependences of the applied pressures and the direction of applied magnetic field on the magnetic properties of the CoFe₂O₄ nanocrystals were investigated in detail using vibrating sample magnetometer (VSM). The pressed CoFe₂O₄ nanocrystal gains the most excellent magnetisms in a parallel applied magnetic field.