顽火辉石的高温高压同步辐射研究

 采用同步辐射能量色散X射线衍射技术、激光加热技术和金刚石对顶砧（DAC）高压装置，在温度为2 000 K和压力为23 GPa的范围内，对采自地幔二辉橄榄岩中的顽火斜方辉石，进行了原位的高温高压能量色散X射线衍射（EDXRD）测量。实验结果表明：当压力为15.3 GPa、温度为1 600 K时（相当于地球内部410 km处的地震波不连续界面的温压环境），顽火斜方辉石转变为橄榄石的β相——瓦兹利石（Wadsleyite）相；继续加温加压至2 000 K、23 GPa时（相当于地球内部670 km处的地震波不连续界面的温压环境），顽火斜方辉石相变为钛铁矿（Ilmenite）结构和钙钛矿（Perovskite）结构的混和相。实验结果进一步证明，在地幔中存在的两个地震波不连续界面是由橄榄石、顽火斜方辉石等矿物的相变引起的。     

Raman and X-Ray Investigation of Pyrope Garnet （Mg0.76Fe0.14Ca0.10）3Al2Si3O12 under High Pressure

The compressional behavlour of natural pyrope garnet is investigated by using angle-dlspersive synchrotron radiation x-ray diffraction and Raman spectroscopy in a diamond anvil cell at room temperature. The pressureinduced phase transition does not occur under given pressure. The equation of state of pyrope garnet is determined under pressure up to 25.3 GPa. The bulk modulus KTO is 199 GPa, with its first pressure derivative K′TO fixed to 4. The Raman spectra of pyrope garnet are studied. A new Raman peak nearly at 743 cm^-1 is observed in a bending vibration of the SiO4 tetrahedra frequency range at pressure of about 28 GPa. We suggest that the new Raman peak results from the lattice distortion of the SiO4 tetrahedra. All the Raman frequencies continuously increase with the increasing pressure. The average pressure derivative of the high frequency modes （650-1000 cm^-1） is larger than that of the low frequency （smaller than 650 cm^-1）. Based on these data, the mode Grǖneisen parameters for pyrope are obtained.     

High pressure electrical transport behavior in SrF_2 nanoplates

The charge transport behavior of strontium fluoride nanocrystals has been investigated by in situ impedance measurement up to 35 GPa.It was found that the parameters changed discontinuously at each phase transition.The charge carriers in SrF_2 nanocrystals include both F~-ions and electrons.In the Fm3 m phase,pressure makes the electronic transport easier,while makes it more difficult in the Pnma phase.The defects at grain boundaries dominate the electronic transport process.Pressure could make the charge-discharge processes in the Fm3 m phase much easier,but make it more difficult in the Pnma phase.     

不同TiO2原料制备一维钛酸盐纳米材料

以不同二氧化钛为原料, 用水热法制备一维钛酸盐纳米材料. 原料一次粒径和晶体结构对一维纳米钛酸盐的形貌和结构的影响很大. 原料的一次粒径越小, 反应过程中产物的形貌和晶相转变越快; 纯锐钛矿相有利于钛酸盐纳米管的形成, 而少量金红石相则有利于纳米管向纳米线的进一步转变和晶相转变.     

石墨相C3N4的高温高压研究

为了得到超硬相的C3N4,利用石墨相C3N4(gC3N4)为实验的初始原料,利用六面顶压机高温高压实验技术,对gC3N4进行了高温高压研究.实验结果表明,在5.2 GPa、600 ℃和5.2 GPa、800 ℃两个压力和温度点,制备的样品经过X射线衍射(XRD)分析,样品仍然为gC3N4,当温度升到1000 ℃时,发现样品发生了变化,经XRD和X光电子能谱（XPS）分析,gC3N4完全分解为石墨.     

氮化碳的高压同步辐射研究

 采用金刚石对顶砧及原位同步辐射实验技术,对高温高压有机催化反应制备的氮化碳材料,进行了室温及直到44 GPa压力条件下的原位高压同步辐射X射线衍射研究,并用最小二乘法拟合了样品的Murnaghan型等温状态方程。结果表明,在室温及直到44 GPa压力条件下,石墨相C₃N₄和待定的正交相CN材料都是稳定的,没有发生明显的相变,推测正交相CN材料可能是原始材料三聚氰胺和三聚氰氯在高温高压条件下催化热解产生的某种高分子有机聚合物。     

Electroluminescence explored internal behavior of carriers in InGaAsP single-junction solar cell

The internal behaviors of carriers in InGaAsP single-junction solar cell are investigated by using electroluminescence (EL) measurements. Two emission peaks can be observed in current-dependent electroluminescence spectra at low temperatures, and carrier localization exists for both peaks under low excitation. The trends of power index α extracted from excitation-dependent EL spectra at different temperatures imply that there exists a competition between Shockley-Read-Hall recombination and Auger recombination. Auger recombination becomes dominant at high temperatures, which is probably responsible for the lower current density of InGaAsP solar cell. Besides, the anomalous "S-shape" tendency with the temperature of band-edge peak position can be attributed to potential fluctuation and carrier redistribution, demonstrating delocalization, transfer, and redistribution of carriers in the continuum band-edge. Furthermore, the strong reduction of activation energy at high excitations indicates that electrons and holes escaped independently, and the faster-escaping carriers are holes.     

GaInP/GaAs太阳电池的柔性封装及稳定性

柔性Ⅲ-Ⅴ薄膜太阳电池通常被作为空间电源在航天器上使用,而在实际应用中适宜的封装材料可以保护电池免受水分、氧化、污染物等环境因素的影响.因此,探究合适的柔性封装方案和电池性能的长期稳定性至关重要.本文利用电阻焊方法将制备好的柔性双结GaInP/GaAs太阳电池进行焊接,之后采用具有高透光性的薄膜材料和热熔胶与柔性电池进行层压封装并研究了其在恶劣储存条件下的性能稳定性和环境耐受性.研究结果表明,柔性封装太阳电池在1000 h以上的温度为85℃,相对湿度85%(85℃/85%RH)的湿热试验以及108次温度范围为–60℃—75℃的冷热循环老化试验后仍然保持了很好的稳定性,表明封装工艺对柔性太阳电池具有较好的保护作用.此外,基于二极管模型的电学仿真结果表明,柔性封装后电池性能的改变是由于载流子复合增强,从而降低了开路电压.     

无定形硒的高压同步辐射研究

采用原位高压同步辐射X射线衍射技术, 利用金刚石对顶砧(DAC)装置产生高压, 测定了无定形硒在室温下、74.3GPa的压力范围内的同步辐射X射线衍射谱. 在实验压力范围内, 发现无定形硒在10GPa到11Gpa压力范围内发生了压致结晶变化, 其结晶后的产物为六角晶体与一种新的高压金属相^{[6]<\sup>的混合体. 值得说明的是该高压金属结构一直到42GPa时仍稳定存在, 到42GPa以后才转变成正交结构. 分别观察到了在30GPa和60GPa左右发生的从单斜相到正交相和从正交相到菱方相的结构相变, 这分别与Mao等人[1]<\sup>和Akahama等人[3]<\sup>从六角结构硒晶体出发得到的实验结果相同.}     

A New Method for Preparation of Nanocrystalline Molybdenum Nitride

Nanocrystalline molybdenum nitride （γ-Mo2N） with the cubic structure is prepared by the direct-current arc discharge method in N2 gas, using metal Mo or W rod as a cathode. The x-ray diffraction （XRD） and transmission electron microscopy （TEM） are used to characterize the product. It is found that the conversion of Mo to γ-Mo2N and affinity of Mo to N2 are determined by the nitrogen pressure. Moreover, we compare the effect of Mo and W rod as a cathode for preparing γ-Mo2N. The average size of γ-Mo2N particles is about 5 nm. The rapid quenching mechanism can be used to explain the formation of nanocrystalline γ-Mo2N.