【作者】 贾茹；

【导师】 经福谦；

【作者基本信息】 西南交通大学 ， 固体力学， 2008， 博士

【摘要】 高压物理学是研究物质在高压作用下的力学、光学、电学、磁学特性,以及高压下物质的微观结构、状态方程、相变等等。由于高压研究可以发现一些物质在常压下不能表现出来的新现象、新规律、新性能或新相,所以它为新材料的制备、合成与改性提供了重要的理论依据和实验基础。本论文共分为两个部分,第一部分为高温高压下氩的布里渊散射研究,属于高压下的物性研究:第二部分为快速增压制备大块非晶硫,属于高压下新材料的制备。分别摘要如下:(一)高温高压下氩的布里渊散射研究。氩分子为简单的单原子分子,由于其外层电子具有满壳层结构,所以在理论计算研究和实验对比中已成为一个非常理想的研究体系。高温高压下氩精确的状态方程及其热力学性质在检验物理模型、分子间作用势特别是多体相关势中有非常重要的意义。本论文利用高温高压下原位布里渊散射系统,对液氩首次进行了高温高压布里渊散射研究:(1)结合激光加热技术、金刚石对顶砧高压技术、高温高压原位布里渊散射系统,利用磁控溅射镀膜技术和光刻技术,首次获得了氩在14.58GPa熔融状态下布里渊光谱和体声速;(2)结合外部电加热的金刚石对顶砧技术及高温高压原位布里渊散射系统,同时采用60°平板式和180°背散的散射几何配置,首次获得了液氩在388K、476K和503K下的布里渊散射光谱,并由此得到了液氩高温高压下的体声速、折射率、等温状态方程、绝热体弹模量等:(3)从我们所获得的液氩的状态方程出发,结合文献理论计算结果,从实验上证实了液氩分子间的多体影响对氩分子间两体势起到软化作用;发现在等温线上,多体关联对状态方程(密度)的影响随压力的增加而增加,随温度的增加而减小:(4)通过对氩的固液两相共存区布里渊光谱的分析,首次获得了氩的固液转变体积差和熔化潜热等重要数据。(二)快速增压方法制备大块非晶硫非晶态是指物质内部结构中原子呈短程有序、长程无序排列的一种状态,而非晶态材料做为新型的功能材料已获得越来越广泛的应用。对比于传统的非晶制备方法,考虑到压力和温度在热力学上的对等关系,我们认为对熔融液体因快速改变压力导致的凝固与快速改变温度一样可以获得亚稳态结构,同时因其分子的凝聚过程将不再受到热传导率的限制,由此可获得大块非晶材料。本部分论文利用本实验室的快速增压压机对熔融态硫进行了快速增压实验,增压速度和幅度分别为0.1GPa/ms和2GPa。做为对比实验,我们还设计了三种不同的熔融硫的凝固过程:常压下自然冷却、高压下淬火和快速增压。对四组实验所获得固态硫分别进行X射线衍射和差示扫描热分析后,发现快速增压方法能够有效地抑制晶态的生长,获得纯度较高的非晶态硫。虽然高压下淬火和慢速增压也可获得非晶态,但这两种方法均不能完全抑制晶体生长,所制备出的样品中晶态与非晶态共存。通过快速增压过程所获得的非晶硫块直径为20mm,厚度为3mm。这是我们第一次通过快速增压方法成功地制备出单质非晶材料。研究结果显示,快速增压方法是一种有效制备大块非晶材料的新途径。更多还原

【Abstract】 High pressure physics is a subject that studies the mechanics, optics, electricity, magnetism, microstructure, equation of state and phase transformation of materials under high pressure. Because high pressure research can discover the new phenomena, new properties, new characters of materials or even new substances which do not appear at ambient condition, it provides a great of important experimental and theoretical evidence to synthesize and modify the new materials. Our work has two parts. One is the Brillouin study of argon at high pressures and high temperatures. It is about the physics properties measurement research at high pressure. Another part is the rapid compression induced solidification of bulk amorphous sulfur. It is about the synthesis of new materials. The summery is followed.First part is the Brillouin study of argon at high pressures and high temperatures. Because of the closed-shell electronic configuration, the single-atom argon molecular is an ideal system allowing fruitful comparisons between experiments and theoretical calculations. The accurate equation of state of argon is very important to determine the interatomic potentials, including possible effects of many-body forces. In present study, the Brillouin measurement of argon has been performed at high pressures and high temperatures. First, with the laser heating technology and diamond anvil cell (DAC), the Brillouin scattering system for in situ measurements under high pressure and high temperature has been applied in argon. With the help of film deposition technique and photolithographic shaping method, the Brillouin scattering spectra and the longitudinal sound velocities of liquid argon were determined at 0.85GPa and 14.58GPa. Secondly, we applied the in-situ high pressure and high temperature Brillouin scattering system and external resistant heated diamond anvil cell to study the liquid argon at high pressures and high temperatures. The 60°platelet and 180°back -scattering Brillouin scatterings were performed. The velocities, refractive index, experimental equation of state, and adiabatic bulk modulus as a function of pressure of liquid argon at high P-T conditions were determined for the first time. Thirdly, based on the comparison between the equation of state of liquid argon obtained by present study and the result of previous calculation, we proved the softening consequence of possible many-body contribution to the interatomic potential. It indicated that the many-body contribution to the density of liquid argon gradually increases with increasing pressure and decreases with increasing temperature. Last, with the Brillouin spectra of co-existence of liquid and solid along argon equilibrium curve, the experimental solidifying parameters of argon at equilibrium at high pressures and high temperatures are obtained for the first time.Second part is the rapid compression induced solidification of bulk amorphous sulfur. Amorphous state is a state that the molecular structure is arranged orderly in short distance but disorderly in long distance. As special functional material, amorphous substances have been used more and more widely. Contrast to the traditional methods to produce amorphous solid and considering the equal effect of pressure and temperature in thermodynamic, we believe that changing the pressure rapidly has the same thermodynamic effect as changing the temperature abruptly in the process of producing metastable structure. Furthermore, in the rapid compressing process the whole sample, whether surface or interior, is held in a synchronously thermal environment, where the thermal conduction is not working. As a result, the size of the sample solidified as amorphous or metastable structure should not be limited by its thermal conductivity. In present study, we applied the rapid compression apparatus to investigate the solidification behavior of liquid sulfur, which a high pressure jump from ambient pressure to 2GPa with a speed of 0. 1GPa/ms were performed. The contrast experiments are designed as natural cooling at ambient pressure, quenching at high pressure and slow compression. All the solid sulfur samples thus obtained were analyzed by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results showed that rapid compression can effectively suppress the crystallization of liquid sulfur and induce the solidification of an amorphous phase from the melt in sulfur. Furthermore although the amorphous phase can also be obtained by quenching at high pressure and slow compression, these two processes are not so effective as to suppress the crystallization completely and the samples obtained are coexisted with crystals and amorphous. The sample obtained by rapid compression is a bulk amorphous solid 20mm in diameter and 3mm in thickness. It indicates that the rapid compression method is a promising alternative for making bulk amorphous solids for more substances.更多还原