Brillouin Scattering Study Of Argon At High Pressures And High Temperatures And Rapid Compression Induced Solidification Of Bulk Amorphous Sulfur

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.