49 / 2023-04-10 17:25:43

Physical Properties and Phase Transition of Low Z Materials under Dynamic High Pressure

高压物理与材料科学 > 动高压-II

The equation of state, physical properties, and phase states of materials under high pressure has been a fundamental scientific issue of long-term concern. Laser driven experiments can mimic extreme conditions in the laboratory, explore physical processes of TPa pressure range, 10000 K temperature range, and femtosecond to microsecond scale time span, creating conditions for research on high pressure and high strain rate material properties. With the rapid development of large laser devices and laser driven platforms based on advanced X-ray sources, improving the supporting experimental diagnostic technology and exploring the physical process of dynamic response of materials under high pressure have important application value in many fields, such as astrophysics, inertial confinement fusion, national defense and military, and basic research of materials. This work is based on laser driven shock experiments, combined with macroscopic shock wave diagnostic methods such as VISAR and SOP, and in-situ X-ray microscopic diagnostic methods, to conduct experimental research on the equation of state and phase transition of low Z materials. Based on the Shenguang II high-power laser platform, we carried out experimental research on the high-pressure equation of state and phase transition of liquid deuterium. Main Hugoniot and secondary reverse shock compression measurements were performed on liquid deuterium over a wide pressure range. The main Hugoniot and secondary reverse shock compression reached the highest pressures of~240 GPa and~830 GPa, respectively. Our independent Hugoniot and reflection shock experimental data are consistent with the WEOS model over a wide pressure range (27-830 GPa). These high-precision experimental results establish an important reference equation of state on deuterium. Based on the fourth generation free-electron laser device, through the simultaneous use of in-situ X-ray diffraction and small angle X-ray scattering, the growth process of nanodiamonds dissociated from C-H-O mixture under high pressure was recorded with unprecedented data quality, providing evidence of the nanodiamonds formation kinetics from C-H-O samples under the internal state of the planet, and verifying the positive support effect of oxygen atoms on C-H phase separation, It also demonstrates the strong potential of in-situ XRD combined with SAXS technology to accurately describe chemical reactions under extreme pressure and temperature conditions on a nanosecond time scale. The implementation of the diagnostic method combining VISAR, in-situ XRD, and SAXS under shock compression in this work will provide important reference significance for the joint use of multiple diagnostic platforms in shock compression experimental research.