Nanosecond Ultrasonics to Study Phase Transitions in Solid and Liquid Systems at High Pressure and Temperature

Bonner, B P ; Berge, P A ; Carlson, S C ; Farber, D L ; Akella, J

Lawrence Livermore National Laboratory

关键词: Lawrence Livermore National Laboratory;    Dimensions;    Pistons;    75 Condensed Matter Physics, Superconductivity And Superfluidity;    36 Materials Science;   

DOI  :  10.2172/908907
RP-ID  :  UCRL-TR-229901
RP-ID  :  W-7405-ENG-48
RP-ID  :  908907

美国|英语

来源: UNT Digital Library

【 摘 要 】

This report describes the development of a high-frequency ultrasonic measurement capability for application to the study of phase transitions at elevated pressure and temperature. We combined expertise in various aspects of static high-pressure technique with recent advances in wave propagation modeling, ultrasonic transducer development, electronic methods and broadband instrumentation to accomplish the goals of this project. The transduction and electronic systems have a demonstrated bandwidth of 400 MHz, allowing investigations of phenomena with characteristic times as short as 2.5 nS. A compact, pneumatically driven moissanite anvil cell was developed and constructed for this project. This device generates a high-pressure environment for mm dimension samples to pressures of 3 GPa. Ultrasonic measurements were conducted in the moissanite cell, an LLNL multi-anvil device and in a modified piston cylinder device. Measurements for water, and elemental tantalum, tin and cerium demonstrate the success of the methods. The {gamma}-{alpha} phase transition in cerium was clearly detected at {approx}0.7 GPa with 75 MHz longitudinal waves. These results have direct application to important problems in LLNL programs, as well as seismology and planetary science.