Detection of a P-induced liquid ⇌ solid-phase transformation using multiple acoustic transducers in a multi-anvil apparatus

Abstract

A technique for detecting and measuring phase transitions in a multi-anvil apparatus by measuring the change in travel time for a longitudinal sound wave as a function of pressure is reported. The system measures the time for pulsed ultrasonic signals to travel through a high pressure assembly with a sample in the center. Upon phase change from liquid to solid, the travel time shows an abrupt decrease due to the intrinsic increase in velocity in the sample and a reduced delay between the triggering of an amplitude threshold and the arrival of the waveform. As a proof of concept, results are shown for mercury as it undergoes pressure-induced liquid ⇌ solid transitions at room temperature. We propose that this non-destructive technique may be valuable in situations where other in situ probing techniques cannot be readily used to provide information about changes of state and potentially to study transition kinetics at high pressures as well.

Keywords:

• phase transitions
• ultrasonics
• high pressure
• multi-anvil apparatus
• Hg

Acknowledgements

We thank Dr. W. Yong and J. Jacobs for their help with some of the technical aspects of this study. We also thank the reviewer for helpful comments.

Disclosure Statement

Timothy Officer and Richard A. Secco have no financial interest of benefit arising from direct applications of this research.

Additional information

Funding

This work was supported by grants to RAS from the Canadian Foundation for Innovation (CFI) [grant number 11860]; Natural Science and Engineering Research Council's (NSERC) Discovery program [grant number 105604-2013]; Research and Technology Initiative (RTI) [grant number 406998-2011]; and Western University's Academic Development Fund (ADF) [grant number 11-215]. Timothy Officer was supported by a NSERC Post Graduate Scholarship and an Ontario Graduate Scholarship.