Diamond-to-graphite transformation under hypersonic impact

TL;DR

This study investigates how diamond embedded in a ceramic matrix transforms into graphite during hypersonic impact, revealing the phase change mechanism under extreme conditions.

Contribution

It demonstrates the shock-induced diamond-to-graphite transformation in a ceramic composite during hypersonic impact, a novel insight into phase changes under extreme impact conditions.

Findings

Diamond transforms into graphite during impact

Energy absorption occurs via phase change

Characterization reveals shock-induced phase interfaces

Abstract

Diamond to graphite transformation is a complex kinetically driven process which has been studied under various conditions for its fundamental importance. We report the transformation of diamond embedded ceramic matrix composites during hypersonic impact. Diamond particles embedded in cubic boron nitride matrix provide a superhard composite that was subjected to high impact collisions of metal projectiles travelling at speeds reaching Mach 8.45. Our observations suggest that the energy absorption and fracture of the composite is primarily enabled via the phase change of diamond into graphite. Characterization of the impact-fractured composite shows transformed diamond particles and provides details of the shock-induced phase transformation and the nature of diamond-graphite interfaces formed during rapid phase change. The study provides new understanding of phase transformation of diamond under extreme conditions.