Abrupt irreversible transformation of rhombohedral BN to a dense form in uniaxial compression of CVD material

摘要

The behavior of rhombohedral BN has been investigated under uniaxial compression along the [0001]{sub}r texture axis of a highly textured CVD rBN material (thin plate sample) in a diamond anvil cell without a gasket. An abrupt martensitictransformation of the graphite-like rBN structure to a dense cubic BN form accompanied by a distinct acoustic emission signal has been recorded at the sample center at a pressure somewhat above 5.6 GPa, which is an order of magnitude below the thresholdpressure of the transformation under hydrostatic compression.