Phase Transformation of Turbostratic BN by Shock Compression

Using two kinds of turbostratic BN (tBN) powders with different degrees of turbostratic disorder, the shock-induced phase transformation has been investigated through recovery techniques in a pressure range 12−36 GPa. Recovered specimens were investigated by X-ray diffraction and electron microscopy. It is shown that the temperature plays an important role in promoting the tBN→cBN (zincblend-type BN) transformation and that the transformation efficiency depends strongly upon the degree of turbostratic disorder of the starting tBN. It is deduced from the results that the mechanism of the shock-induced phase transformation of tBN to cBN is a direct conversion through diffusion process and that tBN is most likely the intermediate phase via which shock-induced phase transformation of rBN to cBN proceeds under relatively low shock pressures (<50 GPa).