3.03 - High-Pressure Phase Diagrams of the Systems Containing Carbon and BN

Abstract

Spontaneous crystallizations of diamond and cubic boron nitride (cBN) at high pressure have been analyzed in terms of phase diagrams and rate of nucleation and crystal growth. It is shown that the position of low-temperature boundary of the diamond crystallization region in the p,T diagram of carbon is defined by the line of metal–carbon eutectic (peritectic) reaction. Diamond–graphite equilibrium line defines the position of high-temperature boundary of the diamond crystallization region. For the fluid-containing systems, the position of the low-temperature boundary of the cBN crystallization region in the p,T diagram of boron nitride is defined either by the line of the incongruent melting of the BN compound with the solvent or by the kinetics of the cBN nucleation and crystal growth. The position of the high-temperature boundary of the p,T region of the cBN crystallization is always defined by the kinetic factors.