On the nature of wurtzite boron nitride hardening under high pressure and temperature

Abstract

The results of TEM microscopy examination of the substructure of wurtzite boron nitride particles in polycrystalline samples fabricated under high temperature and pressure are presented along with the data on microhardness of the samples. Microhardness was determined by indentation on a “Micron-gamma” unit at room temperature under loading to F = 2 N using the Berkovych diamond pyramid (σ = 65^о). The accuracy of the force F determination was 10^-3 N; the depth of indentation was ±2,5 nm. The increase in the microhardness of samples from H_v = 11,7 tо 34,0 GPa was established to be related to the formation of a microdomain substructure in particles due to the evolution of layer-by-layer crystal-oriented transformation of the wurtzite phase into multilayered polytypes and twinned sphalerite boron nitride. The samples containing ~10—15% sphalerite phase exhibited the highest microhardness. Full text download