Microstructure of nano and micron size diamond-SIC composites sintered under high pressure high temperature conditions

Abstract

Compacts and composites were sintered under high pressure (2 GPa - 10 GPa) and high temperature (1400 - 2300 ? C) conditions. The compacts were sintered using nano-SiC powder, micron-diamond powder, and nano-diamond powder. Composites were sintered using the liquid infiltration method from nano-silicon powder and nano or micron diamond powder. Under the high pressure, high temperature conditions the silicon powder would melt and react with carbon from the diamonds to form a SiC matrix. The microstructure and strain of the composites and compacts was analyzed using X-ray diffraction analysis. The extended convolutional multiple whole profile fitting method was used to analyze the X-ray line profiles to determine average crystallite size, dislocation density, and planar fault probability. The apparent lattice parameter method was used to analyze strain. Below a certain pressure there was subgrain growth. However, at the higher pressures there was a reduction in crystallite size. In the SiC phase there was a correlation between predominate defect, dislocation or planar fault, and the crystallite size. The defect structure of the diamonds seemed to be dependent on the initial diamond powder used. At higher temperatures there was evidence of recovery and or recrystallization.