Some features of the sintering behavior of pure and technical boron carbide

Abstract

1. At temperature below 1500°C specimens from pure and technical boron carbide powders experience no shrinkage. An investigation into the variation of the strength and electrical conductivity of specimens has shown that sintering in this temperature range is due to processes of surface self-diffusion. 2. At temperatures above 1800°C an important part in the sintering process is played by the mechanism of mass transport through the vapor phase. This conclusion is arrived at on the basis of data yielded by measurements of the strength properties of specimens sintered under different partial vapor pressures. 3. Diffusion-controlled densification processes take place at temperatures above 2000°C in pure boron carbide and above 1500° C in technical boron carbide. The active behavior of technical boron carbide may be ascribed to its reaction with the impurities present in it and to the formation of a liquid phase at its grain boundaries. These phenomena promote densification by the mechanism of activated sliding and lead to the appearance of structural defects activating diffusion processes.