Reaction and Its Suppression of B4C with Mullite.

Abstract

The reactivity of B4C with mullite was investigated under Ar and reductive atmospheres, respectively. The results indicated that B4C could coexist stably with mullite under Ar atmosphere below 1350°C, above which some reaction would occur to form Al2O3 and Al3SiB48 phases. Under a reductive atmosphere, whereas, they exhibited a relatively higher co-existing temperature of 1500°C, which is deemed to be dependent on the partial pressure of CO2 gas in heating atmosphere. Coating technique was employed in this study to suppress the reaction between B4C and mullite by producing a TiO2 thin coating layer on the surface of B4C particles. TiO2 will react with B4C at high temperature to produce TiB2 and B2O3. The latter phase, existing on the grain boundary of B4C particles by a liquid state at high temperature, will, together with TiB2, serve as a barrier to inhibit the reaction between B4C and mullite. A2mass% TiO2 on B4C powders can effectively suppress the occurrence of this reaction.