Phase identification in reactively sintered molybdenum disilicide composites

The objective of this research was to identify and quantify the phases form ed in reactively sintered MoSi2 and MoSi2 composites made from carbon coate d MoSi2 powders. The purpose of adding carbon was to form silicon carbide p articles (SICp) in situ and reduce the inherent presence of SiO2 in MoSi2. The carbon additions were made via polymeric coatings on MoSi2 particles by two processes, Phenolic Resin Based Carbon by Solvent Evaporation (PRBCSE) and Aqueous Dispersion Flocculation (ADF). The sintering temperatures and times ranged from 1600 to 1800 degrees C, and from 1 to 100 h, respectively . The addition of carbon did reduce the presence of SiO2 and there was form ation of SiCp. However, the SiCp formation was less than expected, a maximu m of 1.4 vol.% SiCp was formed. The Nowotny phase (Moless than or equal to 4.8Si3Cless than or equal to 0.6) was observed in the sintered samples. The in situ formation of SiCp would increase the toughness of MoSi2 by serving as a reinforcement. The reduction in the amount of SiO2 would reduce the i ncidence of grain boundary sliding caused by viscous flow of SiO2 at elevat ed temperatures. (C) 1999 Elsevier Science S.A. All rights reserved.