Fabrication, microstructure, and mechanical properties of TaC particulate and SiC fiber-reinforced lithia-alumina-silica composites

Additions of O to 9 mol % Ta₂O₅ to a lithia-alumina-silica glass-ceramic matrix Nicalon SiC-reinforced composite increased the elastic modulus and ultimate strength of the composite. The additive fostered sphereulitic growth of β-eucriptite solid solution crystals which concentrated Ta₂O₅ at sphereulite boundaries and adjacent to the fiber-matrix carbon-rich interphases. These regions reacted with the interphases as well as soluble carbon monoxide gas to convert them to TaC. The former reaction was shown to be thermodynamically favorable above 983 °C, while the latter was favorable above 1249 °C. The improvement in mechanical properties was attributed to TaC particulate reinforcement, and suggests a simple glass-ceramic route to the fabrication of particulate-reinforced ceramic matrix composites.