Strength improvement and purification of Yb₂Si₂O₇-SiC nanocomposites by surface oxidation treatment

A two-step processing was developed to prepare Yb₂Si₂O₇-SiC nanocomposites. Yb₂Si₂O₇-Yb₂SiO₅-SiC composites were first fabricated by a solid state reaction/hot-pressing method. The composites were then annealed at 1250°C in air for 2 h to activate the oxidation of SiC, which effectively transformed the Yb₂SiO₅ into Yb₂Si₂O₇. The surface cracks purposely induced can be fully healed during the oxidation treatment. The treated composites have improved flexural strength compared to their pristine composites. As a result, the mechanism for crack-healing and silicate transformation have been proposed and discussed in detail.