Fabrication and Mechanical Properties of In-Situ Monazite-Coated Alumina Fiber-Reinforced Alumina/YAG Composites

摘要

Monazite(LaPO_4)-coated alumina-fiber/alumina-YAG (Y_3Al_5O_(12)) matrix composites were fabricated by in-situ coating of monazite followed by hot-pressing, and the effects of coating and sintering condition on mechanical properties of the composite were examined. Alumina powder and YAG powder (weight ratio, 95:5) were used as raw materials for green sheets, which was fabricated by tape casting technique. Monazite was synthesized by the in-situ reaction of La(NO_3) solution with H_3PO_4 on the surface of fibers. After slurry infiltration into the coated fiber bundles, the fiber cloths were laminated with the green sheets alternately, then they were heat-treated, finally sintered by hot-pressing at various temperatures. The mechanical properties of the composites were changed by the fabrication conditions. Non-brittleness of the composites reduced with the increase of sintering temperature. The composites sintered at 1200°C showed the highest Weibull modulus and pseudo-ductility.