Effects of LaPO₄ Coating on Properties of Carbon Fiber Reinforced SiBCN Ceramic Matrix Composites

Abstract

A novel lanthanum monazite (LaPO4) coating was applied on two-dimensional woven continuous carbon fibers by a simple hydrothermal method. Then a Cf/LaPO4/SiBCN ceramic matrix composite(CMCs) was fabricated via subsequent RTM (resin transfer moulding) & PIP (polymer impregnation and pyrolysis) technology. Microstructure observation shows that most of the carbon fibers are coated uniformly with a layer of lanthanum monazite with the thickness of 500nm and there is no obvious chemical contamination between the coating and fiber/matrix during high temperature pyrolysis process. Cf/SiBCN, Cf/PyC/SiBCN and Cf/BN/SiBCN composites were also made to be compared with Cf/LaPO4/SiBCN composites in three-point bending test, fracture toughness test and oxidation test. The results show that Cf/LaPO4/SiBCN composites obtain at least 30% improvement in fracture toughness; in 1350℃/50h oxidation test, Cf/LaPO4/SiBCN composites have the lowest mass loss and the fibers are protected effectively by the coatings, demonstrating the significant increasing in oxidation resistance. Overall, compared with other mentioned coatings, the lanthanum monazite coating enhances much more the high temperature performance of the carbon fiber reinforced SiBCN ceramic matrix composites and promotes the high temperature application potential of the composites.

Keywords

• LaPO₄
• carbon fiber
• SiBCN
• composite