A lanthanum monazite coated silicon carbide fiber reinforced SiBCN composite with improved mechanical properties for high temperature applications

Abstract

A novel lanthanum monazite (LaPO₄) coating was applied to silicon carbide fiber using a simple hydrothermal method to afford a SiC_f/LaPO₄/SiBCN composite that could be fabricated using resin transfer molding & polymer impregnation and pyrolysis processing technologies. Microstructural analysis showed that silicon carbide fibers were coated uniformly with a ∼700 nm layer of LaPO₄, with X-ray diffraction results confirming that the coating formed in the deposition process were compatible with the fiber and matrix materials produced during the pyrolysis process. The mechanical properties of the resultant SiC_f/SiBCN, SiC_f/BN/SiBCN, SiC_f/LaPO₄/SiBCN composites were compared using bending, tensile strength, fracture toughness and oxidation tests. These tests indicate that the SiC_f/LaPO₄/SiBCN composite exhibits excellent mechanical properties, with tests at evaluated temperatures (1350°C for 50 h) revealing that the LaPO₄ coating does not undergo oxidation. These results indicate that the SiC_f/LaPO₄/SiBCN composite has good thermal properties for high temperature applications.