The Influence of SiO2 + SiC + Al (H2PO4)3 Coating on Mechanical and Dielectric Properties for SiCf/MWCNTS/AlPO4 Composites

SiC fiber-reinforced AlPO4 matrix (SiCf/MWCNTs/AlPO4) composites were fabricated using a hot laminating process with multi-walled carbon nanotubes (MWCNTs) as the absorber. A coating prepared from SiO2 + SiC + Al (H2PO4)(3) was applied to the surface of the SiCf/MWCNTs/AlPO4 composites prior to an anti-oxidation test at 1273 K in air for 40 h. The anti-oxidation effect was verified by a three-point bending test, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and a dielectric property test. Anti-oxidation mechanism investigations revealed that the coating effectiveness could be attributed to three substances, i.e., SiO2, SiP2O7, and SiO2 + AlPO4 solid solution from the reactions of SiC + O-2 -> SiO2 + CO, SiO2 + P2O5 -> SiP2O7 and SiO2 + AlPO4 -> solid solution, respectively.