Microstructural regulation,oxidation resistance,and mechanical properties of Cf/SiC/SiHfBOC composites prepared by chemical vapor infiltration with precursor infiltration pyrolysis

To further improve the oxidation resistance of polymer derived ceramic (PDC) composites in harsh environments,Cf/SiC/SiHfBOC composites were prepared by chemical vapor infiltration(CVI) and precursor impregnation pyrolysis (PIP) methods.The weight retention change,mechanical properties,and microstructure of Cf/SiC/SiHfBOC before and after oxidation in air were studied in details.Microscopic analyses showed that only the interface between the ceramics and fibers was oxidized to some extent,and hafnium had been enriched on the composite surface after oxidizing at different temperature.The main oxidation products of Cf/SiC/SiHfBOC composites were HfO2and HfSiO4after oxidation at 1500℃for 60 min.Moreover,the weight retention ratio and compressive strength of the Cf/SiC/SiHfBOC composites are 83.97%and 23.88±3.11 MPa,respectively.It indicates that the Cf/SiC/SiHfBOC composites should be promising to be used for a short time in the oxidation environment at 1500℃.