Preparation and oxidation behavior of a double-layer coating for three-dimensional braided carbon fiber

Double-layer coatings, with Pyrolytic carbon (PyC) as inner layer and SiC/SiO2 as outer layer by a precursor infiltration and pyrolysis (PIP) process, were prepared on the surface of three-dimensional (3-D) braided carbon fiber. The double-layer coatings (PyC-SiC/SiO2) were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The microstructure, tensile strength and the oxidation resistant properties of the carbon fiber with and without coating were studied. Result showed that the best coating quality obtained was use of 10 wt% polycarbosilane (PCS) with 5 wt% methyltriethoxysilane (MTES) precursor in divinylbenzene (DVB) pyrolyzed to 1400 °C for 2 immension–pyrolysis cycles. The oxidation resistance of carbon fibers was improved obviously by the PyC-SiC/SiO2 coatings. Tensile strength measurement revealed that the PyC-SiC/SiO2 coated carbon fiber maintained 87.7% of its original strength.