炭纤维表面SiC/SiO_2抗氧化涂层的溶胶凝胶法制备

Preparation of an anti-oxidative SiC/SiO_2 coating on carbon fibers by a sol-gel method

采用溶胶凝胶法,并经高温热处理在炭纤维表面制备SiC/SiO2陶瓷涂层。通过X-射线光电子能谱、X-射线衍射、扫描电镜等分析SiC/SiO2涂层的结构与形貌。通过热重分析研究炭纤维涂层前后的抗氧化性能。结果表明,均匀、无裂纹的SiC/SiO2涂层可改善炭纤维的抗氧化性能,而且涂层炭纤维的抗氧化性能随着溶胶浓度和热处理温度的升高而增加。与原始炭纤维相比,具有300nm涂层厚度的炭纤维起始氧化温度提高了200℃。但是当涂层超过一定厚度时,涂层开裂脱落,炭纤维的抗氧化性能降低。SiC/SiO2涂层炭纤维的拉伸强度与原始纤维相比降低了37.7%,在700℃等温氧化90 min,涂层纤维的拉伸强度为1.37GPa,仍保留一定的强度。

A SiC/SiO2 ceramic coating on carbon fibers was prepared by a sol-gel method followed by heat treatment at high tem- perature. The structure and the morphology of the SiC/SiO2 coating were characterized by X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. The oxidation resistant properties of the carbon fibers with and without the coating were compared by thermogravimetric analysis. Results indicate that a uniform and continuous coating can improve the oxidation re- sistance of carbon fibers. The oxidation resistance of the coated carbon fibers increased with increases in the sol concentration and heat treatment temperature. A coating of thickness 300 nm increased the onset oxidation temperature by about 200 ℃ and the single fiber tensile strength was decreased by 37.7% compared with the pristine carbon fibers. After isothermal oxidation at 700 ℃ for 90 rain, the single fiber tensile strength of the coated carbon fibers was decreased to 1.37 GPa. The oxidation resistance of the fibers was decreased when the coating thickness exceeded 400 nm duc to the spallation of the coating.