SiC/PyC复合涂层碳纤维微观结构及氧化行为研究

Microstructure and Oxidation Behavior of the SiC/PyC Multilayer Coated Carbon Fibers

采用两步法在碳纤维表面制备了碳化硅/热解碳(SiC/PyC)复合涂层,PyC内涂层的制备采用等温化学气相渗透法,SiC外涂层的制备采用碳热还原法.借助X射线衍射、场发射扫描电镜、透射电镜分析了SiC/PyC复合涂层碳纤维的物相组成以及微观结构,利用热重分析研究了SiC/PyC复合涂层、PyC涂层以及无涂层碳纤维的氧化行为.结果表明,在碳纤维表面制备的SiC/PyC复合涂层连续致密、厚度均匀,PyC内涂层厚度约为200nm,SiC外涂层厚度约为160nm,SiC层中存在大量孪晶面高度有序的SiC孪晶.SiC/PyC复合涂层能够有效地改善碳纤维的抗氧化性能,较无涂层碳纤维起始氧化温度提高了近250℃.

SiC/PyC coated carbon fibers were prepared by two-steps method. The PyC inner layer was prepared by isothermal chemical vapor infiltration and the SiC outer layer was synthesized by the carbothermalreduction. The mierostructures of the as-prepared SiC/PyC coated carbon fibers were characterized by XRD, FESEM and TEM. The oxidation behavior of the uncoated, PyC coated, and SiC/PyC coated carbon fibers were studied by the thermal-gravity analysis. The results show that the SiC and PyC layer deposited on carbon fibers are continuous and uniform. The thickness of PyC inner layer is about 200nm, and thickness of the SiC outer layer is about 160nm. High order twin boundaries are observed in the SiC layer. The oxidation resistance of the carbon fiber can be improved by the SiC/PyC muhilayer coating. The initial oxidation temperature of the SiC/PyC coated carbon fiber is about 250℃ higher than that of uncoated carbon fiber.