【摘要】 采用二次包埋法和水热电泳沉积法相结合的工艺在碳纤维增强碳复合材料表面制得SiC/方石英型磷酸铝(cristobalite aluminum phosphate,c-AlPO4)复合涂层。借助X射线衍射仪和扫描电镜对复合涂层的晶相组成和显微结构进行了表征。研究了复合涂层的高温氧化性能,讨论了复合涂层氧化、失效的机理。结果表明:复合涂层具有双层结构,包埋的SiC内层主要由α-SiC,β-SiC和少量的游离硅组成,外层由c-AlPO4颗粒构成,内外层结合紧密。复合涂层在1300～1500℃范围内具有良好的抗氧化性能,其氧化激活能为117.2kJ/mol,氧化过程主要受氧在c-AlPO4层中的体扩散速率所控制;氧化气体逸出留下的孔洞是复合涂层防氧化失效的主要原因。更多还原

【Abstract】 SiC/cristobalite aluminum phosphate (c-AlPO4) multi-layer coating was prepared on the surface of carbon fiber reinforced carbon (C/C) composites by using combining process of two-step pack cementation process and later hydrothermal electrophoretic deposition process.The phase composition and microstructure of the multi-layer coating were characterized by X-ray diffraction and scanning electron microscopy.The anti-oxidation property,oxidation mechanism and failure mechanism of the multi-layer coating were investigated.The results show that the SiC layer obtained from two-step pack cementation consists of α-SiC,β-SiC phases and a small quantity of free silicon,and the outer layer is composed of c-AlPO4 crystallites.Additionally,the multi-layer coating has good interface bonding between the two layers.The SiC/c-AlPO4 multi-layer coating exhibits an excellent oxidation resistance in air in the range of 1 300-1 500 ℃,and the oxidation activation energy of the coated C/C is calculated to be 117.2 kJ/mol.The oxidation process is predominantly controlled by outward diffusion of O2 through the c-AlPO4 coating.The failure of the multi-layer coating is a result of the generation of the microholes that may be left by the escape of the oxidation gases.更多还原