Si-B-C陶瓷涂敷2D C/SiC复合材料的抗氧化性能

利用化学气相沉积(CVD)法制备了Si-B-C陶瓷涂敷改性的2D C/SiC复合材料, 研究了其在700～1200 ℃氧化10 h性能和结构的演变规律以及自愈合机制, 同时获得了Si-B-C涂层在不同温度氧化后的形貌、 组分和物相转变规律。结果表明: 涂敷在复合材料表面的Si-B-C陶瓷随温度的升高氧化加快, 但氧化程度较低, 不深于7 μm; 随温度的升高, 氧化形成的硅硼玻璃黏度降低, 挥发增强; 当温度达到1200 ℃时, 硅硼玻璃析出SiO₂晶体; Si-B-C陶瓷涂敷改性的C/SiC具有优良的抗氧化性能, 随氧化温度的升高, 复合材料失重率增加, 但在1200 ℃氧化10 h后失重率仅为0.47%; 此外材料在1000 ℃氧化后的强度保持率最高, 达到91.6%, Si-B-C陶瓷氧化形成的硅硼玻璃可以有效封填裂纹, 这是材料具有优良抗氧化性能的主要机制。

Oxidation resistance of two dimensional C/SiC composite coated with Si-B-C ceramic

Two dimensional C/SiC composite coated with Si-B-C ceramic was prepared via chemical vapor deposition (CVD). Properties and structure evolution and self-healing mechanisms of the C/SiC composite were studied after oxidation for 10 h during 700-1200 ℃. At the same time, the evolution of morphologies, composition and phase for Si-B-C ceramic were also investigated. The experimental results show that the oxidation of Si-B-C ceramic accelerates with the temperature increasing, however, the oxidation scale is shallow and no more than 7 μm. With the temperature increasing, viscosity of borosilicate glass oxidized from Si-B-C ceramic reduces but volatilization accelerates. When the temperature increases to 1200 ℃, SiO₂ crystallizes from borosilicate glass. C/SiC composite coated with Si-B-C ceramic shows an excellent oxidation resistance. Mass loss increases with temperature increasing, which is only 0.47% after oxidation for 10 h at 1200 ℃. Furthermore, the strength retention ratio is 91.6% at 1000 ℃, higher than that at other temperatures. The main mechanisms for excellent oxidation resistance of C/SiC composite is that borosilicate glass oxidized from Si-B-C ceramic can seal cracks in composite effectively.