碳纤维增强Si-C-N陶瓷基复合材料的氧化行为

OXIDATION BEHAVIOR OF CARBON FIBER REINFORCED Si-C-N MATRIX COMPOSITE

采用化学气相浸渗(chemical vapor infiltration,CVI)法制备了以热解碳为界面的碳纤维增强碳氮化硅陶瓷基(carbon fiber reinforced silicon carbonitride ceramic,C/Si-C-N)复合材料。用热重法研究了无涂层C/Si-C-N在空气环境中的氧化行为。研究表明:由950℃CVI沉积的Si-C-N基体所制备的C/Si-C-N复合材料的氧化行为与碳纤维增强SiC陶瓷基(carbon fiber reinforced silicon carbide ceramic,C/SiC)复合材料的完全不同。在600～1200℃,C/Si-C-N的氧化速率随温度的升高而持续增加,其抗氧化能力在600℃明显高于C/SiC复合材料;在900℃,抗氧化能力与C/SiC复合材料基本相当;在1200℃,抗氧化能力则低于C/SiC复合材料。C/Si-C-N复合材料所表现出来的氧化行为主要与Si-C-N基体较低的热膨胀系数有关。

Carbon fiber reinforced silicon carbonitride matrix composite （C/SiC-N） with a pyrolytic carbon interlayer was fabricated by a chemical vapor infiltration （CVI） technique. The Si-C-N matrix was deposited by CVI at 950 ℃. The oxidation behaviors of C/Si-C-N were investigated in air using thermogravimetry. The results indicate that the oxidation behavior of C/Si-C-N is completely different from that of carbon fiber reinforced SiC composite （C/SiC）. The oxidation rate of C/Si-C-N increases continuously with the increase of temperature from 600 to 1 200℃. The oxidation resistance of C/Si-C-N is similar to that of C/SiC at 900℃, obviously higher than that of C/SiC at 600 ℃, and is lower than that of C/SiC at 1 200℃. These oxidation behaviors are mainly related to the low coefficient of thermal expansion of the Si-C-N matrix.