热压烧结C-SiC-B_4C复合材料组织与性能(Ⅱ):氧化行为

以C鳞片,SiC,B4C和TiO2为原料,在2000℃热压合成C-SiC-B4C-TiB2复合材料.研究复合材料在600~1400℃静态空气中的恒温氧化行为,利用TG/DTA研究复合材料氧化机理,利用XRD,SEM研究复合材料恒温氧化后表面相组成和氧化层剖面的显微结构.结果表明不同C鳞片含量的复合材料的氧化动力学曲线均为抛物线,氧化层可分成氧化膜和过渡层,C鳞片质量分数为20%的复合材料在1400℃时有很好的抗氧化自还原能力,表面生成致密的氧化膜,氧化膜的成分为未形成玻璃态的TiO2或SiO2.TiO2固溶体,组织形貌为枝条状.

Microstructure and Properties of C-SiC-B4C Composites Prepared by Hot Pressing Sintering(Ⅱ): Oxidation Behavior

C-SiC-B4C-TiB2 composites were hot pressed at 2000°C with graphite flake, SiC, B4C and TiO2 as raw materials. The oxidation behavior of C-SiC-B4C-TiB2) composites in steady atmosphere at 600-1400°C was analyzed in view of isothermal oxidation with oxidation mechanism studied through TG/DTA thermal analysis, and XRD and SEM were used for the phase composition and cross-sectional morphology of oxide layer. The results showed that the oxidation kinetic curves of the composites are in form of parabola. No matter what content of graphite flake is the oxide layer comprises oxide film and transition layer. The composite with 20% graphite flake content has an excellent oxidation resistance with self-reduction properties at 1400°C and forms a compact oxide film which is composed of TiO2 or SiO2·TiO2 solid solution that has not become glass yet and its morphology shows dendritic structure.