Si3N4颗粒及SiC晶须强韧化MoSi2复合材料的低温氧化行为

对Si₃N₄颗粒及SiC晶须强韧化MoSi₂复合材料在773K下的氧化行为进行了研究.通过热重量分析法（TG）分析了MoSi2及其复合材料MoSi₂-Si₃N_4(p)和MoSi₂-Si₃N_4(P)SiC_(w)在773K下的氧化性能, 采用SEM和X射线衍射测定其表面形貌和氧化物相组成.结果发现：在773K下, 纯MoSi₂和MoSi₂+20vol%Si₃N₄均发生了“Pesting”氧化, 氧化过程服从直线规律, 氧化产物层疏松, 氧化产物主要为MoO₃; MoSi₂+40vol%Si₃N₄氧化服从抛物线规律, 速率常数K_p为0.04mg²/(cm⁴·h), 氧化层致密, 成分主要为SiO₂、Si₂N₂O, 增加Si₃N₄的含量可显著提高MoSi₂的抗“Pesting”氧化能力; MoSi₂+20vol%Si₃N₄+20vol%SiC发生了严重的粉化现象, 氧化产物主要为短针状MoO₃.

Low Temperature Oxidation Behavior of MoSi2 Composites Strengthened and Toughened by Si3N4 Particles and SiC Whiskers

The oxidation behavior of MoSi₂ composites strengthened and toughened by Si₃N₄ particles and SiC whiskers was investigated. The oxidation performances of pure MoSi₂, MoSi₂-Si₃N_4(p) and MoSi₂+20vol%Si₃N₄+20vol%SiC at 773K were analyzed by thermo gravimetric analysis(TG). The surface micrograph and phases of the oxidation productions were analyzed using by SEM and X-ray. “Pesting” phenomena are observed in the pure MoSi₂ and MoSi₂+20vol%Si₃N₄ after oxidation, the relationship between gain weight and oxidation time is followed the straight-line law. The oxidation layer is loose and the main oxidation production is MoO₃. While the relationship between the gain weight and oxidation time is followed parabolic law during the oxidation of MoSi₂+40vol%Si₃N₄ and the oxidation rate is 0.04mg²/(cm⁴·h). The oxidation layer is dense and the main oxidation productions are SiO₂ and Si₂N₂O. So the resistance to “Pesting” oxidation will increase with the content of Si₃N₄ increasing. There happens serious “Pesting” in the MoSi₂+20vol%Si₃N₄+20vol%SiC after oxidation and the main oxidation production is short acicular MoO₃.