原位合成MoSi_2-SiC复合材料在500℃的氧化行为  

OXIDATION BEHAVIOR OF IN SITU SYNTHESIZED MoSi_2-SiC COMPOSITES AT 500℃

作　　者：张来启[1] 潘昆明[1] 段立辉[1] 林均品[1] 

机构地区：[1]北京科技大学新金属材料国家重点实验室,北京100083

出　　处：《金属学报》2013年第11期1303-1310,共8页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目50871012;国家重点基础研究发展计划项目2011CB605502资助~~

摘　　要：研究了不同SiC体积分数原位合成MoSi_2-SiC复合材料在500℃的氧化行为.经1000h氧化的结果表明:复合材料的氧化抗力明显好于单一MoSi_2,原位合成复合材料的氧化抗力好于传统的热压商用MoSi_2粉末和SiC粉末混合物制备的复合材料(外加复合材料),复合材料氧化1000h后未发生pest现象.其氧化动力学曲线分为:孕育期、快速氧化期和稳态氧化3个阶段.氧化膜的相组成为MoO_3,非晶SiO_2和β-SiC,材料的氧化过程主要是O_2与MoSi_2的作用,SiC未发生氧化.氧化5,10和20h后样品表面形貌观察结果表明:材料的氧化优先在相界处发生,初生氧化物以无定形态存在;随着氧化的进行,逐渐形成MoO_3晶须和非晶SiO_2为主的团絮状氧化物;MoO_3晶须优先在表面凸凹不平处形核并长大.The oxidation behavior for in situ synthesized MoSi2-SiC composites with different SiC volume fraction at 500℃ was investigated. The results of oxidation for 1000 h indicate that the oxidation resistance for composites is significantly higher than that of monolithic MoSi2, MoSi2-30%SiC composite in situ synthesized possesses higher oxidation resistance compared with the traditional composite which is fabricated by hot-pressing the mixture of commercial powders of MoSi2 and SiC. After oxidation for 1000 h, the composites have not been observed to disintegrate （pest）. The oxidation kinetics curves are divided into three stages： incubation period, rapid oxidation period and the steady-state. The oxide scale consists of MoO3, amorphous silica and β-SiC, therefore, the oxidation of the materials is mainly done between MoSi2 and O2, and SiC is not oxidized. The surface morphology observations of samples oxidized for 5, 10 and 20 h show that the phase boundary is the preferential oxidation site, the oxides formed at the initial stage of oxidation are irregular-shaped, and MoO3 whisker and oxide cluster mainly composed of amorphous SiO2 come gradually into being along with the development of oxidization. It is also found that the nucleation and growth of MoO3 whisker preferentially take place at the concave and convex sites of substrate surfaces.

关 键 词：原位合成 MOSI2-SIC复合材料 低温氧化行为 pest现象 

分 类 号：TB333[一般工业技术—材料科学与工程]