MgO/Si3N4复合材料表面致密层的形成机理

研究发现MgO/Si3N4复合材料具有自阻碍氧化的性能,氧化时其表面能自发生成一层阻碍进一步氧化和提高抗侵蚀的致密层,添加Al,Si可以加厚、加宽致密层.在此基础上,研究了无添加剂和添加Al,Si的致密层的形成机理、组成和结构.提出转换氧分压为衡量气态氧化物SiO和Al2O的逸出标准,并确定气态的SiO或Al2O可以在氧化层内部生成以及由于它们在表面的再氧化和反应使表层内形成了致密层的机理.

Forming Mechanism of Compact Layer on the Surface of MgO/Si3N4 Composite

It was found that MgO/Si3N4 composite possesses a self-impedient performance to oxidation. A compact layer on the surface, which is an anti-oxidation and anti-corrosion layer, formed spontaneously in MgO/ Si3N4 composite in the process of oxidation, and the thickness and density of the compact layer increased by adding Si or Al into the composite. On the basis of the results, the forming mechanism, the composition and structure of the compact layer of the composites with or without Si or Al were studied. The transform oxygen partial pressure was proposed as a standard for evaluating the escape intensity of gaseous SiO and A12O. It will show using the thermodynamics and the standard that gaseous SiO and A12O can produce inside the composite and they reoxidize and react with other oxides in the outside layer to form the compact layer.