晶型及化学成分对SiC粉体氧化性能的影响

Influence of Crystalline Forms and Chemical Composition on Oxidation Performance of SiC Powders

研究粒度标号为W2.5和W10、晶型为3C和6H的3C-W2.5、3CW10、6H-W2.5、6H-W10这4种SiC粉体的氧化性能,通过同步热分析仪讨论4种粉体在30~1 400℃时的非等温氧化特性,采用X射线衍射和扫描电子显微镜对氧化前、后粉体的物相和表面性质进行表征。结果表明：起始氧化温度从高到低的SiC粉体依次为3C-W10、6H-W2.5、6H-W10、3CW2.5,与其化学成分中SiO2相对含量由大到小的关系相一致;在相同实验条件下,高温氧化后同一晶型的粉体粒度标号为W2.5的质量变化大于W10的,粒度相同时,3C-SiC的质量变化小于6H-SiC的;加热至1 400℃后,SiC晶体表面有玻璃状SiO2生成。

Oxidation performance of SiC powders such as 3C-W2.5、3CW10、6H-W2.5、6H-W10 with particles size grades of W2.5 and W10 as well as crystalline forms of 3C and 6H was researched. Non-isothermal oxidation behaviors of four kinds of powders were analyzed via simultaneous thermal analyzer at temperature from 30 to 1 400 ℃. Morphology and surface properties of powders before and after oxidization were investigated by XRD and SEM. The results show that the SiC powders with initial oxidation temperature in descending order are 3C-W10, 6H-W2.5, 6H-W10 and 3CW2.5, consistent with the relative content of SiO2 from large to small in their chemical composition. Under the same experimental conditions, mass change of W10 powders is greater than that of W2.5 powders after oxidation with an identical crystal form, and mass change of 3C-SiC is smaller than that of 6H-SiC with an identical particle size. Glassy SiO2 is found on the surface of SiC crystal after heating to 1 400 ℃.