无压烧结碳化硅在高温熔融Na_(2)SO_(4)中的腐蚀行为

Corrosion Behavior of Pressureless-sintered Silicon Carbide in High-temperature Molten Na_(2)SO_(4)

将无压烧结碳化硅(SiC)样品放入氩气(Ar)气氛中,于900℃-1000℃的熔融硫酸钠环境中进行浸泡实验。通过扫描电子显微镜(SEM)、能量色散X射线光谱(EDS)、X射线衍射(XRD)及拉曼光谱等测试对样品的显微结构与成分演变进行了分析。实验显示,样品发生了严重的溶解,尤其是在碳(C)富集的晶界处发生了晶间腐蚀,导致晶粒从基体上脱落。样品的失重随着浸泡时间呈线性增加。在900℃条件下浸泡8 h后,样品失重量达到了31%。温度升高至1000℃后,样品浸泡4 h后的失重量达到了95%。通过对腐蚀及其机制进行分析,结果发现,样品的腐蚀机制主要是表面缺少具有保护性的氧化层以及游离碳容易富集的晶界处发生优先腐蚀从而导致晶粒脱落。

Corrosion behavior of pressureless-sintered SiC plates was studied by immersing in molten sodium sulfate(Na_(2)SO_(4))in Ar at 900℃ and 1000℃.Microstructural and compositional evolutions were examined by using scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(XPS),X-ray diffraction(XRD)and Raman spectroscopy.Dissolving corrosion was observed.Particularly,intergranular corrosion along grain boundaries with enriched C was confirmed,which induced peeling off of grains.The weight loss increased linearly with the immersion time.The SiC was dissolved by~31%after immersion for 8 h at 900℃ and~95%after immersion for 4 h at 1000℃ in the molten Na_(2)SO_(4).The corrosion mechanism was discussed.It was revealed that the corrosion mechanism was attributed to the absence of the protective Si-O layer and the preferential corrosion of the C-rich areas that caused massive grains falling out from the matrix.