SHI Xiaoguang 1, 2, DAI Shuxin 1, 2, LI Bingsheng 3, LIU Haiyong 2, LI Peng 2, ZHOU Jie 2, HUANG Qing 2, MIN Yong´an 1, GE Fangfang 2
(1. School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China; 2. Engineering Laboratory of Advanced Energy Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Science,Ningbo 315201, Jiangsu, China; 3. State Key Laboratory for Environment-friendly Energy Materials,Southwest University of Science and Technology, Mianyang 621010, Sichuan, China)
Abstract: Corrosion behavior of pressureless-sintered SiC plates was studied by immersing in molten sodium sulfate (Na2SO4) in Ar at 900 °C and 1000 °C. 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 °C and ~95% after immersion for 4 h at 1000 °C in the molten Na2SO4. 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.
Key words: SiC; corrosion; grain boundaries