In-Situ Raman Spectroscopy Investigation of Corrosion Behavior of SiC/SiCf Composite in High-temperature and High-pressure Water

Corrosion test and in-situ Raman spectroscopy measurement for SiC/SiCf composite were carried out using the established high temperature and high pressure circulating water corrosion test system, in-situ observation autoclave and Raman spectroscopy characterization system. The corrosion test environment was an aqueous solution containing 1 200 mg/L H₃BO₃ + 2 mg/L LiOH. Two series of corrosion experiments were conducted: in one experiment, the oxygen content in solution was not controlled (oxygen content ≈ 2 688 μg/L); in the other experiment, the oxygen content in solution was controlled (oxygen content≈5 μg/L). The results show that the Raman peaks were located near 500、590、715、785、805、870、915、960 cm^-1, corresponding to β-SiC matrix and its surface oxide films SiC_xO_y, SiO₂, Si(OH)₄ etc., respectively. In the oxygen-saturated solution, surface films were prone to become Si(OH)₄, which were not protective. In the oxygen-controlled solution, surface films were stable, and the transformation from SiO₂ to Si(OH)₄ were retarded. Therefore, the corrosion resistance of SiC/SiCf composite was improved.