An Investigation of Environment Barrier Coating on 2D C/SiC Composites Prepared by Liquid Phase Process

Sc ₂Si ₂O ₇-based environmental barrier coating (EBC) was prepared on 2D C/SiC composites by different liquid phase processes. Single Sc ₂Si ₂O ₇ coating was brushed with sol and slurry. The multi-layer coating, which consisted of BSAS (Ba _{0. 25}Sr _{0. 75}Al ₂Si ₂O ₈, B) as bond coat, BSAS + Sc ₂Si ₂O ₇ (BS) as interlayer and Sc ₂Si ₂O ₇ (S) as top coat, was painted with slurry and modified slurry. The slurry process was modified using amorphous instead of crystallized powders as raw materials derived from the sol-gel method. Modification mechanisms were proposed and characterized by weight losses of BSAS and Sc ₂Si ₂O ₇ dry gel from thermogravimetric analysis and their sintering shrinkage ratios from coefficient of thermal expansion tests. The microstructure of the prepared coating was observed using scanning electron microscopy. The phase composition was detected by X-ray diffraction. The results showed that the S/BS/B coating with 30 μm thickness, which was prepared by the modified slurry, possessed excellent adhesion to the substrate and the best compactness among the above coatings. Higher activity, lower sintering energy barrier and tiny sintering shrinkage of S and B amorphous powders are mainly responsible for the performance enhancement.