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Bonding strength and thermal shock resistance of a novel bilayer ( c ‐AlPO 4 ‐SiC w ‐mullite)/SiC coated carbon fiber reinforced CMCs
Author(s) -
Chen Pengju,
Xiao Peng,
Li Zhuan,
Pan Ling,
Li Jinwei,
Liu Zeyan,
Pu Dongmei,
Li Yang
Publication year - 2020
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16697
Subject(s) - mullite , materials science , thermal shock , composite material , whiskers , coating , cristobalite , ceramic , quartz
Mullite coating, SiC whiskers toughened mullite coating (SiC w ‐mullite), and cristobalite aluminum phosphate ( c ‐AlPO 4 ) particle modified SiC w ‐mullite coating ( c ‐AlPO 4 ‐SiC w ‐mullite) were prepared on SiC coated C/SiC composites using a novel sol‐gel method combined with air spraying. Results show that molten SiO 2 formed by the oxidation of SiC whiskers and molten c ‐AlPO 4 improved the bonding strength between mullite outer coating and SiC–C/SiC composites due to their high‐temperature bonding properties. The bonding strength between mullite, SiC w ‐mullite, c ‐AlPO 4 ‐SiC w ‐mullite outer coatings and SiC–C/SiC composites were 2.41, 4.31, and 7.38 MPa, respectively. After 48 thermal cycles between 1773 K and room temperature, the weight loss of mullite/SiC coating coated C/SiC composites was up to 11.61%, while the weight losses of SiC w ‐mullite/SiC and c ‐AlPO 4 ‐SiC w ‐mullite/SiC coatings coated C/SiC composites were reduced to 7.40% and 5.12%, respectively. The addition of appropriate SiC whiskers can considerably improve the thermal shock resistance of mullite coating owing to their excellent mechanical properties at high temperature. In addition, c ‐AlPO 4 particles can further improve the thermal shock resistance of SiC w ‐mullite coating due to their high‐temperature bonding and sealing properties. No obvious micro‐pores and cracks were observed on the surface of c ‐AlPO 4 ‐SiC w ‐mullite coating after 48 thermal cycles due to timely healing effect by formation of secondary mullite.