Carbon nanotube reinforced pyrocarbon matrix composites with high coefficient of thermal expansion for self-adapting ultra-high-temperature ceramic coatings

The mismatch in the coefficients of thermal expansion (CTE) of the carbon fiber reinforced pyrocarbon (Cf/C) composites and their thermal barrier coatings (TBCs) has significantly restricted the service life of Cf/C composites in high-temperature environments. Owing to the high CTE of TBCs, it is vital to find a material with similar mechanical properties and higher CTE than Cf/C composites. In this work, carbon nanotube reinforced pyrocarbon (Ct/C) nanocomposites with high CTEs were prepared to self-adapt to the TBCs. Different CTEs (similar to 4.0-6.5 x 10(-6)/degrees C) were obtained by varying the carbon nanotube (CNT) content of the Ct/C composites. Owing to the decreased mismatch in the CTEs, no cracks were formed in the TBCs (SiC and HfB2-SiC-HfC coatings) deposited on the Ct/C composites. After heat treatment at 2100 degrees C, several wide cracks were found in the TBCs on the Cf/C composite, whereas the TBCs on the Ct/C composites were intact without cracks. We found that the CTE-tunable Ct/C composites can self-adapt to different TBCs, protecting the composites from oxidation at high temperatures.