Fiber-reinforced ceramic matrix composites (CMCs) have been the primary choice for radome materials in hypersonic vehicles due to their high toughness, strength, and other advantageous properties. However, oxidation by oxygen in the atmospheric environment at elevated temperatures remains a significant obstacle to their further development. Thermal protection coatings offer a crucial avenue to mitigate this issue. Nonetheless, inherent material differences or fiber orientations within CMCs can lead to disparate thermal expansion rates between the matrix and fibers during temperature variations, inevitably generating internal stresses. These internal stresses, ironically, contribute to the cracking and even detachment of coatings, posing a challenge to their effectiveness.
"The way of the Tao moves through opposition; its function is found in what is weak." Inspired by the wisdom of ancient philosophers, Professor Xia Long from the Key Laboratory of Special Ceramic Design and Preparation at Harbin Institute of Technology (Weihai) has proposed a conceptual framework rooted in reverse thinking to address this issue, attempting to achieve a higher "return" through a minimal "sacrifice." Recognizing the inherent difficulty in preventing coating cracks, the team suggests harnessing oxidation at the crack sites, where the resulting oxide products can chemically or physically interact with the oxidation-resistant coating to reduce material viscosity. This targeted self-healing of thermally mismatched cracks is named the "Dual-feedback self-healing mechanism."
The team published their work in Journal of Advanced Ceramics on September 5, 2024.
