Ceramic coating protects carbon materials in extreme temperatures

The aerospace industry has adopted carbon materials due to their strength, temperature stability, and lightweight characteristics. The use of these materials, however, are restricted by their oxidization and ablation at high temperatures. Many methods have been developed to create protective coatings for the carbon materials, but none have been able to produce a high-density coating with protection over a wide range of temperatures.

Building on their previous work developing a silicon-based coating with ultra long static oxidation protection performance, Yang et al. tested many methods for creating a ceramic coating before settling on a combined approach using a slurry method and gas-phase silicon evaporation.

“We have verified the controllability of coating components by combining slurry method with vapor phase silicon evaporation method, and the coating exhibits excellent wide temperature range protection effect from 1600 °C to 2300 °C,” said author Yan Jiang.

After testing the coating for 100 hours at 1600 °C, the researchers determined the high oxidation resistance of the coating was due to the hafnium tantalum silicon oxide (Hf-Ta-Si-O) multiphase oxide layer, which had a low oxygen diffusion rate and high temperature stability. Additional ablation tests at 2300 °C showed the formation of high-melting-point oxides, which protected the surface from mechanical scouring. The fluidity of the silicon and tantalum oxides also helped fill tiny pores and cracks, providing additional protection.

The researchers plan to continue developing coatings for a range of environments including ceramic coatings, high-entropy ceramic coatings, carbide composite boride ceramic coatings, and multi-layer coatings. They also hope to increase the temperature range protection up to 2500 °C.

Source: “Study on the thermocyclic protection performance of ultrahigh temperature ceramic SiC-Si-Hf(Ta)B₂ coating for static oxidation and ablation environments up to 2300 °C,” by Jiani Yang, Xiaoyang Guo, Yuan Tian, Yan Jiang, Na Wang, Journal of Vacuum Science and Technology: A (2025). The article can be accessed at https://doi.org/10.1116/6.0004561 .