Tailored composites for superior ablation resistance at 3000 °C

Ultra-high temperature ceramics (UHTCs) with superior ablation resistance play a critical role in fulfilling mankind’s aspirations for elevated hypersonic speeds in aerospace. However, few materials satisfy the demands of such extreme environment, mostly due to their intrinsic brittleness and poor thermal shock resistance.

In a new study published in Advanced Powder Materials, a team of researchers at the National University of Defense Technology and Central South University in Changsha, China, reported an advanced ablation-resistant C_sf/HfC_0.76N_0.24 composite that can withstand a temperature of 3000 °C for 900 seconds marking the first report of such system for prolonged ablation resistance at elevated temperatures.

“The ablation resistance of this composite is over 14 times greater than that of HfC at 3000 °C, indicating significant practical potential for long-term thermal stability and oxidation resistance under ultra-high temperatures,” says lead author Zheng Peng.

To better understand the oxidation and ablation process, experimental results are integrated with Density Functional Theory (DFT) calculations to elucidate the underlying mechanisms of ablation behaviors.

“The mechanistic details of the complex oxidation processes are elucidated for the first time in terms of chemical bonding and cluster evolution, along with their relationship to cooperative oxygen atoms,” shares Peng. “Notably, nitrogen does not directly generate gas and escape at the initial stage; rather, it interacts with hafnium atoms to form ablation-resistant layer with large Hf-C-N-O networks.”

The melting point of this oxide is significantly higher than that of HfO₂, preventing it from melting into a liquid state at ablation temperatures exceeding the melting point of hafnium oxide, that increases the viscosity of the oxidation layer. The formation of a dense layer with enhanced viscosity prevents erosion caused by high-speed airflow during the ablation process, as demonstrated in experimental results of improved ablation-resistant capabilities.

“The mechanism of ablation resistance relies on the regulation of the coordination structure of UHTCs at the atomic level, which will serve as a paradigm for inspiring and accelerating materials discovery in this field, as well as maximizing their potential applications in hypersonic aircraft and spacecraft vehicles,” says Peng.

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Contact the author: Sian Chen (chensian07@nudt.edu.cn)

Fuhua Cao(Caofuhua@csu.edu.cn)

Xiang Xiong(xiongx@csu.edu.cn)

1 Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, National University of Defense Technology, Changsha, P. R. China

2 School of Materials Science and Engineering, Central South University, Changsha, P. R. China

3 State Key Laboratory of Powder Metallurgy, Central South University, Changsha, P. R. China

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