Abstract: The ultra-lightweight and multifunction integrated thermal protection materials are critical for the development of hypersonic vehicles. Although various materials have been developed as potential thermal protection materials, most of them generally present a singular function. It is still challenging to meet the multifunctional requirements of ultra-lightweight, thermal insulation, electromagnetic interference (EMI) shielding, and high-temperature ablation resistance. Herein, a gradient C_f/(CrZrHfNbTa)C-SiC composite is designed and fabricated based on the bionic strategy of capillary adsorption and transport. The developed gradient C_f/(CrZrHfNbTa)C-SiC composite is as light as 0.74 g/cm³, which shows excellent ablation resistance (-3.88 μm/s at 2000 °C). It also presents competitive thermal insulation performance with a back temperature below 152 °C while enduring 1300 °C on the front side. The thermal conductivity of the gradient composite is 0.202 W m^-1 K^-1. Furthermore, the gradient C_f/(CrZrHfNbTa)C-SiC composite offers remarkable EMI shielding performance with mean total EMI shielding efficiency (SE_T) larger than 45 dB in an ultra-wide frequency range of 0-100 GHz. The excellent multifunctional performance with ultra-lightweight makes the gradient C_f/(CrZrHfNbTa)C-SiC composite ideal thermal protection materials for hypersonic vehicles. This work provides a flexible strategy for constructing gradient composites for multifunctional applications.

Key words: Multifunction integration, Bionic strategy, Gradient composite