Growth mechanism and structure regulation of super-elastic SiC aerogels for thermal insulation and electromagnetic wave absorption

Abstract

High-performance silicon carbide (SiC) aerogels with excellent high-temperature resistance and high porosity are highly desirable in the fields of thermal insulation and adsorption. However, constructing a super-elastic SiC aerogel and controlling its properties is still a significant challenge. To better regulate its properties, it is necessary to clarify its reaction and growth mechanism. Here, we propose an in-situ reactive growth strategy to prepare super-elastic SiC aerogels. The obtained aerogels can withstand 80 % deformation and exhibit an ultra-low thermal conductivity of 0.024 W·m−1 K−1. Furthermore, the aerogel shows a superior electromagnetic wave (EMW) absorption performance with a minimum refection loss (RLmin) value of – 40.7 dB. More importantly, we reveal the mechanism of the reaction and growth of SiC crystal. The growth process of SiC crystal can be divided into three stages: pyrolysis, nucleation and growth. Based on understanding the growth mechanism, we can further regulate the structures of SiC crystals by controlling the sintering time, including sea urchin-like, nanorod-like, nanowire-like and slub-like shapes. This study provides a new idea for preparing super-elastic SiC aerogel and regulating its structure.