Ultralight SiC nanowire aerogels with exceptional thermal stability enabled by diffusion-controlled microstructure engineering

초록

Uniform formation of three-dimensional SiC nanowire (SiC NW) aerogels remains challenging because ceramic conversion in bulk architectures is often constrained by limited vapor diffusion. Here, controlled microstructural design of polyimide-derived carbon aerogels is shown to regulate vapor transport during carbothermic reactions, enabling systematic examination of how internal architecture influences nanowire nucleation and conversion depth. Open, low-density scaffolds allow homogeneous vapor penetration throughout the bulk, leading to continuous and fully interconnected SiC NW networks, whereas denser architectures restrict diffusion and confine SiC formation to surface regions. As a result, the optimized SiC NW aerogel exhibits an ultralow density of 0.023 g cm(-3), high porosity (similar to 98%), and a low thermal conductivity of 0.046 W m(-1) K-1. The material further shows excellent thermal and oxidative stability, maintaining a temperature gradient exceeding 800 degrees C under prolonged direct flame exposure (>1000 degrees C). These findings indicate that microstructure-guided control of diffusion offers a broadly applicable route for designing ceramic nanowire aerogels for extreme thermal insulation.

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