Anisotropic and hierarchical SiC@SiO2 nanowire aerogel with exceptional stiffness and stability for thermal superinsulation.

TL;DR: A SiC@SiO2 nanowire aerogel with a nanowires-assembled anisotropic and hierarchical microstructure was prepared by using directional freeze casting and subsequent heat treatment to realize thermal superinsulation and high stiffness of ceramic aerogels.

Abstract: Ceramic aerogels are promising lightweight and high-efficient thermal insulators for applications in buildings, industry, and aerospace vehicles but are usually limited by their brittleness and structural collapse at high temperatures In recent years, fabricating nanostructure-based ultralight materials has been proved to be an effective way to realize the resilience of ceramic aerogels However, the randomly distributed macroscale pores in these architectures usually lead to low stiffness and reduced thermal insulation performance Here, to overcome these obstacles, a SiC@SiO2 nanowire aerogel with a nanowire-assembled anisotropic and hierarchical microstructure was prepared by using directional freeze casting and subsequent heat treatment The aerogel exhibits an ultralow thermal conductivity of ~14 mW/m·K, an exceptional high stiffness (a specific modulus of ~247 kN·m/kg), and excellent thermal and chemical stabilities even under heating at 1200°C by a butane blow torch, which makes it an ideal thermally superinsulating material for applications under extreme conditions