Anisotropic and hierarchical SiC@SiO ₂ nanowire aerogel with exceptional stiffness and stability for thermal superinsulation

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 ~24.7 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.

Recent advances in novel aerogels through the hybrid aggregation of inorganic nanomaterials and polymeric fibers for thermal insulation

“…To solve this problem, researchers employed flexible fibers to construct aerogels to enhance the mechanical properties. [ 90–97 ]…”

“…This fusion and anisotropic microstructure of nanowires lead to high compression resilience. [ 96 ] Furthermore, the inorganic sol nanoparticles can also act as crosslinkers, forming a stable crosslinking structure between the nanofibers and nanoparticles. Dou et al.…”

“…Introducing fiber into inorganic aerogels: (A) inorganic nanofiber reinforce inorganic aerogel (reprinted with permission [ 96 ] ); (B) directional freeze drying method provide oriented structure (reprinted with permission [ 93 ] ); (C) organic nanofiber reinforce inorganic aerogel (reprinted with permission [ 94 ] )…”

Programmable Local Orientation of Micropores by Mold‐Assisted Ice Templating

“…Porous materials, such as wood and bones, widely exist in nature and have attracted great attention due to their low density, high specific strength, large specific surface area, and good mass permeability. [ 1 ] Hence, porous materials can be used for light‐weight materials, [ 2 ] energy, [ 3 ] material separation, [ 4 ] safety protection, [ 5 ] and tissue engineering. [ 6 ] To prepare porous materials, various methods have been developed, including direct synthesis, [ 7 ] phase separation, [ 8 ] templating, [ 9 ] foaming, [ 10 ] and 3D printing.…”

Fabrication and application of macroscopic nanowire aerogels

“…24 This seminal work has inspired the development of a significant amount of nanowire aerogels including various ceramic, metal, metal oxide, metal phosphate nanowire aerogels. 26,38,40,41,[45][46][47][48][49] Different from the typical application of macroscopic-scale 2D assembled nanowires in thinfilm based electronic devices such as transistors, sensors and photodetectors, [50][51][52] the intrinsic properties of anisotropic nanowire building blocks combined with the structural characteristics of aerogels have promoted wide application of aerogels in many emerging fields including thermal insulator, 53 energy storage and conversion, 54 catalysis, 27 pollutants removal, 55 pressure sensor, 37 and solar steam generation. 56 As a matter of fact, the literature regarding nanowire aerogels is growing rapidly.…”