Eggplant-derived SiC aerogels with high-performance electromagnetic wave absorption and thermal insulation properties

Abstract

Lightweight and strong silicon carbide (SiC) aerogels with a three-dimensional architecture and in situ grown SiC nanowires are obtained from natural eggplants by direct graphitization and subsequent carbothermal reduction. Effective synergism is achieved by decorating the SiC frameworks with one-dimensional SiC nanowires, which impart the aerogels with excellent electromagnetic (EM) wave absorption, thermal insulation, and mechanical properties. Highly porous, interconnected SiC networks facilitate the multiple reflection–absorption effects of infiltrated EM waves and extend the routes of heat transmission in the samples. SiC nanowires, which consist of numerous stacking faults and heterojunctions, play key roles in dissipating EM energy, obstructing heat transfer, and reinforcing the SiC skeleton. Given their 97.6% porosity, the SiC aerogels show a minimum reflection of −43 dB and effective bandwidth of 4 GHz at 2 mm thickness. The in situ grown SiC nanowires substantially increase the compressive stress of the SiC aerogels to 2.12 MPa, which is nearly 50-fold than that of carbon aerogels derived from eggplants. Moreover, the SiC aerogels show a very low thermal conductivity of 0.035 W/m·K. These results indicate that the developed SiC aerogels are outstanding materials with potential applications in high-performance EM absorption and thermal insulation in the aviation and aerospace fields.