SiC Nanowire Sponges as Electropressure Sensors

Lightweight, flexible, and highly porous ceramics are very attractive to engineering applications due to their good inertness, stability, and excellent mechanical properties. We here report such SiC nanowire (SiCNW) sponges and demonstrate their multifunctionalities. They were simply generated by reacting SiO2 with sustainable kitchen sugar, using NH4Cl as a blowing agent. The as-grown, highly porous SiCNW sponges exhibit a core–shell structure, with an extremely low density in the range of 115–125 mg/cm3 (against 3.21 g/cm3 for the bulk). The core part is comprised of short and tangled SiC whiskers with SiC flakes embedded, while the shell layer consists of numerous smooth SiCNWs of a hundred micrometers long. These sponges exhibit a compressive modulus of ∼1.35 MPa and recoverability under cyclic compression loading for 100 cycles at a strain of 20%. Meanwhile, the SiCNW sponges exhibit interesting electromechanical sensing capability with a gauge factor up to 87 and stable wide-range compression-resistance responses that are hundreds of times better than those of carbon-based composite sensors. Furthermore, the high porosity (96.1–96.4%) of the sponges gives rise to a very low thermal conductivity of merely 1.01 W/mK at room temperature, demonstrating their excellent thermal insulation potential. These lightweight, highly porous, thermally insulating features of the SiCNW sponges can be further exploited in electromechanical microdevices for monitoring structural damage or capturing impacts, at a high-temperature environment.