SiN Nanofibrous Aerogel with In Situ Growth of SiO Coating and Nanowires for Oil/Water Separation and Thermal Insulation.

Nanofibrous aerogels constructed by ceramic fiber components (CNFAs) feature lightweight, compressibility, and high-temperature resistance, which are superior to brittle ceramic aerogels assembled from nanoparticles. Up to now, in order to obtain CNFAs with stable framework and multifunctionality such as hydrophobicity and gas absorption, it is necessary to perform binding and surface modification processes, respectively. However, the microstructure as well as properties of CNFAs are deteriorated by the direct addition of binders and modifiers. To tackle these problems, we introduced a unique low-temperature (100 °C) chemical vapor deposition method (LTCVD) to achieve the cross-linking and hydrophobization of SiN CNFA in only one step. More importantly, during the LTCVD process, SiO coatings and nanowire arrays were in situ formed via vapor-solid (VS) and vapor-liquid-solid (VLS) mechanisms on the surface and intersection of SiN nanofibers, which cemented the aerogel framework, endowed it with hydrophobicity, and improved its oxidation resistance at high temperature. Compared to most of its counterparts, the SiN/SiO CNFA exhibited better mechanical properties, higher capability of oil/water separation (33-76 g·g), lower thermal conductivity (0.0157 W/m·K), and superior structural stability in a wide temperature range of -196-1200 °C. This work not only presents an excellent SiN/SiO CNFA for the first time but also provides fresh insights for the exquisite preparation strategy of CNFAs.