TiO₂ Nanorod Array-Enhanced Si₃N₄ Nanoribbon Aerogels with Superior High-Temperature Insulation

It is necessary to incorporate infrared opacifiers into ceramic aerogels for inhibiting the thermal radiative heat transfer at high temperature, since the porous structures are almost transparent to the strong infrared radiation. The key challenge, however, lies in how to create a strong interfacial bond between opacifiers and aerogel networks, thereby ensuring their structural and functional stability under cyclic strain or high-frequency vibration. Here, a layer of TiO₂ nanorod (TiONR) arrays is in situ grown onto silicon nitride nanoribbon (SiNNR) aerogels via the hydrothermal reaction method to improve their thermal insulating efficiency at high temperature. By adjusting the reaction time, the density of the TiONR array can be significantly increased, thereby enabling the complete encapsulation of both sides of each nanoribbon. From room temperature to 800 °C, the thermal conductivity increases by 231% for SiNNR aerogels but only 82% for TiONR/SiNNR aerogels, indicating that the TiONR array markedly suppresses radiative heat transfer. Moreover, the robust interface formed between TiONR and SiNNR not only imparts remarkable flexibility to the aerogel but also effectively protects the nanoribbons from oxidation. The grafting of opacifier arrays onto the building blocks offers an effective strategy to simultaneously enhance the high-temperature insulation and oxidation resistance of ceramic aerogels.