Direct synthesis of ultralight, elastic, high-temperature insulation N-doped TiO 2 ceramic nanofibrous sponges via conjugate electrospinning.

The design of three-dimensional ceramic nanofibrous materials with high-temperature insulation and flame-retardant characteristics is of significant interest due to the effectively improved mechanical properties. However, achieving a pure ceramic monolith with ultra-low density, high elasticity and toughness remains a great challenge. Herein, a low-cost, scalable strategy to fabricate ultralight and mechanically robust N-doped TiO 2 ceramic nanofibrous sponges with a continuous stratified structure by conjugate electrospinning is reported. Remarkably, the introduction of dopamine into the precursor nanofibers is engineered, which realizes the nitrogen doping to inhibit the TiO 2 grain growth, endowing single nanofibers with a smoother, less defective surface. Besides, the self-polymerization process of dopamine allows the construction of bonding points between nanofibers and optimizes the distribution of inorganic micelles on polymer templates. Moreover, a rotating disk receiving device under different rotating speeds is designed to obtain N-doped TiO 2 sponges with various interlamellar spacings, further affecting the maximum compressive deformation capacity. The resulting ceramic sponges, consisting of fluffy crosslinked nanofiber layers, possess low densities of 12-45 mg cm -3 , which can quickly recover under a large strain of 80% and have only 9.2% plastic deformation after 100 compression cycles. In addition, the sponge also exhibits a temperature-invariant superelasticity at 25-800 °C and a low heat conductivity of 0.0285 W m -1 K -1 , with an outstanding thermal insulation property, making it an ideal insulation material for high-temperature or harsh conditions.