Preparation of ultrafine flexible alumina fiber for heat insulation by the electrospinning method

In this work, aluminum isopropoxide is used as the aluminum source, and acetylacetone (Hacac) is used as the ligand to synthesize a precursor, which can be used to prepare ultrafine Al2O3 fibers. Fiber with excellent flexibility is obtained by electrospinning and subsequent heat treatment processes. The uniform diameter of the fiber is approximately 300–400 nm, and it has a compact structure and no surface defects, such as cracks and holes, the lack of which can prevent it from being damaged in the process of flexible behavior, such as folding in half. By analyzing the crystallization transformation process of the Al2O3 precursor fibers, it is found that the precursor begins to transform from amorphous to γ-Al2O3 at approximately 700 °C. After heat treatment at 1000 °C, it completely changed to α-Al2O3, which is 100–200 °C lower than the results reported in previous literature. Even after heat treatment at 1200 °C, the fiber still has good flexibility, which ensures its functional performance. In addition, the thermal conductivity of the prepared Al2O3 fibers was only 0.318 W/m·K at 1000 °C, which can be used as a thermal insulation material in aerospace, high-temperature industries and other fields.