Ultra-small sepiolite fiber toughened alumina aerogel with enhanced thermal stability and machinability

Abstract

Herein, a new sepiolite/alumina aerogel composite with outstanding toughness and machinability was prepared using AlCl3·6H2O precursor and sepiolite fibers by a specific sol–gel process and supercritical fluid drying. Sepiolite was added into the aluminum sols containing as high as 37 wt% of AlCl3·6H2O and the resulting sepiolite fibers dispersed randomly and uniformly with the lengths of 60–100 nm and diameters of 2–3 nm. With the increase in the ratio of sepiolite, the sepiolite-alumina aerogel composites exhibit no shrinkage during the sol–gel process and supercritical fluid drying, while a linear shrinkage of 4.6% was observed after heat-treatment at 1000 °C. Compared with undoped alumina aerogels, the sepiolite/alumina aerogel composites exhibit outstanding toughness and machinability on grinding, slicing and perforating. Meanwhile, the morphology, phase nature, and porosity of sepiolite/alumina aerogel composites with different sepiolite content (from 0 to 0.06 g/cm3) were investigated.