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

Herein, a new sepiolite/alumina aerogel composite with outstanding toughness and machinability was prepared using AlCl 3 ·6H 2 O 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 AlCl 3 ·6H 2 O 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/cm 3 ) were investigated.