Hydroxyethyl cellulose/alumina-based aerogels as lightweight insulating materials with high mechanical strength

Alumina aerogels reinforced with hydroxyethyl cellulose (HEC) have been successfully synthesised using an environmentally friendly freeze-drying method. Alumina aerogels are materials with interesting properties, such as low density, high-temperature stability, high porosity and high surface area, which can be used in several industrial applications. It is necessary to add one or more supporting materials, such as carbon nanofibres and a fibrous second phase such as cellulose, to the matrix to reinforce the mechanical properties of the aerogels. In this study, the influence of the HEC-to-aluminium tri-sec-butoxide (ASB) solution mass ratio on the morphological, mechanical and thermal properties of the synthesised aerogels and its impact on the thermal insulation properties of the resulting materials were evaluated. The apparent density of the hydroxyethyl cellulose-reinforced alumina-based aerogels increased with the amount of HEC. Thus, compact structures with a small pore size were obtained when increasing HEC/ASB solution mass ratio. The incorporation of HEC into the ASB matrix led to an increase in the mechanical properties in terms of the Young’s modulus. Thermal stability of samples varied as a consequence of the HEC addition. Thus, the second decomposition stage shifted to lower temperatures with HEC incorporation. In addition, all synthesised aerogels showed low thermal conductivities. The remarkable physical characteristics of the hydroxyethyl cellulose-reinforced alumina-based aerogels prepared herein and the successful synthesis suitable for scale-up make them a good candidate for construction applications.