Thermally Stable Nanoporous ZrO2/SiO2 Hybrid Aerogels for Thermal Insulation

Abstract

Compared with single-component aerogels, hybrid aerogels with multiple components possess enhanced properties, especially high thermal stabilities. Thermal stability improvement depends on the mixing between the various components. In the present research, a ZrO2/SiO2 hybrid aerogel was representatively chosen to study the mixing behaviors and resultant thermal stabilities. A series of ZrO2/SiO2 hybrid aerogels were synthesized by using different sol-gel parameters to study shrinkage, nanopore collapse, and crystallization behavior upon heat treatment. The sol-gel hybridization of weakly branched ZrO2 and SiO2 clusters was found to provide maximum mixing of ZrO2/SiO2. The highly mixed hybrid aerogel, with a ratio of 86/14 w/w ZrO2/SiO2, showed the best thermal stability. The thermally stable ZrO2/SiO2 hybrid aerogel, after incorporation into a mullite fiber blanket, showed very low thermal conductivities of 0.026 ± 0.001, 0.037 ± 0.001, and 0.058 ± 0.002 W/(m K) at 600, 800, and 1000 °C, respectively. It was suggested that weakly branched ZrO2 and SiO2 clusters preferred to freely tangle with each other during the preparation procedure, achieving the most highly mixed ZrO2/SiO2 hybrid with the maximum synergistic effect. This hybrid strategy may provide pathways in designing other multiple-component hybrid aerogels.