Modulating pore microstructure of silica aerogels dried at ambient pressure by adding N-hexane to the solvent

In this work, a kind of superhydrophobic silica aerogels was prepared at ambient pressure using tetraethoxysilane (TEOS) as precursor. Particularly, N-hexane was added in the solvent to modulation pore microstructure and effect on the insulation properties of samples were analyzed. It is discovered that when the volume ratio of N-hexane to TEOS is 1:2.24 the thermal conductivity of samples can reach the lowest of 0.012 W/m.K. Compared with that of samples no addition of N-hexane, the density is decreased, the theoretical average pore size increases and the total pore volume increases. Due to N-hexane it leads cross-linking between the sol particles stronger and inhomogeneous. Thus gelation process is speeded up resulting in a change in pore structure. Low density can reduce the solid-phase heat transfer, perfect pore microstructure reduces the contribution of gas-phase heat transfer, and only when the two aspects forms a suitable combination it can exhibit optimal thermal insulation performance.

Automated summary

In this study, superhydrophobic silica aerogels were synthesized at ambient pressure using TEOS as precursor. The addition of N-hexane in the solvent helped to modulate the pore microstructure, and its effect on the insulation properties of the samples was analyzed. It was discovered that the thermal conductivity of the samples reached the lowest value of 0.012 W/m.K when the volume ratio of N-hexane to TEOS was 1:2.24. The addition of N-hexane led to a decrease in density, an increase in the theoretical average pore size, and an increase in the total pore volume, due to the stronger and more heterogeneous cross-linking between the sol particles. The optimal thermal insulation performance was achieved when the combination of low density and perfect pore microstructure reduced both solid-phase and gas-phase heat transfer contributions.