Interfacial modification and ultra-low concentration sol impregnation: A combined approach for tailoring the pore structure and improving the thermal insulation performance of fumed silica compact

Abstract

Abstract Fumed silica compacts for buildings show outstanding thermal insulation performance. However, the completely elimination of macropores within the fumed silica compacts under the condition of optimum level of compaction is rather difficult, which has a negative impact on its thermal insulation property. Here, a novel method of interfacial modification combined with ultra-low concentration sol impregnation is proposed to tailor the pore structure and reduce the thermal conductivity of fumed silica compacts. The result shows that, compared with the general sol impregnation treatment (without interfacial modification)，the thermal conductivity of the resulting fumed silica compact after interfacial modification and ultra-low concentration sol impregnation significantly decreases from 26.6\u202fmW/(m·K) to 22.0\u202fmW/(m·K), as the pore diameter and the volume fraction of macropores decreases from 100\u202fnm to 37\u202fnm and from 64.91% to 30.32%, respectively. The decrease in the amount of silanols on the surface of the fumed silica matrix effectively inhibits the interfacial adhesion of the colloidal particles introduced by the ultra-low concentration impregnation and thus promoting the formation of new mesoporous networks of the silica aerogel, which further improving the pore structure and reducing the thermal conductivity of fumed silica compacts at the optimum level of compaction.