This paper reports the preparation of cast-in-situ, large-sized monolithic silica xerogels by a two-step acid⁻base catalyzed approach under ambient pressure drying. Low-cost industrial silica sol and deionized water were used as the silicon source and the solvent, respectively. Hexadecetyltrimethylammonium bromide (CTAB) was used as a modification agent. Different amounts of polyethylene glycol 400 (PEG400) was added as a pore-forming agent. The prepared silica xerogels under ambient pressure drying have a mesoporous structure with a low density of 221 mg·cm-3 and a thermal conductivity of 0.0428 W·m-1·K-1. The low-cost and facile preparation process, as well as the superior performance of the monolithic silica xerogels make it a promising candidate for industrial thermal insulation materials.
Keywords: ambient pressure drying; binder and pore-forming agent; silica sol; surfactant.