Formamide as novel catalyst for the gelation of water glass to synthesize silica aerogel monolith

Water glass (WG)-based aerogels (WAGs) are challenged with requirement of acid catalyst and poor mechanical property. In this work, we have developed a novel formamide (FA) as catalyst for gelation of WG at alkaline condition to prepare WAG monolith under atmospheric pressure drying (APD). The FA serves both as the catalyst by hydrolyzing product formic acid and drying control agent. The effect of the gelation temperature, FA dosage, and WG concentration on the gelation time, density, shrinkage and microstructure of the aerogels were analyzed. The optimum WAG monolith shows a low shrinkage of 20 % and density of 0.165 g cm⁻³, as well as large specific surface area of 229.4 m² g⁻¹ and superhydrophobic surface. The connected nanoparticle into three-dimensional network endows the WAG monolith with good mechanical property. Due to the low-cost, easy fabrication process and free usage of acids, the method expands the synthesis of aerogel monolith.