Optimized preparation of thermal insulation hydrophobic SiO2 aerogel based on orthogonal design method

Abstract

Uses tetraethyl orthosilicate (TEOS) as the silicon source, ethanol (EtOH) as the solvent, water (H₂O) as the reactant, and trimethylchlorosilane (TMCS) as the surface modifier, the heat-insulating hydrophobic SiO₂ aerogel was prepared by the acid–base catalyzed sol–gel method followed by the ambient pressure drying. In order to systematically study the effect of multi-parameter combination on the preparation of thermally insulating hydrophobic SiO₂ aerogel, four-factor three-level orthogonal experiments with modifier concentration, silicon alcohol ratio, modification time, and replacement times as influencing factors were carried out. The extremum analysis method is used to analyze the experimental results, and found the measurement relationship of the orthogonal test factors that affect the preparation of low-density and high-porosity SiO₂ aerogel is: Modifier concentration (TMCS vol%) > silicon alcohol ratio (TEOS:EtOH) > Modification time > Replacement times. When the TMCS vol% is 40, TEOS:EtOH is 1:9, the modification time is 4 h, and the number of replacements is 5 times, a heat-insulating hydrophobic SiO₂ aerogel with a density of 0.113 g/cm³, a porosity of 94.84%, a pore diameter of 5–8 nm, a specific surface area of 1030.67 m²/g, and a thermal conductivity of 0.030 W/(m K) can be obtained.