Preparation of Sodium Silicate–Based Aerogels Using a Two-Step Sol–Gel Process and Ambient Pressure Drying

摘要

The experimental result on the preparation of sodium silicate–based aerogels using a two-step sol–gel process and ambient pressure drying is presented. The silica aerogels are prepared by following the procedure, namely, gel preparation, shaking of the gel in water and methanol, silylation/washing of the gel, and finally drying of the silylated gel at ambient pressure. The influence of various sol–gel and preparation parameters such as wt% of silica (2–6 wt%), NH4F:HCl molar ratios (0–0.5), and aging periods (0 to 24 h) on the physical and textural properties of the aerogels is studied. The physical properties such as bulk density, thermal conductivity, optical transmission, as well as the textural properties using BET analysis are studied. It is observed that the silica aerogels prepared using 3 wt% of silica, NH4F:HCl molar ratio of 0.333, and 3-h aging period have low density ≈0.11 g cc~(–1), low thermal conductivity ≈0.12 W mK~(–1), as well as larger BJH (desorption) and BET surface areas of around 900 and 590 m2 g~(–1), respectively. The as-synthesized aerogels have reduced processing period of 36 h and posses larger surface area. The as-synthesized aerogels can be applied for thermal insulation purpose.