The relationship between the silica wet-gels relative optical transmittance at 500Â nm and structural features of silica aerogels

Aerogels are usually synthesized from supercritical drying of wet-gels. High quality aerogels are usually characterized with high specific surface area (measured by BET method here) and high degree of polymerization of silicate (characterized by 29Si NMR here). The quality of the aerogels depends highly on the quality of the corresponding wet-gels because the skeletal structure in the wet-gels changes only slightly in the supercritical drying process. Here we present a simple method to predict the quality of the desired silica aerogels before the supercritical drying. We found that the relative optical transmittance of the silica wet-gels at 500 nm had good linear correlation with the specific surface area and the degree of silicate polymerization in the corresponding aerogels. We can assess the quality and screen out the low-quality wet-gels from supercritical drying operation, and greatly reduce the cost for aerogel production.