Composites of silica aerogels with organics: a review of synthesis and mechanical properties

Aerogels are considered as outstanding future materials owing to their wide surface area and three-dimensional network of silica particles, low density, low-thermal conductivity, high porosity, and low dielectric property. Their outstanding characteristics represent excellent potential applications in thermal insulation systems, aeronautical domains, environmental clean-up and protection, as heat storage devices, transparent windows, thickening agents in paints, etc. Among these applications, thermal insulating materials can play a vital role in living systems and for saving energy in various domestic and industrial processes. However, native silica aerogels are fragile and sensitive to relatively low pressures, which limit their application. More robust aerogels with higher strength and stiffness can be obtained by compounding silica networks with organoalkoxysilanes, polymers or using porous scaffolds as supports. This paper presents a review on the approaches for mechanical reinforcing methods for silica aerogels and recent achievements toward improving the strength of native silica aerogels. In addition, various characteristics derived from composite aerogels are analyzed synthetically.