Use of surface treated aerogels derived from various silica precursors in translucent insulation panels

Many translucent industrial insulation applications require optimization of both the thermal and optical properties. Currently, the thermal performance witnessed in today's products often limits, the amount of available area which call be designated for translucent panels. For example, translucent wall panels for passive lighting systems must provide both adequate light transmission as well as sufficient thermal insulation. In granular fill systems, these demands can sometimes work against each other since thermal performance will improve as the panel thickness is increased but light transmission will decrease accordingly. In contrast, the optical properties can be significantly enhanced by careful control of the particle size and size distribution. This in turn impacts the thermal resistance since spaces between the particles act as large pores that dominate the heat transfer. We have investigated aerogel materials derived from commercially viable silica sources. Results indicate that depending on the silica precursor, particle size distribution, and control over other processing conditions, the optical transparency can be varied from 25% to 80% in a 20 mm layer. Within these same constraints, we have found the thermal conductivity can be varied from 0.0140 to 0.0210 W/m K. This ability to tailor the optical and thermal characteristics, coupled with superior thermal properties of aerogel, may enable more widespread acceptance. (C) 2001 Elsevier Science B.V. All rights reserved.