Low cost silica aerogel production

Abstract

Buildings form a major part of the energy demand in Switzerland. Silica aerogels as high performance insulation materials have the potential to reduce the energy demand for heating and cooling. Silica aerogel insulation materials, can achieve the same thermal insulation performance with only half of the thickness of conventional insulation materials. Translucent, superinsulating silica aerogels exhibit the lowest thermal conductivity of any solid known, typically of the order of 0.015 W· m -1 ·K -1 at ambient temperature, pressure, and relative humidity. The interest in silica aerogels as insulation materials is illustrated by the rapid growth of the aerogel market: in 2004, only about 25 million US$ of aerogel insulation materials were sold, but this had increased to about 500 million US$ by 2013. Still the major drawback for a large scale usage of silica aerogels as standard insulating material in the building sector is their production cost. As a result, most of the current aerogel production is used for industrial applications such as pipeline insulation, rather than building insulation. Silicon alkoxides such as tetramethoxysilane (TMOS), and tetraethoxysilane (TEOS) are the most common precursors for the production of silica aerogel. Although the chemistry of silicon alkoxide gelation is straightforward from a chemical perspective, alkoxides have their drawbacks, for example their high production cost due to a multi-step synthesis procedure. Although less reactive, TEOS is often preferred over TMOS because its price is about four times lower and because it is less hazardous. Still the minimum material cost of the raw materials for silica aerogel production is 700-800 CHF/m 3 of aerogel. Our group developed an alternative route for the silica aerogel production using low cost silica precursors and ambient pressure drying technique. This potentially lowers the material cost by a factor of two or more. With the development of more cost-efficient large-scale production technologies, silica aerogel materials have the potential to gain a significant share of the building insulation market by 2020, particularly for retrofit applications.