Silica-based core materials for thermal superinsulations in various applications

Abstract

Vacuum insulation panels (VIP) are usually manufactured using standardized manufacturing processes based on empirical values and in most cases with any fumed silica as the main component of the core material. However, not all applications have the same requirements in terms of thermal conductivity and service life. Therefore, it is useful to adapt the kind of core materials and their product specifications, such as particle size and porosity, to the different applications. Furthermore, in some applications cheaper core materials, like precipitated silica, would be a reasonable alternative. To replace the time-consuming series of measurements for this purpose, this work offers comprehensive parameter studies to determine the optimum product properties of precipitated silica, fumed silica, silica gel, and glass spheres for use in the building sector, in transport boxes, as a superinsulation at atmospheric pressure, and as a switchable VIP. As a result, not only the preferred materials but also their porosities and particle sizes are presented. For atmospheric pressure and construction applications, fumed silica has to be preferred. For the transport sector and switchable VIPs as well as certain special applications, precipitated silica and silica gel may well be reasonable alternatives.