Silica-Aerogel Composites for Thermal Insulations

Abstract

In accordance to the climate negotiations of Paris (COP21) a sustainable handling with energy resources is required. In this context high quality aerogel based thermal super insulation materials are of critical importance to energy-efficiency, as a lot of thermal and therefore energy losses can be reduced for example in industrial processes, buildings or even in the transportation sector. Research and development made great progress and nowadays the properties of silica aerogels with respect to density, thermal conductivity, mechanical strength and shrinkage are adjustable via sol-gel processing. Also the development of composite materials, like embedding aerogel granulates or infiltrating them to nonwoven felts improved the materials. Further investigations to manufacture super-insulating, low density, flame resistant boards leads to the combination of aerogels with honeycombs in general and silica aerogels with paper honeycombs especially. In this combination the selected silica aerogels provide a low density around 0.1 g/cm3, a specific surface area in the range of 100 - 1000 m2/g, low thermal conductivity under SATP conditions between 0.01-0.03 W/mK and a high sound absorption. The paper-honeycombs on the other hand are cheap and widely used for all kinds of packaging, easy and sustainable in production. They possess a low density and thus combine light weight with high stiffness. We report on successfully manufacturing of such composites. The challenges in the preparation are to have almost shrinkage free aerogels, no cracks developing during drying and a perfect bonding at the paper-silica interface. The composite materials are characterized with respect to their mechanical properties (compression and bending tests), microstructure analysis (SEM/TEM), thermal conductivity, flammability and gas permeability. The composite withstand easily 20 minutes at 1000°C open flame without damage on the backside of the aerogel filled board. These results recommend the composite material for several applications in the field of thermal super insulations.