Light and super-insulating silica aerogel fibers by extrusion process

Kurzfassung

Silica aerogels are porous solid materials with high insulation poperties. Their open porous nanostructure inhibits diffusion and circulation-processes of air, which is one of the main reasons for thermal conductivity. Typically thermal conductivity values of silica aerogels are between 0.01 and 0.03 W/m*K (expanded polystyrene: 0.035 – 0.05 W/m*K). Silica aerogels are brittle and stiff like all the inorganic material (ceramics or glasses). Additionally, they easily brake under vibration and compressive stress. In order to give flexibility it is necessary to shape those materials into fibers with low diameter. Like glass and ceramic also silica aerogel fibers are flexible and can be processed into textile structures like fleece, which could withstand bending stress and vibration. Cellulose based aerogel fibres have already been produced and they show good results in terms of thermal insulation.1 However, cellulose decomposes at 200 °C. Silica aerogels enable temperatures around 600 °C and even more. Additionally, silica based fibres are resistant against the most common acids. The production of silica aerogel fibers and its textile processing is the aim of this research project. Aerogels are synthezised via sol-gel-process. The wet gel is put into an extruder to form fibers. After regeneration and drying with supercritical CO2 highly porous, nano-structured silica aerogel fibers are produced². The content of reaction partners, gelation time and reaction temperature are important parameters and affect the spinnability of the wet gel. Systematical experiments for spinning conditions are carried out. The effect of the process on the degree of viscosity, nano-structure formation and surface area are described. Aim of the project is to fiberize highly porous silica aerogels which have a high temperature resistance. Possible applications are extrem light thermal insulation material or filling material for different materials like concretes to improve thermal insulation.