B.P. Jelle, T. Gao, L.I.C. Sandberg, B.G. Tilset, M. Grandcolas, A. Gustavsen
thermal insulation, nano insulation material, Knudsen effect, hollow silica nanospheres
A major key strategy to achieve energy-efficient buildings is the development of high performance thermal building insulation materials, also often called superinsulation. A possible and promising way to reach these advanced insulation materials is to exploit the Knudsen effect, where the gas thermal conductivity is reduced as the pore diameter in a material is decreased below the mean free path of the gas molecules, i.e. in the nanometer range. The nano insulation materials (NIM) utilizing the Knudsen effect, and also addressing radiation and solid state thermal conduction aspects, may be made by miscellaneous fabrication techniques. Currently, our NIM research is mainly focused on various attempts to tailor-make hollow silica nanospheres (HSNS) by manufacturing and applying different sacrificial templates, synthesis procedures, parameter variations, and inner diameters and shell thicknesses of the nanospheres. The future NIMs may not necessarily be based on HSNS, nevertheless the investigations on the HSNS represent a possible stepping-stone towards the ultimate goal of achieving high performance thermal insulation materials.