Restructure of expanded cork with fumed silica as novel core materials for vacuum insulation panels

Using expanded cork dust as a cheaper substitute of fumed silica, the expanded cork/fumed silica composites with hierarchical porous structure were designed and constructed as an alternative lower cost material for vacuum insulation panel (VIP) core. A novel strategy compromised of microwave pretreatment and vacuum impregnation method is developed for cork restructuring and recombination. The morphology, microstructure and thermo-physical properties of expanded cork/fumed silica composites were thoroughly investigated. It is found that the microwave pretreatment is a rapid and effective method to restructure cork, and then fumed silica can be introduced into the cork pores efficiently by the vacuum impregnation method, resulting in a hierarchical microstructure of cork micro-pores and nano-porous fumed silica micelle. Thanks to this unique hierarchical porous structure, the hybrid expanded cork-fumed silica materials show an excellent thermal insulation property (as low as 6.3 mW/m·K at pressure < 1 mbar). The results demonstrate that the proposed strategy is an efficient means to construct a hierarchical porous expanded cork/fumed silica hybrid network system, and the as-prepared composites could have a potential application for VIPs core materials due its cost-effective and good thermal insulation performance.