THERMAL CONDUCTIVITY OF POWDER SILICA HOLLOW SPHERES

摘要

Porous particles show remarkable enhancement in heat resistance compared to solid counterparts of the same material, which are a promising candidate for thermal insulator. In the present work, porous materials i.e. uniform hollow silica spheres with size-controllable interiors were prepared through polystyrene template method, which were of different inside radius 188nm and 238nm. Conventional thermal conductivity testing techniques were rarely taken to test such powder materials, the 3ω method was applied in this work. All the experimental values of less than 0.02W/m·K indicated that the powder silica hollow spheres are indeed the high performance heat-insulating materials. The effects in the thermal conductivity of the particle size, packing density were observed. The formula interpreting aerogels originally proposed by Lu were then used to calculate the thermal conductivity of hollow silica spheres. The calculative results match well with the experimental values. On the other hand, ANSYS software was applied to develop a heat conduction model for this type materials based on their hollow structure features. The geometry of the materials was discrete and finite element analysis was performed. The simulative values are higher than the experimental or calculative data, three possible causes were proposed in this paper.