Comparison between the process-structure-property relationships of silica foams prepared through two different processing routes

摘要

Cellular silica with improved framework, crosslinking, and stability properties are desirable for applications in thermal insulation. A process for the preparation of cellular silica foam with interconnected cells with tailored porosity and pore size distribution has been attempted. The silica foams have been prepared through two different methods; surfactant-and particle-based stabilization. The silica foams prepared through two different processes namely surfactant-stabilized foams (SSF) and particle-stabilized foams (PSF) have exhibited a wide range of differences in their structure which in turn have shown to affect the final properties of the foam. The cell size distributions in SSF (89 vol% porosity) and PSF (85 vol% porosity) have been found in the range of 50-250 μm (monomodal) and 4-10 μm and 50-100 μm (bimodal), respectively, whereas the cell counts of both have been found in close proximity. The microstructure of both the sintered SSF as well as PSF samples foams have shown an open and interconnected porosity with the permeability of both in the region of ～10~(-8) m~2. The mechanical (compressive) strength and Young's modulus of the PSF are a third of that in SSF. The structure-property relationship of both the SSF and PSF and their comparison have been discussed.