Abstract
Silica aerogel microspheres based on alkali silica sol were synthesized using the emulsion method. The experimental results revealed that the silica aerogel microspheres (4–20 µm in diameter) were mesoporous solids with an average pore diameter ranging from 6 to 35 nm. The tapping densities and specific surface areas of the aerogel microspheres are in the range of 0.112–0.287 g/cm3 and 207.5–660.6 m2/g, respectively. The diameter of the silica aerogel microspheres could be tailored by varying the processing conditions including agitation rate, water/oil ratio, mass ratio of Span 80: Tween 80, and emulsifier concentration. The effects of these parameters on the morphology and textural properties of the synthesized silica aerogel microspheres were systematically investigated. Such silica aerogel microspheres can be used to prepare large-scale silica aerogels at an ambient pressure for applications in separation and high efficiency catalysis, which requires features of high porosity and easy fill and recovery.
Highlights
Aerogels are highly porous and possess remarkable properties such as high specific surface area and low thermal conductivity [1,2,3]
The specific surface area was calculated using the Brunauer-Emmett-Teller (BET) method, whereas the pore size distribution was determined by the Barrett-Joyner-Halenda (BJH) method
Silica aerogel microspheres based on alkali silica sol were synthesized using the emulsion method
Summary
Aerogels are highly porous and possess remarkable properties such as high specific surface area and low thermal conductivity [1,2,3]. A potential approach to address the above challenge is to pre-synthesize silica aerogel microspheres In this way, the solvent exchange step could proceed quickly (minimal diffusion obstacles), allowing a dramatic reduction in synthesis time [17]. Liu et al demonstrated the synthesis of titania-silica microspheres by a water-in-oil emulsion technique combined with APD [19]. They used Span 80 and Tween 85 as surfactants, and the hydrophile-lipophile balance (HLB) value of the emulsion was 4.9. Controlling the dimension of silica aerogel microspheres will significantly facilitate the fabrication of large scale silica aerogels at an ambient pressure at the step. The effect of surface modification on the silica aerogel microspheres was examined
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