The Effect of Catalyst and Water Content of the Hydrolysis Step on the Physical Properties of Silica Aerogel Dried at the Ambient Pressure

Authors

Department of Textile Engineering, Isfahan University of Technology, Isfahan, Iran

Abstract

In the present study, silica aerogel was evaluated by a two-step catalytic process at the ambient pressure drying, under different synthesis conditions. The effects of  the catalyst and water content in the hydrolysis step on the physical properties of silica aerogel, including density, porosity and shrinkage, were investigated. The results showed that increasing the water content in the hydrolysis step increased the shrinkage of gel network and density of obtained aerogel. Moreover, in the presence of insufficient water, NH4OH as the condensation catalyst in the gel formation step was more effective on the physical properties of silica aerogel, as compared to HCl as  thehydrolysis catalyst; Moreover, the increase in the NH4OH content led to lower density and higher porosity. On the other hand, NH4OH effect on the physical properties of silica aerogel was not noticeable in the presence of enough water content. In the NH4OH/HCl molar ratio of 6, the best silica aerogel sample was obtained with the density of 0.214 g/cm3, porosity of 90% and shrinkage of 23%

Keywords

References

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Journal of Advanced Materials in Engineering (Esteghlal)
Volume 37, Issue 1
June 2018
Pages 27-35

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