Journal of Sol-Gel Science and Technology

, Volume 3, Issue 3, pp 205–217 | Cite as

Influence of molar ratios of precursor, catalyst, solvent and water on monolithicity and physical properties of TMOS silica aerogels

  • A. Venkateswara Rao
  • G. M. Pajonk
  • N. N. Parvathy
Article

Abstract

In continuation to our earlier work on aerogels, the experimental results on the monolithicity and physical properties of silica aerogels as a function of the molar ratios of tetramethoxysilane (TMOS) precursor, catalyst (NH4OH), methanol (MeOH) solvent and water, are reported. The molar ratios of NH4OH/TMOS, MeOH/TMOS and H2O/TMOS were varied from 7.1 × 10−6 to 9.6 × 10−1, 1 to 90 and 1 to 18 respectively. It has been found that larger molar ratios of NH4OH/TMOS (10−2), MeOH/TMOS (13 to 60) and H2O/TMOS (>10) resulted in transparent but cracked aerogels, and very low molar ratios of these combinations gave monolithic but less transparent or opaque aerogels. The best quality silica aerogels, in terms of monolithicity, transparency and low density, have been obtained with TMOS:MeOH:H2O:NH4OH in the molar ratio of 1:12:4:3.7 × 10−3 respectively. The aerogels have been characterized by density, optical transmission, surface area and porosity measurements. The results have been discussed by taking into account the hydrolysis and condensation reactions, and syneresis effects.

Keywords

aerogels silica monolithicity porous glass optical transmission 

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Copyright information

© Kluwer Academic Publishers 1994

Authors and Affiliations

  • A. Venkateswara Rao
    • 1
  • G. M. Pajonk
    • 1
  • N. N. Parvathy
    • 1
  1. 1.Laboratoire des Matériaux et Procédés CatalytiquesUniversité Claude Bernard Lyon IVilleurbanne CedexFrance

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