Structural Evolution of Alkoxide Silica Gels to Glass: Effect of Catalyst pH

Jackie Y. Ying, Jay Burton Benziger, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

91 Scopus citations

Abstract

Structural and energetic changes of alkoxide silica during densification were followed in situ using photoacoustic Fourier‐transform infrared spectroscopy (PAS‐FTIR), transposed temperature drop calorimetry, and drop solution calorimetry. Acid‐catalyzed silica gels contained higher concentrations of adsorbed water, silanol groups, and unreacted alkoxy groups than did the base‐catalyzed gels/precipitates. The surface species in acid‐catalyzed gels were removed easily, allowing this material to be densified at 800°C. The densified material was both structurally and energetically equivalent to fused silica glass. Base‐catalyzed gels had fewer silanol groups in the green state, but free silanol groups emerged during drying at 500°C. The base‐catalyzed gels did not densify below 1000°C, maintaining a high surface area of 100 m2/g. Base‐catalyzed alkoxide gels comprised strained ring structures; their IR spectra were similar to those of fumed silica, but they were energetically much less stable.

Original languageEnglish (US)
Pages (from-to)2571-2582
Number of pages12
JournalJournal of the American Ceramic Society
Volume76
Issue number10
DOIs
StatePublished - Jan 1 1993

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites
  • Materials Chemistry

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