Infrared studies of alkoxide gels

doi:10.1016/0022-3093(86)90127-4

Journal of Non-Crystalline Solids

Volume 82, Issues 1–3, 1 June 1986, Pages 171-176

https://doi.org/10.1016/0022-3093(86)90127-4 Get rights and content

Abstract

Dried alkoxide silica gels were studied by infrared spectroscopy after equilibration with room air and with vacuum. H₂O is reversibly adsorbed in the gel pores and held by hydrogen bonding to surface silanol groups. The rates of loss or gain of adsorbed water at room temperature differ according to the conditions of preparation, and the rates are characteristic of the pore size and shape distribution. Less water is found in gels made with fluoride compared with similar gels made without, and the BET surface areas are also smaller in the gels made with fluoride. Differences among the spectra of gels made from alkoxides are due to differences in the sites to which water molecules are attached when equilibrated in moist air, and quantitative determinations of H₂O content can be made from the intensity of the 5292 cm⁻¹ absorption band.

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The presence of large pores is generally desirable to suppress the fracture during drying and bubbling due to the release of gaseous species during sintering. In addition, SiF groups formed by the HF catalysis may replace SiOH groups [20–23], which increase the optical loss at fiber telecommunication spectral range (wavelength at ∼1.5 μm) and enhance the non-radiative decay of PL centers. Incorporation of fluorine in silica matrix may also be effective in suppressing the oxidation of fluoride nanocrystals during sintering.
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¹: We are grateful to C. McCrory-Joy, T.Y. Kometani, L.D. Blitzer, and A.M. Williams for analyses, and to K. Nassau, A. Miller, J.B. MacChesney, D.W. Johnson Jr for helpful discussions.

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Infrared studies of alkoxide gels

Abstract

J. Amer. Ceram. Soc.