Abstract
The surface free energy of a monolithic silica xerogel treated at 1000°C has been measured by inverse gas chromatography in the temperature range 25–150°C using n-alkanes. Values of the dispersive component, γS D, vary from 49.07 mJ·m−2 at 25°C to 17.20 mJ·m−2 at 150°C. The γS D value obtained at 25°C is lower than that found for amorphous and crystalline silicas but higher than that found for glass fibres meaning that the heat treatment at 1000°C changes drastically the structure of the silica xerogel showing a surface similar to a glass. However, the higher value of γS D in comparison to glass fibres can be attributed to the mesoporous structure present in the silica xerogel. In the temperature range of 60–90°C there exists an abrupt change of the γS D values as well as in the dispersive component of the surface enthalpy, h S D. Such abrupt change can be attributed to an entropic contribution of the surface free energy.
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Rubio, F., Rubio, J. & Oteo, J. Effect of the Measurement Temperature on the Dispersive Component of the Surface Free Energy of a Heat Treated SiO2 Xerogel. Journal of Sol-Gel Science and Technology 18, 115–118 (2000). https://doi.org/10.1023/A:1008756718043
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DOI: https://doi.org/10.1023/A:1008756718043