Pyrolysis study of fluorinated sol-gel silica |
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Authors: | Campostrini R Ischia M Armelao L |
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Institution: | (1) Dipartimento di Ingegneria dei Materiali, Università di Trento, Via Mesiano 77, 38050 Trento, Italy;(2) ISTM-CNR and INSTM, Dipartimento di Scienze Chimiche, Università di Padova, Via Marzolo 1, 35131 Padova, Italy |
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Abstract: | Fluorinated silica gels at various fluorine content were prepared via sol-gel by hydrolysis of 3,3,3-trifluoropropyltrimethoxysilane
and tetraethoxysilane mixtures. The gels, of nominal stoichiometry Si(CH2CH2CF3)XO(2-X/2)(X=0.1-1), were characterized by FT-IR, X-ray photoelectron spectroscopy (XPS) and N2 adsorption analysis. The thermal stability of the fluorinated samples was investigated by coupling thermogravimetric measurements
with mass spectrometric and gas chromatographic analyses of the evolved gaseous species. The chemical reactions occurring
in the gel matrices during heating were siloxane chain rearrangements involving condensation between residual hydroxyl and
ethoxyl groups in the 100-350°C temperature range, whereas the thermal decomposition of the fluoroalkyl groups were observed
at higher temperatures (450-600°C). The release of the fluoroalkyl moieties also involved C-F/Si-O bond exchanges inside the
siloxane chains, with gas-phase evolution of different fluorinated silicon units.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | pyrolysis study sol-gel synthesis fluorinated silica gels thermogravimetric-mass spectrometric-gas chromatographic coupled analyses |
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