The evolution of TEOS to silica gel and glass by vibrational spectroscopy

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Abstract

Fourier-transform infrared and Raman spectroscopies were simultaneously used in order to study the time evolution of the acid-catalyzed hydrolysis and condensation of tetraethoxysilane (TEOS) in ethanol, to form silica xerogel. The transformation to vitreous silica by gradual densification of the gel was also monitored after different heat treatments. The extent of hydrolysis was revealed by the changes in intensity of the IR-active bands of TEOS at 793 cm (Sisingle bondO asymmetric stretch), 1102 cm−1 (Csingle bondO asymmetric stretch), 1168 cm−1 (CH3 rocking) and 1400 cm−1 (CH2 wagging) and also the TEOS Raman-active bands corresponding to the strongly polarized Sisingle bondO symmetric stretch (656 cm−1) and the depolarized CH3 rocking (960 cm−1). The intensity of all these bands clearly decreased as the reactions proceeded. Good evidence for the formation of ethanol in the initial steps of hydrolysis and for the subsequent predominance of its evaporation was found in the occurrence of maximum intensities for its infrared and Raman-active bands due to deformation of CH3 or CH2 groups (881 cm−1) and CH2 bending (1275 cm−1), after a period of time. The intensity of these bands later decreased. The gel to glass conversion was followed through the disappearance of the infrared peaks at 554 cm) (Sisingle bondOH rocking) and 940 cm−1 (Sisingle bondOH stretching), together with the intensity increase of the peaks at 800 and 1078 cm−1. The complementary nature of the IR and Raman spectroscopies is of great value for a complete understanding of the TEOS to silica glass transformation.

References (18)

  • C.A.M. Mulder et al.

    J. Non-Cryst. Solids

    (1987)
  • D.L. Wood et al.

    J. Non-Cryst. Solids

    (1986)
  • R.M. Almeida et al.

    J. Non-Cryst. Solids

    (1990)
  • A. Bertoluzza et al.

    J. Non-Cryst. Solids

    (1982)
  • C.J. Brinker et al.

    J. Non-Cryst. Solids

    (1985)
  • H. Yoshino et al.

    J. Non-Cryst. Solids

    (1990)
  • S. Sakka et al.

    J. Non-Cryst. Solids

    (1980)
  • R.M. Almeida

    J. Non-Cryst. Solids

    (1988)
  • C.W. Turner et al.

    J. Non-Cryst. Solids

    (1987)
There are more references available in the full text version of this article.

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    The Raman spectra of high silica glass were shown in Fig. 2. There were a number of bands associated with organic functional groups in Raman spectra of xerogel that could be identified as follow according to references [17,18]. The band ∼874 cm−1 was assigned to CH3 or CH2 deformation (EtOH).

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