TY - JOUR
T1 - Structure and energetics of silica in the sol-gel to ceramic transitions
AU - Ying, Jackie Y.
AU - Benziger, Jay Burton
N1 - Funding Information:
Acknowledgment is made to the donors of The Petroleum Research Fund, administered by the American Chemical Society for partial support of this research. One of us (JYY) thanks the General
Funding Information:
Electric Foundation and AT&T Foundation for fellowship support during this work.
PY - 1993/7/6
Y1 - 1993/7/6
N2 - Sol-gels of colloidal silica were characterized with photoacoustic Fourier-transform infrared spectroscopy, differential scanning calorimetry, thermogravimetry, drop solution calorimetry and X-ray diffraction. Infrared spectroscopy showed that water and hydrogen-bonded silanol were removed from the gels with increasing temperature. The intensity of the isolated SiOH stretching band increased as temperatures increased to 800°C, then decreased as the temperature was increased further and densification occurred. Sintering was facilitated by an oxygen atmosphere. The colloidal silica gel densified at 1150°C in O2, but densification was negligible in an N2 atmosphere. When polyvinyl alcohol was used as a binding additive to the gel, the resulting gel densified and crystallized to cristobalite between 1000 and 1150°C in both oxygen and nitrogen. The crystallization was found to result from alkali impurities in the PVA. Photoacoustic spectra of the gels showed that the PVA adsorbed to the silica surfaces through the surface hydroxyl groups, helping to tether particles together.
AB - Sol-gels of colloidal silica were characterized with photoacoustic Fourier-transform infrared spectroscopy, differential scanning calorimetry, thermogravimetry, drop solution calorimetry and X-ray diffraction. Infrared spectroscopy showed that water and hydrogen-bonded silanol were removed from the gels with increasing temperature. The intensity of the isolated SiOH stretching band increased as temperatures increased to 800°C, then decreased as the temperature was increased further and densification occurred. Sintering was facilitated by an oxygen atmosphere. The colloidal silica gel densified at 1150°C in O2, but densification was negligible in an N2 atmosphere. When polyvinyl alcohol was used as a binding additive to the gel, the resulting gel densified and crystallized to cristobalite between 1000 and 1150°C in both oxygen and nitrogen. The crystallization was found to result from alkali impurities in the PVA. Photoacoustic spectra of the gels showed that the PVA adsorbed to the silica surfaces through the surface hydroxyl groups, helping to tether particles together.
KW - Ceramic transition
KW - Energetics
KW - Silica
KW - Sol-gel
KW - Structure
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U2 - 10.1016/0927-7757(93)80395-U
DO - 10.1016/0927-7757(93)80395-U
M3 - Article
AN - SCOPUS:0027910492
SN - 0927-7757
VL - 74
SP - 23
EP - 31
JO - Colloids and Surfaces A: Physicochemical and Engineering Aspects
JF - Colloids and Surfaces A: Physicochemical and Engineering Aspects
IS - 1
ER -