Abstract
Calcium boroaluminosilicate xerogels and glasses with an E-glass composition were synthesized using metal alkoxides and metal salt as precursors. Structural evolution during the gel-to-glass transition was monitored by FTIR and NMR spectroscopies. Kramers-Kronig analysis was performed on the FTIR specular reflectance data to yield the ε2 and Im(-1/ε) spectra for the xerogels and the glass. A xerogel treated at 600°C exhibits distinct structural characteristics relative to the glass. A significantly higher concentration of BIV is present in the xerogel due to the large amount of surface boranol groups. Another unique feature of this xerogel is revealed by a red-shift in the high-frequency LO mode of the Si-O stretching vibration relative to the dense glass. This shift is attributed to a surface mode in the vibrational spectrum which is a consequence of the high surface area and the particulate structure of the xerogel. A xerogel treated at 710°C has FTIR and NMR spectra that are similar to the dense glass. Thus, the bulk network structure of the glass is present in the 710°C xerogel. A higher surface area (∼ 40 m2/g) and concentration of isolated surface Si-OH and B-OH groups distinguish it from the dense glass. An important conclusion of this study is that the only fundamental difference between the 710°C xerogel and the glass is the surface of the xerogel. In this sense, monolithic xerogels can provide convenient substrates for studying the surface chemistry of multicomponent glasses.
Original language | English (US) |
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Pages (from-to) | 225-233 |
Number of pages | 9 |
Journal | Journal of Non-Crystalline Solids |
Volume | 142 |
Issue number | C |
DOIs | |
State | Published - 1992 |
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry