A homogeneous silica gel sample bearing ≡Si-H groups was prepared, via sol-gel method, by hydrolysis of trimethoxysilane under acid condition in tetrahydrofuran. Preliminary NMR experiments in liquid phase indicated an immediate and complete hydrolysis of Si-OCH3, followed by a slower condensation of the Si-OH groups, with maintenance of Si-H bonds. The crude-gel, and samples heated to various temperatures, were characterized by different instrumental methods, including FTIR, density, porosity, and specific surface area. These data indicate that the crude-gel was a dense material which, on heating, increases porosity and surface area up to ca 500�C. The thermal behavior was studied in inert atmosphere by means of coupled thermogravimetric, gas chromatographic, mass spectrometric analyses. The pyrolysis process was described by the fundamental chemical reactions occurring among the siloxane chains of the gel network and by the qualitative and semiquantitative chemical analysis of the compounds released in gas-phase. The proposed pyrolysis mechanism was discussed and interpreted in agreement with the change of the morphological properties of the gel. The pyrolysis data and the mass balance between the compounds released in gas-phase and the solid residue at 1000�C allowed the determination of a nominal chemical formula to describe the crude-gel composition.
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| Journal of Thermal Analysis and Calorimetry | |
|---|---|
| Language | English |
| Size | A4 |
| Year of Foundation |
1969 |
| Volumes per Year |
1 |
| Issues per Year |
24 |
| Founder | Akadémiai Kiadó |
| Founder's Address |
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245. |
| Publisher | Akadémiai Kiadó Springer Nature Switzerland AG |
| Publisher's Address |
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245. CH-6330 Cham, Switzerland Gewerbestrasse 11. |
| Responsible Publisher |
Chief Executive Officer, Akadémiai Kiadó |
| ISSN | 1388-6150 (Print) |
| ISSN | 1588-2926 (Online) |
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