2.5CaO·2SiO2 gel was synthesised by hydrolytic polycondensation of tetramethyl orthosilicate (TMOS) with calcium nitrate in alcoholic medium. Thermal treatments were carried out to convert the gel into the glass. However, a completely amorphous sample was not obtained. The gel-derived material structure was examined by FTIR spectroscopy. The IR spectra suggested that the gel-derived material has a different structure than the corresponding melt-quenched glass, for having a more uniform distribution of non-bridging oxygens among the SiO4 tetrahedra. Crystallisation of the gel-derived material, examined by differential thermal analysis is reported and discussed. The activation energy for crystal growth, Ec=782 kJ/mol, and the Avrami parameter, n=1, which indicates a surface nucleation mechanism, were evaluated by non-isothermal methods. The results were compared with those obtained for a conventionally prepared glass of the same composition.
SOL-GEL PREPARATION AND CRYSTALLISATION OF 2.5CaO 2SiO2 GLASSY POWDERS
CATAURO, Michelina;
1998
Abstract
2.5CaO·2SiO2 gel was synthesised by hydrolytic polycondensation of tetramethyl orthosilicate (TMOS) with calcium nitrate in alcoholic medium. Thermal treatments were carried out to convert the gel into the glass. However, a completely amorphous sample was not obtained. The gel-derived material structure was examined by FTIR spectroscopy. The IR spectra suggested that the gel-derived material has a different structure than the corresponding melt-quenched glass, for having a more uniform distribution of non-bridging oxygens among the SiO4 tetrahedra. Crystallisation of the gel-derived material, examined by differential thermal analysis is reported and discussed. The activation energy for crystal growth, Ec=782 kJ/mol, and the Avrami parameter, n=1, which indicates a surface nucleation mechanism, were evaluated by non-isothermal methods. The results were compared with those obtained for a conventionally prepared glass of the same composition.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
