The nucleation and growth of zircon (ZrSiO4) crystals on the free surface of a 2·3Li2O.1·1ZrO2.6·6 SiO2 glass was investigated through differential thermal analysis (DTA), x-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallisation was completed at about 860°C with an activation energy value corresponding to 740 kJmol-1. Samples with polished free surfaces were nucleated at selected temperatures in the range 640-690°C and then heated at 750°C for 30 rain for crystal growth. A dominant effect of surface nucleation was observed and the number of ZrSiO4 crystals per unit area and the mechanism of crystallisation were determined. It was concluded that the nucleation starts from a fixed number of surface nuclei which reach a maximum at 670°C corresponding to a zircon crystal number density of 1·33×1011 m-2 and that at 880°C a uniform surface crystalline layer was formed with a rate of growth of 1·93 μm min-1.
Crystallisation kinetics of a 2·3Li2O. 1·1ZrO2.6·6SiO2 glass / Novaes de Oliveira, A. P.; Alarcon, O. E.; Manfredini, T.; Pellacani, G. C.; Siligardi, C.. - In: PHYSICS AND CHEMISTRY OF GLASSES. - ISSN 0031-9090. - 41:2(2000), pp. 100-103.
Crystallisation kinetics of a 2·3Li2O. 1·1ZrO2.6·6SiO2 glass
Manfredini T.;Pellacani G. C.;Siligardi C.
2000
Abstract
The nucleation and growth of zircon (ZrSiO4) crystals on the free surface of a 2·3Li2O.1·1ZrO2.6·6 SiO2 glass was investigated through differential thermal analysis (DTA), x-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallisation was completed at about 860°C with an activation energy value corresponding to 740 kJmol-1. Samples with polished free surfaces were nucleated at selected temperatures in the range 640-690°C and then heated at 750°C for 30 rain for crystal growth. A dominant effect of surface nucleation was observed and the number of ZrSiO4 crystals per unit area and the mechanism of crystallisation were determined. It was concluded that the nucleation starts from a fixed number of surface nuclei which reach a maximum at 670°C corresponding to a zircon crystal number density of 1·33×1011 m-2 and that at 880°C a uniform surface crystalline layer was formed with a rate of growth of 1·93 μm min-1.
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