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Proceedings ArticleDOI

Effects of CaF2 vis-a-vis TiO2 as nucleating agent in SiO2–Al2O3–CaO glass-ceramics

03 Jun 2013-Vol. 1536, Iss: 1, pp 625-626

AbstractThe independent effects of CaF2 and TiO2 on the glass-ceramics based on SiO2–Al2O3–CaO system have been investigated. The crystallization behavior, microstructure, mechanical properties and chemical resistance of the glass-ceramics were studied by Differential Thermal Analysis (DTA), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), FTIR, mechanical and chemical resistance measurements. The CaF2 containing glass ceramics are found to be much superior to that of TiO2 containing glass ceramics on the basis of sintering strength, mechanical and chemical properties.

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Journal ArticleDOI
Abstract: Glasses based on the SiO 2 –Al 2 O 3 –MgO–K 2 O–B 2 O 3 –MgF 2 system added with TiO 2 were synthesized and characterized by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques. The results showed that by increasing the TiO 2 content, glass transition temperature ( T g ), both the crystallization peak temperature ( T p I and T p II ) and activation energy ( E ) increased. The interconnected large blocky card-like crystals were identified as fluorophlogopite as a major crystalline phase for all three glass-ceramic specimens by (XRD) and subsequently confirmed by SEM. The Vickers hardness ( H v ) value for glass-ceramic specimens decreases with progressively increasing TiO 2 content (1–10 wt%) and Titania containing MGT-3 glass-ceramic specimen with interconnected large blocky card-like fluorophlogopite mica crystals possess lower H v (4.26 GPa) as well as good machinability ( m = 0.12) useable for machinable applications. The study shows that Titania promoted initial crystallization of glass and can be used as an effective nucleting agent.

20 citations

Journal ArticleDOI
Abstract: The influence of MgF2 on the various properties like crystalline behavior, microstructure phases, hardness etc. in the SiO2-Al2O3-MgO-K2O-B2O3 glass system has been investigated. Three batches of glass system were synthesized and characterized by differential scanning calorimetry (DSC), coefficient of thermal expansion (CTE), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) equipped with energy dispersion X-ray spectroscopy (EDS). DSC study reveals that with the increase in MgF2 content the glass transition temperature (T-g) and first crystallization peak temperature (T-p(I)) decreased whilst the second crystallization peak temperature (T-p(II)) slightly increased. The CTE of the glasses is found to be in the ranges 634-6.40 x 10(-6) K-1 (50-400 degrees C). The activation energy (E-c) and frequency factor (v) both increase with increasing MgF2 content. The three-dimensional crystal growth is observed. The mica crystals are identified as fluorophlogopite, the predominant crystal phase for all the three glass specimens heat treated at 1050 degrees C. Vickers hardness values decrease with increasing amount of fluorine content and it gives better machinability. (C) 2015 Elsevier B.V. All rights reserved.

15 citations