Garai, Mrinmoy and Sasmal, Nibedita and Molla, Atiar Rahaman and Karmakar, Basudeb (2015) Structural effects of Zn+2/Mg+2 ratios on crystallization characteristics and microstructure of fluorophlogopite mica-containing glass-ceramics. Solid State Sciences, 44. pp. 10-21. ISSN 1293-2558

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Abstract

We report the effect of Mg+2 substitution (by Zn+2) on crystallization kinetics, microstructure, thermal and mechanical properties of boroaluminosilicate glass. Zn2+ was selected for Mg2+ on the basis of similar ionic radius in six coordination system (Mg2+similar to 0.72 angstrom, Zn2+similar to 0.75 angstrom). The melt-quenched glasses with SiO2-(1 - x) MgO-Al2O3-K2O-B2O3-MgF2 (BPAS)/x ZnO system, have been investigated to establish the effect of Zn+2/Mg+2 ratios. It is found that the density of BPAS glass without zinc content is 2.52 g/cm(3) and increased linearly on substitution of Mg2+ by 5-32 mol% ZnO. T-g and T-d of BPAS glass initially increased on adding 5 mol% ZnO and then decreased on further addition. From DSC study, it is found that the crystallization exotherm changes significantly in the temperature range 750-1000 degrees C, where different crystalline phases are formed, and the activation energy of crystallization (E-C) varies in the range of 254-388 kJ/mol. The crystalline phases formed in opaque BPAS glass-ceramic, derived by controlled heat treatment at 800 and 1050 degrees C (4 h), are identified as fluorophlogopite KMg3(AlSi3O10)F-2] mica and willemite (Zn2SiO4) by XRD technique, and confirmed by FTIR spectroscopy. The change of crystallization phenomena varying Zn+2/Mg+2 ratios correspond to significant microstructural change. A wide range of thermal expansion (CTE) values are obtained for the BPAS glasses and corresponding glass-ceramics. CTE (50-500 degrees C) of BPAS glass without zinc content is 7.76 x 10(-6)/K, and decreased sequentially on increasing Zn+2/Mg+2 ratio. The density of glass-ceramics after heating at 800 and 1050 degrees C increased linearly with increasing Zn+2 substitution for Mg+2. Microhardness of the BPAS glasses is in the range of 4.26-6.15 GPa and found to be increased to 4.58-6.78 GPa after crystallized at 1050 degrees C. (C) 2015 Elsevier Masson SAS. All rights reserved.

Item Type:	Article
Subjects:	Glass
Divisions:	Glass
Depositing User:	Bidhan Chaudhuri
Date Deposited:	29 Dec 2015 11:29
Last Modified:	29 Dec 2015 11:29
URI:	http://cgcri.csircentral.net/id/eprint/2985

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