Effects of M2+ (M = Ca, Sr, and Ba) Addition on Crystallization and Microstructure of SiO2-MgO-Al2O3-B2O3-K2O-F Glass

Mrinmoy Garai,Nibedita Sasmal,Basudeb Karmakar

doi:10.1155/2015/638341

Mrinmoy Garai, Nibedita Sasmal + Show 1 more

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https://doi.org/10.1155/2015/638341

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Abstract

In understanding the effect of K+ substitution by M2+ (M = Ca, Sr, and Ba) on crystallization and microstructural properties of boroaluminosilicate glass system, the SiO2-MgO-Al2O3-B2O3-MgF2-K2O-Li2O-AlPO4 glasses were prepared by single-step melt-quenching at 1500°C. Density of base glass (2.64 g·cm−3) is found to be decreased in presence of CaO and SrO. Tg is increased by 5–10°C and Td decreased by 13–20°C on addition of M2+. The variation of Tg, Td and decrease of thermal expansion (CTE) from 7.55 to 6.67–6.97 (×10−6/K, at 50–500°C) in substituting K+ by M2+ are attributed to the higher field-strength of Ca2+, Sr2+, and Ba2+. Opaque mica glass-ceramics were derived from the transparent boroaluminosilicate glasses by controlled heat treatment at 1050°C (duration = 4 h); and the predominant crystalline phase was identified as fluorophlogopite (KMg3AlSi3O10F2) by XRD and FTIR study. Glass-ceramic microstructure reveals that the platelike mica flake crystals predominate in presence of K2O and CaO but restructured to smaller droplet like spherical shaped mica on addition of SrO and BaO. Wide range of CTE values (9.54–13.38 × 10−6/K at 50–800°C) are obtained for such glass-ceramics. Having higher CTE value after crystallization, the CaO containing SiO2-MgO-Al2O3-B2O3-MgF2-K2O-Li2O-AlPO4 glass can be useful as SOFC sealing material.

Highlights

The development of high temperature sustainable material is an archetypal challenge to materials science researchers since the last decade
The glass based on SiO2-MgO-Al2O3-K2O-F system is converted to glass-ceramic containing fluorophlogopite mica (KMg3AlSi3O10F2) through the process of heterogeneous phase separation, precipitation of primary crystalline nuclei, and the formation of metastable and stable phases from these nuclei [1–3]
We report the comparative study of MO addition in SMAKBF glasses by characterizing the techniques of dilatometry, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), EDX, and Fourier transformed infrared (FTIR) spectroscopy

Summary

Introduction

The development of high temperature sustainable material is an archetypal challenge to materials science researchers since the last decade. CTE (×10−6/K) (50–500∘C) 7.55 6.97 6.79 6.67 phases and by that of the residual glassy phase and sealing glass’s and glass-ceramic’s elastic properties Tarlakov and his coworkers [5] investigated the effects of CaO addition on the glass structure and crystallization mechanism of Li2O-CaO-SiO2 system. Hamzawy and Darwish [6] established that the substitution of Ca for Mg in stoichiometric Na-fluorophlogopite decreases the glass transformation temperature and increases the crystallization range (Tc) and thermal expansion values They [6] accomplished that the crystallization at CaO/MgO molar ratio = 0.25 in the base glass did not enhance the formation of Na-fluorophlogopite phase but catalysed the development of fluororichterite with cristobalite crystals. The increase of nonbridging oxygen (O−) and network strength (Si-O-Si) play significant role in controlling the physical and thermal properties Yazawa and his coworkers [10] successfully prepared the alkali-resistant porous glass in SiO2-B2O3ZrO2-RO system to ascertain the effects of MgO, CaO, SrO, BaO, and ZnO (RO). We report the comparative study of MO addition in SMAKBF glasses by characterizing the techniques of dilatometry, XRD, FESEM, EDX, and FTIR spectroscopy

Experimental

Results and Discussion

Conclusions