Effects of In-situ Generated Coinage Nanometals on Crystallization and Microstructure of Fluorophlogopite Mica Containing Glass-Ceramics

The effects of in-situ generated coinage nanometals (Cu, Ag and Au) on crystallization behavior, microstructure, thermal and mechanical properties of SiO2-MgO-Al2O3-B2O3-K2O-MgF2 (BMAPS) glass. ceramics were systematically studied-On addition of coinage nanometal, the glass transition temperature (T-g) is increased by 20-30 degrees C, crystallization temperature (T-c) by 30-50 degrees C and dilatometric softening temperature (T-d) by 10-25 degrees C. It was found that the density of Cu-containing glass was 2.59 g cm(-3) and for other glasses it was in the range of 2.56-2.57 g cm(-3). From the non-isothermal differential scanning calorimetry study, the activation energy of crystallization for BMAPS base glass was calculated as 344 kJ/mol, and changed to 406, 334 and 274 kJ/mol on addition of Cu, Ag and Au-nanometals, respectively. Crystals evolved in the opaque BMAPS glass-ceramics derived by controlled heat treatment, were identified as fluorophlogopite mica (KMg3(AlSi3O10)F-2) by X-ray diffraction (XRD) technique and confirmed by Fourier transformed infrared spectroscopy. Presences of copper, silver and gold nanometals were also identified by XRD technique. It is found from field emission scanning electron microscopy that the interlocked grain like microstructure developed in BMAPS glass. ceramics (being heat-treated at 1050 degrees C for 4 h) changed to denser house-of-cards like microstructure (containing smaller sized mica crystals) on addition of coinage nanometals. Density of BMAPS base glass-ceramic was 2.60 g cm(-3) and marginally changed to 2.61-2.62 g cm(-3) on addition of Cu, Ag and Au-nanometals. The change in microstructure resulted in the decrease of Vickers micro hardness value from 5.37 to 4.12, 4.20 and 4.58 GPa on addition of Cu, Ag and Au, respectively. Coinage nanometal doped mica glass-ceramics containing interlocked microstructure with higher thermal expansion coefficient, hence, is suitable for high temperature sealing application (like solid oxide fuel cell)