Microstructure-mechanical properties of Ag0/Au0doped K-Mg-Al-Si-O-F glass-ceramics

Abstract

In understanding the catalytic efficacy of silver (Ag0) and gold (Au0) nanoparticles (NPs) on glass-ceramic (GC) crystallization, the microstructure-machinability correlation of a SiO2-MgO-Al2O3-B2O3-K2O-MgF2system is studied. The thermal parametersviz., glass transition temperature (Tg) and crystallization temperature (Tc) were extensively changed by varying NPs (in situorex situ). Tc was found to be increased (Tc= 870-875 °C) by 90-110 °C whenex situNPs were present in the glass system. Under controlled heat-treatment at 950 ± 10 °C, the glasses were converted into glass-ceramics with the predominant presence of crystalline phase (XRD) fluorophlogopite mica, [KMg3(AlSi3O10)F2]. Along with the secondary phase enstatite (MgSiO3), the presence of Ag and Au particles (FCC system) were identified by XRD. A microstructure containing spherical crystallite precipitates (∼50-400 nm) has been observed through FESEM inin situdoped GCs. Anex situAg doped GC matrix composed of rock-like and plate-like crystallites mostly of size 1-3 μm ensured its superior machinability. Vicker's and Knoop microhardness ofin situdoped GCs were estimated within the range 4.45-4.61 GPa which is reduced to 4.21-4.34 GPa in theex situAg system. Machinability of GCs was found to be in the order,ex situAg >ex situAu ∼in situAg >in situAu. Thus, theex situAg/Au doped SiO2-MgO-Al2O3-B2O3-K2O-MgF2GC has potential for use as a machinable glass-ceramic.