Microstructural characterization and wear properties of silver and gold nanoparticle doped K-Mg-Al-Si-O-F glass-ceramics

In ascertaining the effects of silver (Ag) and gold (Au) nanoparticles on crystallization of boro-alumino-silicate system; the K2O-MgO-Al2O3-SiO2-B2O3-F glasses doped with/without 0.2 wt% Ag- and Au- content were melt-quenched at 1550 °C. Doping of nanoparticles considerably increased the glass-transition temperature and softening point but decreased the thermal expansion. A sharp crystallization exotherm in differential scanning calorimetry (DSC) is observed at 750 °C ( ± 1 °C) for glass without nanoparticle and that broadened to 800–855 °C when contains nanoparticle. Opaque glass-ceramics were derived from the glasses by controlled heat-treatment at 1050 °C with predominant crystalline phase fluorophlogopite (KMg3AlSi3O10F2) mica. Traces of Ag- and Au- particles were also identified from X-ray diffraction (XRD) technique. The activation energy (Ec) of crystallization (344 ± 17 kJ/mol) is decreased to 233 ( ± 12) and 307 ( ± 15) kJ/mol (Kissinger method) on doping with Ag- and Au- nanoparticles, respectively. Compact microstructure (FESEM) composed of rock like and plate-like mica crystals are developed in base glass-ceramic and that gets restructured to interlocked type morphology in presence of Ag- nanoparticle. Significant microstructural change induced by nanoparticle addition caused the decrease in microhardness (4.31–4.66 GPa) and increase in thermal expansion. Friction and wear testing under reciprocative sliding (using WC-Co ball) exposed that the average coefficient of friction (COF) is 0.60 ± 0.2 for all glass-ceramics at 20 N load and 10 Hz frequency. At a lower load of 5 N, the average COF value is increased from 0.69 to 0.92 on use of Au-nanoparticle. A Similar trend was also observed at 10 N load as COF increased from 0.62 to 0.78.