Microstructural studies of glass-metal composites produced by ion-exchange and hydrogen treatments

Abstract

Detailed electron micrographic studies have been carried out on float glass surface subjected to sodium ⇋ copper ion-exchange in molten salts followed by a reduction treatment in hydrogen. Spherical copper particles of diameters ranging from 50 to 300 Å are formed in the glass matrix depending on the ion-exchange and reduction temperatures. The nucleus density of these particles is maximum at around 450°C. Phase separation in glasses whether incipient or induced by ion-exchange, increases considerably the nucleus density when such samples are subsequently reduced. This is ascribed to the increase in the number of copper atoms surrounding the nucleation sites in the phase separated glasses. The optical absorption spectra of the glass-metal composites show two bands, namely at 17 400 cm⁻¹ and 23 000 cm⁻¹ respectively. The absorption maxima for both the bands occur for specimens reduced at temperatures between 450 and 500°C corresponding to the temperature of maximum nucleus density. The bands at 17 400 cm⁻¹ and 23 000 cm⁻¹ are assigned to the conduction resonance and plasma resonance respectively as predicted by Maxwell-Garnet theory on aggregated metal systems dispersed in a dielectric matrix.