Ion-Exchange Treatment of Glass Surface in NaNO₃-TlNO₃ Molten Salt

Abstract

To make functional glasses, ion-exchange treatment of the glass surface was carried out in TlNO₃-NaNO₃ molten salt at 673 K and 723 K for various time periods, and then the Tl ions embedded in the glass were reduced to metallic Tl nanoparticles by hydrogen gas. The color of the glass containing metallic Tl nanoparticles changed to brown or black. The Tl nanoparticles were detected by a qualitative TEM analysis. The optical absorption spectra of these treated glasses showed a peak at about 370 nm. With increases in the temperature of the molten salt, the band intensity of the absorption is enhanced. The absorption increase may correspond to larger particle sizes and densities with the increase in temperature. The Tl nanoparticles with 10–150 nm diameter were observed at neighboring parts of the glass surface by TEM and FE-SEM.