Abstract
Porous glass prepared by acid leaching of phase-separated sodium borosilicate glass usually contains colloidal silica particles which originate from the silica component of the borate phase. When the colloidal silica fills the pores in the silica skeleton, the pore volume is reduced and the mass transport through the porous glass is prevented. In order to obtain the porous glass with high pore volume, the effects of the sample diameter and the concentration of leaching acid on the formation of colloidal silica were studied. With decreasing sample diameter, the dissolution of silica during leaching increased and the precipitation of colloidal silica decreased, and accordingly the pore volume increased. Similarly the pore volume increased with decreasing concentration of the leaching acid. By washing with acid solution both colloidal silica and the skeleton were dissolved, and the pore volume increased. These results indicate a method to obtain porous glass with high pore volume.
