Transformation of Na2O-CeO2-B2O3 glass into a material with interconnected pores

Substitution of SiO₂ with CeO₂ in the ternary sodium borosilicate system was found to produce phase-separable glasses. Heat treatment of these glasses resulted in separation into two different phases. The one phase enriched in sodium borate was then leached out leaving a CeO₂-rich framework. The structure of the leached material was crystalline (Pt/Rh crucible melt) which changed to a rather net-like appearance if Al₂O₃ resulting from erosion of alumina crucibles was added. B₂O₃ remained partially in the insoluble CeO₂-skeleton. X-ray diffraction analysis of leached material proved the presence of crystalline cubic CeO₂ and cerium borate (metaborate of the aragonite type) in Pt/Rh crucible melts, whereas cubic CeO₂, 2Al₂O₃ · B₂O₃ and traces of sodium borate were detected in Al₂O₃ containing melts. The specific surface areas of the leached materials ranged between 25 and 120m²g^–1 while the main radii of interconnected pores were calculated to be between 0.5 and 17nm. A sintering temperature of about 1500° C was estimated from void volume and bulk density measurements.