Heat-Resistant Nonsilicate Porous Glasslike Material

Abstract

Substitution of the end-member oxides in the ternary sodium borosilicate system was studied. Replacing SO2 with a combination of beat-resistant oxides Ce, Hf, Th, and Zr (with or without La2O3 and/or Y2O3) was found to produce glasses (droplet like phases present), which after heat treatment decomposed into two immiscible microphases (coarsening process) of which one is water-soluble. The structure of the leached materials or the materials sintered after leaching (CeO2-HfO2-La2O3-ThO2-Y2O3-ZrO2), (CeO2-HfO2-La2O3-ThO2-ZrO3), (CeO2-HfO2-ThO2-YZO3-ZrO2), and (CeO2-HfO2-ThO2-ZrO2) is predominantly glasslike. Some Na2O-B2O3 may be expected to remain unleached in the pores, as has been observed for silica-based materials. However, no evidence for this was found during X-ray diffraction analysis and therefore any such presence if crystalline must be below 1%. The new glasslike materials have a higher sintering temperature (1520°C) than porous silica glass (900° to 1200°C). The specific surface area of the leached glasslike materials is 93.7 to 295.8 m2/g and an average pore radius of 0.4 to 7.3 nm was calculated, A favorable alkali resistance of 5.12 × 10−3 to 1.36 × 10−2 mg/dm2 as well as a water resistance of 5.9 to 13.8 Na2O in mg/g was measured.