Heat‐Resistant Nonsilicate Porous Glasslike Material

Substitution of the end‐member oxides in the ternary sodium borosilicate system was studied. Replacing SO 2 with a combination of beat‐resistant oxides Ce, Hf, Th, and Zr (with or without La 2 O 3 and/or Y 2 O 3 ) 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 (CeO 2 ‐HfO 2 ‐La 2 O 3 ‐ThO 2 ‐Y 2 O 3 ‐ZrO 2 ), (CeO 2 ‐HfO 2 ‐La 2 O 3 ‐ThO 2 ‐ZrO 3 ), (CeO 2 ‐HfO 2 ‐ThO 2 ‐YZO 3 ‐ZrO 2 ), and (CeO 2 ‐HfO 2 ‐ThO 2 ‐ZrO 2 ) is predominantly glasslike. Some Na 2 O‐B 2 O 3 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 m 2 /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/dm 2 as well as a water resistance of 5.9 to 13.8 Na 2 O in mg/g was measured.