Preparation and properties of porous microspheres made from borate glass

Dysprosium lithium-borate glass microspheres and particles ranging from 45 to 150 mu m diameter, were reacted with a 0.25M phosphate solution at 37 degrees C, whose pH was either 3 or 8.8. The glass reacted nonuniformly and was converted into a porous, amorphous, hydrated, dysporium phosphate reaction product. The amorphous product had the same volume and shape (pseudomorphic) as the untreated glass, and could be dried without cracking. After heating at 300 C for 1 h, the amorphous reaction product had a specific surface area of approximate to 200 m(2)/g size of approximate to 30 nm, and nominal crushing strength approximate to 10 MPa. When the reaction product was heated to 600 degrees C for 15 min, the specific surface area decreased to approximate to 90 m(2)/g and the nominal crushing strength increased to 35 MPa Heating above 615 degrees C converted the amorphous dysprosium phosphate product into crystalline DyPO4, which contained open porosity until heated above 800 degrees C for 15 min. Highly porous materials of different chemical composition can be prepared by chemically reacting a borate-based glass with an aqueous solution at low-temperature (<100 degrees C). These highly porous materials are easy to process, and are considered candidates for controlled drug delivery, catalysis, chromatographic separation, filtration, and as bioactive materials (C) 2008 Wiley Periodicals, Inc. J Biomed Mater Res 88A: 531-542, 2009