Preparation and properties of porous microspheres made from borate glass

Dysprosium lithium‐borate glass microspheres and particles, ranging from 45 to 150 μm in diameter, were reacted with a 0.25 M phosphate solution at 37°C, whose pH was either 3 or 8.8. The glass reacted nonuniformly and was converted into a porous, amorphous, hydrated, dysprosium phosphate reaction product. The amorphous product had the same volume and shape (pseudomorphic) as the unreacted 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 ≈200 m 2 /g, a pore size of ≈30 nm, and nominal crushing strength of ≈10 MPa. When the reaction product was heated to 600°C for 15 min, the specific surface area decreased to ≈90 m 2 /g and the nominal crushing strength increased to 35 MPa. Heating above 615°C converted the amorphous dysprosium phosphate product into crystalline DyPO 4 , which contained open porosity until heated above 800°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°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. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009