title: Preparation and properties of porous microspheres made from borate glass.
abstract: Dysprosium lithium-borate glass microspheres and particles, ranging from 45 to 150 microm in diameter, were reacted with a 0.25 M 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, 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 degrees C for 1 h, the amorphous reaction product had a specific surface area of approximately 200 m(2)/g, a pore size of approximately 30 nm, and nominal crushing strength of approximately 10 MPa. When the reaction product was heated to 600 degrees C for 15 min, the specific surface area decreased to approximately 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 DyPO(4), 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.
authors.affiliation: Materials Science and Engineering Department, Graduate Center for Materials Research, Missouri University of Science and Technology, Rolla, Missouri 65409-1170, USA.
authors.forename: Samuel D
authors.initials: SD
authors.lastname: Conzone
authors.forename: Delbert E
authors.initials: DE
authors.lastname: Day
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D001881:Borates / Q000737:chemistry*; D019245:Compressive Strength; D016503:Drug Delivery Systems; D004419:Dysprosium / Q000737:chemistry*; D005898:Glass / Q000737:chemistry*; D006358:Hot Temperature; D008094:Lithium / Q000737:chemistry*; D008422:Materials Testing; D008863:Microspheres; D010316:Particle Size; D016062:Porosity; D013499:Surface Properties
chemical_list: D001672:Biocompatible Materials; D001881:Borates; C455467:dysprosium lithium borate glass; D004419:Dysprosium; D008094:Lithium