Crystallization Behavior and Microstructure of Silica-Free 5K 2 O-45CaO-50P 2 O 5 Bioglass
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HENCH et al. first discovered the bioglass proposed of SiO2 (45 wt pct), CaO (24.5 wt pct), Na2O (24.5 wt pct), and P2O5 (6 wt pct) was used for bonegraft substitutes. Subsequently, many kinds of silicatebased bioactive glasses[2,3] and glass ceramics[4,5] have been developed, because glass-based materials can be prepared with the desired composition and structurally designed by controlling the phase(s) and size of the crystals precipitated after the crystallization treatment. These silicate-based glasses and glass ceramics have potential for use in long-term medical devices, because they are insoluble due to the use of SiO44 as a networkforming anion, although both locally and systematically the long-term reactions of such materials are still unknown.[6] Nagase et al.[7] examined the mortality of mice when a suspension of calcium phosphate glass containing silica (100Ca(PO3)2ÆxSiO2) dispersed in normal saline water was injected intraperitoneally and demonstrated that silica-free Ca(PO3)2 glass does not show any toxicity. [1]
MOO-CHIN WANG, Professor, is with the Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C. YOU-CHENG LAI, Student, and PING-YU SHIH, Professor, are with the Department of Materials Science and Engineering, National United University, Miaoli 36003, Taiwan, R.O.C. Contact e-mail: [email protected] WEI-JEN SHIH, Engineer, is with the Metal Industries Research & Development Centre, Kaohsiung 81160, Taiwan, R.O.C. GUO-JU CHEN, Associate Professor, is with the Department of Materials Science and Engineering, I-Shou University, Dashu Township, Kaohsiung County 840, Taiwan, R.O.C. WANG-LONG LI, Associate Professor, is with the Institute of Nanotechnology and Microsystems Engineering, National Cheng Kung University, Tainan 70101, Taiwan, R.O.C. Contact e-mail: [email protected] Manuscript submitted April 20, 2009. Article published online December 18, 2009 METALLURGICAL AND MATERIALS TRANSACTIONS A
Silica-free phosphate-based glass has been used as a biomaterial because its chemical composition is close to that of bone. However, Rawson[8] pointed out that to prepare CaO-P2O5 glass, a relatively low concentration of P2O5 is required. On the other hand, it is not easy to prepare calcium phosphate glass with a high P2O5/CaO ratio (molar ratio < 0.83) in the pyrophosphate region, because a very high temperature is required and crystallization tends to occur, as reported by Abe et al.[9] By applying a two-step thermal treatment to 45CaO-25TiO2-30P2O5 glass containing a few mole percent of Na2O, volume crystallization results in the formation of dense glass ceramics comprised of CaTi4(PO4)6 and b-Ca3(PO4)2, as reported by Hosono et al.[10] Moreover, Kasuga and Abe[11,12] have demonstrated that phosphate glasses are obtained in the region of P2O5/CaO 0.50 by introducing 10 mol pct of Na2O and TiO2. However, glass less than 1-mm thick still remains in the glass interior after crystallization, and this needs further sintering. Calcium phosphat
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