Crystallization of experimental bioactive glass compositions

✍ Scribed by Rizkalla, A. S. ;Jones, D. W. ;Clarke, D. B. ;Hall, G. C.

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 420 KB
• Volume: 32
• Category: Article
• ISSN: 0021-9304
• DOI: 10.1002/(sici)1097-4636(199609)32:1<119::aid-jbm14>3.0.co;2-h

✦ Synopsis

Crystallization kinetics studies for six experimental glass formulations in the system NazO-CaO-Si02-P,0, synthesized by wet chemistry were conducted by means of differential thermal analysis. These glasses had CaO/P,OS and SiOJ (CaO + NazO) ratios ranging from 8.74-3.38 and 0.92-3.03, respectively. Samples of each glass (n = 30 were heated from 23 to 1250°C under N2 atmosphere at heating rates ranging from 10 to 50"C/min. Glass-ceramics were obtained after heat treating the initial glasses at temperatures determined from their DTA exotherms. The activation energy of crystallization for each glass composition was calculated from an expression-relating log-heating rate and the reciprocal of the exothermic peak temperature. The compositions of the six glasses were significantly different ( p = 0.05). The activation energy of crystallization (Q) values ranged from 196 to 782 kJ/mole. A correlation was obtained between Q and CaO/P20s and between Q and the Young's modulus ( p < 0.001). Two of the six glasses exhibited bulk crystallization. X-ray diffraction studies showed that four of the six glasses exhibited different proportions of crystalline phases following heat treatment. These phases were wollastonite (CaSiOJ, Na2CaSi309, combeite [Na4Ca3S16016(OH),], and some unidentifiable phases. Two of the six bioceramic materials had a mixture of unknown crystalline phases.