ISSN:
0021-9304
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Medizin
,
Technik allgemein
Notizen:
Crystallization kinetics studies for six experimental glass formulations in the system Na2O-CaO-SiO2-P2O5 synthesized by wet chemistry were conducted by means of differential thermal analysis. These glasses had CaO/P2O5 and SiO2/(CaO + Na2O) 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/P2O5 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 (CaSiO3), Na2CaSi3O9, combeite [Na4Ca3SI6O16(OH)2], and some unidentifiable phases. Two of the six bioceramic materials had a mixture of unknown crystalline phases. © 1996 John Wiley & Sons, Inc.
Zusätzliches Material:
13 Ill.
Materialart:
Digitale Medien
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