The Crystallization of Fluoroapatite Dumbbells from Supersaturated Aqueous Solution

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• 作者：Oleg Prymak ; Viktoriya Sokolova ; Thorsten Peitsch ; and Matthias Epple
• 刊名：Crystal Growth & Design
• 出版年：2006
• 出版时间：February 2006
• 年：2006
• 卷：6
• 期：2
• 页码：498 - 506
• 全文大小：1535K
• 年卷期：v.6,no.2(February 2006)
• ISSN：1528-7505

文摘

The crystallization of fluoroapatite is of importance because a number of biological systems makes use of this mineralin teeth (sharks) or for protection (molluscs). The crystallization of fluoroapatite was performed on titanium metal, on polymer(poly(ethylene-co-1,4-cyclohexane-dimethylene-terephthalate), PETG), and in a tubular reactor made of polytetrafluoroethylene (PTFE).A special morphogenesis leading to a distinct dumbbell-like morphology was observed. The morphology was clearly dependent onthe external parameters pH and supersaturation. Secondary parameters were the crystallization time, the ionic strength, and thestoichiometric ratios of calcium, phosphate, and fluoride. Dumbbells were only observed in the pH range of 5-7. Two differentgrowth mechanisms for fluoroapatite at a pH of 5-6 and a pH of 6-7 are proposed, based on branching hexagonal prisms and onbranching spikes, respectively. The presence of charged additives (cationic and anionic surfactants, poly(aspartic acid), polylysine)led to inhibition of the crystal growth, suggesting an electrostatic blocking of the crystal growth sites. An increase in the ionicstrength did not influence the crystal morphogenesis.