Effect of Metal Ions of Chlorapatites on the Topotaxial Replacement by Hydroxyapatite under Hydrothermal Conditions
Effect of Metal Ions of Chlorapatites on the Topotaxial Replacement by Hydroxyapatite under Hydrothermal Conditions
复制标题
水热条件下氯磷灰石金属离子对羟基磷灰石顶轴置换的影响
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
S. Oishi
中科院分区：
文献类型：
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作者：
J. C. Rendón;K. Yanagisawa;N. Ishizawa;S. Oishi
摘要利用三种不同类型的氯磷灰石单晶，钙、锶和钡氯磷灰石，研究了氯磷灰石结构中的金属离子对向羟基磷灰石结构的拓扑转化的影响。在水热条件下，在300至800°C的温度范围内，在浓KOH溶液中，以3至96小时的间隔进行向羟基磷灰石结构的拓扑转化。钙和锶氯磷灰石晶体中的Cl−离子交换分别在500 ° C和700°C的6.25 M KOH溶液中完成，导致羟基磷灰石结构的形成。由于拓扑变换，变换的晶体保持其原始形状和尺寸。与此相反，拓扑转化率进一步降低的钡氯磷灰石晶体，含有大尺寸的金属离子，如Ba。即使在800°C下在10 M KOH溶液中，这些晶体也仅部分转化为羟基磷灰石。在这些条件下，观察到拓扑转化的钡羟基磷灰石层的离子种类的溶解，这导致新晶体在剩余的钡氯磷灰石晶体的表面上沉淀。新晶体的结构与六方磷灰石结构相匹配，但在结构中掺入了大量的K。
Abstract The effect of the metal ions in the chlorapatite structure on the topotaxial conversion to the hydroxyapatite structure was investigated, using three different types of chlorapatite single crystals, calcium, strontium, and barium chlorapatite. The topotaxial conversion to the hydroxyapatite structure was conducted under hydrothermal conditions at a range of temperature from 300 to 800°C for intervals between 3 and 96 h in concentrated KOH solutions. The Cl− ion exchange in the calcium and strontium chlorapatite crystals was completed at 500 and 700°C in a 6.25 M KOH solution, respectively, which resulted in the formation of hydroxyapatite structure. The transformed crystals retained their original shape and dimensions due to the topotaxial transformation. In contrast, the rate of the topotaxial conversion was further reduced on the barium chlorapatite crystals that contain metal ions with large size such as Ba. These crystals were only partially converted to hydroxyapatite even at 800°C in 10 M KOH solution. Under these conditions, a dissolution of ion species of the topotaxially converted barium hydroxyapatite layer was observed, which resulted in the precipitation of new crystals on the surface of the remaining barium chlorapatite crystals. The structure of the new crystals was matched with the hexagonal apatite structure, but a great amount of K was incorporated in the structure.