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首页> 外文期刊>RSC Advances >Phase segregation in hydroxyfluorapatite solid solution at high temperatures studied by combined XRD/solid state NMR
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Phase segregation in hydroxyfluorapatite solid solution at high temperatures studied by combined XRD/solid state NMR

机译：结合XRD /固态NMR研究高温下羟基氟磷灰石固溶体中的相分离

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摘要

Fluoride substituted apatite is a key player among currently existing biomaterials. The F-19 MAS-NMR is perhaps the most and only reliable technique to detect fluoride substitution in apatite. Typically any F-19 MAS-NMR signal between -101.0 and -107.0 ppm is often used to identify fluoride substitution in apatite. Until now no explanation has been given as to why there is such a large variation in the NMR signals of these crystalline species. In this study, for the first time, we were able to explain this large variation in the F-19 chemical shift values often seen in the literature. Hydroxyfluorapatites (FHA) with varied fluoride substitution and free from other substitutions have been synthesized via solution route followed by heat treatment in air at different temperatures up to 900 degrees C. Solid-state nuclear magnetic resonance (F-19 and P-31 MAS-NMR) and X-ray diffraction (XRD) were used to characterize the synthesized powder samples. Formation of solid solution with varied hydroxyl/fluoride ratio was observed after the heat treatment up to a temperature of 300 degrees C. FHA samples decomposed to b-tricalcium phosphate (b-TCP) at higher temperature, which started from 20% F sample at 750 degrees C. With increasing F%, the FHA became more thermally stable and 80% F sample did not show b-TCP until 900 degrees C. An empirical nonlinear correlation between F-19 NMR chemical shift and relative F% had been established. The mechanism of FHA solid solution formation and its thermal instability is proposed.
机译：氟化物取代的磷灰石是当前现有生物材料中的关键角色。 F-19 MAS-NMR可能是检测磷灰石中氟化物取代的最可靠的技术。通常，通常使用-101.0和-107.0 ppm之间的任何F-19 MAS-NMR信号来鉴定磷灰石中的氟化物取代。到现在为止，还没有解释为什么这些晶体种类的NMR信号会有如此大的变化。在这项研究中，我们首次能够解释文献中经常出现的F-19化学位移值的这种大变化。已通过溶液途径合成氟代磷灰石（FHA），该氟代磷灰石具有多种氟取代基，并且没有其他取代基，然后在高达900摄氏度的不同温度下于空气中进行热处理。固态核磁共振（F-19和P-31 MAS- NMR和X射线衍射（XRD）用于表征合成的粉末样品。热处理至300摄氏度后，观察到形成了具有变化的羟基/氟化物比的固溶体。FHA样品在较高温度下分解为b-三磷酸三钙（b-TCP），其起始温度为20％F 750°C。随着F％的增加，FHA变得更加热稳定，而80％F的样品直到900°C才显示b-TCP。已经建立了F-19 NMR化学位移与相对F％之间的经验非线性关系。提出了FHA固溶体的形成机理及其热不稳定性。

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