HIGH-RESOLUTION ELECTRON-MICROSCOPY OF NONSTOICHIOMETRIC APATITE CRYSTALS
HIGH-RESOLUTION ELECTRON-MICROSCOPY OF NONSTOICHIOMETRIC APATITE CRYSTALS
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DOI：
10.1002/ar.1092240217
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发表时间：
1989-06-01
影响因子：
--
通讯作者：
BARRY, JC
中科院分区：
文献类型：
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作者：
NELSON, DGA;BARRY, JC
应用高分辨电子显微镜、计算机图像处理和图像模拟技术对合成非化学计量比磷灰石进行研究，为磷灰石晶体生长机制提供了新的细节。在某些沉淀条件下，观察到具有明显的磷酸八钙（OCP）-磷灰石共生体的缺钙磷灰石。表面上具有OCP晶胞厚过度生长的磷灰石晶体证实了Brown（Nature 196：1048-1050）最初提出的逐步水解晶体生长机制。然而，许多晶体还包含一个中心的二维OCP包含一到两个单位细胞厚，嵌入磷灰石基质。在牙釉质、牙本质和骨磷灰石晶体中也观察到类似的平面缺陷。我们已经开发了一个修改后的版本布朗的逐步OCP水解磷灰石晶体生长机制来解释形成的晶体与OCP中心平面缺陷。该机制涉及OCP晶种的成核，该晶种生长直到其在OCP水解发生之前达到临界尺寸rh。磷灰石随后在OCP晶种上外延生长，从而将其嵌入磷灰石晶体的中心。磷灰石的生长是由平面缺陷产生的部分螺旋位错促进的。
The application of high resolution electron microscopy, computer image processing, and image simulation techniques to the investigation of synthetic nonstoichiometric apatites has provided new details of apatite crystal growth mechanisms. Under certain precipitation conditions, calcium‐deficient apatites with distinct octacalcium phosphate (OCP)‐apatite intergrowths have been observed. Apatite crystals with unit‐cell thick overgrowths of OCP on their surfaces confirmed the stepwise hydrolysis crystal growth mechanism initially proposed by Brown (Nature196:1048–1050). However, many crystals also contained a central two‐dimensional OCP inclusion one to two unit cells thick, embedded in an apatite matrix. Similar planar defects have been observed in dental enamel, dentin, and bone apatite crystals. We have developed a modified version of Brown's stepwise OCP hydrolysis apatite crystal growth mechanism to explain the formation of crystals with OCP central planar defects. The mechanism involves the nucleation of an OCP seed that grows until it reaches a critical size, rh, before OCP hydrolysis occurs. Apatite subsequently grows epitaxially on the OCP seed, thereby embedding it in the center of an apatite crystal. Apatite growth is facilitated by partial screw dislocations emanating from the planar defect.