A High-Resolution Transmission Electron Microscopy Investigation on the Microstructure of Monoclinic Pyrophyllite from Qingtian, Zhejiang
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摘要: 采用X射线粉晶衍射 (XRD)、高分辨透射电镜 (HR-TEM) 及X射线荧光光谱 (XRF) 对青田叶腊石的矿物学特征进行了较为系统的研究。结果表明：叶腊石矿物颗粒微结构中最基本的构成单元为纳米板片，且该板片多呈聚集态，单层板片面积大小不一，厚度为 (8±2) nm。XRF分析结果表明青田叶腊石原矿混合物中SiO2与Al2O3的分子个数比为6.2，明显高于纯叶腊石中SiO2与Al2O3的分子个数比4.0。HR-TEM对叶腊石晶体结构的研究证实青田叶腊石具有典型的单斜晶系特征，该结论与叶腊石XRD结论一致；且XRD分析结果证实其伴生矿为石英，该结论与XRF所获得的青田叶腊石的“富硅”特征吻合。此外，叶腊石微结构中存在着较明显的晶体缺陷。在高能电子束辐照作用下，叶腊石晶体结构发生明显的破坏，并最终转变为非晶态结构。Abstract: The mineralogical characterizations of pyrophyllite from Qingtian were investigated using X-ray Diffraction (XRD), High-Resolution Transmission Electron Microscopy (HR-TEM) and X-ray Fluorescence Spectrometry (XRF). The results indicated that the pyrophyllite consists of a composite nanometer size lamina with irregular surface area, and the thickness is about (8±2) nm. XRF results show that the SiO2/Al2O3 molar ratio is 6.2, which is higher than the calculated one for an ideal pyrophyllite (ratio=4.0). The crystal system of pyrophyllite from the Qingtian deposit, obtained by HR-TEM analysis with powder, was monoclinic, which was consistent with the results obtained by XRD analysis. Quartz was the associated mineral in raw ore, consistent with the characteristic of the rich-Si feature detected by XRF analysis. In addition, it was clearly found that crystal defects exist in the microstructure of pyrophyllite. The high energy electron beam irradiation induced the changes in morphology of clay mineral particles, resulting in phase transformation from crystalline to amorphous.
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