树脂包埋在透射电子显微镜测试中的应用

在环氧树脂包埋样品的过程中,部分样品易漂浮于树脂中而不易定位,因而影响了技术人员超薄切片的效率及样品在透射电子显微镜下的观察效果.对易漂浮于环氧树脂中的样品进行多次包埋定位,再通过修块、切片等步骤制备透射电子显微镜截面样品,特别适用于快速高效地制备纳米线、棒等截面样品.多次包埋方法操作简单、实用性强,经超薄切片后制备出的样品截面更清晰、更完整.     

扫描透射电子显微镜技术及其在中药研究中的应用

扫描透射电子显微镜(STEM)兼具透射电子显微镜(TEM)和扫描电子显微镜(SEM)的优势,具有高分辨成像、强原子衬度敏感以及图像易懂、直观等优点,已成为材料微结构和微区分析的必要性工具. 中药研究有着悠久历史,显微技术一直是研究药材微特征和作用机制的重要手段之一,具有其他手段不可替代的作用. 综述了STEM的原理、方法、技术特点,以及其在中药显微结构和纳米颗粒等方面的应用,以期为进一步扩展中药微特征领域的研究作参考.     

透射电子显微镜

<正>日本电子JEM100-CXⅡ型透射电子显微镜透射电子显微镜(TEM)在材料科学、生物学上应用较多。由于投射电镜具有高分辨率、高性能,可应用于材料科学如物理、化学、化工、冶金、材料、半导体、地质、石油、纺织、轻工、考古、航天、外贸等方面的成分和结构分析;在生命科学如生物学、医学、药学、法医学、农业、林业,畜牧业,水产,环保,食品等方面进行生化物质定位。日本电子JEM100-CXⅡ型透射电子显微镜的晶格分辨率为2.04,最大放大倍率为20万倍,最大加速电压为100 kV。利用该仪器,可以观察纳米材料的粒径大小及分布、颗粒形貌,也可以     

基于透射电子显微镜的沸石分子筛结构研究进展

透射电子显微镜是解析沸石分子筛新结构、 分析结构缺陷和研究活性位点等的有力工具. 应用于分子筛研究的透射电子显微术总体上可以分为图像法和衍射法, 包括透射电子显微镜和扫描透射电子显微图像、 选区电子衍射和三维电子衍射, 通常结合其中的几种方法进行分析. 近年来, 随着电子显微镜硬件性能的不断提升, 特别是球差矫正器的广泛应用及各种适用于分子筛等电子束敏感材料的探测器和图像处理技术的不断革新, 在原子尺度观察分子筛的结构已成为可能. 此外, 利用原位电子显微镜技术研究分子筛的生长和催化反应机理也在逐步展开. 本文按电子显微镜方法分类, 综述了近些年基于电子显微镜的分子筛研究, 包括新结构解析、 手性确认和金属负载等的最新进展.     

粉末样品制备方法对扫描电子显微镜成像质量的影响

纳米粉末材料是化学化工领域常见的样品,在其扫描电子显微镜表征中,通常会遇到以下几个问题：二次电子产率低,粉末聚集结块从而导致无法观察纳米形貌,以及荷电效应等.以二氧化硅小球粉末、ZSM-5分子筛纳米片以及聚苯乙烯小球粉末为研究对象,在不镀金属膜的前提下,分别采用粉末直接涂抹在导电碳胶或银胶上和溶液分散后滴涂在不同基底上的方法进行样品制备,比较了直接涂抹和分散后滴涂在基底上两种方法对扫描电子显微镜成像的影响.结果表明,样品经过溶液分散能够有效的减小粉末的团聚,其中,滴涂在硅片基底上可以减小荷电效应和背景影响,清晰观察到粉末的纳米级形貌.     

CM200透射电子显微镜保护关机的故障分析及维修

介绍了CM200透射电子显微镜电镜保护(LPR)的工作原理,分析了电镜保护关机的故障原因并介绍了几个维修实例.     

JEM-2100PLUS透射电子显微镜操作方法与技巧及常见故障排除

以JEM-2100PLUS透射电子显微镜为例,介绍了电镜的基本结构、操作面板和成像原理。使用透射电子显微镜的最终目的就是要得到高质量的照片,结合透射电镜的操作步骤,总结了如何拍摄高质量的照片以及常见故障排除方法。     

扫描电子显微镜对样品的要求及样品的制备

扫描电子显微镜对样品的要求很严,要求样品必须是固体,且做到五无:无毒、无放射性、无污染、无磁、无水分,成分稳定,块状样品大小要适中,粉末样品要进行特殊处理,对不导电和导电性能差的样品要进行镀膜,且要选择适当的镀膜仪,方能达到理想的分析效果.     

High-Resolution Transmission Electron Microscopy Re-examined as a Tool in Solid State Chemistry

Transmission electron microscopy (TEM) can be used with crystalline solids to obtain direct images of small structural groups comprising a few coordination polyhedra with resolution nearly down to atomic scale (“lattice imaging”). More exact knowledge of the conditions required for direct imaging, as well as improvements in the instruments themselves, have now made it possible to examine very small defect regions (microdomains), faults in the stacking sequence of structural groups or atom layers (planar or Wadsley defects), and isolated defects in narrowly delimited areas that may actually be below the dimensions of the unit cell. The structural principle of the very smallest ordered regions can even be determined when X-ray structure analysis proves unable to do this. “Block structures” are particularly suitable as models for the testing and further development of the high-resolution method; the detection of three-dimensional, two-dimensional, and one-dimensional defects has been studied on such structures.     

透射电镜三维重构确定金纳米粒子的立体结构

贵金属纳米颗粒具有局域表面等离激元这一特性使其具有丰富的光学性质,而这一特性受制于纳米颗粒所形成的立体几何形状,而透射电镜和扫描电镜的二维图像不能真切地观测和确定纳米颗粒所形成的立体几何结构。透射电镜三维重构技术可作为一种确定纳米颗粒立体结构的直观有效的方法。本文利用透射电镜的三维重构技术,选择合适的参数进行二维图像的采集、图像匹配对中及重构、立体模型的构建,从而通过构建的模型对两种金纳米颗粒样品的不同几何形状所产生的边界形态进行了确认和分析。     

Fluctuation Transmission Electron Microscopy: Detecting Nanoscale Order in Disordered Structures

The structures of many disordered materials are not ideally random, but contain structural order on the scale of 1–3 nm. However, such nanoscale order, called medium‐range order, cannot be detected by conventional diffraction methods in most cases. Fluctuation transmission electron microscopy (FTEM) has the capability to detect medium‐range order in disordered materials based on statistical analysis of nanodiffraction patterns or dark‐field images from TEM. FTEM has been successful in demonstrating the theoretically predicted development of nanoscale nuclei in amorphous chalcogenides, as well as in revealing the subtle effect of different preparation routes on the medium‐range order in amorphous semiconductors and metals. The fluctuation principle can also be applied to study structural order on longer length scales in polymers and other disordered materials using X‐rays or visible light. Further advances in theory and practice of FTEM will greatly increase our understanding of amorphous structures and nucleation phenomena.     

电子显微镜下的纳米世界

以高中阶段知识为基础,简述了扫描电子显微镜、透射电子显微镜等电镜技术的发展和基本原理,并以实际应用案例介绍了电镜技术在纳米科学领域的应用,最后给出了电镜技术的未来发展前景。     

Electron Diffraction with the Transmission Electron Microscope as a Phase-Determining Diffractometer—From Spatial Frequency Filtering to the Three-Dimensional Structure Analysis of Ribosomes

Chemists recognize X-ray crystal structure analysis and electron microscopy as powerful methods of analysis. In the last 20 years the basic ideas of X-ray diffraction analysis have been extended to the field of electron microscopy, whereby an image-forming apparatus is converted into an electron diffractometer, and through which an old dream of crystallographers can be realized—the measurement of the phase shift of scattered waves, a prerequisite for the direct calculation of structures. Its most important area of application, like that of the X-ray diffractometer, is in three-dimensional structure analysis—in all fields of science. However, beyond crystallography, aperiodic structures (comparable to crystals with a single unit cell) can also be analyzed three-dimensionally. In this progress report, the development of the first idea (spatial frequency filtering) to the analysis of ribosomal particles is outlined. Attention will be focused primarily on quantitative methods for the measurement of scattered rays, which are also usable beyond the conventional limit of resolution, down to atomic resolution. In the course of this work in 1968, the principle of the three-dimensional analysis of native biological crystal structures using the electron microscope, as worked with today in many laboratories, was developed. In Munich, however, further research focused on the three-dimensional analysis of aperiodic and individual (especially biological) objects. The analysis of 50S-subunits of the procaryotic ribosome of E. coli showed surprisingly good reproducibility of the results (although only within the same orientation), allowing the deduction of almost ideal average model structures from a limited number of particles.     

Microdeformation in Heterogeneous Polymers,Revealed by Electron Microscopy

Recent investigations of the tensile fracture behaviour of representative glassy and semicrystalline impact-resistant polymers are reviewed, with emphasis on the microdeformation behaviour as revealed by electron microscopy of sections from bulk specimens, where the crack-tip damage zone has been embedded and/or stained under load, and on thin films deformed in situ. The insight that such techniques have provided into the toughening mechanisms is discussed.     

The Cross‐Sectional Structure of Vanadium Oxide Nanotubes Studied by Transmission Electron Microscopy and Electron Spectroscopic Imaging

Vanadium oxide nanotubes (VO_x‐NTs) are easily accessible in pure form from vanadium(V) alkoxides and amines by a sol‐gel reaction and a subsequent hydrothermal treatment. The wall structure of VO_x‐NTs containing hexadecylamine or dodecylamine as the structure‐directing template has been characterised by transmission electron microscopy (TEM). A standard method for preparing TEM specimens was modified in order to investigate the cross‐sectional structure of the tubes. The elemental distribution in the layered structure inside the tube walls has been visualised by electron spectroscopic imaging: vanadium oxide builds up the layers that appear with dark contrast in the TEM images while carbon, i. e., the organic template, is present in between. The bent VO_x layers inside the tube walls are preferentially scrolls rather than concentric cylinders. Moreover, some tubes are formed by a combination of both types. The layer structure inside the tube walls is frequently disordered, and several types of defects appear.     

Orientation Imaging Microscopy for the Transmission Electron Microscope

The resolution limit of Orientation Imaging Microscopy in the Scanning Electron Microscope is between 20 nA and 80 nA depending on the basic resolution/beam current performance of the SEM, the sample atomic number and the level of residual strain within it. The newer technique of orientation imaging in the transmission electron microscope, TEM, improves on this resolution limit by a factor of five to ten. The new technique is based on a novel procedure for determining the crystallography of separate small volumes in the sample by examination of a large series of dark field images. Each image is recorded for a different diffraction condition. This is achieved by using a computer to direct the electron beam onto the same area of the sample so that it covers all directions within a cone of semi-apex angle 3 degrees. Analysis of the intensity of the same point in each of the dark field images permits reconstruction of a diffraction pattern for that point providing the data to calculate its crystal orientation. The process is repeated for each point in the image. The Orientation Image Micrograph is constructed from the orientations so determined. The technique is shown to be capable of producing orientation micrographs of high spatial resolution for unstrained samples. For highly strained samples difficulties are encountered in accurately indexing the complicated diffraction patterns that are observed. Methods to improve the indexing procedures involve determining the sub-cell structure first from a comparison of patterns from adjacent pixels and then summing all patterns belonging to a single sub-cell. The resultant improvement in pattern quality permits more reliable determination of orientation. Examples of this procedure are taken from studies of deformed aluminum.     

电子显微技术应用于生物纳米材料表征与测试的研究进展

该文简述了电子显微技术的发展历程,并介绍了现代电子显微镜的新功能。针对生物纳米材料理化性能与功能应用的特殊性,结合研究实例,重点阐述运用电子显微结构表征与原位分析测试技术指导构建新颖纳米结构、揭示材料与细胞/组织相互作用并发挥功能的机制。并在此基础上,展望了电子显微技术在生物纳米材料研究领域的发展方向(大尺寸图像拼接、三维重构、动态原位实时成像)。