Electron diffraction pattern analysis

Stormer, H., Kleebe, H. J., Ziegler, G. (2007). Metastahle SiCN glass matrices studied by energy-filtered electron diffraction pattern analysis. Journal of Non-Crystalline Solids, 353(30-31), 2867-2877. doi 10.1016/j.jnoncrysol.2007.06.003. 

Although conventional electron-probe microanalysis appears to be unsuitable for analysis of the exposed surface layer of atoms in an alloy catalyst, recent developments have shown that X-ray emission analysis can still be used for this purpose (89, 90). By bombarding the surface with high energy electrons at grazing incidence, characteristic Ka radiation from monolayer quantities of both carbon and oxygen on an iron surface was observed. Simultaneously, information about the structure of the surface layer was obtained from the electron diffraction pattern. 

Analytical electron microscopy of individual catalyst particles provides much more information than just particle size and shape. The scanning transmission electron microscope (STEM) with analytical facilities allows chemical analysis and electron diffraction patterns to be obtained from areas on the order of lOnm in diameter. In this paper, examples of high spatial resolution chemical analysis by x-ray emission spectroscopy are drawn from supported Pd, bismuth and ferric molybdates, and ZSM-5 zeolite. 

Key words electron diffraction, structure analysis, geometrical analysis of electron diffraction patterns... 

Oblique texture electron diffraction patterns (Fig.7) are main experimental material for the electron diffraction structure analysis since they have a large number of reflections, so that only one pattern can provide an almost three dimensional set of diffraction reflections. The formation of textures in specimens is achieved by the use of orienting agents. As in the preparation of single crystal films, use can be made of orienting supports, mechanical action or even the application of an electrical field. Electron... 

However, quite complicated algorithms are needed for extracting the data Ifom texture patterns. The analysis of texture patterns must be performed in a different way compared to regular electron diffraction patterns, due to different geometrical settings. Firstly, the centre of the... 

The future for electron diffraction is very bright for two reasons. First, electron diffraction pattern can be reeorded seleetively from individual nanostrueture at sizes as small as a nanometer using the electron probe forming lenses and apertures, while eleetron imaging provides the selectivity. Second, electrons interact with matter mueh more strongly than X-ray and Neutron diffraction. These advantages, eoupled with quantitative analysis, enable the structure determination of small, nonperiodic, structures that was not possible before. 

A possible economically attractive alternative would be the production of acrylic acid in a single step process starting from the cheaper base material propane. In the nineteen nineties the Mitsubishi Chemical cooperation published a MoVTeNb-oxide, which could directly oxidise propane to acrylic acid in one step [6], Own preparations of this material yielded a highly crystalline substance. Careful analysis of single crystal electron diffraction patterns revealed that the MoVTeNb-oxide consists of two crystalline phases- a hexagonal so called K-Phase and an orthorhombic I-phase, which is the actual active catalyst phase, as could be shown by preparing the pure phases and testing them separately. 

Optical examination of etched polished surfaces or small particles can often identify compounds or different minerals hy shape, color, optical properties, and the response to various etching attempts. A semi-quantitative elemental analysis can he used for elements with atomic number greater than four by SEM equipped with X-ray fluorescence and various electron detectors. The electron probe microanalyzer and Auer microprobe also provide elemental analysis of small areas. The secondary ion mass spectroscope, laser microprobe mass analyzer, and Raman microprobe analyzer can identify elements, compounds, and molecules. Electron diffraction patterns can be obtained with the TEM to determine which crystalline compounds are present. Ferrography is used for the identification of wear particles in lubricating oils. 

X-ray or electron diffraction analyses are commonly employed to determine mineral species. In the case of biophosphates, these techniques are limited because the material is a complex mixture of organics and inorganics and furthermore the crystallites are small. Thus, resolution of X-ray diffraction pattern of bone and dentin material is rather poor. Electron diffraction pattern is generally better, but there is always the possibility of secondary alteration of the specimen during exposure. Other methods — such as infrared analysis — have their limitations too. In short, there are some analytical problems which may in part account for the conflicting interpretations offered in the literature. 

Experimental results. Some carbon fibre specimens reveal several orders of 001 particularly in electron diffraction patterns Figure 15 shows a plot of (3 against l2, equation (3), for an electron diffraction pattern from the skin region of a high-modulus material. L(oOl)> usually referred to as Lc, is 3.5 nm and a = 2%. A full description of electron-diffraction analysis in several similarly heterogeneous carbon fibres has been published (23). Figure 15 also includes a plot from the 001 electron diffraction profiles of a carbon whisker, an exceptionally perfect graphite material. This specimen, with an Lc of 10 nm, has zero distortion, and represents the only case where we have found no distortion in a fibrous specimen. 

Important data on the structure of the films were obtained in an analysis of electron diffraction patterns recorded directly in the transmission electron microscope. In all cases, the diffraction patterns had the form of diffuse halos, which indicate that nanoparticles are in the amorphous state [30]. The fact that the nanoparticles are amorphous is in all probability due to the exceedingly fast cooling of nanometer drops after the expansion of the plasma cloud. Estimates of the cooling rate of nanodrops at the instant of their hardening give values of up to 107K/sec. 

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