High-resolution transition electron microscopy

Diffraction experiments with X-rays or neutrons, as well as high-resolution transition electron microscopy, showed that SiO (Patinal) is not crystalline on a length scale > 1 nm. However, areas with a different contrast were observed by HRTEM, indicating a local heterogeneity. From in situ crystallization experiments, the size of these areas can be estimated to be 1-2 nm. 

Transition metal oxides attract great interests mainly due to their redox nature, which is thought to be related with their flexible stmcture modiflcation under reductive and oxidative conditions. Such stmcture modiflcation takes place by forming so called crystallographic shear (CS) stmctures to accommodate anion vacancies in speciflc crystallographic planes by simultaneous shear displacement and crystal stmctural collapse [30-32]. High-resolution transmission electron microscopy (HRTEM) is a... 

Since the number of atoms on the surface of a bulk metal or metal oxide is extremely small compared to the number of atoms in the interior, bulk materials are often too costly to use in a catalytic process. One way to increase the effective surface area of a valuable catalytic material like a transition metal is to disperse it on a support. Figure 5.1.5 illustrates how Rh metal appears when it is supported as nanometer size crystallites on a silica carrier. High-resolution transmission electron microscopy reveals that metal crystallites, even as small as 10 nm, often expose the common low-index faces commonly associated with single crystals. However, the surface to volume ratio of the supported particles is many orders of magnitude higher than an equivalent amount of bulk metal. In fact, it is not uncommon to use catalysts with 1 nm sized metal particles where nearly every atom can be exposed to the reaction environment. 

Except for the fullerenes, carbon nanotubes, nanohoms, and schwarzites, porous carbons are usually disordered materials, and cannot at present be completely characterized experimentally. Methods such as X-ray and neutron scattering and high-resolution transmission electron microscopy (HRTEM) give partial structural information, but are not yet able to provide a complete description of the atomic structure. Nevertheless, atomistic models of carbons are needed in order to interpret experimental characterization data (adsorption isotherms, heats of adsorption, etc.). They are also a necessary ingredient of any theory or molecular simulation for the prediction of the behavior of adsorbed phases within carbons - including diffusion, adsorption, heat effects, phase transitions, and chemical reactivity. 

A variety of techniques has been used in the characterization of these materials. Superconducting transition temperatures and the magnetic susceptibility measurements (i.e., confirmation of the Meissner effect) are studied through the use of a SQUID magnetometer. Electric property characterization usually involves a simple measurement of the resistance of the sample. Finally, high-resolution transmission electron microscopy has also been widely employed in the characterization of these materials to aid in understanding their complex crystal structures. ... 

Another possible evidence of grafted organic/polymeric molecules onto CNT surface can be achieved by microscopy analyses using both principal types of electron microscopy - transition electron microscopy, TEM, or scanning electron microscopy, SEM (15,19,24,44,45,47). Such analyses are usually performed after careful extraction of the polymer from tubes by polymer solvents, performed several times by a reflux procedure with an excess of solvent therefore it is supposed that only covalently attached molecules remain fixed at CNT surface. High Resolution mode of TEM analysis shows the evidence of amorphous material on nanotubes surface (15). 

In the work reported in this chapter, oriented pyrolytic graphite was shock-loaded at pressures up to 15 GPa perpendicular or parallel to the basal plane of the graphite. The phase transitions of graphite to other carbon allotropes will be discussed using nanostructural data obtained by high-resolution electron microscopy (HREM). 

O Reilly W (1984) Rock and Mineral Magnetism. Blackie, Glasgow, London O Reilly W, Baneqee SK (1965) Cation distribution in titanomagnetites. Phys Lett 17 237-238 Otsuka N, Sato H (1986) Observation of the Verwey transition in Fe304 by high-resolution electron microscopy. J Solid State Chem 61 212-222... 

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