Scanning transmission microscopy

In NSR catalysts, the Ba-Pt interface plays an important role in the storage of NOx, which occurs by the formation of Ba(N03)2. Recent results [95] using scanning transmission microscopy (STM) and a model catalyst formed by deposition of a Ba thin films on Pt(lll) showed that, at room temperature, a film of Ba was formed with few individual Ba atoms, which were locally ordered. Upon annealing, particles are produced, of which atomic resolution is achieved with an atomic spacing consistent with the (111) plane of Ba. 

Scanning transmission microscopy STEM Microstructure and composition... 

STEM Scanning transmission microscopy Electron Electron (transmission) Polarization = 1 nm Crystallization in very fine regions (+ EDX, + EELS)... 

Surface morphology SEM, TEM, atomic force microscopy (AFM), scanning transmission microscopy (STM)... 

In the first scanning transmission microscopy experiment, a logarithmic dependence of the tunnel current on tip-sample separation was found. Calculate the tunnelling decay coefficient of this distance dependence, knowing that the sample was in platinum and the tip was made of tungsten, and that their work functions are 5.03 and 4.55 eV, respectively. 

Figure Bl.24.17. An example of scanning transmission ion microscopy (STIM) measurements of a human oral cancer cell. The different images indicate different windows in the energy of transmitted helium ions as indicated in the figure. White indicate areas of high counts. The teclmique offers a thickness scan through the sample, and, in this case, the cell walls of one specific cell can be seen in the areas dominated by thicker structures (data from C A Pineda, National Accelerator Centre, Fame, South Africa).

Blodgett films direct imaging by scanning tunneling microscopy and high-resolution transmission electron... 

Additional information on elastomer and SAN microstmcture is provided by C-nmr analysis (100). Rubber particle composition may be inferred from glass-transition data provided by thermal or mechanochemical analysis. Rubber particle morphology as obtained by transmission or scanning electron microscopy (101) is indicative of the ABS manufacturing process (77). (See Figs. 1 and 2.)... 

The very high powers of magnification afforded by the electron microscope, either scanning electron microscopy (sem) or scanning transmission electron microscopy (stem), are used for identification of items such as wood species, in technological studies of ancient metals or ceramics, and especially in the study of deterioration processes taking place in various types of art objects. 

Particle Size. Wet sieve analyses are commonly used in the 20 )J.m (using microsieves) to 150 )J.m size range. Sizes in the 1—10 )J.m range are analyzed by light-transmission Hquid-phase sedimentation, laser beam diffraction, or potentiometric variation methods. Electron microscopy is the only rehable procedure for characterizing submicrometer particles. Scanning electron microscopy is useful for characterizing particle shape, and the relation of particle shape to slurry stabiUty. 

Asbestos fiber identification can also be achieved through transmission or scanning electron microscopy (tern, sem) techniques which are especially usefiil with very short fibers, or with extremely small samples (see Microscopy). With appropriate peripheral instmmentation, these techniques can yield the elemental composition of the fibers using energy dispersive x-ray fluorescence, or the crystal stmcture from electron diffraction, selected area electron diffraction (saed). 

Occasionally, especially in the developmental phase of catalyst research, it is necessary to determine the oxidation state, exact location, and dispersion of various elements in the catalyst. Eor these studies, either transmission electron microscopy (TEM) or scanning electron microscopy (SEM) combined with various high vacuum x-ray, electron, and ion spectroscopies are used routinely. 

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