Electron microscope HRTEM

The size of Ti-Beta particles was determined with the high resolution transmission electron microscope (HRTEM). After 28 hours of hydrothermal treatment they grew to... 

The transmission electron microscopy (TEM) images of a two-layer Tl-1223 film are shown in Fig. 7.12, which confirms the epitaxial nature of the annealed electrodeposited films. All films showed a significant amount of intergrowth, as shown by a high-resolution transmission electron microscopic (HRTEM) measurement in Figs. 7.12c and d of a representative two-layer... 

In HRTEM, very thin samples can be treated as weak-phase objects (WPOs) whereby the image intensity can be correlated with the projected electrostatic potential of crystals, leading to atomic structural information. Furthermore, the detection of electron-stimulated XRE in the electron microscope (energy dispersive X-ray spectroscopy, or EDX, discussed in the following sections) permits simultaneous determination of chemical compositions of catalysts to the sub-nanometer level. Both the surface and bulk structures of catalysts can be investigated. 

Transmission electron microscopy (TEM/HRTEM) Topography Electron microscope... 

Mann, S. Cornell, R.M. Schwertmann, U. (1985) The influence of aluminium on iron oxides XII. High-resolution transmission electron microscopic (HRTEM) study of aluminous goethites. Clay Min. 20 255-262 Mann, S. Perry, C.C. Webb, J. Luke, B. Wil-liams, R.J.P. (1986) Structure, morphology, composition and organization of biogenic minerals in limpet teeth. Proc. R. Soc. Lond. 

Important ongoing developments in HRTEM that are expected to be valuable in catalysis research include the correction of spherical aberrations in electron microscope lenses and monochromatization of the electron beam for improvement of the spatial and spectral resolution. Recently, scanning-TEM (STEM) of atomically dispersed lanthanum atoms on alumina (63) has provided e.x situ aberration-corrected images, but it is noteworthy that there is no technical limitation in applying the correction devices to instruments used for making measurements of samples in reactive environments. 

Transmission electron microscopes (TEM) use a 100-keV electron gun and can study <50-nm-thick specimens, provide electron diffraction from them, and in the high-resolution TEM (HRTEM) version achieve a resolution below 0.05 nm and magnifications up to 5 x 107. One drawback of TEM is that the sample has to be thinned to not over 50 nm, to enable the electron beam to traverse the sample. 

Fig. 9.2. High Resolution Transmission Electron Microscopic (HRTEM) image of Au nanoparticles stabilized by dodecanethiol ligand molecules after SMAD and digestive ripening procedure. (Reprinted from Stoeva, S. et al J. Phys. Chem. B, 2003,107,7441-7448, Fig. 11(c), by permission of the American Chemical Society, copyright 2002, American Chemical Society.)...

HRTEM images were obtained on a Jeol JEM2010 ultra high-resolution analytical electron microscope equipped with an emission cathode operated at 200KV in bright field mode. The samples were examined with a magnification of 400,000. The ex situ treated samples were supported holey carbon coated copper grids for the experiment. 

The principles ofTEM and HRTEM have been discussed in several textbooks [6, 7]. A TEM column can be described using a ray diagram as shown in Figure 10.1, which is very similar to that for an optical microscope. The most important components in an electron microscope are the electron source (normally called the electron gun) and a group of electromagnetic lenses. 

Figure 39 HRTEM of a carbon nanotube whose inner cavity is filled with silver particles (lattice fringes correspond to [111] planes of Ag, d=0.23 nm). The tube cavity is first filled with molten silver nitrate that is subsequently reduced to metal by electron irradiation in situ, in the electron microscope.

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