HRTEM images structures

Similar results were found by Bacsa el al. [26] for cathode core material. Raman scattering spectra were reported by these authors for material shown in these figures, and these results are discussed below. Their HRTEM images showed that heating core material in air induces a clear reduction in the relative abundance of the carbon nanoparticles. The Raman spectrum of these nanoparticles would be expected to resemble an intermediate between a strongly disordered carbon black synthesized at 850°C (Fig. 2d) and that of carbon black graphitized in an inert atmosphere at 2820°C (Fig. 2c). As discussed above in section 2, the small particle size, as well as structural disorder in the small particles (dia. —200 A), activates the D-band Raman scattering near 1350 cm . ... 

Ag-core/Au-shell bimetallic nanoparticles were prepared by NaBH4 reduction method [124]. UV-Vis spectra were recorded and compared with various ratios of AuAg alloy nanoparticles. The UV-Vis spectra of bimetallic nanoparticles suggested the formation of core/shell structure. Furthermore, the high-resolution transmission electron microscopy (HRTEM) image of the nanoparticles confirmed the core/shell type configuration directly. 

It is noteworthy that the HRTEM cannot distinguish core and shell even by combining X-ray or electron diffraction techniques for some small nanoparticles. If the shell epitaxially grows on the core in the case of two kinds of metals with same crystal type and little difference of lattice constant, the precise structure of the bimetallic nanoparticles cannot be well characterized by the present technique. Hodak et al. [153] investigated Au-core/Ag-shell or Ag-core/Au-shell bimetallic nanoparticles. They confirmed that Au shell forms on Ag core by the epitaxial growth. In the TEM observations, the core/shell structures of Ag/Au nanoparticles are not clear even in the HRTEM images in this case (Figure 7). 

Figure 4. TEM images of the (a) Pt cubes, (b) Pt cuboctahedra, and (c) Pt octahedra. Inset images are corresponding HRTEM images and ideal structural models [15]. (Reprinted from Ref. [15], 2005, with permission from American Chemical Society.)...

Figure 2. HRTEM image analysis, a raw HKTEM image b corresponding skeletonized image c limits of a coherent domain, definition of the structural (L, La, Lc, d) and microtextural (a) parameters N is the number of layers stacked within a domain.

Table. Structural data from computer analysis of the HRTEM images obtained on carbon aerogels formed by pyrolysis at 1050 and 2600°C ofNa2(CO)3 and Ca(OH)2 based aerogels heated.

For both structures, all final Si positions were obtained with reasonable accuracy (0.1 -0.2 A) by a 3D reconstruction of HRTEM images followed by a distance least-squares refinement. This kind of accuracy is sufficient for normal property analysis, such as catalysis, adsorption and separation, and as a starting point for structure refinement with X-ray powder diffraction data. The technique demonstrated here is general and can be applied not only to zeolites, but also to other complicated crystal structures. 

Figure 2. On the left hand side is the HRTEM image of Ti-Beta nanoparticles obtained from the colloidal solution that was thermally treated for 28 hours. In the inset a selected area electron diffraction ofTi-Beta nanpoarticles shows their crystalline structure. On the right hand side are the 29Si MAS and H - 29Si CPMAS spectra of the sample g).

Fig. 3. HRTEM atomic structure image of germanium silicalite (GeSi04) in which there are channels of aperture diameter 0.55 nm running along the [010] direction. Inset shows the 5- and 6-membered smaller apertures that are circumjacent to larger (0.55 nm) channels (5).

Fig. 8. HRTEM image of FAU/EMT intergrowths viewed along the [110] direction. The stackings ABC... and AB... correspond to the FAU and EMT end-member structures, respectively (5).

The electron crystallography method (21) has been used to characterize three-dimensional structures of siliceous mesoporous catalyst materials, and the three-dimensional structural solutions of MCM-48 (mentioned above) and of SBA-1, -6, and -16. The method gives a unique structural solution through the Fourier sum of the three-dimensional structure factors, both amplitude and phases, obtained from Fourier analysis of a set of HRTEM images. The topological nature of the siliceous walls that define the pore structure of MCM-48 is shown in Fig. 28. 

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