Electron lattice-fringe

An image of an MWCNT obtained by using all available reflexions usually exhibits only prominently the oo.l lattice fringes (Fig. 4) with a 0.34 nm spacing, representing the "walls" where they are parallel to the electron beam. The two walls almost invariably exhibit the same number of fringes which is consistent with the coaxial cylinder model. 

The macrostructure of the boron nitride obtained here is porous with pores 2 pm in diameter. There is no evidence for microporosity and the BET surface area 1s 35 m2 g-1. Transmission electron micrographs (Figure 4) show regions of well developed crystallinity. The crystalling grains are 5—10 nm on a side and 30-40 nm long. The BN (002) lattice fringes are clearly visible. 

High Resolution Transmission Electron Microscopy (HRTEM, Philips CM20, 200 kV) was applied to get structural and nanotextural information on the fibers, by imaging the profile of the aromatic carbon layers in the 002-lattice fringe mode. A carbon fiber coated with pyrolytic carbon was incorporated in epoxy resin and a transverse section obtained by ultramicrotomy was deposited on a holey carbon film. An in-house made image analysis procedure was used to get quantitative data on the composite. 

Coma is due to the electron beam being tilted away from the optical axis of the objective lens, the coma-free axis. The coma results in lattice fringes related to +g and -g being shifted by the objective lens. Lattice fringes belonging to different beam pairs, +g and -g, are shifted differently resulting in an asymmetry of the HRTEM image. 

Fig. 4.5 High resolution electron micrograph of synthetic goethite crystals cut perpendicular to the needle axis [010]. The crystals are bounded by 101 faces. The large crystal contains faults and some of the smaller, fault-free crystals show ca. 1 nm lattice fringes corresponding to the c -parameter of the unit cell (0.9956 nm) (Schwertmann, 1984, with permission, courtesy H. Vali, Schwertmann Cornell, 2000, with permission).

Fig. 4.6 High resolution electron micrograph of natural goethite a) Diamond-shaped cross sections of domains running along [010] and bounded by 101 faces. Lattice fringes correspond to the c -parameter. b) Higher magnification shows the a fringes (ca. 1 nm) and structural distortions. (Smith Eggleton, 1983 with permission courtesy R.A. Eggleton).

Fig. 4.8 High resolution electron micrograph of two goethite domains and their interdomai-nic zone. The lattice fringes at 0.5 nm correspond to the (200) spacing (courtesy S. Mann, Bristol).

Fig. 16.9 Electron micrographs of soil lepidocro-cite. a) Large multidomainic lath-like crystal viewed perpendicularto [001] with laminar pores from a re-doximorphic soil, Natal, South Africa, b) Poorly crystalline grassy lepidocrocite crystals mixed with tiny ferrihydrite particles and pseudo-hexagonal kaolinite platelets. Origin as before (a. b courtesy P. Self), c) Small lepidocrocite crystal from a hydromorphic soil (with ferrihydrite) viewed perpendicularto [001] and showing (020) lattice fringes (see also Schwert-mann. Taylor, 1989,with permission).

Fig. 4.4.3 High-resolution electron micrograph and electron diffraction pattern. (A) Sample II the mean diameter and lattice fringe of particles X and Y were 7.7 nin, 0.374 nm. and 7.1 nm, 0.397 nm, respectively. (B) Sample V the 15.4-nm particle was viewed along the [0011 zone axes with the 100 lattice spacing of 0.397 nm. (From Ref. 10.)...

FIGURE 2.15 Transmission electron micrograph and lattice fringe images for VGCF. (Courtesy of Prof. M. Endo, Shinshu University, Nagano, Japan. With permission.)... 

Chems et al [18] performed a detailed quantitative analysis of CBED data for (1010) inversion domains in GaN grown on sapphire and concluded that of the various structural models tested, only the IDB model [14] was consistent with their data. High resolution electron microscopy images [16,20] also support the IDB model. Such images show a shift in intensity of lattice fringes across the (1010) plane that is consistent with the proposed model. 

Figure 7--Second phase particles (lattice fringes) in molecular sieve matrix, FeZSM-5, after 4h steam treatment at 700 °C, SiO0/Fe2O3-ratio 90. Molecular sieve structure is amorphous due to electron beam damage.

Using transmission electron microscopy the lattice fringe image can be seen. Also the scanning electron microscopy image showed that the montmoriilonite layer structures still remained after Si-heterostructure and no occluded clay by SiOj is observed. The results further indicate the expansion of the basal spacing. 

Cockayne, D. J. H., Parsons, J. R., Hoelke, C. W. (1971). A study of the relationship between lattice fringes and lattice planes in electron microscope images of crystals containing defects. Phil. Mag., 24, 139-53. 

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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