Lattice fringes

Figure 3. Lattice fringes LF 002 of buckled nanotube particles.

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. 

Fig. 4. Singularities in MWCNT imaged by means of basal plane lattice fringes, (a) Straight ideal MWCNT. (b) Capped MWCNT. The tube closes progressively by clusters of 2-5 graphene layers. (c)(d) Bamboo-like compartments in straight tubes.

A square and triangular Pt nanoparticle obtained by using poly-NIPA and poly-NEA, respectively, was observed by high resolution TEM (HRTEM) (JEM-2010F). The images (Figure 4) show a crystalline structure with clearly resolved lattice fringes. The square Pt nanoparticle... 

Similarly, monometallic Rh, Pd, and Au and bimetallic Pt-Rh and Pt-Pd nanowires were prepared in FSM-16 or HMM-1 by the photoreduction method [30,33,34]. The bimetallic wires gave lattice fringes in the HRTEM images, and the EDX analysis indicated the homogeneous composition of the two metals. These results show that the wires are alloys of Pt-Rh and Pt-Pd. Mesoporous silica films were also used as a template for the synthesis of uniform metal particles and wires in the channels [35,36]. Recently, highly ordered Pt nanodot arrays were synthesized in a mesoporous silica thin film with cubic symmetry by the photoreduction method [37]. The... 

Fig. 56. TEM images of DNA-linked gold network (a) an assembly of 8 and 30 nm gold particles (b) higher resolution image of (a) (c) control experiment without DNA (d) HR-TEM image of a portion of a hybrid Au/quantum dot (QD) assembly. The lattice fringes of the QDs, which resemble fingerprints, appear near each Au nanoparticle, (e) A satellite structure formed using a 60-fold excess of the 8 nm particles. Reproduced with permission from Ref. (185). Copyright 2000, American Chemical Society.

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. 

Shim H.S., Hurt R.H. and Yang N.Y.C. A methodology for analysis of 002 lattice fringe images and its application to combustion-derived carbons. Carbon 2000 38 29-45. 

Fig. 8.3 SEM images of hexadecyl-functionalized magnesium phyllosilicate showing (A) intact spheroids (scale bar = 20pm) and (B) fractured spheroid with foam like interior (scale bar = 20pm). (C) TEM image of a wall fragment showing lattice fringes corresponding to a periodic lamellar structure (scale bar = 50 nm).

A noteworthy line of research is the application of TEM on models for supported catalysts. Figure 7.6 shows a side view of Au particles (diameters <6 nm) on top of MgO crystals, taken from the work of Giorgio et al. [16]. The picture beautifully shows the shape of the particles together with the lattice fringes characteristic of certain orientations of the particles and the support. In addition, the authors obtained... 

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. 

One typical delocalization effect is that lattice fringes appear to continue well beyond the edge of a specimen into the vacuum or support film. In... 

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).

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