Atomic micrograph

Figure 15.2 (a) Atomic micrograph of silver film-over-nanospheres (AgFON). (b) Reflec-... 

Eutectoid structures are like eutectic structures, but much finer in scale. The original solid decomposes into two others, both with compositions which differ from the original, and in the form (usually) of fine, parallel plates. To allow this, atoms of B must diffuse away from the A-rich plates and A atoms must diffuse in the opposite direction, as shown in Fig. A1.40. Taking the eutectoid decomposition of iron as an example, carbon must diffuse to the carbon-rich FejC plates, and away from the (carbon-poor) a-plates, just ahead of the interface. The colony of plates then grows to the right, consuming the austenite (y). The eutectoid structure in iron has a special name it is called pearlite (because it has a pearly look). The micrograph (Fig. A1.41) shows pearlite. 

In some materials, semiconductors in particular, interstitial atoms play a crucial role in diffusion. Thus, Frank and Turnbull (1956) proposed that copper atoms dissolved in germanium are present both substitutionally (together with vacancies) and interstitially, and that the vacancies and interstitial copper atoms diffuse independently. Such diffusion can be very rapid, and this was exploited in preparing the famous micrograph of Figure 3.14 in the preceding chapter. Similarly, it is now recognised that transition metal atoms dissolved in silicon diffuse by a very fast, predominantly interstitial, mechanism (Weber 1988). 

Since a considerable amount of review articles on both theoretical frameworks and calculated results have been reported[15-25], the main objective of the present study is placed on the comparisons with experimental results. The organization of the present report is as follows In the next section, for the sake of completeness, a brief theoretical description of the PPM is summarized from the previous articles. In the third section, disorder-LIq transition is focused and visualized atomic (spin) configuration is compared with recent high resolution electron micrograph. In the fourth section, ordering relaxation... 

FIG. 1 Freeze-etching image of a bacterial cell of (a) Desulfotomaculum nigrificans (bar, 100 nm). Atomic force micrographs of the S-layer proteins of (b) Bacillus sphaericus CCM 2177 and (c) Bacillus stearothermophilus PV72/p2 recrystallized in monolayers on silicon wafers. Bars, 50 nm. The insets in (b) and (c) show the corresponding computer-image reconstructions. 

Fig. 2. Effect of deposition time and deposition pressure on (a) dot size (inset shows atomic force micrograph of dots formed at O.STorr) (b) dot density.

In this present study, we basically showed dependence of the number of reduced cobalt metal surface atoms on dispersion of cobalt oxides along with the presence of rutile phase in titania. Both XRD and SEM/EDX results (not shown) revealed good distribution of cobalt oxides over the titania support. However, it can not differentiate all samples containing various ratios of rutile/anatase phase. Thus, in order to determine the dispersion of cobalt oxide species on titania, a more powerful technique such as TEM was applied with all samples. The TEM micrographs for all samples are shown in Figure 1. The dark spots represented cobalt oxides species present after calcination of samples dispersing on titania consisting various... 

Figure 1. High resolution Electron Micrograph of a cubic MgO crystal viewed in [100] direction showing square net of 22 fringes and apparent bending of atom planes at edges. Courtesy of Dr. T. Tanji.

Fig.2 High-resolution transmission electron micrograph of [Os5C(CO)i4] on MgO. This cluster was present with osmium carbonyl clusters with lower nuclearities (containing three and four Os atoms) [25]...

Fig. 11 Formation of crystalline 3D super-lattices of tin nanoparticles a TEM view of a facetted super-crystal b SEM image showing particles included into a super-crystal as well as the organic surrounding c High resolution micrograph showing the alignment of the tin atomic planes inside the super-structure...

TEM is conventionally used as a tool to evaluate the size and shape of the cores by direct imaging. However, the core size cannot be determined with atomic resolution from low contrast and 2-D projection of the 3-D core. There are several subjective factors in the estimation of size e.g., how to select the area from which the core size is derived and how to measure this precisely from the vague projections of cores in the TEM micrographs. 

Figure 1.9. FIM micrograph showing boron segregation to a grain boundary in austenitic 316L stainless steel, together with atom probe composition profiles for boron (Karlsson and Norden 1988).

Recent developments have allowed atomic force microscopic (AFM) studies to follow the course of spherulite development and the internal lamellar structures as the spherulite evolves [206-209]. The major steps in spherulite formation were followed by AFM for poly(bisphenol) A octane ether [210,211] and more recently, as seen in the example of Figure 12 for a propylene 1-hexene copolymer [212] with 20 mol% comonomer. Accommodation of significant content of 1-hexene in the lattice allows formation and propagation of sheaf-like lamellar structure in this copolymer. The onset of sheave formation is clearly discerned in the micrographs of Figure 12 after crystallization for 10 h. Branching and development of the sheave are shown at later times. The direct observation of sheave and spherulitic formation by AFM supports the major features that have been deduced from transmission electron and optical microscopy. The fibrous internal spherulite structure could be directly observed by AFM. 

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