Weak-beam dark-field

Single-Particle Diffraction, Weak-Beam Dark-Field, and Topographic Images of Small Metallic Particles in Supported Catalysts... 

Figure 8. Platelet structures observed by weak beam dark field.

This equation is particularly useful when setting up for weak-beam dark field imaging, to be discussed in Chapter S. 

Figure 5.19. Ewald sphere diagrams and corresponding diffraction patterns illustrating the procedures for setting up the conditions for weak beam dark field imaging using the first-order diffracted beam g. Continued, p. 160)...

Fig. 15.3 Preparation of epitaxial thin film model catalysts, (a) Electron micrograph of a Pt-AljOj model catalyst with a mean particle size of 5 nm the insets show the corresponding electron diffraction pattern and the (200) weak-beam dark-field image of a pyramidal Pt nanocrystal (b) an atomically resolved TEM micrograph of a slightly rectangular Pt particle. A structural model of a pyramidal Pt particle is presented in (c). To illustrate the epitaxial growth the NaCl substrate is also included...

Figure 5 Bright field (a) and weak beam dark field (b) TEM pictures (345x212nm ) of large Pd particles supported on MgO (100).

Fig. 3.69 Representative weak-beam dark-field (WBDF) images where dislocations Burgers vectors (b) and fault vector (Rp) of fault F were determined (transmission electron microscopy) [55], With kind permission of John Wiley and Sons...

Figure 7.6 Weak beam dark-field graph showing the microstmcture in 304 stainless steels irradiated at 3.4 dpa. The triangle-shape clusters are stacking fault tetrahedra [24].

Figure 9.1 Weak beam dark-field TEM image = 200 close to a zone axis <011>)ofF82H...

Figure 9.2 Dislocation microstmcture of EMIO irradiated to 112 dpa at 398°C. Weak beam dark-field micrograph, g = 110. ...

Fig. 10. Deformation microstructures containing perfect dislocations (the confining pressure is 5 GPa). (a) Deformation temperature T = 293 °C (101) foil plane, weak-beam dark field (4.1g, g = 202). The dislocations nucleated at crack edges are of 1/2[1 0 i](l 11) type. These half-loops are elongated along the [3 21] direction (after Rabier and Demenet [62]). (b) In the bulk, the same dislocations tend to be aligned along several Peierls valleys < 112 > /30°, < 12 3 > /4T, and screw orientation (after Rabier et al. [62]). (c) Deformation temperature T = 150 °C. Same Peierls valleys as at room temperature some strong pinning points are indicated by arrows (after Rabier et al. [61]).

Fig. 11. Silicon deformed in the metallic phase (confining pressure 15 GPa, T = 293 °C). Deformation microstrutures in the diamond-cubic Si I phase, (a) Ghde bands with a high dislocation density and isolated perfect dislocations. Weak-beam dark field 2g, g = 040. (b) Isolated perfect dislocations with <123>/41° orientation (straight lines) and unstable 1/2[110] screw segments. After Rabier et al. [62].

Deformation substructure in Si indented at low temperature Asaoka et al. [66] recently revisited the indentation of silicon with the aim of deforming it plastically below room temperature. These authors indented silicon at 77 K and showed that it can be deformed plastically. TEM observations of the microstructure showed dislocations aligned along the <110> and <112> directions. Weak-beam dark field showed these dislocations were perfect ones and had a/2<110> Burgers vectors. A HREM observation was also performed on a dislocation seen edge-on, which was shown to have an undissociated core. The exact location of this core, in a glide plane or a shuffle plane, could not be determined. 

Fig. 14. Dissociated dislocations in the (111) glide plane of a crystal prestrained at 1050 °C and further deformed at 293 °C under 5 GPa. There are two slip systems, A and B. (a) Weak-beam dark field (2.2g, g = 2 2 0) A and B are in contrast, (b) Weak-beam dark field (7.1g, g = 1 1 1) the stacking fault of A is in contrast, B is in contrast, (c) Weak-beam dark field (3.1g, g = 2 0 2) A is out of contrast, B is in contrast. After Rabier and Demenet [77].

Fig. 14. (a) Weak beam dark-field image of dislocations in biotite. The trace of the slip plane (S) is indicated as well as dislocations bowing out (X). [346]. (b) Dark-field image of screw dislocations in... 

WBDP weak beam dark field method... 

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