Bending contours

Rodriguez-Gonzalez, B., Pastoriza-Santos, 1. and Liz-Marzdn, L. M. (2006). Bending contours in silver nanoprisms, y. Phys. Chem. B 110 11796-11799. 

Iq and /g are plotted as a function of 5tg in Figure 4.10. This situation is achieved experimentally in a bent crystal, and the variation of s across the bend gives rise to a fringe pattern known as a bend contour. If we... 

In view of the failure of the dynamical theory without absorption to account for several important features of bend contours and thickness... 

Figure 4.13. Calculated curves showing I(,(a) and I a) as a function of st. These curves correspond to the intensity profiles across a bend contour observ in BF and DF, respectively. Note the asymmetrical nature of I ia) and the symmetrical nature of 7g(a) about s = 0. The crystal thickness was taken as 3/. tyt —0.1 and /o = tg. (From Amelinckx 1964.) Compare with Figure 3.18.

This is because in 7g(a), s always appears as s, but in 7o(u), s appears as s in the product term 2(5/a )(cosh Msinhw). Thus, we expect the contrast at a bend contour to be symmetrical about 5 = 0 in a DF image and asymmetrical in a BF image. Calculated profiles across a bend contour in a crystal of thickness 3tg and with /g/tg = 0.1 are shown in Figure 4.13. 

If we compare the curves of Figure 4.13 with the images of a bend contour shown in Figure 3.18, we can see that the dynamical theory with absorption predicts in considerable detail the contrast actually observed in... 

Finally, we examine the physical reasons for the symmetry about = 0 for bend contours in DF and for the asymmetry about 5 = 0 in BF, as illustrated in Figure 4.13. Consider the four waves of amplitudes /4q , Aq, A... 

Figure 5.4. Schematic diagram showing the displacement across the bend contour of the image of a dislocation from the position of the dislocation itself.

For n = 1, the image is displaced from x = 0 (the position of the dislocation) for all conditions except DF at s = 0. Thus, the image changes from one side to the other of the dislocation on crossing a bend contour (see also Figure 5.4). 

Figure 8.29. A single antiphase boundary cro ng a bend contour in body-centered bytownite (An77). DF image on a -refiection. Note reversal of contrast with s = 0 and (From McLaren and Marshall 1974.)...

Figure 3.46 Formation of a pair of bending contours. (Reproduced with permission from M. von Heimandahl, Electron Microscopy of Materials, Academic Press, New York. 1980 Elsevier B. V.)...

You have been told that thickness fringe and bending contours can be distinguished. Explain how. 

Fig. 12.23. Low-magnification micrographs of (a) the twist and (b) the BPF fabricated boundaries. At this magnifieation both boundaries appear straight. Surface pitting is observed in the a-axis side of both boundaries twins and bend contours are observed in the c-axis side (continued overleaf).

Fig. 40. (b) High magnification image of the [lOT] zone axis pattern related to the diffraction in (a). The lack of symmetry about an axis normal to the image is due to the influence of the image of the nodes of the upper Laue zones. Arrows indicate the position of the bend contours due to these nodes. 

The second group of kinematic definition of the bending contour can also be subdivided into procedures with rotary and linear tool motion. The roll-bending procedures (three-, four-, and multiple-roll bending), incremental tube forming, sweeping, and other process combinations and... 

Bending (Tubes, Profiles), Fig. 3 (left) Profile bending procedures with kinematic definition of the bending contour, right). Thermal-induced bending procedures... 

Increase of flexibility in the design for a freely definable bending contour... 

If the sample is crystalline, the scattered intensity depends very strongly on the orientation of the crystals and on their thickness. In bright field, a thin crystal will appear dark when it is correctly oriented for diffraction. If the crystal is not perfectly flat, the contours of correct orientation will appear as dark lines, called bend contours. Variation of intensity such as this in crystalline specimens is called crystallographic or diffraction contrast. Many types of defects in crystals cause localized distortion of the crystal lattice. These defects change the crystal orientation locally and so cause variations in the crystallographic contrast. Detailed information... 

Loss of crystallinity causes all diffraction contrast features in the TEM image to fade away. Moire fringes, lattice fringes, bend contours and the like will all lose contrast during irradiation [118]. Features that depend on orientation such as bend contours or dislocation strain field images will become smeared out, as directions in imperfect or very small crystals are less well defined (the reciprocal lattice spot increases in size). During irradiation, new contrast features -radiation artifacts - can appear temporarily and then fade with the rest. 

A wide variety of standard and special attachments are available for these chains. Most of the standard attachments are shown in Figure 10-1 to Figure 10-8. Attachments can also be modified for special needs. The hole size and location can be altered or the attachments can be altered to provide special geometry of bend, contour, or other forms. Figure 10-9 shows a group of special attachments. When modified attachments are needed, consult a roller chain manufacturer. Many attachment sizes and types are available in stainless steel. 

For comparison of serpentine curvilinear and serpentine square bends, contour plots of static pressure and dynamic pressure distributions are shown in Figure 10.23 for a single serpentine channel. 

Bending contours are due to bending of thin TEM sample. Note some defects (mainly stacking faults) present in the Ga-wing (vertical lines). 

Rodriguez-Gonzalez, B Pastoriza-Santos, I. and liz-Marzan, LM. (2006) Bending contours in silver nanoprisms. The Journal of Physical Chemistry B, 110, 11796-9. 

The eylindrieal structure of the CNT is also affected by the high-pressure eompaetion. Figure 14.19 is an example of a partially collapsed CNT. A eontrast eorresponding to the bend contour of the eompressed part is observed. As shown in Fig. 14.20, the innermost layer shows the 7r-bonding interaetion due to the interaetion between p electrons. The interlayer spaeing of the bonded layer is... 

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