Crystals intersection

The liquidus of the Yb4Bi3-Bi2Te3 system is quasi-binary and of the eutectic type, it consists of the branches of the primary crystallization of the Bi2Te3- and YbBi2-base solid solutions (Aliyev and Maksudova 1986). The branches of the primary crystallization intersect at 40 mol. % YbBi2 and 550°C where their cocrystallization starts according to the following eutectic scheme,... 

The density of dislocations is usually stated in terms of the number of dislocation lines intersecting unit area in the crystal it ranges from 10 cm for good crystals to 10 cm" in cold-worked metals. Thus, dislocations are separated by 10 -10 A, or every crystal grain larger than about 100 A will have dislocations on its surface one surface atom in a thousand is apt to be near a dislocation. By elastic theory, the increased potential energy of the lattice near... 

Several studies have concerned the microstnicture of lamellae in materials such as the block copolymers polystyrene-h/oc/r-poly-l-vinylpyridine [139] and polystyrene-h/oc/r-polybutadiene [140], as well as single crystals of poly-para-xylylene [139], and reveal features (such as intersecting lamellae (figure Bl.19.29)) that had not been previously observed. 

Figure B3.3.13. Intersecting stacking faults in a fee crystal at the impact plane induced by collision with a momentum mirror for a square cross section of side 100 unit cells. The shock wave has advanced half way to the rear ( 250 planes). Atom shading indicates potential energy. Thanks are due to B Holian for tliis figure.

Crystallizers with Fines Removal In Example 3, the product was from a forced-circulation crystallizer of the MSMPR type. In many cases, the product produced by such machines is too small for commercial use therefore, a separation baffle is added within the crystallizer to permit the removal of unwanted fine crystalline material from the magma, thereby controlling the population density in the machine so as to produce a coarser ciystal product. When this is done, the product sample plots on a graph of In n versus L as shown in hne P, Fig. 18-62. The line of steepest ope, line F, represents the particle-size distribution of the fine material, and samples which show this distribution can be taken from the liquid leaving the fines-separation baffle. The product crystals have a slope of lower value, and typically there should be little or no material present smaller than Lj, the size which the baffle is designed to separate. The effective nucleation rate for the product material is the intersection of the extension of line P to zero size. 

When crystals yield, dislocations move through them. Most crystals have several slip planes the f.c.c. structure, which slips on 111) planes (Chapter 5), has four, for example. Dislocations on these intersecting planes interact, and obstruct each other, and accumulate in the material. 

By their nature, dislocations cannot end suddenly in the interior of a crystal a dislocation line can only end at a free surface or a grain boundary (or form a closed loop). Where a screw dislocation intersects a free surface there is inevitably a step or ledge in the surface, one atomic layer high, as shown in Fig. 20.30c. Furthermore, the step need not necessarily be straight and will, in fact, almost certainly contain kinks. 

In the as-synthesized MFI-crystals the tetrapropylammonium (TPA) ions are occupying the intersections between the straight (parallel) and the sinusoidal channels of the zeolite, thus providing an efficient pore filling. The detailed structure of as-synthesized MFI-TPA has been elucidated by X-ray single crystal analysis (ref. 3). Also the combination tetrabutyl-Ztetraethylammonium can be applied as template in MFI-synthesis. A 1 1 build-in is found then (Fig. 1). When only tetrabutylammonium is available as template, the MEL (ZSM-11) lattice is formed with another distance between the channel intersections. 

Direction indices are also frequently used in crystallography to specify the direction or the orientation of a line in the crystal. If a point is moved from the origin (the intersection of the coordinate axes) to some other position in the crystal by means of translations paral-... 

The electrocrystallization on an identical metal substrate is the slowest process of this type. Faster processes which are also much more frequent, are connected with ubiquitous defects in the crystal lattice, in particular with the screw dislocations (Fig. 5.25). As a result of the helical structure of the defect, a monoatomic step originates from the point where the new dislocation line intersects the surface of the crystal face. It can be seen in Fig. 5.48 that the wedge-shaped step gradually fills up during electrocrystallization after completion it slowly moves across the crystal face and winds up into a spiral. The resultant progressive spiral cannot disappear from the crystal surface and thus provides a sufficient number of growth... 

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