Crystal growth direction

However, hydroxides proved to be applicable intermediate for preparing various nanocrystals of rare earth oxide, oxysulphide, oxyfluoride, and other rare earth compounds. In this route, the crystallized R(OH)s nanocrystals instead of gels were obtained and collected, later a next step is performed to convert the R(0H)3 nanocrystals into other compounds, without destroying the morphology. The obtained new nanocrystals may or may not have a certain crystal growth direction related to the precursor. A selection of typical works on the conversion of rare earth hydroxide nanostructures are listed in Table 1. 

Fig. 19. High-magnification image of an aligned goethite crystal and stained organic fibrous material running parallel to the crystal growth direction (arrow). Bar = 0.1 /nm.

Fig. 7.1. Classification of silicon ribbon technologies according to the shape of the meniscus at the liquid-solid interface [22]. For Ml, the lower part of the meniscus is formed, e.g. by a shaping die, whereas M2 has a broad base at the free surface of the liquid. Both Ml and M2 represent ribbon techniques, where the crystallisation front moves in the direction of ribbon transport (type I). M3 is characterised by a large liquid-solid interface and represents the techniques with wafer transport almost perpendicular to the crystal growth direction (type II)...

Fig. 13. The nucleation point(s) and crystal growth direction in a gel-sphere of a a few ultra-large crystals of MFI and b one ultra-large crystal of analcime. Larger gel-spheres allow larger crystals to be grown...

Figure 40 Left Schematic illustration of a PE crystalline lamella in which the stems are inclined by a significant angle in the plane perpendicular to the fast crystal growth axis (i.e., the b-axis). In terms of the symmetry operation, such lamella exhibits an inversion point when viewed along b. Right The unbalanced stresses generated on the lamellar surface result in a helicoidal twist of the crystal, which becomes symmetric about the mirror plane M perpendicular to the crystal growth direction and passing through the primary nucleus. With permission from Rosenthal, M. etal. Angewandte Chemie lot. Ed. 123 (2011) 9043-9047. ...

One of the earliest and most commonly used microscopical methods of examining polymers is between crossed polarizers. Some of the earliest work was determining the birefringence of fibres, then came the study of spherulites in semi-crystalline polymers. Often the spherulites show a simple Maltese Cross pattern where the dark areas show zero-amplitude birefringence, which simply arises from the orientation of the crossed polars. In the polypropylene spherulites (Fig. 2.7a), radial growth has occurred along the a -axis which is the fastest crystal growth direction, while the and c-axis are effectively randomly oriented. 

In summary, if the direction of flow in the liquid which originated from the shrinkage of solidification were opposite to the crystal growth direction, it would... 

The crystal orientation of PCL homopolymers spatially confined in nanocylinders showed that the c-axis of PCL crystals (stem direction of PCL chains) was always perpendicular to the cylinder axis but the crystal growth direction depended significantly on nanocylinder diameter D and crystallization temperature T the h-axis (fastest growth axis of PCL crystals) was parallel to the cylinder axis in nanocylinders with smaller D (<13.0 nm), whereas the (110) plane of PCL... 

---