Crystals characteristic morphology

Similarly, we can pick another example in crystal growth in melt. In this case, the growth occurs at the interface between the melt and a substrate that is kept at a constant temperature that is lower than the critical temperature for crystallization. The morphology characteristic of the instability is formed by the coupling of the heat flux and the surface-form fluctuation. This problem was first theoretically analyzed by Mullins and Sekerka.57-62... 

Zeolite crystals can be grown in sizes ranging from 0.5 pm to several hundreds pm and often have a characteristic morphology. Thus type A zeolites are cubes,... 

Twinning and epitaxial growth are also methods of controlled growth, and therefore crystals grown by these methods often exhibit a very different characteristic morphology from that of coexisting single crystals. 

In contrast to the hexagonal prismatic morphology of low-temperature quartz, it has been assumed that the characteristic morphology of high-temperature quartz is hexagonal bipyramidal where no 1010 faces appear on the crystal... 

By the time the clinical program has entered phase 3, the sponsor should provide a full description of the physical, chemical, and biological characteristics of the drug substance. For example, most of the following should be evaluated and submitted solubility and partition coefficient, pKa, hygroscopicity, crystal properties/morphology, thermal evaluation, X-ray diffraction, particle size, melting point, and specific rotation stereochemical consideration. Proof... 

As noted in the previous section, the phenomenon of polymorphism is not new to chemistry. Nineteenth century chemists were very much aware of the properties of solids, and in the decades preceding the development of spectroscopic and X-ray crystallographic methods, the characterization of solids was a crucial aspect of the identification of materials. Chemists grew crystals carefully in order to obtain characteristic morphologies and then determined physical properties such as colour, interfacial angle, indices of refraction, melting point, and even taste (e.g. Schorlemmer 1874 Senechal 1990 Kahr and McBride 1992). Being critically observant was essential, for there was little other information to rely on. 

NS-W powders exhibit a characteristic morphology, exhibiting holes in the crystal surfaces (Fig. 5.30), which form during HF-washing of the powders due to the dissolution of partly intergrown silicate phases. 

The characteristic morphology of the spherulite branched crystal pattern was found to closely resemble polymeric sphenilites. Scheme 3.2 shows a schematic growth mechanism. 

PVDP Is a crystalline polymer that has offered interesting and fruitful subjects for analysis to many scientists in the entire domain on engineering plastics since about 1975, Both crystallization and morphology of the polymer are Important features for the polymer properties and the richness of the morphological behavior is not surpassed by any other polymer (3). It has the characteristic stability of fluoropolymers when exposed to harsh thermal, chemical, and ultraviolet environments. The alternating CH and CF groups in the chain contributes to the unique polarity that influences its solubility and electric properties. 

Figure 14.3 Evolution of the storage modulus during crystallization of an iPP grade at Texp = 135°C, measured under quiescent conditions (0,1) and after shearing at 7=60(l/s) for fj = 1 s ( , 2), and = 6 s (A, 3). Optical micrographs indicate the characteristic morphology for these three crystallization experiments [176],...

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