Diameter of crystal

A similar table summarizing the experimental data measured in the FBC. with the same mean diameters of crystal seeds, r/ l0, and under the same operating temperatures, T, was also obtained but it is not given here. 

Figure 7.14. Schematic of fat crystal network under extension when the weak-link theory is applicable ( is the diameter of crystal clusters, La is the size of the microscopic system, AL is the extension due to elongational stress, a is the size of a primary particle within a cluster and da is the interfloc distance).

Dried crystals were observed by optical and scanning electron microscopy (SEM) in order to measure their Ferret mean diameter and to determine their habit and texture. The mean diameters of crystals obtained from different solvents and submitted to different drying conditions are reported in Table 15.2.3.3. 

In addition, the stability of the diameter of crystal growing in length can be enhanced by selecting the minimum possible value of the difference D pi > d sPs-... 

The fluoride ion is the least polarizable anion. It is small, having a diameter of 0.136 nm, 0.045 nm smaller than the chloride ion. The isoelectronic E and ions are the only anions of comparable size to many cations. These anions are about the same size as K" and Ba " and smaller than Rb" and Cs". The small size of E allows for high coordination numbers and leads to different crystal forms and solubiUties, and higher bond energies than are evidenced by the other haUdes. Bonds between fluorine and other elements are strong whereas the fluorine—fluorine bond is much weaker, 158.8 kj/mol (37.95 kcal/mol), than the chlorine—chlorine bond which is 242.58 kJ/mol (57.98 kcal/mol). This bond weakness relative to the second-row elements is also seen ia 0-0 and N—N single bonds and results from electronic repulsion. 

The polycrystaUine EGS is converted to siagle-crystal silicon via the C2okralski (CZ) crystal growing process, based on the solidification of silicon atoms from the Hquid phase at a moving iaterface. Volume production of 200-mm diameter crystals is standard. Development of crystals having diameters of up to 400 mm has been predicted (3). 

Microfilaments and Microtubules. There are two important classes of fibers found in the cytoplasm of many plant and animal ceUs that are characterized by nematic-like organization. These are the microfilaments and microtubules which play a central role in the determination of ceU shape, either as the dynamic element in the contractile mechanism or as the basic cytoskeleton. Microfilaments are proteinaceous bundles having diameters of 6—10 nm that are chemically similar to actin and myosin muscle ceUs. Microtubules also are formed from globular elements, but consist of hoUow tubes that are about 30 nm in diameter, uniform, and highly rigid. Both of these assemblages are found beneath the ceU membrane in a linear organization that is similar to the nematic Hquid crystal stmcture. 

Sihcon carbide whiskers typically have diameters of a few micrometers and lengths up to 5 cm. They may be composed of either P SiC or a-SiC, the latter in one or more polytypes, and occur mosdy as hair- or ribbonlike crystals. Despite many attempts to produce SiC whiskers on a large scale at low cost, they have never acquired a wide importance. SiC whiskers have been reviewed (111—120). 

Coefficient of Variation One of the problems confronting any user or designer of crystallization equipment is the expected particle-size distribution of the solids leaving the system and how this distribution may be adequately described. Most crystalline-product distributions plotted on arithmetic-probability paper will exhibit a straight line for a considerable portion of the plotted distribution. In this type of plot the particle diameter should be plotted as the ordinate and the cumulative percent on the log-probability scale as the abscissa. 

Fig. 3. Crystal structure of the compound C o(S8)2CS2 projected normal to the a-axis. Large cireles denote Coo, small eireles denote sulfur, black balls denote carbon. In this structure, the Coo-Ceo distanee is nearly 11 A, and the diameter of the Ceo molecule has been reduced relative to the other atoms for clarity [54].

Configurations of interest are those using disk-shaped samples cut from crystals in orientations that permit plane waves of uniaxial strain to propagate through their thickness when a uniform load is applied to their face. When the diameter of the disk is sufficiently large in comparison to its thick-... 

In this section we briefly summarize a few modern applications of simulation techniques for the understanding of crystal growth of more complex materials. In principle, liquid crystals and colloids also belong to this class, but since the relative length of their basic elements in units of their diameter is still of order about unity in contrast to polymers, for example, they can be described rather well by the more conventional models and methods as discussed above. 

H. Weimann, J. Amon, T. Jung, G. Mueller. Numerical simulation of the growth of 2" diameter GaAs crystals by the vertical gradient freeze technique. J Crys Growth 180 560, 1997. 

A solution of the piperidino-diol (9 grams) in acetic anhydride (18 ml) was heated at 90°C for 1 hour, the solution cooled, excess acetic anhydride destroyed by the careful addition of water, and the resulting solution carefully made alkaline with 2N caustic soda solution to precipitate a solid product. The soiid was dried, extracted with n-hexane and the solution filtered free of insoluble material before percolation down a column (4x1" diameter) of alumina. Eiution with n-hexane gave a fraction (4.2 grams) which was crystallized twice from ether to give the diacetate, MP 176°-180°C. 

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