Crystals mixed crystals

Stimulated emission has been recorded for Nd + in more than 100 different crystals including doped single crystals, mixed crystals (solid solutions), and several crystals in which Nd is a stoichiometric component of the host (21). Because the spectroscopic properties are host dependent, the selection of materials provides variability with respect to cross sections and lifetimes as well as other physical properties. 

The concept of the multi-component molecular solid covers co-crystals, mixed crystals, salts, clathrates, and complexes. As Yan and Evans have indicated,multi-component systems of luminescent dyes with a variety of co-assembled units offer a more flexible method for tuning the packing-directed luminescent properties of the dye than the formation of polymorphs of the pure material. An example has already been given above (16). ° Another example is the organic salts of anthracene-2,6-disulfonic acid (20) with amines (Scheme 6). ... 

It is usual, except in special cases, to work with x-rays of 0.5 to about 3.0 A wave lengths or with cathode rays of 10 to 10 volts. The latter coincide, according to the de Broglie relation, with a wave length range of about 0.4 to 0.04 A. The molecules under investigation may be in the free state (gas or solution) or in the form of a homogenous condensed phase (liquid, crystal, mixed crystal). 

In this review article vibronic spectra are presented for selected d , d , and d systems in a variety of environments such as pure crystals, mixed crystals and surfaces. In the d example, vanadium oxide on a Si02 substrate, the relation between the vibronic structure and the V=0 bond length in the lowest excited electronic state and the reactivity toward CO is discussed. In the d example, ReBr and MnF ions in single and mixed crystals, group theory selection rules are shown to be important for understanding the vibronic mechanism by which d— d transitions occur in an octahedral environment. In the final example, d ° Au(CN)2 and Ag(CN)j ions in different pure crystals, the appearance of vibronic structure is related to the relative rates for radiative and non-radiative processes. 

Crystal Photolysis One-Component Crystals Mixed Crystals Inclusion 73-2... 

Essentially all the ammonium sulfate fertilizer used in the United States is by-product material. By-product from the acid scmbbing of coke oven gas is one source. A larger source is as by-product ammonium sulfate solution from the production of caprolactam (qv) and acrylonitrile, (qv) which are synthetic fiber intermediates. A third but lesser source is from the ammoniation of spent sulfuric acid from other processes. In the recovery of by-product crystals from each of these sources, the crystallization usually is carried out in steam-heated sa turator—crystallizers. Characteristically, crystallizer product is of a particle size about 90% finer than 16 mesh (ca 1 mm dia), which is too small for satisfactory dry blending with granular fertilizer materials. Crystals of this size are suitable, however, as a feed material to mixed fertilizer granulation plants, and this is the main fertilizer outlet for by-product ammonium sulfate. 

Fig. 11. Schematic diagram of a simple, perfectiy mixed crystallizer.

Determination of Crystallization Kinetics. Under steady-state conditions, the total number production rate of crystals in a perfectly mixed crystallizer is identical to the nucleation rate, B. Accordingly,... 

GSD Characteristics for MSMPR Crystallizers. The perfectiy mixed crystallizer described ia the preceding discussion is highly constrained and the form of crystal size distributions produced by such systems is fixed. Such distributions have the foUowiag characteristics. 

Preferential Removal of Crystals. Crystal size distributions produced ia a perfectiy mixed continuous crystallizer are highly constraiaed the form of the CSD ia such systems is determined entirely by the residence time distribution of a perfectly mixed crystallizer. Greater flexibiUty can be obtained through iatroduction of selective removal devices that alter the residence time distribution of materials flowing from the crystallizer. The... 

Classified removal of course material also can be used, as shown in Figure 16. In a crystallizer equipped with idealized classified-product removal, crystals above some size ate removed at a rate Z times the removal rate expected for a perfecdy mixed crystallizer, and crystals smaller than are not removed at all. Larger crystals can be removed selectively through the use of an elutriation leg, hydrocyclones, or screens. Using the analysis of classified-fines removal systems as a guide, it can be shown that the crystal population density within the crystallizer magma is given by the equations... 

Sodium chloride and sodium cyanide are isomorphous and form an unintermpted series of mixed crystals. The ferrocyanide ion has a marked effect on the habit of sodium cyanide crystallized from aqueous solution (50). Sodium cyanide and sodium carbonate form a molten eutectic at approximately 53 wt % sodium carbonate and 465°C. The specific conductivity of molten 98% sodium cyanide is 1.17 S /cm (51). 

Phospholipids. For the removal of ionic contaminants from raw zwitterionic phospholipids, most lipids were purified twice by mixed-bed ionic exchange (Amberlite AB-2) of methanolic solutions. (About Ig of lipid in lOmL of MeOH). With both runs the first ImL of the eluate was discarded. The main fraction of the solution was evaporated at 40°C under dry N2 and recryst three times from n-pentane. The resulting white powder was dried for about 4h at 50° under reduced pressure and stored at 3°. Some samples were purified by mixed-bed ion exchange of aqueous suspensions of the crystal/liquid crystal phase. [Kaatze et al. J Phys Chem 89 2565 7955.]... 

A semi-open impeller has exposed blades, but with a support plate or shroud on one side. Some people prefer the name semi-enelosed. These types of impeller are generally used for liquids with a small percentage of solid particles like sediment from the bottom of a tank or river, or crystals mixed with the liquid (Figure 6-17). 

This clearly indicates quantum diffusion of H and D atoms, rather than molecular diffusion. In mixed crystals of D2 and HD (with the H2/D2 ratio being from 20 1 to 7 1) the concentration of... 

Rielly and Marquis (2001) present a review of crystallizer fluid mechanics and draw attention to the inconsistency between the dependence of crystallization kinetic rates on local mean and turbulent velocity fields and the averaging assumptions of conventional well-mixed crystallizer models. 

This equation describes the change of population in a well-mixed system and is often used to model fully mixed crystallization and precipitation processes. If the system is imperfectly mixed, however, then the more complicated equation 2.88 can be used provided that the external flow field can be calculated e.g. by use of CFD (see later). 

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