Post-crystallization

The separation of solids from liquids forms an important part of almost all front-end and back-end operations in hydrometallurgy. This is due to several reasons, including removal of the gangue or unleached fraction from the leached liquor the need for clarified liquors for ion exchange, solvent extraction, precipitation or other appropriate processing and the post-precipitation or post-crystallization recovery of valuable solids. Solid-liquid separation is influenced by many factors such as the concentration of the suspended solids the particle size distribution the composition the strength and clarity of the leach liquor and the methods of precipitation used. Some important points of the common methods of solid-liquid separation have been dealt with in Chapter 2. 

Post-crystallization/heating Low-melting-peak shift Final drying De-dusting Setting-reactor PET Temperature... 

The first step in any chemical approach to crystalline structure is to determine the short-range order, i.e. which atoms are bonded. The most convenient way of doing this is by means of the bond graph described in Section 2.5. In many cases all or most of the bond graph can be determined from first principles, since, except for the weakest bonds created in the post-crystallization stage, the bond graph is determined by the rules of chemistry, particularly the hierarchical principle (Rule 11.5), the valence matching principle (Rule 4.2), and the principle of maximum symmetry (Rule 3.1). 

However, the drawback of the use of HDPE has been the curling of the material caused by it. The reason for this is the post-crystallization taking place in the HDPE layer after its extrusion. This problem can be circumvented by replacing the HDPE by COC. COCs exhibit good water vapor barrier properties, and in addition, they are amorphous. Thus, neither post-crystallization nor curling caused by this occur in the extruded COC layer (64). 

In situations where crystallization does not produce the desired form or there are issues with robust final form production, crystallization engineers frequently perform solvent-mediated or slurry transformations to the desired product. Several articles have described the use of in situ spectroscopic probes to evaluate, track and control such transformations post-crystallization. Both Raman49-51 and NIR52 53 have been demonstrated for such... 

Relatively low productivity can be expected when fines are produced by salting-out process although it also depends on the substance properties. The post-crystallization processing (separation, concentration etc.) of very weak slurries may go according to the routines of colloid chemistry practice. 

The post-crystallization regime for Fe,Mg-rich chondrules is essentially quantitatively unconstrained. However, the presence of glassy mesostasis and fractionated element abundances within chondrule phases indicates that most chondrules definitively did not experience prolonged heating after they were cooled and quenched. 

Yamaguchi A., Taylor G. J., Keil K., Floss C., Crozaz G., Nyquist L. E., Bogard D. D., Garrison D., Reese Y., Wiesman H., and Shih C.-Y. (2001) Post-crystallization reheating and partial melting of eucrite EET 90020 by... 

Papike J. J., Fowler G. W., Shearer C. K., and Eayne G. D. (1996) Ion microprobe investigation of plagioclase and orthopyroxene from lunar Mg suite norites implications for calculating parental melt REE concentrations and for assessing post-crystallization REE redistribution. Geochim. Cosmochim. Acta 60, 3967-3978. 

Moreover, if polyoxymethylene is recrystallized from nitrobenzene and the usual chain-folded lamellae of ca. 100 A thickness is treated with TXN in the presence of BF3, more perfect extended-chain-type crystals are formed. These facts confirm the conclusion formulated -by Wunderlich, that post-crystallization leads to chain-folded crystals because of kinetic restrictions, while crystallization in the polymerizing system gives thermodynamically more stable extended-chain crystals77). The formation of the thermodynamic product in polymerization is due to the growth of crystals at equilibrium polymerization conditions. Thermodynamically less stable crystals may redissolve as a result of depropagation, and crystals may thus grow further under equilibrium conditions. This (at least partly) eliminates kinetic restric-... 

Post-crystallization exchange can take many forms that will complicate thermometry. Figure 3 shows four cartoons of the isotope distribution predicted for various processes of hydrothermal alteration of quartz by a low fluid. If diffusion is radial and inward from the grain boundary then a concentric zonation of is predicted with a smooth error function shaped gradient (Fig. 3 A and Fig. 4). If the rim of the crystal... 

Easy possibilities for post crystallization treatments of the crystal layer on the cooled surface. Treatments such as sweating and washing should lead to a further purification of the product (see Sections 7.8. and 7.9.). The amount of impure liquid entrapped in the layer or sticking on the surface of the crystal coat should be reduced by these treatments. 

The electron microprobe s detection limit for Pb can be a limitation in the precision of the chemical age results (e g., Olsen and Livi 1998) as can potentially the assumption that monazite is generally concordant (eg., Cocherie et al. 1998) and does not incorporate appreciable amounts of Pb° during growth (e g., Scherrer et al. 2000). Finger and Helmy (1998) suggest that monazite is resistant to post-crystallization disturbance and mostly free from inheritance. These assumptions are not always met as numerous studies indicate that the mineral can accumulate excess ° T b (Scharer 1984, Parrish 1990, Scharer et al. 1990, see also Fig. 2), Pb° (e g., Coleman 1998, Catlos et al. 

For tub products, a much softer filling consistency is required than for wrapping. Therefore, tub products are processed on lines with a (post)crystallizer instead of a B-unit. The filling consistency can be adjusted by varying the rotational speed of the crystallizer. Precrystallization can be applied in the tub-filling lines as well. 

In a typical flux synthesis, a significant excess of one or more constituents is added to the reaction charge, which is loaded in an appropriate (inert) crucible and sealed under inert atmosphere either in a fused silica ampoule or welded container, depending on the composition. A plug of quartz wool is often placed above the reaction charge, either inside the crucible or directly above it, to act as a filter to separate the flux, post-crystal growth [113]. After an adequate soak at elevated... 

Stress relieve by annealing at 150°C, accelerates post crystallization... 

The degree of crystallization increases with increasing cavity temperature prevention or reduction of post-crystallization (shrinkage), causes changes in toughness properties. High cavity temperatures provide a more uniform structure in the surface layers. 

Left effects of physical aging processes on oriented and semi-crystalline plastics (top relaxation processes, bottom post-crystallization)... 

The final properties of every polymeric material are determined by its chemical composition and its physical structure. Whereas chemical composition mainly affects its chemical aging processes, physical structure affects both chemical and physical aging processes. Other factors, such as catalytically active contamination, can affect all aging processes. Chemical and physical aging processes also influence each other, e.g., post-crystallization can reduce oxygen diffusion and thus affect oxidation and vice versa [19]. 

Temperature thus influences physical aging processes by increasing both the mobility of the molecular chains and the free volume. Both factors promote relaxation or post-crystallization. 

Figure 1.17 Chain cleavage and post-crystallization along the amorphous surface layer of lamellae [19]...

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