Effect of temperature on crystallization

In the majority of investigations on zeolite synthesis, particular attention was paid to the effect of temperatures on crystallization. Recent works on mordenite crystallization (20, 32) indicate that temperature... 

Parameter Estimation. The kinetic parameters of the model given above that must be estimated for model identification include kg, g, Eg, kb, b, Eb,j. Parameter estimation for this type of model is quite difficult because the parameters appear nonlinearly, the nucleation rate parameters enter only in the boundary condition, and availability of accurate data is limited. Certainly a model that describes the behavior of a nonisothermally operated crystallizer is needed if the temperature is to be manipulated, but there have been only a few studies of the effect of temperature on crystallization processes (Kelt and Larson 1977 Randolph and Cise 1972 Rousseau and Woo 1980). For isothermal crystallization, the terms involving Eg and Eh are absorbed into kg and kb, and only kg, g, kb, b, and i need to be estimated. 

Garside, J., Brecevic, Lj. and Mullin, J.W., 1982. The effect of temperature on the precipitation of calcium oxalate. Journal of Crystal Growth, 57, 233-240. 

Helt, J.E. and Larson, M.A., 1977. Effects of temperature on the crystallization of potassium nitrate by direct measurement of super-saturation. American Institution of Chemical Engineers Journal, 23(6), 822. 

We now describe a relatively simple MD model of a low-index crystal surface, which was conceived for the purpose of studying the rate of mass transport (8). The effect of temperature on surface transport involves several competing processes. A rough surface structure complicates the trajectories somewhat, and the diffusion of clusters of atoms must be considered. In order to simplify the model as much as possible, but retain the essential dynamics of the mobile atoms, we will consider a model in which the atoms move on a "substrate" represented by an analytic potential energy function that is adjusted to match that of a surface of a (100) face-centered cubic crystal composed of atoms interacting with a Lennard-Jones... 

Zinc sulfide, with its wide band gap of 3.66 eV, has been considered as an excellent electroluminescent (EL) material. The electroluminescence of ZnS has been used as a probe for unraveling the energetics at the ZnS/electrolyte interface and for possible application to display devices. Fan and Bard [127] examined the effect of temperature on EL of Al-doped self-activated ZnS single crystals in a persulfate-butyronitrile solution, as well as the time-resolved photoluminescence (PL) of the compound. Further [128], they investigated the PL and EL from single-crystal Mn-doped ZnS (ZnS Mn) centered at 580 nm. The PL was quenched by surface modification with U-treated poly(vinylferrocene). The effect of pH and temperature on the EL of ZnS Mn in aqueous and butyronitrile solutions upon reduction of per-oxydisulfate ion was also studied. EL of polycrystalline chemical vapor deposited (CVD) ZnS doped with Al, Cu-Al, and Mn was also observed with peaks at 430, 475, and 565 nm, respectively. High EL efficiency, comparable to that of singlecrystal ZnS, was found for the doped CVD polycrystalline ZnS. In all cases, the EL efficiency was about 0.2-0.3%. 

Pan ERE, Bard AJ (1985) Semiconductor Electrodes. 58. The effect of temperature on photo- and electroluminescence in Al-doped self-activated ZnS crystals. J Phys Chem 89 1232-1236... 

The effect of temperature on diffusivities in zeolite crystals can be expressed in terms of the Eyring equation (see Ruthven, gen. refs.). 

Reif 97) has observed the effects of point defects on nuclear resonance lines of Br , Br, Na , and Li in cubic crystals. The effect of temperature on the line widths and spin-lattice relaxation times was investigated for various impurity levels in AgBr and found to be quite pronounced due to vacancy association and diffusion. 

Figure 5(a). Effect of temperature on nucleation for seed density of 200 g/1. Number of crystals 1.2 lm) vs crystallization time. 

Drs. J. Owicki and M. S. Springate and I are currently attempting to apply liquid crystal continuum models to account for some of the effects of temperature on the activity of membrane-associated biochemical processes. This approach is also being used to estimate how close the... 

Figure 8. The effect of seeding on crystallization rates of mordenite from a hatch composition of 8.6 NazO-AWr-85 SiOz-182 HzO 4-5 NaCl as a function of temperature (8X2X8 imeter seed crystals)...

The effect of temperature on g is difficult to predict because effects such as solvatation, entropic thermodynamic have to be taken into account. Thus the phase transition of MCM-41 to MCM-48 can not be explained by using the packing parameter g when crystallization temperature increases. Some complementary studies (synthesis at lower and higher temperatures, XRD or SAXS measurements...) should be made to understand and explain the mechanism of phase transition. 

The procedure based on the direct use of the g tensor anisotropy and Eq. (2.24) is quite common for S = xh systems, since g values from frozen solutions are easily obtainable. In this case, both the second order Zeeman contributions and possibly the effects of temperature on the g values are neglected. Furthermore, the directions of the molecular axes are arbitrarily assumed unless single-crystal data are available. Attempts are available in the literature regarding low spin cobalt(II) [77] and copper(II) [61]. 

A measurement of the Kerr relaxation times in succinoni-trile(SN)as a function of temperature is shown in Fig. 2. The Kerr relaxation times measured show the effect of temperature on the rotational motion of the SN molecules as they undergo a change from the liquid to the plastic crystal phase. The data obtained from the Kerr gate measurement is shown along with a best fit curve from depolarized Rayleigh scattering (dotted line), and a best fit curve from dielectric relaxation measure-... 

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