Impluse response experiments of secondary nucleation of potassium alum

1990 ◽  
Vol 99 (1-4) ◽  
pp. 1082-1086
Author(s):  
Noriaki Kubota ◽  
Tsutomu Sato ◽  
Kenji Shimizu
Keyword(s):  
Secondary Nucleation ◽  
Potassium Alum

Continuous Precipitation of Lead Iodide

1994 ◽  
Vol 59 (7) ◽  
pp. 1503-1510
Author(s):  
Stanislav Žáček ◽  
Jaroslav Nývlt
Keyword(s):  
Growth Rate ◽  
Particle Size ◽  
Crystal Size ◽  
Crystal Growth Rate ◽  
Laboratory Model ◽  
Lead Iodide ◽  
Secondary Nucleation ◽  
Equimolar Ratio ◽  
Continuous Precipitation ◽  
The Mean

Lead iodide was precipitated from aqueous solutions of 0.015 - 0.1 M Pb(NO3)2 and 0.03 - 0.2 M KI in the equimolar ratio using a laboratory model of a stirred continuous crystallizer at 22 °C. After reaching the steady state, the PbI2 crystal size distribution was measured sedimentometrically and the crystallization kinetics was evaluated based on the mean particle size. Both the linear crystal growth rate and the nucleation rate depend on the specific output of the crystallizer. The system crystallization constant either points to a significant effect of secondary nucleation by the mechanism of contact of the crystals with the stirrer blade, or depends on the concentrations of the components added due to the micromixing mechanism.

Batch Crystallization with Crystals Attrition

1993 ◽  
Vol 58 (8) ◽  
pp. 1855-1860 ◽  
Author(s):  
Jaroslav Nývlt ◽  
Stanislav Žáček
Keyword(s):  
Mathematical Model ◽  
Calcium Sulfate ◽  
Crystal Size ◽  
Theoretical Description ◽  
Secondary Nucleation ◽  
Batch Crystallization ◽  
Batch Time ◽  
The Mean

The dependence of the mean crystal size of the products from batch crystallizers on the batch time occasionally exhibits a maximum, which can be explained by secondary nucleation due to the attrition of crystals. A kinetic equatation of nucleation, comprising a term for crystal attrition, can be used for the theoretical description of such behaviour. A mathematical model of a batch crystallizer with crystal attrition has been verified on the calcium sulfate precipitation.

Vibrational Spectra and Structure of Potassium Alum Kal(SO4)2·12[(H2O)x(D2O)1-x]

2004 ◽  
Vol 71 (3) ◽  
pp. 328-333 ◽  
Author(s):  
M. V. Barashkov ◽  
A. I. Komyak ◽  
S. N. Shashkov
Keyword(s):  
Vibrational Spectra ◽  
Potassium Alum

On the morphology of melt-crystallized polyethylene - II. Lamellae and their crystallization conditions

1981 ◽  
Vol 377 (1768) ◽  
pp. 39-60 ◽  
Keyword(s):  
Molecular Mass ◽  
Crystallization Temperature ◽  
Lamellar Thickness ◽  
Kinetic Regime ◽  
Secondary Nucleation ◽  
Constant Multiple ◽  
Linear Polyethylene ◽  
Simple Assumption ◽  
Crystallization Conditions ◽  
Prevalent Form

The microstructure of melt-crystallized linear polyethylene has been correlated with the variables of crystallization for most readily attainable conditions. All samples are filled with well defined lamellae with an aver­age chain inclination of about 35° to lamellar normals. The lamellar thickness depends upon supercooling rather than directly on crystalliza­tion temperature, which indicates that it is a kinetically determined quantity. The simple assumption that it is a constant multiple of the height given by secondary nucleation is, however, incorrect. Lamellar profiles depend only upon the crystallization temperature and molecular mass of the polyethylene concerned. They are independent of the extent of spherulitic development and are not determined solely by the kinetic régime in which crystals grow. Dominant S-shaped lamellae (Ss) and their associated subsidiary platelets are, nevertheless, the prevalent form for crystallization within régime II, i. e. in most cases of practical import­ance. The distinction between dominant and subsidiary lamellae is linked to fractional crystallization. At low supercoolings it is shown that shorter molecules are concentrated within subsidiary lamellae, and the trend to separate later-crystallizing species is likely to persist, to a lesser degree, even to quenched samples. With the use of added branched molecules this has been demonstrated to occur. The consequences of spatial segre­gation are likely to include increased vulnerability to mechanical and environmentally induced failure.

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