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STEADY-STATE TRANSITIONS AND POLYMORPH TRANSFORMATIONS IN CONTINUOUS PRECIPITATION OF CALCIUM-CARBONATE

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Title STEADY-STATE TRANSITIONS AND POLYMORPH TRANSFORMATIONS IN CONTINUOUS PRECIPITATION OF CALCIUM-CARBONATE
 
Creator CHAKRABORTY, D
AGARWAL, VK
BHATIA, SK
BELLARE, J
 
Subject crystallization
monolayers
 
Description The continuous precipitation of calcium carbonate is studied here with on-line particle size distribution evaluation and in-situ video visualization. Morphological characterizations of collected samples using differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and cryo-SEM were also performed. It is found that in a scaled reactor the nucleation is homogeneous and predominantly of vaterite which transforms to calcite within the reactor itself, and subsequently outside the reactor during sample collection and drying. In an unsealed reactor the precipitation is predominantly heterogeneous with both vaterite and calcite being nucleated. The heterogeneously nucleated material is morphologically more perfect and is therefore slower to transform and has a lower growth rate. As a result of the transformation of vaterite, conventional characterizations such as DSC, XRD, and SEM, involving sample collection, filtration, and drying, at room temperature are unreliable. More meaningful determinations are available from cryo-SEM studies of rapidly frozen samples in which the transformation and subsequent nucleation is arrested.
 
Publisher AMER CHEMICAL SOC
 
Date 2011-07-14T21:47:29Z
2011-12-26T12:47:38Z
2011-12-27T05:37:46Z
2011-07-14T21:47:29Z
2011-12-26T12:47:38Z
2011-12-27T05:37:46Z
1994
 
Type Article
 
Identifier INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 33(9), 2187-2197
0888-5885
http://dx.doi.org/10.1021/ie00033a024
http://dspace.library.iitb.ac.in/xmlui/handle/10054/4077
http://hdl.handle.net/10054/4077
 
Language en