Control of crystal morphology

Kurimura, S. and Nakamura, R. (2005) Control of crystal morphology in dewetted films of thienyl dyes. Appl. Phys. A, 80, 903-906. 

Li S, Xu J, Luo G (2007) Control of crystal morphology through supersaturation ratio and mixing conditions. J Cryst Growth 304(l) 219-224... 

Moradian-Oldak. J. Amelogenins Assembly, processing and control of crystal morphology. Matrix Biol. 2001, 20. 293-305. 

Authoritative account of the control of crystal morphology by the use of tailor-made additives have been given by Davey, Polywka and Maginn (1991), Popovitz-Biro et al. (1991), Myerson (1999) and Davey and Garside (2000). 

There are literally thousands of reports in the scientific literature concerning the effects of impurities on the growth of specific crystals, and it would be superfluous to attempt a summary here. General reviews on the influence of additives in the control of crystal morphology have been made by Kem (1965), Boistelle (1976), Davey (1979), Botsaris (1982), Nancollas and Zawacki (1984), van Rosmalen, Witkamp and de Vreugd (1989), Davey et al. (1991) and Pfefer and Boistelle (1996). 

Bai, H., Zhang, W., Deng, H. et al. (2011) Control of crystal morphology in poly(L-lactide) by adding nucleating agent. Macromolecules, 44, 1233-1237. 

Systematic Control of Crystal Morphology during Preparation of Selective Vanadyl Pyrophosphate. 

Kestemann E., Merzouki M., Taouk B., Bordes E. and Contractor R.M. (1995). Systematic control of crystal morphology during preparation of selective vanadyl pyrophosphate , in Poncelet G., Martens J., Dehnon B., Jacobs P.A. and Grange P. (eds). Preparation of catalysts Vl.Stud Surf. Sci. Catal, 91, pp. 707-716. 

FIGURE 17.2 The control of crystal morphology by controlling the crystal face growth rates. If additives are adsorbed on a face that inhibit growth, the final surface of the crystal will be dominated by the slowest growing crystal face. 

Future experiments are planned to resolve the interrelationship of crystalline morphological dimensions and the population of tie molecules. This can be accomplished by control of crystallization conditions and the use of nucleating agents. That is, the size of spherulites can be varied without variation of lamellar thickness by addition of nucleating agents followed by crystallization at one temperature. Crystallization at different temperatures followed by annealing will allow comparison of samples having approximately the same lamellar thickness but different spherulitic diameters. Comparison of properties of samples prepared at different temperatures but with similar dimensions (obtained experimentally or by extrapolation) will allow estimation of the effect of tie molecules. 

Conventional synthesis methods offer limited control over desirable phase and elemental (bulk and surface) compositions, preferential exposure of active and selective surface planes, surface areas and pore structures of VPO catalysts, which define their catalytic performance in selective oxidation of n-butane. For instance, conventional methods produce VPO catalysts with relatively low surface areas (< 20 m7g) and a limited choice of crystal morphologies. 

Knowledge of crystal morphology and ways to control and predict the morphology of drugs and excipients could prove invaluable in formulation and product... 

Figure 3.3 WulfT plot for the derivation of equilibrium form. (From Powder Technology, 65, Understanding and Controlling the Crystal Morphology of Some Ionic Crystals, 219-225. Used by permission of Elsevier Science, 1991.)...

The third design feature is the polymer microstructure. Morphology of polymer can influence wear resistance of polymers. For example, in a semicrystalline polymer, both amorphous and crystalline phases coexist. The amorphous phase has been shown by Tanaka (8) to be weaker than the crystalline phase, thus the former wears faster than the latter. In addition to the difference in phases, the size of the spherulites and the molecular profile can also influence the wear rates. Thus, a control of the morphology through crystallization can improve the wear resistance of a polymer such as polytetrafluoroethylene (11). 

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