Crystal growth of polyethylene from dilute solution: Growth kinetics of {110} twins and diffusion-limited growth of single crystals

1989 ◽  
Vol 27 (1) ◽  
pp. 53-70 ◽  
Author(s):  
Akihiko Toda ◽  
Hiroshi Kiho
Author(s):  
Qiao Chen ◽  
Jingyun Weng ◽  
Gabriele Sadowski ◽  
Yuanhui Ji

The influence of temperature, stirring speed, and excipients on crystal growth kinetics of mesalazine and allopurinol was investigated through experiment and chemical potential gradient model. The results indicated that the Diffusion-Surface Reaction model (DSR (1,2)) showed good performance in modeling API crystal growth kinetics within the ARDs of 4%. Excipients played a crucial role in inhibiting crystal growth in all the systems. It can not only improve the API solubility, but also reduce the crystal growth rate. By comparing diffusion rate and surface-reaction rate constant within the DSR (1,2) model, it was found that the controlling step of mesalazine crystallization was surface-reaction. Allopurinol crystallization was dominated by both surface-reaction and diffusion. Meanwhile, the crystal growth kinetics of mesalazine and allopurinol were predicted successfully with the ARDs of 2.53% and 4.78%. This work provided a mechanistic understanding of polymer influence on the inhibition of API crystal growth.


1997 ◽  
Vol 481 ◽  
Author(s):  
R. R. Chromik ◽  
W. K. Neils ◽  
E. J. Cotts

ABSTRACTThe kinetics of the formation of Cu3Si in Cu/a-Si diffusion couples have been investigated by means of differential scanning calorimetry and x-ray diffraction. Multilayered composites of average stoichiometry Cu3Si were prepared by sputter deposition with individual layer thicknesses varying in different samples between 2 and 100 nm. We observed diffusion limited growth of Cu3 Si upon annealing these diffusion couples below 500 K. Reaction constants were measured for a temperature range of 455 to 495 K for thicknesses of growing Cu3Si between 2.6 and 80 nm. The temperature dependence of the reaction constant, k2, was characterized as k2 = k0 exp(− Ea/kbT) with activation energy, Ea = 1.0 eV/atom and pre-factor, k0 = 1.9×10−3 cm2/s.


2013 ◽  
Vol 215-216 ◽  
pp. 903-912 ◽  
Author(s):  
Mary Hanhoun ◽  
Ludovic Montastruc ◽  
Catherine Azzaro-Pantel ◽  
Béatrice Biscans ◽  
Michèle Frèche ◽  
...  

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