Crystallization in a confined space

The influence of sample thickness on the overall crystallization is best illustrated by the well-known fact that often the spherulitic crystallization in a thin film takes much longer time than that in a polymer bulk under the 

The instantaneous nucleation assumed, with the temperature dependent density D = 2.308 x 10 exp(-0.254 T) (mm ) (measured experimentally [44] and recalculated for 11-pm-thick film [10]), with temperature T expressed in Kelvin. The spherulitic growth rate temperature dependence according to the Hoffman equation g = GoQxp[-U[R(T - r )] exp -Kg[r(r - T)]- ] with U = 1500 caPmol, = 231.2 K, 

Depending on thickness of a polymer layer, rf, crystallization is usually treated as a 3D or 2D process if d is at least several times larger than a spherulite radius, it is treated as 3D, whereas if d is much less than a spherulite size, it is treated as 2D. However, there are intermediate cases when a more complex mathematical 

Calculation of the probability for A to be occluded at time t by one spherulite nucleated either inside a polymer or on polymer boundaries leads to the equations describing the respective components of conversion rate. Integration over time allows derivation of the separate expressions for two contributions to cr. the contribution from spherulites nucleated in the bulk of a polymer, a , and the contribution from those nucleated on the sample boundaries, respectively  

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Dacquin et al. [51] used a method called in situ crystallization in a confined space to prepare a LaNiOs/SBAlO catalyst. As evidenced by TEM analysis, very small nanoparticles of perovskite were generated within the silica porosity with a size between 2 and 5 nm and an average closed to 3 nm. The reduction step performed at 700 °C gives Ni° particles well dispersed within the matrix porosity and their size remained close to the support pore size. The catalytic activity for syngas production was doubled compared to bulk LaNiOs precursor, it remains... 

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