Recrystallization phenomena of solution grown paraffin dendrites

Paraffin crystals were grown from decane solutions using a micro-Bridgman s et up for in-situ observation of the morphology at the growth front. It is shown that for large imposed velocities, dendrites are obtained. After dend ritic growth, aging or recrystallization processes set in rather quickly, c hanging the crystal shapes considerably from the well-known dendritic shape s of melt grown dendrites. It is shown that several factors may cause these post-growth shape transitions: surface minimization, uptake and subsequent sweating of solvent material, and polymorphic phase conversion. It is show n that the first two recrystallization mechanisms are the most important fo r tricosane (n-C23H48) and pentacosane (n-C25H52) dendrites. Surface minimi zation by increasing the thickness of the crystals is particularly favorabl e. For dotriacontane (n-C32H66) dendrites, the recrystallization behavior a ppears to be less dramatic. It is shown that the uptake and sweating out of solvent material afterwards may lead to formation of holes within the dend rites. (C) 2001 Elsevier Science B.V. All rights reserved.