Driving force recrystallization

The resulting complex salt is so stable that it can be recrystallized from water. In this system, five hybridized carbon atoms are necessarily held in a cissoid configuration. More recently, Pettit and co-workers 192, 193, 194) have studied acyclic systems of this type and have found that there is a strong driving force for a cissoid configuration of the resulting TT-pentadienyl-iron tricarbonyl complexes. 

Aside Classical primary recrystallization is the nuclea-tion and growth of new strain-free grains in a matrix of heavily deformed material. The driving force arises from the decrease in strain energy. There is an induction period as the system forms stable nuclei. 

The hardness profile now indicates that the driving force for recrystallization and... 

Impedance diagrams measured during a Hj sorption experiment on a 125 pm thick Pd Agjs membrane (a) before and (b) after recrystallization using the same driving force AP= 150 mbar at T= 150°C. 

In the modified approach a thermo-mechanical treatment was devised, where the final reheating temperature was lowered to around 1100°C (to ensure very low finishing temperature) and adequate final reduction of 25%, so as to derive adequate driving force for recrystallization during subsequent solution treatment. Figure 2 shows the flow chart for manufacture of ring forgings. 

Compared to lyotropic LCNP the thermotropic mesophase-based supercooled smectic nanoparticles are in a still much more early stage of development. Although structural aspects of these nanoparticles are not quite as complex as with lyotropic LCNP and the physicochemical properties of these nanoparticles as well as the influencing parameters on the phase behavior have been studied in some detail yet much remains to be done for further optimization of the formulations in particular with regard to the stability of the nanoparticles against recrystallization. Furthermore, application related studies have to be performed, especially with a focus on parenteral drug delivery which was the main driving force for the development of these particles. 

The procedure of evaluating thermodynamic parameters in terms of their configurational properties is an attempt to incorporate not only the properties of the amorphous form but also of the original crystalline state, as the driving force for recrystallization is the energy difference between these two states. 

Figure 6.2 Schematic of a solubility curve due to a form change and precipitation of a less stable form (curve C) at equilibrium, the curve will level out to the solubility of the less soluble form. Line B represents the less soluble form. Curve A represents a stable form which is under-saturated with respect to the less soluble form, while curve D represents a stable form that is supersaturated with respect to the less soluble form. The phenomenon observed for curve D is rare, due to the large driving force towards recrystallization. Reproduced with permission from Schultheiss and Newman, ref. 23, Copyright 2009 American Chemical Society.

SA side chains recrystallize and form physical crosslinks. In this situation, the main chains are restricted in their conformations and fixed at a reduced entropic state. When the gel under such conditions is reheated above the transition temperature, the SA side chain crystals melt and the main chains move towards the direction of increased entropy (entropy elasticity). The siun of the movement of each main chain becomes the driving force for the recovery of the macroscopic shape. The hydrophobic SA of this gel forms crystalline domains, which are incompatible with water. Therefore,... 

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