Relative crystallization times

As in the operation of chemical reactors, multistaging requires shorter residence time for the same performance. For the same L/G ratio, the relative crystallization times of k stages and one stage to reach the peaks are given by Eq. (16.26) as... 

Mossbauer spectra were recorded for the same samples four species for Fe3+ and two for Fe2+ were distinguished. The relation between their relative proportions and crystallization time are shown in Figs. 2A and 2B. RBS spectra are shown in Fig 2C. 

Transport phenomena and other dynamic processes in lyotropic liquid crystals have received relatively little research attention. However, they can be quite important in practice because relatively long times are often required to reach equilibrium when a liquid crystal is present. Moreover, understanding of equilibrium behavior seems to have reached a point where additional work on dynamic phenomena would be productive. Accordingly, the available information on such phenomena is reviewed. It consists mainly of measurements of viscosity, diffusivity, electrical conductivity, and chemical reaction rates in liquid crystalline materials. Some possible areas for future research are identified and discussed briefly. 

The development of the -modification is controlled by the relative crystallization thermodynamics and kinetics of the stable a-modification and of the smectic phase towards the metastable / -phase. For PP homopolymers, it is generally accepted that under isothermal conditions, the a-phase grows more rapidly at temperatures below 105 and above 140 °C than its counterpart, which in turn is more prone to develop in between these two temperatures in the presence of selective -promoters [52,70,122]. An elegant way to get fully nucleated /3-PP specimens would consist of pressing /3-PP pellets above their melting temperature (ideally more than 250 °C to erase any a-nuclei in the system), cool the melt quickly up to a crystallization temperature in between 100 and 130 °C, let the sample crystallize, and then quench it to room temperature [70]. However, such a processing method is too time-consuming to be of industrial relevance. 

Transuranium(III) hydroxides form from aqueous solutions at relatively high pH. Their stabilities are remarkably different. For example, Np(III) in the form of Np(OH)3 slowly oxidizes even imder anaerobic conditions [1]. Therefore, the Np(III) hydroxide has not yet been synthesized. The Pu(III) hydroxide Pu(OH)3 has a blue color. It can be prepared as an amorphous precipitate using NH4OH or NaOH. In contrast, Am(OH)3 (pink) and Cm(OH)3 (colorless) can be isolated from solution in the form of a jelly-like precipitate that, under heating, can be transformed into a frne-crystallized state. The crystallization time increases with temperature, and at 130°C (in the autoclave) may take more than one hour [2]. 

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