Ultrasound initiated crystallization

The reactive crystallization has some peculiar characteristics like insoluble product, initiation of reaction by change in pH and conductivity. In this case the solution becomes saturated and eventually supersaturated with respect to reactant nucleation [30], The ultrasound assisted decomposition precursors includes dissolving metal organic precursors in organic solvents/water with the assistance of surfactants leads to monodisperse and reduced metal/metal oxide nanoparticles. 

The claims of exclusive formation of rac-stilbene dichloride upon gas-solid addition of chlorine to frans-stilbene (103) [71] and of meso-stilbene dibromide in the gas-solid addition of bromine to trans- or czs-stilbene [54] could not be verified. Scheme 12 shows the results of more detailed studies indicating the mesolrac ratios on the solid-state chlorination and bromination of trflns-stilbene (103) and some variations when the crystal size was changed [58, 60-61]. There is a risk of partial transient liquefaction if the chlorine is added too rapidly, due to initially heavy reaction. But even at the start with a stoichiometric amount of chlorine at 0.1 bar and 0 °C, a persistent product layer forms on the unground crystal powder of 103 that cannot be disintegrated by the ultrasound of a cleaning bath at 20 °C for 60 h (only 7% conversion with mesolrac ratio of 11 89 under these conditions) [22]. It is therefore unavoidable to mill the crystals of 103 to sizes <1 pm in order to overcome these rare diffi-... 

Ultrasound is by far the most sensitive technique for detecting the initial stages of crystallization. Ultrasound velocity is very sensitive to the state of fat in a dairy emulsion (Figure 21.2) and can be used to follow changes in the amount of solid fat which occurs as the temperature changes. 

The manipulated variables for the optimization are the mass flux over the membrane (J) and the ultrasound utilization rju). Figure 7 shows the optimal trajectories of the manipulated variables. The results illustrate the strength of the task based design approach. In this case a very tight constraint on the growth rate has been imposed. It can be seen how both the flux and the utilization of ultrasound work together to maximize the crystal mean size. In the initial phase the ultrasound and flux are both high to create... 

It has been proposed that the absorption of ultrasound energy depends on the thermo-elastic relaxation of ice crystals in food and is affected by ice crystal orientation and size, impurities present in the ice crystals, as well as temperature (Kissam et al., 1981). Miles and Shore (1978) and Shore et al. (1986) found that ultrasound was more attenuated in frozen meats than in unfrozen tissues and that the attenuation increased markedly with temperature, reaching the maximum near the initial freezing points of the foods before decreasing rapidly at higher temperatures, thus making ultrasound particularly suitable for the controlled thawing of foods (Miles et al., 1999 Torley and Bhandari, 2007). 

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