Solution studies ultrasound action

An ample and systematic study was carried out by G. Schmid and O. Rommel, which followed the ultrasounds action on the diluted solutions of many polymers, such as poly(vinyl acetate), poly(methyl methacrylate), cellulose nitrate in organic solvents [1117-1122]. Analysing the behaviour of fractionated and unfractionated polystyrene solutions under ultrasonic field, in all cases they found the decrease of molecular weight in time and proved that, finally, all samples tend to the same limit value of the molecular weight. Figure 3.386, [1117]. The authors reported the same results for a series of polyacrylates. 

The effect of ultrasound on the process of tellurium anodic dissolution in alkaline solutions was studied by the method of plotting polarization and galvanostatic curves [148]. Tests were made in NaOH solutions (concentrations of 0—20 g/L), subjected to the action of ultrasound at a frequency 17.5 kHz and using Te electrodeposited under ultrasound. The anodic polarization curves plotted without ultrasound and in its presence shifted with increased NaOH concentration towards negative values as a result of the increasing rate of Te anodic dissolution. The presence of ultrasound inhibited the process of Te anodic dissolution, probably due to the desorption of OFT anions from the anode surface. This sonoelectrodeposited Te thus showed greater corrosion resistance in alkaline solution than that deposited... 

Quite similar results have been described for the action of ultrasound on D-fructose solutions. After two hours, an absorption maximum was observed at 283 mu, probably showing the formation of reductone, as mentioned by Phillips. An effect on the specific rotation was also noted, but this was much less than that observed during some irradiation studies. An x-ray investigation proved that at least 15% of the parent sugar is changed to other products, but isolation of the products has not yet been attempted. ... 

Recently the synthesis of perovskite-type phases including barium titanate has been studied in terms of cavitation under the action of ultrasound. For example, the formation of monodisperse BaTi03 partieles at T < 90 °C in a strongly alkaline medium with the help of intense ultrasound has been studied in Ref. [272]. In the acoustic field, particles acquire a spherical shape and their size distribution has low variance, see Fig. 5.14. Barium titanate has been prepared sonochemically in aqueous solution according to the following reaetion... 

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