High-intensity ultrasonics

For general aspects on sonochemistry the reader is referred to references [174,180], and for cavitation to references [175,186]. Cordemans [187] has briefly reviewed the use of (ultra)sound in the chemical industry. Typical applications include thermally induced polymer cross-linking, dispersion of Ti02 pigments in paints, and stabilisation of emulsions. High power ultrasonic waves allow rapid in situ copolymerisation and compatibilisation of immiscible polymer melt blends. Roberts [170] has reviewed high-intensity ultrasonics, cavitation and relevant parameters (frequency, intensity,... 

O.V. Abramov, High-Intensity Ultrasonic Theory and Industrial Applications, Gordon Breach, New York, NY (1998). 

The submitters used Heat Systems-Ultrasonics Model W-220 (maximum output power 200W) with a standard horn. The checkers used a Sonics and Materials Inc. Vibra-Cell High Intensity Ultrasonic Processor (maximum power outlet 600W)... 

Abramov, O.V. High-Intensity Ultrasonics Theory and Industrial Applications,... 

M.G. Sirotyuk, Experimental investigation of ultrasonic cavitation, in L.D. Rozenberg (Ed.), Physics and Technology of High-Intensity Ultrasound, Vol. 2, High-Intensity Ultrasonic Fields, Nauka, Moscow, 1968. 

Rozenberg, L. D.. High-Intensity Ultrasonic Kelds, pp. 263-340. Plenum, New York, 1971. 

High-Intensity Ultmsonicator. Droplets are disrupted within a field of high-intensity ultrasonic waves. Droplet disruption occurs either due to cavitation or because the frequency of the ultrasonic wave equals the resonance frequencies of the droplets. This causes the droplets to oscillate vigorously. Eventually, the oscillation becomes supercritical and the droplets are disrupted. The effectiveness of sonication, therefore, depends on the nature of the continuous and dispersed phase. The type of oil, as well as the nature of the surfactant, is the limiting factor for the minimal droplet size that can be achieved. 

Nowadays nanocomposites are used in a broad variety of technical and scientific fields since they possess useful mechanical and chemical properties. Nanocomposite systems can be derived from different materials. Among these, clays are widely applied because their layered structure with high active surface area and cation exchange capacity has advantages for nanocomposite production. A possible way to improve and accelerate the incorporation of polymers (surfactants) into clay layers is the application of high-intensity ultrasonic treatment on to the suspension of a clay mineral in the presence of polymer (surfactants) molecules. Sonication promotes a drastic decrease of the incorporation time increasing the interlamellar space of clay minerals. 

It is more difficult to prepare III-V semiconductors than the II-VI. Two sonochemical investigations reported on the preparation of these materials. The first paper details a safe method for the preparation of transition metal arsenides, FeAs, NiAs, and CoAs [142]. At room temperature, well-crystallized and monodispersed arsenide particles were successfully obtained under high-intensity ultrasonic irradiation for 4 h from the reaction of transition metal chlorides (FeCla, NiCl2, and C0CI2), arsenic (which is the least toxic arsenic feedstock) and zinc in ethanol. Different characterization techniques show that the product powders consist of nanosize particles. The ultrasonic irradiation and the solvent are both important in the formation of the product. 

Similarly, as shown in Reactions (10) and (11), under high-intensity ultrasonic irradiation, InP nanocrystallites were synthesized in ethanol/benzene mixed solvent at room temperature [46]. 

Brown, B. and Goodman, J.E. High Intensity Ultrasonics, ILiffe Books Ltd, London, 1965. 

It is well known that some amounts of cavities or small bubbles are present in rubber during any type of mbber processing (Kasner and Meinecke, 1996). The formation of bubbles can be nucleated by precursor cavities of appropriate size (Gent and Tompkins, 1969). The proposed models (Isayev et al., 1996a,c,d Yashin and Isayev, 1999,2000) were based upon a mechanism of rubber network breakdown caused by cavitation, which is created by high intensity ultrasonic waves in the presence of pressure and heat. Driven by ultrasound, the cavities pulsate with amplitude depending mostly upon the ratio between ambient and ultrasonic pressures (acoustic cavitation). 

Baxter, S., Zivanovic, S and Weiss, J., Molecular weight and degree of acetylation of high-intensity ultrasonicated chitosan. Food HvdrocoUoids. 19 (2005), 821-830. 

The milled rice straw pulp fiber was soaked in distilled water for more than 24 h, and then treated by high intensity ultrasonication (Sonics Materials. INC, CT, 20kHz, Model 1500 W) for 30 min with 80% power level. After ultrasonication treatment, the obtained RSF aqua compound was kept in frozen. 

Gonzalez, J. R., Alcantara, R., Nacimiento, R, Ortiz, G. R, Tirado, J. L., Zhecheva, E., and Stoyanova, R. [2012]. Long-length titania nanotubes obtained by high-voltage anodization and high-intensity ultrasonication for superior capacity electrode, / Phys. Chem. C, 115, pp. 20182-20190. 

---