Ultrasonic vibration mixing

Fig. 13.18. Heterodyne mixed signals from ultrasonic vibration around 9 MHz of the sample and the cantilever, with difference frequencies (a) 5 kHz, (b) 15 kHz. The upper traces are from conventional electronic mixing of the excitation waveforms, the lower signals are from the cantilever response, with mixing occurring mechanically at the tip-sample contact. The electronically mixed waveforms were rectangular, giving rise to the triangular beat waveforms (Kolosov and Briggs 1996).

SiC-coated or uncoated MWCNTs are dispersed in isopropylalcohol (IPA) using ultrasonic vibration for 5 min. Then the SiC-coated or uncoated MWCNTs are mixed with fine WC and cobalt powders (10 wt% cobalt) in IPA using plastic balls (10-20 mm in diameter) for 5 h. After ball milling, the IPA solution is evaporated by stirring using an electric heater and then dried at... 

FIGURE 3.47 The ultrasonic mixing process, (a) Videocamera scene at standby state. Ethanol and water were in laminar flow. Limited diffusion occurred at the interface of the ethanol and water flows, (b) Ultrasonic vibration ON. The laminar flow changed and turbulence occurred, (c) After 2 s of ultrasonic vibration, ethanol was mixed well with water, (d) Ultrasonic vibration OFF. The laminar flow resumed [327]. Reprinted with permission from Wiley-VCH Verlag. 

A pH titration of the suspension solutions of NaBir or NiBir in Ni(N03)2 solution was carried out similarly as that for preparation of Ni(OH)2-montmorillonite mixed layered compound described by Yamanaka et al. [15], Separate NaBir and NiBir (dried at 80°C) were dispersed in Ni(N03)2 solution (O.IM), and agitated by ultrasonic vibration for 30 min. Then these suspensions were potentionmetrically titrated with a NaOH solution. The pH value at each stage of the titration was measured by a HORIBA F-22 pH meter. The titrated suspension was stirring for 10 min before the pH measurement at each stage of the titration before pH=8, 5 min before pH= 10, and 2 min to the end. A pure water and one with dispersed NiBir as well as a pure Ni(N03)2 solution were also similarly titrated for comparison. 

The mixing for W/O emulsions is usually performed in the laboratory by simple equipment like a magnetic stirrer, an ordinary mechanical stirrer with multiple fins, a planetary stirrer, a high shear / high speed blender, an ultrasonic vibrator or in some cases a sonic disruptor [18]. Ordinary rotational mixing can be coupled with sonication for obtaining relatively small droplets [42]. 

Sonogel Gel obtained when the mixing of the precursor, solvent, and water is enhanced by ultrasonic vibrations (sonication)... 

Loosely linked with dispersion is the process of removing small particulate material from the surface of larger pieces. This has been employed in the process of coal beneficiation, where 20 tons per hour of a fine waste coal mixed with an equal amount of water can be treated. The equipment is relatively simple, involving an ultrasonically vibrating tray over which the mixture is passed, and it requires only 2 kW of ultrasonic energy. ... 

The oil (or alkyd) was mixed with the emulsifier solution while dispersed with the Braunsonlc Ultrasonic Vibrator which formed a pre-emulsion. 

Miaowave irradiation was successfully used to prepare nanocomposites of polystyrene silica (PS/SNs) with diffaent contents of inorganic nanofilfets by in situ bulk radical copolymerization of styrene with methacryloxypropyl silica nanopartides (MPSNs). Unda optimized condition, 33% of grafting could be achieved with 98% convasion of styrene. In a typical experiment, MPSNs were mixed with styrene and a certain amount of AIBN with ultrasonic vibrations for 30 min. Then the mixture was irradiated in a miaowave oven (700 W) for lOmin with a diffaent power." ... 

Researches on studying of separation properties were spent on metal dual-lead vortex tube Z)=125-2.5mm with a diameter on a thread of 175mm with a variable depth of thread from 10 to 25mmwatercolumn of cutting of 8.5, a conditional outlet angle of gas a =78°. Superposition of ultrasonic vibrations for clearing of a gas mix was spent with the following fasted frequency 18.5 21.6 22.1 23.5 kc. The best results are had at frequency of ultrasoimd 21.6 kc. 

This technique is used mainly for nonpolar compounds. Typically a small aliquot of soil (10-30 g) is dried by mixing with sodium sulfate prior to extraction. Next, the sample is extracted with a solvent for 10-20 min using a sonicator probe. The choice of solvent depends on the polarity of the parent compound. The ultrasonic power supply converts a 50/60-Hz voltage to high-frequency 20-kHz electric energy that is ultimately converted into mechanical vibrations. The vibrations are intensified by a sonic horn (probe) and thereby disrupt the soil matrix. The residues are released from soil and dissolved in the solvent. 

Jin and Park processed the Al O -epoxy nanocomposites by hot curing technique [69]. Zheng et al. prepared the SiO -epoxy nanocomposites by mixing the nanoparticles in epoxy matrix at 120°C [4]. Similarly, SiO -based thermoset polyester nanocomposites are prepared by mechanical mixing followed by ultrasonication [72]. Alumina-epoxy nanocomposites are also processed in-situ by reducing the size of alumina particles from micrometer range to nanometer range with the assistance of mechanical vibrator [73]. 

Instead of vibrating a surface directly, ultrasound can be used to create rapid movement in a fluid adjacent to a heat exchanger surface. The effects of ultrasound are commonly witnessed in ultrasonic cleaning baths, for removing contamination from the surfaces of metal objects, for example. Ultrasound, as discussed later, is used to enhance reactions and mixing - see for example Prosonix in Appendix 4. With regard to heat transfer enhancement ultrasound is stiU in its infancy, and the main thrust in recent years has been to enhance reactions - discussed in Section 3.4 in the context of electrical enhancement. 

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