What are the mechanism of distribution nanoparticles by using ultrasonic waves in the manufacture of cast aluminum nanocomposites?
Ultrasonicators are used to disperse nano size particles in a medium. The device emits sound waves either using a probe or water bath to disperse the nano particles effectively.
I am not sure, what method you are using for preparation of the composites. But in general, the nano particles can be distributed homogeneously in a suspension using ultrasonic bath. Refer this paper:
http://www.sciencedirect.com/science/article/pii/S0032591007005694
Dear Somayeh Kord
By so called transient cavitations mechanism.
www.fracturae.com/index.php/MST/article/download/1136/1088
Best regards
Ultrasonic radiation when pass through the medium, Nano particles of the medium absorb energy and move so that they may form new arrangement however, their uniform arrangement or distribution depends on the intensity of ultrasonic radiation or the energy absorbed by the nano size particles.
Unfortunately, the sound effectively interacts with a particle when resonant conditions are fulfilled. It means that [Ultrasound freq.] = [Sound velocity]/[Particle size]. For typical values C~10E3 m/s, D~10E-6 m it gives the resonance frequency in a GHz range. Surely, this frequency can not be done with traditional techniques. More likely any results may be obtained with USP laser-generated ultrasound.
What are the mechanism of distribution nanoparticles by using ultrasonic waves in the manufacture of cast aluminum nanocomposites?. Available from: https://www.researchgate.net/post/What_are_the_mechanism_of_distribution_nanoparticles_by_using_ultrasonic_waves_in_the_manufacture_of_cast_aluminum_nanocomposites [accessed Apr 26, 2017].
I am not sure I agree with your evaluation of the relevant resonance. If you were correct, the same argument would apply to dirt particles in water, giving 1 GHz for 1 um particles and 1,000 m/s sound speed . Yet we know dirty water cavitates easily at kHz frequencies.
Instead, gas pockets (bubbles) trapped in or around the particles are the resonating structures, with freq given by Fres = Sqrt(3*gam*Po/rhol)/(2*Pi*R) where gam is the ratio of the gas specific heats (~1.4), Po the ambient pressure (100,000 Pa), rhol the liquid density (1000 kg/m3), Pi ~ 3.142, and R the bubble radius (m). For a 150 um bubble, Fres is around 20 kHz.
Furthermore, even if there are no bubbles of this size, a large enough acoustic amplitude will expand much smaller pockets to larger sizes, due to gas diffusion from surrounding liquid. This is the most common occurrence.
For the case of cavitating in liquid Al with embedded nanoparticles, the particle itself is not the nucleus but the pocket of gas surrounding it. Given the higher liquid density but larger (hydrostatic) Po compared to water, Fres should be of the same order as for water. The one factor that might change is the minimum acoustic pressure needed for cavitation (higher cavitation threshold) due to higher surface tension of liquid Al.
Hope this helps.
What are the mechanism of distribution nanoparticles by using ultrasonic waves in the manufacture of cast aluminum nanocomposites?. Available from: https://www.researchgate.net/post/What_are_the_mechanism_of_distribution_nanoparticles_by_using_ultrasonic_waves_in_the_manufacture_of_cast_aluminum_nanocomposites [accessed Apr 26, 2017].
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