The Design and Experimental Research on Megasonic Dispersion System
|School||Nanjing University of Aeronautics and Astronautics|
|Course||Mechanical Manufacturing and Automation|
|Keywords||Megasonic dispersion PZT nano particles inverter power source emulsion|
Distinguishing from dispersion in traditional ultrasonic wave, this thesis proposes, for the first time, a pulsed megasonic dispersion technology in a bath trough type. Namely by using high frequency megasonic transducer with high efficiency, high speed sonic flow and strong sound pressure, which responsible for the material dispersion, are produced in liquid medium. Simultaneously, it is effective to suppress material damage which the tradition ultrasonic dispersion is unable to avoid because of the excessive cavitation inherited. This technology unifies supersonic technology, the advanced technique of manufacture and materials science, providing a new technical method for material dispersion. In the mean time, it features good energy controllability, cost efficiency and environmental friendliness. The megasonic dispersion technology has broad prospect of applications in the fields of material dispersion and preparation. Main contents in this thesis are as follows:1. Discussion about the megasonic dispersion mechanism on the basis of sound cavitation, cavitational air bubble kinematics and sonic flow. Theoretically prove that when the ultrasonic frequency exceeds 600 kHz, the cavitation threshold values up, while the number of cavitational air bubble reduces, thus the cavitation damage to the materials would be suppressed effectively. At the same time, this thesis initially discusses the process of energy conversion in this megasonic dispersion system, and analyzes the theoretical conditions required for the high speed sonic flow effect and the higher mode of sonic oscillation to be the main power in the megasonic sound field and the material dispersion process.2. Summary of design of the single element transducer and the process of manufacture. A mega Hertz inverter is designed and manufactured as power source. Debugging details of the input and output waveform of mega Hertz inverter recorded by an electric power analyzer.3. The application of megasonic dispersion method to nano particles dispersion, specifically PZT nano particles. The effects are characterized by Scanning Electron Microscopy, X-Ray Diffraction and Transmission Electron Microscopy. The results indicate a high efficiency and harmless effects.4. Preparations of O/W, W/O emulsion and ultra-large reverse micellar micro reactor are reported, as well as the initial study of non-emulsifier emulsion by the megasonic dispersion technology. The emulsion dispersivity is characterized by Measuring Microscope, which demonstrates that a combined refinement treatment by magasonic dispersion has the best dispersive effects.