Research On The Formation Of Uniform Particles Based On The Technology Of Magnetic Fluid

The formation of uniform particles has received great attention in the fields of electronic packaging,3D printing of micro-jet,ink-jet printing of two-dimensional digital image,micro-fluidic driving and controlling technology,new drug research and development,and biochemical detection.Therefore,there is great theoretical significance and practical value to carry out basic research on the production of uniform particles.In this paper,a new method for the formation of uniform metal particles by the control technology of differential pressure and the electromagnetic force driving(disturbance)was presented.The electromagnetic force as body force was directly produced in the driven cavity for the formation of the uniform metal particles by the technology of drop-on-demand(DOD)and continuous-ink-jet(CIJ).A corresponding test equipment for fabricating uniform metal particles was developed,which included pulse electromagnetic force generation system,pressure difference control and protection system,the temperature control system for heating and melting,the system for formation and collection uniform balls,and high-speed photography et al.A software testing system based on MATLAB was designed,which was used to measure the spherical degree of metal particles.The Ga_0.75In_0.25alloy was used as experimental material at room temperature to verify the feasibility for producing uniform droplets by the control technology of differential pressure and the electromagnetic force driving(disturbance)technology.The effects of input current frequency and gas pressure on uniform droplets formation were studied.The results showed that one droplet per cycle was produced by the electromagnetic force driving technology at a low frequency,and one droplet per cycle was produced by the electromagnetic force disturbance technology at a high frequency.The metal particles of Sn-58Bi were produced by DOD based on electromagnetic force technology and the control technology of differential pressure.The uniform liquid metal particles were produced by drop-on-demand technology at a small magnetic strength and current amplitude.The effect of the nozzle diameter,the input current waveform and frequency,the differential pressure,and the input current amplitude on the formation of uniform liquid metal particles were studied.The metal particles were produced by the device of balls formation.The results showed that:the one droplet per cycle and two droplets per cycle were produced by the present technology.The length of micro-column and the diameter of metal particles were controlled by the differential pressure.The break-up time of the tip of micro-column was controlled by the input current waveform.The metal particles with a spherical degree between 0-3%and diameter distribution between 0.6-0.65mm were produced at the nozzle diameter of 0.41mm and reasonable test parameters.The metal particles of Sn-58Bi were produced by the CIJ based on electromagnetic force technology and the control technology of differential pressure.This technology can produce metal particles at a higher frequency comparing with the metal particles fabricated by the DOD based on electromagnetic force technology.The effect of the nozzle diameter,the input current waveform and frequency,the differential pressure,and the input current amplitude on the formation of a uniform liquid metal particles were studied.The metal particles were produced by the device of balls formation.The results showed that the uniform liquid metal particles were produced without forming satellite droplets at the nozzle diameter of 0.21mm,0.30mm,and 0.41mm with reasonable test parameters.The metal particles with the spherical degree between 0-6%,the maximum error of the mean diameter of±4.2%and diameter distribution between 0.68-0.74mm were produced at the nozzle diameter of 0.41mm and reasonable test parameters.The metal particles with spherical degree between 0-3%,the maximum error of the mean diameter of±7.2%,the maximum error of the mean diameter of±5%accounted for 90%,and the production efficiency of 6.48 million particles per hour and diameter distribution between 0.32-0.37mm were produced with the nozzle diameter of 0.21mm and reasonable test parameters.The uniform water droplets were produced by the CIJ based on disturbance technology of electromagnetic force by a diaphragm and the control technology of differential pressure.The key problem,the electromagnetic force driving(disturbance)technology was only suitable for driving liquid metal,which was solved using the present technology.The effect of the nozzle diameter,the differential pressure,the disturbance frequency,the variation of the tip of jet-column,and the wavelength of the surface wave on the formation of uniform liquid metal particles was studied.The results showed that:the formation of the main droplet and satellite droplet was well controlled by adjusting the disturbance frequency at a constant nozzle diameter and gas pressure.When the uniform droplets were produced,the fluctuation range at the tip of the jet-column decreased with the increase of disturbance frequency,resulting in a decrease of water diameter.With the increase of disturbance frequency at the nozzle diameter of 0.15mm and reasonable test parameters,the diameter of droplets decreased gradually from 0.27 to 0.23mm by controlling disturbance frequency from2000 to 2600Hz.