Fundamental Research On Micro And Nano Electrochemical Machining

With the development of science and technology, the size of parts and components becomes more and more miniaturized, such as the sensors in aerospace aircraft, micro pump in the nuclear research, gyroscope in the smart phones, micro clamp in medical treatment, etc. These miniaturization demands indicate that the micro/nano machining technology will become a research hotspot in the high-tech world in future. As one of micro machining technology, the electrochemical machining technology is also developing towards the micro-nano scale.Micro/nano scale electrochemical machining technology is carried out in this paper. The main studies and contributions in this dissertation are as followings:(1)According to the basic principle of electrochemical machining, the characteristics of micro/nano electrochemical machining were expounded. The electrode reaction and the electrode/solution interface status during electrochemical process were analyzed, and the influence of ultrashort pulses on the electrochemical machining was discussed. The transient mechanism of micro/nano electrochemical machining was also discussed.(2)In order to satisfy the requirements of the micro/nano electrochemical machining, the micro/nano electrochemical machining system was developed. The system mainly includes vibration isolation unit, micro/nano drive unit, electrodes unit, electrolyte unit, ultrashort pulse power supply, auxiliary visualization unit, tool setting unit, control unit and so on.(3)The current amplitude mutation of ultrashort pulse was proposed as the method of tool setting. Based on the pulse power with ultrashort pulse width and tool setting unit with sampling rate of 5GS/s, the submicron tool position could be precisely located by monitoring the sudden change of peak pulse current in the route. The problems of tool deformation and spark discharge in the tool setting process could be avoided by the proposed method.(4)Ag nanowire was tested as the tool electrode of micro/nano electrochemical machining. The dissolving problem of Ag nanowire in electrochemical machining was analyzed and solved by optimized the thickness of sputtering layer. The experiments results indicate that the thickness of the sputtering layer of about 150 nm is appropriate to electrochemical machining, and the tool electrode with 400 nm in diameter could be obtained. By using H2SO4 solution of 0.1 mol/L concentration, the pulse generator with 50 ns in period, 6 ns in pulse on-time and 4 V in voltage, a submicron groove with the depth of 80 nm, minimum bottom width of 450 nm and maximum entrance width of 1000 nm has been prepared successfully with sputtered Ag nanowire as the tool electrode.(5)The mathematical model of liquid membrane electrochemical etching of nano tool electrode was established. The parameters which influence the dimension and morphology of the fabricated tool, such as the initial tungsten rod radius, the length of the lower tip, the thickness of the liquid membrane, the etching voltage and the electrolyte concentration were optimized. And the optimal machining parameters are the following: initial tungsten rod radius of 100 μm, the length of the lower tip is 10 mm, the thickness of liquid membrane is 4mm, processing voltage of 3V and potassium hydroxide electrolyte concentration of 0.5 mol/L. Using these optimal machining parameters, an tool electrode with 76 nm in diameter was obtained in several minutes. By using H2SO4 solution of 0.05 mol/L concentration, the pulse generator with 1μs in period, 100 ns in pulse on-time and 4 V in voltage, a micro/nano groove with the depth of 55 nm, minimum bottom width of 100 nm and maximum entrance width of 1400 nm has been obtained in the superalloys workpiece.