Research On Gas Bubble Kinetic Behaviors Under The Condition Of Vacuum Boiling In The Micro-electro-deposition Space

Micro-electro-deposition technique is one of the key supporting technologies to achieve and promote the high quality, miniaturization and intelligent of high-tech products. However, the electrodeposition defects are often difficult to control and seriously weaken the quality and morphology of fine electrodeposition parts, or even directly cause it scrapped. The electrolyte vacuum boiling technique is considered to be applied to deposite the fine parts in order to reduce defects and improve the physical and mechanical properties in view of the peculiar process effect of depositing high quality nickel at a speed of up to 0.81mm/h without additives by this technique. The reasons that lead to these favorable results are highly related to the dynamic behavior of boiling gas bubbles besides the vacuum environment of degassing bubble and avoiding dust. This dissertation was supported by National Natural Science Foundation(51175152) and Henan Province University Science and Technology Innovation Talent Support Plan(2012HASTIT012), and kinetics behavior of boiling gas bubbles in micro space during the electrolyte vacuum boiling environment was taken as the research topic. The concrete contents were as follows:(1)The electrolyte vacuum boiling electrodeposition apparatus was developed with functions of phenomenon observation and data collection.(2) Dynamic behavior of bubbles in the microporous was studied, the results showed that, the growth of bubble in microporous is divided into three types, First, small gas bubbles float directly(diameter less than the diameter of 1/2), the second, gas column is formed then merge small bubbles generated of the cathode surface continuously under certain conditions, and departed from the aperture in the final form of big bubbles; the three, a lot of bubbles generated instantly from the cathode surface gather into a big bubble at the orifice and then escape in eruption style under the condition of high current density. Bubble departure diameter increase with vacuum, cathode surface temperature and depth to diameter ratio increases, but increases with the current density and then decreases. Bubble departure frequency increases with the increasing current density and the cathode surface temperature, but decreases with increasing depth to diameter ratio.Bubbles begin to appear the behavior of evident poly formation in multi-microporous. Gas-liquid two-phase flow in porous show the following evolution with increasing vacuum: calm flow(no significant bubbly flow)â†'weak bubblyâ†'bubbly flow streamâ†'strong bubbly flow, annular flow and annular dispersed flow will appear under certain condition. Parallel porous escaping bubbles affect each other.(3)The dynamic behavior of micro-bubble bath and gas-liquid two-phase flow model was concluded after analysis, growth of bubbles presents three different modes. Bubble departure diameter increase with the increasing current density, the cathode surface temperature and aspect ratio. Bubble departure frequency increases with increasing current density and temperature of the cathode surface increases, increases with decreasing depth to diameter ratio. There are three kinds of bubble coalescence behavior in micro groove. Liquid two-phase micro-groove-type are complex, changing and uncertain, including bubbly flow, slug flow, slug flow bubbly mixing, film slug flow, annular flow and gas-liquid phase flow other flow patterns. The process of bubbles departure from the groove notch is more complex.