Study On The Effect Of Silicone Defoamer On Nano - Bubbles

In recent twenty years, the interfacial nanobubbles had become one of the hot topics in the study of physics, and its existence had been confirmed by a variety of characterization methods. According to the research findings, interfacial nanotubbles have a great effect on the nanotechnology, interface science, fluid mechanics, biology and other fields. Since they could cause fluid slippage on the interface and reduce the flow resistance, nanobubbles could be applied to surface adhesion, colloidal dispersion, ore flotation, waste disposal, etc. Therefore, it is very necessary to study interfacial nanobubbles due to the important theoretical significance and application value. Classical thermodynamic theory proved that the lifetime of interfacial nanobubbles in the water was only a few microseconds. However, a large number of experiments had confirmed that interfacial nanobubbles could exist for a few days in solution, and AFM also directly detected the interfacial nanobubbles. The abnormal long lifetime of nanobubbles posed challenges to traditional views about the gas behavior in solid-liquid interface and it may be applied in many fields. So the stability of the nanobubbles is still a mystery.The first chapter is literature review which mainly introduced morphology features, preparation methods and the existence theories of interfacial nanobubbles. In addition, it also introduced antifoaming principles and the composition of organic silicon defoamer.In the second chapter, we used organic silicon defoamer to explore the stability of nanobubbles since its good antifoaming effect. We explored the effect of organic silicon antifoaming and interfacial nanobubbles(average grain diameter<100nm) and the effect of organic silicon defoamer and the interface micro-nanobubbles(average grain diameter≥100nm) respectively. The experimental results showed that ethanol-water replacement producing nanobubbles or micro nanobubbles, organic silicon defoamer molecules could not affect the stability of the bubbles. It showed that the surface structure of nanoscale bubbles may be different from the macroscopic bubbles, its surface tension may be bigger than the macroscopic bubble. Besides, defoaming agent particles have large particle size(average particle size of 347.8 nm), but the volume of micro-nano bubbles are very small, so the defoaming agent particles that adsorbed on the surface of bubbles are little, although they can lead to the bubbles deformation but not enough to damage their surface structure.In the third chapter, since AFM was chosen to study the nanobubbles, it was quite necessary to understand the working mechanism of AFM. The work-mode and parameters setting would affect the AFM image quality. In this chapter, we studied various parameters and the impact from external factors on the interfacial nanobubbles imaging and made detailed instructions. The various parameters settings were detailed described for the next stage study interface nanobubbles by means of AFM. Meanwhile, some phenomena and the results appeared in the effect of organosilicon defoaming agent and interfacial nanobubbles were also further analyzed.In chapter four, we studied the effect of organic silicon defoamer and bulk-phase nanobubbles. The experimental results showed that the volume of ethanol and water mixture proportion was different, it could produce different diameters of bulk-phase nanobubbles. Besides, the same concentration of organic silicon defoamer had effect on bulk-phase phase nanobubbles of different diameters. It could make the quantity and the diameter of nanobubbles became small in mixed solution. Different concentrations of organic silicon defoamer solution also had some influence on the same diameter of the nanobubbles. It could make the quantity and the diameter of nanobubbles became small in mixed solution. But nanobubbles would not disappear completely, there were always a part of nanobubbles with small diameter in mixed solution, and the quantity is small. Finally, by comparing the experimental results, it could found that the stability of interfacial nanobubbles and interfacial micro nanobubbles were relatively more stable than bulk-phase nanobubbles. Interfacial bubbles had small contact area with defoaming agent particles. The three-phase pinning line of interfacial bubbles also promoted the stability of the bubble.The fifth chapter is summarization and prospect.