Bubble Stability: From The Macro Scale To The Nanometer Scale

Bubble is a very common concept in many scientific areas. From the whole university to the economic phenomena around us, they are all treated as bubbles by the theorists. From a physicochemical view, a bubble is a globule of one substance into another, usually gas in a liquid. So how long does a bubble can live? The experiences tell that bubbles are always unstable and end in the following three situations,(1) Rupture(2) Dissolved in the solution(3) Growing to detach the wall, and finally float out the solutionA deliberation will let you recognize that this problem is not easy. First, the liquid/gas of bubbles interface has unique mechanical properties. When bubbles are dissolving or growing, the mass transport occurs at the liquid/gas interface. Moreover, the moving interface will drive the convective flow in the solution. In summary, the bubble phenomenon is a dynamical system involved multiphysics.In this thesis, we focus on the mass transport at the liquid/gas interface to study the stability of bubbles. In chapter one, we conceptualize the stability of bubbles using thermodynamics. In chapter two, we study the dissolution kinetics and discuss the dependence of lifetime on varied boundary conditions.Nanobubbles are relative new concepts in interfacial science. They can be simply regarded as nanoscopic gaseous bubbles formed at the interface when liquids encounter solids. However, the surprising stability of nanobubbles runs counter to classical thermodynamics. The extra pressure inside the bubbles should be so high that the bubbles should dissolve almost immediately. In chapter three, we start from two new experiments and propose two new properties of nanobubbles, i.e.(1) The mass transport occurred at liquid/gas interface is very slow(2) Nanobubbles are half-solid-like. The physical essence of these two properties is discussed here, and some experiments are proposed for validation.It is the aim of this thesis to help the new comers understand the stability of bubbles systematically. I hope this thesis can be a teaching material for graduate student majoring physical chemistry in future.