| Inertial confinement fusion(ICF)is not only expected to completely solve the energy crisis,and has important theoretical and practical significance on the study on the material evolution under extreme conditions,such as the origin of the universe.To perform ICF experiments,since the 1960 s,many countries in the world have successfully built or are building ICF facility,China also carried out the construction of the SG facility.And the ICF laser facility has been treated as an important symbol of national security,energy and scientific research.However,owing to the contamiannts adsobed onto surface and subsurface of components,the ICF facility has been faced with serious problem of surface damge of the optics components,one of the main reaons should be the pollutants inside ICF facility.How to obtain and maintain the ultra-clean state of the internal optical elements and metal mechanical parts is one important bottleneck problems to restrict the development of ICF technology,which needs to be urgently solved.In order to obtain the components meeing the performance demand of the ICF facility,workpieces should be cleaned by adopting appropriate pollutants removal methods.Thus it is necessary to comprehensively understand the adsorption behavior and removal mechanim of pollutants on the workpiece surface.However,if the study is concuted by relying solely on experiments,it is not only diffucult,and with heavy workload,but also extremely costly.It's widely known that molecualr dynamics simulation can reveal the mechanism of the adsorption and removal of pollutan ts on workpiece surface from the microscopic view.Thus,by using molecular dynamic simulations,the dissertation focused on the adsorption behavior and removal mechanism of pollutants on processed aluminum surface is conducted from following parts:Firstly,taking the surface cleaning method,in which water solution is the main cleaning medium,as the research objective,the conformational change and detachment of oil contaminants on perfect Al2O3 surface in aqueous solution was deeply investigated.The diffusion of water molecules on Al2O3 surface contaminated by oil molecules and its driving forces were analyzed.Then the residual mechanism of oil contaminants on perfect Al2O3 surface was revealed.On this basis,the effects of molecular weights on the conformational change and even detachment of oil contaminants were obtained.The simulation results indicate that in aqueous solution,the conformational change and even detachment of oil contaminants on perfect Al2O3 surface is conducted in the form of “roll-up”.However,due to the effect of different adsorption contents of oil contaminants,the conformational change processes of oil contminants could be divided into two types.Under the action of water solution,oil contaminants at low adsorption content c ould be thoroughly detached from substrate surface.The entire detachment process consists of the slight conformational change of oil contaminants on the substrate surface at the early stage,the migration process of oil contaminants in aqueous solution,and the quick motion of oil from aqueous solution to air/solution.At high adsorption content,despite of the evident conformational change,oil contaminants could not be thoroughly detached from substrate surface.At the end of simulation,oil contaminants are existed as ordered adsorption layers of oil molecules,which are stably adsorbed onto the hydrated substrate surface.The conformational change process is composited of the slight conformational change of oil contmainants at the early stage,the drastic conformational change of “ordered?disordered?ordered” and the "homogenization" process in the system equilibrium stage.In the cleaning process of workpiece,surfactant molecules are usually added into the cleaning solution to improve the removal effciency of contaminants.Moreover,the cleaning process can be enhanced by using ultrasound-assisted method.Thus,in order to determine the role of surfactants in the removal process of contaminants,the conformational change and detachment of oil contaminan ts on Al2O3 surface in SDS aqueous solution is studied.Moreover,the effects of surfactants on the conformational change and even detachment are emphatically analyzed.On this baisi,by studying the removal process of the oil contaminants affected by the cavitation bubble induced by ultrasonic physical field,the influence of cavitation on the oil detachment is revealed from molecular scale.The workpiece surface obtained by various kinds of processing methods is are defect-free.There're large amount of surface defects,which certainly have large influence on the adsorption and removal of contaminants on the workpiece surface.To reveal the effects of surface defect,the defective alumia surface was constructed by introducing surface defects on perfect alumina surface.Futher,by studing the microscopic removal process of oil contamiannts from defective alumina surface,the possible effects of surface defects on the adsorption conformational change and detachment are analyzed.The simulation results indicate that surface defect,to some extent,could promote the detachment of oil contaminants from alumina surface.But these surface defects could also induce the residual of contaminants,which hinders the thorough removal of contamiants on alumina surface.In order to meet the requirements of ICF device for the performance of metal mechanical parts,the ultra-clean manufacturing process of metal mechanical parts should be established.Based on the present study,the adsorption behavior and removal mechanims of typical contaminants on processsed surface of a luminum alloy are investigated,which are helpful to enrich and impove the basic theory on the removal of contaminants.Meanwhile,all of these present findings could provide theoretical guidance for the development of new cleaning method and improvement of the cleaning process of metal parts,which could provide foundations for the establishement of ultra-clean manufacturing process of metal mechanical parts. |
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