Research On Fabrication Technology And Mechanical Durability Of “Interconnect Topology”-based Superhydrophobic Surface On Aluminum Substrate By Femtosecond Laser

Owing to their unique properties,superhydrophobic surfaces possess great advantages for various potential applications including enhanced heat transfer,fluid drag reduction and enhanced corrosion resistance.Meanwhile,they are also widely used in aerospace,national defense & military industry,energy power,and other fields due to their superb properties and enhanced performance.Furthermore,the current superhydrophobic surfaces exhibit a number of disadvantages such as poor mechanical durability,environmental pollution during the preparation process,poor control over the wetting and so on.Therefore,the structure design and technology of the interconnect topology functional surface(ITS)with better mechanical durability and superhydrophobicity characteristics have been studied in this thesis.In addition,a low-cost,non-polluting,high efficiency,and quantitatively controlled method for preparing superhydrophobic surfaces,which is called temperature-controlled aging treatment(TCAT),is proposed.Subsequently,the mechanical durability of that is enhanced by comprehensive control and optimization of structural dimension features based on realizing the enhance of superhydrophobic property of interconnect topology structured surface,which has important research significance.1Different from the traditional structure design of superhydrophobic surfaces,we propose a novel designing scheme based on the theory of finite element static analysis and the wettability contact models,a comprehensive theoretical framework was developed in order to take into account the mechanical durability and the wettability of the superhydrophobic surfaces.From our analysis,it is apparent that the interconnect topology structure(ITS)exhibits best mechanical durability and superhydrophobicity characteristics compared with the other four typical compounds.Specifically,the maximum equivalent stress and maximum equivalent strain of interconnect topology structured surface are the smallest compared with the other typical structured surfaces under the same external excitation.When the geometric feature size of the structures are fixed,ITS can theoretically achieve the superhydrophobic state with a static contact angle greater than 174.151° with the increase of the energy coefficient of the solid-liquid interface,and the other structured surfaces can only achieve superhydrophobic state of 168°~170°.Meanwhile,the critical value of static contact angle for ITS(~175.810°)is much larger than that of other typical superhydrophobic surfaces(171.778° ~172.740°)in terms of achieving superhydrophobic property by controlling the three-phase wetting state.The structures were fabricated by employing a femtosecond laser technique on substrate surfaces.The interconnect topology structure(ITS)was processed successfully by velocity gradient enhancement compound with low frequency secondary modification,and the other four typical compounds were fabricated based on "depth barrier" effect.In addition,ITS is a complex micro-nano unit composed of alternating arrays with holes and bumps while the other configurations are single micro-nano units with protruding-like monomer shapes.Subsequently,a low-cost,non-polluting,high efficiency,and quantitatively controlled method for preparing superhydrophobic surfaces by control the temperature and treatment time,which is called temperature-controlled aging treatment(TCAT),is proposed.As a result,All the above-mentioned structures achieved the wettability transition from superhydrophilic /hydrophilic surfaces during femtosecond laser ablation to superhydrophobic surfaces after imposing the TCAT step(150 ℃,3~6 h).This phenomenon indicates the high efficiency of the TCAT technique in fabricating robust superhydrophobic surfaces,which is over 720 times bigger than that of the natural aging treatment.At the same time,interconnect topology structure exhibited the largest contact angle of 172.744° among these samples and all of them could retain the contact angle of about 170° after 24-hour-TCAT.All the surfaces under consideration still maintained the superhydrophobic properties after the elapse of 200 days of static storage in the air and water shock(~100 KPa)for 30 minutes whereas the contact angle of interconnect topology structure was over 171° and the other four typical compounds were lower than 170°,which indicates ITS has the better superhydrophobicity stability.To further improve and optimize the double-effect performance of interconnect topology superhydrophobic surfaces,especially the mechanical durability,a comprehensive theoretical framework of the finite element statics simulation and wetting contact theory optimization model under the change of dimensional characteristics were developed.Afterwards,the dimensional characteristics of the ITS were enhanced from the perspective of structural morphology optimization by a coupled optimization of "Functional Structure Array Period" modulation and "Depth-stacking" effect.It is found that the preparation of superhydrophobic surfaces with contact angles about 170.000°±1.750° can be achieved at 150°C-2.5 htemperature-controlled aging treatment under the comprehensive preparation strategy based on power-velocity coupling modulation and the increase of the periodic characteristics of functional structure,which the efficiency is increased by 500%.At the same time,the mechanical durability was also improved,including the wear resistance and friction resistance.More specifically,compared with traditional fluorination modification and original ITS superhydrophobic surface,the wear rate is reduced by 40.03% and 29.79%,and the time that wear to bare substrate is increased by 93.7% and 37.10%.Finally,the dual-effect performance optimization of superhydrophobicity and mechanical durability for ITS is realized.