| Due to its unique mechanical properties,electrical properties,optical properties,magnetic properties and giant magnetoresistance effect,nano multilayer films have been widely concerned by researchers at home and abroad.At present,the method of preparing multilayer film mainly has physical method,chemical method and electrochemical method.But the physical and chemical methods,which have high environmental requirements and high cost of equipment,have restricted the development of multilayer film,while the ordinary electrochemical method at present although the cost is reduced,but the process is relatively complex,frequent human intervention also affected the quality of preparation for multilayer film.As a local electrodeposition method,jet electrodeposition has the characteristics of larger limiting current density,higher deposition efficiency and fine grain size of deposited coatings and compact structure,which is very suitable for the preparation and research of multilayer films.due to local electric deposition,as long as the effective control of the relative motion of the nozzle and the workpiece,you can achieve rapid switching of the station,which provides a good condition for the autonatic preparation of multilayer films.In this paper,a method for the preparation of multilayer films by "multiple array jet electrodeposition" is presented.For preparation requirements of multilayer film on the surface of rotary parts and non rotary parts,we build a multiple rotating jet array electrodeposition system and multiple translational array jet electrodeposition system.Based on the requirements of different applications,the Cu-Ni multilayer films and Cu-Co multilayers with good structure were prepared on the substrate of stainless steel,copper,single crystal silicon and Nd-Fe-B,respectively.Through a large number of experiments,the preparation method and the strengthening mechanism of multilayer films were studied.The special interface structure of the semi-coherent interface was found between the films,which is one of the important reasons for the performance enhancement of nano-scale multilayers.Finally,based on the strengthening mechanism of multilayer film,using multiple array jet electrodeposition preparation technology of nano multilayers in offshore wind power Nd-Fe-B surface preparation of multilayer interweaving nickel,the paper discusses the application of the technology in surface corrosion protection.The main work of this paper is as follows:(1)In view of the characteristics of the jet electrodeposition method,combined with the electro deposition dynamics theory,a systematic analysis was carried out on the four steps of liquid mass transfer,pre transformation,charge transfer and new phase formation.The research shows that the high speed jet of jet electrodeposition improves liquid phase mass transfer speed and reduces the concentration polarization;furthermore,high speed jet reduces the thickness of the diffusion layer of the surface of the substrate,thereby improving the limiting current density,the charge transfer overpotential increases,therefore,jet electrodeposition can be electrodeposited on the current the density is higher than the ordinary electro deposition of dozens or even hundreds of times.At the same time,high over potential is more favorable to improve the nucleation rate and nucleation density,which is the direct cause of the fine grain size and compact microstructure.The above characteristics of jet electrodeposition provide a basic condition for the preparation of nano multilayer films with good structure.(2)Based on theoretical analysis and flow field simulation,the microstructure and thickness uniformity of the coating were analyzed by the initial experiment.The results show that the coating microstructure influenced by the experimental conditions,will produce varying degrees of pinhole,tumor defects which are reduced by friction auxiliary device added,and it also increases the uniformity of deposition coating structure;the flow field simulation and experimental analysis of narrow rectangular nozzle found that,the port will produce uneven flow field solution,thus affecting the uniformity of coating thickness,as a result,the thickness is higher than the port near the center nozzle position,which is not conducive to the preparation of the multilayer;optimizing the design of nozzle port and changing the port to half round reduce the thickness gap between the near port and the center of nozzle,which improve the uniformity of coating thickness,for the preparation of nanometer multilayer films provide a good test condition.(3)Based on the original NC jet electrodeposition machine,by adding multiple rotating array electrodeposition unit and control system,built multiple rotating jet array electro deposition system,and the Cu-Ni multilayer films were preparated on the stainless steel surface by the system.Analyse the section of the Cu-Ni multilayer film by using SEM and the multiple effects of electric rotary jet prepared multilayer deposition factors at the micro level,put forward the effective pre plating can improve the accuracy of multilayer modulation wavelength;testing on Cu-Ni multilayer film thickness,roughness and hardness characterized that the Cu-Ni multilayer coatings prepared by this system has good uniformity;by XRD and TEM analysis on the structure of multilayer films,the special interface structure of Cu-Ni multilayer was found,which showed the Cu-Ni nano multilayer films has a new type of Cu-Cu Ni-Ni structure.Through the analysis of micro hardness,wear resistance,corrosion resistance and magnetic properties of Cu-Ni multilayer films,which shows nano multilayer film strengthening effect mainly from its interface structure;the study found that Cu-Ni multilayer films exhibit various magnetic properties,this paper presents a possibility of Cu-Ni nano multilayer film as magnetic head and magnetic recording materials.(4)For preparation of multilayer films on non rotating body parts,we design and build multiple translational array jet electrodeposition system,and the system was used to prepare Cu-Co multilayer film with the copper substrate and silicon substrate.Because of the electrical properties of semiconductor silicon,the jet plating surface is not uniform or not plating.Based on electromagnetic simulation,combined with the experimental,charge mobile silicon surface were analyzed,and the conduction mode of silicon was improved,which ensure that multilayer films are prepared on silicon surface.With the analysis of the microstructure and properties of copper substrate and silicon substrate preparation of Cu-Co multilayer films,we found that the growth of Cu-Co multilayers is affected by the substrate material.The surface of silicon substrate Cu-Co multilayer film magnetoresistance change ratio is analyzed;we found that the giant magnetoresistance effect,the rate of reluctance can reach 50.38% in this paper.(5)Based on the multiple array jet electrodeposition translation system as an example,we studied the effects of current density,scanning speed,the number of parameters on the coating.For the multilayer coatings with different structure,we put forward the idea of selecting optimal test plan to guide future multilayer film preparation parameters,which provides theoretical guidance for the industrial production of multilayer film.(6)In view of the poor corrosion resistance of sintered Nd-Fe-B permanent magnetic materials in offshore wind power,we present a method for the preparation of multilayer interweaving nickel on the surface of Nd-Fe-B based on the study of the strengthening mechanism of multilayer films prepared by jet electrodeposition.The test results show that the multilayer with bright nickel & dark nickel intertwined is conducive to the performance improvement.The different layers of multilayer interweaving nickel with thickness of about 20?m were prepared on the surface of Nd-Fe-B,we found that the more the number of layers,the better performance,when the number of layers for the 230 layer,it performances a good neutral salt spray corrosion resistance,far higher than the national standard. |
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