| High quality films with fine grains were prepared by the new plating method of nano-materials,which combined the merits of traditional electroplating with supercritical carbon dioxide techniques,it could be helpful to designing novel non-traditional machining technology.This dissertation was supported by National Natural Science Foundation(50875116)and Jiangsu Province Natural Science Foundation(BK2006043),and it simulated and experimental studied about fabricating metal films of micro-electroforming process in supercritical CO2.This dissertation focused on the following aspects:(1)An optimized mathematical model was established to demonstrate the effect of pressure and temperature under supercritical conditions on the electric resistance of emulsion for electroforming.Optimal toolboxes of Matlab software and anova12 functions for variance analysis were used for numerical solving.Experiment of nickel electroforming with non-ionic surfactant in supercritical CO2 was investigated.The results indicate that based on the model and that of analysis are roughly consistent.The dispersion state of electric resistance of emulsion for electroforming was best under optimized conditions,and the microhardness of electroformed coating was increased about 30%.Working pressures had a significant effect on the resistance of emulsion,while temperatures had a little effect on it.Relevant results could be helpful to designing novel electroforming process.(2)To improve the micro electroforming quality of a microstructure,the distribution properties of the electric field and flow field in the micro-electroforming process under supercritical CO2 fluid were simulated by Matlab software.The analysis results showed that,the equipotential line curvature of electric field growed with the aspect ratio increasing,which resulted in a discrepancy of ions transferring capacity during the reaction area.The results also indicated that only stirring could not improve transferring condition of the metal deposition,while complex stirring with auxiliary ultrasonic or supercritical C02 fluid environment could improve the velocity of the metal deposition and reduce the defect of the electroforming layer to obtain the perfect microstructure.(3)Pdetool toolboxes of Matlab software were used for numerical simulating and discussing two kinds of diffusion transport process under supercritical C02.The effect of various cathode applied current density and depths on single nickel ions and multispecies ions concentration variation inside the micro-structure were discussed respectively.Numerical analysis results indicated that for an aspect ratio of 4,the diffusion transport of nickel ions was gradually approaching a steady state with the working time increasing.A small current density should be employed in high aspect ratio while a larger current density should be used for low aspect ratio electroforming.It was difficult to achieve the transport task only having diffusion transport effect on micro-electroforming.(4)The experiment of nickel electroforming with non-ionic surfactant Tergitol TMN 10 was investigated under supercritical C02.The principle,technique method,quality symbol and performance characterization of micro-electroforming were briefly introduced.The experimental priciple and schematic,technique conditions and process in supercritical CO2 were detailedly presented.The effect of current density on microstructure,Vickers hardness,current efficiency,depositing rate and thickness were mainly discussed.The experimental results indicated that the average Vickers hardness,thickness of nickel coatings were gradually increased with the current density growing,but that of current efficiency was decreasing.Compared to the conventional electroforming method,a higher uniformity and smoother surface of the nickel film was obtained by supercritical CO2 fluid at 10MPa and 323K,the microhardness,current efficiency,depositing rate and thickness of nickel films were 701.2HV,94.51%,51.85mg/(cm2·h)and 39?m with the current density of 5 A/dm. |
PDF Full Text Request