Investigation On Preparation And Stability Of Electroplated Enhancedcopper Nanowire Flexible Electrode

Traditional Indium tin oxide(ITO)transparent electrode is difficult to be applied in flexible wearable electronic products due to its high cost and high brittleness.Therefore,it is urgent to search for a new alternative material.Copper nanowires have attracted much attention due to their low cost and excellent electrical conductivity.However,copper nanowires are easily oxidized,making them less conductive.In order to promote the large-scale application of flexible copper nanowire electrodes,it is urgent to develop an efficient and convenient method to improve the electrical conductivity and protect it.This paper mainly studied the preparation of a nickel protective layer on the surface of copper nanowire flexible electrode by fast and convenient electroplating method to obtain high performance flexible electrode.The nickel protection layer can effectively improve the joint strength and electrical conductivity,and greatly improve the mechanical stability,chemical stability,thermal stability and long-term storage stability of the electrode.Finally,the electroplated enhanced copper nanowire flexible electrode with excellent performance was successfully applied to flexible electric heater parts,and the stable electric heating performance was obtained.High quality copper nanowires were prepared by hydrothermal method.The effects of octadecylamine content and glucose content on the morphology of the reaction products were studied systematically.During the growth of copper nanowires,copper ions are reduced to copper atoms by glucose,which selectively binds to the crystal surface of{100}to induce the formation of one-dimensional nanostructures.During the synthesis process of copper nanowires,too little ODA will lead to insufficient coating effect and the appearance of tadpole-like structure.When the content is too high,the coating effect will be too strong and a large number of particles will appear.Too little glucose leads to insufficient reduction,and too much glucose ACTS as a surfactant,preventing expansion in the one-dimensional direction.Subsequently,the separation of copper nanowires and copper nanoparticles was effectively realized by extraction method,and ultra-high purity copper nanowires were obtained.ODA on the surface of nanowires is difficult to remove,while ODA on the surface of nanoparticles is easier to remove.ODA is pro-hexane and hydrophobic,so ODA remaining on the surface of nanowires will drag the nanowires into n-hexane to achieve separation.Due to the large number of organic matter in surface layer and the oxide layer,untreated copper nanowires flexible electrode sheet resistance level in 10~5,almost is not conductive,the use of rapid acid treatment can quickly remove organic layer and the oxide layer on the surface of the nanowires,the contact between bare copper nanowires,side resistance exponential scale to drop,to meet the needs of subsequent electroplating process.After a thin layer of nickel is electroplated on the surface of the electrode after acid treatment,a solid welding joint is formed between the nanowires,and the conductivity of the electrode is greatly improved.Transmission electron microscope(TEM)was used to observe that the nickel coating grew along the(111)crystal plane of the copper nanowires,and the(011)crystal plane spacing of the nickel was almost completely matched with that of the(111)crystal plane spacing of the copper.The mechanical stability of the electrode before and after electroplating was tested by cyclic bending test and tape stripping test respectively.The cyclic bending test shows that the electroplated electrode has higher stability,and the resistance is only 1.03 times of the original value after 2000 cycles.It was observed that the electrode remained stable after 20 times of stripping after electroplating.The hydrogen peroxide solution with a mass fraction of 15%was added to the surface of the electrode before and after electroplating treatment.It was found that the electrode without electroplating treatment would fail after 70 s,while the electrode after electroplating treatment would remain stable after 450 s,but the PET substrate would be damaged.The thermal stability of the nanowires before and after electroplating was tested by heating the nanowires at 400?for 30 min.It can be observed that the copper nanowires have been broken,while the nanowires after nickel plating still maintain their morphology.The non-electroplated nanowires lose their electrical conductivity after being stored for 12 hours,while the electroplated electrodes remain stable after being stored for one week.Finally,the flexible electrode of copper nanowire is successfully applied to the flexible electric heater.After electroplating,the electrode has a more uniform temperature distribution.When the input voltage is 10 V,it can be heated to 120?,and the electrode can remain stable after continuous power supply of 20000 s.