Preparation And Failure Behavior Of Multifunctional Graphite Based Coating

With the development of modern science and technology,electronic components show the development trend of miniaturization,which puts forward higher requirements for the conductivity,thermal conductivity and anti-corrosion performance of materials.Based on this,a multifunctional coating with electrical,thermal and anti-corrosion properties was developed in this subject.The properties of the coating were characterized,and the failure process of the coating system was analyzed.The main conclusions are as follows:（1）Graphite/polyurethane coatings were prepared with graphite as conductive filler,and the effect of graphite addition on the properties of the coatings was studied.The results showed that with the increase of graphite content,the square resistance of the coating decreased and the thermal conductivity increased,but the salt spray resistance became worse.When the amount of graphite was 45%,the square resistance of the coating was 542Ω/□,the thermal conductivity was 2.3026W·m^-1·K^-1,and the salt spray resistance time could reach 480h.（2）Zinc was coated on the surface of graphite by electroless plating,which improved the conductivity of graphite filler.The results showed that the optimum process parameters of electroless plating were 60g/L zinc chloride and2g/L sodium borohydride,and the electroless plating time was 3h.The resistivity of the zinc-coated graphite filler prepared by this process was only0.0022Ω·cm,which was about 98%lower than that of graphite.（3）The zinc-coated graphite powder was treated with a corrosion inhibitor,and a conductive coating was prepared.The results showed that the addition of corrosion inhibitor slightly reduced the electrical conductivity and thermal conductivity of the coating,but the salt spray resistance was significantly improved.Compared with the 45%graphite/polyurethane coating,the square resistance of zinc coated graphite coating（Zn/C-16#coating）treated with corrosion inhibitor was reduced by about 49%,the thermal conductivity was reduced by 13.05%,and the salt spray resistance time was shortened from 480h to 240h.（4）Multifunctional composite coatings were constructed by mixing graphite with polyaniline and silver-coated copper powder as conductive fillers,respectively,and the effects of different fillers on the properties of the coatings were studied.Compared with the C-45 coating,the square resistance of the two composite coatings decreased by 30.26%and 75.65%,respectively,the thermal conductivity decreased by about 40%,and the salt spray resistance time was shortened from 480h to 48h and 240h,respectively.It showed that the coating prepared by the composite of graphite and silver-coated copper（（Ag/Cu）/C composite coating）had better performance.（5）The electrochemical behaviors of multifunctional coatings and aluminum alloy substrates were analyzed by electrochemical methods,and the corrosion failure process of the coating system was deeply studied.The results showed that compared with C-45 coating,the potential difference between Zn/C-16#coating and（Ag/Cu）/C composite coating and aluminum alloy decreased by 36.77%and 32.67%respectively,indicating that the tendency of galvanic corrosion was reduced.The electrochemical test results further showed that the characteristics of electrochemical impedance spectroscopy changed significantly during the corrosion failure of the coating system.The microporous resistance and interfacial charge transfer resistance of the coating both increased first and then decreased,so the anticorrosion performance of the coating system increased first and then decreased.