石墨烯–金刚石/铜复合材料的电化学腐蚀性能研究

Electrochemical Corrosion Properties of Graphene-diamond/Copper Composites

目的通过引入石墨烯和纳米金刚石,提高铜基体的硬度和抗腐蚀性能。方法通过球磨、原位生长复合的方法,向铜粉上均匀引入纳米金刚石和石墨烯,并采用放电等离子烧结(SPS)制备石墨烯–金刚石混杂强化铜基复合材料(Gr@Dia/Cu)。利用扫描电子显微镜(SEM)、硬度计、电化学工作站对材料的微观组织形貌、显微硬度、电化学腐蚀性能进行测试和表征。此外,还利用X射线光电子能谱(XPS)对腐蚀产物进行分析,并讨论Gr@Dia/Cu的腐蚀机理。结果微观组织分析表明,石墨烯和纳米金刚石可以均匀地分散于铜基体中。Gr@Dia/Cu的硬度达到了97.49HV,相较于纯Cu,Gr@Dia/Cu的硬度提高了55.2%。在3.5wt%的NaCl溶液中,Gr@Dia/Cu表现出较好的抗腐蚀性能,其腐蚀电压为98 mV(纯Cu为121 mV),Gr@Dia/Cu的腐蚀电流为3.082×10^(–7)A/cm^(2)(纯铜为7.293×10–7A/cm^(2)),腐蚀速率低至0.0723 mm/a,抗腐蚀效率提高了57.74%。Gr@Dia/Cu的腐蚀产物中含有Cu2O、Cu(OH)2和CuO,与其他样品相比,Gr@Dia/Cu的腐蚀产物中CuO的相对含量(22.03%)明显较高。结论原位生长的石墨烯由于自身良好的抗渗透性和化学惰性,可以大大提高铜基体的抗腐蚀性能,并且石墨烯可以在腐蚀过程中诱导产生致密的CuO钝化层,进一步提高材料的抗腐蚀性能。

Corrosion will cause the performance of metal materials to fail.Therefore,it has always been an unsolved problem to prevent corrosion and enhance the corrosion resistance of metal materials.In this work,the electrochemical corrosion properties of copper matrix composites reinforced with graphene and diamond as reinforcing phases were investigated.The copper powder and nano-diamond were mixed in an ethanol solution at a mass ratio of 0.3 wt.%and put into a ball mill tank to mix the two evenly with a planetary ball mill.The diameters of the stainless steel balls used in the ball mill were 5 mm,10 mm and 15 mm,and the mass ratio was 5∶3∶2.The mass ratio of grinding ball to raw material was 15∶1.The model of the ball mill was QM-3SP4(Nanjing Nanda),and the rotational speed was set to 140 rpm.After ball milling for 2 hour,the composite powder was taken out from the tank,and it was naturally dried after suction filtration to obtain the Dia/Cu flake composite powder.The Dia/Cu composite powder obtained above was mixed with naphthol(0.1 wt.%)in an ethanol solution,and the mixed solution was subject to ultrasonic and stirring treatment for 20 min.The mixed solution was then subject to rotary evaporation to remove ethanol to obtain dry naphthol-coated Dia/Cu composite powder.Subsequently,the above carbon source-coated Dia/Cu composite powder was put into a tube furnace for carbonization at 800℃for 10 min,and the protective gas was mixed H2(17%)/Ar.Finally,three powders of Gr@Dia/Cu,Dia/Cu and pure Cu were densified and sintered by spark plasma sintering equipment LABOX-650(Sinter Land,Japan).The sintering temperature was 700℃,the sintering time was 5 min,the sintering pressure was 40 MPa,and the sintering atmosphere was vacuum condition.The microstructure of the material was characterized by scanning electron microscope(SEM),and the scanning electron microscope used was Hitachi S4800(Japan).The elemental qualitative and semi-quantitative analysis of the surface of the corroded samples was carried out by micro-area X-ray photoelectron spectrometer and model Esca Xi+(ThermoFisher Scientific),and the X-ray light source was Al Kα=1486.6 eV.The hardness of the samples was tested by a digital micro-Vickers hardness tester(TMVS-1)with an applied load of 0.2 kg.The surface of the test sample was a polished and smooth surface.Gr@Dia/Cu,Dia/Cu and pure Cu were cold mounted with epoxy resin,and only 1 cm^(2)of the test surface was exposed,and the test surface was in the direction of SPS sintering pressure.Afterwards,electrochemical impedance spectroscopy(EIS)and dynamic potential polarization curve tests were performed.The test equipment was Shanghai Chenhua chi760e,the electrode system was a three-electrode system,the auxiliary electrode was Pt,the reference electrode was Ag/AgCl,and the electrolyte solution was 3.5wt.%NaCl solution.The EIS test range was 10-2 Hz~106 Hz.The scanning rate of Tafel polarization curve test was 0.001 V/s.Microstructure analysis indicated that graphene and diamond could be uniformly dispersed in the copper matrix,and to a certain extent,they were uniformly distributed in strips along the direction perpendicular to the pressure.The hardness of Gr@Dia/Cu reached 97.49 Hv,which was 55.2%higher than that of pure Cu.This indicated that diamond and its hybrid strengthening with graphene could significantly increase the hardness of the composites.Moreover,in 3.5 wt%NaCl solution,Gr@Dia/Cu exhibited good corrosion resistance,its corrosion voltage was 98 mV(pure Cu was 121 mV),and the corrosion current of Gr@Dia/Cu was 3.082×10^(–7)A/cm^(2)(7.293×10^(–7)A/cm^(2)for pure copper),the corrosion rate was as low as 0.0723 mm/year,and the corrosion resistance efficiency increased by 57.74%.Through XPS analysis of corrosion products,it was found that the corrosion products of Gr@Dia/Cu contained Cu2O,Cu(OH)2 and CuO.Compared with other samples,the relative content of CuO(22.03%)in the corrosion products of Gr@Dia/Cu was significantly higher.Finally,it is concluded that the in-situ-grown graphene can greatly improve the corrosion resistance of the copper matrix due to its good permeability resistance and chemical inertness,and graphene can induce a dense CuO passivation layer during the corrosion process,further improving the corrosion resistance of the material.