大气等离子喷涂及固相反应法制备MnCoCu金属连接体防护涂层OACSTPCD

Mn-Co spinel coating can effectively protect metallic interconnects of solid oxide fuel cells(SOFC)from oxidation at elevated temperature and thus can restrain the performance degradation of cells.But currently the cost of spinel is high,the electrical performance and stability need to be improved.In this paper,highly conductive spinel coatings were prepared from metallic powder through atmospheric plasma spraying(APS)and solid phase reaction.Cu-Mn spinel,a highly conductive phase,was introduced into the spinel coating by Cu-doping.The effect of Cu addition and doping condition on the properties of spinel coatings was studied according to phase composition,morphology,element distribution and conductivity.The results showed that coatings were obviously densified and homogenized after being heated at 800℃.The main phase of the obtained coatings was identified as CuxMn3-xO4(x=1,1.2,1.4)and MnCo2O4 according to the X-ray diffraction(XRD)analysis.For sample with 6wt.%Cu and 9wt.%Cu,CuO,Mn2O3 were also in the coating samples containing 6wt.%Cu and 9wt.%Cu content.A region with rich Cr was observed between the substrate and the spinel coating.Sintering at controlled temperature with H2 protection(a reduction process)could significantly improve the density of coatings.The conductance of samples was characterized according to the areal specific conductivity and the conductivity.The areal specific conductivity was obtained by an ohmmeter,including both the contribution of the metallic substrate,the coating and the Cr-enriched region between them.The sample with 12wt.%Cu exhibited the highest areal specific conductivity with value of 24.84 S/cm2 after oxidation for 10 h at 800℃.For all samples,being oxidized for a period more than 100 h,the measured areal specific conductivity decreased,but sample with 12wt.%Cu still presented the highest conductivity.Moreover,after a reduction process,the areal specific conductivity of the obtained samples was significantly lower than that of samples without reduction process.It was thought that an intensive diffusion of Cr happened during the reduction process which turned to low-conductive phases during the oxidation step.The conductivity of coatings was obtained via a four-probe method.It was found that the conductivity of oxidized coatings increased with the addition of Cu and the test temperature.At 800℃,the conductivity of the sample with 12wt.%Cu was as high as 93.15 S/cm,but when a reduction process was introduced before the oxidization,its conductivity decreased to 35 S/cm due to the intensive diffusion of Cr happened during the reduction,which introduced the Cr-enriched region and low conductive phases to the coating.In addition,the conductivity of coatings was found higher after a long-time sintering.Therefore,it can be concluded that highly conductive spinel coatings can be obtained by sintering the metallic coatings prepared by APS.The phase composition of obtained spinel coatings can be easily regulated by adjusting the composition of metallic powder.The addition of Cu can effectively improve the electrical conductivity of spinel coatings.The reduced coatings were significantly densified,but will lead a decrease both of areal specific conductivity and the coating conductivity.