中温SOFC金属连接体材料的氧化规律和导电行为

Oxidation and electrical behaviors of metallic interconnect in IT-SOFC cathode environment

系统地研究了SUS430铁素体不锈钢在中温SOFC阴极气氛（空气）中的氧化动力学、表面氧化物特征以及表面氧化对导电行为的作用。通过750℃静态空气中的氧化实验得出氧化增重与氧化时间的动力学关系；采用“4点法”测量合金表面氧化膜的面比电阻（ASR）；利用XRD和SEM表征表面氧化物的相结构、微观形貌及成分。实验发现，氧化动力学符合抛物线规律，并呈现出多级氧化现象；所生成的表面氧化物主要为Cr2O3和MnCr2O4；表面氧化物的ASR与测量温度之间的关系满足Arrhenius方程，并且在600～700℃之间，其斜率发生改变。结合氧化过程中的阳离子扩散、氧化物形成热力学以及半导体的导电机理对多级氧化动力学机制、氧化物相形成规律以及面比导电行为进行了理论分析。在此基础上，对SUS430作为中温SOFC金属连接体材料的可能性做出了合理的评估。

In the present paper, the oxidation kinetics, surface oxide characteristics and the effect of the surface oxides on the electrical behavior of the SUS 430 ferritic stainless steel oxidized in the intermediate temperature SOFC （IT-SOFC） cathode environment （air） were systematically investigated. The kinetic relationship of oxidation was obtained by weight gain experiments at 750℃ ; the ＂4-probe＂ method was employed to determine the area specific resistance （ASR） of the surface oxides; XRD and SEM were used to characterize the phase structure, morphology and composition of the surface oxides. It has been found that the oxidation kinetics obeys the parabolic rule with multistage; the primary oxides formed are Cr2O3 and MnCr2O4 ; the ASR-oxidation time relation satisfies the Arrhenius equation with slope change in between 600 and 700℃. Cation diffusion during oxidation, thermodynamics of oxide formation and theory of semiconductor conductivity were applied to explain the phenomena observed in the experiments. The feasibility of SUS 430 as the interconnect material of IT-SOFC was reasonably evaluated.