OXIDATION KINETICS BEHAVIOR AND ELECTRICAL PROPERTY OF MnCO2O4 SPINEL AS A COATING MATERIAL FOR METALLIC INTERCONNECTS
Wenying ZHANG1(),Jun LI2,Bo ZHOU1
1 School of Mechanical Engineering and Electronic Information, China University of Geosciences, Wuhan 430074, China
2 State Key Laboratory of Materials Processing and Die&Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Cite this article:
Wenying ZHANG, Jun LI, Bo ZHOU. OXIDATION KINETICS BEHAVIOR AND ELECTRICAL PROPERTY OF MnCO2O4 SPINEL AS A COATING MATERIAL FOR METALLIC INTERCONNECTS. Acta Metall Sin, 2016, 52(3): 355-360.
MnCo2O4 spinel was coated on the surface of SUS 430 alloy by using the sol-gel method. The oxidation kinetics behavior and electrical property of coated SUS 430 alloy in solid oxide fuel cells (SOFCs) cathode atmosphere were investigated. XRD, EDS and SEM were used to characterize the phase structure, surface and cross-section morphology, and composition of the surface oxides; the area specific resistance (ASR) of the surface oxides was measured by using the four-probe direct current technique. The result shows that a 2 μm thick oxide scale, mainly consisting of an inner layer of Mn-Cr spinel and an outer layer of doped Mn-Co spinel, was formed during cyclic oxidation at 750 ℃ in air for 1000 h. The growth of Cr2O3 and Fe2O3 was depressed. The oxidation kinetics obeys the parabolic law with two rate constants 3.74×10-15 g2/(cm4s)(0~200 h) and 7.06×10-15 g2/(cm4s) (200~1000 h), respectively, which is 1 order of magnitude lower than that of the SUS 430 alloy without coating. The ASR is in the range of 5.21~22.65 mΩcm2 at 600~800 ℃. MnCo2O4 coating was proved to be effective in enhancing the oxidation resistance and electrical property of SUS 430 alloy.
Table 1 EDS analysis results corresponding to points A, B and area C in Fig.2 (mass fraction / %)
Fig.1 XRD spectra of MnCo2O4 coating on SUS 430 alloy before and after oxidation at 750 ℃ in air for 1000 h
Fig.2 Surface morphologies of MnCo2O4 coating before (a) and after (b) oxidation at 750 ℃ in air for 1000 h
Fig.3 Cross-sectional morphology (a) and EDS analysis along the line in Fig.3a (b) of MnCo2O4 coating after oxidation at 750 ℃ in air for 1000 h
Fig.4 Square of oxidation mass gain of SUS 430 alloy with and without MnCo2O4 coating as a function of oxidation time at 750 ℃ in air (Kp1 and Kp2 correspond to oxidation rate constants at 0~200 h and 200~1000 h, respectively)
Fig.5 Area specific resistance (ASR) of MnCo2O4 coating as a function of measurement temperature (T) after oxidation at 750 ℃ in air
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