Thermal Growth Cu1.2Mn1.8O4 Spinel Coatings on Metal Interconnects for Solid Oxide Fuel Cell Applications

Abstract

A novel cobalt-free Cu 1.2 Mn 1.8 O 4 spinel coating is prepared and evaluated for the metal interconnect of solid oxide fuel cell. Mn-35Cu and Co-35Mn alloy coatings are deposited on 430 SS substrate and then in-situ oxidized in air at 750 • C for 100 h. XRD results confirm that Cu 1.2 Mn 1.8 O 4 spinel with some Mn 2 O 3 is formed, and the average thickness of the coating is 70-80 µm according to cross section image. Spinel oxide coating is compact and has good adherence to the substrate, and very low Cr and Fe contents are detected in the coating. A small area specific resistance of 8.7 mΩ cm 2 is achieved at 800 • C for the composited Cu 1.2 Mn 1.8 O 4 spinel coating, which is much less than that of the composited (Co,Mn) 3 O 4 spinel coating. The research indicates that the Cu 1.2 Mn 1.8 O 4 coating evolved by the high-energy micro-arc alloying process is a promising coating material for the metallic interconnects.

Oxidation Characteristics and Electrical Properties of Doped Mn-Co Spinel Reaction Layer for Solid Oxide Fuel Cell Metal Interconnects

“…Some granular appearance in Figure 2b2 is also seen on the surface and EDS in Table 1 shows that element compositions are the same as Figure 2b1. It is hypothesized that the granular Co3O4 found in local area is due to active element Lanthanum enrichment, which is found in Co-38Mn-2Dy coating but not for Co-40Mn coating [25]. When coating oxidized for 100 h, fine pores and needle-like morphology in Figure 2c1 are visible and uniformly distributed in Co3O4 scales.…”

“…In previous study [3,8,25], the results disclose that ambient dissociation pressure of oxygen at high temperature will favor the formation of some specific oxides. When coating oxidized in air, partial pressure of oxygen gradually decreases from gas/scale interface to oxide/alloy interface; therefore, a thin Co 3 O 4 layer forms at high oxygen partial pressure and is usually found on the top oxide layer (Figures 4a 1 and 6).…”

“…Figure 2 shows X-ray diffraction and surface morphology of coatings oxidized at 750 °C for 20 h and 100 h. Before oxidation, Co-38Mn-2La alloy coating in Figure 2a is mainly a cubic Co structure and peaks shift toward low angles by referring to pure Co When coating oxidized at 750 °C in air for 20 h, the outmost scales in Figure 2b combined with EDS analysis consist of Co3O4 and small amount of (Co,Mn)3O4, which is an intermediate tetragonal spinel structure between MnCo2O4 (cubic) and Mn3O4 (tetragonal). The previous study [25] discloses that Co3O4 prefer to form under high oxygen partial pressure and only a thin layer is found on the top oxide layer. When Co-38Mn-2La coating oxidized for 100 h, diffraction peak of tetragonal (Co,Mn)3O4 spinel is intensified in Figure 2c, due to Mn outer-diffusion with the extended time.…”

“…However, the adherence to substrate for spinel coatings is still a problem. HEMAA process [25] produces the metallurgically bonded alloy coatings and forms spinel coatings via in situ oxidation.…”

Investigation on the High-Temperature Oxidation Resistance of Ni-(3~10) Ta and Ni-(3~10) Y Alloys

“…These alloys are used extensively for high-temperature industrial applications, such as aerospace systems, gas turbine blades, and interconnects of solid oxide fuel cell (SOFC) [1][2][3]. In these applications, with the working temperature of SOFC decreasing to an intermediate temperature (600-800 • C), metallic materials (Fe-based, Ni-based, and Cr-based alloys) as interconnects become feasible [4][5][6]. However, Cr in Ni-based alloys can result in Cr volatilization and deposition on the cathode, which can significantly degrade SOFC performance [7,8].…”