Investigation On Preparation And Properties Of Mn-Cu Oxide Coating For SOFC Metallic Interconnect

Solid oxide fuel cells (SOFCs) can transfer chemical energy which stored in the fuel into electrical energy directly. Interconnct is one of important part of SOFC. It not only connects the single cells in series, but also separates the fuel gas and oxidant. Metallic interconnect, especially the ferritic stainless steel, becomes the suitalble interconnect material, owing to its better electrical conductivity, thermal conductivity, thermal expansion coefficient (TEC) match with other cell components, and easy processing. However, in the SOFC cathode atmosphere, Cr outward migaration from the ferritic stainless steel makes the cathode poisonous, leading to the degradation of cell performance. (Mn,Cu)3O4 spinel coatings on stainless steel interconnect is considered to be one of the most promising solutions at present,In the present study, Mn-Cu alloy coating was deposited on SUS 430 stainless steel by DC magnetron sputtering, followed by high temperature oxidation to convert the metallic coating to (Mn,Cu)3O4 spinel oxides. The oxidation behavior of sputtered coating at 800? in air corresponding to the SOFC cathode environment was investigated. Morphologies and phase structures of the surface scale after 1 week,5 weeks and 10 weeks oxidation were characterized by means of SEM/EDS and XRD, and the electrical performance of surface scale was evaluated. Futhermore, the influence of preoxidized and non-preoxidized process for coating's high temperature oxidation behavior were investigated and discussed. The results indicated that:(1) The mass gains of the preoxidized and non-preoxidized steel with Mn-Cu coating were dramatically obvioius at the early stage, followed by a slight increase wirh increasing time. A double-layer oxide scale was developed on the surface of the coated steel, consisting of an outer layer mainly of (Mn,Cu)3O4 spinel and an inner layer of oxide rich in Cr.(2) The developed layer of (Mn,Cu)3O4 spinel of the preoxidized and non-preoxidized steel with Mn-Cu coating during the oxidation effectively prevented the outward diffusion of(3) The preoxidized process promoted the formation of a continuous and compact layer, which acted as a barrier of Fe outward diffusion. However, for the non-preoxidized steel, it occurred that Fe migrated outward, subsequently leading to Fe doping in the (Mn,Cu)3O4 spinel.(4) The area specific resistance (ASR) of the preoxidized sample was higher than that of the non-preoxidized sample, but it was stable with increasing time.