Electrophoretic Deposition of Advanced Ceramic Coatings for High Temperature Corrosion Protection of Steel Interconnects for Solid Oxide Cells

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Microstructural, thermo-mechanical and corrosion properties of electrophoretically co-deposited Cu and Fe doped Mn–Co spinel coatings for solid oxide cell interconnects

Chromia forming ferritic stainless steels are employed as interconnects in SOC stacks; the deposition of a manganese cobalt spinel protective coating is widely accepted as a viable solution to mitigate both the oxidation and the chromium evaporation. Electrophoretic deposition (EPD) offers the possibility to deposit homogeneous coatings in few seconds and at room conditions and the need of a simple and adaptable apparatus, thus reducing processing time and cost. A successful deposition is ensured by the optimization of both the starting suspensions in terms of colloidal properties and the post-deposition sintering profile. Electrophoretic co-deposition is an innovative approach for the simultaneous deposition of spinel precursors and for designing in-situ modified manganese-cobalt spinel coatings. A systematic microstructural, thermo-mechanical and electrical characterization of simultaneous Fe–Cu doped Mn–Co spinel coatings processed by electrophoretic co-deposition on Crofer22APU is here reported and discussed. We demonstrate the feasibility to co-deposit Fe2O3, CuO and Mn–Co spinel to produce dense, stable and effective doped spinel coatings. Improved functional properties of produced coatings are assessed in terms of microstructure development, oxidation kinetics and area specific resistance at SOC stack relevant conditions. Furthermore, an assessment of the dilatometric properties of the Fe–Cu doped spinels reveals the influence of different doping levels on the thermomechanical compatibility of the Fe–Cu doped Mn–Co spinel coatings with the interconnect. This work proposes the electrophoretic co-deposition method as an innovative approach for the simultaneous deposition of spinel precursors and for designing in-situ modified coatings

Fe-modified Mn2CuO4 spinel oxides: coatings based on abundant elements for solid oxide cell interconnects

The current state of the art steel interconnect coating materials are based on critical raw material - Co-oxide spinels. Replacing Co-oxide spinels with alternative, abundant materials can reduce the dependence on the critical raw materials. Cobalt-free coatings with the general formula Mn2-xCuFexO4, where x = 0, 0.1, 0.3, were electrophoretically deposited on a ferritic stainless-steel support and evaluated. Prior to deposition, the powders were prepared by a soft chemistry process and studied in terms of crystallographic phase analysis, electrical conductivity, thermal expansion, and sinterability behaviour. Coated steel samples were oxidised in an air atmosphere at 750 \ub0C for 3000 h. In parallel, a state-of-the-art MnCo2O4 spinel oxide was tested as a reference. The coatings and oxide scale microstructures of the surfaces and cross-sections were examined by XRD, and SEM-EDX. TEM-EDX, XRF, and micro-XRD were also performed on the cross-section lamellae. The electrical properties of the steel-coating system were evaluated by Area Specific Resistance measurement. The results confirm that Mn–Cu–Fe oxides exhibit higher conductivity and lower TEC than Mn–Co oxide. Based on the obtained results, it might be concluded that the proposed coatings are a promising alternative to coatings that contain cobalt

Manganese–Cobalt Based Spinel Coatings Processed by Electrophoretic Deposition Method: The Influence of Sintering on Degradation Issues of Solid Oxide Cell Oxygen Electrodes at 750 °C

This paper seeks to examine how the Mn–Co spinel interconnect coating microstructure can influence Cr contamination in an oxygen electrode of intermediate temperature solid oxide cells, at an operating temperature of 750 °C. A Mn–Co spinel coating is processed on Crofer 22 APU substrates by electrophoretic deposition, and subsequently sintered, following both the one-step and two-step sintering, in order to obtain significantly different densification levels. The electrochemical characterization is performed on anode-supported cells with an LSCF cathode. The cells were aged prior to the electrochemical characterization in contact with the spinel-coated Crofer 22 APU at 750 °C for 250 h. Current–voltage and impedance spectra of the cells were measured after the exposure with the interconnect. Post-mortem analysis of the interconnect and the cell was carried out, in order to assess the Cr retention capability of coatings with different microstructures

Addition of dimethyl phosphite to <i>N,N'</i>-dialkyl- and -diaryl terephthalaldimines and its stereochemistry contrary to behavior of other analogues

<p>The addition of dimethyl phosphite to <i>N,N</i>'-terephthalylidene-alkyl- (or aryl-) amines resulted in new tetramethyl 1,4-phenylene-bis-(<i>N</i>-alkylaminomethyl)-phosphonates in moderate yields. The stereochemical behavior of these reactions was studied by NMR, demonstrating that the reactions lead to the formation of both possible diastereomeric forms from 1:1 to 1:2 ratios. This was unexpected considering that previously investigated additions of diethyl, dibenzyl, and diphenyl phosphites to terephthalaldimines were diastereoselective up to 100%. Attempts were made to find reasonable explanation for the phenomenon using semi-empirical and DFT calculations.</p