Interface stability between bare, Mn-Co spinel coated AISI 441 stainless steel and a diopside-based glass-ceramic sealant

This document is the Accepted Manuscript version of the following article: A. G. Sabato, A. Crysanthou, M. Salvo, G. Tempura, and F. Smeacetto, ‘Interface stability between bare, Mn-Co spinel coated AISA 441 stainless steel and a diopside-based glass-ceramic sealant’, International Journal of Hydrogen Energy, Vol. 43 (13): 1824-1834, January 2018, made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License CC BY NC-ND 4.0 ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way. Under embargo until 16 December 2018. The final, definitive version of this paper is available online at doi: https://doi.org/10.1016/j.ijhydene.2017.11.150.This study is focused on a diopside-based glass-ceramic sealant for solid oxide fuel cells and its compatibility with AISI 441 stainless steel interconnect. The morphological and chemical stability with both bare and Mn–Co spinel coated AISI 441 steel, after 3500 h exposure at 800 °C in air, is reviewed and discussed. Post-mortem samples are morphologically and chemically analysed by SEM-EDS. Reaction products at the glass-ceramic/bare AISI 441 interface, resulting from the reaction of Mg from the sealant and Cr and Mn from the steel, are detected, without affecting negatively the integrity of the joints. In the case of Mn–Co spinel coated AISI 441, interactions between the glass-ceramic and the outer part of the Mn–Co spinel coating, along with crystallization of oxides rich in Si and Mg, are detected, but still no corrosion phenomena are present. The glass-ceramic is found to be compatible with both bare and coated AISI 441.Peer reviewe

Oxidation protective glass coating for magnesium silicide based thermoelectrics

A Mg2Si-Mg2Sn based thermoelectric material (TE), with composition of Mg2Si0.487Sn0.5Sb0.013, produced by ball-milling combined with spark plasma sintering, is successfully coated with a new silica-based glass, which is specifically designed, characterised and tested as an oxidation protective coating for mid-temperature range (up to 500 °C) applications. Despite the relatively high coefficient of thermal expansion (CTE) of Mg2(Si,Sn) based materials, very good thermo-mechanical compatibility between the substrate and the coating material is obtained. Oxidation tests, performed at 500 °C for 120 hrs in air, demonstrate the effectiveness of the glass coating for the protection of Sb doped Mg2(Si,Sn) thermoelectric materials

Analysis of Lanthanum and Cobalt Leaching Aimed at Effective Recycling Strategies of Solid Oxide Cells

Lanthanum and cobalt are Critical Raw Materials and components of Solid Oxide Cells— SOCs electrodes. This review analyses lanthanum and cobalt leaching from waste materials (e-waste, batteries, spent catalysts), aiming to provide a starting point for SOC recycling, not yet investigated. The literature was surveyed with a specific interest for leaching, the first phase of hydrometallurgy recycling. Most references (86%) were published after 2012, with an interest higher (85%) for cobalt. Inorganic acids were the prevailing (>80%) leaching agents, particularly for lanthanum, while leaching processes using organic acids mostly involved cobalt. The experimental conditions adopted more diluted organic acids (median 0.55Mfor lanthanum and 1.4Mfor cobalt) compared to inorganic acids (median value 2 M for both metals). Organic acids required a higher solid to liquid ratio (200 g/L), compared to inorganic ones (100 g/L) to solubilize lanthanum, while the opposite happened for cobalt (20 vs. 50 g/L). The process temperature didn’t change considerably with the solvent (45–75  C for lanthanum, and 75–88  C for cobalt). The contact time was higher for lanthanum than for cobalt (median 3–4 h vs. 75–85 min). Specific recycling processes are crucial to support SOCs value chain in Europe, and this review can help define the existing challenges and future perspectives

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

Electrophoretic Deposition of Ceramic Coatings for Solid Oxide Cells: Challenges and Perspectives

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Shear Strength Tests of a Glass-Ceramic Sealant for Solid Oxide Fuel Cells Applications

Different approaches are used for the integration of ceramic components in solid oxide fuel cells stacks, where dissimilar materials (ceramics and metals) have to be joined and coupled for a reliable long term operation. This work focuses on the mechanical characterisation of a glass ceramic sealant used for the joining of Crofer22APU metallic interconnect samples as well as the interaction with a preoxidised Crofer22APU. Crofer22APU–glass ceramic sealant joined samples are tested by two different mechanical tests. Hourglass samples with different geometries were tested using an in-house developed torsion test machine at room temperature. In addition, their mechanical strength was also evaluated according to the ISO 13124 standard. The comparison of the two different testing methods, with particular focus on the shear strength of the joined samples, are reviewed and discussed

Electrical characterization of glass-ceramic sealant-metallic interconnect joined samples under solid oxide electrolysis cell conditions; influence on the microstructure and composition at the different polarized interfaces

In this study, the electrical resistivity of a glass-ceramic sealant is evaluated at 850 ◦C, for 2800 h under the applied voltage of 1.6 V. The glass-ceramic sealant is sandwiched between two Crofer22APU plates to produce Crofer22APU/Glass-ceramic/Crofer22APU samples. The Crofer22APU/glass-ceramic/Crofer22APU joints show electrical resistivity around 106-107 Ω cm, significantly high to ensure the insulation between two conductive interconnect plates. The detailed SEM-EDS post mortem analysis showed good thermo-mechanical compatibility of the glass-ceramic with the Crofer22APU substrates, thus excluding any detrimental interaction with the metallic interconnect under high applied voltage. XRD analysis of glass-ceramic confirmed the presence of crystalline phases with suitable CTEs, after electrical resistivity under harsh conditions

Design and characterization of novel glass‐ceramic sealants for solid oxide electrolysis cell (SOEC) applications

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