Corrosion behaviour of nitrided ferritic stainless steels for use in solid oxide fuel cell devices

Plasma nitriding was applied to ferritic stainless steel substrates to improve their performances as interconnects for solid oxide fuel cell devices. The samples underwent electrical conductivity test and SEM/EDS, TEM/EDS, environmental-SEM analyses. The first stages of corrosion were recorded in-situ with the e-SEM. Nitriding is effective in limiting the undesired chromium evaporation from the steel substrates and accelerates the corrosion kinetics, but its influence of the electrical conductivity is ambiguous. No intergranular corrosion is found in the steel substrate after long time operation. Nitriding helps commercially competitive porous coating to improve chromium retention properties of metal interconnects

Development of a novel electroless deposited nickel braze for micro-tubular solid oxide fuel cell current collector contacting

© 2021 The Authors. Published by Elsevier. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1016/j.jajp.2021.100070A brazing process for the fuel electrode (anode) contacting of a micro-tubular fuel cell is reported. The low-cost, novel, electroless deposited braze suitable for mass production was optimised with respect to material loading and brazing environment. Durable current collector-anode joints were obtained while protecting sensitive solid oxide fuel cell components. It was determined that a minimum braze loading of 20 µm thickness was required to join the current collector at multiple contacts along the interior tube wall. The final brazed current collector design achieved a high peak power density of 0.14 W.cm−2 at 750°C, 2.35 times higher than for the un-brazed design.This research was funded by the EPSRC, grant number EP/L015749/1), through the CDT in Fuel Cells and their Fuels, led by the University of Birmingham.Accepted versio

Considering the suitability of symmetrical cell testing in developing electrodes for solid oxide fuel cells via a study of different lanthanum nickelate cathode materials

Developing solid oxide fuel cells (SOFCs) with improved performance and lifetime continues to attract research attention from around the world. One important focus in this field is the synthesis of new air electrode materials that can replace the state-of-the-art lanthanum cobaltite-type phases. A host of materials with a wide range of properties has resulted. However, the means and metrics by which promising cathode materials are best characterised are not widely agreed upon within the literature and this can often complicate comparisons between studies. One common approach to conducting analysis of electrodes is to employ so-called ‘symmetrical cell’ tests which aim to isolate the performance of a specific electrode material under open-circuit conditions. However, despite the prevalence of symmetrical cell testing in the literature, there are some widely accepted limitations of the approach (e.g. limited to study at equilibrium conditions). In this work, a selection of air electrode materials with a wide range of properties were studied in both symmetrical and single cell testing set-ups. This case-study was conducted to identify the correlation between the two approaches and to understand how successful the symmetrical cell testing approach is in identifying favourable electrode materials. The results show that, whilst symmetrical-cell testing can be used to identify open circuit behaviours, the comparison between polarisation resistance at open circuit and performance under polarisation is not always perfectly correlated. Crucially, while the symmetrical cell test can provide some guidance in determining whether a new material may show promise, it highlights the need for more detailed studies to understand material performance under polarised conditions

A computational fluid dynamics and finite element analysis design of a microtubular solid oxide fuel cell stack for fixed wing mini unmanned aerial vehicles

© 2019 Hydrogen Energy Publications LLC Computational fluid dynamics (CFD) and finite element analysis (FEA) are important modelling and simulation techniques to design and develop fuel cell stacks and their balance of plant (BoP) systems. The aim of this work is to design a microtubular solid oxide fuel cell (SOFC) stack by coupling CFD and FEA models to capture the multiphysics nature of the system. The focus is to study the distribution of fluids inside the fuel cell stack, the dissipation of heat from the fuel cell bundle, and any deformation of the fuel cells and the stack canister due to thermal stresses, which is important to address during the design process. The stack is part of an innovative all-in-one SOFC generator with an integrated BoP system to power a fixed wing mini unmanned aerial vehicle. Including the computational optimisation at an early stage of the development process is hence a prerequisite in developing a reliable and robust all-in-one SOFC generator system. The presented computational model considers the bundle of fuel cells as the heat source. This could be improved in the future by replacing the heat source with electrochemical reactions to accurately predict the influence of heat on the stack design.Published versio

Effects of thin film Pd deposition on the hydrogen permeability of Pd60Cu40 wt% alloy membranes

AbstractPd60Cu40 wt% (Pd47.3Cu52.7 at%) membranes were surface modified by depositing Pd thin films of three different thicknesses (~100, 800 and 1400nm) on to one side of a range of as-received Pd60Cu40 wt% cold-rolled foils via magnetron sputtering. The hydrogen permeability of the membranes was then measured and compared to the uncoated material. The Pd60Cu40 wt% membrane coated with a 1400nm thick Pd thin film positioned on the feed side (445kPa of hydrogen pressure) during hydrogen permeability measurements and cycled between 50 and 450°C achieved the highest hydrogen permeability of 1.09×10−8molm−1s−1Pa−0.5 at 450°C in the third cycle. This is a 58% increase on the value measured for the as-received Pd60Cu40 wt% membrane under the same conditions.This improvement can be attributed to a Pd-rich Pd–Cu face centred cubic (FCC) phase forming through interdiffusion between the Pd thin film and bulk Pd–Cu membrane as a result of the test conditions used during hydrogen permeability measurements. This introduces a larger hydrogen concentration gradient across the membrane due to the relatively high hydrogen solubility of the Pd-rich Pd–Cu FCC phase resulting in the observed increase in permeability.The Pd60Cu40 wt% membranes coated with a ~1400nm and ~800nm thick Pd thin film retained an almost pure Pd surface throughout cycling between 50 and 450°C with a feed and permeate hydrogen pressure of 445 and 100kPa, respectively. For the deposition technique and test conditions used throughout this work, these surface modified Pd–Cu membranes appear to stabilise the Pd thin films upon cycling across the critical temperature of 295 °;C

Qualitätsprodukt Erziehungsberatung. Empfehlungen zu Leistungen, Qualitätsmerkmalen und Kennziffern

Neben einer Beschreibung der Leistung Erziehungs- und Familienberatung - Beratung und Therapie, präventive Angebote und Vernetzungsaktivitäten - werden ihre Qualitätsmerkmale - gegliedert nach Struktur-, Prozess- und Ergebnisqualität - ausführlich dargestellt und Kennziffern zu ihrer quantitativen Erfassung vorgeschlagen. Der Anhang enthält u.a. eine Kurzfassung der vorliegenden Empfehlungen zu Leistungen, Qualitätsmerkmalen und Kennziffern. (DIPF/Autor

Non-crystallising Glass Sealants for SOFC: Effect of Y2O3 Addition

The joining of ceramic and metal (interconnect) parts is one of the main challenges in the development of solid oxide fuel cells (SOFC). A promising approach to solving this problem is the use of glassy sealants. In this work, we investigated the effect of yttria additions on the properties of SiO2–Al2O3–CaO–Na2O–ZrO2–Y2O3 glass sealants. An increase in the concentration of yttria is shown to reduce the tendency of the glasses under study to crystallisation. A glass containing 4 wt% of Y2O3 is found to be amorphous, even after exposure at 850 °C for 100 h. Moreover, the defectiveness of the glass microstructure, after sealing, is found to decrease along with a growth in the Y2O3 concentration. The developed non-crystallising sealant was successfully applied for joining a YSZ ceramic and an Fe–Ni–Co alloy having the phase transition of around 500 °C. The use of the non-crystallising sealant allows us to join materials with very different thermal expansion coefficients and to avoid cracking under cooling, which might occur due to a large difference in thermal expansion coefficients. © 2019 Elsevier Ltd and Techna Group S.r.l.This study was financially supported by the RFBR project no. 17-58-10006. The research was partially performed using the facilities of the Shared Access Centre “Composition of Compounds” of IHTE UB RAS . The authors are grateful to Dr. S.V. Plaksin for XRD analysis, Dr. N. I. Moskalenko for AES analysis, A. S. Farlenkov for SEM analysis, and A. A. Solodyankin and V. A. Vorotnikov for their assistance in sample preparation

Formation of conductive oxide scale on 33NK and 47Nd interconnector alloys for solid oxide fuel cells

Two grades of chromium-free alloys were studied in order to apply them as interconnectors for solid oxide fuel cells. The surface modification methods were proposed for each alloy with the purpose of forming of oxide scales considering the required physicochemical properties. Investigations of the structure and properties of the obtained oxide scales were performed and the efficiency of the chosen surface modification methods was approved. The samples with the surface modification exhibited higher conductivity values in comparison with the nonmodified samples. A compatibility study of samples with surface modification and glass sealant of chosen composition was accomplished. The modified samples demonstrated good adhesion during testing and electrical resistance less than 40 mOhm/cm2 at 850 ◦C in air, which allowed us to recommend these alloys with respective modified oxide scales as interconnectors for SOFC. © 2019 by the authors.Russian Foundation for Basic Research, RFBR: 17-58-10006This research was funded by the Russian Foundation of Basic Research grant number 17-58-10006. The facilities of the shared access center "Composition of Compounds" of IHTE UB RAS were used in this work