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

Pd–Cu alloys have great potential as hydrogen separation membranes due to their relatively low cost and excellent durability compared to commercial dense metal membranes such as Pd and Pd–Ag alloys. At a composition of Pd60Cu40 wt% the body centred cubic (bcc) phase possesses the highest hydrogen permeability of the Pd–Cu alloy system. Furthermore, a Pd–Cu membrane containing a Pd-rich Pd–Cu fcc phase exhibits improved resistance to hydrogen sulphide (H2S) contamination.The basis of this study was to modify the surface composition of bcc Pd60Cu40 wt% membranes through deposition of a Pd thin film onto one side to produce a stable Pd-rich fcc layer and to investigate its effects on hydrogen permeability. The hydrogen permeability of two as-received Pd60Cu40 wt% membranes (Membranes 1 and 2) was measured in addition to two Pd coated Pd60Cu40 wt% membranes (Membranes 3 and 4) for comparison. A Pd-rich Pd–Cu fcc phase with an approximate composition of Pd70Cu30 wt% was formed as a result of Cu interdiffusion between the Pd–Cu bulk membrane and the Pd thin film during hydrogen permeability testing. This new phase was responsible for the reduction in hydrogen permeability shown in the Samples 3 and 4.Using variable temperature in-situ X-ray diffraction(XRD), it was observed that Cu interdiffusion occurred from the Pd–Cu bulk membrane and into the Pd thin film between 300 and 600 °C under 445 kPa of flowing helium. Under 445 kPa of flowing hydrogen the Pd thin film readily formed the β-palladium hydride (β-PdH) phase at room temperature and gradually formed the α-interstitial hydrogen solid solution (α-PdH) phase at around 200 °C with Cu interdiffusion also occurring between 300 and 600 °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