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An Fe21Cr7Al1Mo0.5Y alumina-forming stainless steel is designed and evaluated as a material for porous supports for oxygen transport membranes. The thermal expansion coefficient, elastic modulus and creep rates of the alloy are presented. The microstructure, porosity and pre-oxidation conditions are optimised simultaneously in-situ during sintering by controlling the growth rate of the oxide scale. Oxidation of metal supports with 20–40% porosity at 850 °C and oxygen partial pressure of 10 − 11 kPa showed sub-parabolic kinetics and stability over 3000 h. The FeCrAl steel shows vastly superior oxidation resistance compared with an FeCr steel of similar composition and porosity. Modelling of the alloy lifetime as a function of surface area and Al-content was performed, and lifetimes over 30 000 h are predicted for a metal support with 30% porosity operating at a temperature of 750 °C, where the oxidation and creep rates are sufficiently low. Ceramic interlayers with graded porosity and pore-size were applied and co-fired with the metal supports, producing substrates that were shown to be viable for a 3 μm dense Ce 0.8 Gd 0.2 O 1.9 − δ oxygen transport membrane deposited using sputtering.

The oxidation resistance of the Fe-Cr alloy backbone structure of metal supported solid oxide fuel cells is significantly improved when infiltrated with gadolinium doped ceria (CGO) particles. The mechanism for the improved oxidation behaviour is elucidated using various analytical transmission electron microscopy (TEM) techniques including energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy of focus ion beamed TEM samples. The infiltrated CGO is predominately converted into CeFeO3 after high temperature processing, protecting the alloy. A thin layer of Cr-oxide is observed to be sandwiched between the CeFeO3/CGO layers and the Fe-Cr alloy particles. Despite the improved oxidation resistance at open circuit voltage, during fuel cell testing accelerated oxidation is observed at the triple phase boundaries. (C) 2012 Elsevier B.V. All rights reserved.

Effects of novel dual layer coatings Co3O4/La0.85Sr0.15MnO3-delta on high temperature oxidation behaviour of candidate steels for interconnects are studied at 1123 K in flowing simulated ambient air (air + 1% H2O) and oxygen. Four alloys are investigated: Crofer 22 APU, Crofer 22 H, E-Brite and AL 29-4C. The reaction kinetics is followed by measuring the mass increase of the samples over time. The oxide scale microstructure and chemical composition are investigated by scanning electron microscopy/energy dispersive spectroscopy. The kinetic data follow the parabolic rate law. It is found that the oxidation reaction is limited by outward Cr3+ diffusion in the chromia scale. The coating effectively reduces the oxidation rate. Reactions and cation inter-diffusion between the coating and the oxide scale are observed. Long term effects of these interactions are discussed and practical implications for interconnect electrochemical performance are suggested. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

The effect of single layer La0.85Sr0.15MnO3−δ (LSM) coatings on high temperature oxidation behaviour of four commercial chromia-forming steels, Crofer 22 APU, Crofer 22 H, E-Brite and AL 29-4C, is studied. The samples were oxidized for 140–1000 h at 1123 K in flowing simulated ambient air (air + 1% H2O) and oxygen and corrosion kinetics monitored by mass increase of the materials over time. The oxide scale microstructure and chemical composition are investigated by scanning electron microscopy/energy-dispersive spectroscopy. The kinetic data obey a parabolic rate law. The results show that the LSM coating acts as an oxygen transport barrier that can significantly reduce the corrosion rate.

Six different coatings consisting of fluorite-, corundum-, spinel- or perovskite-type oxides were deposited on a Fe22Cr alloy (Crofer 22APU) and oxidized at 900 °C in moisturized air. Five of the coatings prevented break-away oxidation otherwise observed for the uncoated alloy, and the parabolic oxidation rate constant was reduced with 50–90% of that for uncoated alloy. One coating consisting of MnCo 2 O 4 did not significantly affect the oxidation rate of the alloy, and just as for uncoated samples break-away oxidation occurred for MnCo 2 O 4 coated samples. The interaction mechanisms between the growing oxide scales and applied coatings can be classified according to three types.

Scanning electron microscopy and cyclic voltammetry were used to investigate the high-temperature oxidation behavior of two solid oxide fuel cell interconnect steels. One alloy had a low content of manganese; the other alloy had a high content of manganese. Four reduction and four oxidation peaks were observed in the voltammograms of the low manganese alloy at a temperature of 800 °C. The voltammograms of the alloy with a high content of manganese were different. At 600 °C, three reduction peaks and two oxidation peaks were observed. At 800 °C, additional peaks were observed in the voltammogram for this alloy.

Long-term oxidation behaviour of eight ferritic steels with 20-29 wt.% chromium (F 20 T, TUS 220 M, AL 453, Crofer 22 APU, Crofer 22 H, Sanergy HT, E-Brite and AL 29-4C) has been studied. The samples were cut into square coupons, ground and annealed for 140-1000 h at 1173 K in flowing, wet hydrogen, air and pure oxygen. The reaction kinetics was followed by mass increase of individual samples over time. Parabolic rate law was observed for most measurements. The respective rate constants have been evaluated and compared. The chemical composition of the oxide scale was investigated by XRD and SEM/EDXS. The major constituent is chromium oxide. Other oxides, such as (Mn, Cr)(3)O(4), MnTiO(3), SiO(2) or Al(2)O(3), are also present in different amounts depending on the chemical composition of the steel. The oxidation rate increases with increasing oxygen partial pressure and decreasing chromium concentration. Chromium diffusion coefficients in Cr(2)O(3) and parabolic rate constants are compared. The reaction mechanism for the chromia formation is suggested. The results are discussed with respect to the applications of the steels in a working solid oxide electrolyser cell stack. Furthermore, suggestions for the development of a superior alloy composition are given. (C) 2010 Elsevier Ltd. All rights reserved.

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Analyses of heme-attached amino acid sequences in known hemoprotein superfamilies provide a basis for prediction of such sequences in hemoproteins of unknown three-dimensional structure. Among 11 histidine residues conserved in subunit I of 3 mammalian and 2 fungal cytochrome oxidases the sequence around His-233 (human) is the most conserved and shows remarkable similarity to the sequence of the oxygen binding site in globins. Furthermore, the gene coding for subunit I in Saccharomyces cerevisiae and the gene for leghemoglobin in soybean are both split by introns right after these similar histidine sequences. The predicted distal histidine sequence of subunit I provides for heme a3 and Cua3 binding and has an extraordinarily high content of aromatic residues. These aromatic groups may serve as a molecular electron capacitor. Transmembrane sequences and electron transfer sequences are proposed.

The feasibility of a harbour project, which involves dredging of an access channel, may to a large extent depend on the future maintenance dredging in the channel. It is therefore important to be able to calculate sedimentation in dredged channels with sufficient accuracy. In 1974 and 1975 the Danish Hydraulic Institute (DHI) carried out a study of the most feasible access channel to Warri Port situated in the Western Niger Delta, Nigeria. Two alternative entrances were studied and in conclusion it was recommended to improve the existing access channel through Escravos Entrance.