| 1. |
- Ignaczak, Justyna, et al.
(författare)
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Fe-modified Mn2CuO4 spinel oxides: coatings based on abundant elements for solid oxide cell interconnects
- 2023
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Ingår i: International Journal of Hydrogen Energy. - 0360-3199. ; 48:92, s. 36076-36093
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Tidskriftsartikel (refereegranskat)abstract
- 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 °C 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.
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| 2. |
- Koszelow, D., et al.
(författare)
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Pre-oxidation of porous ferritic Fe22Cr alloys for lifespan extension at high-temperature
- 2024
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Ingår i: Corrosion Science. - 0010-938X. ; 234
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Tidskriftsartikel (refereegranskat)abstract
- Pre-oxidation of porous ferritic Fe22Cr alloys was extensively studied in this paper. Weight gain measurements and SEM analysis revealed that pre-oxidation performed at 900°C for 40 min increased the lifespan of the alloy. A Cr evaporation study did not disclose any significant influence of the pre-oxidation process on the Cr content in the alloy. For a more detailed assessment, TEM imaging and X-ray tomography measurements of pre-oxidized samples were performed. These analyses showed that alteration in the grain and grain boundary diffusion fluxes might be the key for explaining the corrosion prevention role of pre-oxidation.
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| 3. |
- Makowska, Małgorzata, et al.
(författare)
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Flexible sample environment for high resolution neutron imaging at high temperatures in controlled atmosphere.
- 2015
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 86:12
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Tidskriftsartikel (refereegranskat)abstract
- High material penetration by neutrons allows for experiments using sophisticated sample environments providing complex conditions. Thus, neutron imaging holds potential for performing in situ nondestructive measurements on large samples or even full technological systems, which are not possible with any other technique. This paper presents a new sample environment for in situ high resolution neutron imaging experiments at temperatures from room temperature up to 1100 °C and/or using controllable flow of reactive atmospheres. The design also offers the possibility to directly combine imaging with diffraction measurements. Design, special features, and specification of the furnace are described. In addition, examples of experiments successfully performed at various neutron facilities with the furnace, as well as examples of possible applications are presented. This covers a broad field of research from fundamental to technological investigations of various types of materials and components.
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| 4. |
- Makowska, Malgorzata Grazyna, et al.
(författare)
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Coupling between creep and redox behavior in nickel - yttria stabilized zirconia observed in-situ by monochromatic neutron imaging
- 2017
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 340, s. 167-175
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Tidskriftsartikel (refereegranskat)abstract
- Ni-YSZ (nickel - yttria stabilized zirconia) is a material widely used for electrodes and supports in solid oxide electrochemical cells. The mechanical and electrochemical performance of these layers, and thus the whole cell, depends on their microstructure. During the initial operation of a cell, NiO is reduced to Ni. When this process is conducted under external load, like also present in a stack assembly, significant deformations of NiO/Ni-YSZ composite samples are observed. The observed creep is orders of magnitude larger than the one observed after reduction during operation. This phenomenon is referred to as accelerated creep and is expected to have a significant influence on the microstructure development and stress field present in the Ni-YSZ in solid oxide electrochemical cells (SOCs), which is highly important for the durability of the SOC. In this work we present energy selective neutron imaging studies of the accelerated creep phenomenon in Ni/NiO-YSZ composite during reduction and also during oxidation. This approach allowed us to observe the phase transition and the creep behavior simultaneously in-situ under SOC operation-like conditions.
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| 5. |
- Makowska, Malgorzata G., et al.
(författare)
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Effect of stress on NiO reduction in solid oxide fuel cells: a new application of energy-resolved neutron imaging
- 2015
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Ingår i: Journal of Applied Crystallography. - 1600-5767. ; 48, s. 401-408
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Tidskriftsartikel (refereegranskat)abstract
- Recently, two new phenomena linking stress field and reduction rates in anode-supported solid oxide fuel cells (SOFCs) have been demonstrated, so-called accelerated creep during reduction and reduction rate enhancement and nucleation due to stress (Frandsen et al., 2014). These complex phenomena are difficult to study and it is demonstrated here that energy-resolved neutron imaging is a feasible technique for combined mechanics-chemical composition studies of SOFC components, including commercially produced ones. Cermet anode supports, which prior to the measurements were reduced under varying conditions such as different temperatures, various times and different values of applied stress, have been measured. Thus, samples with different contents (and gradients) of Ni and NiO phases were investigated. The first Bragg edge transmission neutron measurements applied for the studies of the reduction progress in these samples were performed at two neutron beamline facilities (ISIS in the UK, Helmholtz Zentrum Berlin in Germany). The obtained results demonstrate the possibility to image and distinguish NiO and Ni phases within SOFC anode supports by energy-resolved neutron imaging and the potential of the neutron imaging method for in situ studies of reduction processes.
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| 6. |
- Makowska, Malgorzata G., et al.
(författare)
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In situ time-of-flight neutron imaging of NiO-YSZ anode support reduction under influence of stress
- 2016
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Ingår i: Journal of Applied Crystallography. - 0021-8898. ; 49:5, s. 1674-1681
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Tidskriftsartikel (refereegranskat)abstract
- This article reports on in situ macroscopic scale imaging of NiO-YSZ (YSZ is yttria-stabilized zirconia) reduction under applied stress - a phase transition taking place in solid oxide electrochemical cells in a reducing atmosphere of a hydrogen/nitrogen mixture and at operation temperatures of up to 1073K. This process is critical for the performance and lifetime of the cells. Energy-resolved neutron imaging was applied to observe the phase transition directly with time and spatial resolution. Two different approaches are presented for using this imaging technique for the investigation of chemical and physical processes requiring controlled atmosphere and elevated temperature. The first type of measurement is based on alternating stages of short-term partial chemical reaction and longer neutron image acquisition, and the second type is a real in situ neutron imaging experiment. Results of applying energy-resolved neutron imaging with both approaches to the NiO-YSZ reduction investigation indicate enhancement of the reduction rate due to applied stress, which is consistent with the results of the authors' previous research.Results of the first in situ energy-resolved neutron imaging of NiO-YSZ (YSZ is yttria-stabilized zirconia) reduction under applied stress are presented. Neutron experiments were performed at the pulsed neutron source ISIS (UK) using a time-of-flight approach.
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