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This paper presents progress in development of microstructure in MCFC electrodes. Within these studies the influence of microstructure parameters of materials, such as porosity and pore size distribution on the fuel cell power density is analyzed using pure nickel. The results indicate that the optimal range of porosity for MCFC electrodes can be related with specific surface area, which reveals maximum for volume fraction of pores being 55–60%. The porosity of the cathode should be 5–10% higher due to in situ oxidation taking place during the startup procedure. Pore size distribution, PSD, was found to be especially important in MCFC, where liquid electrolyte infiltrates electrodes by capillary action. Through the application of specific porogens, multimodal PSD can be obtained, which significantly enhances reference cell power density. Optimization of basic microstructure parameters informed the design of a new concept MCFC cathode incorporating bi-layered materials, where each layer is appointed a different role. The application of commercial nickel foam as the gas side layer of the cathode increased power density and reduced the brittleness of the element, which is of key importance from the technological point of view.

This paper demonstrates the benefits of using a metallic foam support within molten carbonate fuel cell (MCFC) cathodes. A state-of-the-art fabrication process based on tape casting has been developed to produce microporous electrodes with a nickel foam scaffold. Surfactant was added to control the depth to which the slurry infiltrated the foam. New cathodes were used as an alternative to the traditional cathode in the single cell assembly and were tested for power density. Mechanical properties were compared with the current state-of-the-art. The results show that the use of metallic foams for high temperature fuel cell electrodes is beneficial from the technological point of view, especially in larger scale production. It was also found that the resultant continuous metallic structure of the microporous electrodes delivered a slight enhancement to fuel cell power density.

A three-dimensional (3D) sintering method of bulk magnetron targets has been developed recently. However, the use of bulk target had the following limitations: constrained geometry, limited chemical-phase composition, small size and cost-effectiveness. Thus a novel approach of surface sintering (2D) was arranged by a method of electromagnetic discharge evolution without applying any mechanical press. In the proposed method, the internal energy of pulsed plasma flux (~102.3 J) was dissipated at a tungsten (W) powder interface, therefore providing a form of sintered body with a density of 9.24–14.21 g/cm3 in the crystal structure of (α)-W. The morphology view indicates that, for the most part of sinters, only a subsurface (< 100 nm) was well-consolidated, which was in accordance with an almost fourfold increase in thermal diffusivity there, as showed the results of laser flash analysis. Subsequently, the decrease in mean porosity distribution (Vv) from 42.4% to 27.1% in consolidated surface was confirmed by using the microcomputed tomography (μCT) reconstruction. The (2D) sintered target was then used in the synthesis of pure metallic films by gas injection magnetron sputtering. As a result, a conductive (β)-W phase was recognized (103–405 μΩ cm), giving a promising hope for spintronic device applications.

Preparation of a ternary ReBx–Ti compound within a single magnetron target, forming a plasma surface sintering (PSS) conditions, were investigated. An ionized‑neon pressure of 40 Pa induced sintering power pulses (Ei) with energies of up to 3.1 kJ, which resulted in a low-porosity rhenium boride (3.2%) structure within a solid titanium matrix (ReBx–Ti). The prepared targets showed promising resistance to high temperatures (5.45 mm2/s of thermal diffusivity), after the PSS process at a temperature above 2100 °C. These as-surface-sintered magnetron targets were further used in gas injection magnetron sputtering to obtain Re–B–Ti films characterized by an enhanced deposition rate (120 nm/min). Quantitative analysis of these films revealed that the B/Re ratio was in deficit in comparison to the stoichiometry of as-prepared cathode materials. A multiple-chemical-bond state showed the occurrence of Re B, Ti B, B B, Ti Ti, Ti O, and B O phases, of which TiB2 and ReB2 were dominant, forming therefore a glass-like structure. All gathered data indicated a maximum Vickers microhardness value (36.4 GPa), emphasizing the valuable mechanical response of the deposited Re–B–Ti films, as well as the retaining of their good self-passivation effect, attributed by the oxide phases.

In this study, the effect of microstructure of porous nickel electrode on the performance of high temperature fuel cell is investigated and presented based on a molten carbonate fuel cell (MCFC) cathode. The cathode materials are fabricated from slurry consisting of nickel powder and polymeric binder/solvent mixture, using the tape casting method. The final pore structure is shaped through modifying the slurry composition - with or without the addition of porogen(s). The manufactured materials are extensively characterized by various techniques involving: micro-computed tomography (micro-XCT), scanning electron microscopy (SEM), mercury porosimetry, BET and Archimedes method. Tomographic images are also analyzed and quantified to reveal the evolution of pore space due to nickel in situ oxidation to NiO, and infiltration by the electrolyte. Single-cell performance tests are carried out under MCFC operation conditions to estimate the performance of the manufactured materials. It is found that the multi-modal microstructure of MCFC cathode results in a significant enhancement of the power density generated by the reference cell. To give greater insight into the understanding of the effect of microstructure on the properties of the cathode, a model based on 3D tomography image transformation is proposed.

In the present paper, fabrication, characterization and modeling techniques are combined to analyze the microstructure of tape-cast open-porous materials. This kind of material is highly permeable to gases and at the same time has a high catalytic reactivity which leads to successful applications e.g. in high-temperature fuel cells. However, the microstructure of such material is complex and not fully understood. The main goal of this paper is to provide a realistic model of tape-cast porous microstructures based on the simulation of their fabrication process. In order to accomplish this, four different samples are fabricated by firing the green tapes obtained by the tape casting process. The microstructure of each sample is analyzed by means of micro-tomographic image data. Furthermore, a method for modeling open-porous 3D microstructures is proposed, where the cast slurry is represented by a system of spheres with a given volume fraction and radius distribution. Model-based post-processing of the simulated microstructures is proposed to improve the fit of the surface area. Finally, model validation is performed by means of a detailed statistical analysis of experimentally produced and virtual microstructures. Keywords: Open-porous materials, 3D microstructure modeling, Micro-computed tomography, Molten carbonate fuel cell

In the present paper, advanced characterization and modeling techniques are combined to analyze the microstructure of open-porous tape-cast materials and its influence on the permeability. Four samples with different pore former content were fabricated via the tape casting method. Subsequent firing of the manufactured green tapes allowed to obtain open-porous structures with porosity in range 45–50%. Quantitative image analysis of 3D micro-computed tomography data was performed and detailed porous microstructure characteristics were obtained. Based on the acquired data, representative model of the open-porous microstructure has been developed. Finite volume method was utilized to calculate the permeability of various microstructural scenarios. Results obtained indicate that porosity, mean pore size and constrictivity directly influence the fluid flow properties. Notable variations in the constrictivity and resulting permeability may be caused by a significant addition of porogen, for which the connectivity of the pores change and creation (or its lack) of free-paths affects the fluid flow. Keywords: Porous materials, Microstructure, Permeability, Modeling of flow, Constrictivity