Papers by Author: Olivera Kesler

Abstract: In this study, an addition of Co and Cu oxides to Sm0.2Ce0.8O1.9 (SDC) was studied to improve the SDC sinterability. It has been found that both Co and Cu oxide are very effective as sintering aids, and the SDC sintering temperature can be reduced from 1400°C without aids to below 1000°C with only 1at.% of either Cu or Co. As compared to the pure SDC, a slight decrease of ionic conductivity was observed in SDC with Cu sintering aid. There is no obvious effect on electrochemical property of SDC with Co sintering aid under 2.5at.%.

Abstract: Plasma spray processing is a low-cost, rapid manufacturing technique that is widely used industrially for fabrication of thermal barrier and wear- and corrosion-resistant coatings. Because the technique can be used to rapidly deposit coatings of high melting temperature materials with good substrate adhesion, it has also been applied to the production of individual component layers in tubular solid oxide fuel cells (SOFCs), and more recently, in planar SOFCs. The use of plasma spray processing for the fabrication of fuel cell components presents unique challenges, due to the high porosities required for the electrode layers and fully dense coatings required for electrolytes. Application of plasma spray processing for the manufacture of solid oxide fuel cells is discussed, with consideration of potential advantages of the technique compared to standard SOFC wet ceramic processing routes. Major challenges faced in the adaptation of the processing method to solid oxide fuel cell manufacture are discussed, along with current research approaches being used to overcome these challenges. Recent developments in the use of the technique for the rapid onestep manufacturing of direct oxidation SOFC anodes are discussed, for composite material combinations that cannot be co-sintered due to widely divergent melting points. The impacts of plasma sprayed coating properties on solid oxide fuel cell performance are considered, and implications of the use of the technique on overall stack and system manufacturing costs are discussed.

Abstract: Porous composite cathodes containing (La0.8Sr0.2)0.98MnO3 (LSM) and yttria stabilized zirconia (YSZ) for use in solid oxide fuel cells (SOFCs) have been produced by air plasma spraying. Deposition was carried out using axial powder injection for increased deposition efficiency and composition control. A number of composite cathodes were produced using different combinations of parameter values within the identified range. Successful coatings were then characterized for composition and porosity using EDX and SEM. As a result of these tests, combinations of input parameter values were identified that are best suited to the production of coatings with microstructures appropriate for use in SOFC composite cathodes.

Abstract: Extensive interfacial reactions are known to occur between Fe-Co based perovskite cathode materials and the standard solid oxide fuel cell (SOFC) yttria stabilized zirconia (YSZ) electrolyte. Thin films of gadolinia doped ceria (GDC) could be used as a diffusion barrier between the cathode and the electrolyte. The present work investigates spin coating thin diffusion reaction inhibiting films onto SOFC electrolytes. The chemical and structural evolution of ethylene glycol based precursor solution is studied by means of rheology, x-ray diffraction (XRD), high temperature XRD (HT-XRD), Fourier-transformed infrared spectroscopy (FTIR) and differential thermal analysis (DTA). The studies show that cerium formate is formed as an intermediate resin. Thin films, up to 500 nm thick, of gadolinia doped ceria (GDC) are successfully produced by multiple spin coating of polymerized ethylene glycol derived solutions on 200 1m thick YSZ tapes. The GDC and YSZ interfacial surface morphology and film thickness are studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). These films are shown to successfully prevent the creation of non-conducting reaction phases at the cathode-electrolyte interface by blocking interdiffusion.

Abstract: A new rapid manufacturing technique for the production of SOFC anodes for direct oxidation of hydrocarbon fuels has been demonstrated. Composite anodes with doped ceria as catalyst and ion conductor and copper as electronic conductor have been fabricated by plasma spraying in air. The process, which can be readily automated and scaled up for mass production, provides a rapid method to produce anodes with mixtures of low and high melting temperature components in several minutes. These anodes previously have required complex multi-step, multi-day processes involving infiltration of sintered pre-forms. This work demonstrates the feasibility of using plasma spray processing to manufacture composite Cu-SDC coatings for application in direct-oxidation SOFC anodes.