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MOLYBDENUM AND HASTELLOY B 1925Limited corrosion tests were also carried out with an experimental Fe-30Ni-15Mo alloy. The objective of these tests was to determine whether molybdenum might provide better corrosion protection from Na2S3 in an ironbased alloy. However, 100h exposure tests showed metal losses greater than those observed with Hastelloy B. ConclusionsMolybdenum corroded very slowly in sulfur and sodium polysulfides at 623 K. This indicated that molybdenum, used as an alloying additive with nickel-and ironbased alloys or as a coating material, might be a good candidate for constructing containers for sodium/sulfur cells. The assumed MoSs corrosion scale is an electrical conductor; therefore such containers would also make good positive-electrode current collectors.The high molybdenum content of Hastelloy B results in good corrosion protection when it is exposed to sulfur at 623 K. However, in Na~S3 very high corrosion rates were measured, with only small improvements over rates measured previously for pure nickel. An experimental Fe-Ni-Mo alloy also corroded very rapidly in Na2S3 at 623 K. Thus, molybdenum is not an effective alloying element for producing an iron-or nickel-based alloy to use as a sodium/sulfur cell container.

The technique of solution aerosol thermolysis (SAT) for the production of ceramic electrolytic films suitable for solid oxide fuels cells was investigated. The research has focused on the optimization of process parameters and characterization of the obtained films by means of X-ray diffractometry and scanning electron microscopy/energy-dispersive spectroscopy. Dense films of gadolinia-stabilized ceria of uniform thickness have been successfully produced on substrates consisting of dense disks of yttria-stabilized zirconia by SAT using nitrate salts of the precursors dissolved in an ethanol-water solvent. Substrate temperature is an important parameter and in this system the best initial values identified were of the order of 400-420°C. The interplay between initial substrate temperature, solution flow rate, and postdeposition temperature is important for a good-quality film.

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Two Cu-based anode cermets suitable for direct hydrocarbon oxidation in Solid Oxide Fuel Cells (SOFC) based on yttria stabilized zirconia (YSZ) electrolyte were tested in the temperature range (500-800°C). The ceramic c o m p o n e n t s w e r e C e O 2 a n d t h e p e r o v s k i t e La 0.75 Sr 0.25 Cr 0.5 Mn 0.5 O 3−d (LSCM). The cermets were made in both the form of pellets and films applied onto the YSZ electrolytes. Pellets exhibited good mechanical strength and resistance to fracture in both oxidized and reduced state. Cu-LSCM cermets exhibited good redox cycling behavior between 700-800°C. Reduction temperature plays a significant role on final morphology with Cu segregation occurring at 800°C. Cu-LSCM films were found to exhibit lower polarization resistances than CuCeO 2 under 5% H 2 . Examination of the data revealed a poorer contact of the Cu-CeO 2 electrode with the YSZ surface than the Cu-LSCM electrode. Reduction temperature should be less than 750°C to ensure suitable microstructure and adhesion of both film electrodes with the electrolyte.