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A novel micro-tubular solid oxide fuel cell (SOFC) design with an inert support was proposed for operation on direct hydrocarbon fuels with an improved stability. In this design, the inert support also serves as a diffusion barrier between the fuel stream and Ni cermet anode. The barrier effect leads to higher local steam to carbon ratios in the anode, thus inhibiting carbon deposition. To demonstrate this concept, we fabricated micro-tubular SOFCs with a porous yttria-stabilized zirconia (YSZ) support. Ni, Ni-scandia-stabilized zirconia (ScSZ), ScSZ, strontium-doped lanthanum manganite (LSM)-ScSZ, and LSM were used as the anode current collector, anode, electrolyte, cathode, and cathode current collector, respectively. Good electrochemical performance was achieved with hydrogen and methane fuels in a temperature range 600-750 °C. Continuous cell operation on direct methane fuel for >40 h at 750 °C under moderate current densities delivered stable voltage without any evident performance degradation due to carbon deposition. The absence of carbon deposition on the anode and anode current collector layers was also confirmed by scanning electron microscope images and energy-dispersive X-ray spectra. We further discuss oxidation mechanism of the direct methane fuel and removal of the carbon possibly formed in the anodic layers during stability testing. [ABSTRACT FROM AUTHOR]

This study was performed in order to investigate a possibility to obtain Co-W microbumps via electrochemical routes, because this alloy recently has gained attraction as a novel barrier against copper diffusion. In order to be applied in flip-chip technology, barrier layers should be void-free and uniformly deposited on the entire area of a die to ensure high reliability and high performance of wafer bump-solder interface. To meet these requirements, a set of potentiostatic and galvanostatic electrodeposition was carried out from a citrate electrolyte, at pH 5 and at room temperature. The tests done confirm that void-free Co-W bumps with a uniform tungsten content along the bump can be obtained by potentiostatic and galvanostatic electrodeposition. Successful electrodeposition of Cu/Co-W/Sn layers with good adhesion between them and uniformity on the entire array of bumps also was obtained. The XPS data confirm that electrodeposited Co-W layers can act as a good barrier between Sn and Cu. [ABSTRACT FROM AUTHOR]