With increasing attention paid to metal-supported SOFCs recently, metal supports have become important factors in the performance of the cells. The formation of surface oxides and the poisoning of Cr from Cr2O3-forming metal supports often result in the degradation of the cells. However, few studies have focused on developing oxidation resistance and decreasing Cr migration from porous alloys in intermediate temperature metal-supported SOFCs. In this work, Y2O3 and CeO2 coatings were applied to porous AISI 430 stainless steels by sol-gel dip coating. Phases and microstructures of the coatings on the porous metal supports were characterized by XRD and SEM with EDS, respectively. The effects of the coatings on oxidation resistance of the supports were evaluated by cyclic oxidation testing. Electrical and electrochemical properties of LSCF-SDC cathodes and symmetrical cells deposited on the Y2O3-protected metal supports were also investigated. The issue of Cr depletion of the supports was also discussed.

With increasing attention paid to metal-supported SOFCs recently, metal supports have become important factors in the performance of the cells. The formation of surface oxides and the poisoning of Cr from Cr2O3-forming metal supports often result in the degradation of the cells. However, few studies have focused on developing oxidation resistance and decreasing Cr migration from porous alloys in intermediate temperature metal-supported SOFCs. In this work, Y2O3 and CeO2 coatings were applied to porous AISI 430 stainless steels by sol-gel dip coating. Phases and microstructures of the coatings on the porous metal supports were characterized by XRD and SEM with EDS, respectively. The effects of the coatings on oxidation resistance of the supports were evaluated by cyclic oxidation testing. Electrical and electrochemical properties of LSCF-SDC cathodes and symmetrical cells deposited on the Y2O3-protected metal supports were also investigated. The issue of Cr depletion of the supports was also discussed.

By the second decade of the twenty-first century, the preponderance of scholarship examining oil paintings made on stone slabs or metal sheets in Western Europe during the early modern period (fifteenth–eighteenth centuries) had settled on an interpretation of these artworks as artifacts of an elite taste that sought objects for inclusion in private collections of whatever was rare, curious, exquisite, or ingenious. In a cabinet of curiosities, naturalia formed by nature and artificialia made by man all complemented each other as demonstrations of marvelous things (mirabilia). Certainly small-scale paintings on stone or metal exhibited amidst these kinds of rarities aided in aggrandizing a noble or bourgeois collector’s social prestige. As well, they might have derived their interest as collectables because of the painter’s fame or increased capacity for miniaturization on copper plates, or because the painter left a slab of lapis lazuli, for example, partially uncovered to reveal its visually arresting stratigraphy or coloration. Nonetheless, while the lithic and metallic supports might have added value to the oil paintings it was not thought to add meaning. A totalizing theory about this type of artwork, based on a perception of them as if they had only served as conspicuous consumables, therefore overlooks that in other circumstances the stone and metal supports did contribute to the iconographic substance of the paintings. As this dissertation will argue, the introduction of metal and stone supports allowed patrons and painters literally to add another layer of meaning to an oil painting’s imagery. These materials mattered not just as passive receptacles of meaning but as active shapers of significance. Evidence for this hypothesis exists in the historical record in at least three identifiable contexts: Leonardo da Vinci’s Portrait of Ginevra de’Benci (ca. 1474–1478) in relation to the epistemological debate known as the Paragone; funerary monuments in Roman churches inclusive of painted portraits in relation to theories about color and lifelikeness; medallion-shaped, chest plates known as Escudos de monjas (Nuns’ Shields) worn by nuns of some religious orders in Colonial Mexico in relation to pre-Hispanic sacral materials. All three of these case studies ultimately concern the paradoxical materialization of the immaterial fame of the painter, the soul of the deceased, and the Christian divine. Observing them in tandem provides an outline of the origins and development of the technique of painting with oils on stone and metal, and consequently broadens our understanding of this wider, early modern phenomenon. / Art History

Composite thin Pd/Ag alloy membranes with long-term thermal and chemical stabilities have potential applications for H2 separation via catalytic membrane reactors and may be one of the key determinants to achieve the 21st century's global hydrogen economy. This work provides a detailed microstructure characterization study and a better understanding of the fundamental principles involved in the synthesis of a novel Pd/Ag intermetallic diffusion barrier formed by the bi-metal multi-layer (BMML) deposition technique. The BMML deposition technique formed an extremely effective Pd/Ag intermetallic diffusion barrier and significantly improved the thermal and long-term stability of the composite Pd and Pd/alloy membranes over a temperature range of 500-600oC. In addition, high temperature annealing studies over a temperature range of 500-800oC in H2 atmosphere led a thorough understanding of the surface interactions and the phase changes between the Pd and Ag metals and the porous metal support elements (Fe, Cr and Ni) and it was shown by the SEI, EDX and X-ray phase analyses that the Ag/Fe and Ag/Ni binary systems exerted complete immiscibility compared to the completely miscible solid solutions of Pd/Fe and Pd/Ni phases. A novel characterization method of in-situ time-resolved high temperature X-ray diffraction (HTXRD) analysis was used to elucidate the mechanistic details of the isothermal nucleation and growth kinetics of the Pd/Ag alloy phase over a temperature range of 500-600oC in H2. The nucleation of the Pd/Ag alloy phase was instantaneous where the growth mechanism was through diffusion-controlled one-dimensional thickening of the Pd/Ag alloy layer. The Pd/Ag alloy phase growth was strongly dependent upon the deposition morphology of the as-synthesized Pd and Ag layers due to the presence of the heterogeneous nucleation sites. Based on the empirical rate constants derived from the solid-state reaction models, the estimated activation energies for the Pd/Ag alloy phase transformation were 236.5 and 185.6 kJ/mol and in good agreement with the literature values of 183-239.5 kJ/mol. The successful utilization of surface modification techniques and modified plating conditions led to the synthesis of several dense Pd/Ag layers, which were as thin as 5-15 µm with a bulk Ag content in the 10-40 wt% range. The long-term testing of the composite Pd/Ag membranes (5-15 µm) at 500oC showed stable hydrogen permeances as high as 30 to 54 m3/m2-h-atm0.5 with H2/He selectivities ranging from 200 to 14000. Furthermore, the atomic absorption flame analysis was used for the first time to elucidate the effects of temperature, initial metal ion concentration, initial hydrazine concentration and bath agitation on the electroless plating rates of Pd and Ag. The electroless plating of both Pd and Ag were strongly affected by the external mass transfer in the absence of bath agitation. The external mass transfer limitations for both Pd and Ag deposition have been overcome at or above an agitation rate of 400 rpm, resulting in a maximum conversion of the plating reaction and dramatically shortened plating times with the added advantage of uniform deposition morphology as evidenced by the SEI micrographs. Finally, the agitation rate of 400 rpm was successfully employed for the synthesis of composite Pd and Pd/Ag membranes. The H2 permeance for a 4.7 µm thick pure-Pd membrane at 400oC was as high as 61 m3/m2-h-atm0.5 with H2/He selectivity over 310 after a total testing period of 690 hours.