Ceramic electrolytes and secondary recovery

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Two important applications for ionically conducting ceramics are high temperature in situ sensors and solid oxide fuel cells.  Unfortunately, stabilized zirconia used for determining dissolved oxygen during steelmaking operations becomes inaccurate at low oxygen concentrations due to partial decomposition.  Two new solid electrolytes that are more stable, Y2O3-CaO and Dy2O3-CaO, are being studied in an effort to develop a more accurate oxygen sensor.  Major problems associated with gas sensors for polluting and greenhouse gases, e.g., CO2, SO2, NOx, are sluggish response, poor sensitivity and limited concentration range.  To help overcome these difficulties, miniaturization using microelectronic techniques and a new vapour deposition method, polarized electrochemical vapour deposition, are being applied to sensors involving oxysalt or B"-Al2O3 electrolytes.  The vapour deposition technique has been extended to improve the electrochemical activity and stability of the composite anode in the solid oxide fuel cell.  Yttria stabilized zirconia is deposited on previously screen printed nickel to provide a unique composite microstructure - both phases are continuous to minimize resistance losses.  Included in this work are ceria deposition on nickel to improve catalytic behaviour and testing with natural gas to see if the ceramic coating restricts troublesome carbon deposition.   A detailed investigation of oil sands fly ash on mineralogical changes occuring during its formation from coke combustion and, to a lesser extent, during roasting with additives has, in part, led to a process for the recovery of vanadium and several byproducts from this waste product.  Also, a process has been proposed to convert zircon from the oil sands tailings to much more valuable zirconia using another waste product, oil sands coke.  Mineral transformations, achieved by roasting with additives, are being extended to treat other complex and potentially hazardous waste products either to recover valuable metals or make toxic elements environmentally benign, e.g., zinc ferrite residue, electric arc furnace steelmaking dust, copper-nickel-arsenic sulphide waste.