Dense composites of silver and Sc-stabilized ZrO2 (Ag-ScSZ) are manufactured from ScSZ sub-micrometric particles coated with silver using Tollens’ reagent. The fabrication route allows for a significant reduction in the level of silver, as low as 8.6 vol %, required for percolation well below the usual 30-40 vol % previously believed as indispensable. The fabrication method ensures a metallic conductivity of 186 S cm-1 and an oxygen flux of 0.014 umol cm-2 s-1 at 600°C for a 1-mm thick membrane when used as a pressure-driven separation membrane between air and argon. To gain insight into the role of oxygen transport in Ag and ScSZ, a dense non-percolating sample is analysed by impedance spectroscopy and the transport of oxygen through both phases is modelled. Oxygen transport takes place in both silver and ScSZ but it is still dominated by transport in the ionic conductor and therefore a large volume fraction of the ion conductor is beneficial for the separation. The oxygen transport in the silver clusters inside the composite is dominated by diffusion of neutral species and not by the charge transfer reaction at the interface between ScSZ and silver, yet small silver particles at the surface improve the reduction of oxygen.
Oxygen separation with low silver content scandia-stabilised zirconia composite membranes
Bertei AInvestigation
;
2017-01-01
Abstract
Dense composites of silver and Sc-stabilized ZrO2 (Ag-ScSZ) are manufactured from ScSZ sub-micrometric particles coated with silver using Tollens’ reagent. The fabrication route allows for a significant reduction in the level of silver, as low as 8.6 vol %, required for percolation well below the usual 30-40 vol % previously believed as indispensable. The fabrication method ensures a metallic conductivity of 186 S cm-1 and an oxygen flux of 0.014 umol cm-2 s-1 at 600°C for a 1-mm thick membrane when used as a pressure-driven separation membrane between air and argon. To gain insight into the role of oxygen transport in Ag and ScSZ, a dense non-percolating sample is analysed by impedance spectroscopy and the transport of oxygen through both phases is modelled. Oxygen transport takes place in both silver and ScSZ but it is still dominated by transport in the ionic conductor and therefore a large volume fraction of the ion conductor is beneficial for the separation. The oxygen transport in the silver clusters inside the composite is dominated by diffusion of neutral species and not by the charge transfer reaction at the interface between ScSZ and silver, yet small silver particles at the surface improve the reduction of oxygen.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
