Fabrication of Electrochemical Ceramic Membrane with Assistance of Metallization by the Electroless-plating Technique
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AA8.1.1
Fabrication of Electrochemical Ceramic Membrane with Assistance of Metallization by the Electroless-plating Technique Y-Y. Liu1, L. Hong, Z-C. Shao, and H-X. Jiang Institute of Materials Research & Engineering, 3 Research Link, Singapore 117602 1 Department of Chemical & Environmental Engineering National University of Singapore 10 Kent Ridge Crescent, Singapore 119260 ABSTRACT This work developed a metal-reinforced ceramic membrane processing approach [by using perovskite La0.2Sr0.8 CoO3-x (LSCO-80) as the model membrane] with the aim of overcoming the membrane-cracking problem. A thin layer of Ag/Pd alloy was incorporated into the LSCO-80 membrane made by dip coating and sintering. It is not viable to obtain a Pd/Ag alloy film using the co-plating method because Ag+ ion strongly inhibits chemical reduction of Pd2+ ion, and the alkaline plating bath causes severe etching of LSCO-80. This obstacle was circumvented through a layer-by-layer deposition procedure, in which Ag and Pd layers were deposited subsequently onto LSCO membrane. The Ag and Pd layers undergo alloying when the laminar structure was subjected to calcinations at 1000oC. It was found that the Pd/Ag alloy drifts beneath into pores in the LSCO layer. The resultant metal-ceramic composite membrane shows excellent structural integrity and free of micro-cracks.
INTRODUCTION The membrane made of the perovskite complex oxides, La1-xAxCo1-yByO3-δ , has great potentials in the solid electrochemical reaction technology [1-2]. Important applications include their use as the cathode material in the solid oxide fuel cells (SOFC) and use as the membrane materials for coupling air separation with the catalytic oxidations of small hydrocarbons provided the material possesses the mixed-conductive property. For the application in the catalytic membrane reactor, a dense but adequately thin membrane is therefore required in order to ensure the unique electrochemical separation mechanism to be executed [3]. However, heavy material cracking in ceramic membranes driven by thermal mismatch between the membrane and its support is an existing problem impeding successful fabrication of this type of ceramic electrochemical membranes, and their further industrial applications [4]. The model membrane assembly of this work is composed of three moieties; a porous MgO disk as the support, an overlaying La0.2Sr0.8CoO3-δ (LSCO-80) membrane and an intercalated Pd/Ag alloy network. In the absence of the alloy network, a porous and defectprevalent LSCO-80 membrane is always obtained after sintering the powder-coating layer of this material (see figure 1). It is known that the ceramic oxygen-separation membrane is operated at rather high temperature in order to gain a high oxygen flux. The prime reason of choosing Pd/Ag alloy is that the alloy will not be oxidized and therefore offer an elastoviscous intercalating network at the operation high-temperature as long as an appropriate Pd content is maintained in the alloy.
AA8.1.2
Defects
Figure 1. SEM graph of sintered LSCO mem
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