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Inorganic Oxides Materials
The Building Energy Materials and Components Department is working along with the Energy Conversion Department at EMPA to investigate the deposition of dense oxide films onto porous oxide and hybrid layers using cost-effective non-vacuum deposition methods (DEPOLA). Our department is investigating different soft chemistry techniques were investigated to optimize the deposition of porous anode materials ( yttria-stabilized zirconia and nickel, YSZ-Ni) as substrates for AA-CVD electrolyte thin films. As alternative to expansive traditional sol-gel routes, which involves use of expansive organic precursor, epoxy-assisted sol-gel synthesis requires inexpensive precursors (i.e metal salts), with no need for controlling the pH or temperature of the reaction. As salts of different metals can be used simultaneously, epoxy assisted synthesis sol-gel route can be employed to prepared mixed oxide aerogels.
a) As prepared NiO/YSZ monolith and b) calcinated monolith (550 °C in air, dwell time 1h) and reduced (reduced at 550°C in 5% H2 /N2 atmosphere)
After mixing the reagent, gelation occurred in 5 minutes, leading to the formation of a rigid, opaque-green monolith. The gel was left to age for 24h and then washed for 3-5 with ethanol. The wet gel was then dried in an autoclave for 24h in supercritical CO2 for removing the ethanol from pores without cracks formation. The resulting monolith is shown in Figure 1a. The aerogel was then calcinated at 550 °C (dwell time 1h). The calcinated monolith showed considerable shrinkage and a change in colour from green to grey due to the formation of NiO. Figure 2 shows the morphology of the aerogels.
SEM images of monoliths containing 70mol% Ni a) as-prepared b) calcined c) reduced. .SEM images of NiO-YSZ composite monolith containing d) 30 mol% e) 50 mol% f) mol70% Ni.
sol-gel solution can be used also for the deposition of thin films on different substrate for the preparation of anodes materials for SOFC. The anode can be coated with YSZ electrode deposited AA-CVD (aerosol-assisted chemical vapour deposition) to form a dense on porous layers structure.