Preparation of Ni–YSZ thin and thick films on metallic interconnects as cell supports. Applications as anode for SOFC

In this work, we propose the preparation of a duplex anodic layer composed of both a thin (100 nm) and a thick film (10 lm) with Ni–YSZ material. The support of this anode is a metallic substrate, which is the interconnect of the SOFC unit cell. The metallic support limits the temperature of thermal treatment at 800 C to keep a good interconnect mechanical behaviour and to reduce corrosion. We have chosen to elaborate anodic coatings by sol–gel route coupled with dip-coating process, which are low cost techniques and allow working with moderate temperatures. Thin films are obtained by dipping interconnect substrate into a sol, and thick films into an optimized slurry. After thermal treatment at only 800 C, anodic coatings are adherent and homogeneous. Thin films have compact microstructures that confer ceramic protective barrier on metal surface. Further coatings of 10 lm thick are porous and constitute the active anodic material

Hochtemperatur-Festelektrolyt-Brennstoffzelle umfassend einen Verbund aus nanoporoesen Duennschichtelektroden und einem strukturiertem Elektrolyt

WO2003092089 A UPAB: 20031203 NOVELTY - High temperature, solid electrolyte fuel cell with an electrolyte layer between 2 electrode layers is obtained by (i) applying electrolyte particles in a screen printing paste to an unsintered electrolyte and sintering the resultant structure; and (ii) depositing a nanoporous electrode thin film on this structure by sol-gel or MOD (metal organic deposition) process and heat treating the structure. USE - The products are high-temperature, solid electrolyte fuel cells (claimed). ADVANTAGE - These high temperature fuel cells have higher long-term stability, higher current density and lower polarization resistance than usual. They also have a higher specific capacity for given area at the same degree of efficiency and can be produced cost-effectively, as costly and chemically pure materials need be used only on the electrochemically active areas of the boundaries. The structurized electrolyte surface has better adhesion to the electrode layer, which reduces degradation resulting from delamination

Microstructure of Nanocrystalline Yttria-Doped Zirconia Thin Films Obtained by Sol-Gel Processing

Nano- and microcrystalline yttria-stabilized zirconia (YSZ) thin films with a dopant concentration of 8.3±0.3 mol% Y2O3 were prepared with a variation in grain size by two orders of magnitude. A sol–gel-based method with consecutive rapid thermal annealing was applied to fabricate YSZ films, resulting in about 400 nm YSZ on sapphire substrates. The average grain sizes were varied between 5 nm and 0.5 μm by heat treatment in the temperature range of 650°–1350°C for 24 h. High-resolution (HRTEM) and conventional transmission electron microscopy analyses confirmed specimens—irrespective of the thermal treatment—consisting of cubic (c-)ZrO2 grains with nanoscaled tetragonal precipitates coherently embedded in the cubic matrix. Energy-dispersive X-ray spectroscopy and HRTEM on a large number of specimens yielded a homogeneous yttria concentration within the grains and at the grain boundaries with the absence of impurities, i.e. silica at the grain boundaries