Preparation Of Rare Earth Modified CuFe₂O₄ Spinel Coating By Screen Printing Method

Solid oxide fuel cell is a new type of power generation device,which has a wide range of application.Interconnector is one of the most important components,which can connect the cathode and anode of a single cell and conduct electrons.With the development and progress of fuel cell technology,Fe-Cr interconnectors have attracted the attention of researchers and been widely used.However,problems such as increased surface resistance and cathodic material toxicity were caused by Cr diffusion in Fe-Cr interconnectors during long-term service at high temperature.At present,researchers mainly prepare protective coatings on the surface of Fe-Cr interconnector to avoid direct contact with O₂ during high temperature service,reduce the diffusion of Cr in the matrix,and effectively reduce the battery performance attenuation caused by the above problems.Among all kinds of protective coatings,spinel coatings have good adhesion to matrix,relatively high-temperature electrical conductivity and the ability to prevent the diffusion of Cr in the interconnector,which has been widely attracted by researchers.Among them,Cu-Fe spinel coating has a better inhibition effect on O₂,and the constituent elements are transition metals,strong electron conduction ability,low raw material cost,respectively.However,after coating is oxidized at high temperature for a long time,there is still the growth of the Cr-containing transition layer,which leads the problem of the working efficiency of the coated sample to decrease.It was found that rare earth modification of the coating could reduce the growth rate of the Cr layer and improve the bonding force between the coating and the alloy interconnectors during the battery service at high temperature.From the point of view of cost,this topic takes low-cost Cu-Fe spinel coating material as the research object,adopts low-cost sol-gel method to prepare rare earth modified CuFe₂O₄spinel powder,and the simple screen printing to prepare coating on SUS430 alloy substrate surface.The effect of rare earth element modification on the microstructure,high temperature oxidation resistance and electrical conductivity of the coating sample were systematically studied,and the effect of rare earth modification was explained.The mechanism of the CuFe₂O₄spinel coated sample is expected to provide theoretical support for exploring the low-cost surface modification of solid oxide fuel cell alloy connectors.The main results are as follows:(1)In the process of preparing rare earth modified CuFe₂O₄ spinel powder by sol-gel method,when the drying temperature of the wet sol is 80?and the drying time is 6 h,a completely dry xerogel can be obtained.When the sintering temperature of xerogel is 800?and the sintering time is 4 h,CuFe₂O₄ spinel powder with higher crystallization degree can be obtained.At the same time,the phase structure and microstructure of CuFe₂O₄ spinel powder under different modification amount of Y and Ce are compared and studied.The optimum modification amount of Y and Ce was 0.03mol/L and 0.04mol/L,respectively.(2)In the process of preparing the rare earth modified CuFe₂O₄ spinel coating by the screen printing,when the CuFe₂O₄ powder in the slurry is 10 g,ethanol is 5 m L,and polyacrylic acid is 2.5 m L,a 200 mesh screen is used to print the SUS430 alloy substrate.The coated sample with a flat surface was obtained by deposition.After the coated sample was dried at 60?for1.5 h,it was sintered in the air at 800?for 3 h to obtain a denser CuFe₂O₄ spinel coating sample.(3)Compared with the oxidation rate constant(3.24×10^-15 g²·cm^-4·s^-1)of Ce-modified coating sample after 168 h oxidation at 800?,the oxidation resistance and conductivity of Y-and Ce-modified samples at high temperature were compared.The Y-modified samples exhibited better oxidation resistance at high temperature(2.99×10^-15 g²·cm^-4·s^-1).At the same time,the ASR of the Y-modified sample was 14.8 m?·cm²,which was lower than that of the Ce-modified sample(15.6 m?·cm²)and the unmodified sample(16.5 m?·cm²).It shows that Y-modified sample has good high temperature conductivity.