Fabrication Of Anode Functional Layer And Electrolyte For Apatite Lanthanum Silicate SOFCs

Solid oxide fuel cells?SOFCs?is a novel energy conversion device that directly converts the chemical energy of fuel into electrical energy through an electrochemical reaction.This device has attracted attention due to its all-solid structure and high utilization efficiency.However,since the operating temperature of traditional SOFCs is generally above 800°C,this working conditions impose high requirements on the thermodynamic stability and chemical stability of the SOFCs,its package and connection components,and increase manufacturing cost.Therefore,the intermediate/low temperature SOFC is a research focus in recent years.In this paper,electrolyte was prepared with apatite-type La₁₀Si_5.8Mg_0.2O_26.8?MDLS?which has good conductivity at intermediate/low temperature,and the resistance of the electrolyte was reduced by thinning the electrolyte layer.It is difficult to prepare a dense electrolyte film on an anode substrate with a porosity of more than 25%.So we introduce an anode functional layer?AFL?to achieve the purpose of reducing the anode pore size and increasing the three-phase interface.On the other hand,the surface roughness of the anode functional layer directly affects the density of the electrolyte film,so we introduce different flattening methods to improve the flatness of the functional layer.In this paper,Ni O/MDLS anode with porous structure was manufactured and the anode functional layer was prepared on the anode substrate powder by screen printing.Screen printing paste was made of NiO powder with particle size of 30nm and La₁₀Si_5.8Mg_0.2O_26.8powder.The ratio of NiO and La₁₀Si_5.8Mg_0.2O_26.8 powder is 6:4.Dissolved in the appropriate amount of terpineol,and then add different amounts of ethyl cellulose as a binder,the paste is prepared.Making the AFL dry after printed different layer numbers of slurry,then sintering at1050°C for 2h,we completed the preparation of AFL.This thesis discusses the effects of the content of ethyl cellulose and screen printing layer numbers on the anode functional layer.The SEM was used to observe the surface/cross sectional morphology and thickness of the functional layer.The XRD was used to analyze the functional layer phase and the laser confocal microscope was used to measure the roughness of the functional layer.The surface porosity is measured by the image-analysis method.The experimental results show that when10wt.%-12.5wt.%ethyl cellulose is used,the surface of the functional layer with micro-nano pores has no cracks and large pores?the pore size>2?m?,and the functional layer porosity is between 14%-16%.The three-layers anode functional layer has the highest flatness,and its thickness is about 14?m.In this paper,the La₁₀Si_5.8Mg_0.2O_26.8 electrolyte film was prepared on the anode substrate/AFL by magnetron sputtering.Without applying a temperature field,the sputtering power was 80W.The sputtering pressure,sputtering time,and annealing parameters were adjusted to prepare a dense electrolyte thin film.By using SEM,XRD,EPMA,etc.,the surface/cross-sectional morphology,thickness,phase,and composition of the electrolyte films were analyzed.The experimental results show that an amorphous thin film was obtained after sputtering and was annealed at 1100°C to transform into crystalline state.The sputtering gas pressure is in the range of 0.5 Pa-1.9 Pa and 0.9 Pa is the best sputtering gas pressure.Sputtered at 0.9 Pa and then annealed at 1100?,a pure apatite phase electrolyte film was prepared.The films sputtered at the other pressures contain a small amount of La₂SiO₅ impure phase.