Study On Preparation And Properties Of LSM Coating On SUS430Alloy Derived From Screen Printing Method

The stainless steel with Cr is most commonly used interconnect materials formedium temperature and low temperature solid oxide fuel cell (SOFC), which has theadvantages of low cost and good workability. However, the poor oxidation resistance athigh temperatures and the Cr caused cathode poisoning impact the long-term stability ofthe SOFC stack, and the surface modification is necessary. In this thesis, theLa0.75Sr0.25MnO3(LSM) coating was prepared on SUS430alloy using screen printingmethod coating to improving high temperature oxidation resistance of metallicinterconnect and inhibit the volatilization of Cr. The preparation process of LSM coatingwas studied and the effect of slurry dispersion, sintering atmosphere and temperature wasalso investigated.1) In this thesis, tri-oleic acid glyceride was used as LSM slurry dispersant with1wt.%,3wt.%,5wt.%content respectively. The SEM morphology of the LSM coatingwas observed, the oxidation kinetics curve and specific area resistance (ASR) weremeasured. The results showed that the LSM coating with3wt.%dispersant sintered well,the LSM particles is clear to observed, the coating is dense and contact with the SUS430matrix closely. The thickness of the LSM coating is about15μM. The sintered LSMcoating was then oxidized in air at800℃for different time, the thickness of LSMcoating with different dispersant content increased, and LSM particles were grown. After1000h oxidation, the weight gain of LSM coating with3wt.%dispersant yield to1.5mg,which was less than that of the coating with1wt.%dispersant. The measured oxidationkinetic constant is1.6867×10-14and the ASR after oxidized at800℃for4×104h wasestimated to be88.99×10-3Ω·cm2for the LSM coating with3wt.%dispersant, whichcould meet the SOFC interconnect request.2) In this thesis, the LSM coating on SUS430alloy was prepared in the atmosphereof N2and N2+H2at900℃respectively, the effect of atmosphere on SEM morphology,phase composition, oxidation kinetics, ASR of LSM coating were studied. The resultsshow that, the LSM coating was dense and no cracking and spalling phenomenon wasobserved. The main phase of the LSM coating was LSM phase and metal matrix phaseafter oxidized in air at800℃for1000h. Compared with the LSM coating sintered underatmosphere of N2, the samples sintered under atmosphere of N2+H2have more uniformLSM particle size and no obviously connected pores. The weight gain of the later treatedunder air at800℃for1000h yield to be1.2mg, the oxidation kinetics constant was9.6946×10-15, the ASR after oxidized at800℃for4×104h was estimated to be36.49× 10Ω·cm2, more less than the value of100×10-3Ω·cm2. The results indicate that N2+H2atmosphere was more conducive to improving the LSM coating on SUS430interconnects.3) In this thesis, the LSM coating was prepared in N2+H2atmosphere at1000℃，theeffect of sintered temperature on SEM morphology, oxidation kinetics, ASR of LSMcoating were studied. The results show that, the LSM particles of the coating sintered at1000℃was large. The same sample was oxidized in air at800℃for1000h, the weightgain was1.9mg, ASR value was higher than100×10-3Ω·cm2, which were all higher thanthat values of the sample sintered ait900℃. The results indicated poor properties ofLSM coating sintered at1000℃.