Application In Preparation Of Solid Oxide Fuel Cells By Slip-casting With Aqueous Slurry

Solid oxide fuel cell（SOFC）is composed of three layers of ceramic components.Lowering the fabrication cost of the ceramic components can push forward thecommercialization of SOFC. Compared to dry process, the wet forming method can improvethe homogeneity of green ceramic body. The wet forming method involves four basic steps:(1)powder synthesis,(2) suspension preparation,(3) consolidation into the desired componentshape,(4) sintering, among which suspension preparation is one of the most critical step.The work presented in this thesis aims to achieve stable slurry to facilitate formingceramic components. The effects of different kinds of dispersant on the surface zeta potentialsof NiO and YSZ (8%Y2O3-stabilized ZrO2) are examined. It is found that the zeta potential ofNiO is opposite to that of YSZ when the anionic or amphoteric dispersant existed. The zetapotentials for both NiO and YSZ are positive when the cationic dispersantpoly(diallyldimethylammonium chloride)(PDAC) is applied. A stable NiO-YSZ-graphiteaqueous slurry was prepared by using PDAC to disperse NiO and YSZ, andpolyvinylpyrrolidone (PVP) to disperse graphite (pore former). Tubular anode supports areprepared by slip-casting technique with the stable slurry and anode-supported SOFCs areprepared with the anode supports. Such a typical SOFC, with a cathode area of0.42cm2,using moist hydrogen (30ml/min) as fuel and ambient air as oxidant, shows a maximumpower density of509mW cm-2at800°C.To achieve higher power, three kinds of nickel oxide are used to prepare cone-shapedSOFCs. The results show that the performance of the SOFC prepared by Australia nickeloxide is the best.To reduce the large ohmic resistance arisen from the long current path of a tubular SOFC,we proposed a new method to collect current at the anode. The tubular SOFC（tube length:5.4cm）employed by the method shows an improvement of74.6%, compared to that withconventional current collection way.To further reduce cost of ceramic forming, we developed a slurry, which use chitosanoligosaccharide and polyvinyl alcohol (PVA) as the dispersant of YSZ in water, to prepareelectrolyte membrane on the surface of anode support by dip-coating. The as prepared cone-shaped SOFC, with a cathode area is1.6cm2, using moist hydrogen (30ml/min) as fuel,shows a maximum power density of424mW cm-2at800°C. FT-IR and zeta analysisindicates that YSZ can’t adsorb chitosan oligosaccharide, so the stability of the slurry ismainly ascribed to PVA.In conclusion, stable aqueous Ni-YSZ-graphite slurry has been prepared and themechanism of slurry stability has been investigated. This work can provide a guide inpreparing stable and cost-effective suspensions for fabricating ceramic components of solidoxide fuel cell.