Papers by Keyword: Aqueous Tape Casting

Abstract: Nickel oxide/yttrium stabilized zirconia (NiO/8YSZ) anodes with different amounts of pore formers for anode used for solid oxide fuel cell have been prepared by aqueous tape casting technique. The zeta potential of NiO/8YSZ aqueous suspensions with and without dispersants was characterized. Moreover, the viscosity of NiO/8YSZ aqueous suspensions with different amount of dispersants and pore formers were studied by the concentric cylindrical rotational viscometer. The microstructures of the anode with different amounts of pore formers were also studied by SEM. The electrochemical performance of the single cell with different amounts of pore formers (modified by 0.8 wt% of polyvinyl pyrrolidone (PVP) over graphite) was evaluated between 700 and 800 °C with hydrogen as the fuel and air as the oxidant. It was observed that the maximum power density of the single cell with the optimum amount of graphite content (20wt%) measured was over 0.8 Wcm-2 at 800 °C and the area specific resistance value was as low as 0.79Ωcm2. The study allowed identifying optimum amount of graphite modified by PVP as the most promising pore formers for the production of supporting anodes prepared by aqueous tape casting for intermediate temperature solid oxide fuel cell application.

Abstract: In the last years many efforts have been spent to develop colloidal processes that use water instead of organic solvents. The aim of this study was to develop aqueous tape casting systems to produce zirconia tapes. Different types of binder were tested. Rheological properties of the slurries were measured at room temperature. The slurries were cast on a PET carrier with/without a silicone-based coating. Interactions between the slurry and the polymeric substrate were evaluated. It was found that an acrylic binder is more appropriate for colloidal processing. The acrylic-based suspensions showed a pseudoplastic behavior and remained stable after hours. Tapes with thicknesses between 90 and 200 µm were produced. Optimized tapes showed smooth and homogeneous surfaces and adequate plasticity.

Abstract: Aqueous tape casting process was used to prepare the thin cordierite sheets, the influences of dispersant (PAAS), the rate of plasticizer (PEG),and binder (PVA),content (R) and drying temperature on the tape casting process were investigated, the sintering character of the sheets were studied after drying. It was showed that when the content of PAAS was 1wt%, the slurries were stable uniform and the shear thinning was reversible. The green sheets with the thickness of 177μm showed good flexibility, lubricious surface and compact microstructure when R was 0.7 and the drying temperature was 25°C. A compact α-cordierite sheet was obtained at 1000°Csintering for 2h.

Abstract: Nickel oxide/yttrium stabilized zirconia (NiO/8YSZ) anodes with different amounts of pore formers for anode used for solid oxide fuel cell have been prepared by aqueous tape casting technique. The zeta potential of NiO/8YSZ aqueous suspensions with and without dispersants was characterized. Moreover, the viscosity of NiO/8YSZ aqueous suspensions with different amount of dispersants and pore formers were studied by the concentric cylindrical rotational viscometer. The microstructures of the anode with different amounts of pore formers were also studied by SEM. The electrochemical performance of the single cell with different amounts of pore formers( modified by 0.8 wt% of polyvinyl pyrrolidone (PVP) over graphite) was evaluated between 700 and 800 °C with hydrogen as the fuel and air as the oxidant. It was observed that the maximum power density of the single cell with the optimum amount of graphite content (20wt%) measured was over 0.8 Wcm-2 at 800 °C and the area specific resistance value was as low as 0.79Ωcm2. The study allowed identifying optimum amount of graphite modified by PVP as the most promising pore formers for the production of supporting anodes prepared by aqueous tape casting for intermediate temperature solid oxide fuel cell application.

Abstract: Green tapes were prepared by aqueous tape-casting method with binders of polyvinyl alcohol, styrene-acrylate emulsion and the mixed binders, respectively. Effects of solid content and binders on viscosity of the slurry were investigated by digital rotary viscosimeter. Results show that solid content should be lower than 60wt % with the binder of PVA; solid content could achieve the maximum 73wt% by tape-casting using emulsion as binder. Furthermore, slurry with solid content up to 75wt % had been successfully prepared by tape-casting using mixed binders. Mixed binders are promising additives to produce high solid content green tapes with smooth surface, adequate strength and very good flexibility.

Abstract: Aqueous tape casting was developed to fabricate YSZ films using a cobinder. The processing parameters such as pH value, dispersant content, and binder type and content on the quality of YSZ films were investigated and optimized. The results show that at pH = ~ 9.6, the YSZ suspensions with 0.8wt% of the dispersant PAA have a good stability. The degree of pseudo-plastic and viscosity of slurry using different binders increased with the increasing of PVA content, in contrast, the degree of pseudo-plastic and viscosity decreased with the increasing of B1070 content. The density and drying shrinkage of YSZ green tape are tightly related to the different binders. The sintered density of YSZ film increased as the density of green tape increased. The green tape using PVA (30wt %) +B1070 (70wt %) cobinders was sintered at 1400 °C for 2 hours. The films of YSZ with 98.5% of theoretical density have been obtained.

Abstract: Sr0.7Ca0.3TiO3 (SCT) substrates were prepared through aqueous tape casting. Properties of SCT slurries with and without ammonium polyacrylate (NH4PAA) dispersant were characterized by zeta potential. The zeta potential measurement result shows that the isoelectric point (IEP) of the powder changed obviously with the addition of the dispersant. The optimum pH value of the slurry is in the range of 9-10. The rheological test result indicates that the proper content of the dispersant is between 0.6 and 0.8 wt%. The effect of different plasticizer/binder ratio (R) on the properties of the green tapes was investigated. For 56 wt% solid loading, the tensile strength of the green tape reached 2.02 MPa and the breaking elongation rate was about 8%. SEM micrographs show that the microstructure of the green tapes is homogeneous and the microstructure of the sintered tapes is dense.

Abstract: Semiconducting barium titanate powderss with an average particle size less than 40 nm were used for tape casting. Green tapes with a thickness of 100-500 μm were tape-cast from aqueous slurry of barium titanate powders using polyvinyl alcohol (PVA) as binder and polyelectrolyte ammonium salt as dispersant. The solid loading, viscosity and rheological properties of the ceramic slurries were investigated. Slurries with low viscosity were obtained when the concentration of dispersant was 1.5-2.0 wt% (based on ceramic powders weight) with fixed 75 wt% solid loading. The highest solid loading and optimum dispersion were determined through the proper viscosity to cast. Microstructure and PTC effect of the ceramic chips were studied as a function of firing temperature. Yttrium ions were homogeneously diffused into barium lattices at a low temperature of 1240 °C, and fine-grained PTC ceramics with grain size of 1-2 μm were developed successfully. These results can be explained by the higher rate of reactivity of finer powders and stable behavior of the suspension.

Abstract: In this paper, the sintering behavior of Ni/YSZ anode and YSZ electrolytes fabricated by aqueous tape casting were studied. This study involved tape casing of Ni/YSZ (8 mol% Y2O3 stabilized ZrO2) anode, and co-sintering of anode supports and electrolytes. At last, thickness of 140 mm (after sintering) with uniform microstructure and ~30% porosity anode and thickness of ~10 0m (after sintering) with high density (> 95%) and electrolyte were achieved.

Abstract: Well-dispersed SiO2 slurry with high solid content for aqueous tape casting was obtained by selecting the appropriate dispersant, binder, plasticizer and other additives. However, it is difficult to prepare well-dispersed CNTs/SiO2 slurry because CNTs tend to aggregation and the bulk density disparity of CNTs and SiO2 is obvious. In addition, the contradiction between removing organic additives and retaining the properties of CNTs should be considered. Some methods are provided to solve the as-mentioned difficulties.