Inkjet printing infiltration of Ni-Gd:CeO2 anodes for low temperature solid oxide fuel cells.

ABSTRACT: The effect of inkjet printing infiltration of Gd0.1Ce0.9O2-x in NiO-Gd0.1Ce0.9O2-x anodes on the performance of symmetrical and button cells was investigated. The anodes were fabricated by inkjet printing of suspension and sol inks. Symmetrical cells were produced from composite suspension inks on Gd0.1Ce0.9O2-x electrolyte. As-prepared scaffolds were infiltrated with Gd0.1Ce0.9O2 ink. Increasing the number of infiltration steps led to formation of "nano-decoration" on pre-sintered anodes. High resolution SEM analysis was employed for micro-structural characterization revealing formation of fine anode sub-structure with nanoparticle size varying in the range of 50-200 nm. EIS tests were conducted on symmetrical cells in 4% hydrogen/argon gas flow. The measurements showed substantial reduction of the activation polarization as a function of the number of infiltrations. The effect was assigned to the extension of the triple phase boundary. The i-V testing of a reference (NiO-8 mol% Y2O3 stabilized ZrO2/NiO-Gd0.1Ce0.9O2-x /Gd0.1Ce0.9O2-x /Gd0.1Ce0.9O2-x -La0.6Sr0.4Co0.2Fe0.8O3-δ ) cell and an identical cell with infiltrated anode revealed ~2.5 times improvement in the maximum output power at 600 °C which corresponded with the reduction of the polarization resistance of the symmetrical cells at the same temperature (2.8 times). This study demonstrated the potential of inkjet printing technology as an infiltration tool for cost effective commercial SOFC processing.

Infiltration of commercially available, anode supported SOFC's via inkjet printing.

Commercially available anode supported solid oxide fuel cells (NiO-8YSZ/8YSZ/LSCF- 20 mm in diameter) were anode infiltrated with gadolinium doped ceria (CGO) using a scalable drop-on-demand inkjet printing process. Cells were infiltrated with two different precursor solutions-water based or propionic acid based. The saturation limit of the 0.5 µm thick anode supports sintered at 1400 °C was found to be approximately 1wt%. No significant enhancement in power output was recorded at practical voltage levels. Microstructural characterisation was carried out after electrochemical performance testing using high resolution scanning electron microscopy. This work demonstrates that despite the feasibility of achieving CGO nanoparticle infiltration into thick, commercial SOFC anodes with a simple, low-cost and industrially scalable procedure other loss mechanisms were dominant. Infiltration of model symmetric anode cells with the propionic acid based ink demonstrated that significant reductions in polarisation resistance were possible.

Performance optimization of LSCF/Gd:CeO2 composite cathodes via single-step inkjet printing infiltration.

ABSTRACT: The effect of solid oxide fuel cell cathode microstructure modification on its electrochemical activity is investigated. Inkjet printing infiltration was used to develop a nano-decoration pattern on the composite cathode scaffolds. Two types of composite La0.6Sr0.4Co0.2Fe0.8O3-δ:Ce0.9Gd0.1O1.9 cathodes with different volume ratios (60:40 and 40:60 vol%) were fabricated using inkjet printing of suspension inks. The electrodes were altered by single-step inkjet printing infiltration of ethanol-based Ce0.9Gd0.1O1.9 ink. After heat treatments in air at 550 °C the cathodes' surfaces were shown to be nano-decorated with Ce0.9Gd0.1O1.9 particles (~20-120 nm in size) dispersed uniformly onto the electrode scaffold. The nano-engineered microstructure enhanced the active triple phase boundary of the electrode and promoted the surface exchange reaction of oxygen. Electrochemical impedance tests conducted on symmetrical cells showed a reduction in the polarization resistance of between 1.3 and 2.9 times. The effect was found to be more pronounced in the 60:40 vol% composite cathodes. Ageing of infiltrated electrodes up to 60 h in air revealed enhanced stability of gadolinium doped ceria nanoparticles decorated electrodes ascribed to the suppression of SrO surface segregation. This work demonstrated that single-step inkjet printing infiltration can produce reproducible performance enhancements and thus offers a cost-effective route for commercial solid oxide fuel cell infiltration processing.

Superconducting-magnetic heterostructures: a method of decreasing AC losses and improving critical current density in multifilamentary conductors.

Magnetic materials can help to improve the performance of practical superconductors on the macroscale/microscale as magnetic diverters and also on the nanoscale as effective pinning centres. It has been established by numerical modelling that magnetic shielding of the filaments reduces AC losses in self-field conditions due to decoupling of the filaments and, at the same time, it increases the critical current of the composite. This effect is especially beneficial for coated conductors, in which the anisotropic properties of the superconductor are amplified by the conductor architecture. However, ferromagnetic coatings are often chemically incompatible with YBa(2)Cu(3)O(7) and (Pb,Bi)(2)Sr(2)Ca(2)Cu(3)O(9) conductors, and buffer layers have to be used. In contrast, in MgB(2) conductors an iron matrix may remain in direct contact with the superconducting core. The application of superconducting-magnetic heterostructures requires consideration of the thermal and electromagnetic stability of the superconducting materials used. On one hand, magnetic materials reduce the critical current gradient across the individual filaments but, on the other hand, they often reduce the thermal conductivity between the superconducting core and the cryogen, which may cause destruction of the conductor in the event of thermal instability. A possible nanoscale method of improving the critical current density of superconducting conductors is the introduction of sub-micron magnetic pinning centres. However, the volumetric density and chemical compatibility of magnetic inclusions has to be controlled to avoid suppression of the superconducting properties.