Fabrication of a Flat Tubular Segmented‐in‐series Solid Oxide Fuel Cell Using Decalcomania Paper

A flat tubular segmented‐in‐series (SIS) solid oxide fuel cell (SOFC) was fabricated using decalcomania paper. The performance of a two‐cell stack with 4.5‐mm‐wide electrodes was investigated in a temperature range of 650–800 °C. The decalcomania paper allowed fabrication of the SIS‐SOFC on all sides of the flat tubular support and achieve an effective electrode area larger than that obtained using typical SOFC fabrication techniques such as screen printing or slurry coating. SEM observations revealed that each component layer was flat, uniformly thick, and well adherent to adjacent layers. Measured values of open circuit voltages were very close to the theoretical values; confirming that the processing technique utilizing decalcomania paper is suitable for SIS‐SOFC fabrication. The power densities of the two‐cell‐stack were 437.4, 375.6, 324.6, and 257.1 mW cm⁻² at 800, 750, 700 and 650 °C, respectively.     

Evaluation of Low‐Cost Separators for Increased Power Generation in Single Chamber Microbial Fuel Cells with Membrane Electrode Assembly

We compared novel size‐selective separators, namely the textile fabrics of polyphenylene sulfide (PPS) and sulfonated polyphenylene sulfide (S‐PPS), and the nonwoven fabrics of polypropylene80 (PP 80) and PP 100, with commonly used ion exchange separators (Nafion 117 and cation exchange membane‐7000; CMI‐7000) in terms of power generation, oxygen diffusion, and biofilm formation in a single chamber microbial fuel cell. Size‐selective separators exhibited more power generation than ion selective separators. MFC operation with size‐selective separators generated power output ranging 0.407 to 0.591 V (1000 Ω), whereas with Nafion it was 0.272 V. In polarization analysis, S‐PPS resulted in the highest power density of 190 mW/m², whereas it was 24 mW/m² with Nafion‐117. Size selective separators showed similar or higher proton conductivity than Nafion 117. Oxygen mass transfer coefficients of size‐selective separators (K_O = 3.7 ∼ 7.5 × 10⁻⁵) were lower or similar to Nafion (K_O = 7.5 × 10⁻⁵). Fourier‐transform infrared spectroscopy and scanning electron microscopy analysis revealed that all separators (PP80, S‐PPS, and Nafion) contained proteins or carbon chain compounds after 300‐day operation, and however, Nafion 117 seems to be more susceptible to biofouling than the other separators.     

Electrochemical Performance of PrBaCo2O5+δ and Sm0.5Sr0.5CoO3−δ Infiltrated Ce0.9Gd0.1O1.95 Cathodes

Cathodes with PrBaCo₂O_5+δ (PBC) and Sm_0.5Sr_0.5CoO_3−δ (SSC) infiltrated on Ce_0.9Gd_0.1O_1.95 (CGO) backbones are prepared using metal nitrates as precursors and ethanol as wetting agent. Electrochemical impedance spectra (EIS) are measured from cathode/CGO/cathode symmetrical cells in 400–650 °C under humidified air. The results indicate that interfacial area specific resistance (ASR) value decreases and then increases with infiltrate loading and minimum values occur at 50 wt.% loading (relative to sum of infiltrate and backbone) for both PBC and SSC infiltrates. ASR values of PBC infiltrated cathodes are lower than that of corresponding SSC infiltrated cathodes in general, and in particular ASR values as low as 1.36 × 10⁻² and 2.27 × 10⁻² Ω cm² are obtained at 650 °C in air for 50 wt.% PBC and 50 wt.% SSC infiltrated cathodes, respectively. Conductivity values of CGO electrolyte increase with infiltrate loading and agree with the reported values when the loading reaches 50 wt.%.     

Study of the anticorrosive properties of polypyrrole/polyaniline bilayer via electrochemical techniques

In this work, using electrochemical techniques the authors investigated the protective properties of a polypyrrole/polyaniline bilayer as a conductive polymer. A polypyrrole/polyaniline bilayer was deposited on carbon steel substrate by potentiostatic method. The electric capacitance and resistance of the films were monitored with the immersion time in a corrosive solution to investigate the water permeability of the films. Polypyrrole/polyaniline bilayer has a relatively low permeability and good catalytic behavior in passivation of carbon steel in longer periods. The results show that the bilayer has a better anticorrosive behavior compared to homopolymers (polypyrrole and polyaniline).     

Development of copper beam ducts with antechambers for advanced high-current particle storage rings

There has been continuous progress at the High Energy Accelerator Research Organization (KEK) in R&D on vacuum beam ducts adaptable to future high-current particle storage rings. Here we proposed copper beam ducts with antechambers to deal with the severe issues attributed to the high beam currents. The proposed antechamber scheme can withstand intense synchrotron radiation (SR), provide a beam duct with low beam impedance, and effectively reduce the electron cloud effect (ECE) in positron/proton rings. Several trial models were manufactured by a pressing or cold-drawn method, and assembled with electron beam welding. Special vacuum components, such as connection flanges, distributed pumps, and gate valves, were customized for the beam ducts. TiN coating on the inner surface of the beam duct was also investigated as a mitigating measure for the ECE. Trial models of the copper beam ducts were installed into the KEK B-factory (KEKB), and their performances were evaluated using real positron and electron beams.     

A new approach to the solution of electromagnetic problems with the impedance method

We propose a new approach based on the use of interpolation which provides a significant increase in the accuracy of electric potential calculation using the impedance method. In a rectangular three-dimensional grid, we use a first order interpolation function to describe the distribution of electric potential within each voxel of the mesh. The electric field obtained analytically from this function is used as a solution of the continuity equation applied to each node of the mesh. The system of node equations is then solved to obtain the potential distribution. The obtained results show that this technique provides better accuracy than the conventional impedance method. This approach is exemplified in this article in problems involving high dielectric constant and low conductivity media similar to biological materials.     

High frequency response to the impedance complex properties of Nb-doped CaCu3Ti4O12 electroceramics

Impedance analyses was performed on undoped and Nb-doped CaCu₃Ti₄O₁₂ (CaCu₃Ti_4−xNb_xO_12+x/2; x = 0, 0.01, 0.03, 0.05, 0.1) to investigate their electrical properties. The pellet samples were prepared using the solid state reaction method. Silver electrode was deposited on both pellets’ surfaces for electrical measurement. The thermally etched samples showed tiny bumped domains within the grains. The existence of both domain and grain boundaries are believed to strongly influence the dielectric constant of CaCu₃Ti₄O₁₂ (CCTO). Undoped CCTO showed two arcs of impedance complex plane while Nb-doped samples have three arcs. Each arc represents the constituent elements of the CCTO. The highest frequency arc is evidence that CCTO consists of conductive domains which measure about 1 Ω and are insulated by two types of barriers, i.e. domain boundary and grain boundary.     

Influence of morphology on the behaviour of electrodes in a proton-conducting Solid Oxide Fuel Cell

SrCe_0.95Yb_0.05O₃ (SCY) and related materials are under consideration as a proton conductors for Solid Oxide Fuel Cell (SOFC) electrolytes. Sintered pellets of SCY are used to perform impedance spectroscopy (IS) studies and fuel cell tests on cells with Pt electrodes of two different morphologies. Electrodes are applied to the SCY pellets by two routes: either by firing on a layer of Pt paint (denoted electrode P) or by magnetron sputtering (electrode S). In impedance spectra recorded over a wide temperature range under humidified hydrogen, in symmetrical cell conditions, cells with S electrodes give rise to a much smaller low frequency impedance feature than the cells with P electrodes. This is tentatively attributed to faster diffusion-related processes taking place at the S electrodes. The behaviour of working fuel cells with S and P electrode morphologies is evaluated in terms of maximum power output and Area Specific Resistance in two-atmosphere tests. The fuel cell anode with the S morphology results in superior fuel cell performance, in agreement with the impedance study. The influence of the two different electrode morphologies on the behaviour of the cells is discussed with reference to their morphology, as determined by SEM and AFM.     

Composition and behaviour of cerium films on galvanised steel

The composition and corrosion performance of galvanised steel treated by immersion in cerium nitrate solution was investigated by electrochemical techniques and surface analysis. The surface film consists of a mixture of Ce(III) and Ce(IV) compounds, being very rich in Ce(III) in the first instants of the deposition process and becoming gradually enriched in the more oxidised form, Ce(IV). The presence of this film on the surface hinders the corrosion reaction by reducing the rate of both the cathodic and the anodic reactions. The film becomes thicker but more uneven when the time of film growth increases, with the development of defects in the film, which in contact with electrolyte behaves anodic with respect to the covered areas of the surface. These thicker films have revealed lower resistance to corrosion initiation.     

Protective YSZ-based thin films deposited by RF magnetron sputtering

Protective Zr(Y)O_2−δ-based films sputter-deposited onto apatite-type lanthanum silicate ceramics were appraised for potential applications in solid oxide fuel cells with silicate-based solid electrolytes, where the performance may suffer from surface decomposition processes in reducing atmospheres. Dense and crystalline coatings were deposited using radio-frequency magnetron sputtering from an yttria-stabilized zirconia target. On the basis of microstructural analysis and profile measurements, a sputtering power of 300 W was selected in order to achieve deposition rates in the range 0.50-0.75 μm/h. The surface morphology studies using an atomic force microscope revealed typical film structures with small (<50 nm) grains. The polarization of model electrochemical cells with cermet anodes comprising Ni, yttria-stabilized zirconia and Ce_0.8Gd_0.2O_2−δ (50:30:20 wt.%), deposited onto the protective zirconia films, was found quite similar to that of copper-zirconia cermets without interlayers, suggesting that the electrochemical reaction is essentially governed by the oxygen anion transfer from zirconia phase and/or hydrogen oxidation in the vicinity of zirconia film surface.