Yoshio Matsuzaki

The poisoning effect of sulfur-containing impurity gas on a SOFC anode: Part I. Dependence on temperature, time, and impurity concentration

An aqueous suspending agent solution or vehicle useful for suspension polymerization of a styrene-monomer such as styrene as well as derivatives of it and also mixtures with it to produce styrene-polymers. Also included is a suspension polymerization batch, as well as an improvement in the method, for the suspension polymerization of a styrene-monomer.

Evaluation and modeling of performance of anode-supported solid oxide fuel cell

For an anode-supported planar SOFC, a single-unit with double channels was modeled for a counter-flow pattern, and the concentration polarization at the anode was estimated. The flow phenomena were simulated using the finite volume method and the distribution of the gaseous species was calculated. In the model, it was assumed that the gas flow in the porous anode is governed by Darcys Law, and the reactant species are transported to the electrolyte/anode interface mainly by diffusion in a multicomponent mixture system. For binary H2–H2O and CO–CO2 systems, the calculated concentration polarization was found comparable to the experimental results. As an example for a multicomponent system, a model using steam-reformed methane as a fuel was employed to simulate the concentration polarization at a high fuel utilization. From the simulated results, it was evident that the shift reaction effectively reduces the concentration polarization when the fuel utilization is high.

Electrochemical properties of a SOFC cathode in contact with a chromium-containing alloy separator

Abstract Substrate-type solid oxide fuel cells (SOFCs) can reduce the operating temperature of SOFCs to enable alloys to be used as separators. When chromium-forming alloys are used as the separators, however, the performance of SOFC cathodes degrades rapidly. The degradation of a porous La 0.6 Sr 0.4 MnO 3+ δ (LSM)/YSZ electrode in contact with the alloy current-collector has been investigated using the frequency dispersion diagram of the complex impedance of the electrode. The equivalent circuit analysis based on a Randles-type equivalent circuit made clear that the Cr 2 O 3 deposition at the interface between the LSM and the YSZ electrolyte causes an increase in both diffusion and charge-transfer resistances.

Electrochemical properties of reduced-temperature SOFCs with mixed ionic-electronic conductors in electrodes and/or interlayers

Abstract We have investigated the electrochemical properties of two types of reduced-temperature solid oxide fuel cells (SOFCs) in which the mixed ionic–electronic conductors are used to improve their performances. Electrolyte-supported cells, in which doped LaGaO 3 strengthened by Al 2 O 3 dispersion is used as the electrolyte, were prepared and tested. Samaria-doped ceria (SDC) interlayers of 0.3-μm thickness were fired onto both surfaces of the electrolyte of 0.2-mm thickness at 1523 K, before firing the Ni–Sm 0.1 Ce 0.9 O 1.95 –(CeO 2 ) 0.1 [(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 ] 0.9 (Ni–SDC–CeYSZ) (10 mol% ceria-doped yttria-stabilized zirconia [YSZ]) cermet anode at 1723 K and La 0.7 Sr 0.3 Co 0.2 Fe 0.8 O 3 –Sm 0.2 Ce 0.8 O 1.9 (LSCF–SDC) composite cathode at 1373 K. The cells have a nominal size of 60×60 mm 2 with an effective electrode area of 4 cm 2 . The single cell thus prepared showed a high power density of 0.67 W cm −2 at 1073 K and long-term stability during the operation time of 1000 h. Anode-supported cells with a thin YSZ electrolyte film approximately 30 μm thick were also prepared by co-sintering of screen-printed YSZ paste on a compacted anode substrate. The cells have a nominal size of 50×50 mm 2 with an effective electrode area of 4 cm 2 . The single cell with the LSCF–SDC composite cathode having SDC interlayer showed the maximum power density of 0.648 W cm −2 at 1023 K. The bilayer cathode also showed high resistance against degradation by Cr-poisoning.

Relationship between the steady-state polarization of the SOFC air electrode, La0.6Sr0.4MnO3+δ/YSZ, and its complex impedance measured at the equilibrium potential

Abstract By making clear the relationship between the cathodic limiting current density and R -type Warburg impedance used in the Randles type equivalent circuit, the limiting current density, as well as the exchange current density, of a porous La 0.6 Sr 0.4 MnO 3+ δ /YSZ electrode has been successfully estimated from a complex impedance spectrum measured at an equilibrium potential. A steady-state polarization calculated from these current densities gave a good agreement with the measured one, which indicates that, even at an equilibrium potential, the limiting current density can be obtained with high precision from the complex impedance. Investigation of the exchange and limiting current densities of the electrode under an oxygen partial pressure, P O 2 , of 0.001–1 atm at 1123–1273 K has derived the formulation for expressing an equation which expresses the P O 2 and temperature dependence of steady-state polarization.

Electrical conductivity and mechanical properties of alumina-dispersed doped lanthanum gallates

Abstract With the aim of increasing the mechanical strength of doped lanthanum gallate ceramics, which can be applied to the electrolyte in solid oxide fuel cells for reduced temperature operation, the effects of alumina dispersion on mechanical and electrical properties were investigated. The thermal expansion coefficient showed no significant changes either with the amount of alumina addition or with the oxygen partial pressure in the atmosphere. The alumina dispersion preferably along grain boundaries was found to be effective in retarding the grain growth of lanthanum gallate, which greatly increased the bending strength at both room temperature and 800°C. The sample with 2 wt% of alumina addition showed electrical conductivity comparable to that of the perovskite matrix alone at 800°C and higher conductivity at temperatures lower than 750°C. At additions of ≥5 wt%, the alumina grains partially blocked the transport of oxide ions between the lanthanum gallate grains, which decreased the ionic conductivity to unacceptable levels. The optimum alumina addition for the improvement of mechanical properties without altering the thermal expansion coefficient and ionic conductivity was found to be around 2 wt%. A single-cell using the electrolyte sheet with the optimized composition showed a maximum power density of 0.245 W/cm2 at 800°C.

Growth of yttria stabilized zirconia thin films by metallo-organic, ultrasonic spray pyrolysis

Abstract Randomly and preferentially oriented thin films of yttria stabilized zirconia (YSZ) have been prepared on fused quartz substrates by ultrasonic spray pyrolysis using zirconium octylate and yttrium octylate as metallo-organic precursors at a substrate temperature of 873–1023 K. The as-deposited films composed of fine columnar grains were found to be crystalline and transparent with a cubic fluorite structure. With increasing substrate temperature the growth rate and diameter of the columnar grains increased and the crystal habit showed a preferential orientation at the (111) plane.

Photo-excitation effects on pyrolysis of metallo-organic precursors for yttria-stabilized zirconia thin films

Abstract Combination of pyrolysis and vacuum ultraviolet (VUV) photolysis under reduced pressure offered an effective method to prepare yttria-stabilized zirconia (YSZ) thin films from metallo-organic precursors at moderate temperatures. It became clear from IR and XPS analyses that thermal decomposition of metalloorganic precursors was accelerated by VUV excitation. The precursors dip-coated on a fused quartz substrate were found to decompose and crystallize into YSZ thin films as low as 603 K by thermal decomposition assisted by VUV irradiation. Without the VUV irradiation, however, the films were in an amorphous state at this temperature. It was also found that the VUV irradiation was more effective under air flow than under nitrogen flow, which suggests that active oxygen in the gas-phase generated by the VUV irradiation has an important role in the decomposition of the precursors.

Gas Supply Infrastructure

In 2012, Japan imported 87 million tons of LNG or 36.2 % of total worldwide LNG imports of 239 million tons. The main sources, accounting for over 70 % of the total, are Asia-Pacific countries such as Australia, Malaysia, Russia, and Brunei. LNG production is dispersed more widely around the world, making it less exposed to geopolitical risk than oil. LNG can be transported in several ways, such as tank lorries and tank containers, to satellite bases for distribution. Gas pipelines are the primary means in Japan, where there are two kinds of gas pipelines. One is for transport of natural gas produced in domestic gas fields; the other is for transport of city gas produced in LNG terminals to areas of demand. For metering gas consumption at customer sites, there is an increasing need for remote meter reading. Furthermore, it is believed that demand will increase for services that emphasize security and safety or for those facilitating monitoring of senior citizens or those living alone via their gas use. Energy saving is another important consideration. To meet all these expectations, a smart gas meter is being developed.