Paper-structured catalyst for the steam reforming of biodiesel fuel

Architectonics of the paper-structured catalyst for the application to the biofuel reformer or direct internal reforming SOFC (DIRSOFC) was studied. Inorganic fiber network, “paper”, composed of yttria-stabilized zirconia (YSZ) fiber (Zf), alumina fiber (Af) and inorganic binder (Al₂O₃ sol (As) or ZrO₂ sol (Zs) or CeO₂ sol (Cs)) was prepared by a simple paper-making process. Then, the catalytic activities of the Ni and Ni–MgO loaded papers called “paper-structured catalysts (PSCs)” for the steam reforming of biodiesel fuels (BDFs) were evaluated. Ni–MgO loaded PSC using Cs as an inorganic binder, Ni–MgO/ZfAfCs, exhibited excellent performance over Ru/γAl₂O₃ catalyst beads. Formation of light hydrocarbons, especially C₂H₄, was eliminated and water–gas shift reaction was more promoted compared to the catalyst beads.     

Influence of thermal and flow boundary perturbations on convection heat transfer characteristics: Numerical analysis based on adjoint formulation

A numerical approach based on adjoint formulation of convection heat transfer is proposed to predict the change of heat transfer characteristics for arbitrary thermal and flow boundary perturbations. In order to obtain the adjoint system of the convection heat transfer problem, we formally linearize the governing equations by the perturbation method and then derive the adjoint system for the perturbation system. As a result, it is shown that the numerical solutions of the base and the adjoint problems enable us to predict the changes of heat transfer characteristics, such as the change of total heat transfer rate or the change of temperature at a specific location, when the thermal and flow boundary conditions are perturbed. An application example is presented to demonstrate the proposed method. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(1): 1–12, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10065     

Estimation of flooding in PEMFC gas diffusion layer by differential pressure measurement

The flooding, especially in gas diffusion layer (GDL), is one of the critical issues to put PEMFC to practical use. However, the experimental data of the flooding in GDL is so insufficient that the optimization design related to the water management for GDL has not established. In this study we developed a method to estimate the water saturation, namely the ratio of liquid water to pore volume in GDL. We fabricated a simple interdigitated cell where the supply gas is enforced to flow under rib. This structure enables to estimate the liquid water ratio in GDL by the measurement of differential pressure through the cell. We operated the cell and measured the differential pressure, and succeeded in estimating the water saturation, which changed largely with changing cell operation condition. In addition to this deferential pressure measurement, we measured the ionic resistance in polymer electrolyte membrane by ac impedance method. We evaluated and discussed the influence of the water saturation on cell voltage.     

Thermal boundary condition effects on forced convection heat transfer

We propose a numerical solution of an adjoint problem of forced convection heat transfer to evaluate the mean heat transfer characteristics under arbitrary thermal boundary conditions. Using the numerical solution of the adjoint problem under the Dirichlet condition, which can be computed by slightly modifying a conventional heat transfer code, we obtain an influence function of local surface temperature on total heat transfer. As a result, the total heat transfer for arbitrary surface temperature distributions can be calculated by the influence function. Similarly, using the numerical solution of the adjoint problem under the Neumann condition, we can also obtain an influence function of the local heat flux on the mean surface temperature. The influence functions for a circular cylinder and for an in-line square rod array are presented to illustrate the capability of this method. © 1999 Scripta Technica, Heat Trans Asian Res, 28(3): 227–238, 1999     

Internal gravity wave resonance of thermal convection fields in rectangular cavities with heat‐flux vibration (effects of aspect ratio on the fields)

In this paper the thermal convection field and its resonance phenomena in a rectangular cavity with heat‐flux vibration are numerically examined and the results are compared with those of a square cavity. As in the case of α=1, the critical angular velocity at which the relative amplitude of the midplane Nusselt number α_m has a local maximum agrees very well with the resonance angular velocity of the internal gravity wave ω_r, estimated by the theoretical equation proposed by Thorpe, even when the aspect ratio is α=5 and the Prandtl number is Pr=0.71 for a range of the Rayleigh number Ra. However, α_m has two local maxima for a larger Ra, which is peculiar to the case of larger α. The time variation of sub‐components of the fluctuating component of the midplane Nusselt number shows that the phase at the maximum value of α_m agrees well with that of the sub‐component of velocity for the first resonance angular velocity ω_r. For the other angular velocity ω_r2, the phase of α_m agrees with that of the sub‐component of temperature. Moreover, we found that the boundary angular velocity ω₀ between the first two of the five ω regions, which classify the thermal convection fields against ω, can be expressed by a function of α, Ra, and Pr and that α_m is independent of α and Ra for a relatively wide range of ω/ω₀. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(3): 158– 171, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20149     

Isoprene formation from CO and H2 over CeO2 catalysts

The CO-H₂ reaction over CeO₂ catalysts at around 623 K and 67 kPa forms isoprene with about 20% and 70% selectivities in total and C₅ hydrocarbons, respectively. The formation of dienes may be due to the low and high activity of CeO₂ for alkene and CO hydrogenation, respectively.     

Physicochemical properties of Ba(Zr,Ce)O3-δ-based proton-conducting electrolytes for solid oxide fuel cells in terms of chemical stability and electrochemical performance

To enhance the power generation efficiency of solid oxide fuel cells (SOFCs), the use of proton-conducting solid solutions of doped BaCeO₃ and doped BaZrO₃, with formulas of the Ba(Zr_0.1Ce_0.7Y_0.1X_0.1)O_3-δ (X = Ga, Sc, In, Yb, Gd), was investigated as SOFCs electrolyte materials with respect to both chemical stability and electrical conductivity. Regarding chemical stability, the weight changes of each material were measured under a CO₂ atmosphere in a temperature range of 1200 °C–600 °C.Higher chemical stability was observed for dopant ions with smaller radii. Regarding conductivity, the dependences of the total conductivities on the oxygen partial pressure and temperature were measured in the temperature range of 600 °C–900 °C. In each material, the total conductivity was proportional to the oxygen partial pressure to the 1/4 power at high oxygen partial pressures, as previously observed for accepter-doped proton-conducting perovskite-type oxides. The derived conductivities for each type of charge carrier showed that the hole conductivity increased with the ionic conductivity. Based on the measured data, the leakage current densities were calculated for SOFCs with each of the investigated electrolyte materials and an area-specific resistance of 0.383 Ωcm². BZCYSc showed the minimum leakage current density, with a value of 3.7% of the external current density at 600 °C. Therefore, this study indicates that BZCYSc is the most desirable among the materials investigated for use as SOFCs electrolyte. However, for BZCYSc to be used as SOFCs electrolyte material, a protective layer is needed to ensure its chemical stability.     

FT-IR studies of decarbonylation and recarbonylation of [Pt3(CO)6] 5 2− supported on dehydrated SiO2

Decarbonylation of [Pt₃(CO)₆]₅ on SiO₂ at 373 K produced [Pt₃(t-CO)₃]₅ species, where all the terminal CO remained. Complete decarbonylation at 423 K was not observed, which led to aggregation at 473 K. The interaction of some Pt with SiO₂ inhibited complete recarbonylation to [Pt₃(CO)₆]₅.     

Highly Efficient Water Oxidation Photoanode Made of Surface Modified LaTiO2N Particles

An improved variation of highly active/durable O₂‐evolving LaTiO₂N powder‐based photoelectrode has been fabricated by pre‐cleaning the powder with mild polysulfonic acid and by homogeneous deposition of CoO_x co‐catalyst aided by microwave annealing. The treatment in aqueous solution of poly(4‐styrene sulfonic acid) results in removal of surface LaTiO₂N layers, forming fine pores in the crystallites. The CoO_x co‐catalyst by microwave deposition in Co(NH₃)₆Cl₃/ethylene glycol homogeneously covers the particle surface. The LaTiO₂N powder is fabricated into particle‐transferred electrodes on Ti thin film supported on solid substrate. The modified LaTiO₂N grains on the electrode serve as a highly active O₂‐evolving photoanode achieving 8.9 mA cm^?2 of the photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) in 0.1 m NaOH (pH 13) under solar‐simulator irradiation Airmass 1.5 Global (AM 1.5G). The activity has been much improved, compared with conventional LaTiO₂N treated in mineral acid or with CoO_x deposited by impregnation. The new electrode also exhibits better durability in fixed‐potential chronoamperometric tests under AM 1.5G irradiation.     

Influence of structural organization on tensile properties in mesomorphic isotactic polypropylene

The effects of annealing on the structure and mechanical properties of mesomorphic isotactic polypropylene have been investigated using wide-angle and small-angle X-ray scattering and rheo-optics in addition to tensile tests. Young's modulus of mesomorphic phase was estimated to be 5 GPa using Takayanagi model. The α-crystallitic iPP prepared by annealing the quenched mesomorphic iPP was transparent because of the absence of spherulitic structure. It was found that the mechanical yielding of α-crystallitic iPP is dominated by the plastic flow of crystalline structural units whereas the yield process of α-spherulitic iPP quenched at 80 °C is caused by the fracture or fragmentation of crystalline structural units.