Electrochromic thin films prepared by sol–gel process

New methods are shown for lower temperature preparation of amorphous tungsten oxide thin film and preparation of crystalline iridium oxide thin film by sol–gel process using metal chloride as the starting materials and ethanol as a solvent. These electrochromic materials were combined with gel solid electrolyte, and preparation of fully solid-state electrochromic display (ECD) was made. The transmittance of the ECD could be made to change by 35% by applying a voltage of 3 V for 0.2 sec.     

Fabrication of micro-tubular solid oxide fuel cells with a single-grain-thick yttria stabilized zirconia electrolyte

This study discusses the fabrication and electrochemical performance of micro-tubular solid oxide fuel cells (SOFCs) with an electrolyte consisting a single-grain-thick yttria stabilized zirconia (YSZ) layer. It is found that a uniform coating of an electrolyte slurry and controlled shrinkage of the supported tube leads to a dense, crack-free, single-grain-thick (less than 1 μm) electrolyte on a porous anode tube. The SOFC has a power density of 0.39 W cm⁻² at an operating temperature as low as 600 °C, with YSZ and nickel/YSZ for the electrolyte and anode, respectively. An examination is made of the effect of hydrogen fuel flow rate and shown that a higher flow rate leads to better cell performance. Hence a YSZ cell can be used for low-temperature SOFC systems below 600 °C, simply by optimizing the cell structure and operating conditions.     

Quantitative analysis of oxygen-containing species adsorbed on the Pt surface of a polymer electrolyte fuel cell membrane electrode assembly electrode using stripping voltammetry

The quantity of oxygen-containing species adsorbed on Pt surface of a single-cell polymer electrolyte fuel cell membrane electrode assembly (PEFC MEA) in the gas-phase system was measured by stripping voltammetry (SV), of which the adsorbed amount is considered in terms of the quantity of electric charge required for stripping. The effect of different experimental parameters on the adsorption quantity was analyzed and an optimum condition for applying SV to a PEFC MEA electrode was then suggested. The electric charge required for stripping was observed to be linearly proportional to the potential and arose from 0.7 V vs. RHE. The adsorption amount of oxygen-containing species for the PEFC MEA at a cell temperature of 60 °C was 384 μC cm⁻²-Pt at a potential of 1.0 V vs. RHE. More importantly, considering the effect of O₂ partial pressure on the adsorption in the gas-phase PEFC MEAs, water is suggested to be the main source of the oxygen in adsorbed oxygen-containing species. The present method is well applicable to quantitative studies of the oxygen-containing species adsorbed on electrodes of PEFC MEAs.     

Influence of inclination angle,attack angle,and arrangement of rectangular vortex generators on heat transfer performance

We have studied the enhancement of heat transfer by vortex generators. Experiments were performed on rectangular‐type vortex generators mounted on a parallel‐plate heater, and the heat transfer coefficient of the heater surface and pressure drop in the duct were measured. These measurements indicated that a rectangular vortex generator (called a double‐inclined winglet), with inclination angle of the vortex generator surface to the heater surface (β) at 60°, and the attack angle to the flow direction (γ) at 45°, maximizes the local Nusselt number of the heater surface. It was also found that a group of double‐inclined winglets has an optimal arrangement in a winglet array, longitudinal pitch and transverse pitch, that maximizes the ratio [Colburn's dimensionless heat transfer coefficient J_H]/[friction factor f]. The results of numerical calculations showed that the double‐inclined winglet was superior to the conventional rectangular vortex generator in heat transfer. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(3): 253–267, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10089     

Isolation and characterization of an alkaliphilic bacterium utilizing pyrene as a carbon source

Alkaliphilic Mycobacterium sp. strain MHP-1, which can grow on pyrene as a sole carbon and energy source, was isolated from a soil sample. At the optimum pH for growth (pH 9), about 50% of pyrene (final concentration at 0.1% [w/v]) was degraded during 7 d of incubation, and 4,5-phenanthrenedioic acid, 4-phenanthroic acid and phthalic acid were identified as metabolic intermediates. Strain MHP-1 was found to possess aromatic-ring dioxygenase genes, which are highly homologous to the known nidAB genes from pyrene-degrading mycobacteria.     

Analysis of the photofading of phenylazo-aniline and phenylazo-pyridone disperse dyes on poly(ethylene terephthalate) substrate using the semiempirical molecular orbital PM5 method

The photofading characteristics of six monoazo disperse dyes on polyester fabric upon exposure to a carbon arc in air were analyzed in terms of the reactivity (k₀) towards ¹O₂ and the photosensitivity (f). The photochemical properties of the dyes were estimated by catalytic fading in mixture dyeings of two yellow (pyridone-azo and quinolone-azo) dyes. The k₀ ratios for the componential dyes in the 1:1 mixture dyeings varied with the partner yellow dye, implying that they depend upon the f values and the concentrations of the component dyes as well as the superposition of absorption spectra, and the changes in their concentration, even in the initial stages of fading. The relative k₀ values, as estimated by the sum of the electrophilic frontier densities using the PM5 method were demonstrated experimentally, while taking the influencing factors into consideration. The assumption that the rates of oxidative fading on PET were proportional to the product of two factors of k₀ and f was confirmed as reasonable based on the fading behavior upon exposure to a carbon arc in air of eight disperse azo dyes with a wide range of two factors.     

Performance improvement in direct methanol fuel cells using a highly porous corrosion-resisting stainless steel flow field

Power generation with direct methanol fuel cell (DMFC) systems requires only simple equipment, and has the important advantage of using a liquid fuel with higher energy density and easier handling characteristics than hydrogen. However, the power output of DMFC is lower than hydrogen fuel cells. To improve the power output of DMFC it is very important to reduce diffusion polarization at higher current density conditions. This research used a corrosion-resisting type porous stainless steel developed based on the technology for metal–hydride battery electrodes in the separator flow fields for reactants and products in a single cell DMFC and analyzed its influence on performance characteristics.     

Formation of Ni-aluminide Coating Containing Hf by Molten-Salt Electrodeposition and Cyclic-Oxidation Resistance

The formation of a coating layer consisting of Ni-aluminide containing Hf on a Ni–10at.%Cr–8at.%Al alloy substrate was attempted by the electrodeposition of Hf, Ni, and Al. The cyclic-oxidation resistance for the alloy covered with this coating was then evaluated in air at 1,423 K. Ni was deposited by aqueous solution electrolysis. Hf and Al were deposited by molten-salt electrolysis. For the sample first treated with the Hf-deposition, subsequently treated with the Ni-deposition, followed by Al-deposition, a coating consisting of Ni₂Al₃ of about 40-μm thickness was uniformly formed on the alloy. At the center region of this coating, a Hf-concentration layer was formed. The cyclic-oxidation test showed that, for the untreated sample and the sample with only Ni and Al depositions, a mass reduction due to spallation of a scale took place during the initial oxidation period. On the contrary, for the sample with Hf, Ni, and Al depositions, a mass reduction due to spallation of a scale scarcely took place. The cross-sectional observation using SEM showed that, for the sample with Hf, Ni, and Al depositions after the oxidation test, an adhesive scale having a spiked shape was formed. This scale mainly consisted of α-Al₂O₃, and contained HfO₂ particles. It was postulated that, for this sample, the Hf in the Hf-concentration layer diffused into the surface region of the Ni-aluminide layer, contributing to improvement in the exfoliation resistance of the scale.     

DNA-lipid complexes carrying carbazole and triphenylamine moieties: Synthesis, and chiroptical and photoelectronic properties

Novel DNA-lipid complexes carrying carbazole and triphenylamine moieties were prepared by substituting the sodium counter cation with cationic amphiphilic lipids, namely lipid(Cz) and lipid(TPA), in which the actual mole ratios of phosphate to lipid were 1:1.10 and 1:0.83, respectively. The DNA-lipid(Cz) and DNA-lipid(TPA) complexes were soluble in common organic solvents including CHCl₃, CH₂Cl₂, methanol and ethanol, while insoluble in THF, toluene, and aqueous solutions. CD spectroscopy revealed that the DNA-lipid complexes took a predominantly double helical structure in CHCl₃ and methanol and that the helical structure was fairly stable against heating. Solutions of DNA-lipid(Cz) and DNA-lipid(TPA) complexes emitted fluorescence in 5.7 and 76.4% quantum yields, which were higher than those of the corresponding lipid(Cz) and lipid(TPA) (4.4 and 55.3%). The cyclic voltammograms of the complexes indicated that the oxidation potentials of DNA-lipid(Cz) and DNA-lipid(TPA) were 0.95 and 0.85 V, respectively. The onset temperatures of weight loss of the DNA-lipid complexes were both 220 °C according to TGA in air.