Design of High-Quality Pt–CeO2 Composite Anodes Supported by Carbon Black for Direct Methanol Fuel Cell Application

A Pt on nano-sized CeO₂ particles that in turn are supported on carbon black (CB) was synthesized using the co-impregnation method. This potential anode material for fuel cell applications was synthesized in a stepwise process. The pure CeO₂ was synthesized using an ammonium carbonate precipitation method, and the Pt particles dispersed on the CeO₂ in such a way that a uniform dispersion with the CB was obtained (Pt–CeO₂/CB). The electrochemical activity of the methanol (CH₃OH) oxidation reaction on the Pt–CeO₂/CB was investigated using cyclic voltammetry and chronoamperometry experimentation. The onset potential of CH₃OH oxidation reaction on the Pt–CeO₂/CB anode was shifted to a lower potential as compared with that on commercially available Pt–Ru/carbon (C) alloy anode. In addition, the activation energy of the Pt–CeO₂/CB anode was much lower than that of the Pt–Ru/C alloy anode. Moreover, the current density of the Pt–CeO₂/CB anode was much higher than that of the Pt–Ru/C alloy anode at temperatures between 28° and 60°C. These results suggest that the anode performance of the Pt–CeO₂/CB anode at the operating temperature of typical fuel cells (80°C) is superior to that of the more usual Pt–Ru/C alloy anode. Importantly, the rare metal, Ru, is not required in the present anode material and the amount of Pt required is also significantly reduced. As a consequence, we report a promising candidate Pt–CeO₂/CB composite anode for application in the development of direct methanol fuel cells.     

Polymerization of 2-dibutylamino-1,3,5-triazine-4,6-dithiol on wire during friction process

2-Dibutylamino-1,3,5-triazine-4,6-dithiol (DB) and a mixture of DB and triallylisocyanurate (TAIC) were used as a lubricant during steel wire drawing due to a dry process. DB gave a polymer film with 180 nm in thickness to wire surfaces during the wire drawing. The polymer film had a disulfide structure on the backbone and contained a small amount of DB monomer and olygomer. Molecular weight and polymer weight increased with the drawing rate. The mixture of DB and TAIC gave mainly a three-dimensional polymer film with 225 nm in thickness to wire surfaces during drawing. The polymer film insoluble in THF had mono and disulfide structures and contained a small amount of linear polymer, DB, and TAIC. Such tribological polymerizations are estimated as follows: DB produces dithiyl radicals on a nascent surface formed during drawing and in the presence of oxygen and heat. The dithiyl radicals were polymerized by coupling with each other to give disulfide bonds or added to allyl groups in TAIC to give monosulfide bonds. It is concluded that this technique should be possible to use for unifying metal processing and surface treatment. © 1995 John Wiley & Sons, Inc.     

Influence of ammonium salt on electrowinning of copper from ammoniacal alkaline solutions

In order to develop an energy-saving copper recycling process from wastes, electrochemical measurements were conducted in ammoniacal alkaline solutions containing Cu(I) ions and an ammonium salt of sulfate, chloride or nitrate. The results of each system were then compared. The polarization measurements suggested that the voltage required for the electrode process is lower in the chloride and nitrate systems than that in the sulfate system. The cathode current efficiency during the copper electrodeposition varied from 39 to 97% and increased with current density in the chloride and sulfate systems. In the nitrate system, the lowest cathode current efficiency of 30% was observed because of nitrate ion reduction. Based on these results, the power consumption required for the electrowinning stage of the copper recycling process was calculated. Among these three systems, the chloride system showed the lowest power consumption of 500 kWh t⁻¹ at the current density of 200 A m⁻², which is about 25% of the conventional copper electrowinning process from a copper sulfate-sulfuric acid solution.     

Activity measurement of gallium in the B2 phase of the CoGa–Sb system by the EMF method with zirconia-based solid electrolyte

Gallium activity in the B2 phase regions of both binary Co–Ga and ternary Co–Ga–Sb systems was measured by EMF method with stabilized zirconia solid electrolyte The temperature range was 1073–1273 K and Sb concentrations were 1, 2 and 3 mol fractions. Ga activity at 1173 and 1273 K increases sharply in Ga rich region and the addition of Sb to the CoGa phase increases Ga activity. Activity change corresponds to the lattice parameter change with Sb addition to the CoGa phase.     

Zr-Hf interdiffusion in polycrystalline Y2O3-(Zr+Hf)O2

Lattice and grain-boundary interdiffusion coefficients were calculated from the concentration distributions determined for Zr-Hf interdiffusion in polycrystalline 16Y₂O₃·84(Zr_1–x Hf _x )O₂ withx=0.020 and 0.100. The lattice interdiffusion coefficients were described byD=0.031 exp [–391 (kJ mol^–1)/RT] cm² sec^–1 and the grain-boundary diffusion parameters byD=1.5×10^–6exp [–309(kJ mol^–1)/RT] cm³ sec^–1 in the temperature range 1584–2116° C. Comparison of the results with those for the systems CaO-(Zr+Hf)O₂ and MgO-(Zr+Hf)O₂ indicated that the Zr self-diffusion coefficient was insensitive to the dopants in the fluorite-cubic ZrO₂ solid solutions.     

Fabrication of an Anode-Supported Gadolinium-Doped Ceria Solid Oxide Fuel Cell and Its Operation at 550°C

Ce_0.9Gd_0.1O_{2− x} (CGO) layers were deposited onto nonconductive porous NiO–CGO supports by electrophoretic infiltration, and then compacted by isostatic pressing to achieve a high packing density of the deposited layer. The bilayers were sintered to give dense CGO layers at 1290°C in air. A fuel cell comprising an La_0.6Sr_0.4Co_0.2Fe_0.8O_{3− x} cathode, a 10-μm CGO electrolyte, and a Ni–CGO anode was tested at 550°C with humidified 10% H₂ and air. The cell showed an open circuit voltage of 0.86 V and delivered a steady current of about 470 mA/cm² at a terminal voltage of 0.24 V.     

Structural and hydration properties of amorphous tricalcium silicate

Mechanical milling was carried out to synthesize amorphous tricalcium silicate (Ca₃SiO₅) sample, where Ca₃SiO₅ is the most principal component of Portland cement. The partial phase transformation from the crystalline to the amorphous state was observed by X-ray and neutron diffractions. Moreover, it was found that the structural distortion on the Ca-O correlation exists in the milled Ca₃SiO₅. The hydration of the milled Ca₃SiO₅ with D₂O proceeds as follows: the formation of hydration products such as Ca(OD)₂ rapidly occurs in the early hydration stage, and then proceeds slowly after about 15 h. The induction time for the hydration of the milled Ca₃SiO₅ is approximately one half shorter than that for the hydration of the unmilled one. This result means that the mechanical milling brings about the chemical activity of Ca₃SiO₅ for hydration, and may be particularly useful for increasing the reactivity in the early hydration stage.     

Bioaccumulation, temporal trend, and geographical distribution of synthetic musks in the marine environment

Bioaccumulation of synthetic musks in a marine food chain was investigated by analyzing marine organisms at various trophic levels, including lugworm, clam, crustacean, fish, marine mammal, and bird samples collected from tidal flat and shallow water areas of the Ariake Sea, Japan. Two of the polycyclic musks, HHCB and AHTN, were the dominant compounds found in most of the samples analyzed, whereas nitro musks were not detected in any of the organisms, suggesting greater usage of polycyclic musks relative to the nitro musks in Japan. The highest concentrations of HHCB were detected in clams (258-2730 ng/g lipid wt.), whereas HHCB concentrations in mallard and black-headed gull were low, and comparable with concentrations in fish and crab. These results are in contrast to the bioaccumulation pattern of polychlorinated biphenyls; for which a positive correlation between the concentration and the trophic status of organisms was found. Such a difference in the bioaccumulation is probably due to the metabolism and elimination of HHCB in higher trophic organisms. Temporal trends in concentrations of synthetic musks were examined by analyzing tissues of marine mammals from Japanese coastal waters collected during 1977-2005. HHCB concentrations in marine mammals have shown significant increase since the early 1990s, suggesting a continuous input of this compound into the marine environment. Comparison of the time trend for HHCB with those for PCBs and PBDEs suggested that the rates of increase in HHCB concentrations were higher than the other classes of pollutants. To examine the geographical distribution of HHCB, we have analyzed tissues of fish, marine mammals, and birds collected from several locations. Synthetic musks were not detected in a sperm whale (pelagic species) from Japanese coastal water and in eggs of south polar skua from Antarctica. While the number of samples analyzed is limited, these results imply a lack of long-range transportation potential of synthetic musks in the environment.     

Synthesis and application of fluorescein- and biotin-labeled molecular probes for the chemokine receptor CXCR4

The design, synthesis, and bioevaluation of fluorescence- and biotin-labeled CXCR4 antagonists are described. The modification of D-Lys8 at an epsilon-amino group in the peptide antagonist Ac-TZ14011 derived from polyphemusin II had no significant influence on the potent binding of the peptide to the CXCR4 receptor. The application of the labeled peptides in flow cytometry and confocal microscopy studies demonstrated the selectivity of their binding to the CXCR4 receptor, but not to CXCR7, which was recently reported to be another receptor for stromal cell-derived factor 1 (SDF-1)/CXCL12.     

Kinetic roughening transition and missing regime transition of melt crystallized polybutene-1 tetragonal phase: growth kinetics analysis

The morphology and lateral growth rate of isotactic polybutene-1 (it-PB1) have been investigated for crystallization from the melt over a wide range of crystallization temperatures from 50 to 110°C. The morphology of it-PB1 crystals is a rounded shape at crystallization temperatures lower than 85°C, while lamellar single crystals possess faceted morphology at higher crystallization temperatures. The kinetic roughening transition occurs around 85°C. The nucleation and growth mechanism for crystallization does not work below 85°C, since the growth face is rough. However, the growth rate shows the supercooling dependence derived from the nucleation and growth mechanism. The nucleation theory seems still to work even for rough surface growth. Possible mechanisms for the crystal growth of this polymer are discussed.