Cell performances of direct methanol fuel cells with grafted membranes

Cell performances were evaluated with grafted polymer membranes as an electrolyte for a direct methanol fuel cell (DMFC). The membranes were prepared using a poly(ethylene-tetrafluoroethylene), or ETFE, film. The base polymer film was added to sulfonic groups using γ-radiation activated grafting technique as ion-exchange groups. These membranes had more suitable properties for DMFCs, i.e. higher electric conductivity and lower methanol permeability than perfluorinated ionomer membrane (Nafion). Nevertheless, the cell performance with the grafted membrane was inferior to that with Nafion. The analysis of electrode potentials vs. reversible hydrogen electrode showed larger activation overpotential for both the electrodes on the grafted membranes. We concluded that this is due to poor bonding of the catalyst layers to the grafted membranes.     

Catalytic Methoxycarbonylation of Aromatic Diamines with Dimethyl Carbonate to Their Dicarbamates Using Zinc Acetate

The methoxycarbonylation of 2,4-toluene diamine and 4,4-diphenylmethane diamine with dimethyl carbonate to the corresponding dicarbamates using zinc acetate was carried out at 453 K. Zn(OAc)₂, prepared by evacuating Zn(OAc)₂2H₂O at 383 K for 2 h, yields dimethyltoluene-2,4-dicarbamate in 96% yield in 2 h, while Zn(OAc)₂2H₂O yields dimethyl-4,4-methylenediphenyldicarbamate in 98% yield at 453 K in 2 h.The structure of methyl 3-amino-4-methyl phenyl carbamate, which is one of the intermediates for the reaction of 2,4-toluene diamine with dimethyl carbonate into dimethyltoluene-2,4-dicarbamate, has been determined by measuring the NOE spectrum of ¹H NMR.     

Catalytic Combustion of Volatile Organic Compounds on Supported Precious Metal Catalysts

Catalytic combustion of volatile organic compounds (VOCs) was investigated on supported precious metal catalysts. The activities for the combustion of methane and acetaldehyde were closely related to the reducibility of the precious metal oxides of the catalysts. On the other hand, light-off temperatures for toluene combustion on PdO/Al₂O₃, PdO/SnO₂, and PdO/CeO₂ were around 200 °C, although PdO/ZrO₂ showed a higher temperature of 240 °C. This result indicated that light-off temperatures depend on not only the catalytic activities but also the catalyst structure because of low concentration of toluene and weak interaction between catalysts and toluene. In this experiment, the PdO/SnO₂ catalyst showed highest activity for the combustion of methane and VOCs.     

Low loss fibre transmission of high speed pulse signals at 1.29 ?m wavelength

Using InGaAsP semiconductors laser emitting at 1.29 ?m wavelength as optical sources, and low-loss germanium-doped single-mode silica fibres with 11 km lengths, optical transmission experiments were carried out at 400 and 800 Mb/s bit rates.     

GaAs Hall-effect devices fabricated by ion-implantation technique

Gallium-arsenide Hall-effect devices were developed by using Se-implanted n layers. A Hall voltage of 85 mV was generated at I = 1 mA and B = 5 kgauss. The imbalance voltage appearing was below 1.4 mV at I = 1 mA and B = 0.This fabrication technique is very promising in the high throughput of GaAs Hall-device production.     

Development of multicomponent vaporization/condensation model for a reactor safety analysis code SIMMER-III: Extended verification using multi-bubble condensation experiment

Complex phenomena such as phase transitions and heat transfers in multiphase, multicomponent flows were modeled in the fluid-dynamics portion of SIMMER-III, which was developed to appropriately assess core disruptive accidents (CDAs) in liquid–metal fast reactors (LMFRs). A new multicomponent vaporization/condensation (V/C) model was developed and introduced to SIMMER-III by the authors. In the present study, a new series of multi-bubble condensation experiments was performed to demonstrate that SIMMER-III with the present V/C model is practically applicable to multicomponent, multiphase flow systems with phase transition. In the experiments, bubble diameters and void fractions were quantified from visualization images using original image-processing techniques. Comparing SIMMER-III predictions with experimental data, it was confirmed that SIMMER-III with the proposed V/C model could suitably represent the effects of noncondensable components on the condensation process in multi-bubble systems. This work has improved the reliability of SIMMER-III with regard to multicomponent phase-transition phenomena.     

Positive Temperature Coefficient of Resistivity in Ba1-xSrxPb1+yO3-8 Ceramics

The positive temperature coefficient of resistivity (PTCR) effect in Ba_1-xSr_xPb_1+yO_3-s ceramics is systematically studied. The influence of the preparation conditions on the PTCR properties is experimentally tested. The PTCR effect in metallic-conducting BaPb_1+yO₃ is confirmed around 700°C. The temperature where the PTCR effect starts can be shifted to a higher temperature range by substituting strontium for the A-site barium. By the enhancement of the sintering, the magnitude of the PTCR effect was increased and the resisitivity was reduced. In addition to Pb(IV) in the perovskite structure, Pb(II) is detected at the grain boundary in the sintered body.     

Molecular dynamics simulation of amorphous silicon with Tersoff potential

We have performed molecular dynamics simulation of amorphous silicon (a-Si) by rapid quenching, with empirical interatomic potential (Tersoff potential) as a first step toward hydrogenated amorphous silicon film growth simulations. The numerical results on structural properties showed fairly good agreement with experimental data or numerical results from ab-initio molecular dynamics in other groups. In our a-Si sample, the average coordination is 4.2 and approximately 18% of the atoms have a coordination number of 5. In addition, visualization of the a-Si sample by computer graphics made it possible to see that there are some microcavities in the sample, which was predicted in experimental data.     

<Emphasis Type="Italic">In-Situ</Emphasis> Scanning Electron Microscopy/Electron Backscattered Diffraction Observation of Microstructural Evolution during <Emphasis Type="Italic">α</Emphasis> → <Emphasis Type="Italic">γ</Emphasis> Phase Transformation in Deformed Fe-Ni Alloy

This article presents in-situ observation of ferrite (α)/austenite (γ) phase transformation in an Fe-8.5 at. pct Ni alloy deformed by rolling using an automated scanning electron microscopy/energy backscattered diffraction (SEM/EBSD) system. During heating, recrystallization in α phase and α → γ phase transformation independently occurred. The γ grains nucleated in unrecrystallized α grains were most probably incorporated into the grain interior of recrystallized α grains. They did not have any specific orientation relation (OR) with recrystallized α grains and grew in an isotropic manner. On the other hand, the intragranular γ grains nucleated in recrystallized α grains had a Kurdjumov–Sachs (K-S) OR with the α grains and grew in a considerably anisotropic manner. They preferentially grew along the common direction of surface traces of {110} _α /{111} _γ . Approximately half of grain boundary (GB) allotriomorphs had either the K-S OR or the Nishiyama–Wasserman (N-W) OR with the parent α grains. The γ allotriomorphs predominantly grew into the α grain having the special OR with themselves. The GB character distribution of γ phase at high temperatures was measured. The fraction of CSL boundaries was as high as 63 pct, particularly that of Σ3 grain boundaries (GBs) was 54 pct.     

Reduction characteristics of Fe-Bi-P mixed oxide catalysts and their ammoxidation activities of propylene

The characteristics of Fe-Bi-P mixed oxide catalysts of different compositions for reduction by propylene or ammonia and the ammoxidation activities of propylene were studied using a McBain type thermobalance and the pulse reaction technique respectively. By comparing the dependency of the reduction characteristics and catalytic activity with oxide composition and also the reduction rates and reoxidation rates of the reduced catalyst it was concluded that the ammoxidation of propylene on Fe-Bi-P mixed oxide catalyst proceeds through alternate repetition of reduction by propylene and reoxidation by oxygen, and that abstraction of allylic hydrogen from adsorbed C₃H₆ is the rate determining step.