Preparation and characterization of Ni–PTFE plate as an electrode for alkaline fuel cell: Effects of conducting materials on the performance of electrode

Polytetrafluoroethylene (PTFE) fine particles (25 μm) were coated with 29–43 wt% Ni using electroless Ni plating. The Ni-plated PTFE (Ni–PTFE) particle conductivity increased concomitantly with increasing Ni contents. For 43 wt% Ni particles, the conductivity was about 300 S m⁻¹. After pressing the particles into plates with 300 kg cm⁻² pressure and subsequent heat treatment at 350 °C, acetylene black (AB) and graphite particles were introduced into the plates as conducting materials to elucidate effects on electrical conductivity and gas permeability. Plates containing AB (1.3 wt%) and graphite (5 wt%) respectively showed 1.25 and 1.5 times higher conductivity than the original Ni–PTFE plate did. The AB particles particularly caused pore volume expansion at the 0.1–1.0 μm size range in Ni–PTFE plates. The expanded total pore volume (0.159 cm³ g⁻¹) of Ni–PTFE plate with AB particles improved gas permeability, which increased the electrode life performance (25% up for 24 h) in alkaline fuel cells (AFCs). The current density of Ni–PTFE electrode containing AB particles was about 4.5 times than that of original Ni–PTFE electrode.     

Pseudo-capacitance of composite electrode of ruthenium oxide with porous carbon in non-aqueous electrolyte containing imidazolium salt

Pseudo-capacitance of composite materials where ruthenium oxide particles are loaded on activated carbon has been evaluated in the electrolyte of 1-ethyl-3-methyl imidazolium tetrafluoroborate dissolved in acetonitrile. The composite materials prepared by conventional a sol-gel method have dispersed structure of ruthenium oxide particle of tens nanometer diameter on the surface of activated carbon. The extent of the pseudo-capacitance of the composite electrodes in the imidazolium salt electrolyte, estimated by the comparison of the capacitance per surface area of electrode in different non-aqueous electrolyte, is ca. 3-5 μF cm⁻² in addition to the double-layer capacitance of ca. 6 μF cm⁻², depending on the loading status of ruthenium oxide. The symmetric cell consisting of the composite electrode containing 18 wt% of ruthenium oxide and the imidazolium salt electrolyte provides cell capacitance based on the pseudo-capacitance by a constant-current test.     

Growth prediction of two interacting surface cracks of dissimilar sizes

When multiple cracks approach one another, the stress intensity factor changes due to the interaction of the stress field. This causes variation in the crack growth rate and shape of cracks. In particular, when cracks are parallel to the loading direction, their shape becomes non-planar due to the mixed mode stress intensity factor. In this study, the growth of interacting surface cracks was simulated by using the S-version finite element method, in which a local detailed finite element mesh (local model) is superposed on a coarse finite element model (global model) representing the global structure. First, simulations were performed for fatigue crack growth experiments and the method validity was shown. Second, simulations were conducted for various relative sizes and spacings of twin cracks. It was shown that the offset distance and the relative size were both important parameters to determine the interaction between two surface cracks; the smaller crack stopped growing when the difference in size was large. It was possible to judge whether the effect of interaction should be considered based on the correlation between the relative spacing and relative size.     

Development of a water-resistant and detergent-washable powder coated with a stimuli-responsive polymer and its application to suncare products

IFSCC Magazines , 12 (2009) (1) 3–7
It is generally well known that the surface of an inorganic UV-protective powder used in a sunscreen formula is treated with a fatty acid or other hydrophobic chemicals to obtain a high water resistance. Due to the resulting strongly hydrophobic surface, the treatment has a clear drawback in that it allows the sunscreen to leave its base components on the skin after washing with regular soap. Therefore, in this study to develop an intelligent sunscreen formula that has a high water resistance and can be washed away easily with regular soap, we focused on a pH-responsive polymer as the surface-treatment agent for a UV-protective powder. Numerous experiments led to the synthesis of the 2-acrylamido-2-methyl-1-propanesulfonic acid/11-methacrylamidoundecanoic acid (AMPS/MAU) copolymer, which is hydrophobic in acidic to neutral solution and hydrophilic in basic solution. Titanium dioxide subjected to surface treatment was treated with the AMPS/MAU copolymer showed a high pH-responsiveness that was similar to that of the polymer. A W/O-type sunscreen containing the pH-responsive titanium dioxide showed a high water resistance as well as a high washability with regular soap.
Keywords:  Detergent-washable, pH-responsive polymer, pH-responsive powder, sun care product, water-resistant     

Automatic unbalance correction of rotors by sympathetic phase inversion of ultraviolet-curing resin

We developed an automatic unbalance correction technique for unbalanced rotors using a sympathetic phase inversion of ultraviolet (UV)-curing resin. Correcting the unbalanced weight during production is essential for various industrial rotors. The reduction of the cost and time of the correction process of unbalance during production is of great importance; however, the correction must have high precision, particularly for low-cost rotors such as polygon scanner motors and hard disks. In this paper we propose a new technique for correcting the unbalance of polygon scanner motors. Our system rotated a rotor on a translational oscillation table at a speed higher than that of the resonance rotation speed. The rotor exhibited runout opposing the unbalanced weight at this speed, and UV-curing resin preliminarily injected into the rotor also positioned itself opposite the unbalanced weight. UV light at this point cured the resin to immediately counter the unbalanced weight. Our experimental system confirmed the feasibility of this correction technique and reduced the unbalanced weight to 20% of that before the correction. This was in good agreement with the theoretical analysis.     

The relationship between AE and dissipation energy for fretting wear

This paper describes the behavior of acoustic emission (AE), especially the correlation between the AE output and the dissipation energy under the fretting conditions. Fretting tests are conducted with a ball contacting with a flat disc in air. The specimens used are a bearing steel for a ball, and a bearing steel or an aluminum alloy for a flat disc. The results show that the behavior of the AE output and the dissipation energy during each fretting cycle is not so similar to each other throughout the test, but the total AE root-mean-square and the total dissipated energy during the test have a good correlation between them.     

An estimation of factors influencing residual stress characteristics of fillet welded lap joints

The residual stress behaviours in fillet welded lap joints of sheet metal have been researched in a systematic testing procedure with varied steel types, steel thicknesses and welding wires having different transformation points. Consequently, under the simulated fabrication welding conditions (with a constant amount of deposited metal), the transverse residual stress at the weld toe, which is deemed critical in fatigue strength, has been found almost invariable to a change in steel type and thickness, but it has been clarified to become compressive to a greater extent as the wire’s transformation point is lower. Moreover, as for the residual stress inside the weld metal, the compressive residual stress area has been found to expand as the welding wire’s transformation point reduces, from the results of the thermo-elastic-plastic analysis.     

Mechanistic Study on the Degradation of Thermal Barrier Coatings Induced by Volcanic Ash Deposition

Thermal stress generated on thermal barrier coatings (TBCs) by volcanic ash (VA) deposition was assessed measuring the tip deflection of a multilayered beam structure as a function of temperature. The TBC in this study was deposited onto the surface of a blade utilized in a land-based gas turbine which is composed of 8 wt.%Y₂O₃-ZrO₂/CoNiCrAlY on a Ni-based superalloy. The VA-deposited TBC sample was heated at 1453 K, and the effect of VA deposition on TBC delamination was examined in comparison with a TBC sample without VA deposition as a reference. On the basis of the VA attack damage mechanism which was investigated via the tip deflection measurement and a comprehensive microstructure examination, a damage-coupled constitutive model was proposed. The proposed model was based on the infiltration of the molten VA inside pores and phase transformations of yttria -tabilized zirconia in the TBC system. The numerical analysis results, which were simulated utilizing the finite element code installing the developed constitutive model, showed us that VA attack on the TBC sample induced near-interfacial cracks because of a significant increasing in the coating stress.     

Influence of Gravel on the Compression Characteristics of Decomposed Granite Soil

Large-scale one-dimensional compression tests were performed in order to analyze the influence of gravel on the compression properties of gravel-mixed decomposed granite soils. After adjusting the gravel contents of the said soil, specimens compacted at a certain level of compaction energy and water content were tested. Based on the test results, it was observed that when gravel-mixed decomposed granite soil was compacted at the same energy level, there existed a specific gravel content at which the dry density was maximum and which also produced the minimum compression index. Furthermore, an expression based on two-phase mixture theory was proposed to quantitatively evaluate the effects of gravel content through a material parameter calculated using the theory, and the estimated compression curves agreed very well with the results of the experiments.