Catalytic Performance of Metal Nanoparticles Supported by Ceramic Composite Produced by Partial Reduction of Solid Solution with Dopant

A composite with well-dispersed metal nanoparticles at a ceramic surface was produced by partial reduction of solid solution. It was found that a small amount of dopant, such as Al₂O₃, Cr₂O₃, or Sc₂O₃, accelerated the precipitation of the metal nanoparticles during the reduction. Catalytic performance of the composite for methanol reforming was evaluated. In the Ni-based catalysts, the dopant decreased the CO production by promoting a methanation reaction, while in the Co-based catalysts, the dopant did it by inducing a water–gas shift reaction. Co/MgO with Sc₂O₃ doping showed the most preferable reforming performance, high H₂ production, and CO₂ selectivity.     

Strength of β-sialon/Si3N4 layered composites

The strength of layered composites consisting of -sialon and Si3N4 layers, which were prepared by hot pressing, was investigated. The strength increased as the thickness of the sialon (outer layer) decreased, and reached almost the same level of Si3N4 (inner layer) when the sialon thickness was 250–300 m. No specific fracture morphologies were recognized around the interface of sialon and Si3N4. The aluminium concentration changed sharply around the interface, while the yttrium tended to diffuse deeper than aluminium. This tendency was remarkable in the samples hot-pressed at higher temperature (1900°C). The existence of compressive residual stress in the surface sialon layer was revealed and the residual stress increased as the sialon thickness decreased down to 250–300 m. The increase of strength with the decrease of sialon thickness was discussed based on the mechanical calculations in which the residual stress was considered. This calculation approximately agreed with the results of the samples hot-pressed at lower temperature (1800°C). However, the strength of the samples hot-pressed at 1900°C was much higher than the prediction in the thin range of the sialon thickness. The deep diffusion of yttrium into the sialon layers was thought to be one of the causes of this unpredictable effect.     

Studies on syntheses and permeabilities of special polymer membranes. XIV. Permeation characteristics of modified nylon 12 membranes

The permeation characteristics and the burst strength of nylon 12 membranes treated with heat in various solutions such as aqueous solutions of formic acid, formic acid/formalin, and sodium hydroxide/ formalin were investigated under various conditions. They were significantly influenced by the treatment solution, temperature and time, and the concentration of acid and alkali in the treatment solution. In particular, nylon 12 membranes treated with formic acid/formalin remarkably improved the permeation characteristics and the burst strength. These phenomena were discussed from the standpoint of the effective pore size and pore number in the membrane, and the form and aggregation of polymer molecules forming the membrane.     

Quantitatively investigating the self-attraction of nanowires

The self-attraction of nanowires(NWs)would lead to NWs bunching up together when fabricated in high density and the short circuit of NW-based devices during ser...     

Component spatial pattern analysis of chemicals by use of two-dimensional electro-optic terahertz imaging

We demonstrate a method of chemical mapping by using the transillumination terahertz (THz) images obtained by two-dimensional electro-optic THz imaging. The images and spectral data were measured between 0.1 and 1.0 THz. An experimental sample consisting of three chemicals was prepared, with one in two concentrations. By introducing the component spatial pattern analysis based on the least-squares method, the chemical composition, spatial distribution, and difference in concentration were clearly determined.     

Polyethylene paper insulation impregnated with liquid nitrogen

Polyethylene paper tape wrapped insulation impregnated with liquid nitrogen for cryogenic cables was studied using model cable specimens, 66 kV cryocable samples, and 275 kV cryocable samples. This insulation system performs well in that (1) voltage deterioration is small, (2) thickness dependence is small, and (3) dissipation factor is small. This insulation system is one of the most promising systems for a large capacity transmission cryogenic cable.     

A study of breakdown strength of liquid nitrogen cooled power cables

A 66 KV liquid nitrogen cooled cryogenic cable was manufactured and tested using ac and impulse voltages.Liquid nitrogen cooled cryogenic cables will be in practical use over the 275–500 kV range. Study of the 66 kV class cable is the first step towards the development. The insulation system of this cable is polyethylene paper tape wrapped insulation impregnated with liquid nitrogen and its insulation thickness is about 7.75 mm. The influence of bending, conductor surface effect, and thickness dependence on the breakdown strength are discussed.     

Bactericidal activity of copper-deposited TiO2 thin film under weak UV light illumination

The bactericidal activity of copper-deposited titanium dioxide thin film (Cu/TiO2) was investigated under very weak ultraviolet (UV) light illumination. To elucidate the roles of the film photocatalyst and the deposited copper in the bactericidal activity, cells from a copper-resistant Escherichia coli (E. coli) strain were utilized. A decrease in survival rate was not observed with the copper-resistant cells under dark conditions, but when illuminated with a very weak UV intensity of 1 microW/cm2, the survival rate decreased, suggesting photocatalytic bactericidal activity. The decay curve of survival on the Cu/TiO2 film under very weak UV light illumination consisted of two steps, similar to the survival change of normal E. coli on TiO2 films under rather strong UV illumination. The first step is due to the partial decomposition of the outer membrane in the cell envelope by a photocatalytic process, followed by permeation of the copper ions into the cytoplasmic membrane. The second step is due to a disorder of the cytoplasmic membrane caused by the copper ions, which results in a loss of the cell's integrity. These processes explain why the Cu/TiO2 film system shows an effective bactericidal activity even under very weak UV light illumination.