High energy-resolution electron energy-loss spectroscopy study of the electric structure of double-walled carbon nanotubes

Electron energy-loss spectra were obtained from two double-walled carbon nanotubes (DWCNTs) with an energy resolution of 85 meV. The spectra showed multiple peak structures between 2 and 3 eV. However, peak positions are different for these two DWCNTs. The chiral indices of CNT layers of the two DWCNTs were determined to be (29,4)(in) (17,8)(out) and (46,6)(out) (26,21)(in), respectively, by comparing experimental electron diffraction patterns with simulated ones. The spectra were also compared with simulated joint density of states, which were derived from the determined chiral indices. It was confirmed that the peak structures in the spectra are due to interband transitions intrinsic for tubular structures of graphitic sheets.     

Scoring resistance of TiC- and TiN-coated gears

In trying to clarify the effect of TiC and TiN coatings on the scoring resistance and wear characteristics of gears, various tests on rollers and gears coated with TiC and TiN coatings have been run. From the test results obtained by an Amsler machine and a power-circulating gear machine, it was found that the seizure resistance of the coated roller pair was larger than that of the uncoated roller pair. Further, the scoring resistance of the gear pair, which was combined with the coated wheel and uncoated pinion, was significantly large, and TiC and TiN coatings had a significant effect on increasing scoring resistance of the gears.     

Simulation study of micro-loading phenomena in silicon dioxide holeetching

A new surface reaction model for a dry-etching topography simulator is propose. First, two types of radical adsorptions are introduced. One is a nondepositive type (Langmuir type) radical adsorption which plays an important role for ion-assisted etching. The other is a depositive type radical adsorption which results in polymer deposition as an etching inhibitor. Secondly, direct and indirect radical transport inside the enclosure of a geometry is self-consistently taken into account based on the present radical adsorption model. Complicated etching/deposition profile evolution is well described by a newly revised string model based on Boolean logical operation. The simulator is applied to study the etching rate, the profile and the selectivity in SiO₂ contact hole etching as a function of depth/diameter or aspect ratio A. Etching rate shows its maximum at an intermediate A, and becomes smaller with increase or decrease of A in the present process condition. The etching profile becomes more vertical as A increases. Etching selectivity to underlying Si becomes lower as A increases. The variations of the etching profile and the selectivity are strongly related to the surface coverage of depositive type radicals on the sidewall and on the bottom of the hole geometry, respectively     

Photocatalytic degradation of organic compounds diluted in water using visible light-responsive metal ion-implanted TiO2 catalysts: Fe ion-implanted TiO2

The application of metal ion-implantation method has been made to improve the electronic properties of the TiO₂ photocatalyst to realize the utilization of visible light. The photocatalytic properties of these unique TiO₂ photocatalysts for the purification of water have been investigated. By the metal ion-implantation method, metal ions (Fe⁺, Mn⁺, V⁺, etc.) are accelerated enough to have the high kinetic energy (150 keV) and can be implanted into the bulk of TiO₂. TiO₂ photocatalysts which can absorb visible light and work as a photocatalyst efficiently under visible light irradiation were successfully prepared using this advanced technique. The UV-Vis absorption spectra of these metal ion-implanted TiO₂ photocatalysts were found to shift toward visible light regions depending on the amount and the kind of metal ions implanted. They were found to exhibit an effective photocatalytic reactivity for the liquid-phase degradation of 2-propanol diluted in water at 295 K under visible light (λ>450 nm) irradiation. The investigation using XAFS analysis suggested that the substitution of Ti ions in TiO₂ lattice with implanted metal ions is important to modify TiO₂ to be able to adsorb visible light.     

Effect of tooth profile modification on the scoring resistance of spur gears

Using power-circulating gear test rigs, the scoring resistance of gears with tooth profile modification and gears without tooth profile modification, both of which were subjected to different amounts of addendum modification, was studied. The effect of tooth profile modification on the scoring resistance of gears with a small amount of addendum modification was significantly increased by the tooth profile modification. The critical surface temperature for scoring lies between 443 and 447 K under the conditions of tooth material and lubricant used. The scoring resistance of gears can be accurately estimated by evaluating the critical surface temperature.     

Lattice parameter determination of a composition controlled Si1-x Gex layer on a Si (001) substrate using convergent-beam electron diffraction

The six lattice parameters (a, b, c, alpha, beta and gamma) of Si(1-x)Ge(x), which was grown epitaxially on a Si (001) substrate with a varying Ge concentration, were determined by convergent-beam electron diffraction (CBED) without any assumption of crystal lattice symmetry. It was revealed that the lattice parameter c of Si(1-x)Ge(x) varies linearly with the Ge concentration and that the lattice symmetry is lowered from cubic to tetragonal, excluding an artifact due to the thinning of the specimen. The effect of strain relaxation that is caused by thinning specimens is discussed. Ge concentrations of examined specimen areas are evaluated using the obtained lattice parameters.     

Development of a sub-eV resolution soft-X-ray spectrometer for a transmission electron microscope

We constructed a grazing-incidence soft-X-ray spectrometer for a transmission electron microscope. The spectrometer, which was composed of a grating and a CCD detector, was attached to a JEM2000FX transmission electron microscope. B K-emission spectra of hexagonal boron-nitride, which give the density of states of the valence band of the material, were obtained with an energy resolution of about 0.6 eV.     

Development of a cryogenic stage for an ion-milling instrument

A specimen-cooling device has been designed, manufactured and integrated into a commercial ion-milling instrument for transmission electron microscopy. The instrument enables us to prepare section specimens of tin-plated Cu without forming intermetallic compound particles and/or voids. The results show that cooling of specimen during ion-milling process is necessary for fine structure investigations of low melting temperature materials.     

Antioxidant effect of naturally occurring furan fatty acids on oxidation of linoleic acid in aqueous dispersion

Naturally occurring furan fatty acids were synthesized and their antioxidant activity has been studied during the oxidation of linoleic acid in the phosphate buffer, pH 6.9, in the dark. The extent of the oxidation was followed both by the accumulation of conjugated diene and by the measurement of the residual amounts of linoleic acid. The tetra-alkylsubstituted furan fatty acids were found to suppress the oxidation. The trialkylsubstituted compound also showed antioxidant activity, being about 50% as effective as the tetra-alkylsubstituted ones. The di-alkylsubstituted one revealed no significant activity. The antioxidant activity of furan fatty acids depended on the number of substituents on the furan ring. Therefore, a tetra-alkylsubstituted furan ring may be necessary for the antioxidant action of furan fatty acids. The tetra-alkylsubstituted furan fatty acids reduced 1,1-diphenyl-2-picrylhydrazyl, reacted with the peroxyl radical generated from the thermal decomposition of a radical initiator, 2,2′-azobis(2-amidinopropane)hydrochloride (AAPH), and also suppressed the AAPH-induced oxidation of linoleic acid, indicating that, by scavenging, the peroxyl radical furan fatty acids inhibit the oxidation.