Yozo Kakudate

Rise and Fall of Surface Level of Water Solutions under High Magnetic Field

Magnetic field effects on the surface profile have been investigated for water and copper sulfate aqueous solutions that have very small magnetic susceptibility. When a field of 10 T is applied in a horizontal superconducting magnet, the surface of distilled water was lowered by 39 mm at the field center, relative to the level at the zero field region (Moses effect). In contrast, the surface of a nearly saturated copper sulfate aqueous solution was raised by roughly the same height at the center (reversed Moses effect). The profiles were systematically explained based on the dia- and paramagnetic volume susceptibility values of distilled water and copper sulfate aqueous solution, respectively.

Sonochemical production of a carbon nanotube

Abstract Sonochemical production of a carbon nanotube has been studied. The carbon nanotube is produced by applying ultrasound to liquid chlorobenzene with ZnCl2 particles and to o-dichlorobenzene with ZnCl2 and Zn particles. It is considered that the polymer and the disordered carbon, which are formed by cavitational collapse in homogeneous liquid, are annealed by the inter-particle collision induced by the turbulent flow and shockwaves.

Onion-like carbon deposition by plasma spraying of nanodiamonds

Abstract A deposit of carbon nanoparticles based on an onion-like structure was fabricated from detonation nanodiamond powders by a novel plasma spraying process, electromagnetically accelerated plasma spraying (EMAPS). EMAPS was able to transform nanodiamonds to onion-like structured carbon within 300 μs through a thermal graphitization process in which the temperature of the particles would be in the range of 2700–4500 K. Synthesized onion-like carbon nanoparticles were spherical or polyhedral. The G-band in the UV–Raman spectra of the produced deposits was found to be a superposition of a characteristic band of well-formed carbon onions at 1571 cm −1 and the G-band of defective carbon onions at 1592 cm −1 . The availability of a plasma spraying process for developing solid lubricant coatings incorporating nanodiamond and onion-like carbon was demonstrated.

Sonochemical polymerization of benzene derivatives: the site of the reaction.

Sonochemical polymerization of benzene and halogen-substituted benzenes has been studied. The difference of absorption spectra of polymerization products can be explained qualitatively using bond energies of the primary products. The relative rate constant of the polymerization reaction is apparently proportional to the inverse of the vapour pressure of the liquids. Using this relation, we analysed the relative rate constant of the polymerization in benzene/chrolobenzene mixtures. From this, we conclude that sonochemical polymerization proceeds in the vapour phase of a bubble.

Possible new route for the production of C60 by ultrasound

The production of C60 by ultrasonic irradiation of liquid benzene has been studied. After irradiating 150 ml of liquid benzene for 1 h (600 W, 20 kHz), approximately 1 microgram of C60 is produced.

Magnetic field effect on interface profile between immiscible nonmagnetic liquids—Enhanced Moses effect

The change in the interface profile between immiscible nonmagnetic liquids was investigated quantitatively in a superconducting magnet with a large horizontal bore. The interface profile changed into concave down or up at the field center accordingly to the balance of magnetic susceptibilities between the lower and upper liquids. A flat interface was also demonstrated when the susceptibilities were balanced. It was found that modification of the interface profile was significantly amplified under an applied field as low as 1 T when the densities of the two liquids were quite close. The morphological change induced by the applied magnetic field can be used to remove a boundary, which initially separates two liquids without the field, and to initiate a mixing process or a chemical reaction between the two liquids.

Synthesis of B-C-N thin films by electron beam excited plasma CVD

Abstract Boron–carbon–nitrogen (B–C–N) thin films were synthesized using an electron beam excited plasma (EBEP)-CVD method and their properties and structure investigated. By controlling the flow rate ratios of process gases, we obtained films with composition expressed as BxCyN, where x=0.9–4.7 and y=0.5–6.0. Hydrogen content is very small, of the order of 1 at.%. The hardness of the films increases monotonically with increasing boron content and reaches 29 GPa. Results of X-ray photoelectron spectroscopy, Fourier transform infrared transmission and X-ray diffraction measurements show that while the films consist of a sp2-bonded B–C–N structure in a boron poor region, a sp3-bonded structure exists as well as the sp2-bonded structure in a boron rich region.

Pressure effect on magneto-optical properties in CdTe/(Cd, Mn)Te single quantum wells with high Mn concentration

The pressure effect on the magnetic field induced type I–type II transition is studied in a CdTe/Cd1−xMnxTe (x=0.24) single quantum well. Photoluminescence measurements under hydrostatic pressures up to 1.07 GPa and long pulsed magnetic fields up to 60 T with a pulse duration of 2 s are reported. The pressures were generated in a plastic diamond anvil cell. A bend toward lower energies (additional red shift) is observed above 28.5 T in magnetic field dependence of the exciton energy for a 13 A thick quantum well. We attribute this red shift to a phenomenon preceding the type I–type II transition after a comparison with a simple quantum mechanical calculation. The onset field of the additional red shift increases by 3.4 T by applying a pressure of 1.07 GPa. Spin–spin coupling between the exciton and the Mn ion in the interface region is also investigated and found to be enhanced by pressure.

Diamond Powders Less Than 100 nm in Diameter as Effective Solid Lubricants in Vacuum

The frictional behavior of detonation nanodiamond and single-crystal fine diamond powders were studied to determine the effect of particle diameter on their lubricative and abrasive characteristics. In vacuum, nanodiamond with an average aggregate size of 75 nm and mechanically crushed single-crystal diamond powders with an average diameter of 50 nm formed a uniform lubricating layer while sliding against a SiC ball and showed very low friction coefficients of 0.03 and less than 0.01, respectively, under moderate conditions of 0.5 N applied load and 3.5 mm/s sliding speed. A clear tendency was observed for both the friction coefficient and specific wear rates to decrease with decreasing particle/aggregate size.

Formation of boron carbide coating by electromagnetically accelerated plasma spraying

Abstract Boron carbide (B 4 C) coating formation is investigated using an electromagnetically accelerated plasma spraying, which can generate a dense and a high velocity plasma jet of 1 MPa and 2.0–2.5 km/s by applying a pulsed high-current arc-discharge to accelerate and heat powders. Highly crystalline B 4 C coatings with roughened coating-substrate interfaces were formed on mirror-polished stainless (SUS304) substrates without a binder material. The density and uniformity of the coating are improved by changing the source powder size from 30 to 10 μm, where the estimated porosity is decreased from 9 to 4%.