Kenji Sugiyama

Multiple-species ion beams from titanium-hafnium alloy cathodes in vacuum arc plasmas

We have studied the ion spectra of the plasma produced by the metal vapor vacuum arc for the case when the cathode material is a solid solution TiHf alloy of variable composition ratio. A vacuum arc ion source was used to generate an intense beam of metal ions and a time‐of‐flight ion charge‐to‐mass diagnostic was used to measure the beam ion species and charge state distributions. A range of different cathode compositions was examined, from pure Ti to pure Hf and with five different alloy mixes between these extremes. We find that the ratio of ion currents in the multiple‐species ion beam corresponds approximately to the ratio of elements in the cathode, and that the mean charge states of the elemental ion components remain approximately constant as the cathode composition ratio is changed. Multispecies metal ion beams can readily be generated in this way and the ion species characteristics of the beam are predictable.

Microstructure and wear behaviour of chromium nitride films formed by ion-beam-enhanced deposition

Abstract Chromium nitride films were deposited on AISI 52100 steel substrates by chromium evaporation and simultaneous nitrogen ion beam irradiation, either by varying the arrival ratio of Cr to N atoms at the substrate while keeping the N ion beam current constant, or by varying the ion beam current while keeping the Cr/N arrival ratio constant. Glow discharge spectroscopy analyses show that the Cr/N ratio of the films is strongly affected not only by the Cr/N arrival ratio but also by the N ion beam current. X-ray diffraction analyses show that the crystalline structure of the films changes from CrN for a film with low Cr/N ratio to Cr 2 N for a film with high Cr/N ratio. Although the friction coefficient of the films against an untreated AISI 52100 steel pin does not decrease much from that of the untreated substrate, the wear characteristics are greatly improved. Regarding the influence of the process conditions on the wear characteristics, a small amount of wear is achieved for the films with Cr/N arrival ratios of 1/1 and 1.5/1, which have both high hardness and good adhesion to the substrate.

SYNTHESIS OF ACTINIDE CARBIDES ENCAPSULATED WITHIN CARBON NANOPARTICLES

Actinide carbides encapsulated with multilayered graphitic capsules have been produced by the arc burning of a composite carbon rod containing thoriated tungsten or uranium ore. The morphology of these filled nanoparticles was observed by transmission electron microscopy. The preferential encapsulation in the constituent elements of the core materials surrounded by the graphite cage was demonstrated. Furthermore, it was found that these carbon nanoparticles filled with radioactive materials have been quite stable for 1 year or more.

Basic characteristics of chromium nitride films by dynamic ion beam mixing

Abstract Chromium nitride films were deposited on steel substrates by chromium evaporation and simultaneous irradiation with a nitrogen ion beam, with the Cr/N atom arrival ratio between 1/2 and 2/1, and the acceleration voltage of ions between 10 and 30 kV. Glow discharge spectroscopy analyses show that the Cr/N ratio of the films increases with increasing acceleration voltage, as well as increased Cr/N arrival ratio. With X-ray diffraction analyses, CrN crystal has been detected in the nitrogen-rich films. As the Cr/N ratio increases, C2N crystal appears and gradually increases at the expense of CrN. Micro-Vickers hardness measurements show that films with higher Cr/N ratio have lower hardness. Although the friction coefficient of films with AISI 52100 steel pin does not decrease much the wear amount significantly decreases compared to untreated AISI 52100 steel substrates.

Synthesis of lanthanum compound encapsulated within carbon nanoparticles

Abstract Encapsulated forms in multilayered graphitic capsules have been studied by varying the lanthanum compounds filled in the positive graphite electrode. The morphology of these filled nanoparticles was observed by transmission electron microscopy. It was found that the encapsulated forms in nanoparticles varied with the compounds filled in the anode: in the case of a La2O3/graphite, a LaN/graphite, and a LaB6/graphite composite anode, the corresponding encapsulated forms are LaC2, La, and LaB6, respectively.

SUPERCONDUCTING TRANSITION AT 12.5 K IN RBXC60

Abstract The effect of heat treatment of RbxC60 (x = 3, 4, 5, and 6) on the superconducting transition has been studied with shielding diamagnetism measurements. For RbxC60 (x = 4, 5, and 6), a superconducting transition at 12.5 K appeared in the course of annealing treatment at 400°C and disappeared on further prolonged annealing, while a clear superconducting transition at 30 K due to the Rb3C60 phase still remained. We speculate that this superconducting transition at 12.5 K is due to a certain phase which appears in the course of the annealing treatment.

Friction properties and microstructural changes of SUS440C implanted with various metal ions

Abstract Friction properties and microstructural changes of SUS440C implanted with ions of IVa group (Ti, Zr, Hf), Va group (V, Ta), VIa group (Cr, W), VIIIa group (Fe), IIIa group (Y) and Ib group (Ag) in the periodic table were investigated. Specimens implanted with Ti, Zr, Hf, V, Ta and Y showed a decrease in the friction coefficient during reciprocating sliding tests at a load of 0.245 N. At higher weight loads, the specimens implanted with Ti, Zr, Hf and Y showed low friction. In the specimens implanted with Ti, Zr, Hf, V and Ta ions (IVa and Va groups), C invasion in the surface layer was detected and amorphous phase formation was observed. In the Y implanted specimen, yttrium oxide film was formed on the surface. Low friction observed in the specimens implanted with the ions of IVa and Va groups was due to the existence of an amorphous phase. In the Y implanted specimen, yttrium oxide film which is considered to act as a lubricant film promoted the low friction.

Wear-resistance improvement of steel surface by Ti+C ion implantation

Ti and C ion implantation was studied as a means of improving the wear resistance of steel surfaces. Titanium ions of 5 × 10 17 ions/cm 2 , which are sufficient for forming a ternary amorphous alloy, were implanted followed by carbon ions implantation over the dose of 1.2 × 10 18 ions/cm 2 , nearly equal to the saturation dose, into forged steel. Wear resistance was evaluated by a reciprocating sliding, a pin-on-disc and a roll rotating wear tester. In each case, the wear of Ti and C ion implanted specimens was significantly less than unimplanted specimens. Moreover, in the case of the roll rotating wear test, it was revealed not only the implanted specimen but also its mating roll showed reduced wear. With investigation of the ion implanted surface structure, the presence of carbon rich layer, which has a special structure, was found in the specimen with the superior wear resistance. It was revealed this special structure appears when the carbon dose exceeds 1.2 × 10 18 ions/cm 2 .

Properties of Alkali-Fulleride Superconductors RbxC60

We report on the properties of alkali-metal doped C60 superconductors prepared by the reaction of C60 with rubidium metals. The effects of mixing and heat treatment of RbxC60 (x = 3, 4, 5, and 6) samples prepared over a wide range of nominal compositions on the supercoducting transition were determined from shielding diamagnetism measurements. More importantly, it was found that prolonged annealing at 400 °C in the samples RbxC60 (x = 4, 5, and 6) caused a superconducting transition-like anomaly at about 12 K, remaining a clear superconducting transition at 30 K due to the RbxC60 phase.

Preparation of Fullerene Derivatives by Resistive Heating With Graphite Crucible

Abstract We report here the preparation of both endohedral fullerenes (La°C82, La2°C80) and exohedral fullerenes (C60 (CmOn)) by the resistive heating with graphite crucible filled with lanthanum oxide.