Hajime Shiki

Parametric Study on Growth of Carbon Nanocoil by Catalytic Chemical Vapor Deposition

Carbon nanocoils (CNCs) were synthesized by the catalytic pyrolysis of acetylene over a mixture of Fe and SnO2 particles in a chemical vapor deposition (CVD) apparatus. The effects of reaction temperature, the composition of Fe and SnO2 in the catalyst, and the ratio of acetylene (C2H2) to helium (He) gas were examined. An optimum output was obtained when the Fe/SnO2 ratio was 2/1, the flow rates of C2H2 and He gases were 150 and 700 sccm, respectively, and the reaction temperature was 700°C. Under these conditions, the CNCs were of 80% purity, with average coil diameters of 750 nm, fiber diameters of 300 nm and pitches of approximately 750 nm. The CNC yield weighed up to 60 times that of the catalyst in 10 min.

Preparation of Powdery Carbon Nanotwist and Application to Printed Field Emitter

In the present study, an automatic production system with sequencer control for the synthesis of carbon nanofibriform based on catalytic CVD using a substrate was developed. The carbon nanotwist (CNTw), which is one of the helical carbon nanofibers, was then synthesized in powdery form with an Ni–SnO2-composed catalyst. The production rate was 5 400 times that of the conventional CVD system and Ni–Cu–In2O3 catalyst. The powdery CNTw was easily scraped off the substrate, then pasted with organic binder, and printed by a squeegee method on ITO glass substrate for an electron field emitter. The field emission performance was found to be better than that of the directly grown CNTw film in conventional CVD with Ni–Cu catalyst.

Low-Temperature Sintering of Indium Tin Oxide Thin Film Using Split Gliding Arc Plasma

The feasibility of sintering on indium tin oxide (ITO) thin film by a mesoplasma under open atmosphere was investigated. An ITO film of 300 nm thickness was prepared on a glass substrate by spin coating an ITO nanoparticle suspension. A mesoplasma of a gliding arc was irradiated on the ITO film. The plasma generated a temperature of 160 °C at the irradiation position. By utilizing nitrogen (N2) gas as the plasma working fluid, the sheet resistance was effectively reduced, compared with the use of air. A small amount of hydrogen (H2) added was more effective. A conventional gliding arc (GA) caused film damage owing to the appearance of an arc spot on the treated film, although a split gliding arc (S-GA) was effectively treated without arc spot appearance and damage. A silica binder was added to the ITO nanoparticle suspension in order to increase film adhesion and conductivity by increasing the film density. A sheet resistance of 1.9 kΩ/sq was obtained at an optimum H2 concentration (1.0 vol %) in N2 and a silica binder concentration (12.5 vol %), which was similar to the resistance obtained by sintering the film on a hot plate at 300 °C.

Removal of Machine Oil from Metal Surface by Mesoplasma Jet under Open Atmosphere

An attempt was made to employ the plasma-energized jet (PEN-jet) generated by pulsed arc discharge, one of the atmospheric-pressure mesoplasmas, for removal of machine oil from the surface of electrically-grounded aluminum (Al) alloy substrate under open atmosphere. Three types of nozzle configurations were examined; a metal nozzle, ceramic nozzle, and electrically-floated metal nozzle. Electric input power to the pulsed arc plasma discharge was 700 W constant. First, free-burning of the PEN-jet was observed as a function of air gas flow. When the PEN-jets were irradiated to the clean substrate, the PEN-jet with the metal nozzle caused substrate damage by the arc spot due to transferring arc discharge. Then the PEN-jet with the ceramic nozzle was irradiated to the oily substrate. The adhesion strength of sealant and water contact angle of the treated surface were then measured. As a result, these values of the oily substrate treated by the PEN-jet were almost the same as those of clean substrate. The treated surface was analyzed by Fourier transform infrared spectroscopy, Raman spectroscopy, and reflectance spectroscopy. Their spectral profiles clearly indicated oil removal from the surface by PEN-jet.