Yoshihiko Itoh

Tribology of carbonaceous films formed by ion-beam- assisted deposition of organic material☆

Abstract By combining the vapour deposition of a silicone oil (pentaphenyltrimethyltrisiloxane) and simultaneous energetic ion irradiation, carbonaceous films (i-silicone films) 0.1-0.3 μm thick were coated on disc samples of hardened SUJ2 (AISI 52100). As the ions for irradiation, 1.5 MeV Ar+, 400 keVTi+ were used. The frictional properties of the i-silicone coated disc, in particular the dependence of the friction coefficient μ on humidity, were tested with a pin-on-disc method using a hardened SUJ2 pin. All the i-silicone coatings prepared by using the three ion beams exhibited similarly low values of μ−0.05 in ambient atmosphere. In both air and nitrogen gas the i-silicone coating exhibited a low value of μ≈0.05 for a relative humidity range from 70% to 20%, the lowest humidity available. On the contrary, diamond-like carbon prepared by plasma- enhanced chemical vapour deposition displayed a value of μ≈0.2 for the same humidity range. In dry nitrogen, both the i-silicone and the diamond-like carbon exhibited an extremely low value of μ⩽0.02. Reasons for the moisture-insensitive frictional properties of i-silicone and features of the ion-beam-assisted deposition coating process of organic materials are discussed.

Tribological properties of metals modified by ion-beam assisted deposition of silicone oil

Silicone oil vapor deposition and Ar + ion irradiation can form an adhesive carbonaceous film on a steel substrate. The friction coefficient μ of the coated substrate is found to be very low for sliding against a steel ball both in air (μ ∼ 0.04) and in N 2 gas (μ 3 –1.5 × 10 4 cycles for a film 0.15 μm thick. X-ray photoemission spectroscopy, infrared reflection spectra, and Raman measurements indicate that the film mainly consists of amorphous carbon containing Si and O.

Formation of carbon films by ion-beam-assisted deposition

Abstract A variety of hard adhesive carbon-rich films can be formed at low temperatures by ion-beam-assisted deposition (IBAD) processing of organic materials, i.e. by vapor deposition of organic materials combined with simultaneous high energy ion irradiation. These films are hydrogenated amorphous carbon (diamond-like carbon) contaminated with other elements such as Si or O, depending on the organic precursors used. They generally exhibit good solid lubrication. In particular, films produced from siloxane compounds ( i -silicone films) exhibit a coefficient μ of friction as low as 0.05 in a humid atmosphere as well as in moisture-free environments. The moisture-insensitive low friction of i -silicone films results from the fact that they contain silicon. Use of a chemically active ion such as Ti + in the IBAD process contributes to enhanced adhesion. The i -silicone films produced by IBAD processing using a low energy ion beam of 30 keV N 2 + contain a significant amount of nitrogen and exhibit values for μ of less than 0.1 in humid air.

Low-temperature oxidation of particulate matter using ozone

Low-temperature oxidation of particulate matter (PM) was investigated using ozone, which has high oxidation ability. Granular carbon was first used as a model PM to investigate the influential factors for PM oxidation with ozone. The PM collected from diesel exhaust using a diesel particulate filter was then evaluated to determine the oxidation performance of ozone. Carbon was effectively oxidized by ozone at low temperatures less than 573 K and the oxidation rate was larger than ten times that for NO2 at 423 K; however, the oxidation rates were decreased by the thermal decomposition of ozone and reaction with NO as an exhaust gas component. The oxidation rate when using ozone could be calculated with inclusion of these factors using the Arrhenius equation. The PM oxidation characteristics were similar to those for granular carbon. The results indicate that oxidation with ozone is a promising method for low-temperature PM oxidation and optimized performance with ozone could be achieved.

IMPROVING THE WEAR RESISTANCE OF AL-SI ALLOY BY ION IMPLANTATION

The mechanical properties of ion-implanted Al–Si alloy were studied using disk samples of alloy irradiated with Ar + , B + , and N 2 + ions. Knoop hardness of ASTM 336.0 disks increased from 117 to 165 kgf/mm 2 upon N 2 + ion implantation. To measure tribological properties, lubricated ball-on-disk tests were performed using steel balls. The coefficients of friction of ion-implanted disks were higher than those of unimplanted ones. Ion implantation improved the wear resistance of the disks, and in the case of N 2 + ion-implanted disks, the worn volume was smaller than 10 −4 mm 3 . XPS analysis for the N 2 + ion-implanted samples revealed the formation of aluminum and silicon nitride on the sample surface. On the other hand, the cross-sectional image of the ion-implanted surface showed precipitated Si which is held under the implanted N 2 + ions.

NOx Reduction Behavior on Catalysts With Non-Thermal Plasma in Simulated Oxidizing Exhaust Gas

NOx reduction activity in an oxidizing exhaust gas was significantly improved by discharging non-thermal plasma and catalysts (plasma assisted catalysis). We investigated effective catalyst for plasma assisted catalysis in view of hydrocarbon-selective catalytic reduction(HC-SCR). Plasma assist was effective for γ-alumina and alkali or alkaline earth metals loaded zeolite and γ-alumina showed the highest NOx conversion among these catalysts. On the other hand, Plasma assist was not effective for Cu-ZSM-5 and Pt loaded catalyst. The NOx conversion for the plasma assisted γ-alumina decreased by formation of a deposit on the catalyst below 400°C. It is shown that indium loading on γ-alumina improved the NOx reduction activity and suppressed the degradation of the NOx reduction activity at 300°C with plasma assist.

A Concept of Plasma Assisted Catalyst System Using a DeNOx Catalyst for an Automobile Diesel Engine

Through the basic research of the plasma assisted catalyst system using DeNOx catalysts and the gas analysis of the system, its conceptual use for automobile diesel engine applications has been studied. This study has shown that the length between the plasma reactor and the catalyst reactor does not affect the NOx conversion. To obtain an efficient NOx conversion, the plasma should affect both the HC as the reductant and NOx at the same time. In the case of γ-Al 2 O 3 and C 3 H 6 , the main component for NOx reduction was CH 3 CHO generated by the plasma. Under 250 deg. C, the temperature was too low for the γ-Al 2 O 3 to become effective. Therefore, the NOx conversion became low. At 400 deg. C, the NOx conversion became high. However, at 600 deg. C, the CH 3 CHO for reducing NOx was not generated, and the NOx conversion decreased. By using multi-catalysts (Na-ZSM-5, In/Al 2 O 3 and Pt/Al 2 O 3 ), an efficient NOx conversion was obtained under the transient gas temperature conditions similar to those of the automobile exhaust.

Tribology of Carbonaceous Films Formed by Ion Beam Assisted Deposition

By combining vapor deposition of organic compounds and simultaneous energetic Ar+ion irradiation, carbonaceous films were deposited onto substrates of a bearing steel (SUJ2). The organic compounds were benzene, pentaphenylether, poly-(dimethylsiloxane) and pentaphenyl-trimethyl-trisiloxane.All the carbonaceous films produced were amorphous and showed low coefficient of friction less than 0.2 in ambient atmosphere. In particular, the films produced from the siloxane compounds (ion-irradiated silicone films) showed extremely low coefficient of friction less than 0.05. Furthermore, the friction coefficient of the ion-irradiated silicone films was much less sensitive to moisture compared to diamond-like carbon films prepared by plasma-enhanced chemical vapor deposition.Scanning electron microscopy and electron-probe micro-analysis for the pins of SUJ2 revealed that the ion-irradiated silicone films are easily transferred to the surface of the pin during sliding. This fact may be related with the very low friction coefficient for the ion-irradiated silicone films.