Tetsuo Oishi

Lubricative coatings of copper oxide for aerospace applications

Lubricative coatings of copper oxide on a stainless-steel substrate were synthesized by a rf magnetron sputter deposition method with a different gas ratio of oxygen and argon in sputter plasma. The crystal structure of the coatings was analyzed with x-ray diffraction spectroscopy. The friction force of the coating films in atmospheric pressure and in an ultrahigh vacuum (UHV) was evaluated by a vacuum pin-on-disk tribometer with different ball probes. Friction coefficients (μ) as low as 0.03 and 0.05 for a stainless-steel ball were achieved in atmospheric pressure and in an UHV, respectively. A value of μ=0.04 was also realized for a silicon nitride ball both in atmospheric pressure and in an UHV. Surface energy was analyzed by a contact angle measuring method which reveals that the behavior of the frictional properties correspond with that of the surface energy. Since the coatings consist of oxide, they will be applicable to a low-frictional coating with resistance to oxidation for aerospace application...

Frictional Property of Zinc Oxide Coating Films Observed by Lateral Force Microscopy

Zinc oxide coating films were synthesized by a magnetron sputter deposition method on stainless steel substrates. The crystal structure of the films was analyzed with X-ray diffraction spectroscopy. Adhesion and frictional properties were obtained from force curves and lateral force data using atomic force microscopy under an atmosphere and in a vacuum. It was found that the friction coefficient decreased in spite of a marked increase in adhesion force on the film surface with heat treatment at 473 K in a vacuum. It was considered that the film surface energy changed during the heat treatment and affected the frictional properties of the films.

Control of pressure rise in a vacuum chamber by boron nitride and copper composite coating

In order to control pressure rise in a vacuum chamber, a radio-frequency magnetron cosputter deposition system has been developed and boron nitride and copper composite (BN/Cu) film was coated onto the inner surface of a vacuum chamber in the shape of a cylinder. Outgassing rate of the BN/Cu coated chamber was estimated with a pressure rise method to be about 5×10−12 Pa m s−1, which was two orders lower than that of the noncoated vacuum chamber in the same shape as the BN/Cu coated chamber. Mass spectra of the residual gas in the chamber indicated that the outgassing of various gas species, such as hydrogen gas, nitrogen gas, and oxygen gas, were reduced by the BN/Cu coating. These results concluded that the BN/Cu coating could control pressure rise in a vacuum chamber.