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Dielectric property of Cu powder/polymer composites

Sonoda K., Moriya Y., Jantunen H.

Materials Science Poland

2011

Vol. 29, No. 1

63--69

Dielectric property of Cu/polymer thermoplastic composites was measured in high frequencies up to 1 GHz. Generally relative permittivity and dielectric loss of the composites increased as the increasing metal inclusion loading as the percolation theory predicts. The incorporation of the copper inclusion with surface antirust layer raised relative permittivity of the composite from 2.3 to 21.3 at the loading level of 39.3 vol. % at 500 MHz. When copper oxide layer was introduced to the filler surface, estimated increase of relative permittivity was ca. 25 %. Since metal composites with ordered structure would raise the relative permittivity of the composites, the cause of this increase in relative permittivity in the present study can be attributable to reduced compatibility of the filler surface and the polymer matrix which lowers randomness of particle distribution. On the other hand, dielectric loss of the composite with surface oxidized Cu powder was increased by ca. 50 % compared to that of the anti/rusted powder composite. This would be caused by skin effect that part of the induced current flows through the less conductive surface oxide layer.

Surface durability of steel rollers lubricated by fresh and used engine oils in comparison with gear oil

Ishibashi A., Sonoda K., Sunagawa Y., Shoji R.

International Journal of Applied Mechanics and Engineering

2004

Vol. 9, no spec.

79-85

The lubricating oil used for the gasoline engine of passenger cars has been exchanged for a fresh oil after running a distance in the range of 3.000 to 10.000km, in Japan, in most cases. In the present investigation, used engine-oils were obtained by two different methods; (1) the oils were gathered at a car service centre, or (2) produced using test cars and fresh engine oils. The fresh and used engine-oils were chemically analysed and the amounts of nine elements (S, Cl, P, Zn, Pb, Mo, Fe, Al, Ca) in the oils were compared with those of a gear lubricating oil. Using a four ball tester, scoring load for the test oils were measured and then surface durability tests were conducted using a two roller testing machine. Many pits occurred at a Hertzian contact pressure of 1.000MPa on the steel rollers with a hardness of 180HB when a fresh engine-oil or the gear oil was used for lubricating the rollers. However, not a single pit occurred at the same contact pressure up to 10 million rotations when the used engine-oil was used. The reason for the higher surface durability was explained using the results of the chemical analyses and scoring tests.