Zinc oxide-coated high-performance bearings developed

1 min read

A research group from the National Institute for Materials Science (NIMS) has developed a coating technique using an environment-friendly, low-friction zinc oxide (ZnO) material. When the researchers coated the bearing balls with the ZnO material, its low frictional characteristics were maintained and the friction coefficient of the bearing was reduced by approximately one-third.

To address worsening global environment/energy issues, it is important to reduce friction occurring in drive mechanisms including engines in terms of energy saving. However, because the mechanically driven part in an engine becomes extremely hot, friction reduction technology applied in such an environment must also be heat resistant. The researchers focused on ZnO, capable of both reducing friction and resisting heat, and identified its friction reduction mechanism at the nano level. They then developed a basic technique to apply a low-friction ZnO coating by controlling the crystal orientation of ZnO.

In efforts to put the technique to practical use, it was applied to reduce the friction level of commercially-available, high-performance bearings to an even further extent. The team developed the technique for applying ZnO coating to bearing balls while controlling the crystal orientation of the ZnO material by rotating bearing balls in cage-shaped sample holders. As a result, the researchers succeeded in reducing the friction coefficient of the bearings by approximately one-third. In addition, the resulting bearings were integrated into a small jet engine and a 1% reduction in fuel consumption was achieved.

Furthermore, the researchers worked to miniaturise generators to be used in times of emergency when procurement of fuel is difficult. In this effort, they succeeded in developing a small jet engine generator equipped with ZnO-coated bearings. Weighing about 40kg, it can be carried by two adults and can produce 8,000W of power, which can approximately cover the amount of power consumed by two households.

The low-friction ZnO coating is expected to be applicable not only to bearings but also to any mechanically driven parts that require energy savings and friction reduction, given that the coating is usable in a range of conditions: from room temperature to high temperature, in oil, in vacuum and in atmosphere.