Solid Lubricant Properties of Catalytically Grown Carbon Nanotubes

Solid lubricant properties of carbon nanotubes catalytically deposited by microwave plasma CVD using methane and hydrogen gaseous mixture have been investigated by means of ball-on-disk type friction testing. Carbon nonotubes with various crystallinity were deposited by changing microwave power and bias voltage onto silicon substrate. Nickel was used as a catalyst and coated on the substrate by DC sputtering before deposition. SEM and Raman spectroscopy were employed to examine carbon nanotubes. In friction testing, a bearing steel ball slid on the substrate coated with carbon nanotubes or covered with vapor grown carbon fibers used as a reference carbon material. Friction force was measured in air containing water vapor, dry nitrogen and vacuum. As a result, low friction has resulted from the carbon nanotubes with fewer defects, in particular, in water-free atmosphere such as dry nitrogen and vacuum. Cemented carbide substrate has improved the adhesion of carbon nanotubes, and lower friction coefficient below 0.1 was consequently attained.