AVS 51st International Symposium
    Vacuum Technology Tuesday Sessions
       Session VT-TuP

Paper VT-TuP4
Adsorption System Controlled with Surface Roughness for Smooth Sliding in a Vacuum

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: A. Kasahara, National Institute for Materials Science, Japan
Authors: A. Kasahara, National Institute for Materials Science, Japan
M. Goto, National Institute for Materials Science, Japan
Y. Pihosh, National Institute for Materials Science, Japan
M. Tosa, National Institute for Materials Science, Japan
Correspondent: Click to Email
Friction measurement was measured out on typical vacuum materials as Copper sheets and type 304 austenitic stainless steel sheets after such surface treatments as chemical polishing or electrochemical buffing. We have shown that the materials with surface roughness around 100nm can offer as smooth sliding in a vacuum as at an atmospheric pressure with a developed vacuum friction measurement system based on Bowden-Leben type system. This smooth sliding may arise from absorption gas layer as lubricant kept in hollows of surface nanoscopic asperities. We accordingly estimated adsorption gases for lubrication by decrease in sliding load with the friction measurement system to study the effect of surface roughness on the adsorption gases. We found existence of low friction coefficient about 0.03 on a Cu sample with surface roughness about 90nm under the load of 0.1N at an atmospheric pressure. The load with over about 0.2N and under about 0.05N also showed increasing friction coefficient at an atmospheric pressure. We can understand change of friction coefficient by using Stribeck-Diagram. The diagram shows the existence of regions indicating solid lubrication, boundary lubrication, mixture lubrication and hydrodynamic lubrication by assuming adsorption layer as lubricant on nano surface roughness. It is therefore concluded that the surface with 100nm roughness exhibiting similarly low friction in a vacuum as at an atmospheric pressure is ideal modified surface for residual adsorbed gases layer system to act as fluid lubricant.