AVS 50th International Symposium
    Vacuum Technology Wednesday Sessions
       Session VT-WeP

Paper VT-WeP10
Adsorption Force Control with Surface Roughness Modification for Smooth Sliding in a Vacuum

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

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
T. Oishi, National Institute for Materials Science, Japan
M. Tosa, National Institute for Materials Science, Japan
Correspondent: Click to Email
Vacuum friction measurement system based on Bowden-Leben type system has been successfully developed that can evaluate sliding friction force under changing load from 1.96N to 0.98mN and under changing atmospheric pressure from 1E+5 Pa to 1E-8 Pa. Friction measurement was carried out on typical vacuum materials as 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. This smooth sliding may arise from absorption gas as lubricant kept in hollows of surface nanoscopic asperities. We accordingly tried to estimate absorption force by decrease in sliding load with the friction measurement system to study the effect of surface roughness on adsorption force and the contribution to smooth sliding in a vacuum. We found existence of absorption force about 20mN on a sample with surface roughness about less than 600nm, at an atmospheric pressure. The sample with the surface roughness under 40nm also showed adsorption force below 0.98mN in a vacuum, while sample with the surface roughness around 100nm showed higher adsorption force over 0.98mN even in a vacuum. The surface roughness can also slow desorption rate of absorption gas layer and keep friction small in a vacuum. 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 trapping adsorbed gases strongly to act as vacuum lubricant. The surface roughness about 100nm will be a good candidate surface for smooth movement in a vacuum.