City University of Hong Kong
Lubricant additives react more rapidly at higher temperatures, thus forming a tribofilm that grows more rapidly as the wear rate increases. This is illustrated for chlorine-, sulfur- and phosphorus-containing compounds and our goal is to understand the relationship between the surface chemistry of the lubricant additives and their tribological properties. The additive surface chemistry is explored both in ultrahigh vacuum and at higher pressures to measure film growth rates and to identify the nature of the surface films.
This strategy is extended to examining boundary lubrication in current-carrying tribocontacts, where heat is generated both by frictional and Ohmic heating. In this case, lubricants are required that react more slowly with increasing interfacial temperature and these effects are illustrated by examining the surface tribochemistry of mixtures of water vapor and carbon dioxide, which are used as vapor phase lubricants for copper electrical brushes.
Finally, in order to further understand frictional properties of reactively deposited tribofilms, evaporated and reactively grown thin films are investigated in ultrahigh vacuum where the tribological properties are measured using an ultrahigh vacuum tribometer. This allows the effect of film thickness on friction to be explored and the shear properties of tribofilms to be investigated as a function of contact pressure.
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Event: |
MEEM Seminar 0809_003 |
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Date: |
15 July 2008 (Tuesday) |
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Time: |
10:30 am - 12:00 noon (Tea reception at 10:00 am) |
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Venue: |
Room B6605 (FSE Conference Room) |
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Speaker: |
Professor Wilfred T. Tysoe |
Wilfred Tysoe is a Distinguished Professor of Chemistry at the University of Wisconsin-Milwaukee. He received his B.Sc. in Chemical Physics at the University of Manchester, England after which he spent a year teaching Chemistry and Physics in Ghana, Africa. He then obtained an M.Sc degree at the University of Sydney, Australia following which he held the position of Senior Scientist at the Plessey Company in England. He then went on to receive his Ph.D. degree in 1982 in Physical Chemistry at the University of Cambridge, England and worked as a post-doctoral researcher at the University of California, Berkeley, before moving to his present position at the University of Wisconsin-Milwaukee in 1984. His research interests focus on chemical properties at surfaces with particular emphasis on understanding catalytic reactions both in ultrahigh vacuum and under realistic conditions and in the area of tribology to understand the interplay between lubricant chemistry and the resulting frictional and wear properties of reactively formed tribological films. He is an Editor in Chief of Tribology Letters, which he co-founded about ten years ago. He is a member of the American Chemical Society, the American Vacuum Society and the Society for Tribologists and Lubrication Engineers (STLE), for which he serves on the publications committee and is a co-contributor to the "Cutting Edge" column in the STLE magazine, Tribology and Lubrication Technology. He has published over 200 papers in scientific journals and presented over 200 talks.
Enquiry: MEEM General Office (Tel: 2788 8420 Email: mego@cityu.edu.hk )