Ian Wark Research Institute,
University of South Australia, Mawson Lakes SA 5095 Australia.
Langmuir,(in press)
Abstract
Friction force measurements between a silica sphere
and a titanium dioxide wafer in electrolyte solutions
were made with an Atomic Force Microscope.
The effect of electrical double layer interactions
on the adhesion and friction force were investigated
as a function of pH.
In contrast to friction measurements in air,
conducting the study in aqueous solution has allowed
the surface separation, adhesion and applied force
to be controlled independently.
Friction was found to be dependent only on the intrinsic force.
Friction was seen to be independent of pH.
Using a force law fitted to the measured data,
the separation as a function of intrinsic force was
likewise found by theoretical calculations to be independent of pH.
It was concluded that friction was solely dependent upon separation
and that the effect of applied force
and electrical double layer interactions served merely
to change the separation. In addition, it was proposed
that a single layer of unbound water molecules effectively
lubricated the surfaces.
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