Sliding electrification of Teflon by metals

• The electrification of a system consisting of a metal and Teflon (polytetrafluoroethylene) has been investigated in vacuum under relative motion. A plane strip of Teflon was moved in relation to a metal electrode connected to an electrometer, which permitted the electrification charge to be continuously recorded. The electrification current was found to be closely proportional to the velocity, and it was practically independent of the radius of curvature of the tip of the electrode. The normal force was also varied, and the linear charge was found to be proportional to the square root of this force. Electrodes of Al, Au, Cu, Dural, Mg, Ni, and Pt were used, and the charge deposited was found to be linearly dependent on the metal work function, except for a large anomalyin the case of Cu. For a given metal the charge was shown to be closely proportional to the area swept out by the electrode on the insulator surface. The linear dependence of charge on metal work function and the short charging time (0.06 s) observed indicate that electrons from the metal fill empty surface states in the insulator up to a level corresponding to the Fermi level of the metal. The surface-state density of Teflon was found to be 7x 1010 eV-l cm-2.

Subject headings

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Keyword

Charge transport

electrification

sliding

PTFE

Teflon

metals

work function

surface states

Fermi level

Publication and Content Type

ref (subject category)

art (subject category)