Experimental studies reveal that the simultaneous addition of zinc dialkyl dithiophosphates\n(ZDDPs) and multi-wall carbon nanotubes (MWCNTs) to a poly-alpha-olefin base oil strongly reduces\nwear. In this paper, it is shown that MWCNTs promote the formation of an anti-wear (AW) layer on\nthe metal surface that is much thicker than what ZDDPs can create as a sole additive. More importantly,\nthe nanotubesâ?? action is indirect, i.e., MWCNTs neither mechanically nor structurally strengthen\nthe AW film. A new mechanism for this effect is also proposed, which is supported by detailed\ntribometer results, friction track 3D-topography measurements, electron diffraction spectroscopy\n(EDS), and Raman spectroscopy. In this mechanism, MWCNTs mediate the transfer of both thermal\nand electric energy released on the metal surface in the friction process. As a result, this energy\npenetrates more deeply into the oil volume, thus extending the spatial range of tribochemical reactions\ninvolving ZDDPs.
Loading....