Enhanced Tribological Performance of Silicon Nitride-Based Materials by Adding Carbon Nanotubes

摘要

In the search for materials that can withstand the new demanding tribological conditions, carbon nanotubes containing ceramic composites emerge as a promising alternative in gasoline direct injection systems. To explore this prospect, the tribological properties of dense good-dispersed multiwalled carbon nanotubes (MWCNTs) containing silicon nitride (Si_3N_4) nanocom-posites were investigated using a reciprocating ball-on-plate configuration mated against Si_3N_4 balls under lubrication with isooctane. The friction coefficient and the wear resistance of the materials were evaluated as a function of the MWCNTs content (up to 8.6 vol%) and the applied load (50-200 N). For the nanocomposites both the friction coefficient and the wear volume decreased in about 40% and 80%, respectively, as compared with the monolithic material. This enhanced tribological performance of the nanocomposites was attributed to the special role played by nanotubes, acting as solid lubricant and modifying, at the same time, the stress field distribution at the contact, thus notably enhancing the wear resistance at high loads.