Long, Y.Y.LongKuwahara, T.T.KuwaharaBarros Bouchet, M.-I. deM.-I. deBarros BouchetRistic, A.A.RisticDörr, N.N.DörrLubracht, T.T.LubrachtDupuy, L.L.DupuyMoras, G.G.MorasMartin, J.M.J.M.MartinMoseler, M.M.Moseler2022-03-062022-03-062021https://publica.fraunhofer.de/handle/publica/26697110.1021/acsanm.0c03362The increasing demand for sustainable tribology has accelerated the development of environmentally friendly lubrication solutions such as water or water-related lubricants. Earlier works have reported on water-lubricated sliding of silicon nitride (Si3N4) at high speeds, which can result in a superlow friction (m < 0.01) owing to the formation of hydrodynamic water films on hydrophilic surface layers. Here, combined boundary-lubrication experiments at low sliding speeds and atomistic simulations reveal an alternative superlubricity mechanism for glycerol-lubricated Si3N4. X-ray photoelectron and time-of-flight secondary ion mass spectrometry performed inside and outside the wear track as well as high-resolution mass spectroscopy of the used lubricant strongly suggest that sub-nanometer-thick graphene nitride layers form at the very top of Si3N4. In the accompanying atomistic simulations, glycerol molecules undergo tribochemical decomposition and react with surface-bound nitrogen atoms to form carbon nitrides. Further shearing promotes the formation of 2D graphene nitrides that passivate the ceramic surfaces and induce a superlow friction under boundary lubrication. Thus, glycerol-lubricated Si3N4 has a high potential for use in green superlubricity enabled by in situ synthesis of disordered graphene nitride species.ensilicon nitridegraphene nitride layerstribochemistryboundary lubricationsuperlubricity620journal article