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In Situ Synthesis of Graphene Nitride Nanolayers on Glycerol-Lubricated Si3N4 for Superlubricity Applications

: Long, Y.; Kuwahara, T.; Barros Bouchet, M.-I. de; Ristić, A.; Dörr, N.; Lubracht, T.; Dupuy, L.; Moras, G.; Martin, J.M.; Moseler, M.


ACS applied nano materials 4 (2021), No.3, pp.2721-2732
ISSN: 2574-0970
Deutsche Forschungsgemeinschaft DFG
INST 39/963-1 FUGG
Journal Article
Fraunhofer IWM ()
silicon nitride; graphene nitride layers; tribochemistry; boundary lubrication; superlubricity

The 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 (μ < 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.