<i>In Situ</i> Synthesis of Graphene Nitride Nanolayers on Glycerol-Lubricated Si<sub>3</sub>N<sub>4</sub> for Superlubricity Applications
Yun‐Ze Long, Takuya Kuwahara, Maria-Isabel De Barros Bouchet, Andjelka Ristić, Nicole Dörr, A.A. Lubrecht, L. Dupuy, Gianpietro Moras, Jean Michel Martin, Michael Moseler
Abstract
High Resolution Image Download MS PowerPoint Slide 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 (Si 3 N 4 ) 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 Si 3 N 4 . 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 Si 3 N 4 . 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 Si 3 N 4 has a high potential for use in green superlubricity enabled by in situ synthesis of disordered graphene nitride species.