Friction of Diamond in the Presence of Water Vapor and Hydrogen Gas. Coupling Gas-Phase Lubrication and First-Principles Studies

Abstract

Nanocrystalline diamond (NCD) has attracted much attention in recent years because of improvements in growth methodologies that have provided increases in both film thickness and growth rate, while preserving the outstanding mechanical properties of diamond material. We provide here some evidence, based on combined experimental and first-principles analyses, that ultralow friction of nanocrystalline diamond in the presence of water vapor is associated with OH and H passivation of sliding surfaces, resulting from the dissociative adsorption of H2O molecules. The presence of these adsorbates (OH and H fragments) keeps the surfaces far apart preventing the formation of covalent bonds across the interface. H-passivated surfaces, resulting from the dissociative adsorption of H2 molecules, appears to be more efficient in further reducing friction than OH-terminated surfaces.

Diamond-like carbon coating under oleic acid lubrication: Evidence for graphene oxide formation in superlow friction

“…These two facts counteract the beneficial impact of the interfacial distance growth. The numerical calculations effectively showed an increase in the friction force for H/OH termination compared to smoothness fully H-terminated interface45 and friction experiments using gas phase lubrication with H 2 gas and water vapour have also corroborated this result46. So, in the light of our new synchrotron data, the model based on the generation of H/OH-terminated a-C surface can be specified with accurate information on the structure of the top layer to explain the superlow friction in mixed/boundary regime with oleic acid.…”

Interfacial Charge Density and Its Connection to Adhesion and Frictional Forces

“…Experiments have shown that lubricant additives containing sulfur or graphene can reduce the friction and wear of iron and steel significantly [23,26,27]. Likewise, friction at diamond interfaces is greatly diminished in the presence of H 2 [28]. To investigate the root cause of these advantageous effects we investigate the influence of these species on ρ redist and E adh at Fe and C interfaces in the second row of Fig.…”

Advances in atomic-scale tribological mechanisms of solid interfaces

“…Bouchet et al [94] investigated the origin of the super-low friction behaviors of smooth nanocrystalline diamond coatings obtained in the presence of OH-and Hcontaining environments, respectively. The ultralow friction is attributed to the formation of H-/OH-terminated carbon surfaces.…”