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Synthesis, Characterization, and Tribological Evaluation of TiO2‑Reinforced Boron and Nitrogen co-Doped Reduced Graphene Oxide Based Hybrid Nanomaterials as Efficient Antiwear Lubricant Additives
journal contribution
posted on 2016-04-20, 00:00 authored by Vinay Jaiswal, Kalyani, Sima Umrao, Rashmi B. Rastogi, Rajesh Kumar, Anchal SrivastavaThe microwave-synthesized
reduced graphene oxide (MRG), boron-doped reduced graphene oxide (B-MRG),
nitrogen-doped reduced graphene oxide (N-MRG), boron–nitrogen-co-doped
reduced graphene oxide (B–N-MRG), and TiO2-reinforced
B–N-MRG (TiO2–B–N-MRG) nanomaterials
have been synthesized and characterized by various state-of-the-art
techniques, like Raman spectroscopy, powder X-ray diffraction, scanning
electron microscopy (SEM) with energy-dispersive X-ray spectroscopy,
high-resolution transmission electron microscopy, and X-ray photoelectron
spectroscopy. Furthermore, the tribological properties of prepared
nanomaterials as antiwear additives in neutral paraffin oil have been
evaluated using a four-ball machine at an optimized additive concentration
(0.15% w/v). The tribological parameters, like mean wear scar diameter,
coefficient of friction, and wear rates, revealed that these nanomaterials
have potential to be developed as environmentally friendly sulfated-ash-,
phosphorus-, and sulfur-free antiwear lubricant additives. The friction-
and wear-reducing behavior of MRG increased upon successive doping
of nitrogen, boron, and both nitrogen and boron. Among these additives,
B–N-co-doped MRG shows superior tribological behavior in paraffin
base oil. Besides this, the load-carrying properties of B–N-co-doped
MRG have significantly improved after its reinforcement with TiO2 nanoparticles. A comparative study of the surface morphology
of a lubricated track in the presence of various additives has been
assessed by SEM and contact-mode atomic force microscopy. The X-ray
photoelectron spectroscopy studies have proved that the excellent
lubrication properties of TiO2–B–N-MRG are
due to the in situ formation of a tribofilm composed of boron nitride,
adsorbed graphene layers, and tribosintered TiO2 nanoparticles
during the tribocontact. Being sulfur-, halogen-, and phosphorus-free,
these graphene-based nanomaterials act as green antiwear additives,
protecting interacting surfaces significantly from wear and tear.
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Keywords
powder X-ray diffractionenergy-dispersive X-ray spectroscopyantiwear additivesN-MRGsulfur-free antiwear lubricant additivestribosintered TiO 2 nanoparticlesMRGX-ray photoelectron spectroscopy studiesgraphene oxidegraphene-based nanomaterials actTiO 2 nanoparticlesB-MRGboronparaffin base oilSEMNitrogen co-Doped Reduced Graphene Oxidescanning electron microscopytransmission electron microscopyEfficient Antiwear Lubricant AdditivesX-ray photoelectron spectroscopytribological
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