Synthesis, Characterization, and Tribological Evaluation of TiO₂-Reinforced Boron and Nitrogen co-Doped Reduced Graphene Oxide Based Hybrid Nanomaterials as Efficient Antiwear Lubricant Additives

Abstract

The 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.

Temperature‐driven wear behavior of Si3N4‐based ceramic reinforced by in situ formed TiC0.3N0.7 particles

“…In addition, tribochemical reaction is another important factor to improve the wear behavior of ceramics . As shown in Figure F, there is a transferred film covered on the matching ball, and its main components are Ti and O elements by EDS analysis.…”

Synergistic Tribo-Activity of Nanohybrids of Zirconia/Cerium-Doped Zirconia Nanoparticles with Nano Lamellar Reduced Graphene Oxide and Molybdenum Disulfide

“…The nanosheets appear to be quite transparent with little folding at the edges. The interlayer distance of (002) plane of rGO was obtained as 0.339 nm [30,42,43]. The HR-TEM image of MoS 2 nanosheets showed a layered structure with weak van der Waals-type of forces existing in between the layers.…”

“…The HR-SEM images of rGO nanosheets, ZCO-2 nanoparticles, the nanohybrid ZCO-2@rGO, MoS 2 nanosheets, and the ternary nanohybrid, ZCO-2@ rGO@MoS 2, are presented in Figure 2a-e, respectively. Figure 2a exhibits a lamellar structure for rGO [42,43]. The crumpled and transparent sheets of rGO with folded edges are visible.…”

“…The nanocomposite of WS 2 with graphene was reported to yield better tribological results than its constituents [41]. A nanohybrid of boron, nitrogen, co-doped graphene with titania was found to reduce friction, wear tremendously, and enhance load-carrying properties [42]. Recently, reinforcement of reduced graphene oxide (rGO) by magnesium-doped zinc oxide showed wonderfully exalted tribological behavior over pure zinc oxide [43].…”

Sulfur-Doped Alkylated Graphene Oxide as High-Performance Lubricant Additive

“…Since the excessive active sulfur in organic compounds could poison the ternary catalyst of emission reduction system while serving on the piston ring and cylinder wall, which has been resulting to serious environment pollution, the coming mandatory standard from the International Lubricant Standardization and Approval Committee (ILSAC) [3] requires the sulfur content of lubrication oil should be less than 0.5 wt%, for the reason that the higher sulfur content in lubricant could deteriorate the quality of engine exhaust gas [4]. In order to resolve the problem, many strategies including the organic friction modifier such as sulfur-free alkyl-cyclens [5], quinolinium salts [6], and nanomaterial anti-wear additives like BN co-doped graphene [7], SiC@graphene [8], crumpled graphene [9], and graphene nanoscroll [10] have been developing to reduce or remove the sulfur content of lubrication oils. However, the above developing methods still need a long time to verify the practical lubrication effect, environment factor, safety, and other aspects to finally confirm the actual application results.…”