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

Abstract

Zirconia and 10%, 20%, and 30% cerium-doped zirconia nanoparticles (ZCO), ZCO-1, ZCO-2, and ZCO-3, respectively, were prepared using auto-combustion method. Binary nanohybrids, ZrO2@rGO and ZCO-2@rGO (rGO = reduced graphene oxide), and ternary nanohybrids, ZrO2@rGO@MoS2 and ZCO-2@rGO@MoS2, have been prepared with an anticipation of a fruitful synergic effect of rGO, MoS2, and cerium-doped zirconia on the tribo-activity. Tribo-activity of these additives in paraffin oil (PO) has been assessed by a four-ball lubricant tester at the optimized concentration, 0.125% w/v. The tribo-performance follows the order: ZCO-2@rGO@MoS2 > ZrO2@rGO@MoS2 > ZCO-2@rGO > ZrO2@rGO > MoS2 > ZrO2 > rGO > PO. The nanoparticles acting as spacers control restacking of the nanosheets provided structural augmentation while nanosheets, in turn, prevent agglomeration of the nanoparticles. Doped nanoparticles upgraded the activity by forming defects. Thus, the results acknowledge the synergic effect of cerium-doped zirconia and lamellar nanosheets of rGO and MoS2. There is noncovalent interaction among all the individuals. Analysis of the morphological features of wear-track carried out by scanning electron microscopy (SEM) and atomic force microscopy (AFM) in PO and its formulations with various additives is consistent with the above sequence. The energy dispersive X-ray (EDX) spectrum of ZCO-2@rGO@MoS2 indicates the existence of zirconium, cerium, molybdenum, and sulfur on the wear-track, confirming, thereby, the active role played by these elements during tribofilm formation. The X-ray photoelectron spectroscopy (XPS) studies of worn surface reveal that the tribofilm is made up of rGO, zirconia, ceria, and MoS2 along with Fe2O3, MoO3, and SO42− as the outcome of the tribo-chemical reaction.

2D graphene/FeOCl heterojunctions with enhanced tribology performance as a lubricant additive for liquid paraffin

“…This behaviour can be explained by the key role that different additives play in the formation of tribochemical films ( in situ ), which prevented proximal surface contact and was essential for reducing friction on the proximal surface. 3 However, the presence of oxygen-containing functional groups, structural ripples, and high shear resistance due to hydrogen bonding between adjacent atomic layers in G had a negative impact on the tribological properties. 43 Thus, the obtained results indicated that CM G/FeOCl had better lubrication performance than G, FeOCl and PM G/FeOCl, which may be due to the synergistic lubricating role of G and FeOCl.…”

“…The absorbance of different dispersions was monitored at different time intervals from 0 to 48 h at a wavelength of 350 nm. 3,38 Fig. 4a displays the dispersion of the proposed G, FeOCl and G/FeOCl lubricant samples at 0.20 wt% in LP.…”

“…As mobility continues to increase, these numbers will no doubt skyrocket, posing huge challenges for sustainable transport. [1][2][3] Therefore, reducing friction and wear can not only improve the service life of machinery but also improve the energy efficiency. Lubricants are thought to reduce friction and wear by forming a stable lubricating lm between the surfaces of the friction pairs.…”

Characterization and Modeling of Nano Wear for Molybdenum-Based Lubrication Layer Systems

“…As soon as the top layer is worn away, a new oxide layer is regenerated from the Mo-reservoir by tribo-oxidation. In addition to the contact pressure, the contact temperature, and the surrounding media, the contact surface is also decisive for tribo-oxidation [ 3 , 4 , 5 , 6 ].…”

Oxygen-Driven Growth Regulation and Defect Passivation in Chemical Vapor Deposited MoS2 Monolayers

“…However, since this sample (sample C) is grown under S-rich condition (the Mo:S ratio is estimated to be 1:2.4 from the XPS spectra as shown in Table S1), we observed presence of sulfur oxide and sulphate from the XPS S 2s core-level spectrum (Figure S2(b)). [1][2] The peak at 533.1 eV seen in the oxygen 1s core level spectrum [figure S2 (c in the sample can be identified using the Raman spectrum by appearance of an intense peak at 820 cm -1 . 3 The Raman spectra clearly shows no such presence of MoO3 in our MoS2 samples.…”