Augmentation in Tribological Performance of Polyalphaolefins by COOH-Functionalized Multiwalled Carbon Nanotubes as an Additive in Boundary Lubrication Conditions

Abstract

This current study emphasized the tribological performances of COOH-functionalized multiwalled carbon nanotubes (MWCNTs) dispersed in two different grades of polyalphaolefins (i.e., PAO 4 and PAO 6). The friction and wear properties have been estimated using SRV 5 tribometer with “ball on disc” configuration. Prior to tribo-testing, MWCNTs were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), and Fourier transform infrared spectroscopy (FTIR). The varying dose of MWCNTs (0.025-0.15 wt.%) was incorporated into both PAO base oils to obtain the optimized lubrication behaviour. The test results revealed that PAO 4 exhibited a reduction in friction coefficient (~27%) and wear volume (~88 %) at a dose of 0.05 wt.% and 0.025 wt.% MWCNTs, respectively. However, in PAO 6, the minimum coefficient of friction and wear volume was obtained at a concentration of 0.075 wt.% and 0.05 wt. % of the additive. The results evidenced that PAO 6 based nanolubricants demonstrated the best frictional characteristics while attained the best anti-wear performance with PAO 4 based nanolubricants. For the better unveiling of the lubrication mechanism of MWCNTs, worn surfaces were characterized using various analytical techniques such as scanning electron microscopy (SEM), scan probe microscope (SPM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron microscopy (XPS).

Tribological evaluation of PAO 100 oil‐based lithium greases with chemically functionalized nanoadditives

“…Furthermore, all of the COOH-MWCNT diffraction peaks are completely superimposed with the JCPDS reference code 00-008-0415, indicating that MWCNT nanomaterials have crystalline and hexagonal graphitic structures. 15 The FTIR spectra of chemically treated LaF 3 with oleic acid nanomaterials are shown in Figure 2c. The peak at 577 cm À1 was attributed to the characteristic stretching vibration of the La-F bond.…”

“…14 Similarly, in the presence of functionalized MWCNTs, the lubrication behaviour of PAO 4 and PAO 6 was significantly improved. 15,16 Due to their relatively low hardness, good resistance to thermal and chemical attack, high melting point and hexagonal crystal structure, the rare earth compound-based nanoparticles demonstrated significant potential as an additive in various lubricating oils to reduce friction and wear. Lanthanum trifluoride (LaF 3 ), a rare earth compound-based nanoparticle, has demonstrated outstanding tribological performance in lubricating oil and grease, as well as coatings.…”

“…The tribological performance of polypropylene glycol (PPG 2000) enriched with (0.025 wt%) functionalized MWCNTs improved significantly 14 . Similarly, in the presence of functionalized MWCNTs, the lubrication behaviour of PAO 4 and PAO 6 was significantly improved 15,16 . Due to their relatively low hardness, good resistance to thermal and chemical attack, high melting point and hexagonal crystal structure, the rare earth compound‐based nanoparticles demonstrated significant potential as an additive in various lubricating oils to reduce friction and wear.…”

A review of advances in tribology in 2020–2021

“…Nanomaterials are effective lubricant additives, such as lanthanum borate nanospheres (LBN) [127], core-shell nanocomposites [128], 2D layered -zirconium phosphate (-ZrP) nanosheets intercalated with different amines [129], novel palygorskite nanoplatelets [130], biocarbon-based magnesium silicate hydroxide nanocomposite [131], COOH-functionalized multiwalled carbon nanotubes [132], and nano-PTFE particles [133], etc.…”

Synthesis of Eco-Friendly Carbon Dots as Self-Repairing Additives of Polyalphaolefin by Means of a Green Solvation Effect

“…Luckily, the inorganic additives of nanomaterials are expected to be excellent additives for PAO because of their unique rolling, mending, and polishing effects and strong film-building ability by sintering and deposition. So far, various nanomaterials, such as metals, metal oxides, metal sulfides, metal salts, boron nitride, graphene, carbon nanotubes, carbon dots (CDs), and composites, have been used as additives of PAO with splendid performance. − Although many nanomaterials are eco-friendly according to their element compositions, there are still two issues limiting their practical application. The morphology and sizes of many nanomaterials are irregular and diverse, which is detrimental to building uniform lubricating films on rubbing surfaces .…”