Search

At present, due to the excellent properties of graphene, which can significantly enhance the performance of lubricants, researchers are conducting extensive studies on it. However, the poor dispersion of graphene limits its application in lubrication, which becomes an urgent problem for researchers to solve. Moreover, with the concept of green environmental protection becoming more and more popular, the research on water-based lubricants is of great significance. Therefore, we modify three-dimensional graphene (3DG) by polycarboxylate superplasticizer (PCE) to prepare a water-based lubrication nano-additive with long-term dispersion stability, named PCEG. PCEG nanomaterials can stably disperse in water for more than three months, which effectively solves this problem. Tests show that friction coefficient and wear volume of the lubricant with 0.5 wt% PCEG are reduced by 31.1 % and 23.1 %, respectively, compared to the base fluid at 20 N (2.7 GPa) heavy load conditions. The enhanced lubrication performance is attributed to the fact that PCEG, which has excellent dispersion stability, forms a strong adsorption and continuous dense lubrication film on the friction surface. In addition, it fills and polishes the grooves and pits, thus improving the friction-reduction and anti-wear properties. This study not only greatly solves the problem of poor dispersion stability of graphene and develops a nano-lubricant that is consistently effective under heavy load conditions, but also provides an important reference value for the subsequent development of high-performance and stable graphene-based lubricants. [Display omitted] • PCEG with excellent dispersion stability was prepared. • PCEG as an additive improves by 31.1% and 23.1% in friction and wear. • The modification method used in this study is easy to operate and can be applied in large-scale production. • PCEG provides a reference solution the problem of poor dispersion of graphene in water-based lubricants. [ABSTRACT FROM AUTHOR]

Developing high-performance carbon dot (CD)-based lubricant additives towards non-polar base oils is always challenging because it is an arduous task to gain hydrophobic CDs with high quality. In this work, with the aid of the chemical reaction between hydroxyl groups and lauroyl chloride molecules, the water-soluble CDs-OH derived from the solvothermal method with particularly high particle size regularity were transformed as the oil-soluble CDs-LA by the one-step surface modification process. As expected, the CDs-LA capped by abundant long alkyl chain groups exhibited excellent long-term dispersion stability in non-polar base oil of polyalphaolefin (PAO4) and hence could be served as the additives of PAO4 directly. Under the same test conditions, the tribological performance of CDs-LA was obviously superior to the hydrophobic CDs obtained by the pyrolysis method, implying that the high particle size regularity was beneficial for making full use of the lubrication functions of CDs. Loading 1.7 wt% of CDs-LA made the friction and wear of PAO4 reduced by 32.2 % and 76.4 %, respectively. When the duration prolonged from 20 min to 200 min, the friction reduction of base oil triggered by CDs-LA further enlarged to 46.9 %. The friction-reducing and anti-wear performance of CDs-LA under high loads was also satisfactory. The worn surface analysis results demonstrated that the robust and homogenous boundary lubrication films composed of Fe x O y and CDs have generated on the rubbing surfaces lubricated by CDs-LA/PAO4 dispersion, well accounting for the outstanding friction reduction and wear resistance functions of CDs-LA. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon dots (CDs), a kind of burgeoning carbon-based nanomaterial, were widely used as high-efficiency lubricant additives for promoting the friction-reduction and anti-wear behaviors of green PEG-based lubricating oils. Undoubtedly, advances in CDs-based lubricant additives play a crucial role in enhancing their application prospect and utility value. Recent studies suggest that doping CDs with heteroatoms, especially multiple heteroatoms could remarkably promote their tribological performance. Therefore, the state-of-the-art N, B, and P-co-doped CDs (N,B,P-CDs) with a diameter of approximately 3.8 nm and composed of amorphous structures were synthesized by conveniently "one-step" pyrolyzing the corresponding carbon sources and dopants. Noticeably, the synthetic procedures of N,B,P-CDs were uninvolved in any pre-processing and post-processing techniques, showing favorable large-scale preparation potential. Adding suitable concentrations of N,B,P-CDs, the friction-reduction, anti-wear, and load-supporting functions of PEG200 base oil can be maximally increased by 38.1 %, 86.2 %, and 66.7 %, respectively, showing outstanding tribological performances. In addition, the tribological behaviors of N,B,P-CDs are evidently better than that of N,B-CDs and P-CDs under identical test conditions, exhibiting a multiatomic synergistic lubrication effect. According to the wear track surface analysis results and previous reports, the excellent tribological performance of N,B,P-CDs attributes to their favorable film-forming ability and nano-lubrication effect in the different friction stages. [Display omitted] • Novel N,B,P-CDs-based lubricant additives for PEG200 base oil were synthesized. • N,B,P-CDs as additives showed great anti-friction and anti-wear functions. • N,B,P-CDs possessed good multiatomic synergistic lubrication effect. • N,B,P-CDs have outstanding film-forming and nano-lubrication effects. [ABSTRACT FROM AUTHOR]

In the field of tribology, graphene has become a potential candidate material for lubricating oil and lubricant additives at multiple scales due to their high thermal conductivity and impermeability. In order to further improve the anti-wear and anti-friction properties of graphene, Ni/polydopamine-functionalized graphene composites (Ni/pDA/GR) were successfully prepared by a wet chemical reduction method. In this paper, The GR, pDA/GR, Ni/GR and Ni/pDA/GR were added into the base oil as lubricant additives respectively to explore their lubrication properties. The results showed that the friction coefficient of Ni/pDA/GR group is the lowest, which is about 15 % lower than base oil. Ni/pDA/GR also exhibited good wear resistance in wear tests. At the same time, the optimal concentration of the composite is 0.1 wt% in base oil, and the optimal lubrication load is 5 N. [Display omitted] • Polydopamine was used to modify graphene which is facile and environmental. • Spherical Ni NPs can improve the load-bearing capacity of base oil. • The composite can improve the anti-wear and anti-friction performance of base oil. • We report a facile method to prepare metal-nanomaterial composites. [ABSTRACT FROM AUTHOR]

Spheroidal carbon particles are touted as excellent additives in lubricants for reduction in friction and wear. Herein 50–100 nm-sized spheroidal carbon soot particles with heliocentric graphitic layers are prepared by controlled decomposition of wasted rubber and subsequent heat-treatment of wasted rubber derived soot. Thermogravimetric analysis showed that the on-set degradation temperature of the soot particles was representative of a material constituted by amorphous and crystalline phases complementing well with x-ray diffraction studies. The soot particles are dispersed in an additive-free base oil (BO), and the soot particles added oil was used as a lubricant. At room temperature, a reduction in coefficient of friction (CoF) and wear scar diameter (WSD) of ~9% and 16.55% were recorded. At a higher temperature of 70 °C, a reduction in CoF and WSD of as high as 48.93% and 28.12% were recorded. Based on the observations, it is theorized that the soot particles acted like nano-bearings between the contacting surfaces producing a rolling effect that efficiently reduced friction and wear concerning the contacting surfaces. Also, the dispersion of soot particles improved the viscosity retention of BO at higher temperatures indicating its multifunctional ability. [Display omitted] • 50–100 nm-sized carbon soot particles with sphere-like morphology are prepared from wasted rubber. • Heliocentric graphitic layers constituted the soot particles. • The carbon soot particles had a mixture of crystalline and amorphous characteristics. • The carbon soot particles are dispersed in an additive-free Group-2 dewaxed lubricating oil. • Carbon soot particles are an excellent additive in lubricating oil for considerable friction and wear reduction. [ABSTRACT FROM AUTHOR]

The prime objective of this study was to extend the application of graphene additive in oil solution via investigating the frictional interaction of graphene and ZDDP composite additives in point contact lubrication. Accordingly, 0.05 wt% graphene, 1 wt% ZDDP and their mixtures as additives were added into PAO4 base oil. The ball-on-disk reciprocating experiments were carried out under the load of 30 N, 80 N, 155 N and 310 N. The tribological performance of the single system containing graphene and ZDDP were evaluated separately to compare the tribological property of the composite system containing graphene + ZDDP. The result revealed that the friction coefficient of the graphene/ZDDP composite system was slightly higher compared to PAO4 oil under high load. Whereas the composite system exhibited excellent wear resistance under all loads, reducing the wear rate by 77% in comparison to that of PAO4 oil under a load of 30 N. The reduction in wear is attributed to the formation of the graphene tribofilm and the protective polyphosphate film, which avoided the direct contact with the sliding surface and effectively inhibited the wear of steel materials. [Display omitted] • Graphene/ZDDP composite system shows excellent antiwear performance as a lubricant additive. • The composite system reduces the wear rate by around 77%. • The wear resistance of the composite system is superior to that of the single system under high contact stress. • The introduction of graphene exhibits no positive response to improve the high friction coefficient of ZDDP. [ABSTRACT FROM AUTHOR]

The morphology, thermal stability, phase composition, chemical groups of nanoparticles were characterized, and appropriate thermal process maintains layered structure and weakens the interlayer interaction of the MSH-AHT400. The tribological performances of MSH-AHT400 as lubricant additive are improved due to the decrease of interlaminar shear strength of nanoparticle. Usage of the as-synthesized nanoparticle leads the formation of a-C tribofilm with higher degree of graphitic structural order. Meanwhile, the degree of graphitic structural order of the a-C correlates with the tribological performances positively. The simulations of classical molecular dynamics (CMD) and Ab-initio molecular dynamics (AIMD) confirm the ability of hydroxyl (–OH) and magnesium ions (Mg2+) in transforming base oil into a-C. A tribological mechanism of MSH-AHT400 as lubricant additive is proposed based on the aspects of easier interlaminar cleavage, nano-polishing and filling and repairing of composite tribofilm containing a-C. [Display omitted] • Reduced interlaminar shear strength of MSH-AHT400 enhances tribological properties. • PAO10 is converted into a-C by Mg2+ and –OH from MSH-AHT400 as lubricant additive. • MSH-AHT400 causes higher degree of graphitic structural order of a-C tribofilm. • Composite tribofilm containing a-C accounts for the tribological mechanism. [ABSTRACT FROM AUTHOR]