Tribological Properties Of Base Oil Research Articles

Improving the lubricating performance of poly-alpha-olefin base oil using SnO2 nanosized-additives

The majority of previous studies have been focused on the thermal properties of SnO2 nanofluids. In order to understand the lubricating performance of SnO2 nanoparticles as additives, the current study investigates the effects of the addition of SnO2 nanoparticles on the tribological properties of poly-alpha-olefin 6 base oil. The dual-step method is utilized to disperse the SnO2 nanoparticles in base oil with oleic acid as surfactant. The shape and size of SnO2 nanoparticles are confirmed by transmission electron microscopy, and the dispersion stability of SnO2 nanoparticles is examined by dynamic light scattering tests. The lubricating properties of SnO2 nanofluids are explored on a universal mechanical tribometer with a ball-on-plate reciprocating sliding configuration. It is found that the SnO2 nanofluids show good stability and dispersibility. The addition of SnO2 nanoparticles decreases the friction and wear for steel-steel tribo-pairs. The positive effects on friction and wear reductions become more significant with increasing concentrations of SnO2 nanoparticles. In this work, nanofluids containing the 5wt% SnO2 nanoparticles and 5wt% oleic acid is considered as the optimum composition, which shows the best lubricating performance with the reductions of 13.8% in coefficient of friction and 41.4% in wear volume loss. After observing the wear tracks by scanning electron microscopy, energy dispersive spectrometer and a white-light interferometer, it is shown that the wear mechanisms are dominated by abrasive wear and adhesive wear. The enhancement in tribological properties of base oil is attributed to the formation of SnO2 tribo-film and oleic acid tribo-layer which reduces the shearing resistance, separates the mating areas and withstands the loads. The findings obtained in this study can be used as references in the development of high-performance nanofluids.

A tribological behavior assessment of steel contacting interface lubricated by engine oil introducing layered structural nanomaterials functionalized by oleic acid

Traditional lubricating oil in the lubrication process leads to oil film rupture and lubrication failure due to thermal instability under high temperatures. Tribological characteristics of synthetic oil (5W-40) can be potentially improved by the application of layered nanoparticles (h-BN and MoS2 NPs). The tribological properties of base oil, MoS2, and h-BN nanolubricants (NLs) were comprehensively investigated under varying loads, rotating speeds, and temperatures using a four-ball tribometer. Moreover, this study confirmed that the COF and wear rate values of wear scar lubricated by h-BN NL and MoS2 NL decreased by approximately 21.5% and 13%, 91.6% and 90.9%, respectively, compared with base oil, showing the brilliant tribological performance following the introduction of NL. The results showed the wear interface lubricated by NL with oleic acid (OA) functionalization contributed to the appearance of tribo-film along with chemical absorption film due to the complicated oxidizing reaction. Eventually, the synergistic role between OA and nanomaterials responsible for the increasing tribological properties is elaborately elucidated.

The superior lubricating performance and unique mechanism of oil-soluble protic ionic liquids with short alkyl chains

HypothesisIonic liquids (ILs), as lubricant additives, can greatly improve the lubricating behavior of the frictional interfaces. However, it is urgent to explore ILs with good oil solubility in nonpolar oils, and it is necessary to further study and verify the lubrication mechanism of ILs from the perspective of alkyl chain length. ExperimentsFive protic ILs (PILs) with varying alkyl chain lengths were synthesized by proton transfer method. As additives in PAO oil, their tribological properties were investigated on SRV-V tester. Through molecular dynamics simulation, the adsorption behavior of PILs at the frictional interface was illustrated. FindingsThe tribological properties of base oil could be significantly improved by adding PIL additives, but interestingly, PILs with short-chain anions showed better lubricating performance, which contradicted most of the early findings. Further analyses revealed that PILs achieved effective lubrication by the tribochemical interaction between anions and frictional interface, and the formation of cationic protective layer. However, PILs with shorter-chain anions form a denser protective layer that can better support the interfacial anions to participate in tribochemical reactions and thus abnormally exhibit superior lubricating performance than those with longer-chain anions.

Reduced friction and wear enabled by arc-discharge method-prepared 3D graphene as oil additive under variable loads and speeds

A high quality three dimensional graphene nanosheets (3D GNS) with few layers’ thickness was prepared by the arc-discharge method. The 3D GNS is used as oil additive to explore its tribological performance under different working conditions. The results demonstrate that with the help of 3D GNS, the anti-wear and friction-reduction capabilities of base oil are improved in a wide range of speed and load. Especially under low speed and heavy load condition (4.2 mm/s and 1.0 GPa contact pressure), the reduction in coefficient of friction and wear volume loss can be as high as 29.1% and 55%, respectively. Raman spectrum and its mapping together confirmed the existence of protective film consisted by 3D GNS on rubbing surface, which avoids the direct contact of tribo-pairs and thus enhances the tribological performance of oil. In the case of heavier load condition, the lubricating performance of 3D GNS was reduced owing to the deteriorated 3D structure of the GNS. For higher speed, the thicker oil film brings better tribological properties to oil and minute 3D GNS is needed to participate in the friction process. The results are in good agreement with the Stribeck curve prediction. In brief, 3D GNS is helpful for improving the tribological properties of base oil under low speed and heavy load; thus providing a new insight for practical application as lubricant additive.

Nano-Magnesium Silicate Hydroxide/Crumpled Graphene Balls Composites, a Novel Kind of Lubricating Additive with High Performance for Friction and Wear Reduction.

In this study, crumpled graphene balls (CGB), a kind of nano-material, was used as an additive to improve the tribological properties of base oil. Nano-magnesium silicate hydroxide (MSH)/CGB composites were prepared by ultrasound-assisted liquid-phase exfoliation. The loading of MSH significantly increased the number of pleats and reduced the lamellar thickness of CGB. Then, in order to improve the compatibility with the base oil, the MSH/CGB composites were decorated with oleic acid and stearic acid to get modified lipophilic composites (ML-MSH/CGB). The ML-MSH/CGB were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). In addition, the tribological properties of the ML-MSH/CGB in base oils were investigated using a ball-on-disc setup tribometer. It indicated that the fantastic tribological behavior of the ML-MSH/CGB in base oil may contribute to a smaller and extremely wrinkled laminated structure. Furthermore, the base oil with 0.005 wt% ML-MSH/CGB composites exhibited the best anti-friction effect, and its average friction coefficient, wearing capacity and wear scar diameter were reduced by 25.4%, 22.1% and 16.7%, respectively. The introduction of ML-MSH/CGB composed materials is an excellent strategy to optimize the friction performance of lubricating oil.

Synthesis of Novel Macromolecular Coupling Agent and its Application in Nano-Copper Lubricating Oil

Background: Due to temperature-insensitive and limited tribochemical reaction, nanolubricants have received tremendous focus over the past few years. The addition of nanoparticles in lubricant has been demonstrated to reduce the coefficient of friction and increase the loadcarrying capability of lubricant in coupled surfaces. Much attention has been paid to copper nanoparticles for their perfect friction reduction and wear resistance performances. However, it is difficult to maintain stable dispersion in lubricant oil for the aggregation of copper nanoparticles. Methods: A novel macromolecular coupling agent copolymer, styrene-butyl methacrylate-3- methoxyacryloyl-propyltrimethoxyl silicon was successfully prepared by free radical polymerization. The structure and composition of the copolymer were characterized through X-ray diffractometer, Fourier-transform infrared spectrometer, and nuclear magnetic resonance spectrometer. The loadcarrying capacities and anti-wear properties of the base oil were evaluated on four-ball tester. Results: The average size of the nano-Cu particle was around 40 nm. The modifier, St-MMA-(KH- 570) macromolecular copolymer could improve the dispersibility of nano-Cu particles. The introduction of the nano-Cu particles helped to improve the tribological properties of base oil. Conclusion: The macromolecular coupling agent was synthesized by free radical solution polymerization method. The modifier was able to bond to the nano-Cu via chemical interaction. The modified Cu nanoparticles as the additive were able to greatly improve the anti-wear and extreme pressure properties of base oil. The optimum concentration of modified Cu nanoparticles in base oil was 0.25 wt.%.

Fatty acid based phosphite ionic liquids as multifunctional lubricant additives in mineral oil and refined vegetable oil

Abstract Ionic liquids (ILs) are highly attractive lubricant additives for their nonflammability, low vapor pressures, structural diversity and reasonable tribological properties. A convenient synthesis route to oil-dispersible ILs has been presented in this paper. Phosphite binds to aliphatic acid as anion and triethylbenzylammonium serve as a cation, which could be applied as lubricant additives in mineral oil (5CST) and refined vegetable oil (RSO). Results demonstrated that these ILs could effectively enhance the antiwear, friction-reducing and extreme pressure properties of 5CST and RSO. The chain length and unsaturation of fatty acid is significant in improving the tribological properties of base oil. TEY and FY mode K-edge XANES analysis of the formed tribofilms showed that the improvement of anti-wear and friction-reducing properties was closely related to the content of phosphate species on the near surface.

Development of a nitrogen-doped 2D material for tribological applications in the boundary-lubrication regime.

The present paper describes a facile synthesis method for nitrogen-doped reduced graphene oxide (N-rGO) and the application of N-rGO as an effective additive for improving the tribological properties of base oil. N-rGO has been characterized by different characterization techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. N-rGO-based nanolubricants are prepared and their tribological properties are studied using a four-ball tester. The nanolubricants show excellent stability over a period of six months and a significant decrease in coefficient of friction (25%) for small amounts of N-rGO (3 mg/L). The improvement in tribological properties can be attributed to the sliding mechanism of N-rGO accompanied by the high mechanical strength of graphene. Further, the nanolubricant is prepared at large scale (700 liter) and field trials are carried out at one NTPC thermal plant in India. The implementation of the nanolubricant in an induced draft (ID) fan results in the remarkable decrease in the power consumption.

Influence of Aluminum Nanoparticles Additives on Tribological Properties of Base Oil

This study investigates the influence of aluminum nanoparticles, oleic acid as dispersants, and rotational speed on the tribological behavior of a lubricant. The experiments are performed on a pin-on-disc tribotester at a normal force of 90 N and a rotational speed ranging from 150 rpm to 600 rpm. Both the aluminum nanoparticles and oleic acid are in concentrations from 0 to 1 wt% and are added to the SN150 base oil. The results revealed that the addition of aluminum nanoparticles and oleic acid to the base oil will lead to significant friction reduction and anti-wear properties. The coefficient of friction (COF) and wear rate decreased after an increase in the concentration of nanoparticles and oleic acid, and an optimum concentration level was exhibited in which both COF and wear-rate were lowest. The viscosity and temperature of the lubricant are also evaluated. Further, the topography of discs after performance of sliding test have been analyzed through the use of an optical microscope, a scanning electron microscope (SEM), and an energy dispersive spectrometer (EDS) in order to interpret the mechanisms of nanoparticle action used to prevent friction and subsequent wear.

Synthesis and Tribological Properties of TiSe<sub>2</sub> Nanoparticles

TiSe2 nanobelts/nanoplates have been successfully fabricated through a facile and environment-friendly pressureless sintered process using micro-sized Ti and Se elements as raw materials. The morphology and structure of the as-prepared TiSe2 products were investigated by X-ray diffractometer, scanning electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy. The experimental results indicated that the morphology of TiSe2 products were strongly dependent on the reaction temperature and reaction time. As the reaction temperature was set at 600°C and 800°C, long belts-like and plates-like structures of as-prepared TiSe2 products could be observed, respectively. However, a mixture of nanobelts and nanoplates could be obtained at a reaction temperature of 700°C. It was also found that the reaction time played a crucial role in obtaining the homogeneous distribution nanoparticles, therefore, reasonable reaction process and formation mechanisms of as-prepared TiSe2 nanoparticles were proposed. Moreover, the tribological properties of the TiSe2 nanobelts/nanoplates were investigated. The test results showed that the addition of TiSe2 nanoparticles could improve the tribological properties of base oil. Furthermore, the friction coefficient of base oil containing TiSe2 nanoplates was lower and more stable than those of TiSe2 nanobelts and pure base oil.

Preparation of TiO2/Ti3C2Tx hybrid nanocomposites and their tribological properties as base oil lubricant additives

TiO2/Ti3C2Tx hybrid nanocomposites were successfully prepared by a liquid phase synthesis technology. The hybrid nanocomposites improve the tribological properties of base oil by mending the surface and formation a uniform tribofilm on the surface.

Effect of Compatibility between AlN Nanoparticles and Borated Bis-Succinimide on Tribological Properties of Base Oil

The purpose of the research was to investigate effect of compatibility between AlN nanoparticles and borated bis-succinimide on tribological properties of base oil. The load-carrying capacity and anti-wear (AW) performance of base oil that contains aluminum nitride (AlN) nanoparticles or borated bis-succinimide (T152B) additive was examined; the tribological properties of the compatibility between AlN and T152B were also examined. The experimental results showed that AlN nanoparticles additive can effectively improve load-carrying capacity and anti-wear performance of base oil. AlN nanoparticles and T152B compatibility experiments showed that two additives have synergies to improve anti-wear performance of base oil. These findings indicate that AlN nanopaticles is an excellent load-carrying capacity and antiwear additive, and it can be used with T152B together in base oil.

Comparative Study on Tribological Behavior of Sb<SUB>2</SUB>S<SUB>3</SUB> Nano-bundles and Nano-particles in Liquid Paraffin

The tribological properties of Sb2S3 nano-bundles as an additive in liquid paraffin were evaluated on a four-ball tester, thereafter the performance of Sb2S3 nano-bundles was compared with that of Sb2S3 nano-particles. The comparative analyses of friction coefficients, wear scar diameters and morphology of worn surfaces show that Sb2S3 nano-bundles and nano-particles can both improve tribological properties of base oil, Sb2S3 nano-bundles exhibit better friction reduction and anti-wear properties than Sb2S3 nano-particles at relative low load, and they possess very similar tribological performance at relative high load. As far as the load carrying ability is concerned, the performance of nano-particles is obviously better than nano-bundles. It is inferred that the sliding-rolling friction transition emerges when lubricated with nano-bundles/oil mixture at low load, which contributes to the good lubricating effect of the

Synthesis and tribological properties of NbSe3 nanofibers and NbSe2 microsheets

AbstractNbSe3 nanofibers and NbSe2 sheets were prepared by solid state reaction. The as‐prepared products are characterized by powder X‐ray diffraction (XRD), and scanning electron microscopy (SEM). The results showed that the obtained NbSe3 nanofibers have a diameter in the range of 100–300 nm and length about 10 μm, while the NbSe2 sheets have a hexagon structure. The tribological properties of the as‐prepared NbSex powders as additives in HVI500 base oil were investigated on UMT‐2 multispecimen tribo‐tester. The wear scars were measured by VEECO WYKO NT1100 non‐contact optical profile testing instrument. It is found that the addition of both NbSex nanofibers/sheets improves the tribological properties of base oil. Furthermore, NbSe2 sheets exhibit better friction reduction and wear resistance properties than NbSe3 nanofibers in HVI500 base oil. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)