L. Rapoport, V. Leshchinsky, M. Lvovsky, O. Nepomnyashchy, Yu Volovik and R. Tenne
In the past few years, inorganic fullerene‐like (IF) supramolecules of metal dichalcogenide WS2 and MoS2 with structures closely related to (nested) carbon fullerenes and…
Abstract
In the past few years, inorganic fullerene‐like (IF) supramolecules of metal dichalcogenide WS2 and MoS2 with structures closely related to (nested) carbon fullerenes and nanotubes have been synthesized. Recent experiments showed that IF added to oil and impregnated into the porous matrixes possess lubricating properties superior to those of layered WS2 and MoS2 (2H platelets). The main goal of this work was to analyze the mechanism of friction of fullerene‐like nanoparticles. Friction and wear behavior of IF in different contact conditions is studied. Third body model is considered. Sliding/rolling of the IF nanoparticles in the boundary of the first bodies and in between the wear particles (third body) is supposed to facilitate the shear of the lubrication film. Broken and oxidized 2H‐WS2 small pieces adhered to wear debris do not provide high tribological properties especially under high loads.
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Juozas Padgurskas, Igoris Prosyčevas, Raimundas Rukuiža, Raimondas Kreivaitis and Artūras Kupčinskas
The purpose of this paper is to investigate the possibility of using the iron nanoparticles and iron nanoparticles coated with copper layer as additives to base oils.
Abstract
Purpose
The purpose of this paper is to investigate the possibility of using the iron nanoparticles and iron nanoparticles coated with copper layer as additives to base oils.
Design/methodology/approach
Fe and Fe+Cu nanoparticles were synthesized by a reduction modification method and added to mineral oil. The size and structure of prepared nanoparticles were characterized by SEM, TEM, XRF, AAS and XRD analysis. Tribological properties of modified lubricants were evaluated on a four‐ball machine in a model of sliding friction pairs.
Findings
Spectral and microscopy analysis evidently displayed the formation of Fe and Fe+Cu nanoparticles in suspensions of colloidal solutions and oil. The size of formed nanoparticles was in 15‐50 nm range. Tribological experiments show good lubricating properties of oils modified with Fe and Fe+Cu nanoparticles: higher wear resistance (55 per cent and 46 per cent accordingly) and lower friction coefficient (30 per cent and 26 per cent accordingly). The tests show that nanoparticles provide decreasing tendency of friction torque during the operation of friction pair.
Originality/value
The paper demonstrates that iron nanoparticles and iron nanoparticles coated with copper layer, not only reduce the wear and friction decrease of friction pairs, but possibly also can create layer in oil which separates two friction surfaces and have some self‐organisation properties.
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To provide a suitable useful mixing ration of nano‐sized molybdenum disulfide and commercial common molybdenum sulfide (MoS2) particles (approximately 1.5 μm in diameter) in…
Abstract
Purpose
To provide a suitable useful mixing ration of nano‐sized molybdenum disulfide and commercial common molybdenum sulfide (MoS2) particles (approximately 1.5 μm in diameter) in liquid paraffin, which can lead to a better tribological performance.
Design/methodology/approach
The MoS2 nanoparticles and commercial common MoS2 particles (approximately 1.5 μm in diameter) were dispersed in liquid paraffin with different concentrations and ratios by means of ultrasonic in order to study their lubrication capacity, friction reduction and wear resistance. The tribological experiments were carried out by MQ‐800 four‐ball tribometer, in which extreme pressure, wear scan diameter and friction coefficient were measured. It was analyzed that the chemical status of elements on the rubbed surface by X‐ray photoelectron spectroscopy (XPS), and it was observed that the surface topography of wear scan by scanning electron microscope (SEM).
Findings
The results showed that the loading capacity of liquid paraffin with different kinds of MoS2 particles were increased with their contents. The liquid paraffin containing the mixture of MoS2 nanoparticles and common MoS2 particles has a better wear resistance, friction‐reducing performance and extreme pressure property than the liquid paraffin containing pure common MoS2 or pure nano‐MoS2 particles. The optimal mixing ratio of nano‐MoS2 and common MoS2 is 20 wt percent, the loading capacity reaches the highest value. By XPS and SEM it was suggested that the difference in the tribological performance between MoS2 nanoparticles and MoS2 common particles was attributed to the surface and interfacial size‐effect of nanoparticles and the formation of molybdenum trioxide thin film on the rubbed surface.
Research limitations/implications
It is not studied that the effects of mixing of common MoS2 and nano‐MoS2 in the actual lubricating oil with various additives.
Practical implications
It provided a basic research results and data for the application of nano‐MoS2 particles.
Originality/value
The mixing of nanoparticles and non‐nano‐sized particles will lead to new tribological results, which is different from results obtained from other nanoparticles before.
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Jiusheng Li, Lifeng Hao, Xiaohong Xu and Tianhui Ren
Sulfurized olefins have been extensively used in many kinds of gear lubricants as EP additives. However, their commercial applications are not totally satisfactory because of the…
Abstract
Purpose
Sulfurized olefins have been extensively used in many kinds of gear lubricants as EP additives. However, their commercial applications are not totally satisfactory because of the pungent, obnoxious odor and corrosion of copper and copper alloys. The purpose of this paper is to investigate the synergistic effects of one type of calcium borate nanoparticles modified by oleic acid (code to CaBN) and sulfurized olefin, in a kind of mineral base oil MVIS 250, in order to find a potential substitute for sulfurized olefins.
Design/methodology/approach
One kind of calcium borate nanoparticle modified by oleic acid (CaBN) was prepared, and its structures were characterized by inductively coupled plasma atomic emission spectroscopy (ICP‐AES), X‐ray power diffraction (XRD) and transmission electron microscope (TEM). The tribological properties of the complex of CaBN with sulfurized olefins (T321) in base oil were evaluated using four‐ball tribotester and compared with CaBN or T321 as individual component. The worn surfaces were investigated by scanning electron microscope (SEM) and X‐ray photoelectron spectroscopy (XPS). In addition, the corrosion‐inhibiting properties of additives were also studied.
Findings
The results of tests show that there are significant synergistic effects on tribological properties between two kinds of additives. Based on the results of SEM and XPS, it can be deduced that a wear resistance film containing B2O3, FeS, FeS2 and CaO was formed on the worn surfaces during the sliding process. Moreover, CaBN and T321 also show excellent synergistic effect on the corrosion‐inhibiting property.
Originality/value
This paper provides a kind of “green” nanoparticle which possesses excellent synergic effect with sulfurized olefins, and gives another selection for industrial applications in which T321 is needed.
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Manu V. Thottackkad, P.K. Rajendrakumar and K. Prabhakaran Nair
– This manuscript aims to deal with the tribological property variations of engine oil (SAE15W40) by the addition of copper oxide (CuO) nanoparticles on weight percentage basis.
Abstract
Purpose
This manuscript aims to deal with the tribological property variations of engine oil (SAE15W40) by the addition of copper oxide (CuO) nanoparticles on weight percentage basis.
Design/methodology/approach
Experimental studies on the influence of CuO nanoparticles utilised as an additive in lubricating oil (SAE15W40) under boundary lubrication conditions have been carried out using a pin-on-disc machine in accordance with ASTM G-99 standard. The variation of viscosity, coefficient of friction, wear and settling of nanoparticles has been studied as a function of particle concentration in the lubricant.
Findings
Results show that the frictional force and specific wear rate decrease with an increase in concentration of nanoparticles comes to a minimum at a specific concentration and then increases, showing the presence of an optimum concentration. With the increase in concentration of nanoparticles, the kinematic and dynamic viscosities, and the flash and fire points are found to increase.
Originality/value
The use of CuO nanoparticles as additives to a moderate level is a very efficient means of improving the tribological properties of lubricating oils.
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Alaa Mohamed, Mohamed Hamdy, Mohamed Bayoumi and Tarek Osman
This work describes the fabrication of composite nanogrease based on carbon nanotubes (CNTs) as an additive at different volume concentrations 0, 0.5, 1, 2 and 3 Wt.% and…
Abstract
Purpose
This work describes the fabrication of composite nanogrease based on carbon nanotubes (CNTs) as an additive at different volume concentrations 0, 0.5, 1, 2 and 3 Wt.% and investigates the correlation between CNTs and grease rheological behaviour. In addition, study the influence of shear thinning rate at various temperatures and investigates the thermal conductivity of nanogrease. The results demonstrated that grease behaves like a Newtonian viscoelastic material with a narrow linear domain. The thermal conductivity of nanogrease was enhanced by about 31.58 per cent, and the thermal and mechanical stabilities improved. Moreover, the apparent viscosity and dropping point increased by about 93 and 27 per cent, respectively.
Design/methodology/approach
Grease was dissolved in chloroform (10 Wt.%), at 25°C for 1 h. In parallel, functionalized CNTs with different volume concentrations (0.5, 1, 2 and 3 Wt.%) were dispersed in N,N-dimethylformamide; the dispersion was stirred for 15 min, and then sonicated (40 kHz, 150 W) for 30 min. Grease solution was then added to the CNTs. The nanofluid was magnetically stirred for 15 min and then sonicated for 2 h. This ensured uniform dispersion of nanoparticles in the base fluid.
Findings
Inexpensive and simple fabrication of nanogrease. Thermal conductivity of nanogrease was typically enhanced compared to other reported studies. Apparent viscosity and dropping point increases with the increase the volume concentration.
Originality/value
This work describes the inexpensive and simple fabrication of nanogrease for improving properties of lubricants, which improve power efficiency and extend lifetimes of mechanical equipment.
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Tatjana Maliar, Satish Achanta, Henrikas Cesiulis and Dirk Drees
The purpose of this paper is to investigate the tribological behaviour of commercially available SAE 10 mineral and rapeseed oils containing Fe particles synthesized directly in…
Abstract
Purpose
The purpose of this paper is to investigate the tribological behaviour of commercially available SAE 10 mineral and rapeseed oils containing Fe particles synthesized directly in the oil phase.
Design/methodology/approach
Sub-micron Fe particles (50-340 nm) were synthesized by wet chemical reduction reaction of FeSO4 by sodium borohydride in the rapeseed and mineral oils in the presence of surfactant: block copolymer (ENB 90R4) or oxyethylated alcohol (OS-20). A four-ball wear tribometer was used to investigate the tribological properties of mineral and rapeseed oil: coefficient of friction (COF), wear scar diameter and wear loss. Viscosity measurements of oil solutions and determination of synthesized Fe particles size were performed as well.
Findings
The presence of Fe particles (0.1 weight per cent) in the rapeseed and mineral oils caused the little change in the COF but resulted in marked improvement of anti-wear property. The oils containing Fe particles with slightly higher viscosity are giving more friction due to viscous drag. The anti-wear enhancement is attributed to the formation of tribofilm and superior load-bearing capability of the modified oil. Both rapeseed and mineral oils irrespective of used surfactant in the presence of 0.1 weight per cent Fe particles (50-140 nm) show sufficiently improved anti-wear properties.
Originality/value
The data collection about tribological behaviour of oils containing Fe particles and various additives in lubricants has a practical interest. The findings could be helpful to increase the knowledge of the behaviour of real tribological systems, where the metallic debris are generated during friction and contaminate the lubricating oil.
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S. Shankar and P. Krishnakumar
The purpose of this study was to investigate the frictional characteristics of the mechanical seals by using an efficient pairing by providing a suitable lubricant. Among all…
Abstract
Purpose
The purpose of this study was to investigate the frictional characteristics of the mechanical seals by using an efficient pairing by providing a suitable lubricant. Among all techniques and lubrication, deposition of solid lubricants on the sliding surface of the mechanical seal was found to be the most effective method to reduce frictional coefficient, frictional force and seal face temperature, thereby increasing the life time of mechanical seal.
Design/methodology/approach
In this study, two coatings, diamond-like carbon (DLC) and tungsten carbide/carbon (WC/C), was deposited over the stationary high-carbon high-chromium steel ring paired with resin-impregnated carbon. Their frictional characteristics were studied under various classes of liquid lubricants such as organic liquids, synthetic oil, mineral oil and vegetable oils using an experimental approach. Further, among all classes of liquid lubricants, the one which showed better frictional characteristics was mixed with 0.5, 1 and 2 wt% of potential environmental friendly solid lubricant – boric acid powder.
Findings
The high hardness and low surface roughness of DLC- and WC/C-coated seal with the lubricant of palm olein oil containing 1 wt% of boric acid powder contributed a hybrid tribofilm and resulted in low and stable friction coefficient in the range of 0.04-0.05 without any measurable wear.
Originality/value
A pair involving stationary DLC- and WC/C-coated seal ring and resin-impregnated carbon seal rotating ring for the application of mechanical seal was suggested and its frictional characteristics were studied under various classes of lubricants.
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Xiaodong Zhou, Huaqiang Shi, Xun Fu, Danmei Wu and Zhengshui Hu
The purpose of this paper is to investigate the tribological properties of MoS2 nano‐sized hollow spheres in liquid paraffin (LP) and the corresponding action mechanism. Morever…
Abstract
Purpose
The purpose of this paper is to investigate the tribological properties of MoS2 nano‐sized hollow spheres in liquid paraffin (LP) and the corresponding action mechanism. Morever, its feasibity of industrial application as an oil additive in the industrial lubrication field is also explored.
Design/methodology/approach
The tribological properties of MoS2 nano‐sized hollow spheres (NH‐MoS2) modified by Cyanex 301(di‐(2,4,4‐trimethylpentyl) dithiophosphinic acid) with size of 200 ∼ 300 nm in LP are studied and compared with those of the commercial colloidal MoS2 (CC‐MoS2) on a four‐ball tester and an Optimol SRV Oscillating friction and wear tester in a ball‐on disk configuration. The worn surfaces of the lower flat disc are examined with a scanning electron microscopy and an X‐ray photoelectron spectroscopy, respectively.
Findings
Results show that NH‐MoS2 is a better extreme‐pressure additive and anti‐wear (AW) and friction‐reducing additive in LP than CC‐MoS2. Under the optimum concentration of 0.5 per cent for both NH‐MoS2 and CC‐MoS2 and the load of 400 N, the friction coefficient of NH‐MoS2 + LP and CC‐MoS2 + LP decreases about 43.8 and 6.3 per cent, and the wear volume loss decreases about 60.3 and 12.0 per cent compared with the pure LP. The boundary lubrication mechanism for NH‐MoS2 + LP can be deduced as the effective chemical adsorption protective film formed by the long chain alkyls R and active elements (S and P) in the modification layer and tribochemical reaction film containing the tribochemical products of the additive. Moreover, sliding and rolling frictions co‐exist in NH‐MoS2 + LP, doing contributions to the good tribological properties as well.
Originality/value
In this paper, the Cyanex 301‐modified MoS2 nano‐sized hollow spheres with diameter of 200 ∼ 300 nm are firstly added into LP to investigate its tribological properties. The excellent AW and friction‐reducing properties indicate that this MoS2 hollow spheres product is a good oil additive, and the fundamental data presented here will be useful for its further industrial application in the future.
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Nanoparticles have been studied as additives to lubrication oils for reducing friction and wear. The purpose of this paper is to investigate the effect of nanofluid on engine oil…
Abstract
Purpose
Nanoparticles have been studied as additives to lubrication oils for reducing friction and wear. The purpose of this paper is to investigate the effect of nanofluid on engine oil and friction reduction in a real engine.
Design/methodology/approach
The nanoparticles were prepared using a high‐temperature arc in a vacuum chamber to vaporize the Ti metal, and then condensed into a dispersant to form the TiO2 nanofluid, which was used as lubricant additive. Experiments were performed in both real engine running and test rig.
Findings
It was found that the engine oil with nanofluid additive with an ethylene glycol dispersant of nanoparticles, had gelled after 10‐h of engine running. The problem of oil gelation (jelly‐like) was solved by replacing the dispersant with paraffin oil. The engine oil with TiO2 nanoparticle additive exhibited lower friction force as compared to the original oil. The experiment showed that a smaller particle size exhibits better friction reduction with particle size ranging from 59 to 220 nm.
Research limitations/implications
The paper is restricted to findings based on the dispersed nanoparticles in fluid as additive for engine lubrication oil.
Practical implications
The test results are useful for the application of nanofluid additive for engine oil.
Originality/value
Most previous researches in this field were executed on tribotester, rather than the actual engine. This paper describes experimental methods and equipment designed to investigate the application of TiO2 nanofluid as lubricant additive in internal combustion engine.