Advances in carbon nanomaterials as lubricants modifiers (original) (raw)
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Carbon Nanomaterial-Based Lubricants: Review of Recent Developments
Lubricants
This review article summarizes the progress of research on carbon nanomaterial-based lubricants witnessed in recent years. Carbon nanomaterials, such as graphene, carbon nanotubes (CNTs), fullerenes and carbon nanostructures, are at the center of current tribological research on attaining superior lubrication performance. The development of nanomaterial-based solid lubricants, lubricant additives and bulk materials and the related issues in their processing, characterization and applications as well as their tribological performance (coefficient of friction and wear rate) are listed in a structured tabulated form. Firstly, regarding nanomaterial-based solid lubricants, this study reveals that carbon nanomaterials such as graphite, graphene, graphene-based coatings and diamond-like carbon (DLC)-based coatings increase different tribological properties of solid lubricants. Secondly, this study summarizes the influence of graphene, carbon nanotubes, fullerene, carbon nanodiamonds, carb...
International Journal of Surface Science and Engineering
In the present study, the tribological performance of water-based emulsion (lubricant) was investigated by blending carbon fillers such as graphene nanoplatelets and multiwall carbon nanotubes using pin-on-disc tribometer. It was noticed that addition of GnP and MWCNT in water-based emulsion (conventional lubricant) increases the thermal conductivity and viscosity as compared to conventional lubricants. The nanolubricants were supplied with minimum quantity lubrication (MQL) technique at a constant flow rate and pressure in the sliding zone. The addition of 0.8 wt.% concentration of GnP showed 58.39% reduction in coefficient of friction and 61.80% reduction in wear depth compared to the conventional lubricant. Similarly, for 0.8 wt.% concentration of MWCNT showed 26.27% reduction in coefficient of friction and 47.35% reduction in wear depth compared to the conventional lubricant. The sliding surface micrographs were also investigated to explain the synergistic effect of nanoparticles.
A review on graphite and hybrid nano-materials as lubricant additives
IOP Conference Series: Materials Science and Engineering, 2016
The paper presents a review on use of nano-particles as lubricant additives. Nanoparticles have a strong potential to improve the lubrication property of grease when they are used as additives. Nano-grease has several advantages such as improved frictional behaviour, high load bearing capacity and reduced wear, as compared to base oil grease. Current advancements, limitations and challenges in use of nano-grease as a lubricant are discussed. Although, nanogrease has shown outstanding results, more research is required in this field for the commercialization of technology related to nano-grease. 2. Nano-additives in semi-solid lubricants There is a wide range of additives available that can be used in either micro or nano forms. However, it's not possible to use all the additives in their nano form, due to problems such as agglomeration of particles. Nano-additives are mainly inorganic nano-particles, carbon-based nano-particles and hybrid (surface capped) nano-particles. Inorganic nano-particles include pure metals, metal-oxides, metal-sulphides, metal-fluorides etc. Metal nano-particles have practical limitations of oxide formation in open environment. The limitation can be overlooked by surface modification/capping using certain organic compounds [5], [6]. Surface modified inorganic material functionalized/coated with organic material together is termed as hybrid nano-particles. The organic part of hybrid material system improves their flexibility and stability, while the inorganic part is responsible for hardness [7]. Materials reduced to nano-scale exhibit increase of surface energy with particles [8]. Higher surface energy of nano-particles leads to their agglomeration. [6]. Surface modification helps to reduce the degree of aggregation. Alkali metal fluorides such as CaF2, LiF2 and BaF2 have low shear strength and stable thermophysical and thermochemical properties at elevated temperature. At low temperature alkali fluoride remains in brittle state but at high temperature they undergo transition from brittle to plastic state. The plastic state at elevated temperature makes nano-additives good to be used in lubricant which operates in high temperature range [9]. Carbon based nano-particles are mainly graphene and fullerene. The shape and structure play an important role in the selection of nano-additives. They influence the functionality of nano-particles in lubricant. In analogy to fullerene, inorganic materials are also developed into these close caged structure, mainly soccer or nanotube, known as 'IF nano-materials'. The IF materials are synthesized from layered inorganic materials such as WS2, MoS2, TiS2 etc. [10]-[13]. Graphene is oneatom thick, 2D planar material of graphite with excellent physical, electrical and thermal properties [14]-[16]. Layered structured materials such as MoS2 [17] and graphene [18] are used as friction modifier in lubricants. In order to find suitable nano-additives for grease many nano-particles are tested and reported in literature. These tested nano-particles as additives include CaF2 [9] , nano-calcium borate (NCB) [19], nano-titanium dioxide [20], [21], CuO [21], nano-silicon dioxide [20], nano-calcium carbonate [22], graphene [18], [23], graphite [18], carbon nanotubes [24] and MoS2 among others. There are several challenges for use of nano-particles as additives. The biggest challenge is to avoid the agglomeration of nano-particles into grease in order to ensure the uniform dispersion throughout. Therefore, the method of mixing of the nano-particles is a subject to research. The functional improvement of nano-grease is subjected to concentration dependency of nano-additives. Nano-additives can improve the tribological performance of grease but only up to a certain limit. If the concentration is increased further, the tribological performance of grease deteriorates. At higher concentration, nano-particles form microclusters due to their tendency to get agglomerated.
Environmentally friendly technology for the modification of lubricants with graphene nanostructures
MATEC Web of Conferences, 2020
Nanomaterials, and in particular graphene, significantly increase the basic tribological characteristics of lubricants. One of the most effective ways to quickly use laboratory results on an industrial scale is to modify traditional lubricants with graphene concentrates. The research results showed that in order to solve this problem successfully, it is necessary to create graphene concentrate and distribute it evenly over the total volume of the lubricant. It is necessary that the concentrate be prepared on the same basis as the lubricant. In the present work, previous studies on the mechanical activation and exfoliation of graphite in a core drum mill, liquid-phase shear exfoliation in a rotary apparatus with moving blades, and the homogenization of graphene nanostructures in lubricants using a rotary mixer are combined. Changes were made to the design of the main components, taking into account the use of this technology in the industry. The presented technology is environmentall...
Journal of Materials Research and Technology, 2016
Since their discovery in 1991 carbon nanotubes (CNTs) have attracted much interest due to their remarkable mechanical, thermal, electrical, chemical and optical properties. In connection with their mechanical properties, CNTs have been studied in various forms for tribological applications including their use as lubricant additives for oil and water. In this work, the tribological properties of functionalized nanotubes (single and multi-walled) modified with carboxylic acid when used as lubricant additives at different concentrations (0.01, 0.05%) were studied under rolling-sliding conditions in a twin-disk testing machine. The tests were performed using 5% of creepage and pressures of 0.8 GPa and 1.1 GPa. The results indicated that the presence of carbon nanotubes leads to a decrease in both friction coefficient and wear rate for both systems studied (oil and water).
The working conditions in many industrial applications cause the tribo pair to operate in the mixed lubrication regime. Since the lubricant film thickness under these conditions is insufficient to separate the sliding tribo pair, therefore usage of lubricant with anti-wear additives is essential. The carbon nano-tubes (CNT) have recently emerged as lubricant additive having extraordinary tribological properties. In the present work, experiments have been conducted on block and disk test setup to determine the effect of using CNT as anti-wear additive in a commercial lubricant. Varying quantities of the CNT have been tried in the lubricant to conduct the wear tests. The wear of the block is quantified in terms of its weight loss after the test. The results of the wear tests are reported.
Novel Nanosized Friction Modifiers for Engine, Gearbox and Rolling Bearings Lubricants
Contemporary materials, 2015
In this paper the tribological performances of graphene oxide nanosheets in mineral oil under wide spectrum of conditions, from boundary and mixed lubrication to elastohydrodynamic regimes, are reported. Nanosheets of graphene oxide prepared by a modified Hummer method have been dispersed in Group I mineral oil. The formulated lubricant has been tested through a ball on disc setup tribometer to quantify the friction reduction with respect to the base mineral oil. The good friction and anti-wear properties of the graphene-oil mixture may possibly be attributed to the small structure of the nanosheets and their extremely thin laminated structure, which offer lower shear stress and prevent direct interaction between metal asperities in engine applications as well as gearbox environment. The results clearly prove that graphene platelets in oil easily form protective film to prevent the direct contact between steel surfaces and, thereby, improve the frictional behaviour of the base oil. ...
Tribological properties of dispersed carbon nanotubes in lubricant
This study examined the tribological properties of two lubricating oils, mobil gear 627 and paraffinic mineral oils, with multiwall carbon nanotubes (MWCNTs) nanoparticles used as additives with various concentrations (0.1, 0.5, 1, and 2 wt. %). The friction and wear experiments were performed using a four ball tribotester. The samples were tested for their antiwear, load carrying capacity and friction coefficients according to ASTM D-2783, ASTM D-2596 and ASTM D-5183 standards. The experimental results show that the addition of MWCNTs to base oils exhibit good friction-reduction and anti-wear properties. The wear test results show a decreased wear by 68 % and 39 % in the case of MWCNTs based mineral oil as compared with base mobil gear 627 and paraffinic mineral oils, respectively. Furthermore, the friction reduction results show a decrease of friction about 57 % and 49 % in the case of MWCNTs based mineral oil as compared with base mobil gear 627 and paraffinic mineral oils, respectively. The weld load of the base oil containing 1 % MWCNTs was found to be 400 kgf and 125 kgf as compared with base mobil gear 627 and paraffinic mineral oils, respectively Downloaded by [University of Nebraska, Lincoln] at 19:57 28 May 2016 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 which got welded at 200 kgf and 100 kgf. The morphologies and typical element distribution of the worn surfaces were characterized by SEM and EDX. The SEM micrographs and EDX chemical analysis confirm the formation of atribolayer composed of the elements from the nanoparticles.