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| Authors | Base fluid, type of nano materials and concentration | Experimental apparatus | Major findings |
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| Bhaumik et al. [6] | Mineral oil dispersed with graphite and MWCNTs in concentration 0.1 to 0.6 Wt%. | Pin on disk tribometer and Four-ball tester | It is found that MWCNTs outperformed graphite with wear reduced by 70-75% and load bearing capacity increasing by 20%. |
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| Chen et. al. [5] | Paraffin oil dispersed with stearic acid modified MWCNTs in 0.45% Wt % | Ring on plate | Friction coefficient decreased by 10%, wear reduced by 30-40%. It was proposed that friction-reduction ability of nano-lubricant depends on both nano materials and obtaining stable dispersion of nano-particle in lubricant. |
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| Cornelio et. al. [7] | Oil and water with SWCNTs & MWCNTs 0.01 to 0.05 Wt % | Twin-disk machine for measurements in rolling-sliding contact | The friction coefficients and wear losses measured were lower for either oil or water dispersed with nanotubes with friction coefficients reported as low as 0.063. It was proposed that decrease of friction and high wear resistance are due to the formation of an amorphous carbon film transferred from the CNT’s on the surface. |
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| Ghaednia et. al. [8] | Mineral base oil dispersed with CuO (9 nm) in 0.5 to 2 wt% | disk-on-disk friction and wear test | Friction coefficient decreased by 14 and 23% for the CuO nanoparticle concentrations of 1.0 and 2.0% wt, respectively. It was suggested that the reduction in the real area of contact due to dispersion of nanomaterials in lubricant is possible mechanism for reduction of friction |
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| Hernandez Battez et. al. [9] | poly-alpha-olefin(PAO6) dispersed with CuO, ZnO and ZrO2 in 0.5 to 2% wt | Four-ball tester | The results indicate that the extreme pressure behavior of lubricant with nano particles is strongly dependent on the size and hardness of the nanoparticles. Particles with hardness less than surfaces in contact exhibited good EP behavior. |
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| Hu et. al. [10] | Water dispersed with sodium dodecyl sulfate modified oxidized MWCNTs in 0.1% Wt (for application in metal working fluids) | Four-ball tester | It is found that oxidation of MWCNTs produced defects on the surface leading to formation of better suspension. There is a good improvement in tribological properties with surfactant modified MWCNTs compared to pristine MWCNTs indicating strong influence of stability of suspension. |
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| Joly-Pottuz et. al.[11] | poly-alpha-olefin dispersed with carbon nano onions and graphite powders in 0.1% wt | pin-on-flat tribometer | Carbon nano-onions show better tribological properties than graphite powder. It is also found that tribofilm formed by carbon onions converts wear particles into ultrafine lubricious iron oxides, thus preventing further abrasive wear process. |
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| Khalil et. al. [12] | Mobil gear 627 and paraffinic mineral oils in 0.1 to 2 wt% | Four-ball tribotester | A 50% reduction in friction and an increase in weld load by up to 100% are observed with dispersion of MWCNTs in lubricant. The Tribological performance is attributed to deposition of MWCNTs nanoparticles on the worn surface resulting in decreasing the shearing stress, thus improving the tribological properties. |
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| Lee et. al. [13] | Raw mineral oil (Sun Oil, Japan) dispersed with fullerenes in 0.01 to 0.05% wt. | disk-on-disk tribotester | Fullerenes have reduced friction by 30% by reducing the metal surface contacts. Further, it is found that volume fraction is a key factor to control the friction and wear |
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| Lee et. al. [14] | Commercial gear oil dispersed with nano graphite (55 nm) in 0.1 to 0.5% wt. Alkyl aryl sulfonate is used as dispersant | disk-on-disk tribotester | The results indicate dispersion of nano graphite in lubricant boosted the lubrication characteristics. The possible reason for improvement of properties is suggested to be due to nanoparticles acting as ball bearing spacers between the friction surfaces reducing the contact between the plates. |
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| Pena-Paras et. al. [15] | 4 types of Metal working fluids dispersed with TiO2, Al2O3, CuO and MWCNTs in 0.01 to 0.1% wt | A four-ball T-02U tribotester | All nano materials improved the tribological properties with MWCNTs giving best results. Tribo-sintering of nano materials on the rubbing surfaces during machining is the reason proposed for the performance improvement. |
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| Puzyr et. al. [16] | Commercial oil dispersed with surface modified nano diamonds in 0.01% wt | block-on-ring test setup | Nano diamond additives in oils improved the anti- wear properties and decreased the oil temperature compared to base oils. The anti-wear mechanism of ND additives was attributed to the formation of a hard and porous layer between the contact surfaces. |
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| Sarma et. al. [17] | SM grade engine oil dispersed with Cu and TiO2 nano particles in 0.025 to 0.1% wt | Pin on disk tester and engine test rig | It was found that copper nano particle dispersed lubricant gave best results on engine tests. 3 to 5% increase in thermal efficiency of the engine is observed. |
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| Srinivas et. al. [18] | EP 140 Transmission oil dispersed with WS2 and MoS2 nano materials in 0.5% wt. | Four-ball tester | Lubricant dispersed with WS2 nanoparticles gave higher weld load and load wear index (LWI) than that of lubricant dispersed with MoS2 nanoparticles. The reason for better performance of WS2 nano particles is attributed to their lower hardness resulting in better deposition on the rubbing surfaces under load. |
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| Srinivas et.al. [19] | CI 4 Engine oil dispersed with long MWCNTs | Four-ball tester | The surface modification of multi walled carbon tubes plays prominent role in the improving stability and thereby anti-wear and anti-friction properties of engine oils. |
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| Viesca et. al. [20] | Poly alpha olefin (PAO6) dispersed with carbon coated nano particles in 0.5 to 2% wt | Block on-ring tribometer and four-ball tester | carbon-coated copper nanoparticles decreases wear and increases the load-carrying capacity of polyalphaolefin |
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