The lubricating performance of two oils (base oil PAO and synthetic motor oil denoted as 5w40) was clarified by doping them with phosphonium-based ionic liquids (P-ILs) and a mixture of P-ILs and metal oxide nanoparticles. The nanoparticles were synthesized by heating titanium tetrabutoxide and 1-methyl-3-(triethoxysilylpropyl)imidazolium chloride-based ionogel in trihexyltetradecylphosphonium bis (2,4,4-trimethylpentyl)phosphinate (P-IL1) or trihexyltetradecylphosphonium bis(2-ethylhexyl) phosphate (P-IL2) media. Tribological experiments were performed using a standard four-ball tribometer. The nanoparticles were characterized by scanning electron microscopy and 1H-NMR. The worn areas of the steel balls were visualized applying optical microscopy. The thermal stability of the solutions of ionic liquids–nanoparticles was determined by thermogravimetric analysis. The best anti-wear performance was achieved by using P-IL2 with functionalized hybrid oxide nanoparticles as an additive in both selected lubricant oils. When the mixture of PAO and 1% P-IL2 + nanoparticles was used as an additive, the wear scar area decreased by ~62% compared to pure PAO. In the case of synthetic motor oil with the addition of the mixture of 1% P-IL2 + nanoparticles the wear trace decreased by ~48%. The wear scar area was found to be significantly reduced when smaller nanoparticles were used. It was shown that the synergistic effect of ionic liquids and hybrid oxide nanoparticles synthesized using the presented novel method can have a great potential for increasing the wear performance of conventional commercial oils. It is crucial from the commercial point of view that only a small amount of ionic liquids–nanoparticles additives (0.1<<1 ww%) in oils is required to induce an enormous effect on their tribological properties.
1. Bermúdez, M.-D., Jiménez, A.-E., Sanes, J., and Carrión, F.-J. Ionic liquids as advanced lubricant fluids. Molecules, 2009, 14, 2888–2908
https://doi.org/10.3390/molecules14082888
2. Minami, I. Ionic liquids in tribology. Molecules, 2009, 14, 2286–2305.
https://doi.org/10.3390/molecules14062286
3. Palacio, M. and Bhushan, B. A review of ionic liquids for green molecular lubrication in nanotechnology. Tribol. Lett., 2010, 40, 247–268.
https://doi.org/10.1007/s11249-010-9671-8
4. Somers, A. E., Howlett, P. C., MacFarlane, D. R., and Forsyth, M. A review of ionic liquid lubricants. Lubricants, 2013, 1, 3–21.
https://doi.org/10.3390/lubricants1010003
5. Zhou, F., Liang, Y., and Liu, W. Ionic liquid lubricants: designed chemistry for engineering applications. Chem. Soc. Rev., 2009, 38, 2590–2599.
https://doi.org/10.1039/b817899m
6. Welton, T. Room-temperature ionic liquids. Solvents for synthesis and catalysis. Chem. Rev., 1999, 99, 2071–2084.
https://doi.org/10.1021/cr980032t
7. Garcia, M. T., Gathergood, N., and Scammells, P. J. Biodegradable ionic liquids. Part II. Effect of the anion and toxicology. Green Chem., 2005, 7, 9–14.
https://doi.org/10.1039/b411922c
8. Handy, S. T. Room temperature ionic liquids: different classes and physical properties. Curr. Org. Chem., 2005, 9, 959–988.
https://doi.org/10.2174/1385272054368411
9. Ye, C., Liu, W., Chen, Y., and Yu, L. Room-temperature ionic liquids: a novel versatile lubricant. Chem. Commun., 2001, 21, 2244–2245.
https://doi.org/10.1039/b106935g
10. Välbe, R., Mäeorg, U., Lõhmus, A., Reedo, V., Koel, M., Krumme, A., et al. A novel route of synthesis of sodium hexafluorosilicate two component cluster crystals using BF4− containing ionic liquids. J. Cryst. Growth, 2012, 361, 51–56.
https://doi.org/10.1016/j.jcrysgro.2012.08.043
11. Huddleston, J. G., Visser, A. E., Reichert, W. M., Willauer, H. D., Broker G. A., and Rogers R. D. Characterization and comparison of hydrophilic and hydrophobic room temperature ionic liquids incorporating the imidazolium cation. Green Chem., 2001, 3, 156–164.
https://doi.org/10.1039/b103275p
12. Wilkes, J. S. and Zaworotko, M. J. Air and water stable 1-ethyl-3-methylimidazolium based ionic liquids. J. Chem. Soc. Chem. Commun., 1992, 13, 965–967.
https://doi.org/10.1039/c39920000965
13. Ma, K., Somashekhar, B. S., Nagana Gowda, G. A., Khetrapal, C. L., and Weiss, R. G. Induced amphotropic and thermotropic ionic liquid crystallinity in phosphonium halides: “lubrication” by hydroxyl groups. Langmuir, 2008, 24, 2746–2758.
https://doi.org/10.1021/la703175x
https://doi.org/10.1021/la801594q
14. Schneider, A., Brenner, J., Tomastik, C., and Franek, F. Capacity of selected ionic liquids as alternative EP/AW additive. Lubr. Sci., 2010, 22, 215–223.
https://doi.org/10.1002/ls.120
15. Lu, R., Nanao, H., Kobayashi, K., Kubo, T., and Mori, S. Effect of lubricant additives on tribochemical decomposition of hydrocarbon oil on nascent steel surfaces. J. Jpn. Pet. Inst., 2010, 53, 55–60.
https://doi.org/10.1627/jpi.53.55
16. Yu, B., Bansal, D. G., Qu, J., Sun, X., Luo, H., Dai, S., et al. Oil-miscible and non-corrosive phosphonium-based ionic liquids as candidate lubricant additives. Wear, 2012, 289, 58–64.
https://doi.org/10.1016/j.wear.2012.04.015
17. Fraser, K. J. and MacFarlane, D. R. Phosphonium-based ionic liquids: an overview. Aust. J. Chem., 2009, 62, 309–321.
https://doi.org/10.1071/CH08558
18. Lee, K., Hwang, Y., Cheong, S., Choi, Y., Kwon, L., Lee, J., and Kim, S. K. Understanding the role of nanoparticles in nano-oil lubrication. Tribol. Lett., 2009, 35, 127–131.
https://doi.org/10.1007/s11249-009-9441-7
19. Tao, X., Jiazheng, Z., and Kang, X. The ball-bearing effect of diamond nanoparticles as an oil additive. J. Phys. Appl. Phys., 1996, 29, 2932–2937.
https://doi.org/10.1088/0022-3727/29/11/029
20. Chang, L. and Friedrich, K. Enhancement effect of nanoparticles on the sliding wear of short fiber-reinforced polymer composites: a critical discussion of wear mechanisms. Tribol. Int., 2010, 43, 2355–2364.
https://doi.org/10.1016/j.triboint.2010.08.011
21. Xue, Q. J., Liu, W. M., and Zhang, Z. J. Friction and wear properties of the surface modified TiO2 nanoparticle as an additive in liquid paraffin. Wear, 1997, 213, 29–32.
https://doi.org/10.1016/S0043-1648(97)00200-7
22. Hu, Z. S., Lai, R., Lou, F., Wang, L. G., Chen, Z. L., Chen, G. X., and Dong, J. X. Preparation and tribological properties of nanometer magnesium borate as lubricating oil additive. Wear, 2002, 252, 370–374.
https://doi.org/10.1016/S0043-1648(01)00862-6
23. Qui, S., Dong, J., and Chen, G. Tribological properties of CeF3 nanoparticles as additives in lubricating oils. Wear, 1999, 230, 35–38.
https://doi.org/10.1016/S0043-1648(99)00084-8
24. Li, W., Zheng, S., Cao, B., and Ma, S. Friction and wear properties of ZrO2/SiO2 composite nanoparticles. J. Nanopart. Res., 2011, 13, 2129–2137.
https://doi.org/10.1007/s11051-010-9970-x
25. Chiñas-Castillo, F. and Spikes, H. A. Mechanism of action of colloidal solid dispersions. J. Tribol-T. ASME, 2003, 125, 552–557.
26. Mishina, H., Kohno, A., Kanekama, U., Nakajama, K., Mori, M., and Iwase, M. Lubricity of the metallic ultrafine particles. Jpn. J. Tribol., 1993, 38, 1109–1120.
27. Pithawalla, Y. B., Deevi, S. C., and El-Shall, M. S. Preparation of ultrafine and nanocrystalline FeAl powders. Mat. Sci. Eng., 2002, A329–331, 92–98.
28. Takeuchi, S. The mechanism of the inverse Hall-Petch relation of nanocrystals. Scripta Mater., 2001, 44, 1483–1487.
https://doi.org/10.1016/S1359-6462(01)00713-8
29. Hernándes Battez, A., González, R., Viesca, J. L., Fernández, J. E., Diaz Fernández, J. M., Machado, A., et al. CuO, ZrO2 and ZnO nanoparticles as antiwear additive in oil lubricants. Wear, 2008, 265, 422–428.
https://doi.org/10.1016/j.wear.2007.11.013
30. Bartz, W. J. Some investigations on the influence of particle size on the lubricating effectiveness of molybdenum disulfide. ASLE Trans., 1972, 15, 207–215.
https://doi.org/10.1080/05698197208981418
31. Modaressi, A., Sifaoui, H., Mielcarz, M., Domanska, U., and Rogalski, M. Influence of the molecular structure on the aggregation of imidazolium ionic liquids in aqueous solutions. Colloids Surf., A., 2007, 302, 181–185.
https://doi.org/10.1016/j.colsurfa.2007.02.020
32. Tarkanovskaja, M., Välbe, R., Esko, K. P., Mäeorg, U., Reedo, V., Hoop, A., et al. Novel homogeneous gel fibers and capillaries from blend of titanium tetrabutoxide and siloxane functionalized ionic liquid. Ceram. Int., 2014, 40, 7729–7735.
https://doi.org/10.1016/j.ceramint.2013.12.114
33. Välbe, R., Tarkanovskaja, M., Mäeorg, U., Reedo, V., Hoop, A., Kink, I., and Lõhmus, A. Elaboration of hybrid cotton fibers treated with an ionogel/carbon nanotube mixture using a sol-gel approach. Open Chem., 2014, 13, 279–286.
https://doi.org/10.1515/chem-2015-0031
34. Janiak, C. Ionic liquids for the synthesis and stabilization of metal nanoparticles. Z. Naturforsch., 2013, 68b, 1059–1089.
https://doi.org/10.5560/znb.2013-3140
35. Brenna, S., Posset, T., Furrer, J., and Blümel, J. 14N NMR and two-dimensional suspension 1H and 13C HRMAS NMR spectroscopy of ionic liquids immobilized on silica. Chem. – Eur. J., 2006, 12, 2880–2888.
https://doi.org/10.1002/chem.200501193
36. ASTM D4172–94 (1999). Standard Test Method for Wear Preventive Characteristics of Lubricating Fluid (Four-Ball Method). ASTM International, West Conshohocken, PA, 1999.
37. Wasserscheid, P. and Welton, T. Ionic Liquids in Synthesis. WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2002.
https://doi.org/10.1002/3527600701
38. Nicholls, M. A., Do, T., Norton, P. R., Kasrai, M., and Bancroft, G. M. Review of the lubrication of metallic surfaces by zinc dialkyl-dithiophosphates. Tribol. Int., 2005, 38, 15–39.
https://doi.org/10.1016/j.triboint.2004.05.009
39. Qu, J., Chi, M., Meyer, H. M. III, Blau, P. J., Dai, S., and Luo, H. Nanostructure and composition of tribo-boundary films formed in ionic liquid lubrication. Tribol. Lett., 2011, 43, 205–211.
https://doi.org/10.1007/s11249-011-9800-z
40. Qu, J., Blau, P. J., Howe, J. Y., and Meyer, H. M. III. Oxygen diffusion enables anti-wear boundary film formation on titanium surfaces in zinc-dialkyl-dithiophosphate (ZDDP)-containing lubricants. Scripta Mater., 2009, 60, 886–889.
https://doi.org/10.1016/j.scriptamat.2009.02.009
41. Tang, Z. and Li, S. A review of recent developments of friction modifiers for liquid lubricants (2007–present). Curr. Opin. Solid St. M., 2014, 18, 119–139.
https://doi.org/10.1016/j.cossms.2014.02.002
42. Smith, A. M., Parkes, M. A., and Perkin, S. Molecular friction mechanisms across nanofilms of a bilayer-forming ionic liquid. J. Phys. Chem. Lett., 2014, 5, 4032–4037.
https://doi.org/10.1021/jz502188g