Phosphonium-based ionic liquids mixed with stabilized oxide nanoparticles as highly promising lubricating oil additives; pp. 174–183Full article in PDF format
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.
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