No abstract

After doing several miscibility essays with eight ionic liquids (ILs) and four base oils, the ILs tri(butyl)ethylphosphonium diethylphosphate [P4,4,4,2][C2C2PO4] and trihexyl(tetradecyl)phosphonium tris(pentafluoroethyl)trifluorophosphate [P6,6,6,14][(C2F5)3PF3] were selected to be studied as lubricant additives. The neat IL [P4,4,4,2][C2C2PO4], the base oils, and several blends were characterized in terms of density, viscosity, and thermal stability. The tribological performance of the miscible base oil/IL blends (1 wt %) and the neat [P4,4,4,2][C2C2PO4] were evaluated for the lubrication of an AISI 420 steel-100Cr6 steel contact pair. The friction coefficients and wear volumes obtained are also compared with those corresponding to the pure base oils and their mixtures with conventional additive zinc dialkyldithiophosphate (ZDDP). As neat lubricants, [P4,4,4,2][C2C2PO4] showed the best antifriction ability, whereas in terms of wear, better results were obtained with [P6,6,6,14][(C2F5)3PF3]. However, higher improvements in both friction and wear were found for blends containing [P4,4,4,2][C2C2PO4]. XPS analyses of the worn surfaces lubricated with these mixtures indicated the presence of phosphorus in the tribofilm formed on the wear track. However, this compound was slightly detected on tribosamples lubricated with blends containing [P6,6,6,14][(C2F5)3PF3].

No abstract

The thermal stability of three ionic liquids (ILs) with the same anion and different lengths of imadazolium cations was investigated using thermogravimetric analysis to consider their usefulness for their potential application as absorbents in absorption heat pumps and refrigeration cycles. First, the influence of experimental conditions such as sample mass, heating rate, and atmosphere was analyzed for one of these ILs. Afterward, dynamic and isothermal studies were performed for the three ILs. From dynamic results, onset temperature has been often selected to define the thermal stability. Nevertheless, to obtain a more precise value, long-term isothermal studies at temperatures lower than the onset one were required, showing that the thermal stability decreases slightly as the length of the cations increases. Using the Arrhenius relationship, the kinetics of isothermal decomposition was also evaluated, and an upper limit for the “working” time of these ILs as potential absorbents was estimated.

No abstract

No abstract

No abstract

No abstract