Thermophysical Properties of 1-Butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, [C₄mim][(C₂F₅)₃PF₃], and of Its IoNanofluid with Multi-Walled Carbon Nanotubes

Thermophysical properties of 1-butyl-3-methylimidazoliumtris(pentafluoroethyl) trifluorophosphate, [C4mim][(C2F5)3PF3] (CAS RN 917762-91-5) ionic liquid, were measured in the temperature range T = (283.15-353.15) K, at P = 0.1 MPa. These properties include density, isobaric heat capacity, speed of sound, refractive index, viscosity, and thermal conductivity and their correlation as a function of temperature. Data obtained were compared with the available literature, whenever available. Comparison of these results with those reported for ILs with the same cation or anion is presented and discussed. Derived quantities such as isobaric expansivity and isothermal and isentropic compressibility were also estimated. Arrhenius, Ghatee, Vogel-Fulcher-Tammann, and IUPAC equations were applied to correlate viscosity data dependence on temperature, the last one being more effective and accurate. An estimation method for thermal conductivity of ILs was applied. Calculated values by this equation deviate from the experimental data between -15.6% at 293 K and -17.9% at 353 K, within the mutual uncertainty of these data and estimation. The thermal conductivity of the IoNanofluid made from the dispersion of multi-walled carbon nanotubes (1% wt MWCNTs) in [C4mim][(C2F5)3PF3] was determined. The enhancement in thermal conductivity due to the presence of MWCNTs was found to vary between 4% at 293 K and 9.6% at 353 K, an average of 6.2%, weakly dependent on temperature.