Determination of the Vapor Pressure and Evaporation Enthalpy of CeO2 Nano-Fuels Based on Isothermogravimetry.

The addition of nanoparticles to base fuel may bring about remarkable changes in a thermodynamic process such as evaporation, due to the intensified interaction between particles and liquid molecules. In this study, the nano-fuels containing the 20 nm and 50 nm cerium oxide (CeO2) particles with the dosing levels of 50 mg·L−1 and 100 mg·L−1 were prepared using N-tetradecane (C14) as base fuel and cetyltrimethyl ammonium bromide as dispersant. The evaporation characteristics of nano-fuels were investigated via a constant temperature thermogravimetric method. The thermodynamic parameters of nano-fuel evaporation process, such as activation energy, vapor pressure and evaporation enthalpy, were calculated based on Arrhenius equation, Antoine and Langmuir equations and Clausius–Clapeyron equation, respectively. It was revealed that the particle size and mass fraction of CeO2 nanoparticles had a consistent effect on the activation energy, vapor pressure and evaporation enthalpy of nano-fuels. The activation energy required for vaporization increased with the decrease of nanoparticle size or the increase of nanoparticle mass fraction, because of the low-specific heat capacity of nanoparticles. Moreover, the vapor pressure decreased with the decrease of nanoparticle size or the increase of the mass fraction for particle. This is because the addition of nanoparticles could augment the surface tension of fuel, retarding the diffusion of liquid phase molecules into gas phase. The evaporation enthalpy of nano-fuels increased due to the Van der Waals forces between fuel molecules and nanoparticles. [ABSTRACT FROM AUTHOR]