The effect of nanoparticles on the physicochemical and thermal properties of different organic eutectic mixtures

Abstract

This final project investigated the effect of SiO2 nanoparticles on the thermal and physicochemical properties of various organic eutectic mixtures, with the aim of improving their properties for application in phase-change materials (PCMs) for energy applications. PCMs are compounds with a high capacity to store and release thermal energy during phase-change processes, making them key materials for achieving greater sustainability and energy efficiency in various sectors such as construction, electronics, and thermal storage systems. A total of five binary eutectic mixtures consisting of fatty acids and esters were synthesized: capric acid/ethyl stearate (CA/ES), capric acid/ethyl myristate (CA/EM), capric acid/methyl palmitate (CA/PM), ethyl myristate/palmitic acid (EM/PA), and capric acid/palmitic acid (CA/PA). However, only three of them (CA/PA, CA/EM, and CA/ES) were fully characterized due to reagent availability issues. Eutectic concentrations were determined by differential scanning calorimetry (DSC) using the STARe Evaluation program, selecting those ratios that showed a single melting peak in the thermogram. From these, modified versions containing 1% by weight of SiO2 nanoparticles were prepared and dispersed using ultrasound. The samples were characterized using differential scanning calorimetry (DSC) to determine their enthalpy of fusion and heat capacity (cp) and using the Hot Disk method to evaluate their thermal conductivity. The results indicate that the addition of nanoparticles increases cp and thermal conductivity, while the enthalpy of fusion decreases. The latter property presents negative values, as it is an endothermic process in which the material absorbs heat to change phase. The main experimental limitation arose when attempting to measure the thermal conductivity of the CA/PA and CA/ES eutectics. Since their melting temperatures were close to the test temperature, the energy released by the sensor caused the compounds to melt, invalidating the results. In conclusion, the results obtained show that the incorporation of SiO2 nanoparticles modifies the thermal properties of the PCMs studied, suggesting a potentially positive impact on their efficiency and use in practical applications. Among these, the most notable uses are in construction materials, electronic components, and thermal energy storage systems, where improved thermal conductivity and thermal stability can provide significant benefits.