Preparation of SrTiO₃-microencapsulated palmitic acid by means of a sol–gel approach as thermal energy storage materials

Abstract

A novel SrTiO₃-microencapsulated palmitic acid (PA) was successfully prepared as a phase change material (PCM) a through a sol–gel approach. The product (PA@ SrTiO₃) microcapsules were studied by Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometery (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), to gain information on its chemical composition, morphology, crystallinity and structure. Further the thermal properties of the products were studied through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. The data obtained through XRD and FT-IR proved the presence of the peaks characteristic to PA and SrTiO_3, proving that these ingredients do not react with one another during the course of preparing the samples. SEM data indicated the microcapsules to have a spherical morphology and rough surfaces, and the average diameters of the particles were found to range from 1.5 to 2 µm. TEM studies also confirmed that the PA was fully encapsulated with SrTiO₃. DSC results indicated the microcapsules to undergo phase change behaviors similar o those of pristine PA. Typical samples were found to melt at 66.9 °C, have a latent heat of 48.85 J/g, freeze at 55.7 °C (the latent heat = 43.29 J/g). The microencapsulation ratio of the product was determined as 43.92%. Results of TGA analyses proved that the thermal stability of PA is improved through the encapsulation.