Evaluation of the thermal properties of SrCO3-microencapsulated palmitic acid composites as thermal energy storage materials

Abstract

A novel composite of SrCO₃-microencapsulated palmitic acid (PA) (PA@SrCO₃ microcapsules) was prepared an evaluated as a phase-change material through a self-assembly approach. Samples of the material were studied by Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometery (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to determine the composition, crystalloid phase, microstructure, and morphology of the product. Also differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to monitor the thermal behavior of the PA@SrCO₃ microcapsules. The data obtained through XRD and FTIR indicated the presence of characteristic peaks of PA and SrCO₃, which is only possible when the species do not chemically react with each other. SEM images indicated the PA@SrCO₃ microcapsules to be spheres with rough surfaces and average diameters of 1.5–2 µm. TEM images proved the samples as being composed of PA cores encapsulated in a SrCO₃ coating. The DSC results showed that the samples had phase-change behaviors, similar to those of pristine PA (melting point = 66.9 °C, latent melting heat = 48.8 J g⁻¹, freezing point = 55.7 °C, latent freezing heat = 43.2 J g⁻¹, at a microencapsulation ratio of 43.92%), and TGA results showed improvements in the thermal stability of PA@SrCO₃ microcapsules as opposed to PA, due to the presence of the SrCO₃ shell.