Preparation and thermal properties of n–octadecane/stearic acid eutectic mixtures with hexagonal boron nitride as phase change materials for thermal energy storage

Abstract

This work focuses on preparing n–octadecane (ODE) and stearic acid (SA) eutectics which contain hexagonal boron nitride (HBN) to improve thermal conductivity of the composites. In the composites, the SA–ODE eutectic mixtures acted as phase change materials (PCMs) for thermal energy storage, the HBN was introduced to enhance the thermal conductivity. Analysis methods such as Fourier transformation infrared spectroscope (FT–IR), X–ray diffractometer (XRD) and scanning electronic microscope (SEM) were used to test the chemical bonding, crystalloid phase and morphology of the eutectic mixture/hexagonal boron nitride composites. The thermal properties, thermal stability and thermal conductivity were measured by the differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA) and thermal conductivity meter (TCM), respectively. It was shown that there was no chemical reaction between the SA–ODE eutectic and HBN, and the composite PCMs (CPCMs) had good thermal stability. The thermal conductivities of the melted/solidified CPCMs increased because of adding HBN, whereas their latent heat of fusion slightly decreased. The SA–ODE eutectic with 10wt% HBN was chosen as satisfactory CPCM. It melted at 27.89°C with the latent heat of 207.6kJ/kg and solidified at 26.53°C with the latent heat of 202.05kJ/kg. It is envisioned that the prepared SA–ODE/HBN composites have application prospect as PCMs in thermal energy storage.