A thermally stable phase change material with high latent heat based on an oxalic acid dihydrate/boric acid binary eutectic system

An oxalic acid dihydrate/boric acid (OCD-BA) binary eutectic mixtures containing 88 wt% OCD and 12 wt% BA was investigated as a novel phase change material (PCM) with high latent heat and thermal stability. The solid-liquid phase diagram of binary systems is established, and the phase change temperature of OCD-BA binary eutectic mixture is 87.3 °C and the latent heats of the melting and crystallization process are 344 J g−1 and 262 J g−1, respectively. Its thermophysical properties and thermal stability were studied using differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and Scanning electron microscopy-Energy dispersive spectroscopy (SEM-EDS). Its thermal stability was investigated in situ through 100 cycles using DSC and 1000 thermal cycling tests using Refrigerated and heating circulators (RHC). The latent heat of melting still exceed 280 J g−1 after 1000 heating/cooling cycles. The heat release platform sustained 5 h at more than 70.0 °C, and the degree of supercooling was only 1.0 °C according to T-history method. These results indicate that the newly prepared OCD-BA binary eutectic mixture is a potential PCM for thermal storage tanks.