Synthesis and thermal properties of fatty acid eutectics and diatomite composites as shape-stabilized phase change materials with enhanced thermal conductivity

• Shape-stabilized fatty acid eutectics and diatomite composites were prepared.
• The eutectic mixtures were dispersed in the diatomite with no chemical interaction.
• The CPCM3 with 5% EG melts at 26.69 °C with a latent heat of 98.26 kJ kg−1.
• Thermal conductivity of the CPCM3 with 5% EG can increase by 25.2%.

In this study, shape-stabilized fatty acid eutectics and diatomite composites were prepared by absorbing liquid fatty acid eutectics into diatomite. The thermal properties of the composites were measured by differential scanning calorimetry (DSC). In the composites, the eutectic mixtures acted as phase change materials (PCMs) for thermal energy storage, and the diatomite was used as supporting material. Expanded graphite (EG) was added to help prevent the eutectic mixtures from leakage and enhance thermal conductivity of the composite phase change materials (CPCMs). Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD) and scanning electronic microscope (SEM) were used to survey the chemical structure, crystalloid phase and microstructure of the eutectic mixture/diatomite composites. The DSC results showed that the satisfactory sample melts at 26.69 °C with a latent heat of 98.26 kJ kg−1 and solidifies at 21.85 °C with a latent heat of 90.03 kJ kg−1 when the mass ratio of the eutectic mixture to the diatomite is 2:1 with 5% EG. According to the results of the Thermal Conductivity Meter (TCM), the EG could enhance the thermal conductivity of the composites. The thermal reliability of the composites was investigated by a thermogravimetric analyzer (TGA). The results indicated that the satisfactory CPCMs have good thermal stability, which can be used as shape-stabilized phase change materials for thermal energy storage.