Microencapsulated heptadecane with calcium carbonate as thermal conductivity-enhanced phase change material for thermal energy storage

Heptadecane (HD) is a useful solid–liquid phase change material (PCM) because of its good thermal energy storage (TES) properties. However, leakage problems throughout the phase change and its relatively low thermal conductivity have significantly restricted its TES utility areas. Simultaneously, to prevent leakage and increase its thermal conductivity, HD was successfully encapsulated in a micro CaCO₃ shell via a self-assembly mechanism. Fourier Transform Infrared (FTIR) analysis determined the chemical structures of the microcapsule's components. X-ray Powder Diffraction (XRD) results confirmed that the crystalline structures of both the HD core and CaCO₃ shell were not impacted during the microencapsulation process. The SEM microstructures showed that the microcapsules had well-defined spherical morphology. Differential Scanning Calorimetry (DSC) measurements revealed that the HD within the capsule had a latent heat storage capacity in the range of 86–147 J/g when it melts and solidifies at around 16 °C. The 1000-times-cycled microcapsules demonstrated remarkable chemical stability and TES dependability. Thermogravimetry (TG) analysis showed that the microcapsules had excellent thermal degradation durability. All the produced microcapsules had greater thermal conductivity than the pure HD. The heat storage and releasing periods of the microcapsules were considerably reduced because of their enhanced thermal conductivity. The results revealed that the synthesised HD@CaCO₃ microcapsules can be evaluated in different TES applications, such as the air conditioning of buildings, thermal management of textiles and thermal preservation of foods.