Advancing Thermal Energy Storage: Synthesis and Thermal Performance of Silica-Encapsulated Paraffin PCMs

This study successfully synthesizes SiO₂-encapsulated nano-phase change materials (NPCMs) via a sol-gel method, using paraffin as the thermal storage medium. The encapsulation process is validated through FTIR, XRD, and XPS analyses, confirming the formation of an amorphous SiO₂ shell without any chemical interaction between the core and shell. SEM imaging reveals a well-defined core-shell structure with uniform spherical geometry, with the smallest particle size (190 nm) observed in the sample with a 4:1 paraffin/SiO₂ ratio (PARSI-4). TGA results demonstrate enhanced thermal stability, with thicker SiO₂ shells effectively protecting against thermal degradation. The DSC analysis indicates that an increased core-shell ratio improves thermal performance, with PARSI-4 exhibiting the highest melting (160.86 J/g) and solidifying (153.93 J/g) enthalpies. The encapsulation ratio (ER) and encapsulation efficiency (EE) have been accomplished at 87.83% and 87.04%, respectively, in the PARSI-4 sample. Thermal cycling tests confirm the material's long-term stability, with 98.16% enthalpy retention even after 100 cycles. Additionally, leakage resistance tests validate the structural integrity of the encapsulated paraffin, preventing spillage at elevated temperatures. These findings demonstrate the potential of SiO₂-encapsulated NPCMs for efficient thermal energy storage (TES), making them promising candidates for sustainable and energy-efficient applications.