A novel stearic acid/expanded graphite/Fe3O4 composite phase change material with effective photo/electro/magneto-triggered thermal conversion and storage for thermotherapy applications

Composite phase change materials (CPCMs) have demonstrated high potential in thermotherapy; however, their poor energy conversion limits thermal−charge performance, thus negatively affecting their practical applications. Herein, we combined stearic acid (SA), expanded graphite (EG), and Fe₃O₄ nanoparticles (NPs) to obtain an 80 wt% SA/EG/Fe₃O₄ CPCM with multisource−triggered thermal conversion and storage abilities. The CPCM was equipped with a photothermal conversion facilitated by high light absorption of EG and localized surface plasmon resonance of Fe₃O₄. The high electrical conductivity of EG also offered the CPCM with an effective electrothermal conversion. An accelerated magnetothermal conversion was further achieved for the CPCM owing to the superparamagnetism of Fe₃O₄ NPs. Resultantly, the 80 wt% SA/EG/Fe₃O₄ CPCM could be facily charged as applied with either low−energy electricity (2.0 V), actual sunlight radiation (98−110 mW/cm²), or alternating magnetic field (120 W). In addition, it exhibited relatively high thermal storage capacity (152.4 J/g), excellent leakage resistance, and high thermal stability, conductivity, and cycling reliability. As in the form of a heat pack, the 80 wt% SA/EG/Fe₃O₄ CPCM maintained a heat release to a human back within 50–52 °C for 34 min, overtaking the criteria for high−temperature thermotherapy. The proposed multisource−triggered thermal conversion abilities and suitable thermal properties made SA/EG/Fe₃O₄ CPCM promising for multiple energy utilization and practical thermotherapy applications.