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Expanded graphite (EG) is often used to encase phase change materials (PCMs) and improve their thermal performance. However, EG's effectiveness when used with disodium hydrogen phosphate dodecahydrate (DHPD) as a hydrated salt is diminished, due to its hydrophobic property. This study proposes modifying the hydrophobic surface of EG with highly hydrophilic nanoparticles, such as SiO 2 and TiO 2 , to address this shortcoming and boost its hydrophilicity. Herein, the nanoparticles were synthesized by the sol-gel technique and mixed with EG to construct a modified EG (MEG). The microstructure, morphology, and adsorption ability of MEG were analyzed. Additionally, the thermal properties, as well as the thermal stability of form-stable composite PCMs, were investigated. The results revealed that by varying the mass ratio of SiO 2 @TiO 2 in MEG, the supercooling degree of the form-stable composite PCMs decreased by 77.36%–78.49%. With 9% SiO 2 @TiO 2 in MEG, the water contact angle of MEG was optimal, and the form-stable composite PCMs prepared (DSMEG3) exhibited a phase change temperature and latent heat of 32.88 °C and 142.13 J/g, respectively. This experimental latent heat was slightly lower than the calculated latent heat by 0.12 J/g. Meanwhile, the supercooling degree decreased to 3.01 °C, and the thermal conductivity increased to 1.23 W/(m ∙ K), which was 1.73 times than that of DHPD. Moreover, DSMEG3 also showed good shape stability, preventing leakage. Therefore, the form-stable composite PCMs, as prepared, are a great potential candidate for the energy storage applications. [ABSTRACT FROM AUTHOR]

Expanded graphite (EG) is often used to encase phase change materials (PCMs) and improve their thermal performance. However, EG's effectiveness when used with disodium hydrogen phosphate dodecahydrate (DHPD) as a hydrated salt is diminished, due to its hydrophobic property. This study proposes modifying the hydrophobic surface of EG with highly hydrophilic nanoparticles, such as SiO 2 and TiO 2 , to address this shortcoming and boost its hydrophilicity. Herein, the nanoparticles were synthesized by the sol-gel technique and mixed with EG to construct a modified EG (MEG). The microstructure, morphology, and adsorption ability of MEG were analyzed. Additionally, the thermal properties, as well as the thermal stability of form-stable composite PCMs, were investigated. The results revealed that by varying the mass ratio of SiO 2 @TiO 2 in MEG, the supercooling degree of the form-stable composite PCMs decreased by 77.36%–78.49%. With 9% SiO 2 @TiO 2 in MEG, the water contact angle of MEG was optimal, and the form-stable composite PCMs prepared (DSMEG3) exhibited a phase change temperature and latent heat of 32.88 °C and 142.13 J/g, respectively. This experimental latent heat was slightly lower than the calculated latent heat by 0.12 J/g. Meanwhile, the supercooling degree decreased to 3.01 °C, and the thermal conductivity increased to 1.23 W/(m ∙ K), which was 1.73 times than that of DHPD. Moreover, DSMEG3 also showed good shape stability, preventing leakage. Therefore, the form-stable composite PCMs, as prepared, are a great potential candidate for the energy storage applications. [ABSTRACT FROM AUTHOR]