Al2O3-modified EG/CH3COONa·3H2O form-stable composite phase change materials for medium and low-temperature waste heat recovery

Abstract

In this study, a novel form-stable composite phase change material (MFCPCM) was synthesized using Al₂O₃ hydrophilic modified expanded graphite (MEG) as the supporting carrier and CH₃COONa·3H₂O (SAT) as the phase change material. By coating Al₂O₃ on the surface of expanded graphite, the water contact angle decreased from 85° to 56°, significantly improving the hydrophilicity of MEG. The adsorption rate of MEG for PCM also increased from 14.6 % to 67.9 % within 40 min. The addition of 12 % MEG effectively prevented the leakage of PCM. The corresponding composite phase change material (MFCPCM-12) exhibited a phase change enthalpy of 239.90 J/g, which remained at 235.33 J/g even after 50 cycles. Compared to pure SAT, the thermal conductivity of MFCPCM-12 was enhanced by 88 %, reaching 3.607 W/(m·K). These findings highlight the superior thermal stability and enhanced thermal conductivity of the MFCPCM based on Al₂O₃-modified EG, indicating that it is a promising candidate for medium and low-temperature thermal energy storage. Future research could focus on optimizing the coating process of Al₂O₃ to further enhance the uniformity and stability of the modification, as well as exploring its compatibility with other PCM to develop more efficient multi-component phase change composites for broader application scenarios.