Dual-network aerogel based composite eutectic phase change material with compound nucleation for building thermal management

Eutectic inorganic hydrated salts are promising for passive building thermal management but are hindered by severe supercooling, phase separation, and leakage. To overcome these challenges, this study developed a novel composite eutectic phase change material (CEPCM) based on a dual-network aerogel with compound nucleation. Sodium acetate trihydrate (SAT) and sodium thiosulfate pentahydrate (STP) were selected as the eutectic PCM, while borax and nano-TiO₂ served as compound nucleating agents to synergistically suppress supercooling and prevent phase separation. A polyvinyl alcohol/starch/expanded graphite (PVA/starch/EG) dual-network aerogel was synthesized as a porous, shape-stable supporting matrix to encapsulate the PCM and prevent leakage. The resulting CEPCM exhibits a high phase change enthalpy of 181.4 J/g, an extremely low supercooling degree of 1.1 °C, and excellent shape stability with no leakage. It also demonstrates good flame retardancy (LOI > 95%), high compressive strength (62.437Mpa), and stable performance over 150 thermal cycles. When integrated into a roof module in a scaled building model, the CEPCM significantly reduced indoor temperature fluctuations and delayed heat penetration, confirming its strong potential for energy-efficient building thermal management.