High thermally conductive shape-stabilized phase change composites with dual-aligned carbon nanofiber scaffolds

Phase Change Materials (PCMs) serve as highly effective mediums for latent heat storage owing to their substantial heat storage capacity. However, their practical application encounters limitations stemming from low thermal conductivity (TC) and the potential leakage of the melt medium during phase transitions. Addressing these challenges, we devised a strategy to enhance the heat conduction paths in PCM composites. This involved fabricating a dual-aligned scaffold (D-AS) through the integration of both aligned carbon nanofibers (CNFs) in microscopic structures and directional microporous channels, achieved by combining magnetic alignment and conventional freeze-casting techniques. Furthermore, the D-AS functions as a supportive structure for PCMs, ensuring the phase change material maintains excellent shape stability. Experimental findings indicate that the TC of the D-AS and polyethylene glycol (PEG) composites reaches 5.48 W/(m·K) when the CNFs constitute 16.21 wt%, representing a remarkable 1857.1 % increase compared to pure PEG. The composites also exhibit outstanding shape stability, with PEG leakage effectively prevented by the pores in the scaffold. As a trade-off, the heat storage capacity and thermal storage efficiency of the composites is slightly reduced (146.85 J/g, 89.9 %) due to the increase of CNF weight fraction. This demonstrates that a promising direction was highlight for the preparation of high TC and shape stabilized PCMs in this work.