High thermal conductivity phase change composite with percolating carbon fiber network

Highlights: • A phase change composite with a percolating network of carbon fiber was developed. • The composites were prepared by the melt-dispersion and hot-press methods. • The composites prepared by the hot-press had a percolating network of carbon fiber just using 20 vol% of it. • The composites with the percolating network had high thermal conductivity. • The phase change material particles with high packing ratio accelerated percolation. - Abstract: Latent heat storage (LHS) using phase change materials (PCM) is a promising technology for the effective use of solar and industrial exhaust heat. However, the heat transfer rate of an LHS system is severely limited by the low thermal conductivity of the PCM. Therefore, this paper describes the development of a high thermal conductivity phase change composite (PCC) with a percolating network of a high thermal conductivity filler. The relationship between the effective thermal conductivity of the PCC and the network structure of the filler was investigated. The PCC were prepared by the conventional melt-dispersion (MD) method and a novel hot-press (HP) method. Erythritol (melting point: 118 °C, thermal conductivity: 0.73 W m⁻¹ K⁻¹) was used as the PCM, and carbon fiber (thermal conductivity: 900 W m⁻¹ K⁻¹ in the fiber direction) was used as the high thermal conductivity filler. The effective thermal conductivity of the PCC was measured by the laser flash method and the network structures were observed by energy dispersive spectroscopy using a scanning electron microscope. As a result, we observed that the percolating filler network in the PCC could be easily formed by the HP method, presenting a higher thermal conductivity with less filler additive than the PCC fabricated by the MD method. Additionally, we found that PCM raw materials with a high packing ratio accelerated the formation of the percolating filler network