Analysis of electrical resistivity of expanded graphite/paraffin composite phase change material

doi:10.12028/j.issn.2095-4239.2018.0209

Abstract

Abstract: Expandable graphite-paraffin composite phase change materials were prepared by a melt-blending process. The resistivity of natural flake graphite, purified graphite, expandable graphite, paraffin-expanded graphite composite phase change materials formed at different pressures was measured using a semiconductor powder resistivity tester. The results showed that the resistivity of all materials decreased with increasing pressure, seven repeated tests were performed on the material with the best thermal conductivity, and the resistivity of the material varied between 0.210-0.535 Ω·cm, which was lower than 11 Ω·cm and hence can be classified as a low-resistivity material. According to the measurement data, the amount of heat storage per unit volume, density, volume and resistance of the composite phase change materials were calculated. The amount of heat storage per unit volume and density of the material increased with increasing pressure, however, the resistivity and volume showed the opposite as expected. The physical properties of materials were found to be stable when the formation pressure was between 4 and 10 MPa; at about 10 MPa, the resistivity of the phase change material was 884 times larger than that of natural scale graphite, 1.9 times the volume and 0.6 times the density. The amount of heat storage per unit volume was 22.8% higher than that at 4 MPa. It was shown that the expanded graphite/paraffin composite was a low resistivity phase transition material, which can be applied on asphalt pavement, achieving both heating up and cooling down effects.

Key words: natural flake graphite, expandable graphite, composite phase change material, resistivity

CLC Number:

TB332

XU Zhong, HUANG Ping, WU En'hui, HOU Jing, LI Jun, LIU Qianshu. Analysis of electrical resistivity of expanded graphite/paraffin composite phase change material[J]. Energy Storage Science and Technology, 2019, 8(2): 371-378.

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