Preparation and thermal characterization of expanded graphite/multiwalled carbon nanotube-based eutectic salt-composite phase change materials

doi:10.19799/j.cnki.2095-4239.2023.0245

Abstract

Abstract:

The application of single hydrated salts phase change materials is limited owing to disadvantages such as supercooling, phase separation, ease of leaking, and phase change temperature. To address these challenges, researchers must focus on developing composite phase change materials exhibiting high heat storage density, suitable phase change temperature, and high thermal conductivity properties. In this study, a eutectic salt having a mass ratio of 55 to 45 with respect to NH₄Al(SO₄)₂·12H₂O (AASD) to MgSO₄·7H₂O (MSH) eutectic phase change material was prepared. The phase change temperature was 76.4 ℃, and the latent heat of phase change was 189.4 J/g. The X-ray diffraction pattern and Fourier transform infrared spectra of the eutectic salt showed that the eutectic process was physical. 1% CaCl₂·2H₂O was used as a nucleating agent and 1% soluble starch was used as a thickening agent herein. This reduced the the supercooling degree from 34.9 ℃ to 28.0 ℃. Modified expanded graphite (MEG) and multiwalled carbon nanotubes (MWCNTs) were introduced to avoid leakage and improve the low thermal conductivity of the eutectic phase change materials. When the mass fraction of MWCNTs was 0.5%, the thermal conductivity of the composite phase change material (CPCM) reached 8.185 W/(m·K), which was 19.98 times that of the pure eutectic salt. The proportion of eutectic salt was 75.6%, the temperature and enthalpy of the CPCM were 74.3 ℃ and 133.5 J/g, and the supercooling was further reduced to 22.2 ℃. Thermogravimetric analysis showed that mixing the eutectic salt phase change material with MEG-MWCNTs increased the thermal stability of the material. The phase change enthalpy of the CPCM remained unchanged after 100 cycles of heating and cooling, indicating good cyclic stability. The CPCM based on AASD-MSH/MEG-MWCNTs developed in this study is a promising phase change material with suitable temperature, high enthalpy of phase change, large thermal conductivity, and good thermal cycle stability. This material has great potential for various applications.

Key words: eutectic hydrated salts, composite phase change materials, modified expanded graphite, multi-walled carbon nanotubes

CLC Number:

TK 124

Qi ZHANG, Yinlei LI, Yanfang LI, Jun SONG, Xuehong WU, Chongyang LIU, Xueling ZHANG. Preparation and thermal characterization of expanded graphite/multiwalled carbon nanotube-based eutectic salt-composite phase change materials[J]. Energy Storage Science and Technology, 2023, 12(8): 2435-2443.

Figures/Tables 16

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样品	CCD质量分数/%	增稠剂含量	过冷度∆T/K
1	0	0% SS	34.9
2	0.5	1.0% SS	28.1
3	1.0	1.0% SS	28.0
4	1.5	1.0% SS	29.7
5	2.0	1.0% SS	30.9

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