膨胀石墨/多壁碳纳米管基共晶盐复合相变材料的制备及热特性

doi:10.19799/j.cnki.2095-4239.2023.0245

摘要/Abstract

摘要：

单一水合盐作为相变蓄热材料使用时常常由于过冷、相分离、易泄漏以及其相变温度而受到限制，因此迫切需要制备出一种储热密度高、相变温度适宜、热导率大的复合相变材料。本工作采用熔融共混法在NH₄Al(SO₄)₂·12H₂O(AASD)中掺入不同质量分数的MgSO₄·7H₂O(MSH)，成功制备了AASD-MSH共晶盐相变材料，其质量比为55∶45，相变温度为76.4 ℃，相变潜热为189.4 J/g。共晶盐的X射线衍射图谱和傅里叶红外光谱表明其为物理混合。引入质量分数1%成核剂CaCl₂·2H₂O及1%增稠剂可溶性淀粉降低共晶盐过冷度，过冷度从34.9 ℃降低至28.0 ℃。引入改性膨胀石墨(MEG)与多壁碳纳米管(MWCNTs)制备复合相变材料，改善共晶盐易泄漏及热导率低等问题，当MWCNTs质量分数为0.5%时，复合相变材料的热导率高达8.185 W/(m·K)，为共晶盐的19.98倍，其中共晶盐占比为75.6%，相变温度为74.3 ℃，相变焓值为133.5 J/g，过冷度进一步降低至22.2 ℃。热重实验表明与MEG-MWCNTs的复合增加了共晶盐的热稳定性，且经过100次冷热循环后复合相变材料的相变焓值基本不变，具有良好的循环稳定性。本工作制备得到的AASD-MSH/MEG-MWCNTs复合相变材料是一种相变温度适合、相变焓值较高、热导率较大的相变材料，且具有良好的热循环稳定性，应用潜力极大。

关键词: 共晶水合盐, 复合相变材料, 改性膨胀石墨, 多壁碳纳米管

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

中图分类号:

TK 124

张琦, 李银雷, 栗艳芳, 宋俊, 吴学红, 刘重阳, 张雪龄. 膨胀石墨/多壁碳纳米管基共晶盐复合相变材料的制备及热特性[J]. 储能科学与技术, 2023, 12(8): 2435-2443.

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.

图/表 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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