新型六水氯化镁-六水硝酸镁/石墨相氮化碳复合相变材料的制备及其热性能研究

doi:10.11949/0438-1157.20211067

摘要/Abstract

摘要：

我国青海盐湖镁资源的利用率低，带来严重的资源浪费和环境污染，若将镁盐开发为相变储热材料，则可扩大其应用领域，从而促进镁盐资源的充分利用。针对中低温保温隔热的应用需求，在前期工作基础上，选用MgCl₂·6H₂O-Mg（NO₃）₂·6H₂O（MCH-MNH）质量比为41∶59的共晶盐作为相变材料，为降低其过冷度并提高隔热性能，选用多孔介质石墨相氮化碳（g-C₃N₄，CN）作为支撑材料，制备低热导率的MCH-MNH/CN复合相变材料。先将尿素在550℃高温下煅烧得到多孔的CN，再采用吸附法制备出MCH-MNH/CN复合相变材料，并对复合相变材料的形貌、结构与热性能进行了表征和测量。结果表明，共晶盐相变材料均匀地吸附在CN的微孔结构内，其与CN的复合是一个物理过程，没有发生化学反应；复合相变材料的相变温度为55.2℃，相变焓值为92.7 J/g，几乎没有过冷度，其热导率为0.3 W/（m·K），仅是共晶盐MCH-MNH的一半，提高了隔热性能。此外，复合相变材料还具有良好的热稳定性，在中低温保温隔热领域具有应用前景。

关键词: 储热, 六水氯化镁, 六水硝酸镁, 石墨相氮化碳, 复合相变材料, 热稳定性

Abstract:

The low utilization rate of magnesium resources in Qinghai Salt Lake in China has caused serious resource waste and environmental pollution. If magnesium salt is developed as a phase change heat storage material, its application fields can be improved, thereby promoting the full utilization of magnesium salt resources. In view of the application requirements of medium-low temperature heat preservation and heat insulation, this work selects eutectic salt MgCl₂·6H₂O-Mg(NO₃)₂·6H₂O(MCH-MNH) with mass ratio of 41∶59 as phase change material based on previous work. MgCl₂·6H₂O-Mg(NO₃)₂·6H₂O/g-C₃N₄(MCH-MNH/CN) composite phase change material with low thermal conductivity is prepared by using porous graphite carbon nitride (g-C₃N₄, CN) as the support material in order to reduce its supercooling and improve its thermal insulation performance. The porous CN is obtained by calcination of urea at 550℃, then MCH-MNH/CN composite phase change material is prepared by adsorption method. The morphology, structure and thermal properties of the composite phase change material are characterized and measured. The results show that the eutectic salt phase change material is uniformly adsorbed in the microporous structure of CN, and the recombination with CN is a physical process without chemical reaction. The composite phase change material has a phase change temperature of 55.2℃ and phase change enthalpy of 92.7 J/g without supercooling. The thermal conductivity of the composite phase change material is 0.3 W/(m·K), which is only half of thermal conductivity of the eutectic salt MCH-MNH, and the heat insulation performance is improved. In addition, the composite phase change material has good thermal stability and has application prospects in the field of medium and low temperature thermal insulation.

Key words: thermal storage, MgCl₂·6H₂O, Mg(NO₃)₂·6H₂O, g-C₃N₄, composite phase change material, thermal stability

中图分类号:

TQ 115

张文波, 凌子夜, 方晓明, 张正国. 新型六水氯化镁-六水硝酸镁/石墨相氮化碳复合相变材料的制备及其热性能研究[J]. 化工学报, 2021, 72(12): 6399-6406.

Wenbo ZHANG, Ziye LING, Xiaoming FANG, Zhengguo ZHANG. Preparation and thermal properties research of a novel magnesium chloride hexahydrate-magnesium nitrate hexahydrate/graphite phase carbon nitride composite phase change material[J]. CIESC Journal, 2021, 72(12): 6399-6406.

图/表 12

图1 MCH-MNH质量分数分别为75%、80%、85%的MCH-MNH/CN复合相变材料的液漏痕迹照片

Fig.1 Photographs of the liquid leakage traces of MCH-MNH/CN composite phase change materials with 75%, 80%, and 85% mass fractions of MCH-MNH

表1 MCH-MNH/CN复合相变材料3 h加热后滤纸质量变化

Table 1 Mass variation of the filter paper with MCH-MNH/CNcomposite phase change material before and after heating for 3 h

MCH-MNH质量分数	加热前质量/g	加热后质量/g	质量变化/g
75%	0.31	0.32	0.01
80%	0.32	0.32	0
85%	0.32	0.56	0.24

图2 CN(a)、MCH-MNH/CN复合相变材料(b)、MCH-MNH/CN复合相变材料循环50次后(c)的SEM图

Fig.2 SEM images of CN (a) and MCH-MNH/CN composite phase change material before (b) and after (c) 50 thermal cycles

图3 CN的N2吸附/脱附等温曲线(a)，BJH孔径分布曲线(b)和XRD谱图(c)

Fig.3 N2 adsorption/desorption isothermal curve (a) , BJH pore size distribution curve (b) and XRD patterns (c) of CN

图4 CN、MCH-MNH、 MCH-MNH/CN复合相变材料的FTIR图

Fig.4 FTIR spectrum of CN, MCH-MNH and MCH-MNH/CN composite phase change material

图5 MCH-MNH、MCH-MNH/CN复合相变材料的DSC曲线

Fig.5 DSC curves of MCH-MNH and MCH-MNH/CN composite phase change material

表2 MCH-MNH、MCH-MNH/CN复合相变材料的相变特征

Table 2 Phase transformation characteristics of MCH-MNH and MCH-MNH/CNcomposite phase change material

样品	熔化温度/ ℃	凝固温度/ ℃	熔化焓值/ (J/g)	凝固焓值/ (J/g)
MCH-MNH	57.7±0.8	38.6	119.8	110.6
MCH-MNH/CN	55.2±0.7	42.8	92.7	88.1

图6 MCH-MNH和MCH-MNH/CN复合相变材料的T-history曲线

Fig.6 T-history curves of MCH-MNH and MCH-MNH/CN composite phase change material

表3 MCH-MNH、MCH-MNH/CN复合相变材料的热导率

Table 3 Thermal conductivity of MCH-MNH， MCH-MNH/CN composite phase change material

样品	热导率/(W/(m·K))
MCH-MNH	0.62
MCH-MNH/CN	0.30

图7 CN、MCH-MNH、MCH-MNH/CN复合相变材料的TG图

Fig.7 TG curves of CN, MCH-MNH and MCH-MNH/CN composite phase change material

图8 MCH-MNH、MCH-MNH/CN复合相变材料冷热循环50次的DSC曲线

Fig.8 DSC curves of MCH-MNH and MCH-MNH/CN composite phase change material before and after 50 thermal cycles

表4 MCH-MNH、MCH-MNH/CN复合相变材料冷热循环50次前后的相变特征

Table 4 Phase transformation characteristics of MCH-MNH and MCH-MNH/CNcomposite phase change material before and after 50 thermal cycles

样品	循环次数	熔化温度/℃	熔化焓值/(J/g)
MCH-MNH	0	57.7	119.8
	50	31.2	59.0
MCH-MNH/CN	0	55.2	92.7
	50	56.7	90.9

参考文献 33

1	史巍, 王传涛. 相变材料研究综述[J]. 硅酸盐通报, 2015, 34(12): 3517-3522.
	Shi W, Wang C T. Study review on phase change materials[J]. Bulletin of the Chinese Ceramic Society, 2015, 34(12): 3517-3522.
2	Hirmiz R, Teamah H M, Lightstone M F, et al. Performance of heat pump integrated phase change material thermal storage for electric load shifting in building demand side management[J]. Energy and Buildings, 2019, 190: 103-118.
3	Pandey A K, Hossain M S, Tyagi V V, et al. Novel approaches and recent developments on potential applications of phase change materials in solar energy[J]. Renewable and Sustainable Energy Reviews, 2018, 82: 281-323.
4	Khadiran T, Hussein M Z, Zainal Z, et al. Advanced energy storage materials for building applications and their thermal performance characterization: a review[J]. Renewable and Sustainable Energy Reviews, 2016, 57: 916-928.
5	Maleki M, Karimian H, Shokouhimehr M, et al. Development of graphitic domains in carbon foams for high efficient electro/photo-to-thermal energy conversion phase change composites[J]. Chemical Engineering Journal, 2019, 362: 469-481.
6	Fu L L, Wang Q H, Ye R D, et al. A calcium chloride hexahydrate/expanded perlite composite with good heat storage and insulation properties for building energy conservation[J]. Renewable Energy, 2017, 114: 733-743.
7	Huang R, Feng J X, Ling Z Y, et al. A sodium acetate trihydrate-formamide/expanded perlite composite with high latent heat and suitable phase change temperatures for use in building roof[J]. Construction and Building Materials, 2019, 226: 859-867.
8	Zalba B, Marı́n J M, Cabeza L F, et al. Review on thermal energy storage with phase change: materials, heat transfer analysis and applications[J]. Applied Thermal Engineering, 2003, 23(3): 251-283.
9	王会春, 凌子夜, 方晓明, 等. 六水氯化镁相变储热材料的研究进展[J]. 储能科学与技术, 2017, 6(2): 204-212.
	Wang H C, Ling Z Y, Fang X M, et al. Recent progress in the use of magnesium chloride hexahydrate used as a phase change material[J]. Energy Storage Science and Technology, 2017, 6(2): 204-212.
10	Pilar R, Svoboda L, Honcova P, et al. Study of magnesium chloride hexahydrate as heat storage material[J]. Thermochimica Acta, 2012, 546: 81-86.
11	Choi J C, Kim S D. Heat transfer in a latent heat-storage system using MgCl₂·6H₂O at the melting point[J]. Energy, 1995, 20(1): 13-25.
12	Gutierrez A, Ushak S, Galleguillos H, et al. Use of polyethylene glycol for the improvement of the cycling stability of bischofite as thermal energy storage material[J]. Applied Energy, 2015, 154: 616-621.
13	Zahir M H, Mohamed S A, Saidur R, et al. Supercooling of phase-change materials and the techniques used to mitigate the phenomenon[J]. Applied Energy, 2019, 240: 793-817.
14	李玉婷, 周永全, 葛飞, 等. 无机水合盐相变储能材料的过冷及相分离研究进展[J]. 盐湖研究, 2018, 26(1): 81-86.
	Li Y T, Zhou Y Q, Ge F, et al. Supercooling and phase separation of inorganic salt hydrates as phase change materials[J]. Journal of Salt Lake Research, 2018, 26(1): 81-86.
15	El-Sebaii A A, Al-Heniti S, Al-Agel F, et al. One thousand thermal cycles of magnesium chloride hexahydrate as a promising PCM for indoor solar cooking[J]. Energy Conversion and Management, 2011, 52(4): 1771-1777.
16	Nagano K, Ogawa K, Mochida T, et al. Thermal characteristics of magnesium nitrate hexahydrate and magnesium chloride hexahydrate mixture as a phase change material for effective utilization of urban waste heat[J]. Applied Thermal Engineering, 2004, 24(2/3): 221-232.
17	Nagano K, Ogawa K, Mochida T, et al. Performance of heat charge/discharge of magnesium nitrate hexahydrate and magnesium chloride hexahydrate mixture to a single vertical tube for a latent heat storage system[J]. Applied Thermal Engineering, 2004, 24(2/3): 209-220.
18	Galazutdinova Y, Vega M, Grágeda M, et al. Preparation and characterization of an inorganic magnesium chloride/nitrate/graphite composite for low temperature energy storage[J]. Solar Energy Materials and Solar Cells, 2018, 175: 60-70.
19	Zhou Y, Sun W C, Ling Z Y, et al. Hydrophilic modification of expanded graphite to prepare a high-performance composite phase change block containing a hydrate salt[J]. Industrial & Engineering Chemistry Research, 2017, 56(50): 14799-14806.
20	Zhou S Y, Zhou Y, Ling Z Y, et al. Modification of expanded graphite and its adsorption for hydrated salt to prepare composite PCMs[J]. Applied Thermal Engineering, 2018, 133: 446-451.
21	Ling Z Y, Liu J W, Wang Q H, et al. MgCl₂·6H₂O-Mg(NO₃)₂·6H₂O eutectic/SiO₂ composite phase change material with improved thermal reliability and enhanced thermal conductivity[J]. Solar Energy Materials and Solar Cells, 2017, 172: 195-201.
22	Zhang C, Zhang Z Y, Ye R D, et al. Characterization of MgCl₂·6H₂O-based eutectic/expanded perlite composite phase change material with low thermal conductivity[J]. Materials, 2018, 11(12): 2369.
23	Ling Z Y, Li S M, Zhang Z G, et al. A shape-stabilized MgCl₂·6H₂O-Mg(NO₃)₂·6H₂O/expanded graphite composite phase change material with high thermal conductivity and stability[J]. Journal of Applied Electrochemistry, 2018, 48(10): 1131-1138.
24	Liu J H, Zhang T K, Wang Z C, et al. Simple pyrolysis of urea into graphitic carbon nitride with recyclable adsorption and photocatalytic activity[J]. Journal of Materials Chemistry, 2011, 21(38): 14398.
25	Yuan Y P, Xu W T, Yin L S, et al. Large impact of heating time on physical properties and photocatalytic H₂ production of g-C₃N₄nanosheets synthesized through urea polymerization in Ar atmosphere[J]. International Journal of Hydrogen Energy, 2013, 38(30): 13159-13163.
26	Zhang Y W, Liu J H, Wu G, et al. Porous graphitic carbon nitride synthesized via direct polymerization of urea for efficient sunlight-driven photocatalytic hydrogen production[J]. Nanoscale, 2012, 4(17): 5300-5303.
27	Mo Z, She X J, Li Y P, et al. Synthesis of g-C₃N₄ at different temperatures for superior visible/UV photocatalytic performance and photoelectrochemical sensing of MB solution[J]. RSC Advances, 2015, 5(123): 101552-101562.
28	Gu Q, Gao Z W, Zhao H, et al. Temperature-controlled morphology evolution of graphitic carbon nitride nanostructures and their photocatalytic activities under visible light[J]. RSC Advances, 2015, 5(61): 49317-49325.
29	Martin D J, Qiu K P, Shevlin S A, et al. Highly efficient photocatalytic H₂ evolution from water using visible light and structure-controlled graphitic carbon nitride[J]. Angewandte Chemie, 2014, 126(35): 9394-9399.
30	Niu P, Yin L C, Yang Y Q, et al. Increasing the visible light absorption of graphitic carbon nitride (melon) photocatalysts by homogeneous self-modification with nitrogen vacancies[J]. Advanced Materials, 2014, 26(47): 8046-8052.
31	Hwang S, Lee S, Yu J S. Template-directed synthesis of highly ordered nanoporous graphitic carbon nitride through polymerization of cyanamide[J]. Applied Surface Science, 2007, 253(13): 5656-5659.
32	Lu X, Huang H W, Zhang X Y, et al. Novel light-driven and electro-driven polyethylene glycol/two-dimensional MXene form-stable phase change material with enhanced thermal conductivity and electrical conductivity for thermal energy storage[J]. Composites Part B: Engineering, 2019, 177: 107372.
33	Ling Z Y, Li S M, Cai C Y, et al. Battery thermal management based on multiscale encapsulated inorganic phase change material of high stability[J]. Applied Thermal Engineering, 2021, 193: 117002.

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