Preparation and properties of nano phase change microcapsules for heat storage

doi:10.16085/j.issn.1000-6613.2022-2330

Abstract

Abstract:

Leakage prevention and thermal conductivity improvement of phase change materials are two key issues for energy storage of phase change materials. In this work, nano-TiO₂@n-docosane microcapsules were prepared by fine emulsion interfacial polymerization using tetrabutyl titanate (TBT) as precursor. The formation process was observed by biomicroscopy, and the properties of nano-TiO₂@n-docosane microcapsules were characterized by scanning electron microscope (SEM), differential scanning calorimeter (DSC), thermal conductivity meter and thermogravimetric analyzer. The experimental results showed that the formation process of nano-TiO₂@n-docosane microcapsules was that the number of nano-microcapsules changed from less to more, the particle size from small to large, the interface of microscopic solution from blurred to clear, and the aging and cooling process of solution was gradually from gelation suspension state to powder precipitation state. The results of SEM test indicated that the particle size of nano-TiO₂@n-docosane microcapsules was significantly related to rotational speed, and the appearance was closely related to the dosage of TBT, hydrochloric acid (HCl) and sodium dodecyl sulfate (SDS). The DSC results showed that the melting and solidification temperatures were 41.3℃ and 42.4℃, respectively. The latent heat of nano-TiO₂@n-docosane was 178J/g. The coating rate and the coating efficiency were 70.7% and 69.0%, respectively with the heat storage capacity of 97.6%. The average thermal conductivity of nano-TiO₂@n-docosane microcapsules was 215% of n-docosane. It was found from the infrared spectrum test that there was no chemical reaction when n-docosane and TiO₂ were physically combined. The results of thermogravimetric analysis indicated that TiO₂formed a physical protective barrier and slowed down the diffusion of n-docosane outside the capsule.

Key words: phase change, enthalpy, stability, nano microcapsules, n-docosane, titanium dioxide

摘要：

防止相变材料的泄漏和提高热导率是相变材料储能的两大关键问题。本文以钛酸四丁酯（TBT）为前体，通过细乳液界面聚合法制备了nano-TiO₂@n-docosane微胶囊。采用生物显微镜对其形成过程进行观察，利用扫描电子显微镜（SEM）、差示扫描量热仪（DSC）、热导率测定仪和热重分析仪对nano-TiO₂@n-docosane微胶囊的性能进行了表征。研究结果表明，nano-TiO₂@n-docosane微胶囊形成过程表现为纳米微胶囊数量由少变多、粒径由小变大、微观溶液界面由模糊变清晰的过程，溶液陈化放冷过程表现为由胶凝悬浮状态逐渐转变为粉末沉淀状态。nano-TiO₂@n-docosane微胶囊粒径与转速显著相关，外貌形态与TBT、盐酸（HCl）和十二烷基硫酸钠（SDS）用量密切相关。纳米相变微胶囊的融化和凝固温度分别为41.3℃和42.4℃，相变焓为178J/g，包覆率和包覆效率达到70.7%和69.0%，蓄热能力为97.6%。nano-TiO₂@n-docosane微胶囊平均热导率是n-docosane的215%。红外光谱测试结果表明，n-docosane和TiO₂物理结合，n-docosane成功被TiO₂包覆。热重分析表明TiO₂形成了一个物理保护屏障，减缓了n-docosane向胶囊外的扩散。

关键词: 相变, 焓, 稳定性, 纳米微胶囊, 正二十二烷, 二氧化钛

CLC Number:

TK02

HUANG Zhiguo, SUN Zhigao. Preparation and properties of nano phase change microcapsules for heat storage[J]. Chemical Industry and Engineering Progress, 2023, 42(11): 5842-5851.

黄志国, 孙志高. 蓄热用纳米相变微胶囊制备与性能[J]. 化工进展, 2023, 42(11): 5842-5851.

Figures/Tables 13

References 37

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名称	型号	精度	测量范围
生物显微镜	XSP-BM-3C	—	40~1600倍
赛多利斯电子天平	BSA224S	±0.1mg	0~220g
数控超声波清洗器	KQ100DE	—	RT+10~80℃
微电热恒温水槽	THD-2015	±0.1℃	-20~99℃
差示扫描量热仪	NETZSCH DSC 200F3	—	-180~725℃
傅里叶红外光谱仪	Thermo Scientific Nicolet iS20	—	4000~400cm^-1
真空干燥箱	BZF-30	±0.5℃	RT+2~250℃
扫描电子显微镜	蔡司Gemini300/Nova NanoSEM450	—	—
热导率测定仪	DRE-Ⅲ	≤3%	0.005~50W/(m•K)

名称	型号	精度	测量范围
生物显微镜	XSP-BM-3C	—	40~1600倍
赛多利斯电子天平	BSA224S	±0.1mg	0~220g
数控超声波清洗器	KQ100DE	—	RT+10~80℃
微电热恒温水槽	THD-2015	±0.1℃	-20~99℃
差示扫描量热仪	NETZSCH DSC 200F3	—	-180~725℃
傅里叶红外光谱仪	Thermo Scientific Nicolet iS20	—	4000~400cm^-1
真空干燥箱	BZF-30	±0.5℃	RT+2~250℃
扫描电子显微镜	蔡司Gemini300/Nova NanoSEM450	—	—
热导率测定仪	DRE-Ⅲ	≤3%	0.005~50W/(m•K)

样品	蒸馏水/mL	无水乙醇/mL	SDS/g	HCl/mL	n-docosane/g	TBT/g
S1	72.0	36.0	0.5	0.10	5.0	5.0
S2	72.0	36.0	0.5	0.10	5.0	10.0
S3	72.0	36.0	0.5	0.25	5.0	5.0
S4	72.0	36.0	1.0	0.10	5.0	5.0

样品	蒸馏水/mL	无水乙醇/mL	SDS/g	HCl/mL	n-docosane/g	TBT/g
S1	72.0	36.0	0.5	0.10	5.0	5.0
S2	72.0	36.0	0.5	0.10	5.0	10.0
S3	72.0	36.0	0.5	0.25	5.0	5.0
S4	72.0	36.0	1.0	0.10	5.0	5.0

材料	融化温度/℃	融化焓值/J·g^-1	凝固温度/℃	凝固焓值/J·g^-1	融化峰值温度/℃	凝固峰值温度/℃	R/%	E/%	η/%
n-docosane	42.9	251.6	42.7	254.15	45.7	40	—	—	—
TiO₂@n-docosane	41.3	178	42.4	171	44.7	35.4	70.7	69.0	97.6