张浩
, 黄新杰, 宗志芳, 刘秀玉
安徽工业大学建筑工程学院 马鞍山 243032
ZHANG Hao, HUANG Xinjie, ZONG Zhifang, LIU Xiuyu
中图分类号: TU522.1
文章编号: 1005-3093(2016)06-0418-09
通讯作者:
收稿日期: 2015-10-22
网络出版日期: 2016-06-25
版权声明: 2016 《材料研究学报》编辑部 《材料研究学报》编辑部
基金资助:
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摘要
采用硅烷偶联剂, 通过溶胶-凝胶法制备以SiO2为壁材、棕榈醇-棕榈酸-月桂酸为芯材的细粒径SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料。采用等温吸放湿法、步冷曲线法、激光粒度分析仪(LPSA)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)和差示扫描量热(DSC)分析表征了SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的调湿性能、调温性能、粒度分布、组成结构、表面形貌和热性能。结果表明, 去离子水用量、无水乙醇用量、硅烷偶联剂用量和棕榈醇-棕榈酸-月桂酸用量对SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料有重要的影响。当去离子水与正硅酸乙酯的物质的量比为9、无水乙醇与正硅酸乙酯的物质的量比为5、棕榈醇-棕榈酸-月桂酸与正硅酸乙酯的物质的量比为0.5和硅烷偶联剂与正硅酸乙酯的物质的量比为0.1时, SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料呈球形且表面光滑紧凑, 尺寸仅为1680.60~1735.35 nm, 粒径分布均匀, 分散性较好, 具有良好的相变储湿性能。
关键词：
Abstract
Microcapsules of phase change- and humidity-controlling material were synthesized by sol-gel method with hexadecanol-palmitic acid-lauric acid as core, SiO2 as shell and silaneas coupling agent. Then their performance of humidity controlling and temperature controlling, particle size distribution, composition and structure, surface morphology and thermal properties were characterized by isothermal sorption method, cooling curve measurement, laser particle analyzer (LPSA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) respectively. The results show that the amount of deionizedwater, absolute alcohol, hexadecanol-palmitic acid-lauric acid and silane coupling agent had great effect on the properties of the prepared phase change- and humidity-controlling materials. The phase change- and humidity-controlling material of good performance as spherical particles with smooth surface, homogeneous size distribution in a range of 1680.60~1735.35 nm and excellent dispersibility may be synthesized by the following optimal processing parameters: the mole ratio of deionized water totetraethyl orthosilicateis 9, the mole ratio of absolute alcohol totetraethyl orthosilicate 5, the mole ratio of hexadecanol-palmitic acid-lauric acid to tetraethyl orthosilicate 0.5, and the mole ratio of silane coupling agent totetraethyl orthosilicate 0.1.
Keywords：
相变储能材料是利用材料相态变化而发生的储能-放能的特性, 以解决建筑能量供求在时间和空间上不匹配的矛盾, 可以有效提高能源的利用率, 达到控制和减少建筑耗能目的, 正逐渐成为建筑节能领域的新宠[1-3]。近年来, 利用微胶囊技术将有机相变材料包裹于无机材料中制备无机相变微胶囊, 既能有效解决有机相变材料泄漏, 防止相变物质与周围环境反应, 又能提高相变材料使用效率, 增大传热表面积, 已成为目前最具发展潜力的相变储热材料[4-5]。然而, 一方面对于无机相变微胶囊的研究多关注于调温性能[6-11], 极少关注多孔无机材料的网络空隙结构可能具有的调湿性能, 从而导致所研究的无机相变微胶囊只能改善室内环境热舒适度, 而无法改善室内环境湿舒适度, 极大地限制了其在建筑领域的应用; 另一方面对于无机相变微胶囊粒径的研究较少, 无机相变微胶囊的粒径越小, 比表面积越大, 传热传湿性能越好, 从而提高相变调湿性能。因此, 研究细粒径SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料对于利用材料“被动调节能力”改善室内环境舒适度, 降低建筑能耗具有重要意义。
本文通过溶胶-凝胶法[12]制备了以SiO2为壁材[13], 棕榈醇-棕榈酸-月桂酸为芯材[14]的SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料, 分析了去离子水用量、无水乙醇用量、硅烷偶联剂用量和棕榈醇-棕榈酸-月桂酸用量对SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料粒径分布、表面形貌、组成结构和相变调湿性能的影响。
主要原料: 正硅酸乙酯(Si(OC2H5)4, 分析纯, 天津市福晨化学试剂厂); 无水乙醇(CH3CH2OH, 分析纯, 西安三浦化学试剂有限公司); 棕榈醇(C16H34O)、 棕榈酸(C16H32O2)及月桂酸(C12H24O2)均为分析纯(天津市福晨化学试剂厂); 盐酸(HCl)和氨水(NH3H2O)为分析纯(上海山浦化工有限公司); 硅烷偶联剂KH570(CH2=C(CH3)COOCH2CH2CH2Si(OCH3)3, 南京强威化工有限公司); 实验用水均为去离子水。
实验原理: 正硅酸乙酯、无水乙醇和去离子水的体系在超声场的分散作用下充分接触传质, 使正硅酸乙酯的水解反应顺利进行。然后正硅酸乙酯、无水乙醇、去离子水和硅烷偶联剂的体系在酸的催化下, 导致Si-O-Si基团断裂, 同时SiO2表面的物理吸附水和硅羟基被硅烷偶联剂的有机部分所代替, 形成Si-OH基团为主、交联度较低的均匀改性SiO2溶胶态。之后加入到改性SiO2溶胶的棕榈醇-棕榈酸-月桂酸在超声的强化传质分散作用下, 可以有效地分散形成均匀液滴, 同时Si-OH基团吸附在棕榈醇-棕榈酸-月桂酸液滴表面。最后改性SiO2溶胶体在超声和适合温度下, 吸附在棕榈醇-棕榈酸-月桂酸液滴表面的Si-OH基团断裂重新形成Si-O-Si基团, 将棕榈醇-棕榈酸-月桂酸液滴包裹, 形成SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料。
制备工艺: 将棕榈醇、棕榈酸和月桂酸按质量分数比(30%:20%:50%)混合并称量放入烧杯中, 在60℃水浴条件下溶解并且以中速搅拌2 h使其分散均匀, 得到棕榈醇-棕榈酸-月桂酸。按表1所列单体组成将正硅酸乙酯、无水乙醇、去离子水和硅烷偶联剂依次称量加入烧杯中, 用恒温磁力搅拌器在中速、60℃水浴条件下搅拌10 min, 将得到的混合液放入超声波细胞破碎仪中, 以100 W的功率分散15 min, 用盐酸和氨水调整混合液到pH=3后继续放到超声波细胞破碎仪中, 以100 W的功率分散15 min后取出, 得到改性SiO2溶胶。按表1所列单体组成将棕榈醇-棕榈酸-月桂酸加入到改性SiO2溶胶中用恒温磁力搅拌器在高速、60℃水浴条件下搅拌15 min后, 再一次以100 W的功率超声分散45 min使棕榈醇-棕榈酸-月桂酸均匀的分散, 使其嵌入到改性SiO2载体中, 将得到的水溶胶放到60℃恒温水浴锅中陈化2 h得到凝胶, 再将凝胶放在干燥箱中80℃烘干8 h得到SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料。
表1 SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的配方
Table 1 Formulations of SiO2 based hexadecanol-palmitic acid-lauric acid microencapsulated phase change and humidity controlling materials
| Sample | Mole ratio between deionizedwater and tetraethyl orthosilicate | Mole ratio between absolute alcohol and tetraethyl orthosilicate | Mole ratio between hexadecanol-palmitic acid-lauric acid and tetraethyl orthosilicate | Mole ratio between silane coupling agent and tetraethyl orthosilicate |
|---|---|---|---|---|
| 1 | 7 | 5 | 0.5 | 0.10 |
| 2 | 9 | 5 | 0.5 | 0.10 |
| 3 | 11 | 5 | 0.5 | 0.10 |
| 4 | 9 | 3 | 0.5 | 0.10 |
| 5 | 9 | 7 | 0.5 | 0.10 |
| 6 | 9 | 5 | 0.5 | 0.00 |
| 7 | 9 | 5 | 0.5 | 0.05 |
| 8 | 9 | 5 | 0.5 | 0.15 |
| 9 | 9 | 5 | 0.2 | 0.10 |
| 10 | 9 | 5 | 0.8 | 0.10 |
性能测试: SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的储湿调湿性能采用等温吸放湿法[15]进行测试, 其相对湿度变化范围为32.78%、43.16%、52.89%、64.92%、75.29%、84.34%和97.30%, 以各相对湿度下试样平衡含湿量u(g/g)表示试样储湿调湿性能的强弱。SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的相变调温性能采用步冷曲线法[16]进行测试, 其温度变化范围为35~20℃, 以降温过程中试样所需时间t(s)表示试样相变调温性能的强弱。
试样的表征: SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的形貌分析采用日本电子株式会社JSM-6510LV 型扫描电子显微镜, 将试样固定在样品台上, 在其表面喷金后进行测试, 分辨率1 nm。SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的结构分析采用德国BRUKER光谱仪器公司BRUKER UECIOR22 型傅立叶变换红外光谱仪, 将试样溶于分散液中超声分散, 设定折射率为1.421进行测试。SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的相变温度和相变焓采用美国TA仪器公司TA2910 型差示扫描量热仪, 将试样放置于载物台上, 设定升/降温速率为5℃/min, 气氛为N2, 进气速率为50 mL/min。
图1为不同去离子水用量的SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料(样品1、2和3)粒径分布图。其中d10表示累积分布10%所对应的直径值; d50表示累积分布50%所对应的直径值,又称“中位粒径”; d90表示累积分布90%所对应的直径值。可见, 当去离子水用量较小时(图1A), 溶胶粘度较大, 导致正硅酸乙酯水解不完全, 局部出现不均匀凝聚, 从而造成所制备的SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料粒径分布较宽, 即d10=758.31 nm、d90=4895.80 nm。当去离子水用量较大时(图1C), 溶胶的含水量和溶质水化度增加, 造成溶胶的黏度和缩聚物浓度减小, 导致SiO2凝胶对棕榈醇-棕榈酸-月桂酸的包裹与束缚能力下降, 相变材料泄露后出现团聚, 使SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料粒径变大, 即d50=2241.53 nm。当去离子水用量适当时(图1B), 溶胶粘度合理且正硅酸乙酯水解完全, 导致颗粒出现凝聚几率小, 使得SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料粒径较小, 粒径分布较窄, 即d10=1232.20 nm、d50=1735.35 nm、d90=2468.32 nm, 说明合适的去离子水用量提高了SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的尺寸均一性。
图1 样品1(A), 样品2(B)和样品3(C)的LPSA图
Fig.1 LPSA images of sample 1 (A), sample 2 (B) and sample 3 (C)
图2为不同无水乙醇用量的SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料(样品4、2和5)粒径分布图。可见, 当无水乙醇用量较小时(图2A), 由于无水乙醇自身的挥发性, 导致溶胶的凝胶时间较短, 极易引起溶胶中粒子的聚集和沉淀, 使SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料粒径变大, 即d50=2090.24 nm。当无水乙醇用量较大时(图2C), 有利于正硅酸乙酯水解反应向逆反应方向进行, 导致正硅酸乙酯水解不完全, 凝聚形成的颗粒大量包裹无水乙醇, 使SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料粒径变大, 即d50=2443.04 nm。当无水乙醇用量适当时(图2B), 无水乙醇不仅能减缓正硅酸乙酯水解速度, 而且稀释溶液浓度, 以达到减少水解产生的聚合物在无水乙醇中的碰撞几率, 有效控制颗粒团聚, 增强溶胶的稳定性, 使SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料粒径较小, 粒径分布较窄, 即d10=1216.58 nm、d50=1680.60 nm、d90=2374.68 nm, 与图1B测试结果基本一致。
图2 样品4(A), 样品2(B)和样品5(C)的LPSA图
Fig.2 LPSA images of sample 4 (A), sample 2 (B) and sample 5 (C)
图3为不同硅烷偶联剂用量的SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料(样品6、7、2和8)形貌图。可见, 当未加硅烷偶联剂时(图3A), SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料团聚体尺寸较大, 即2700.00~3100.00 nm, 并且有大块的堆积现象, 这是因为未改性SiO2表面与水分子作用而带有的羟基(-OH), 会以化学键或者氢键相结合, 极易团聚[17]。当硅烷偶联剂用量较小时(图3B), 由于硅烷偶联剂的添加, SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料粒径明显减小, 即1700.00~2000.00 nm, 粒径分布趋向均匀, 但是团聚现象依然明显。当硅烷偶联剂用量适当时(图3C), SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料呈球形且表面光滑紧凑, 颗粒保持较小粒径尺寸, 即1650.00~1750.00 nm, 粒径分布更加趋向均匀, 整体分散性较好, 这是因为硅烷偶联剂为疏水改性剂, 在强力分散条件下SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料表面形成强界面膜, 有效阻止液滴合一, 形成均匀、分散的细小粒径颗粒。当硅烷偶联剂用量较大时(图3D), SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料粒径存在变大的趋势, 即2200.00~2500.00 nm, 这是因为过量的硅烷偶联剂起到架桥作用, 使颗粒之间产生团聚。
图3 样品6(A), 样品7(B), 样品2(C)和样品8(D)的形貌SEM像
Fig.3 SEM images of sample 6 (A), sample 7 (B), sample 2 (C) and sample 8 (D)
图4为改性SiO2、棕榈醇-棕榈酸-月桂酸与不同棕榈醇-棕榈酸-月桂酸用量的SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料(样品9、2和10)红外光谱。可见, 改性SiO2红外光谱(图4A)在1056.47 cm-1、792.75cm-1和933.75 cm-1处分别出现环状Si-O-Si的反对称伸缩振动吸收峰、Si-O-Si的对称伸缩振动吸收峰和Si-OH的弯曲振动吸收峰, 同时在2925.21 cm-1处出现烷基强的-CH2反对称伸缩振动吸收峰, 说明改性SiO2表面存在有机物, 有利于提高改性SiO2在有机介质—无水乙醇中的分散稳定性。棕榈醇-棕榈酸-月桂酸红外光谱(图4B)在2917.05 cm-1、2849.35 cm-1、1464.88 cm-1、939.35 cm-1和1706.44 cm-1处分别出现-CH3与-CH2的反对称伸缩振动引起的C-H键伸缩振动峰、-CH3与-CH2的对称伸缩振动引起的C-H键伸缩振动峰、-OH面内弯曲振动吸收峰、-OH面外弯曲振动吸收峰和C=O伸缩振动吸收峰, 说明棕榈醇-棕榈酸-月桂酸主要以羧酸聚体的形式存在。在不同棕榈醇-棕榈酸-月桂酸用量的SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料红外光谱(图4C~E)中都存在改性SiO2和棕榈醇-棕榈酸-月桂酸的特征峰且未出现新的特征峰, 表明改性SiO2与棕榈醇-棕榈酸-月桂酸之间未发生化学反应, 仅是物理嵌合。同时对比于图4A~B, 改性SiO2的特征峰强度明显增强, 而棕榈醇-棕榈酸-月桂酸的特征峰强度明显减弱。这是因为改性SiO2包裹棕榈醇-棕榈酸-月桂酸, 导致改性SiO2分子振动时偶极矩变化增大, 其特征峰强度增强; 而棕榈醇-棕榈酸-月桂酸被改性SiO2包裹, 由于存在界面阻隔效果, 其特征峰强度减弱。
图4 改性SiO2(A), 棕榈醇-棕榈酸-月桂酸(B), 样品9(C), 样品2(D)和样品10(E)的FT-IR图
Fig.4 FT-IR images of modified SiO2 (A), hexadecanol-palmitic acid-lauric acid (B), sample 9 (C), sample 2 (D) and sample 10 (E)
进一步分析图4C~E可见, 当棕榈醇-棕榈酸-月桂酸用量较小时(图4C), 改性SiO2特征峰的强度较强, 说明棕榈醇-棕榈酸-月桂酸用量未超出改性SiO2的包裹能力; 当棕榈醇-棕榈酸-月桂酸用量较大时(图4E), 棕榈醇-棕榈酸-月桂酸特征峰的强度较强, 说明棕榈醇-棕榈酸-月桂酸用量超出改性SiO2的包裹能力, 并有可能在SiO2表面出现棕榈醇-棕榈酸-月桂酸堆积的现象; 当棕榈醇-棕榈酸-月桂酸用量适当时(图4D), SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料保持较好的壳核比, 有利于改性SiO2对棕榈醇-棕榈酸-月桂酸的包裹, 而且有利于提高SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的相变调湿综合性能。
图5为不同棕榈醇-棕榈酸-月桂酸用量的SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料(样品9、2、10和6)平衡含湿量。图6为不同棕榈醇-棕榈酸-月桂酸用量的SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料(样品9、2、10和6)步冷曲线。其中从图5A~C和(图6a~c)可见, 随着SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料中棕榈醇-棕榈酸-月桂酸用量的增加, 试样的储湿调湿性能降低, 即相对湿度32.78~97.30%的平衡含湿量从0.1145~0.2769 g/g降至0.0610~0.1462 g/g, 试样的相变调温性能上升, 即温度35~20℃的降温时间从725 s升至1570 s, 试样的储湿调湿性能与相变调温性能呈现此消彼长的趋势, 说明SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料中SiO2属于储湿调湿基元, 棕榈醇-棕榈酸-月桂酸是相变调温基元。其中从图5B、D和图6b、d可见, 加入适当用量的硅烷偶联剂能大幅提高SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的相变调湿性能, 即相对湿度32.78%~97.30%的平衡含湿量从0.0714~0.1763 g/g升至0.0895~0.2150 g/g, 温度35~20℃的降温时间从1240 s升至1345 s。这是因为硅烷偶联剂的加入, 使SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的粒径减少, 比表面积增加, 分散性改善, 一方面有利于增大储湿调湿基元与空气中水分的接触面积, 另一方面有利于提高相变调温基元与空气热交换的作用面积。同时也说明虽然作为疏水改性剂的硅烷偶联剂降低了SiO2表面亲水官能团的吸湿性能, 但是SiO2具有的丰富孔结构是表现储湿调湿性能的主要动力。
图5 样品9(A), 样品2(B), 样品10(C)和样品6(D)的平衡含湿量
Fig.5 Equilibrium moisture content of sample 9 (A), sample 2 (B), sample 10 (C) and sample 6 (D)
图6 各试样的步冷曲线
Fig.6 Cooling curves (a. sample 9, b. sample 2, c. sample 10, d. sample 6)
表2为不同棕榈醇-棕榈酸-月桂酸用量的SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料(样品9、2、10和6)热性质, 同时根据纯棕榈醇-棕榈酸-月桂酸的相变焓, 可以计算出SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料中棕榈醇-棕榈酸-月桂酸的含量。可见, 随着棕榈醇-棕榈酸-月桂酸用量的增加(样品9、2和10), SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料相变焓增加, 而相变温度变化较小, 基本保持不变, 即21.54~27.75℃, 说明棕榈醇-棕榈酸-月桂酸均匀性好, 热性能稳定。硅烷偶联剂的加入(样品2和6), 对SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料相变温度影响极小, 即21.89~27.75℃变为与21.54~27.24℃, 说明所加入的硅烷偶联剂不会影响相变调温基元的相变温度; 对SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料相变焓影响较大, 即92.03~97.96 J/g变为86.78~90.45 J/g, 说明所加入的硅烷偶联剂使胶囊具有较小的粒径和较好的均匀性能提高相变调温基元利用率。
表2 SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的热性能
Table 2 Thermal properties of SiO2 based hexadecanol-palmitic acid-lauric acid microencapsulated phase change and humidity controlling materials
| Sample | Phase change temperature (℃) | Phase transition enthalpy (J/g) | hexadecanol-palmitic acid-lauric acid content (%) |
|---|---|---|---|
| Pure hexadecanol-palmitic acid-lauric acid | 22.79~28.18 | 173.36~178.72 | 100 |
| 2 | 21.89~27.75 | 92.03~97.96 | 53.1~54.8 |
| 6 | 21.54~27.24 | 86.78~90.45 | 50.1~50.6 |
| 9 | 22.13~27.58 | 30.62~32.28 | 17.7~18.1 |
| 10 | 22.27~28.06 | 141.46~150.33 | 81.6~84.1 |
将SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料(样品2)在相对湿度32.78~97.30%和温度20~35℃中进行循环500次, 结果示于表3和图7。由表3和图7可见, 经历500次循环, SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的储湿调湿性能和相变调温性能下降较少, 低于10%, 说明SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的储湿调湿基元SiO2能有效包覆相变调温基元棕榈醇-棕榈酸-月桂酸, 在其调节温度和相对湿度过程中有较好的相变调湿循环稳定性。
表3 样品2的平衡含湿量
Table3 Equilibrium moisture content of sample 2
| Relativehumidity (%) | Equilibrium moisture content (g/g) | Descent rate (%) | |||||
|---|---|---|---|---|---|---|---|
| Without cycling | After 500 cycling | ||||||
| Adsorbing moisture process | Desorption moisture process | Adsorbing moisture process | Desorption moisture process | Adsorbing moisture process | Desorption moisture process | ||
| 32.78 | 0.0895 | 0.0993 | 0.0813 | 0.0898 | 9.16 | 9.57 | |
| 43.16 | 0.1100 | 0.1225 | 0.1020 | 0.1182 | 7.27 | 3.51 | |
| 52.89 | 0.1203 | 0.1345 | 0.1089 | 0.1251 | 9.48 | 6.99 | |
| 64.92 | 0.1296 | 0.1424 | 0.1174 | 0.1316 | 9.41 | 7.58 | |
| 75.29 | 0.1486 | 0.1586 | 0.1347 | 0.1474 | 9.35 | 7.06 | |
| 84.34 | 0.1769 | 0.1830 | 0.1621 | 0.1697 | 8.37 | 7.27 | |
| 97.30 | 0.2145 | 0.2150 | 0.1990 | 0.2035 | 7.23 | 5.35 | |
1. 去离子水用量与无水乙醇用量对SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的粒径分布有重要影响, 当离子水用量与无水乙醇用量适当时, 能减小胶囊凝聚几率和碰撞几率, 有效控制颗粒团聚, 增强溶胶的稳定性。硅烷偶联剂用量对SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的表面形貌有影响, 当硅烷偶联剂用量适当时, 能使胶囊粒径分布更加趋向均匀, 分散性较好, 提高相变调温基元利用率。棕榈醇-棕榈酸-月桂酸用量对SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料的组成结构有一定影响, 当棕榈醇-棕榈酸-月桂酸用量适当时, 能使胶囊保持较好的壳核比, 不仅有利于改性SiO2对棕榈醇-棕榈酸-月桂酸的包裹, 而且有利于提高胶囊的相变调湿综合性能。
2. 当去离子水与正硅酸乙酯的物质的量比为9、无水乙醇与正硅酸乙酯的物质的量比为5、棕榈醇-棕榈酸-月桂酸与正硅酸乙酯的物质的量比为0.5和硅烷偶联剂与正硅酸乙酯的物质的量比为0.1时, SiO2基棕榈醇-棕榈酸-月桂酸微胶囊相变调湿材料呈球形且表面光滑紧凑, 粒径较小(d50=1680.60~1735.35 nm), 粒径分布均匀, 分散性较好; 相变温度21.89~27.75℃适用于建筑领域, 相变焓88.03~91.96 J/g; 在人体舒适相对湿度范围(40~60%), 平衡含湿量为0.1100~0.1424 g/g; 并且在经历500次循环后, 相变储湿性能下降低于10%, 具有较好的相变储湿稳定性。
The authors have declared that no competing interests exist.
| [1] |
Review on thermal energy storage with phase change materials and applications ,
<h2 class="secHeading" id="section_abstract">Abstract</h2><p id="">The use of a latent heat storage system using phase change materials (PCMs) is an effective way of storing thermal energy and has the advantages of high-energy storage density and the isothermal nature of the storage process. PCMs have been widely used in latent heat thermal-storage systems for heat pumps, solar engineering, and spacecraft thermal control applications. The uses of PCMs for heating and cooling applications for buildings have been investigated within the past decade. There are large numbers of PCMs that melt and solidify at a wide range of temperatures, making them attractive in a number of applications. This paper also summarizes the investigation and analysis of the available thermal energy storage systems incorporating PCMs for use in different applications.</p>
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The utilization of micro- encapsulated phase change material wallboards for energy saving ,
Wallboards with micro encapsulated phase changing material (micro PCM) were used to investigate the performance and the energy saving characteristics as building materials in winter and summer climate conditions. The test house consisted of a boiler with under floor heating system, an air conditioner, micro PCM wallboard room and conventional wallboard room. The outer temperature of the rooms could be artificially controlled at the temperature range of -12 to 35 degrees C. Micro PCM content in wallboards was 0-4 kg/m(2). The melting temperature and latent heat of Micro PCM are 23 degrees C and 211 J/g. Also, micro PCM shows stable mechanical strength under 500 psi. As micro PCM content increased, the temperature fluctuations decreased. In case of micro PCM wallboard, temperature profiles in the room show stable and comfortable ranges. The optimum amount of micro PCM in wallboard to maximize energy saving efficiency was around 3 kg/m(2).
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New approach for sol-gel synthesis of microencapsulated n-octadecane phase change material with silica wall using sodium silicate precursor , |
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Fabrication and properties of microencapsulated paraffin@SiO2 phase change composite for thermal energy storage ,
In this work, a novel microencapsulated phase change composite of paraffin@SiOwas prepared by in situ emulsion interfacial hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS). The as-prepared paraffin@SiOcomposite was determined by Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD), scanning electronic microscope (SEM), and transmission electron microscopy (TEM), respectively. The results showed that the paraffin@SiOcomposite is composed of quasi-spherical particles with diameters of 200–500 nm. The paraffin is encapsulated in a SiOshell, and there is no chemical reaction between them. The DSC results indicate that the melting temperature and latent heat of the composite are 56.5 °C and 45.5 J/g, respectively. The encapsulation ratio of paraffin was calculated to be 31.7% from the results of the DSC measurements, slightly lower than the loading content (32.5%) of paraffin in the microencapsulated composite from the TGA measurements. The as-prepared paraffin@SiOcomposite could maintain its phase transition perfectly after 30 melting–freezing cycles, and no leakage of paraffin was observed at 70 °C for 20 min. Moreover, the high heat storage capability and good thermal stability of the composite enable it to be a potential material to store thermal energy in practical applications.
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Fabrication and characterization of nanocapsules containing n-dodecanol by miniemulsion polymerization using interfacial redox initiation , |
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Brouwers, M. Founti, The behavior of self-compacting concrete containing micro-encapsulated phase change materials , |
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Synthesis and properties of microencapsulated paraffin composites with SiO2 shell as thermal energy storage materials ,
Microencapsulated paraffin composites with SiO 2 shell as thermal energy storage materials were prepared using sol鈥揼el methods. In the microencapsulated composites, paraffin was used as the core material that is a phase change material (PCM), and SiO 2 acted as the shell material that is fire resistant. Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD) and scanning electronic microscope (SEM) were used to determine chemical structure, crystalloid phase and microstructure of microencapsulated paraffin composites with SiO 2 shell, respectively. The thermal properties were investigated by a differential scanning calorimeter (DSC). The thermal stability was determined by a thermogravimetric analyzer (TGA). The SEM results showed that the paraffin was well encapsulated in the shell of SiO 2 . The DSC results indicated that the microencapsulated paraffin composites solidify at 58.27掳C with a latent heat of 107.05kJ/kg and melt at 58.37掳C with a latent heat of 165.68kJ/kg when the encapsulation ratio of the paraffin is 87.5%. The TGA results showed that the SiO 2 shells can improve the thermal stability of the microencapsulated paraffin composites due to the synergistic effect between the paraffin and SiO 2 .
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| [8] |
Preparation and thermal properties of fatty acid/inorganic nano-particle form-stable phase change material ,
脂肪酸/无机纳米颗粒基定形相变材料的制备与热性能 ,
以工业水玻璃为纳米SiO2前驱物,以癸酸(CA)和月桂酸(LA)二元低共熔酸为相变芯材,在表面活性剂的参与下,采用溶胶-凝胶法一步制备出纳米级复合定形相变蓄热材料.利用透射电子显微镜,扫描电子显微镜,傅里叶红外光谱仪,方差扫描量热法和热重分析等测试技术对此定形相变蓄热材料的结构和性能进行分析,并采用瞬态热线法测量了其导热系数.结果表明:相变芯材在吸热熔化后不会产生流动和渗漏;复合相变材料中脂肪酸含量(质量分数)为46%,具有良好的相变蓄热性能(相变温度19.57℃,相变潜热71.28J/g)和热稳定性;复合相变材料导热系数为0.178W/(m.K),可作为一种良好的隔热、保温建筑材料.
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| [9] |
Preparation and thermal performance tests of microencapsulated gypsum-based phase change building material ,微胶囊相变储能石膏基建筑材料制备及性能研究 , |
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Improvement of the thermal behaviour of gypsum blocks by the incorporation of microcapsules containing PCMS obtained by suspension polymerization with an optimal core/coating mass ratio ,
<h2 class="secHeading" id="section_abstract">Abstract</h2><p id="">The feasibility of incorporating microcapsules containing Phase Change Materials (PCMs), previously obtained by a suspension polymerization process, in gypsum wallboards to increase the wall energy storage capacity was studied. Firstly, the energy storage capacity of the resulting microcapsules and the microencapsulation efficiency was maximized by studying the influence of the synthesis variable core/coating mass ratio on the suspension polymerization process. Results indicate that the higher paraffin wax to styrene monomer mass ratio, the lower microencapsulation efficiency. A mass ratio of Rubitherm® RT27 to styrene monomer equal 1.5 allowed to obtain microcapsules with the highest energy storage capacity and a good microencapsulation efficiency. It was also observed that the energy storage capacity is dependent on the particle size; the maximum capacity was obtained for a particle size of 500 μm. Finally, the thermal behaviour of three gypsum wallboards one without PCMs and the others doped with 4.7% and 7.5% by weight of microcapsules containing Rubitherm® RT27 at the optimal core/coating mass ratio was studied. Results showed that the higher the amount of microcapsules containing PCMs incorporated to the gypsum wallboard, the lower or higher the external wall temperature for heating or cooling process, respectively. Besides, the incorporation of the microcapsules to the wall increased the time required to achieve the final steady state, verifying that the material insulation capacity was enhanced by increasing PCMs content in the wall.</p>
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| [11] |
Prepared of PAR/POL/SOD-composite-wall microencapsulated and research of energy storage and humidity-control performance ,PAR/POL/SOD复合微胶囊的制备及热湿性能研究 ,
以相变石蜡为核、高吸油性树脂聚丙烯酸酯为内壳,采用原位聚合法制备相变调温微胶囊,在内壳 形成后,采用界面聚合法合成以高吸水性树脂聚丙烯酸钠为外壳的复合微胶囊,通过差示扫描法、吸放湿平衡曲线法对复合微胶囊调温、调湿性能进行测试;利用扫 描电镜、红外光谱分析仪对复合微胶囊的形貌、结构进行分析。结果表明,双壳复合微胶囊兼有良好的调温调湿性,可作为温湿调节剂配制调温调湿建筑材料。
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| [12] |
Study on degradation effect of Ce-TiO2photocatalyst coating on formaldehyde solution and its prediction model ,Ce-TiO2光催化涂料降解甲醛溶液的性能研究及预测模型 ,
通过自制Ce-TiO2光催化 涂料,利用X射线衍射、激光粒度分析和扫描电镜表征Ce-TiO2光催化颗粒的微晶尺寸和晶体结构,进行了光催化涂料耐水性实验和光催化涂料降解甲醛实 验,创建了BP模型函数,建立了Ce-TiO2光催化涂料降解甲醛溶液的预测模型。结果表明,采用彻底除去负离子和温和的热处理方式能显著降低Ce- TiO2颗粒团聚,Ce-TiO2一次颗粒平均粒度在0~1μm范围内,并且呈现正态分布。Ce-TiO2光催化涂料的耐水性能和光催化性能优良,经过 1020 min后,降解甲醛溶液效率高达80.7%。Ce-TiO2光催化涂料的预测模型的预测值和实测浓度吻合较好,平均绝对误差为 -0.00028μg/mL,平均相对误差为-0.202%。
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| [13] |
XIONG lei, MA Xianglong, Preparation and texture of phase change materials of fatty acid/SiO2 composite ,脂肪酸/SiO2复合相变材料的制备及其对织构的影响因素 ,
以SiO<sub>2</sub>为载体材料、以脂肪酸为相变材料、以无水酒精和去离子水为溶剂, 用溶胶-凝胶法制备脂肪酸/SiO<sub>2</sub>复合相变材料, 用SEM、LPSA、FT-IR、DSC等手段对其表征, 研究了芯材种类、相变材料用量、无水酒精用量、去离子水用量、溶液pH值、超声波功率等因素对脂肪酸/SiO<sub>2</sub>复合相变材料织构的影响。结果表明, 脂肪酸/SiO<sub>2</sub>复合相变材料织构受到芯材种类、相变材料用量、无水酒精用量和去离子水用量的影响较大, 也与溶液pH值和超声波功率有关。其最佳工艺参数为: 癸酸-棕榈酸为芯材、癸酸-棕榈酸与正硅酸乙酯的物质的量比为0.4、无水酒精与正硅酸乙酯的物质的量比为5、去离子水与正硅酸乙酯的物质的量比为9、溶液pH值4和超声波功率为200 W。
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| [14] |
Optimization for preparation of phase change and humidity control composite materials of hexadecanol-palmitic acid-lauric acid/SiO2 ,优化制备棕榈醇-棕榈酸-月桂酸/SiO2复合相变调湿材料 ,
以SiO<sub>2</sub>为载体材料、以棕榈醇-棕榈酸-月桂酸为相变材料制备棕榈醇-棕榈酸-月桂酸/SiO<sub>2</sub>复合相变调湿材料, 基于均匀设计和多元非线性回归法研究了各因素对复合相变调湿材料调湿性能和控温性能的影响。结果表明, 各因素对性能影响大小的排序为: 无水乙醇与正硅酸乙酯的物质的量比、溶液pH值、棕榈醇-棕榈酸-月桂酸与正硅酸乙酯的物质的量比、超声波功率、去离子水与正硅酸乙酯的物质的量比; 优化制备方案为: 溶液的pH值为2.68、超声波功率为113 W、去离子水与正硅酸乙酯的物质的量比为9.03、无水乙醇与正硅酸乙酯的物质的量比为5.22、棕榈醇-棕榈酸-月桂酸与正硅酸乙酯的物质的量比为0.51。
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| [15] |
Humidity-control materials and their humidity absorption and desorpttion rate variation ,建筑调湿材料吸放湿速度变化规律 ,
实验测得了4种建筑材料样品在 不同相对湿度条件下的平衡含湿量.将4种样品置于环境参数不同的恒温恒湿环境中进行12h吸湿12h放湿的吸放湿周期试验,测得了样品在各个环境条件下吸 (放)湿过程中每小时的吸(放)湿量.实验结果表明,在样品所处环境相对湿度相同时,各实验样品的量纲为一的吸放湿速度是时间的同一幂函数.数值拟合得到 了环境相对湿度分别为95%和75%时样品的量纲为一的吸放湿速度的表达式.给出了样品在恒温恒湿环境(风速在2.0m·s-1以下)中材料每小时吸放湿 量计算值的相对误差.
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| [16] |
Study on the ternary phase change system of H/PA/LA ,十六醇/十六酸/十二酸三元复合相变体系研究 ,
采用步冷曲线法测定了不同质量比的十六醇(H)/十六酸(PA) 二元体系的相变温度,绘制了该体系的t-x相图；在其最低共熔点附近引入十二酸(LA)组成三元体系,同样测定了该三元体系在不同质量比下的相变温度,得 到了其t-x相图.采用差示扫描量热仪(DSC)和傅里叶变换红外光谱(FTIR)对上述二元和三元体系中低共熔物的热性能和稳定性进行表征.结果表明: 不同质量比的H-PA二元体系均能形成共熔物,H与PA的质量比分别为6:4和7:3时引入LA的三元体系能形成最低共熔物；H,PA,LA这三者的质量 分数之比分别为30:20:50和35:15:50的三元体系,其相变焓和相变温度分别为179.63,177.87 J/g及26.5,27.0℃,连续相变过程无分层现象,1200次热循环后热稳定性好.
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| [17] |
Thermal energy storage in porous materials with adsorption and desorption of moisture ,
Sensible and latent heat that is stored in materials cannot be typically used over long periods, such as seasons, due to heat losses. Storing thermal energy in the form of chemical potential circumvents this issue. We present a numerical model capable of simulating adsorption/desorption based energy release/storage processes for given input material properties, operating conditions and geometric configurations. Since an analysis of flow in porous media can involve a multitude of empirical constants, making the design tool less general, our approach is more fundamental. The model is based on the species transport equation to characterize the adsorption and desorption in a porous solid and is validated against an experimental study. Without requiring microscopic details of pore structure, it provides the spatial and temporal variations in moisture concentration and temperature during the adsorption and desorption processes in the porous material. Through parametric variations of input conditions, the proposed model/tool can be used to identify adsorbent鈥揳dsorbate pairs for optimal performance.
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