共查询到19条相似文献,搜索用时 93 毫秒
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通过傅里叶变换近红外(FT-NIR)光谱分析技术, 探索聚甲基丙烯酸甲酯-二氧化硅@相变材料(PMMA-SiO2@PCM)微胶囊相变过程的光谱学特性和相变机理, 分析相变过程微胶囊的微结构变化特性. 结果显示: 微胶囊中, 石蜡的融化过程就是-CH2对称伸缩振动逐渐增强和非对称伸缩无规则振动共存的振动变化过程. 石蜡相变过程中, 其近红外吸收峰强度的变化仅是壳层材料吸收峰强度变化幅度的一半. 同时, 近红外光谱可以用来辅助分析微胶囊的核壳结构, 实现微胶囊相变过程监测. 近红外光谱在微胶囊相变材料相变过程的应用对相变机理的研究及高效相变材料的选择具有重要的科学意义和应用价值. 相似文献
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有机烷烃相变材料及其微胶囊化 总被引:2,自引:0,他引:2
本文详细阐述了近年来有机烷烃相变材料(PCMs)及其微胶囊化的研究进展和应用前景。单一组分的有机烷烃PCMs一般均具有理想的相变性质,但由于相变点固定使其应用受到限制,为了满足实际需要,通过不同组分的复配,可以实现对相变温度范围的调节。单一组分直链烷烃PCMs的价格往往很高,石蜡由于含有不同碳原子数的有机烷烃而常被用作PCMs。另一方面,由于有机烷烃PCMs发生固-液相变时,通常会伴有体积膨胀等问题而带来不便。微胶囊化可以将PCMs转化为固体粉末,并通过增加比表面积来提高传热效率,在传热、储能和控温等方面具有广泛的应用价值。本文重点介绍了PCMs微胶囊化的三种化学方法,即原位聚合、界面聚合和悬浮聚合,并与喷雾干燥、相分离和溶胶-凝胶等方法进行了比较。 相似文献
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一种致密的相变储能微胶囊的制备与表征 总被引:1,自引:0,他引:1
制备了以聚脲为第一壁材、苯乙烯-二乙烯苯为第二壁材,以相变点在16℃左右的石蜡为芯材的相变储能微胶囊。采用红外光谱、差示扫描量热分析、热重分析测试技术表征了制备的相变储能微胶囊的结构组成以及热性能;采用溶剂淋洗法研究了影响包覆率的因素。结果表明,相变储热微胶囊是复合相变材料,微胶囊的热稳定性好,致密性优良;通过对水油比、乳化剂及苯乙烯-二乙烯苯用量等各因素对微胶囊包覆率影响的讨论,得出在水与油质量比3.2,乳化剂相对于水的质量分数为2%时,加入苯乙烯与二乙烯苯质量比为10∶1混合液的质量分数为6.0%时,其包覆率达81.14%;制备的微胶囊能耐较高温度,在150℃以下无质量损失,且微胶囊储热能力高达80J/g。同时发现,储热能力与芯壁比有关,比值越大储热潜能越高。 相似文献
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细粒径石蜡微胶囊相变材料的制备与性能 总被引:3,自引:0,他引:3
采用阳离子和非离子复配乳化剂,通过原位聚合制备以丙烯酸酯为壁材,石蜡为芯材的细粒径微胶囊相变材料.采用傅里叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)、差示扫描量热(DSC)、热重(TG)及激光粒度仪分析表征了微胶囊相变材料的化学结构、表面形貌和热性能.结果表明,乳化剂的种类和壁材单体的配比对微胶囊性能有重要的影响.当采用阳离子和非离子复配乳化剂,壁材中单体甲基丙烯酸甲酯(MMA)与丙烯酸(AA)的质量比为9∶1时,微胶囊相变材料呈球形且表面光滑紧凑,尺寸仅为0.2~0.35μm,具有良好的储热能力,相变潜热高达169 J/g;微胶囊中壁材对石蜡芯材的分解具有明显热阻滞作用,分解温度比纯石蜡提高了150℃. 相似文献
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以硬脂酸为芯材, 碳酸钙为壁材, 采用原位聚合法制备了微胶囊型相变材料; 通过扫描电子显微镜、 红外光谱及差热-热重分析对其表面形貌和热性质进行了表征; 通过改变乳化剂的种类及用量, 研究了乳化工艺对微胶囊型相变材料表面形貌、 相变温度和包覆率的影响. 实验结果表明, 在选用的3种乳化剂十二烷基苯磺酸钠、 十六烷基三甲基溴化铵和曲拉通X-100中, 十二烷基苯磺酸钠相对效果最好, 乳化剂与芯材最佳质量比为0.5%, 相变温度为112.24 ℃时, 封装率达到92.1%. 相似文献
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以石蜡为芯材,甲基丙烯酸甲酯-丙烯酸共聚物为壁材,纳米SiO2为改性剂,采用原位聚合法制备了石蜡微胶囊相变储能材料,系统研究了添加纳米SiO2对石蜡微胶囊相变材料性能的影响;采用傅里叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)、示差扫描量热法(DSC)和热重分析(TGA)等对石蜡微胶囊相变材料的化学结构、表面形貌和热性能进行了表征.研究表明,纳米SiO2能够有效提高微胶囊壁材的热稳定性,当丙烯酸酯壁材中添加3%改性纳米SiO2时,微胶囊呈球形且表面光滑,尺寸250 ~ 300 nm,具有良好的储热能力,相变潜热高达134.79 J/g,分解温度比未添加改性纳米SiO2的石蜡微胶囊提高了40 K,经过1000次热循环测试,石蜡渗漏率仅2.96%. 相似文献
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蓄热调温石蜡相变微胶囊的制备及性能 总被引:2,自引:0,他引:2
采用界面聚合法,以甲苯2,4-二异氰酸酯和哌嗪为反应单体、30号相变石蜡为芯材,制得了一种智能纺织品用蓄热调温相变微胶囊。通过红外光谱、扫描电镜、差示扫描量热仪对微胶囊的化学组成、形貌和蓄热性能进行了表征,测试了其耐热和耐溶剂性。结果表明:所得微胶囊主要为球形,表面光滑,平均粒径为10.6μm,对w=0.40的NaOH溶液、w=0.60的H2SO4溶液、无水乙醇、丙酮稳定,能被甲苯、二甲基甲酰胺、乙醚破坏。相变潜热为118 J/g,石蜡在微胶囊中的质量分数为84%。 相似文献
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Characterization
of supercooling suppression of microencapsulated phase change material by
using DSC 总被引:1,自引:0,他引:1
J. L. Alvarado C. Marsh C. Sohn M. Vilceus V. Hock G. Phetteplace T. Newell 《Journal of Thermal Analysis and Calorimetry》2006,86(2):505-509
Supercooling suppression of
microencapsulated n-tetradecane was measured
using differential scanning calorimetry. Results indicate that the degree
of supercooling is positively affected by the amount and type of nucleating
agent present in bulk and microencapsulated n-tetradecane
which it is used as a phase change material (MPCM). Results also demonstrate
that the melting point of the n-tetradecane
is fairly independent of nucleating agent concentration (0 – 4%). Conversely,
the latent heat of fusion of n-tetradecane
decreases considerably with nucleating agent amount and the initiation of
crystallization point is inversely proportional to cooling rate. 相似文献
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无机水合盐相变储能材料具有相变潜热大、相变温度适中、价格低廉等优点,在太阳能高效利用、跨季节储热采暖、工业余废热利用、轻纺行业等方面具有广阔的应用前景。但过冷、相分离、导热系数低等问题限制了其实际应用。本文介绍了水合盐相变储能材料近年来的研究进展,分析了水合盐相变存在的过冷及相分离现象的原因。通过成核剂法、多孔基体吸附法、微胶囊法等方法可以降低其过冷度;通过增稠剂法、晶形改变剂法等方法可以改善其相分离问题;通过与高导热性的纳米粒子、多孔的高导热基体相复合,可以提高其导热性能。最后,指出了今后水合盐相变储能材料的重点研究方向,可以从与计算化学相结合、寻找合适的无机壳材料以及探究共晶体系等方面继续深入研究。 相似文献
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Extensively Reversible Thermal Transformations of a Bistable,Fluorescence‐Switchable Molecular Solid: Entry into Functional Molecular Phase‐Change Materials 下载免费PDF全文
P. Srujana Prof. T. P. Radhakrishnan 《Angewandte Chemie (International ed. in English)》2015,54(25):7270-7274
Functional phase‐change materials (PCMs) are conspicuously absent among molecular materials in which the various attributes of inorganic solids have been realized. While organic PCMs are primarily limited to thermal storage systems, the amorphous–crystalline transformation of materials like Ge‐Sb‐Te find use in advanced applications such as information storage. Reversible amorphous–crystalline transformations in molecular solids require a subtle balance between robust supramolecular assembly and flexible structural elements. We report novel diaminodicyanoquinodimethanes that achieve this transformation by interlinked helical assemblies coupled with conformationally flexible alkoxyalkyl chains. They exhibit highly reversible thermal transformations between bistable (crystalline/amorphous) forms, along with a prominent switching of the fluorescence emission energy and intensity. 相似文献
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Ya Nan ZANG En Yong DING 《中国化学快报》2005,16(10):1375-1378
Latent heat storage is one of the most efficient ways of storing thermal energy.Unlike the sensible heat storage method,the latent heat storage method provides much higher storage density,with a smaller temperature difference between storing and releasing heat.Phase change materials(PCMs)can be used for energy storage and temperature control1,2.Among them,the solid-solid phase change materials are focus of attention3,4.They can be applied in many fields such as solar energy utilization,waste… 相似文献
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Dr. Changhui Liu Tianjian Zhang Tingsong Li Yafei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(29):e202200502
Functional phase-change materials (PCMs) are conspicuously absent in various organic or inorganic solids with diversified applications in which the attributes of these molecular materials have been highly realized. Leakage problem during the phase transition process is the main obstacle on the way of widely use of solid-liquid PCMs who has been recognized to be promisingly practical candidates for energy storage owing to the high energy storage density and small volume change in the phase transition process. Herein, a novel homogeneous-to-heterogeneous-strategy, in which all the starting materials involved display a homogeneous state and the encapsulation framework formed in situ in the encapsulation process, enabled by an aerogel reaction of silica was realized under the catalysis of an organic base. Besides the comprehensive study upon energy storage performance, light-to-thermal conversion and recyclability performance study of the obtained materials reveal the clear superiority over pristine paraffin wax (PW) thanks to the versatility and robustness of this fabrication method. More importantly, the homogeneous-to-heterogeneous-strategy endows a unique adsorption ability with respect to organic pollutant due to the PCMs inside and therefore bearing a great potential to be used in environment protection fields. 相似文献
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J. L. Zeng Y. Y. Liu Z. X. Cao J. Zhang Z. H. Zhang L. X. Sun F. Xu 《Journal of Thermal Analysis and Calorimetry》2008,91(2):443-446
We prepared PANI/tetradecanol/MWNTs composites via in-situ polymerization. DSC results indicated that the composites are good
form-stable phase change materials (PCMs) with large phase change enthalpy of 115 J g−1. The MWNTs were randomly dispersed in the composites and significantly enhanced the thermal conductivity of the PCMs from
0.33 to 0.43 W m−1 K−1. The form-stable PCMs won’t liquefy even it is heated at 80°C, so that the MWNTs were fixed in the composite and the phase
separation of the MWNTs from PANI/tetradecanol/MWNTs composites won’t occur. 相似文献