相变材料微胶囊研究进展

相变材料微胶囊有许多优点,如增加了热传导的面积,降低了相变材料与外界环境的反应活性并在相变发生时可以控制蓄能材料体积的变化.介绍了可作为芯材的相变材料及其主要性质,重点总结了2002年以来相变材料微胶囊的制备方法、表征与材料特点,同时讨论了国内外相变材料微胶囊在建筑节能、纺织及其他领域中的应用现状、存在的问题以及发展前景.     

原位聚合法制备相变材料微胶囊及其致密性

采用原位聚合法以三聚氰胺-尿素-甲醛预聚物为壁材, 包覆一种相变点为24 ℃、相变焓为225. 5 J / g 的有机相变材料, 制备一种具有调温储热功能的复合材料。通过改变三聚氰胺和尿素摩尔比对微胶囊壁材渗透性和强度进行研究。相变材料受热时会在微胶囊内部产生较大的蒸汽压使微胶囊壁破裂渗出芯材, 采用TGA 测定微胶囊热失重温度得到胶囊壁破裂时的温度。采用压力法观察微胶囊受力后的形貌, 对其强度进行评价。采用752型紫外分光光度仪对微胶囊壁渗透性进行表征。实验结果表明: 微胶囊呈球形, 平均粒径小于5μm , 固化剂滴加速度为0. 8 mL/ min 时微胶囊形貌最好。当尿素质量为反应总单体质量的20 %时, 与不加尿素相比, 微胶囊热失重温度大约提高30 ℃, 可以承受6. 0 MPa 压力而不破损, 并且渗透性并不增加。      

Fabrication of electrospun nanofibre yarn based on nylon 6/microencapsulated phase change materials

Twisted nylon 6 nanofibre yarns containing microencapsulated phase change materials (MPCMs) were fabricated via electrospinning to prepare thermal regulating nanofibre yarns. Electrospun nanofibre yarns with different contents of MPCMs including 0.375, 0.75, 1.5 and 3 wt% were prepared. The surface morphology, crystallisation and thermal properties of the yarn samples were characterised by scanning electron microscopy (SEM) and differential scanning calorimetry, respectively. SEM results showed that electrospun composite fibres and yarns had good morphology with smooth surface and the MPCMs were randomly distributed on the composite yarn surface, inside the nanofibres and between the fibres in the yarn structure. Additionally, the SEM results suggested that the average diameters of nylon 6/MPCM nanofibres decreased from 0.23 ± 0.03 µm for neat nylon 6 to a minimum of 0.10 ± 0.02 µm for composite yarn containing 3 wt% MPCM. However, nylon 6/MPCM nanofibre yarn diameter displayed a complex behaviour; the average diameters of electrospun composite yarns increased upon addition of MPCM and reached a maximum value of 165.1 ± 5.11 µm for composite yarn containing 0.75 wt% MPCM, then decreased markedly. These changes in nylon 6/MPCM nanofibres and yarn diameters have been discussed in terms of electrospinning solution properties and twist parameter. The melting enthalpy values of MPCM in the composite nanofibre yarns increased as the content of MPCMs increased up to the highest content and higher than 80% of the heat storage capacity of MPCMs was retained after electrospinning.     

The durability of cementitious composites containing microencapsulated phase change materials

This study investigates the durability of cementitious composites containing microencapsulated phase change materials (PCMs). First, the stability of the PCM's enthalpy of phase change was examined. A reduction of around 25% in the phase change enthalpy was observed, irrespective of PCM dosage and aging. Significantly, this reduction in enthalpy was not caused by mechanical damage that was induced during mixing, but rather by chemical interactions with dissolved SO₄^2- ions. Second, the influence of PCM additions on water absorption and drying shrinkage of PCM-mortar composites were examined. PCM microcapsules reduced the rate and extent of water sorption; the former was due to their non-sorptive nature which induces hindrances in moisture movement, and the latter was due to dilution, i.e., a reduction in the volume of sorptive cement paste. On the other hand, PCM inclusions did not influence the drying shrinkage of cementitious composites, due to their inability to restrain the shrinkage of the cement paste. The results suggest that PCMs exert no detrimental influences on, and, in specific cases, may even slightly improve the durability of cementitious composites.     

聚氨酯固-固相变材料的合成与性能分析

以聚乙二醇-6000(PEG-6000),4,4’-二苯基甲烷二异氰酸酯(MDI),1,4-丁二醇(BDO)为原料合成不同软段含量的一系列聚氨酯相变储能材料(PUPCMs),采用红外光谱分析仪(FTIR)、热重(TGA)表征材料的结构和热稳定性,同时差示扫描量热仪(DSC)、动态热机械分析(DMA)研究PUPCMs的热学性能,实验发现,外力场影响材料的性能,使材料的熔融温度向低温方向偏移。     

聚乙二醇改性相变微胶囊制备MicroPCMs-WF/HDPE复合材料物理力学性能

以正十二烷醇（DA）为芯材,密胺树脂（MF）和聚乙二醇改性密胺（PMF）树脂为壁材制备了相变微胶囊（MicroPCMs）,并分别添加到木粉/高密度聚乙烯（WF/HDPE）复合材料中,获得了具有相变蓄热能力的MicroPCMs-WF/HDPE复合材料。采用SEM、FTIR和纳米压痕等方法对MicroPCMs的表面形态、力学性能进行了分析与表征,同时对MicroPCMs-WF/HDPE复合材料的物理力学及热性能进行了测试。结果表明:经聚乙二醇改性后,改性微胶囊（PMF-MicroPCMs）的弹性模量和硬度较未改性微胶囊（MF-MicroPCMs）分别增加了13.9%和30.0%;MicroPCMs-WF/HDPE复合材料的熔融温度区间（22.2~28.7℃）满足人体舒适温度范围,较纯WF/HDPE复合材料温度变化速率明显减缓;相比纯WF/HDPE复合材料,MicroPCMs-WF/HDPE复合材料的吸湿性、冲击强度和表面硬度增加,弯曲和拉伸性能下降;PMF-MicroPCMs-WF/HDPE复合材料的性能均优于MF-MicroPCMs-WF/HDPE复合材料,且达到了木塑装饰板材的力学性能标准要求。      

相变微胶囊悬浮液传热性能的研究进展

相变微胶囊悬浮液作为一种潜热型功能流体,其独特的性能使其受到科研工作者的关注。在回顾了现有相变微胶囊悬浮液传热性能的研究进展,对相变微胶囊悬浮液的导热性能、对流传热特性分别进行介绍。讨论了悬浮液的体积浓度、雷诺数(Re)、斯蒂芬数(Ste)、努塞尔数(Nu)及无量纲过冷度等因素对相变微胶囊悬浮液换热能力的影响,以及相变微胶囊悬浮液管内换热特性。本文针对相变微胶囊悬浮液中添加纳米粒子(纳米Al_2O_3,纳米Fe,纳米TiO_2)和磁性材料对其导热系数和强化传热的提升情况进行了讨论,并指出了目前研究存在的问题和今后研究的发展方向。     

SiO2/十八烷酸相变微胶囊的制备与表征

以水玻璃和十八烷酸为基本原料,利用两者反应生成表面活性剂十八烷酸钠来促进十八烷酸在水中的分散与形成胶束,并使由水玻璃提供的硅氧四面体[SiO4]完成对胶束的包裹,然后再通过调整pH值,使十八烷酸钠还原为具有相变性能的十八烷酸,通过上述方法制得的以[SiO4]结构为囊壁、十八烷酸为囊芯的相变微胶囊.SEM、DSC、XRD、FTIR等对其表面形貌、热性能、囊壁和囊芯结构的表征结果表明,其粒度均匀,为在0.40～0.6靘,表面光滑,相变焓为78.2J/g.该方法较好的解决了相变微胶囊制备过程相变材料的分散问题,既使辅助材料的品种简化,又提高了微胶囊中相变材料的有效含量.     

相变材料微/纳胶囊的研制及其在红外隐身中的应用

相变材料微/纳胶囊是利用保护性囊壁包裹相变材料制得的微粒,它们在相变材料历经相转变时可以吸收、储存和释放大量的潜热,而本身温度基本不变。本文综述了相变材料微/纳胶囊的主要制备方法及最新研究进展,介绍了它们在红外隐身中的应用,并展望了其应用前景。     

木质素基分级多孔碳复合相变材料的制备与性能研究

以木质素为原材料,通过模板法和化学活化法制备出木质素基多孔碳LTC和木质素基分级多孔碳LTCA,以LTCA为载体,采用真空浸渍法负载相变材料聚乙二醇(PEG4000),制备出木质素基分级多孔碳/聚乙二醇(LTCA/PEG)复合相变材料.通过扫描电镜、透射电镜、全自动比表面积及孔隙分析仪、X射线衍射分析、傅里叶变换红外光...     

聚乙二醇(PEG)/聚乙烯醇(PVA)固-固相变材料受限非等温结晶动力学研究

采用接枝共聚法将具有相变特征的聚乙二醇(PEG)接枝到具有较高熔点的聚乙烯醇(PVA)主链上,得到系列性能稳定的PEG/PVA高分子固固相转变材料,利用DSC法对PEG受限状态下非等温结晶行为进行研究.结果表明,随着降温速率增大,峰值温度Tp向低温移动,半结晶时间t1/2逐渐减小,结晶速度G逐渐增大.接枝共聚体系Tp低于纯PEG4000,半结晶时间t1/2大于纯PEG4000.对于接枝共聚体系而言,接枝率对半结晶时间t1/2影响不大,共聚体系中的Avrami指数大多数在2～3之间,比等温结晶更加复杂.运用Jeziorny方法和莫志深方法比较适用于本体系非等温结晶动力学的研究.     

相变材料的复合及其热性能研究

针对相变材料应用领域中对相变温度和相变焓的具体要求,采用复合的方法重点对相变材料的相变温度进行调节,复合出具有特定相变温度和较高相变焓的相变材料.论述了相变材料的复合原理,研究了4种相变材料的复合及其热性能,通过理论计算与实际测试相比较,筛选出复合物的最佳配比.研究表明:通过相变材料的复合可以调节材料的相变温度至所需要的范围,并具有较高的相变焓,可保持良好吸收或释放能量的能力.     

Effect of crystalline phase, orientation and temperature on the dielectric properties of poly (vinylidene fluoride) (PVDF)

The effect of crystalline phase, uniaxial drawing and temperature on the real () and imaginary () parts of the relative complex permittivity of poly (vinylidene fluoride) (PVDF) was studied in the frequency range between 10² and 10⁶ Hz. Samples containing predominantly and phases, or a mixture of these, were obtained by crystallization from a DMF solution at different temperatures. phase samples were also obtained from melt crystallization and from commercial films supplied by Bemberg Folien. Different molecular orientations were obtained by uniaxial drawing of and phase samples. The results showed that the crystalline phase exerts strong influence on the values of and , indicating that the _a relaxation process, associated with the glass transition of PVDF, is not exclsively related to the amorphous region of the polymer. An interphase region, which maintains the conformational characteristics of the crystalline regions, should influence the process decisively. The molecular orientation increased the values of for both PVDF phases and modified its dependence with temperature over the whole frequency range studied. The influence of the crystallization and molecular orientation conditions on the dc electric conductivity (_dc) were also verified. The value of _dc was slightly higher for samples crystallized from solution at the lowest temperature and decreased with draw ratio.     

相变储能材料研究进展

综述了固-固相变储能材料（s-S PCMs：sofid-solid phase change materials）、固-液相变储能材料（s-1 PCMs：solid—liquid phase change materials）的主要优缺点，并主要介绍了以下2种封装方式：（1）PCMs与基体材料复合制成定型PCMs，包括：与有机高分子材料机械共混、用无机多孔材料封装；（2）PCMs微囊化。此外，还分析了PCMs的主要应用领域及PCMs的主要研究方向。     

基于T-history法确定相变材料的相变区间和相变焓

相变区间是决定相变材料使用性能的主要因素,也直接影响相变焓的计算。T-history法设备构造简单,测试试样体积大,可用于确定相变材料的相变区间和相变焓。选取癸酸、六水氯化钙复合物、石蜡3种典型相变材料,基于T–history法得到待测材料温度-时间曲线,改进计算过程得到相变材料焓温曲线。由温度-时间曲线的一阶,二阶导数选取切点,采用切线法确定相变区间,结合焓温曲线求得相变焓。3种材料测试结果:癸酸和石蜡相变起点和终点温度标准差均小于0.5℃,相变焓标准差率小于10%;六水氯化钙复合物结晶起点和终点温度标准差分别为1.9℃和0.8℃,融化起点和终点温度标准差小于0.5℃,相变焓标准差率小于10%。引入临界比热容分析相变区间内当量比热容,结果表明,确定的相变区间内的当量比热容大于临界比热容。改进后的T-history法可用于确定相变区间和相变焓。     

复合相变储冷材料的制备及性能研究

以十二烷基苯磺酸钠(SDBS)作为分散剂,多层石墨烯、TiO₂/石墨烯(m(TiO₂):m(石墨烯)=25∶75)和TiO₂颗粒作为导热添加剂,加入到二元复合有机储冷材料中(m(壬酸):m(葵醇)=60:40),制备了复合相变储冷材料。通过吸光度、DSC和热导率测试等手段,对复合相变储冷材料的稳定性、相变温度、相变潜热及热导率进行了评价分析。结果表明,分散剂和导热添加剂的加入,对储冷材料的相变温度和相变潜热影响不大,但对热导率影响较大。当分散剂SDBS浓度为0.2 g/L,导热添加剂(分别为TiO₂/石墨烯和TiO₂颗粒)浓度为0.5 g/L时,复合相变储冷材料具有较好的稳定性,其热导率分别为为0.2211和0.2096 W/(m·K),相比没有加入任何导热添加剂的储冷材料的热导率(0.1738 W/(m·K)),分别提高了27.22%和20.61%;当分散剂SDBS浓度为0.3 g/L,导热添加剂多层石墨烯浓度为0.3 g/L时,复合相变储冷材料处于稳定状态,其热导率为0.2...     

Nanoelectronic programmable synapses based on phase change materials for brain-inspired computing

Brain-inspired computing is an emerging field, which aims to extend the capabilities of information technology beyond digital logic. A compact nanoscale device, emulating biological synapses, is needed as the building block for brain-like computational systems. Here, we report a new nanoscale electronic synapse based on technologically mature phase change materials employed in optical data storage and nonvolatile memory applications. We utilize continuous resistance transitions in phase change materials to mimic the analog nature of biological synapses, enabling the implementation of a synaptic learning rule. We demonstrate different forms of spike-timing-dependent plasticity using the same nanoscale synapse with picojoule level energy consumption.     

NaCl和分散剂对相变储能蜡微胶囊制备的影响

以常低温相变储能蜡RT31为芯材,脲醛树脂为壁材,采用原位聚合法制备了相变储能蜡微胶囊.利用傅立叶红外光谱仪、扫描电子显微镜、差示扫描量热仪等对样品进行分析和表征,讨论了助剂NaCl及两种不同类型的分散剂对微胶囊性能和形貌的影响.实验结果表明,加入一定量的NaCl能显著提高微胶囊的相变潜热,使得微胶囊的包封率由75.8%升高到92.5%,在微胶囊成型后期加入一定量的分散剂能明显改善微胶囊的表面形貌和粒径均匀度.     

In vitro enzymatic biodegradation of amino acid based poly(ester amide)s biomaterials

A systematic in vitro biodegradation study of regular poly(ester amide)s (PEAs) composed of naturally occurring hydrophobic alpha-amino acids, fatty diols and dicarboxylic acids was carried out in the presence of hydrolases like trypsin, alpha-chymotrypsin, and lipase. An automatic potentiometric titration method was used to examine the biodegradation property of the PEAs. Spontaneous immobilization (absorption) of the enzymes onto the PEAs films surfaces was observed. The surface immobilized enzyme not only accelerated the erosion of the PEAs but also was able to catalyze the hydrolysis of both low-molecular-weight (ATEE) and high-molecular-weight (protein) external substrates. It was found that the enzyme surface absorption process is reversible by nature. A kinetic method for a quantitative determination of the enzyme desorbed from the film surface was developed. The enzymes could also be impregnated into the PEAs to make them "self-destructive" at a target rate. A comparison of the PEAs' in vitro biodegradation data with polylactide (PDLLA) showed that PEAs exhibited a far more tendency toward enzyme catalyzed biodegradation than PDLLA.     

基于硫属化物相变材料的可重构太赫兹超表面器件的研究进展

超表面在控制电磁波的强度、相位、偏振和复杂波前等方面发挥了重要的作用,通过与各种主动调控手段结合可实现动态可调谐器件。本文分析总结了近期基于Ge₂Sb₂Te₅ (GST)的太赫兹超表面器件的研究进展,介绍了GST在太赫兹波段的光谱特性和可逆相变条件,重点回顾了GST与超表面设计相结合用于实现对太赫兹波的振幅、偏振以及波前的非易失、可重构、和多级操纵的前沿研究工作,并讨论展望了未来的发展前景和需要解决的问题。