80#石蜡/膨胀石墨定形复合相变材料的特性表征与分析

以80^#石蜡为相变材料,利用不同粒径膨胀石墨的多孔隙结构,以多层吸附、模压法压制方式制备了80^#石蜡/膨胀石墨定形复合相变材料。通过循环融冻实验分析了80^#石蜡的热稳定性和循环稳定性,滴定滤纸渗漏实验确定了不同组分复合相变材料的渗漏率。采用差示扫描量热仪(DSC)、扫描电子显微镜（SEM）、Hot Disk热常数分析仪等仪器对所制备复合相变材料的相变潜热、多孔基吸附结构、热导率、渗漏率等特性进行了分析。结果表明：当膨胀石墨的添加质量分数达到整体组分的8%时,复合定形相变材料的相变温度为80.86℃（吸热）和76.08℃（放热）,相变潜热为130.12kJ/kg,且渗漏率小于0.3%。制备的复合定形相变材料具有形状稳定、渗漏率低、蓄热密度高的特点,且具有较长的使用寿命。     

定形相变材料的制备及其稳定性能的研究

以石蜡为相变材料,膨胀珍珠岩为基体,采用真空吸附的方法,制备出膨胀珍珠岩——石蜡定形相变材料。为提高定形相变材料的稳定性,在制备的定形相变材料外包覆成膜乳液封装。采用扩散-渗出圈法对材料的稳定性能进行了测试。结果表明:石蜡与膨胀珍珠岩的最佳质量比为2∶1;最佳成膜封装乳液是苯丙乳液,最佳乳液用量是定形相变材料质量的20%;制备得到的成膜封装后的膨胀珍珠岩-石蜡定形相变材料的相变温度为25.05℃,相变潜热为128.93 J/g,稳定性能良好。     

石蜡/MCM-41复合相变材料的结构及热性能

以石蜡为相变材料、SiO2介孔分子筛MCM-41为载体,采用溶液浸渍法制备了石蜡/MCM-41复合相变储能材料。应用SEM与TEM测试了复合材料的微观结构,利用TG-DSC测定了复合材料的相变温度、相变潜热及相变可逆性,通过FTIR对复合材料的兼容性进行了表征。实验表明,复合材料表面孔结构改善了相变可逆性,复合相变储能材料中石蜡的适宜质量分数为40%,相变温度为66.6℃,相变潜热为135.3 J/g。石蜡与MCM-41间是简单的嵌合关系,复合材料具有良好的热稳定性和兼容性。     

石蜡、SEBS和聚苯乙烯共混的复合定形相变材料的制备和热分析

将聚苯乙烯、热塑性弹性体SEBS和石蜡三组分通过熔融共混的方法制备了定形相变储能材料,并且用DSC、TG和SEM等对材料进行了表征,讨论了不同含量的石蜡和SEBS对定形相变储能材料相容性和热性能的影响.实验结果表明,石蜡的质量分数可以提高到70%,三组分的相容性比较好,相变材料的潜热为121.07 J/g,熔点为53.22℃,SEBS能够有效地改善石蜡和聚苯乙烯的相容性,同时通过加入少量的纳米石墨,能够明显提高定形相变储能材料的热导率.     

石蜡/膨胀石墨定形相变材料的性能

以石蜡为相变材料,利用膨胀石墨多孔网络结构,通过物理吸附法制备出石蜡/膨胀石墨复合相变材料,并通过模压法制成定形相变材料板块。采用差示扫描量热分析仪(DSC)、扫描电子显微镜(SEM)、偏光显微镜(POM)和Hot Disk 热常数分析仪等对复合相变材料进行了结构和性能的表征与测量,建立了冷/热循环实验系统以分析材料的蓄/放热性能等。结果表明:石蜡质量分数为80%的定形相变材料相变温度为27.27℃,相变焓为156.6 kJ·kg^-1。制备的定形相变材料具有相变过程形状稳定、热导率高、储热密度大等特点,并具有良好的稳定性和较长的使用寿命。     

用于储能的复合定形相变材料的制备与性能研究

以泡沫聚合法制得的超多孔水凝胶(SPH)为基材,季铵盐类离子液体(ILPCM)为相变材料,氧化石墨烯(GO)为添加剂,制备了一种新型的复合定形相变材料(GO-ILPCM/SPH),且对其性能进行了表征。研究结果表明:SPH是一种潜在的复合定形相变材料的基材,可负载较多的ILPCM,质量分数最高可达约85%。GO-ILPCM/SPH是一种优良的储能相变材料,具有适合冷藏产品的相变温度4℃及较高的相变潜热(约150J/g)。制备的复合定形相变材料具有较快的储热和放热速率,适当地添加GO一类导热性高的物质,可提高其相变储热和放热速率,进而在应用中提高热能利用效率。     

温室用Na2SO4·10H2O-Na2HPO4·12H2O复合定形相变材料制备及性能

十水硫酸钠因过冷度、相分离、相变温度过高和液相泄漏等问题,限制了其在日光温室中的应用,所以需要对其进行改性研究。本文通过添加十二水磷酸氢二钠改善过冷度、氯化钾降低相变温度以及树脂作基体解决相分离和液相泄漏,制备出了Na₂SO₄·10H₂O+80% Na₂HPO₄·12H₂O+6% KCl+6%树脂（质量分数,余同）的复合定形相变材料,并进行了升降温、差示扫描量热仪（DSC）和循环稳定性的测试。结果表明：添加80%十二水磷酸氢二钠,其过冷度和相变潜热分别为1.35℃和268.7J/g;再添加6% KCl可以使相变温度达到温室所需温度23.89℃,且潜热为183.25J/g;最后加入6%树脂可以抑制相变材料的相分离和液相泄漏等问题,其凝固温度为11.56℃,熔化温度为22.61℃,过冷度为1.41℃,相变潜热为143.6J/g。复合定形相变材料在加热到50℃时,没有液相泄漏产生;经过100次循环,其潜热降为127.8J/g,比循环1次衰减了11.2%。得到的复合定形相变材料具有潜热值较大、相变温度合适、热稳定性较好等优点,适合应用于日光温室领域。     

多孔SiC陶瓷/石蜡复合相变材料定型封装及热性能研究

以微米级SiC粉为原料,采用冷冻干燥工艺制备具有连贯层状孔结构的SiC陶瓷。以多孔SiC陶瓷为基体,石蜡为相变芯材,通过真空浸渍法制备多孔SiC陶瓷/石蜡复合相变材料,研究了石蜡在层状多孔SiC陶瓷内的浸渗行为及复合材料的储热性能。结果表明,层片状多孔SiC陶瓷的显微形貌对石蜡的浸渗过程及储热性能有明显影响。当石蜡负载量为21.7%(质量分数)时,复合相变材料熔融温度为59.6 ℃,凝固温度为53.9 ℃,相变潜热为28.4 J/g,室温下的热导率为2.4 W·(m·K)^-1。复合相变材料吸热峰和放热峰强度随着石蜡负载量减少而降低,当温度为200 ℃时,多孔SiC陶瓷/石蜡复合相变材料失重为5%(质量分数),表明材料具有良好的热稳定性。复合相变材料在100 ℃热处理30 min后陶瓷基体未发生形变,经100次热循环后具有稳定的相变潜热和良好的定型能力。     

石蜡定形相变材料的包裹及热性能

利用原位聚合法,提出了对定形相变材料进行无机高分子材料再包裹,制备了硅胶封装石蜡定形相变材料的微胶囊,其石蜡的含量最高达到w(石蜡)=69.12%。用差示扫描量热仪(DSC)测定了微胶囊的热性能,并将测定粉体材料润湿性能的W ashburn方程应用于相变材料的亲油亲水性测定,评价了定形相变材料在胶囊封装前后的亲水性变化。结果表明,经硅胶封装的相变材料其相变焓为153.46 J.g-1,相变焓降低较少,而亲水性能有很大提高,确定了微胶囊产品中石蜡最佳质量分数为w(石蜡)=50%~56%。     

石蜡/碳纳米管复合相变材料的性能研究

针对太阳能烟囱蓄热单元的应用需求,以石蜡为相变材料,向其中添加碳纳米管,通过两步法制备出碳纳米管质量分数分别为0.5%、1%、2%、3%、5%的复合相变材料,并对其热物性及循环稳定性进行了实验研究。结果显示,碳纳米管的添加可以有效提高相变材料的热导率和相变过程的传热速率,当添加的质量分数为5%时,其热导率达0.62 W/m2·K,比纯石蜡提高了1.21倍,蓄、放热速率分别比纯石蜡提高了44%、45%;碳纳米管的添加降低了相变材料的相变潜热,当添加的质量分数为5%时,其相变潜热为170 J/g,为纯石蜡的81%;石蜡与碳纳米管只是简单的物理复合,且制备的相变复合材料具有较好的循环稳定性。     

Preparation,thermal properties and thermal reliability of eutectic mixtures of fatty acids/expanded vermiculite as novel form-stable composites for energy storage

This paper deals with the preparation, characterization, thermal properties and thermal reliability of novel form-stable composite phase change materials (PCMs) composed of eutectic mixtures of fatty acids and expanded vermiculite for thermal energy storage. The form-stable composite PCMs were prepared by incorporation of eutectic mixtures of fatty acids (capric–lauric, capric–palmitic and capric–stearic acids) within the expanded vermiculite by vacuum impregnation method. The composite PCMs were characterized by SEM and FTIR techniques. Thermal properties of the composite PCMs were determined by differential scanning calorimeter (DSC) method. DSC results showed that the melting temperatures and latent heats of the prepared composite PCMs are in the range of 19.09–25.64 °C and 61.03–72.05 J/g, respectively. The thermal cycling test including 5000 heating and cooling process was conducted to determine the thermal reliability of the composite PCMs. The test results showed that the composite PCMs have good thermal reliability and chemical stability. Furthermore, thermal conductivities of the composite PCMs were increased by adding 10 wt% expanded graphite. Based on all results, the prepared form-stable composites can be considered as promising PCMs for low temperature thermal energy storage applications due to their satisfactory thermal properties, good thermal reliability, chemical stability and thermal conductivities.     

Preparation and thermal characterization of expanded graphite/paraffin composite phase change material

Expanded graphite (EG)/paraffin composite phase change materials (PCMs), with mass fraction of EG varying from 0 to 10 wt.%, were prepared and characterized. Polarizing optical microscope investigation showed that compact EG networks formed gradually with increase in the mass fraction of EG. These networks provided thermal conduction paths which enhanced the thermal conductivity of the composite PCMs, e.g., an addition of 10 wt.% EG resulting in a more than 10-fold increase in the thermal conductivity compared to that of pure paraffin. Thermal characterization of the composite PCMs with a differential scanning calorimeter (DSC) revealed the effect of the porous EG on the phase change behavior of paraffin. The shifts in the phase change temperatures were observed. The maximum deviation of the melting/freezing points of the composite PCMs from that of pure paraffin was 1.2 °C whereas that of the peak melting/freezing temperature was 5.6 °C. The DSC investigation also showed an anomaly in the latent heat of the paraffin in the composite PCMs in that it first increased and then decreased with increase in the EG fraction. Heat storage/retrieval tests of the composite PCMs in a latent thermal energy storage system showed that the heat storage/retrieval durations for EG(10)/paraffin(90) composite were reduced by 48.9% and 66.5%, respectively, compared to pure paraffin, which indicated a great improvement in the heat storage/retrieval rates of the system.     

Eudragit S (methyl methacrylate methacrylic acid copolymer)/fatty acid blends as form‐stable phase change material for latent heat thermal energy storage

By composing (Eudragit S) with fatty acids (stearic acid (SA), palmitic acid (PA), and myristic acid (MA)), form‐stable phase change materials (PCMs), which can retain the same shape in a solid state even when the temperature of the PCMs is over the melting points of the fatty acids, are prepared. The compatibility of fatty acids with the Eudragit S is proved by microscopic investigation and infrared (FTIR) spectroscopy. The melting and crystallization temperatures and the latent heats of melting and crystallization of the form‐stable PCMs are measured by Differential Scanning Calorimetry (DSC) method. The maximum mass percentage of all fatty acids in the form‐stable PCMs is found as 70%, and no leakage of fatty acid is observed at the temperature range of 50–70°C for several heating cycles. Thermal properties obtained from the DSC analysis indicate that the Eudragit S/fatty acid blends as form‐stable PCM have great potential for passive solar latent heat thermal energy storage (LHTES) applications in terms of their satisfactory thermal properties and utility advantage. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1402–1406, 2006     

癸酸-石蜡/膨胀石墨定形相变材料的制备及性能

通过物理吸附法将癸酸-石蜡（CA-PC）二元低共熔混合物与膨胀石墨（EG）复合形成癸酸-石蜡/膨胀石墨定形相变材料，实验结果显示，CA与PC、CA-PC与EG的最佳质量配比分别为8.1∶1.9和7∶1。利用扫描电子显微镜（SEM）和傅里叶红外光谱仪（FTIR）分析了定形相变材料的微观形貌和结构特点，发现CA-PC/EG的FTIR曲线上同时存在二元低共熔混合物和膨胀石墨的特征吸收峰，表明二元低共熔混合物与膨胀石墨之间没有发生化学反应，二者依靠表面张力和毛细力作用在一起，并且CA-PC二元低共熔混合物依靠物理作用被有效包封于EG的孔隙中，经过1000次加速冷热循环后，基本没有液态二元复合相变材料泄漏。通过差示扫描量热仪（DSC）得到CA-PC/EG的熔化温度和凝固温度分别为27.04℃和22.26℃，熔化潜热和凝固潜热分别为144.4J/g和133.7J/g，且EG的高导热性促进了CA-PC的蓄放热速率。同时，根据热重分析（TG）与蓄放热实验结果发现其拥有优良的热可靠性和耐热性能。因此，该CA-PC/EG定形相变材料是一种良好的低温储能材料。     

高导热膨胀石墨/棕榈酸定形复合相变材料的制备及储热性能研究

采用棕榈酸(palmitic acid, PA)作为相变材料,膨胀石墨(expanded graphite, EG)作为添加基质,通过“熔融共混-凝固定形”工艺制备了PA/EG定形复合相变材料以提高相变材料的综合性能。预测并制备了21种不同配比的定形复合相变材料,对其形貌结构和孔隙率进行了微观表征与理论分析,并在此基础上对样品进行了传热性能分析、热物性测试、热稳定性研究和储热性能分析。SEM形貌分析显示所使用工艺可使棕榈酸能较好地被吸附于膨胀石墨的孔隙结构并使之均匀分布;DSC测试结果表明定形复合相变材料[70%(质量) PA]的焓值为193.01 J/g,纯PA的焓值为275.35 J/g,对应于熔点分别为61.08℃和59.53℃。EG的添加,可有效提高相变材料的热导率。当样品密度为900 kg/m³,EG含量为30%(质量)时,定形复合相变材料的热导率为14.09 W/(m·K),相比于纯PA[0.162 W/(m·K)]提高约87倍;对制备的样品进行50次循环稳定性实验,EG含量为24%(质量)和30%(质量)的样品形态均未出现明显变化,表现出良好的充放热循环稳定性。     

硬脂酸/活化凹凸棒石复合相变储热材料的制备与表征

以热活化的甘肃临泽凹凸棒石为基体,采用热熔法和浸渍法制备了硬脂酸/活化凹凸棒石复合相变储热材料。利用红外光谱仪(FTIR)、X射线衍射仪(XRD)和扫描电子显微镜(SEM)等方法表征了复合材料的结构,采用示差量热扫描仪(DSC)和储放热实验考察了复合材料的储/放性能和稳定性。结果表明采用热熔法和溶液浸渍法制备的材料具有相同的结构,硬脂酸按38.5%的负载率以物理作用吸附于活化凹凸棒石表面,其相应的相变焓分别为68.44 J/g和69.06 J/g。稳定性实验表明2种材料均具有良好的化学稳定性,但热稳定性存在差异,热熔法制备的复合材料的热稳定性优于浸渍法制备的复合材料。     

Sustainable lignin-based polyols as promising thermal energy storage materials

Six lignin-based polyols (LBPs) have been prepared by cationic ring opening polymerization of an oxirane in the presence of an organosolv lignin in tetrahydrofuran (THF) as reaction media and co-monomer. The prepared LBPs have been characterized and tested for the first time as phase change materials (PCMs) for thermal energy storage (TES) at low temperature. It was found a strong influence of the LBPs composition on their performance to storage thermal energy. Thus, LBPs with higher THF wt% content and lower oxirane/THF mass ratio exhibit the highest latent heats. Furthermore, a clear inversely proportional trend between the oxirane/THF mass ratio and the melting temperatures of the prepared LBPs was noticed. Among the prepared LBPs, the highest obtained latent heat was 53.7 J/g demonstrating the potential application of lignin as feedstock for PCMs preparation. To the best of our knowledge, this is the first time that a biomass derived PCM based on lignin has been studied and considered for TES applications at low temperature. LBPs show energetic solid–liquid transitions that point out their promising potential as bio-PCMs. This work paves the way to introduce new bio-based PCMs from lignin in TES systems, for example, in a more sustainable construction sector.     

多熔点相变材料堆积蓄热床蓄热性能分析

对采用多种不同熔点相变材料（PCM）构成的堆积蓄热床进行了数值分析。热水作为换热流体（HTF）自上而下流经蓄热床,熔化相变材料、蓄积相变潜热。石蜡作为相变材料被注射入聚碳酸酯球壳内形成相变胶囊,根据熔点高低依次排放在蓄热床的不同位置,熔点越高距离热水进口越近。假定流场稳定,采用一维Schumann模型计算HTF温度,相变模拟采用显热容法。分别对两种排列方式下采用2种、3种以及4种相变材料的蓄热床的蓄热过程进行了基于热力学第一及第二定律的性能分析,并将结果与单相变材料蓄热床进行比较。基于热力学第一定律分析结果表明,采用多种相变材料构成的蓄热堆积床蓄热速度更快,能量效率更高。基于热力学第二定律分析表明,平均熔点更高的蓄热床能够储存更高的火用。结果表明采用多熔点相变材料构成的堆积蓄热床能够显著地缩短蓄热时间,改进蓄热性能。     

相变热界面材料导热增强及定形改善的研究进展

将相变时伴随潜热的相变材料（phase change material, PCM）特别是潜热值较大的固-液PCM引入热界面材料（TIM）领域,有望获得兼具储热和导热双功能的新型热界面材料——相变热界面材料（phase change thermal interface material, PCTIM）。然而,鉴于固-液相变材料的热导率普遍较低且存在液相流动泄漏问题,使得增强热传导并同时提升固-液相变材料的定形性成为研制高性能相变热界面材料（PCTIM）的关键。本文系统评述了国内外研究者在提升相变热界面材料热导率以及改善其定形性方面的策略及其研究进展。文中指出,目前强化PCTIM导热的手段主要有添加高导热填料、促使填料有序结构化以及使用低熔点金属等。在改善定形性方面,已运用的策略主要包括使用柔性载体负载固-液PCM以在保证一定柔性的基础上克服其液相泄漏问题,使用固-固PCM来取代固-液PCM来彻底避免液相泄漏问题的出现,以及将固-液PCM封装在微米级或纳米级胶囊内,旨在牺牲借助液相PCM增加柔性的功能,而且通过提高PCTIM的潜热值来提升其抗热流冲击性能。文章指出,当前已研制的PCTIM热导率还较低,储热和导热这两个特性对其散热性能的协同影响机制缺乏深入了解。今后,需要探索研制高性能PCTIM的新策略,以期获得定形性好、热导率高、界面热阻小且潜热值大的PCTIM,从而满足5G通信等高热流密度芯片的散热需求。