癸酸-石蜡二元低共熔复合相变材料的制备及性能研究

为充分利用冬季太阳辐射热,将传统建筑材料与相变材料结合形成新型绿色建筑材料,可充分发挥其储能控温特性,并缩短热量被吸收进室内的时间,降低冬季采暖能耗,实现建筑节能。利用熔融共混法制备了质量配比为0.81∶0.19、共晶温度为27.4℃的癸酸-石蜡(CA-PC)低共熔复合相变材料。通过傅里叶红外光谱仪(FT-IR)对该二元低共熔物的化学结构进行分析,发现CA与PC是通过物理作用结合的,无新物质产生;并且通过500次加速冷热循环实验,证实了CA-PC复合相变材料具有良好的热循环稳定性。此外,由差示扫描量热仪(DSC)分析得到CA-PC的相变温度为27.0℃,相变潜热为153.7 J/g,这一结果与步冷曲线所得的共晶温度相吻合,进一步表明了该复合相变材料在用于制备新型建筑储能材料领域极具发展潜力。     

硬脂酸-十八醇二元复合相变材料性能研究

以硬脂酸(S18)和十八醇(C18)为原料,通过熔融共混法制备二元复合相变材料(PCMs)。复合后的相变材料克服十八醇二次相变的缺点,获得合适的相变温度。采用步冷曲线法测定不同配比下二元相变材料的结晶温度,共晶混合物的相变温度为51.6℃。T-History法和差示扫描量热仪(DSC)测试结果表明,复合相变材料的相变热约为210 J/g。利用红外光谱(FT-IR)表征复配后材料结构,表明硬脂酸和十八醇是通过分子力结合。35～90℃冷热循环(800次)测试表明,复合材料未出现分层现象,相变热几乎无变化,相变温度变化区间不高于0.6℃,且400次热循环后相变温度不再变化,热稳定性能良好。     

月桂酸-十四醇二元复合相变材料的相变特性

为了获得适合在建筑领域应用的相变材料和相变温度,以月桂酸(LA)和十四醇(TD)为原料,采用熔融共混法制备一系列二元酸-醇相变材料。采用步冷曲线法测定不同组分二元相变材料的结晶温度,通过绘制的相图确定二元体系低共晶点,LA-TD二元体系在23.1℃达到共晶点;采用红外光谱(FTIR)表征复合相变材料的结构,表明复合相变材料中LA与TD通过分子间作用力结合在一起;采用DSC差示扫描量热法测量LA-TD混合物的相变温度及相变潜热,低共晶物的相变起始温度为24.46℃,相变潜热达到150.45 J/g,经300次0~60℃冷热循环后热稳定性良好。     

六水硝酸镁-硝酸锂共晶盐/膨胀石墨复合相变材料的制备及性能强化

采用熔融共混法在六水硝酸镁中掺入不同质量分数的硝酸锂成功制备了六水硝酸镁-硝酸锂共晶相变材料.六水硝酸镁-硝酸锂共晶盐的共晶点在质量比85:15附近.利用差示扫描量热仪得到了共晶相变材料的相变温度为72.46℃,相变潜热为193.7 kJ/kg,通过步冷曲线测得共晶盐的放热平台明显且过冷度小于1.5℃,X射线衍射测试表...     

硬脂酸/碳纳米管/聚甲基丙烯酸甲酯复合相变胶囊的制备与热性能研究

首先使用浸渍法制备硬脂酸/碳纳米管(SA/α-CNTs)复合相变材料,然后采用原位聚合法以聚甲基丙烯酸甲酯(PMMA)为壁材,以制得的SA/α-CNTs为芯材,制备硬脂酸/碳纳米管/聚甲基丙烯酸甲酯(SA/α-CNTs/PMMA)复合相变胶囊。通过SEM、TEM、FT-IR表征材料的微观结构与组成,通过DSC、TGA、步冷曲线分析材料的相变温度、相变焓、热稳定性能和导热性能。实验结果表明与纯硬脂酸相比,SA/α-CNT提高到207.95 J/g SA,相变时间由1000 s缩短到520 s,硬脂酸在SA/α-CNTs/PMMA相变微胶囊的完全热分解温度从280℃提升到310℃,说明PMMA的包覆和碳纳米管的复合可提升材料的热稳定性。     

膨胀石墨/多壁碳纳米管基共晶盐复合相变材料的制备及热特性北大核心CSCD

单一水合盐作为相变蓄热材料使用时常常由于过冷、相分离、易泄漏以及其相变温度而受到限制,因此迫切需要制备出一种储热密度高、相变温度适宜、热导率大的复合相变材料。本工作采用熔融共混法在NH_(4)Al(SO_(4))_(2)·12H_(2)O(AASD)中掺入不同质量分数的MgSO_(4)·7H_(2)O(MSH),成功制备了AASD-MSH共晶盐相变材料,其质量比为55∶45,相变温度为76.4℃,相变潜热为189.4 J/g。共晶盐的X射线衍射图谱和傅里叶红外光谱表明其为物理混合。引入质量分数1%成核剂CaCl_(2)·2H_(2)O及1%增稠剂可溶性淀粉降低共晶盐过冷度,过冷度从34.9℃降低至28.0℃。引入改性膨胀石墨(MEG)与多壁碳纳米管(MWCNTs)制备复合相变材料,改善共晶盐易泄漏及热导率低等问题,当MWCNTs质量分数为0.5%时,复合相变材料的热导率高达8.185 W/(m·K),为共晶盐的19.98倍,其中共晶盐占比为75.6%,相变温度为74.3℃,相变焓值为133.5 J/g,过冷度进一步降低至22.2℃。热重实验表明与MEG-MWCNTs的复合增加了共晶盐的热稳定性,且经过100次冷热循环后复合相变材料的相变焓值基本不变,具有良好的循环稳定性。本工作制备得到的AASD-MSH/MEG-MWCNTs复合相变材料是一种相变温度适合、相变焓值较高、热导率较大的相变材料,且具有良好的热循环稳定性,应用潜力极大。     

月桂酸-肉豆蔻酸/膨胀石墨封装复合相变储能材料的制备及表征

以月桂酸-肉豆蔻酸(LA-MA)低共熔酸为芯材,膨胀石墨(EG)为担载材料,利用熔融吸附法制备LA-MA/EG复合相变材料。采用有机无机复合硅溶胶对其包封定形,得到LA-MA/EG封装复合相变材料用来改善相变过程中液态脂肪酸的渗漏问题,并通过SEM、FT-IR和DSC对该封装复合相变材料的结构和性能进行表征。结果表明:LA-MA/EG封装复合相变材料的潜热和相变温度为119.5 J/g和31.2℃;封装材料并未引起新生成物的出现,且可明显抑制脂肪酸的渗漏现象;加速热循环后的封装复合相变材料仍可保持良好的储能性质。     

脂肪酸类二元储能材料的相变特性与配比调节北大核心CSCD

针对单一脂肪酸相变温度固定,与实际需求匹配性差的问题,提出以癸酸(CA)、月桂酸(LA)、十四酸(MA)、软脂酸(PA)和硬脂酸(SA)五种常见的脂肪酸作为相变材料,将其两两复合,利用低共融理论计算10种二元复合体系的最低共融点和理论质量配比,通过熔融共混法制备二元低共融复合体系并在其低共熔点上下3%~6%调节质量配比,借助DSC测试二元低共融复合体系的相变特性。结果表明,二元低共融体系的理论相变温度范围为21.58~53.90℃,理论相变潜热范围为157.64~191.85 J/g,与五种单一脂肪酸的热性能相比,相变温度降低了约10~15℃,相变潜热值无明显变化;制备的10种二元低共融体系的相变温度范围为19.94~56.49℃,与理论相变温度偏差为1.93%~14.72%;相变潜热为125.78~181.45 J/g,与理论相变潜热偏差为0.18%~19.86%;其中CA二元体系的理论相变温度范围为21.58~30.11℃,适用于建筑节能领域;LA二元体系的理论相变温度范围为35.87~41.15℃,适用于电子器件热管理或调温纺织品领域;MA和PA二元体系的理论相变温度范围为46.05~53.9℃,适用于大体积混凝土温控领域;在低共熔点附近调节配比发现最佳配比与理论计算的低共熔配比偏差在4%以内,验证理论计算的准确性和可行性。本研究结果可为脂肪酸类二元复合相变材料的具体使用范围提供技术参考。     

二元有机复合相变材料相变过程热特性实验研究

二元有机复合相变材料因其无腐蚀性、过冷度低、价格低廉和可循环性的优点,在电子器件散热过程中极具发展潜力。通过差示扫描量热法（DSC）测得4种脂肪酸和4种脂肪醇相变温度与潜热,然后利用准共晶相变理论计算脂肪酸/醇二元有机复合相变材料共晶点,确定4种相变温度在33～37 ℃范围内的复合体系,并通过DSC实验测量二元体系相变特性。实验结果表明,筛选出的二元有机复合相变材料相变温度分布在33.08～36.63 ℃,与理论相变温度偏差在0.30%～4.61%;相变潜热分布在138.5～215 kJ·kg^-1,与理论相变潜热偏差在0.4%～27%;十二酸与十八醇复合相变材料具有最高的相变潜热（215 kJ·kg^-1）,相变温度为36.5 ℃。研究结果可为有机复合相变材料在电子器件热管理中的应用提供技术参考。     

N掺杂多孔碳海绵定形芒硝基复合相变材料的制备及其热性能北大核心CSCD

芒硝相变储能材料作为一种潜热值高、来源广泛的无机水合盐,因存在相分层、过冷度等问题,限制了其在储能领域的广泛应用。本工作以N掺杂多孔碳为载体,将芒硝相变储能材料与N掺杂多孔碳复合,解决芒硝相变储能材料在实际应用中存在的问题。基于水热反应在聚氨酯泡沫上负载N原子,随后通过高温碳化得到N掺杂的多孔碳海绵(NPCS-M),并将其作为Na_(2)SO_(4)·10H_(2)O/Na_(2)HPO_(4)·12H_(2)O共晶盐的载体,最终制备出N掺杂多孔碳海绵封装的芒硝基复合相变材料(NPCM)。结果表明:N掺杂多孔碳海绵为蜂窝状结构,N含量为4.3%,比表面积为42.52 m^(2)/g,该材料对共晶盐的吸附量达到了自重的120倍。同时研究了该材料在5~60℃温度范围内循环1000次、3000次和5000次后的固液相变性能,经5000次循环后,该复合相变材料的潜热仍在130 J/g以上,且有降低共晶盐多次循环后过冷度的作用。该N掺杂多孔碳海绵复合相变材料在储能领域具有广阔的应用前景。     

辛酸/月桂酸作为相变蓄冷材料的热性能研究

利用差示扫描量热法和低温显微技术研究辛酸、月桂酸及其二元系统的热性能,建立辛酸/月桂酸二元系统相图。实验结果表明:辛酸/月桂酸二元系统的相图较复杂,辛酸质量分数较低时发生转熔,转熔温度约为14℃,转熔点相应的辛酸质量分数为60%;辛酸质量分数较高时发生共晶,共晶熔融温度为7.44℃,相变潜热为136.43J/g,共晶点相应的辛酸质量分数为80%,该共晶熔融温度适合于空调蓄冷。辛酸/月桂酸共晶混合物经过60次、120次冻熔循环后,其共晶熔融温度、熔融热、比热未发生明显变化,具有较好的热稳定性,可用作相变蓄冷材料。     

Preparation and thermal property of a tetradecane-octanoic acid eutectic phase change material

采用低共熔法研制了一种相变温度在0~3℃的二元有机相变蓄冷材料,该材料由十四烷和正辛酸按一定比例混合组成。首先通过理论计算预测二元最低共熔混合物的比例,确定其理论最低共熔点温度以及潜热值,然后围绕共晶点配制了5种不同比例的混合物。通过差示热量扫描仪、步冷曲线、Hot disk热常数分析仪测量其热物性,并利用高低温交变箱进行循环稳定性实验。当十四烷和正辛酸的摩尔质量比为51：49时,有最低共熔点温度为1.0℃,相变潜热为191.8 J/g,热导率为0.379 W/（m·K）。对其进行100次充放冷实验,循环后相变温度为0.9℃,相变潜热为191.5 J/g,相变蓄冷时间缩短了24.3%,热稳定性良好。实验结果表明,十四烷-正辛酸有机复合相变材料在低温储能中有可观的应用价值。     

纳米Fe2O3/硬脂酸/十八醇纳米复合相变蓄热材料的性能研究

针对有机相变材料热导率低的问题,将高热导率的纳米Fe₂O₃添加到硬脂酸/十八醇二元有机复合蓄热相变材料中,制备纳米复合蓄热相变材料。从分散剂的种类、分散剂与纳米材料的添加量以及超声时间4个方面研究其对纳米复合相变蓄热材料的稳定性及热物性的影响。结果表明,阴离子表面活性剂的分散效果优于阳离子和非离子表面活性剂。复合相变材料中添加质量分数为0.8%,十二烷基苯磺酸钠(SDBS)和质量分数为0.4%Fe₂O₃的体系,超声时间为80 min时,纳米Fe₂O₃在相变材料中的分散效果最好。添加纳米Fe₂O₃后复合蓄热相变材料的相变潜热及相变温度有所下降,热导率提高34.9%。300次热循环复合相变材料的相变温度波动区间不超过0.41℃,相变潜热波动区间不超过4.0%,热稳定性良好。     

Capric-myristic acid/vermiculite composite as form-stable phase change material for thermal energy storage

Phase change materials (PCMs) can be incorporated with building materials to obtain novel form-stable composite PCM which has effective energy storage performance in latent heat thermal energy storage (LHTES) systems. In this study, capric acid (CA)-myristic acid (MA) eutectic mixture/vermiculite (VMT) composite was prepared as a novel form-stable PCM using vacuum impregnation method. The composite PCM was characterized using scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis technique. Thermal properties and thermal reliability of the composite PCM were determined by differential scanning calorimetry (DSC) analysis. The CA-MA eutectic mixture could be retained by 20 wt% into pores of the VMT without melted PCM seepage from the composite and therefore, this mixture was described as form-stable composite PCM. Thermal cycling test showed that the form-stable composite PCM has good thermal reliability and chemical stability although it was subjected to 3000 melting/freezing cycling. Thermal conductivity of the form-stable CA-MA/VMT composite PCM was increased by about 85% by introducing 2 wt% expanded graphite (EG) into the composite. The increase in thermal conductivity was confirmed by comparison of the melting and freezing times of the CA-MA/VMT composite with that of CA-MA/VMT/EG composite. The form-stable PCM including EG can be used as energy absorbing building material such as lightweight aggregate for plaster, concrete compounds, fire stop mortar, and component of interior fill for wallboards or hollow bricks because of its good thermal properties, thermal and chemical reliability and thermal conductivity.     

Synthesis and thermal energy storage characteristics of polystyrene-graft-palmitic acid copolymers as solid-solid phase change materials

A series of polystyrene graft palmitic acid (PA) copolymers as novel polymeric solid-solid phase change materials (PCMs) were synthesized. In solid-solid PCMs, polystyrene is the skeleton and PA is a functional side chain that stores and releases heat during its phase transition process. The heat storage of copolymers is due to phase transition between crystalline and amorphous states of the soft segment PA in copolymer and the hard segment polystyrene restricted the free movement of molecular chains of the soft segments even above the phase transition temperature. The copolymers always remain in the solid state during the phase transition processing and therefore they are described as form-stable PCM. Fourier transform infrared spectroscopy (FT-IR) and polarization optical microscopy (POM) analyses were performed to investigate the chemical structures and crystalline morphology. Thermal energy storage properties, thermal reliability and thermal stability of the PCMs were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) methods. Thermal conductivities of the PCMs were also measured using thermal property analyzer. The analysis results indicated that the PA chains were successfully grafted onto the polystyrene backbone and the copolymers showed typical solid-solid phase transition properties. Moreover, thermal cycling test showed that the copolymers have good thermal reliability and chemical stability although they were subjected to 5000 heating/cooling cycling. The synthesized polystyrene-graft-PA copolymers as novel solid-solid PCMs have considerable potential for such as underfloor heating, thermo-regulated fibers and heating and cooling of agricultural greenhouses. Especially, the polystyrene-graft-PA copolymer including 75% PA is the most attractive PCM due to its highest latent heat storage capacity in the synthesized copolymer PCMs.     

正交各向异性相变材料的无网格法传热模型及应用

利用无网格迦辽金(EFG)法建立正交各向异性相变材料的传热计算模型,基于该模型编程完成各向异性材料太阳能相变蓄热水箱和管壳式相变蓄热单元的相变传热分析,并探讨热导率因子和材料方向角对复合材料相变传热特性的影响.研究表明:在相同节点布置下EFG法的温度场和相界面计算精度均高于有限元法,EFG法在动态相界面追踪方面具有明显...     

Study on preparation and thermal property of binary fatty acid and the binary fatty acids/diatomite composite phase change materials

This study prepared a series of binary phase change materials by mixing decanoic acid, dodecanoic acid, hexadecanoic acid and octadecanoic acid each other. The phase-transition temperature of binary fatty acid and its corresponding mixing proportion are calculated with phase diagram thermodynamic method. The results are verified by the experimental result of the heat absorption curve and the Differential Scanning Calorimetry (DSC) analysis curve. The results show that the calculation method of phase diagram thermodynamic calculation can be taken as a basis for mixing proportion of binary fatty acid phase change materials. In addition, the decanoic–dodecanoic acid/diatomite composite phase change material (PCM) are prepared and its microstructure, thermal property and thermal reliability are characterized. The result shows that the decanoic–dodecanoic acid is uniformly adsorbed into diatomite and the form-stable PCM are formed. The phase-transition temperature and the latent heat of the decanoic–dodecanoic acid/diatomite composite PCMs is 16.74 °C and 66.8114 J/g, respectively.     

光伏相变系统温控特性及散热结构优化设计

针对光伏相变（PV-PCM）热管理系统建立数值模型,与实验结果对比验证模型的有效性。在此基础上,研究24 h内不同复合PCM物性参数（相变温度、膨胀石墨质量分数和厚度）对太阳电池温度的变化规律,利用正交实验法和直观分析法研究最高温度、高于45 ℃与41 ℃的时长和入夜后低于35 ℃的时长的影响。进一步模拟不同类型和数量的散热翅片对太阳电池工作温度的影响,优化PV-PCM系统的散热结构。研究显示,使用内向翅片的散热结构和相变温度为40.2 ℃、膨胀石墨质量分数为15%、厚度为40 mm的复合PCM,可使太阳电池的最高工作温度最小,其值约为42 ℃。     

Phase change material impregnated wood for passive thermal management of timber buildings

The Scots pine (Pinus sylvestris L.) sapwood was impregnated with the eutectic mixture of capric acid (CA) and stearic acid (SA) as phase change material (PCM) via vacuum process for passive thermoregulation in timber buildings. The hygroscopic properties, mechanical properties, thermal energy storage (TES) characteristics and lab-scale thermo-regulative performance of wood/CA-SA composite were evaluated. The produced composite from PCM was morphologically and physico-chemically characterized by SEM, FT-IR and XRD analysis. Thermal energy storage (TES) properties, cycling chemical/thermal reliability, and thermal degradation stability of the produced composite were determined by TG/DTA and DSC analysis. The hygroscopic tests revealed that the wood/CA-SA composite showed low water absorption (WA) and high anti-swelling efficiency (ASE) after 264 hours in water. Wood treatment with CA-SA increased the bending and compression strength of wood. TG/DTA data demonstrated that the wood/CA-SA composite left higher residue of 10.31% at 800°C than that of wood with 6.87%. The DSC measurements showed that the obtained wood/CA-SA composite had a good TES capacity of about 94 J/g at 23.94°C. The cycling DSC results confirmed the eutectic PCM in wood indicated high chemical stability and storage/release reliability even though it was run 600 times melt/freeze. According to thermal performance test, the wood/CA-SA composite has ability of storing excess heat in the environment and preventing the heat flow to the environment. It can be concluded that the fabricated wood/CA-SA composite can be used for indoor temperature regulation and energy saving in timber buildings.     

Influences of expanded graphite on structural morphology and thermal performance of composite phase change materials consisting of fatty acid eutectics and electrospun PA6 nanofibrous mats

In the present work, three fatty acid eutectics of capric acid (CA)–lauric acid (LA), capric acid–palmitic acid (PA), and capric acid–stearic acid (SA) were prepared through melt-blending followed by ultrasonication and were investigated as model phase change materials (PCMs); for comparison, the individual fatty acid of CA was also studied. The DSC measurements indicated that the phase transition temperatures of fatty acid eutectics were lower than those of individual fatty acid of CA. Thereafter, the polyamide 6 (PA6) nanofibers and PA6/EG composite nanofibers with 10 wt.% expanded graphite (EG) were prepared by electrospinning; and then composite PCMs with fatty acid eutectics absorbed in and/or supported by the overlaid mats of electrospun nanofibers (e.g., PA6 and PA6/EG) were explored for storage and retrieval of thermal energy. Influences of the EG on structural morphologies, thermal energy storage properties and thermal energy storage/retrieval rates of composite PCMs were respectively characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and measurement of melting/freezing times. The results indicated that the additions of EG caused the interfaces between fatty acid eutectics and PA6 nanofibrous mats to become more illegible; increased the absorption capacity of fatty acid eutectics within nanofibrous mats. The enthalpies of melting and crystallization of composite PCMs with EG were higher than those of the corresponding composite PCMs without EG, whereas there were no appreciable changes on the phase transition temperatures. The EG improved thermal energy storage/retrieval rates of composite PCMs were also confirmed by comparing the melting/freezing times of CA/PA6/EG and CA–SA/PA6/EG with those of CA/PA6 and CA–SA/PA6, respectively. The results from the SEM observation showed that composite PCMs had no or little variations in shape and surface morphology after heating/cooling processes.