活性炭/有机质复合相变材料的热-电性能

用活性炭(AC)作为支撑材料,石蜡(PW)、十六酸(PA)和硬脂酸(SA)作为相变主材,通过熔融共混法制备AC/PW、AC/PA和AC/SA复合相变材料,并考察了其热-电性能。结果表明,添加活性炭时有机质均不会泄漏;复合材料充-放热过程中温度场分布都比较均匀,热循环会使材料导热性能略有下降;此外,三种复合材料的电阻率均随压力增加而减小。     

石蜡/膨胀石墨/石墨烯复合相变储热材料的制备及性能

以石蜡(PA)作为相变储热材料、 膨胀石墨(EG)作为主导热材料和支撑材料, 石墨烯气凝胶(GA)作为导热增强材料和辅支撑材料制备了PA/EG/GA复合相变材料, 研究了GA添加量对复合相变材料相变温度、 相变潜热、 导热性能以及循环稳定性的影响. 结果表明, 所制备的80%PA-17%EG-3%GA复合相变材料导热性能良好, 循环稳定性出色. 与80%PA-20%EG复合材料相比, 该材料的相变温度、 相变潜热以及循环稳定性无明显变化, 但导热系数由4.089 W/(m·K)提升到了5.336 W/(m·K), 显示出良好的应用前景.     

石蜡/碱改性硅藻土/膨胀石墨复合相变储热材料的制备及性能

通过碱处理,优化了硅藻土(DIA)的孔隙结构,提高了孔隙率,增加了石蜡(paraffin)负载量。通过直接浸渍法制备了新型性状稳定的石蜡/碱改性DIA/膨胀石墨(EG-alDIAP)复合材料,并研究了其结构与性能的关系。结果表明,复合相变材料的石蜡负载量从47.4%提高到了61.1%,进而提高了复合材料的储热性能;向改性DIA中添加膨胀石墨(EG)提高了复合材料的传热能力,添加质量分数10%EG时导热系数提高了113%(从0.276 W·m^-1·K^-1提高到了0.589 W·m^-1·K^-1)。随着EG含量的升高,复合相变材料的相变潜热有所增加,但化学相容性、稳定性等无明显变化。含10%EG的石蜡/碱改性DIA复合材料具有可靠的储能性能、良好的温度调节性能和蓄放热能力。     

石蜡/碱改性硅藻土/膨胀石墨复合相变储热材料的制备及性能

通过碱处理,优化了硅藻土(DIA)的孔隙结构,提高了孔隙率,增加了石蜡(paraffin)负载量。通过直接浸渍法制备了新型性状稳定的石蜡/碱改性DIA/膨胀石墨(EG-alDIAP)复合材料,并研究了其结构与性能的关系。结果表明,复合相变材料的石蜡负载量从47.4%提高到了61.1%,进而提高了复合材料的储热性能;向改性DIA中添加膨胀石墨(EG)提高了复合材料的传热能力,添加质量分数10%EG时导热系数提高了113%(从0.276 W·m^-1·K^-1提高到了0.589 W·m^-1·K^-1)。随着EG含量的升高,复合相变材料的相变潜热有所增加,但化学相容性、稳定性等无明显变化。含 10%EG的石蜡/碱改性 DIA复合材料具有可靠的储能性能、良好的温度调节性能和蓄放热能力。     

还原氧化石墨烯改性少层剥离石墨增强石墨基钾离子电池负极稳定性

钾在石墨中嵌入电位较低,因此石墨负极可使钾离子电池具有较高的能量密度,是一种理想的钾离子电池负极材料。然而,石墨嵌钾后的体积膨胀率高达60%,导致钾离子电池的循环稳定性较差。此外,钾嵌入石墨层间的动力学过程缓慢,制约了钾离子电池倍率性能的提升。在本工作中,我们用还原氧化石墨烯(rGO)包覆剥离石墨(EG),得到一种具有协同效应的层状复合材料。一方面,以少层的EG代替石墨可以减少由于钾的嵌入/脱嵌所引起的体积膨胀和内部应力;另一方面,外层rGO可以避免EG的堆叠,这有利于加速动力学过程并在钾化/去钾化过程中稳定结构。当复合材料所用EG和GO的质量比为1 : 1时,其性能达到最优,在50 mA·g^-1的电流密度下能够提供443 mAh·g^-1的比容量;在电流密度为800 mA·g^-1时,比容量为190 mAh·g^-1,保持率为42.9%。相同测试条件下,纯EG和rGO的容量保持率仅为14.2%和27.2%。测试结果说明EG-1/rGO-1复合材料在比容量和倍率性能两个方面得到了提升。     

导热膨胀石墨/聚醚酰亚胺复合材料的制备与性能

利用膨胀石墨(EG)经高温处理后比表面积大的特点, 以膨胀石墨作为导热填料, 通过球磨和热模压方法制备了膨胀石墨/聚醚酰亚胺(PEI)导热复合材料, 并对其加工过程、 微观形貌、 热性能和导热性能进行了研究. 结果表明, 球磨处理可以打破膨胀石墨的“泡沫”状态并减少石墨纳米片间的间隙, 热压可以诱使和促进石墨纳米片沿着水平方向排列和取向, 从而显著提升了复合材料的平面内导热性能. 当膨胀石墨在复合材料中的质量分数为20%时, EG/PEI复合材料的面内导热系数为2.38 W?m^?1?K^?1. 与PEI相比, 复合材料导热系数的增幅约为12倍. 所制备的EG/PEI复合材料均具有良好的散热能力、 较好的热稳定性和较高的储能模量, 是一种综合性能优异的导热材料.     

膨胀石墨/聚苯胺/Fe_3O_4复合材料的制备及吸波性能

采用原位聚合方法制备了膨胀石墨/聚苯胺(EG/PANI)复合材料,将Fe_3O_4负载于EG/PANI表面,得到具有电磁吸收性能的EG/PANI/Fe_3O_4复合材料.通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)及矢量网络分析仪(VNA)等对复合材料的形貌、成分和吸波性能进行了研究.吸波性能分析结果表明,当掺杂浓度为0.05 mol/L,匹配厚度d=2 mm时,样品的最小反射损耗(RLmin)在8.64 GHz处达到-37 dB.随着掺杂浓度的增加,最小反射损耗峰向低频移动,对应的匹配厚度逐渐变厚.材料的介电弛豫极化、涡流损耗及λ/4模型的干涉相消现象出现的双峰,使EG/PANI/Fe_3O_4复合材料在电磁波吸收领域有一定的应用前景.     

聚乙二醇/氮化硼复合材料相变导热性能及其结晶行为

本文采用熔融共混浇筑的方法制备了聚乙二醇/氮化硼(PEG/BN)相变复合材料,并研究了不同尺度片状BN对相变复合材料导热性能和结晶行为的影响。 通过扫描电子显微镜(SEM)、热常数分析仪、红外热成像分析仪和差示扫描量热仪(DSC)研究了相变复合材料的微观形貌、导热系数和相变过程,并利用莫志深法对DSC结果进行了非等温结晶动力学分析。 结果表明,较大片状直径(50 μm)的BN可以更有效地提高聚乙二醇的导热系数,当BN填料质量分数为40%时,相变复合材料的导热系数可达到5.04 W/(m·K)。 在快速降温条件下,片径为50 μm的BN填料可以缩短PEG的半结晶时间,提高结晶速率,使相变复合材料具有较大的相变焓。     

导热增强聚乙二醇相变复合材料的制备及其性能

本文以聚乙二醇(PEG)为相变材料,通过添加不同的无机填料,采用熔融共混浇筑方式制备了导热增强型相变复合材料。 通过扫描电子显微镜(SEM)、热常数分析仪、差示扫描量热仪(DSC)、红外热成像和热重分析仪研究了所制备复合材料的微观结构、导热性能与相变过程。 研究结果表明,相比于碳酸钙和氧化铝,在相同添加含量下,氮化硼(BN)可有效提高PEG的导热系数,当BN质量分数为40%时,导热系数可达到3.40 W/(m·K);当填料添加量相同时,片状BN和不规则纳米碳酸钙(CaCO₃)比球形氧化铝(Al₂O₃)对PEG具有更加优良的定型效果,在相变过程中,能够更加有效阻隔PEG的流动,保持复合材料的形状稳定性。     

PP/EVA/OMMT纳米复合材料及其阻燃材料的动态燃烧行为

利用锥形量热仪(CONE)在35kW/m2热辐照条件下,并结合极限氧指数(LOI)和UL-94垂直燃烧测试方法对聚丙烯(PP)/乙烯-醋酸乙烯酯共聚物(EVA)/有机蒙脱土(OMMT)纳米复合材料和加入无卤复配阻燃剂制备的PP/EVA/OMMT/氢氧化铝(ATH)/三氧化二锑(AO)纳米复合阻燃材料的热释放速率、烟释放及材料在燃烧时的质量损失行为进行了研究。结果表明,添加5%(质量分数)OMMT可以提高PP/EVA复合材料的阻燃性能,燃烧时的热释放速率、质量损失率以及烟释放量减少,且OMMT与无卤复配阻燃剂之间可产生阻燃协同作用,使纳米复合阻燃材料的阻燃性能、热稳定性和抑烟性进一步增强。     

Preparation and thermal properties of palmitic acid/expanded graphite/carbon fiber composite phase change materials for thermal energy storage

Using palmitic acid (PA), expanded graphite (EG), and carbon fiber (CF) as raw materials, PA/EG/CF composite phase change materials (CPCMs) with diverse CF contents were invented by melt blending approach. The effects of different ratios on thermal properties were studied by experimental characterization and testing. Scanning electron microscopy images displayed that PA was adsorbed in the pores of the EG surface, while CF was disorderly but uniformly embedded in the interior and surface of pores. The chemical stability and thermal decomposition stability of CPCM at low temperature were proved by Fourier transform infrared spectrometer and thermogravimetric analyzer results, respectively. According to the law of heat storage/release time and latent heat variation, the optimal ratio scheme was determined, and its heat storage/release time was 65% and 59% lower than pure PA, respectively. The form-stable materials were prepared by compression forming method, and thermal cycling experiment results demonstrated that the higher the content of CF, the stronger the inhibition of mass loss. Based on the experimental results, the PA/EG/CF CPCM has the advantages of stable phase transition, strong stability, and fast heat storage and release rate, so it has a marvelous application prospect in the field of low-temperature heat storage engineering.

     

Characterization of form-stable phase-change material for solar photovoltaic cooling

Solar PV panel cooling is essential to achieve maximum efficiency of PV modules. Phase-change material (PCM) is one of the prominent options to cool the panel and reduce the temperature, since PCMs have low thermal conductivity. Expanded graphite particles are used to enrich the structure and stability as well as to increase the thermal properties. In the present research work, polyethylene glycol (PEG) 1000 is used as a base material and expanded graphite for inclusive particle. A novel form-stable PEG1000/EG composite PCM mixture is prepared, using impregnation and dispersion method. Expanded graphite and PEG1000/EG sample phase compositions are investigated, using X-ray diffraction technique. No new peak is identified in the composite PCM sample. The surface morphology and structure of EG and PEG1000/EG are investigated, using scanning electron microscopy (SEM). Chemical stability analysis is done by Fourier-transform infrared spectroscopy. Thermal properties of the prepared composite PCMs are analysed by differential scanning calorimetry, thermogravimetric analysis (TGA) and KD2 pro analyser. Results show that addition of EG in various propositions (5%, 10% and 15%) enhances the thermal conductivity of PCM samples from 0.3654 to 1.7866 W mK^?1, while melting point and latent heat of fusion of PCM samples are getting reduced. TGA thermographs are used to investigate the thermal stability of the composite PCM samples. TGA curves show that loss of mass happens above the operating temperature, and it is varied with different mass ratios of EG. Characterization of the prepared composite PCM samples is compared and found that PEG1000-85%/EG-15% is the best form-stable PCM, suitable for cooling the solar PV panel as well as to improve the electrical efficiency coupled with a decrease of temperature in the range of 35 °C to 40 °C.

     

Preparation and thermal properties of expanded graphite/paraffin/organic montmorillonite composite phase change material

Expanded graphite (EG)/paraffin/organic montmorillonite (OMMT) composite phase change material (PCM) was prepared by using melt intercalation method. The microstructure of EG/paraffin/OMMT is observed by scanning electron microscope (SEM). The thermal properties are investigated by differential scanning calorimetry (DSC). The mass loss of EG/paraffin/OMMT after 50 heating cycles was measured for investigating the influence of EG and OMMT on the thermal properties of paraffin. The results show that EG and OMMT have the ability of adsorption and shape-stability. The melting point EG/paraffin/OMMT is decreased slightly with an addition of paraffin and the latent heat of EG/paraffin/OMMT is determined by the mass ratio of paraffin. The heat transfer efficiency of EG/paraffin/OMMT is strengthened and the heating time is decreased to one-sixth of that of paraffin by addition of EG and OMMT. The thermal stability of EG/paraffin/OMMT is improved by addition of OMMT.     

Synthesis of the polyethylene glycol solid-solid phase change materials with a functionalized graphene oxide for thermal energy storage

Polyethylene glycol (PEG) as a phase change material possesses three obstacles, such as leakage, low thermal conductivity and low thermal stability. A novel solid-solid phase change material (PCM) based on functionalized graphene oxide (GO), Polyethylene glycol (PEG) was prepared, and the three obstacles of PEG as a PCM was solved in one and the same material. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman and Transmission electron microscope (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and thermogravimetric analysis/infrared spectrometry (TG-IR) were used to study the properties of supporting material and composite PCM (CPCM). The results indicated that the PEG was grafted on the surface of the supporting material; Compared with pure PEG, the latent heat of CPCM with 9.6 wt% supporting material decreased only 5.3%, however, the thermal conductivity of CPCM increased 111% and the heat peak release rate of CPCM decreased 33.4%.     

Thermal-Conductivity-Enhancing Copper-Plated Expanded Graphite/Paraffin Composite for Highly Stable Phase-Change Materials

Paraffin (PA)/expanded graphite (EG) is an important composite phase change material with low cost, high heat storage, good thermal conductivity and cycling stability. Its thermal conductivity needs to be further improved for application in the thermal management system of power lithium-ion batteries. In this paper, copper plated expanded graphite (CPEG) with 3D porous structure was prepared by electroless copper plating method, which was used as thermal conductivity enhancing material to replace part of EG in PA/EG composite materials. For the optimized phase change material composed of 80 %PA-14 %EG-6 %CPEG, the copper content is very low (0.768 wt %), but its thermal conductivity can be significantly improved without loss of latent heat and thermal cycling stability. Its thermal conductivity is increased from 11 times to 16.5 times that of paraffin while compared with the copper-free composite material (80 %PA-20 %EG). The PA/EG/CPEG composite material exhibits good temperature control effect on power lithium-ion batteries.     

添加共试剂改善聚酰胺复合反渗透膜的性能

将N,N′-二甲基乙酰胺(DMAc)作为共试剂添加在间苯二胺水溶液中参与界面聚合反应, 以改善聚酰胺复合反渗透膜(PA-RO-x, x代表添加DMAc的质量分数)的性能. X射线光电子能谱(XPS)和衰减全反射傅里叶红外光谱(ATR-FTIR)分析表明, 随着DMAc含量的增加, 复合膜结构中交联聚酰胺含量相对于线性羧基部分有所增加; 场发射扫描电子显微镜(FE-SEM)和原子力显微镜(AFM)表征结果显示, 随着DMAc含量的增加, 膜表面的粗糙程度逐渐增大; 静态水接触角测试结果表明, 添加DMAc后, 膜的亲水性增强. 结合上述测试结果发现, 添加DMAc可以有效降低水油两相的不相溶性, 提高水相中间苯二胺向正己烷中扩散的速率, 这有助于加快间苯二胺与均苯三甲酰氯反应; 同时, 聚酰胺结构中交联酰胺含量的增加可以提供更多的氢键位点, 有助于水分子快速渗透通过复合膜而不损失截盐率; 膜表面的粗糙程度变大, 有助于提高水通量. 在2 g/L的氯化钠溶液和1.6 MPa测试压力条件下, PA-RO-5.2(DMAc添加质量分数为5.2%)的渗透通量和截盐率分别为66.1 L/(m²·h)和98.7%, 与未添加DMAc的聚酰胺复合反渗透膜相比, 通量增加115%, 截盐率仅下降0.9%.