Self‑Assembly of Binderless MXene Aerogel for Multiple‑Scenario and Responsive Phase Change Composites with Ultrahigh Thermal Energy Storage Density and Exceptional Electromagnetic Interference Shielding

The severe dependence of traditional phase change materials(PCMs)on the temperature-response and lattice deficiencies in versatility cannot satisfy demand for using such materials in complex application scenarios.Here,we introduced metal ions to induce the self-assembly of MXene nanosheets and achieve their ordered arrangement by combining suction filtration and rapid freezing.Subsequently,a series of MXene/K^(+)/paraffin wax(PW)phase change composites(PCCs)were obtained via vacuum impregnation in molten PW.The prepared MXene-based PCCs showed versatile applications from macroscale technologies,successfully transforming solar,electric,and magnetic energy into thermal energy stored as latent heat in the PCCs.Moreover,due to the absence of binder in the MXene-based aerogel,MK3@PW exhibits a prime solar-thermal conversion efficiency(98.4%).Notably,MK3@PW can further convert the collected heat energy into electric energy through thermoelectric equipment and realize favorable solar-thermal-electric conversion(producing 206 mV of voltage with light radiation intensity of 200 mw cm^(−2)).An excellent Joule heat performance(reaching 105℃with an input voltage of 2.5 V)and responsive magnetic-thermal conversion behavior(a charging time of 11.8 s can achieve a thermal insulation effect of 285 s)for contactless thermotherapy were also demonstrated by the MK3@PW.Specifically,as a result of the ordered arrangement of MXene nanosheet self-assembly induced by potassium ions,MK3@PW PCC exhibits a higher electromagnetic shielding efficiency value(57.7 dB)than pure MXene aerogel/PW PCC(29.8 dB)with the same MXene mass.This work presents an opportunity for the multi-scene response and practical application of PCMs that satisfy demand of next-generation multifunctional PCCs.

Electrospinning-hot pressing technique for the fabrication of thermal and electrical storage membranes and its applications

The combination of electrospinning and hot pressing,namely the electrospinning-hot pressing technique(EHPT),is an efficient and convenient method for preparing nanofibrous composite materials with good energy storage performance.The emerging composite membrane prepared by EHPT,which exhibits the advantages of large surface area,controllable morphology,and compact structure,has attracted immense attention.In this paper,the conduction mechanism of composite membranes in thermal and electrical energy storage and the performance enhancement method based on the fabrication process of EHPT are systematically discussed.Moreover,the state-of-the-art applications of composite membranes in these two fields are introduced.In particular,in the field of thermal energy storage,EHPT-prepared membranes have longitudinal and transverse nanofibers,which generate unique thermal conductivity pathways;also,these nanofibers offer enough space for the filling of functional materials.Moreover,EHPT-prepared membranes are beneficial in thermal management systems,building energy conservation,and electrical energy storage,e.g.,improving the electrochemical properties of the separators as well as their mechanical and thermal stability.The application of electrospinning-hot pressing membranes on capacitors,lithium-ion batteries(LIBs),fuel cells,sodium-ion batteries(SIBs),and hydrogen bromine flow batteries(HBFBs)still requires examination.In the future,EHPT is expected to make the field more exciting through its own technological breakthroughs or be combined with other technologies to produce intelligent materials.

Effects of Co_(2)O_(3)Addition on Microstructure and Properties of SiC Composite Ceramics for Solar Absorber and Storage

SiC composite ceramics for solar absorber and storage integration are new concentrating solar power materials.SiC composite ceramics for solar absorber and storage integration were fabricated using SiC,black corundum and kaolin as the raw materials,Co_(2)O_(3)as the additive via pressureless graphite-buried sintering method in this study.Influences of Co_(2)O_(3)on the microstructure and properties of SiC composite ceramics for solar absorber and storage integration were studied.The results indicate that sample D2(5wt%Co_(2)O_(3))sintered at 1480℃exhibits optimal performances for 119.91 MPa bending strength,93%solar absorption,981.5 kJ/kg(25-800℃)thermal storage density.The weight gain ratio is 12.58 mg/cm2after 100 h oxidation at 1000℃.The Co_(2)O_(3)can decrease the liquid phase formation temperature and reduce the viscosity of liquid phase during sintering.The liquid with low viscosity not only promotes the elimination of pores to achieve densification,but also increases bending strength,solar absorption,thermal storage density and oxidation resistance.A dense SiO_(2) layer was formed on the surface of SiC after 100 h oxidation at 1000℃,which protects the sample from further oxidation.However,excessive Co_(2)O_(3)will make the microstructure loose,which is disadvantageous to the performances of samples.

Effect of MnO2 on Properties of SiC-mullite Composite Ceramics for Solar Sensible Thermal Storage

For improving the properties of SiC-mullite composite ceramics used for solar sensible thermal storage, MnO2 was introduced as sintering additive when preparing. The composite ceramics were synthesized by using SiC, andalusite, a-Al2O3 as the starting materials with non-contact graphite-buried sintering method. Phase composition and microstructure of the composites were investigated by XRD and SEM, and the effect of MnOz on the properties of SiC composites was studied. Results indicated that samples SM1 with 0.2 wt% MnO2 addition achieved the optimum properties： bending strength of 70.96 MPa, heat capacity of 1.02 J.（g.K）-1, thermal conductivity of 9.05 W-（m.K）-1. Proper addition of MnO2 was found to weaken the volume effect of the composites and improve the thermal shock resistance with an increased rate of 27.84% for bending strength after 30 cycles of thermal shock （air cooling from 1 100 ℃ to RT）. Key words： SiC-mullite composite ceramics; MnO2; solar sensible thermal storage; non-contact graphite-buried sintering; thermal shock resistance

Microstructure and Characterization of Capric-stearic Acid/Modified Expanded Vermiculite Thermal Storage Composites

In order to improve the thermal storage capacity of expanded vermiculite（EV） based formstable composite PCM（FS-PCM） via organic modification of EV, first, EV was modified with a sodium stearate（Na St） as surface modifier, and organic EV（OEV） with hydrophobicity and higher adsorption capacity for fatty acid was obtained. A novel capric-stearic acid eutectic（CA-SA）/OEV FS-PCM with high thermal storage capacity was then developed. OEV and CA-SA/OEV were characterized by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR）, differential scanning calorimetry（DSC）, thermal gravimetry（TG）, and thermal cycling test. Results showed that OEV has obvious hydrophobicity and a higher adsorption capacity for fatty acid. Its adsorption ratio has increased by 48.71% compared with that of EV. CA-SA/OEV possesses high thermal storage density（112.52 J/g）, suitable melting temperature（20.49 ℃）, good chemical compatibility, excellent thermal stability and reliability, indicating great application potential for building energy efficiency. Moreover, organic modification of inorganic matrix may offer novel options for improving its adsorption capacity for organic PCMs and increasing heat storage capacity of corresponding FS-PCMs.

A Novel Layered Double Hydroxide and Dodecyl Alcohol Assisted PCM Composite with High Latent Heat Storage Capacity and Thermal Conductivity

Dodecyl alcohol(DDA) is a promising solid-liquid phase change material(PCM) due to its favorable latent heat storage(LHS) characteristics.However,the leakage issue of PCM in a melted state during the heating period and low thermal conductivity restricts its utilization potential in thermal energy storage(TES) practices.Within the same context,the present work aims to overcome the leakage issue and improve the thermal conductivity of the DDA.With this in mind,a novel leak-proof layered double hydroxide(LDH)/DDA composite PCM is proposed through a solution-based impregnation method.The leak-proof impregnation ratio of the DDA impregnated within the cavities of the synthesized Al/Fe-LDH was determined to be 60%.Detailed morphological,physicochemical,and thermal properties of the fabricated composite were studied by scanning electron microscopy(SEM),Fourier transforms infrared(FTIR) spectroscopy,X-ray diffraction(XRD)spectroscopy,differential scanning calorimetry(DSC),thermalgravimetric analysis(TGA),and thermal cycling study.The results show that the LDH/DDA composite has a suitable phase change temperature(about 20℃) for passive solar thermal management of building envelopes.This composite PCM showed high LHS enthalpy(about136 J/g),good thermal stability,and cycling LHS reliability.It also showed nearly 152% higher thermal conductivity compared to that of pure DDA,ultimately reducing the melting and solidification time of the pure DDA by 44.9% and 45.5%,respectively.

Preparation and Thermal Shock Resistance of Mullite and Corundum Co-bonded SiC Ceramics for Solar Thermal Storage

Mullite and corundum co-bonded SiC-based composite ceramics(SiC-mullite-Al2O3)were prepared by using SiC,calcined bauxite and kaolin via pressureless carbon-buried sintering.The low-cost SiC-based composite ceramics designed in this study are expected to be used as thermal storage materials in solar thermal power generation based on the high density and excellent thermal shock resistance.The influences of calcined bauxite addition and sintering temperature on the microstructures,phase compositions,and physical properties of the samples were investigated.Results demonstrated that the introduction of calcined bauxite containing two bonding phases greatly reduced the lowest sintering temperature to 1400℃.The SiC-mullite Al2O3 composite with 40 wt%calcined bauxite sintered at 1500℃exhibited optimum performance.The density and bending strength were 2.27 g·cm^-3 and 77.05 MPa.The bending strength increased by 24.58%and no cracks were observed after 30 thermal shock cycles,while general clay would reduce the thermal shock resistance of SiC.The SiC-mullite-Al2O3 composites with satisfied performance are expected to be used as thermal storage materials in solar thermal power generation systems.

Preparation and characterizations of heat storage material combining porous metal with molten salt

A new type of heat storage materials combining high temperature molten salts phases change latent heat thermal storage materials, PCM with porous metals sensible heat thermal storage materials was developed. The process was expressed as following: firstly, it is necessary to heat up the molten salts phases change materials to molten; and then the porous metals are put into the molten bath; after being held for 13 h, the composite heat thermal storage materials lumps are taken out of the molten bath and cooled to atmospheric temperature; the last step is to electrodeposit a layer metal coat on the surface of the material lumps. The new type of heat storage material integrates the advantages of both solid sensible heat thermal storage materials and high temperature phases change latent heat thermal storage materials. The metal base heat storage materials enjoy some favorable characteristics such as higher heat charge discharge rate, higher heat storage density and better mechanical strength.

装配式日光温室柔性复合墙体性能测试与分析

为解决装配式日光温室柔性墙体蓄热能力不足的问题,该研究通过在墙体内侧附加蓄热层的方式,设计了一种集蓄热、保温和防水多功能于一体的装配式柔性复合墙体。首先,通过对多种材料进行综合性能评估,筛选出优质的表层材料和保温材料,将其复合制成柔性保温墙体;其次,将水、沙子、相变水凝胶(phase change hydrogel,PCH)作为蓄热层固定在柔性保温墙体内侧,从而形成柔性复合墙体;最后,在4个模型温室中分别对墙体进行性能测试,以未附加蓄热层的柔性保温墙体为对照(CK),分析试验墙体的蓄热和保温性能。单一墙体材料的性能测试结果表明,表层材料中镀铝编织布、黑色淋膜毡抗拉性能好且不透水,断裂强力分别为1.06、0.56 kN,断裂伸长率分别为30.99%、65.91%;保温材料中再生棉、太空棉和空气柱保温效果较好且使用成本低,热阻值分别为0.30、0.50、0.76(m^(2)·℃)/W。柔性复合墙体的性能测试结果表明,所有处理中5 kg/m^(2) PCH柔性复合墙体的蓄热和保温性能最佳,热阻值为2.50(m^(2)·℃)/W,单位面积累计吸热量与放热量分别为1.48、1.13 MJ/m^(2);在典型晴天和阴天条件下,该处理的夜间室内平均温度分别比CK提高了3.08、1.87℃。上述分析结果表明,通过在柔性保温墙体内侧附加相变蓄热层的方式,能够增强墙体的蓄热和保温性能。研究结果可为今后装配式日光温室柔性复合墙体设计及材料选择提供理论依据。

Preparation and Characterization of KNO3/Diatomite Shape-Stabilized Composite Phase Change Material for High Temperature Thermal Energy Storage

A new potassium nitrate （KNO3）]diatomite shape-stabilized composite phase change material （SS- CPCM） was prepared by the mixing and sintering method. KNO3 served as the phase change material （PCM） for thermal energy storage, while diatomite acted as the carrier matrix to provide the structural strength and prevent the leakage of PCM. It was found that KNO3 could be retained 65 wt% into pores and on surfaces of diatomite without the leakage of melted KNO3 from the SS-CPCM. The calculated filling rate of molten KNO3 that could enter into the disc-like shape pore of diatomite verified the scanning elec- tronic microscopy images of SS-CPCM. X-ray diffraction and Fourier transform infrared spectroscopy results showed that no reaction occurred between KNO3 and diatomite, performing good compatibility. Accord- ing to the differential scanning calorimetry results, after 50 thermal cycles, the phase change temperatures for melting and freezing of SS-CPCM with 65 wt% KNO3 were changed from 330.23 ℃ and 332.90 ℃ to 330.11 ℃ and 332.84 ℃ and corresponding latent heats varied from 60.52 J/g and 47.30 J/g to 54.64 J/g and 41.25 J/g, respectively. The KNO3/diatomite SS-CPCM may be considered as a potential storage media in solar power plants for thermal energy storage.

Carbonate-salt-based composite materials for medium- and high-temperature thermal energy storage

This paper discusses composite materials based on inorganic salts for medium- and high-temperature thermal energy storage application. The composites consist of a phase change material （PCM）, a ceramic material, and a high thermal conductivity material. The ceramic material forms a microstructural skeleton for encapsulation of the PCM and structural stability of the composites; the high thermal conductivity material enhances the overall thermal conductivity of the composites. Using a eutectic salt of lithium and sodium carbonates as the PCM, magnesium oxide as the ceramic skeleton, and either graphite flakes or carbon nanotubes as the thermal conductivity enhancer, we produced composites with good physical and chemical stability and high thermal conductivity. We found that the wettability of the molten salt on the ceramic and carbon materials significantly affects the microstructure of the composites.

Fabrication of form stable NaCl-Al2O3 composite for thermal energy storage by cold sintering process

A form stable NaCl-Al2O3(50-50 wt-%)composite material for high temperature thermal energy storage was fabricated by cold sintering process,a process recently applied to the densification of ceramics at low temperature 300℃ under uniaxial pressure in the presence of small amount o f transient liquid.The fabricated composite achieved as high as 98.65% of the theoretical density.The NaCl-Al2O3 composite also retained the chloride salt without leakage after 30 heating-cooling cycles between 750℃-850℃ together with a holding period o f 24h at 850℃.X-ray diffraction measurements indicated congruent solubility o f the alumina in chloride salt,excellent compatibility o f NaCl with Al2O3,and chemical stability at high temperature.Structural analysis by scanning electron microscope also showed limited grain growth,high density,uniform NaCl distribution and clear faceted composite structure without inter-diffusion.The latent heat storage density o f 252.5J/g was obtained from simultaneous thermal analysis.Fracture strength test showed high sintered strength around 5 GPa after 50 min.The composite was found to have fair mass losses due to volatilization.Overall,cold sintering process has the potential to be an efficient,safe and cost-effective strategy for the fabrication of high temperature thermal energy storage materials.

LA-MA/陶粒相变储能材料热物性试验与分析

目的为拓宽相变材料在建筑节能领域中的应用,针对单一相变材料难以满足建筑热工性能要求的问题。方法以十二醇(LA)和十四酸(MA)为复合相变材料、页岩陶粒为载体,制备一种新型相变储能骨料。采用差式扫描量热仪(DSC)、傅里叶红外光谱仪(FT-IR)、热重分析仪(TG)等对相变储能骨料的热物性和不同封装方式下的相变循环稳定性进行分析。结果经复合后相变材料、相变储能骨料的相变温度和相变潜热分别为22.08℃、22.92℃和182.1J/g、22.33J/g。LA-MA复合相变材料和页岩陶粒之间仅存在物理嵌合关系,相变储能骨料在70℃以下未发生物质分解。苯丙乳液封装相变储能骨料在5℃~45℃范围内经历100次相变循环后,质量损失率为0.80%。结论LA-MA/陶粒相变储能骨料的热物性满足建筑节能要求,化学结构稳定,热稳定性好,具有优异的循环耐久性,可应用到建筑围护结构中,研究结论对相变储能材料在建筑围护结构中的应用具有参考价值。

High density polyethylene (HDPE)--Graphite composite manufactured by extrusion:A novel way to fabricate phase change materials for thermal energy storage

Thermal energy storage (TES)has the potential to facilitate the deployment of renewable energy through addressing the demand-supply mismatch,ultimately leading to the decarbonisation of heat supply. Among the TES technologies,latent heat based TES with composite phase change materials (PCMs)has shown great potential,which has attracted significant attention in recent years.However,large scale and reliable manufacturing methods for composite PCMs are still largely lacking.Here,we present a study aimed to develop,for the first time,an extrusion process capable of fabricating high density polyethylene based graphite PCM composites at a high throughput and with enhanced thermal properties.The PCM composites were fabricated under different extrusion process parameters and characterized for their thermo-physical properties by multiple techniques including differential scanning calorimetry,thermal gravitational analyzer,and Fourier transform infrared spectroscopy.The results show that the extrusion process has the potential to fabricate PCM composite bars in a continuous fashion with a manufacturing throughput higher than traditional method;the fabricated PCM composites show enhanced properties (e.g.up to +70% increase in thermal diffusivity);and there is a clear link between extrusion process parameters and PCMs properties.Microstructural analyses show a more homogeneous structure with a lower extrusion speed;whereas a high extrusion speed gives a more microscopically heterogeneous structure with visible graphite agglomerates distributed relatively homogeneous macroscopically;and a higher graphite content gives a larger agglomerate size.The results of this work suggest that the elucidation of composition-process-property relationships is crucial:for a given formulation (composition), only through fine tuning of high throughput manufacturing process can make it possible to achieve the desired performance of the PCM composites.

兼顾碳减排和新能源消纳的火电机组深度调峰与复合储能协调规划

火电机组深度调峰、化学储能以及抽水蓄能是电网灵活性资源的重要组成部分,对三者进行协调规划能在保障电网安全低碳运行的同时,提升新能源的接纳能力。从经济性、碳减排量、弃风弃光量3个方面,构建了火电机组深度调峰和复合储能协调的多目标规划模型;提出了基于熵权的改进非支配排序遗传算法(NSGA-Ⅱ)求解多目标规划模型,获得Pareto最优解集,并进一步根据模糊隶属度得到综合最优解。以某省级电网2025年、2030年的预测数据为例进行仿真验证,结果表明:采用改进NSGA-Ⅱ可提升多目标优化的求解速度与精度;火电机组深度调峰协同储能配置可显著减小弃风弃光率,有利于电力系统的低碳经济运行。

铜铝锌复合金属氧化物导热系数和储热特性研究

铜铝复合金属氧化物储热材料导热系数低,该文通过复合导热相氧化锌提高导热系数,对其导热提升机理和改善后的储热特性进行研究。结果表明:铜铝锌复合金属氧化物Cu_(9)Al_(1)Zn_(3)固体介质连续性提高/孔隙率降低/导热系数提高71%;同时其氧化还原基本可逆,还原/氧化反应时间从Cu_(9)Al_(1)的1.45 min/4.48 min降到1.16 min/2.82 min,循环稳定性高,在200次循环内能够保持98.3%的还原特性和94.2%的氧化特性;成型模块储热试验中Cu_(9)Al_(1)Zn_(3)模块还原/氧化反应时间从Cu_(9)Al_(1)的30.4 min/24.5 min降到20.5 min/22.9 min,反应速率加快,反应时间缩短,能够更快完成储放热响应。

无机水合盐相变储能材料性能优化及应用进展

无机水合盐类相变储能材料因具有储能密度高、无毒、经济等明显优势而受到广泛关注。对无机水合盐的研究有望提高可再生能源的利用效率,缓解能源危机。然而此类材料存在固有缺陷,包括相分离严重、过冷度高、热导率低等,阻碍了其应用。文章以无机水合盐的热物理性质为出发点,详细介绍了无机水合盐类相变储能材料的相变行为、导热性、过冷现象以及相分离等特征。针对其缺陷,总结了近年来性能优化的两大常用策略为与多孔材料复合和微胶囊化,并根据其特性,讨论了无机水合盐在太阳能热能储存和光电转换、建筑节能、储冷等方面的实际应用。

低熔点四元硝酸盐基定型复合相变材料的制备与研究

采用冷压-热烧结方法制备研究了一种形态稳定的硝酸盐基复合相变材料,该材料具有较低的熔点和较宽的温度使用范围,适用于中低温领域的热能储存。研究选取NaNO_(3)-NaNO_(2)-KNO_(2)-LiNO_(3)共晶四元硝酸盐为相变基体材料,氧化镁为结构支撑材料,石墨为导热增强剂,并对其微观结构、化学相容性、热物理性能和循环稳定性进行了一系列表征,结果表明:在烧结前后四元硝酸盐、氧化镁以及石墨之间不发生化学反应,具有良好的化学相容性及化学稳定性。在不同质量比的样品中,四元硝酸盐与氧化镁质量比为6∶4时,为复合材料的最佳配比,且其负载质量分数8%的石墨后,仍表现出优异的结构稳定性;该复合材料的熔点较低,约为70℃,分解温度达到610℃;在50~580℃的温度范围内,具有超过749 kJ/kg的储能密度;添加8%的石墨后复合材料的热导率从0.41 W/(m·K)提高到了0.77 W/(m·K);经150次循环后,复合材料表现出良好的热循环稳定性。这种具有低熔点、宽温域的盐基复合材料是中低温热能存储的有力候选者,本研究为其在中低温领域的应用提供了实践依据。

月桂酸基二元低共融储能材料的制备及热性能

相变材料的潜热储能技术利用于建筑节能领域。以月桂酸(LA)为基础,引入石蜡(PW)和癸酸(CA),研究月桂酸基二元相变材料的热性能、稳定性及可靠性。通过理论预测得到LA-PW、LA-CA的相变温度为35.75℃和18.11℃,通过实验得到LA-PW的最佳比例为76∶24,LA-CA的最佳比例为30∶70。LA-PW、LA-CA的相变温度分别为37.45℃和17.82℃,与理论值相差1.70℃、0.29℃,相变潜热分别为186.9J/g、129.16J/g。FTIR和XRD分析发现LA-PW、LA-CA都没产生新物质,为纯物理结合且在蓄放热实验过程中表现出良好的储热性能。热重分析可以看出在100℃内,LA-PW、LA-CA都没有发生热解现象,表现出良好的热可靠性。经过500次冷热循环后LA-PW、LA-CA的相变温度最大差率分别为9.5%、2.15%,相变潜热最大差率分别为3.8%、3.27%,能保持较好的稳定性和蓄热性能,适用于建筑行业的节能研究应用。

应用于太阳能储热的膨胀石墨/石蜡复合相变材料的制备与热性能

为了改善太阳能储热用相变材料的性能,以石蜡为基材,通过添加分散剂和不同质量分数的膨胀石墨,制备出具有良好热性能的复合相变材料。实验测试复合相变材料在熔化和凝固过程的温度变化,分析复合相变材料的蓄放热特性,并采用参比温度法得出复合相变材料的主要热物性参数。数值模拟复合相变材料的熔化过程,比较分析温度的模拟值与实验数据,研究复合相变材料的固液相变化规律和微观流场。结果表明:添加膨胀石墨可增强相变材料的传热,提高相变材料的蓄、放热性能,添加1.5%膨胀石墨的相变材料的热传导率是纯相变材料的1.49倍;随着膨胀石墨的添加量增加,复合相变材料黏度增大,使对流换热强度减弱,同时复合相变材料的潜热也逐渐降低,使蓄热量减小;膨胀石墨添加量(质量分数)为1.0%的复合相变材料蓄放热性能最佳,放热时间比纯相变材料缩短38.06%;膨胀石墨的添加量越高,复合相变材料的熔化速率越快;膨胀石墨添加量为1%的复合相变材料蓄放热性能最佳。