To overcome efficiency limitations in traditional thermal energy storage, a multifunctional magnetic carbon sponge composite phase change materials was developed for efficient thermal energy storage and multi-mode energy conversion. The material features a hierarchical 3D porous structure that enables a high eutectic hydrated salt loading of 94 %. The composite exhibits significantly enhanced thermal conductivity (1.881 W & sdot; m- 1 & sdot; K-1), high phase change enthalpy (239.9 J/g melting, 222.4 J/g crystallization), and excellent cyclic stability, retaining 87.5 % of its initial enthalpy after 1,000 thermal cycles. Incorporated superparamagnetic Fe3O4 nanoparticles enhance magnetothermal conversion, enabling rapid heating to 90 degrees C under an alternating magnetic field. Combined with polydopamine modification and the sponge's light-trapping effect, the composite achieves a high photothermal conversion efficiency of 95.17 %. When utilized in temperature-driven thermoelectric conversion devices, this material achieves a measured output current of 0.619 mA and a generated voltage of 67.95 mV, confirming its capability for thermoelectric conversion and sustained power generation. Because of its exceptional thermal conduction, significant phase transition enthalpy, exceptional cyclic stability, and capacity to function under dual stimuli (optical and magnetic fields), this composite shows lots of promise for use in multipurpose thermal energy management systems.

As a crucial component in phase change heat storage systems, phase change materials have demonstrated remarkable application potential across diverse fields, such as solar energy storage systems, magnetic induction energy conversion, and storage. This research reports a high-performance photomagnetically driven composite phase change materials. The photomagnetic response unit was fabricated via the hydrothermal coprecipitation method by in-situ loading of Fe3O4 nanoparticles onto carbon nanotubes (CNTs@Fe3O4). Subsequently, it was integrated with the Na2SO4.10H2O-Na2HPO4.12H2O eutectic salt to synthesize the composite PCM heat storage material.Experimental findings indicate that the composite incorporating 2.5 % CNTs@Fe3O4 exhibits nearly zero subcooling (Delta T = 0.1 degrees C), a thermal conductivity as high as 1.0230 W/(m.K), a significant latent heat of phase transformation (melting enthalpy of 253 J/g and solidification enthalpy of 218 J/g), and an enthalpy retention rate of 94.8 % after 1000 thermal cycles. The Fe3O4 endows the material with excellent magneto- thermal conversion performance. Specifically, at a 2.5 % doping content, the temperature increase within 240 s in an alternating magnetic field can reach 67.2 degrees C through the Neel/Brownian relaxation mechanism. Additionally, the CNTs carrier enhances the photothermal conversion efficiency to 94.5 %. This material combines high thermal conductivity, cycle stability, and dual-field (optical/magnetic) driven heat storage capabilities, thus demonstrating significant application potential in multifunctional thermal energy storage.

Hydrated salt phase-change materials (PCMs) are difficult to widely use because of their problems, such as supercooling, phase separation, low thermal conductivity and loss of crystal water due to cyclic stability. In this paper, MCTs-Na2SO4·10H2O/Na₂HPO₄·12H₂O-based phase-change materials were prepared using hydrogen peroxide-modified functional groups of cross-linked carbon tubes surfaces (MCTs) to improve the overall properties of the materials. The results show that after modification, microporous cross-linked carbon tubes' surface and channel structure show wrinkled and rough texture and are rich in hydrophilic functional groups, which is conducive to loading more phase-change energy storage materials. Based on the relationship between PCMs and MCTs, the thermal conductivity of carbon-based type phase-change energy storage material is predicted and compared with the actual test value. After 1000 solid–liquid phase cyclic tests, the latent heat loss of PCMs-0 was 14.50

The increasing challenges of energy scarcity and environmental pollution caused by non-renewable sources highlight the critical importance of phase change energy storage materials in improving energy conversion and utilization efficiency. Because of the drawbacks of single function and poor thermal stability of hydrated salt phase change materials, this study employs interfacial polymerization introducing the magnetic graphene oxide (MGO) to successfully prepare the magnetic phase change microcapsule composed of eutectic hydrated salt (EHS) as the nucleus and SiO2 as the shell, with the functions of magnetic/light-to-thermal conversion. Through the optimization of the preparation process, the enthalpies of melting of the microcapsules reached 161.3 J.g-1, and the micromorphology was uniform and complete when tetraethyl orthosilicate (TEOS) of 8 mL and deionized water of 10 mL was added. The study showed that the SiO2 shell effectively suppressed the water loss of the core material and improved the thermal stability; the introduction of MGO increased the thermal conductivity of the microcapsules by up to 82 % and gave it the functions of magnetic/light-to-thermal conversion. Under a constant alternating magnetic field, the temperature of the microcapsules with 0.15 g of MGO was increased to 35 degrees C, and its photothermal conversion efficiency reached 90.7 % under the optical density of 860 mW.cm-2.

Lamellar hydrates of CAC were designed with the introduction of Mg -Al hydrotalcite (M -A -H), and the effects on the early setting behavior, demolding strength, pore structures, mechanical properties, and fracture behavior of alumina-spinel castables were investigated. The results showed that Mg -Al hydrotalcite stimulated rapidly the hydration of CAC and the formation of lamellar C2AH8 and C4AcH11 when curing at 25 and 40 degrees C. In comparison, CAH10 and C2AH8 were detected without M -A -H and were transformed completely into C3AH6 at 40 degrees C. The formation of lamellar C2AH8 and C4AcH11 would contribute to a more complicated pore structure, especially in the range of 1-10 mu m. Meanwhile, the incorporation of MgO from M -A -H also regulates the distribution of CA6 and spinel (pre -formed and in -situ). Consequently, the optimized microstructure and complicated pore structure can induce the deflection and bridging of cracks, thus facilitating the consumption of fracture energy when testing at 1400 degrees C.

水氯镁石是一种非常具有应用前景的镁盐资源,其储量丰富,成本低廉.以青海盐湖水氯镁石和水玻璃合成不同MgO/SiO2摩尔比(0.5:1,1:1,1.5:1)的水合硅酸镁(M-S-H)凝胶,采用XRD、SEM、红外和核磁共振等测试手段研究M-S-H的合成机理和结构特征,进而将合成的M-S-H与硅微粉复合制备镁质浇注料,探究M-S-H结构对浇注料结合特性的影响规律.结果表明:不同MgO/SiO2摩尔比的M-S-H呈层状堆叠结构,MgO/SiO2摩尔比为1:1时M-S-H的层间自由水少,结晶度最高;M-S-H替代部分硅微粉制备镁质浇注料能显著提高1550℃热处理后浇注料的力学性能,其中MgO/SiO2摩尔比为1:1的M-S-H复合硅微粉制备的镁质浇注料综合性能最佳,与添加6％(质量分数)硅微粉制备的镁质浇注料相比,其常温抗折强度和高温抗折强度分别提高75％和8％.

水合硅酸镁是炼钢连铸过程中间包用镁质浇注料的重要结合相,其含量多少决定着浇注料的强度大小.本工作以Na2SiO3·9H2O和MgCl2·6H2O为原料,采用水热法合成水合硅酸镁(MgO-SiO2-H2O,M-S-H),研究了焙烧温度和焙烧次数对水合硅酸镁的"结构记忆"特性;随后将预合成M-S-H复合硅微粉制备镁质浇注料,研究其对镁质浇注料性能的影响.结果表明:当焙烧温度低于400℃时,水合硅酸镁具有"结构记忆"特性,焙烧次数增加有利于M-S-H凝胶中层间羟基的插入,促进其层状结构晶粒的长大和结构稳定性的提高;在镁质浇注料制备过程中引入一定量的预合成水合硅酸镁和少量的硅微粉,使浇注料具有很好的施工性能和足够的早期结合强度;同时减少了高温热处理后浇注料缺陷形成,提高了材料力学性能,为开发低硅微粉镁质浇注料提供支撑.

MgO-bonded castables are one of the promising non-cement bonded refractories used for ladle lining. To make crack-free MgO bonded castables, the formation of layered double hydroxides (Mg-Al hydrotalcite) is proposed. In the present work, the influences of Al(OH)3 and hydratable alumina (p-Al2O3) and different curing temper-atures (40 degrees C, 60 degrees C, 80 degrees C) on the formation of hydrotalcite are investigated. The hydration behavior and corresponding hydrates are examined using electrical conductivity, XRD, SEM, FTIR, and TG-DSC analyses. The results show that the increase in curing temperature is more conducive to the formation of hydrotalcite, where p-Al2O3 significantly promotes the formation due to the enhanced reactions between intermediates of Mg(OH)2 and Al(OH)3. After high-temperature treatment, the decomposition of a larger amount of hydrotalcite and Al (OH)3 and thereafter growth of microcrystalline spinel contribute to refined pore size distribution. Consequently, a higher hydration degree of p-Al2O3 and the formation of more hydrotalcite provide a higher bonding strength at room temperature, and the optimized microstructure enhances high-temperature strengths.

为提升水合盐相变材料的性能,以Na2SO4·10H2O-Na2HPO4·12H2O共晶盐(EHS)作为基体材料,采用HF/HNO3刻蚀法制备亲水性纳米碳化硅(Nano-SiC),并以 Na2SiO3·9H2O 和改性 Nano-SiC 作为复合添加剂制备复合纳米相变流体材料(Nano-SiC EHS PCMs).结果表明:改性后Nano-SiC在EHS PCMS中具有良好的分散稳定性,同时Na2SiO3·9H2O和Nano-SiC协同作用下使得EHS PCMs过冷度降低到0.3℃,无相分层现象.Nano-SiC EHS PCMs在固液相变体系中热导率均有提升,同时添加0.2%(质量分数)Nano-SiC后EHS PCMS储能时间缩短了21.8%.添加质量分数为0.15%Nano-SiC的EHS PCMs熔融焓和结晶焓分别为267.3 J/g和231.4 J/g,经过1000次冷热循环后焓值变化甚小,该体系具有良好的循环稳定性.

In this paper, carbon particles with micro- and nano-particle size were synthesized through a hydrothermal reaction of glucose, namely C-1(123.1 nm), C-2(229.2 nm), C-3(335.1 nm), C-4(456.2 nm) and C-5(534.0 nm) with distinct sizes. We utilized five size carbon particles as individual fillers into the EHS matrix materials to prepare composite eutectic phase change materials (C/EHS PCMs) by melt blending technique. The impact of carbon particle size on the dispersion stability and thermal properties of Na 2 SO[Formula: see text]10H 2 O–Na 2 HPO[Formula: see text]12H 2 O (EHS) phase change materials was investigated. Scanning electron microscopy (SEM) and dynamic light scattering (DLS) analysis were done to analyze the diameters of carbon particles. The cryogenic-scanning electron microscopy (Cryo-SEM) analysis indicated that the carbon particles resulted in modification in the morphology of the EHS. The results of in situ X-ray diffraction (XRD) and Fourier-transformed infrared (FTIR) analysis showed only simple physical mixing between carbon particles and EHS. It is shown that adding 0.2 wt.% C-2 can decrease the supercooling degree of EHS to 1.5[Formula: see text]C. The cyclic stability of C/EHS varies significantly depending on the size of carbon particles. The thermal conductivity of EHS increased by 42.1%, 39.9%, 14.4%, 19.5%, and 18.8% with the addition of C-1, C-2, C-3, C-4, and C-5, respectively, at a mass fraction of 0.2%. The results of differential scanning calorimetry reveal that the incorporation of C-1, C-2, C-3, and C-4 into EHS leads to an enhancement of latent heat. The latent heat capacity of EHS with 0.2 wt.% C-2 is 243.4 J⋅g[Formula: see text], and after undergoing 500 cycles of solid-liquid phase transition, the latent heat remained above 200 J⋅g[Formula: see text]. Through the comprehensive analysis, the C-2/EHS composite phase change material holds significant potential for advancing building insulation and solar energy storage technologies.

In this paper, carbon particles with micro- and nano- particle size were synthesized through a hydrothermal reaction of glucose, namely C-1(123.1 nm), C-2(229.2 nm), C-3(335.1 nm), C-4(456.2 nm) and C-5(534.0 nm) with distinct sizes. We utilized five size carbon particles as individual fillers into the EHS matrix materials to prepare composite eutectic phase change materials (C/EHS PCMs) by melt blending technique. The impact of carbon particle size on the dispersion stability and thermal properties of Na2SO4·10H2O-Na2HPO4·12H2O (EHS) phase change materials was investigated. It is shown that adding 0.2wt% C-2 can decrease the supercooling degree of EHS to 1.5 C. The cyclic stability of C/EHS varies significantly depending on the size of carbon particles. The results of differential scanning calorimetry reveal that the incorporation of C-1, C-2, C-3, and C-4 into EHS lead to an enhancement of latent heat. The latent heat capacity of EHS with 0.2wt% C-2 is 243.4 J·g-1, and after undergoing 500 cycles of solid-liquid phase transition, the latent heat remained above 200 J·g-1. The C-2/EHS composite phase change material holds significant potential for advancing building insulation and solar energy storage technologies.

The effects of C-coated Cu nanoparticles on the rheological behavior of mirabilite phase change nanofluids with different mass fraction(1.0% ,1.5% ,2.0% ,3.5% ,and 5.0% )at different temperatures were investigated.The viscosity of C-coated Cu nanoparticles phase change nanofluids was investigated at different shear rates(39.91～140 s-1)and different temperatures(35～50℃ ).The results show that the hydrothermal method successfully prepares C-coated Cu nanoparticles.Nanofluid samples with mass fraction of 1.0% C-coated Cu nanoparticles at 35℃ and 1.5% C-coated Cu nanoparticles at 35,40℃ exhibit Newtonian fluid behavior,but nanofluid samples exhibit non-Newtonian fluid behavior at other temperatures.When the mass fraction of C-coated Cu nanoparticles increases to 2.0% ,3.5% and 5.0% ,the samples exhibit non-Newtonian fluid behavior,which conforms to the power law model.At the same time,the thermal properties of mirabilite composite phase change energy storage materials were studied.The composite phase change nanofluid has higher thermal conductivity,lower undercooling,and better cycle stability.

Exploring cost-effective and stable electrocatalysts for the oxygen evolution reaction (OER) is of great importance to converting renewable electricity into fuels. Herein, we demonstrate the preparation of phytic acid-iron complex (PAFe) decorated Co3O4/Ni(OH)2 core-shell heterojunction using a hydrothermal-sol-vothermal combined with the typical coordination chemistry technique. The Co3O4 nanowires increase the electrical conductivity and inhibit the agglomeration of Ni(OH)2 nanosheets. The core-shell structure with a tightly contacted interface can regulate the interfacial electronic structure and enhance electron transfer ability. More importantly, the leach of PA under OER operation benefits the dissolution and re-adsorption of Fe species on the surface of the catalyst. The formed amorphous and active multi-metallic oxyhydroxides accelerate the catalytic reaction kinetics. As a result, the Co3O4/Ni(OH)2 @PAFe exhibits excellent OER performance with a low overpotential of 230 mV at 10 mA cm-2 (reduced by 84 mV compared with that of the original Ni(OH)2), a small Tafel slope of 43 mV dec-1, and prominent long-term durability. This research offers a new sight to enhance the catalytic performance of hydroxides and makes for future energy storage and conversion systems.(c) 2022 Elsevier B.V. All rights reserved.

在复合相变材料中引入碳纳米纤维(CNFs)提高相变体系的导热系数,以实现相变材料与外界环境进行快速有效的热量交换.本文采用熔融共混法将Na2 SO4·10H2 O和Na2 HPO4·12H2 O制备成共晶盐相变材料,借助聚丙烯酸钠构筑三维聚合物网络封装相变材料,利用CNFs提升复合材料的导热系数.通过Raman、XPS等测试方法,研究了CNFs经高能球磨、湿化学氧化处理后,其表面含氧官能团的变化;借助Raman、DSC、Hot disk、TG等测试方法,分析了CNFs对复合材料化学相容性、相变行为、热稳定性、潜热容量、导热系数的影响.结果表明:CNFs经过功能化处理,氧、碳原子比增大至0.140,氧化效果显著;CNFs引入至复合相变材料中,体系内各组分之间存在良好的化学相容性;当CNFs的添加量达到3％(质量分数),复合材料的固、液态导热系数分别达到1.05 W/(m·K)、0.88 W/(m·K),相较于未添加CNFs的复合材料,固、液态导热性能分别提升了69.4％、60.0％;经过1000次循环试验,复合材料的熔融焓和结晶焓相较循环前分别下降了56.2％、65.3％,相变体系仍然具备一定的储热能力,表明将相变材料嵌入三维网络结构是一种有效的封装策略.

To solve the problem of the shortened cycle life of phase-change latent heat storage due to the large subcooling degree and serious phase stratification of mirabilite phase-change materials, a graphene oxide/mirabilite composite phase-change material (GO–MCPCM) was prepared with Na2SO4·10H2Na2CO3·10H2–NaCl phase-change composite as a matrix and graphene oxide (GO) as additives. The microstructure and properties of GO and GO–MCPCMs were characterized by scanning electron microscopy, transmission electron microscopy Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetry-Differential scanning calorimetry, respectively. The results show that the O/C ratio in oxidized graphene oxide is increased by 65.75%, the structural defect level is increased from 0.224 to 1.088, indicating that the oxidation–treated graphene has no agglomeration phenomenon and has good hydrophilicity and compatibility. The crystalline phase transition temperature of GO–MCPCMs is 23 ℃, the degree of subcooling reduces to 0 ℃, only sodium sulfate decahydrate releases heat, and the crystalline hydrate is Na2SO4·10H2O with a grain length of approximately 2 cm. The maximum latent heat of GO–MCPCMs crystallization at a mass fraction of 0.075% is 156.7 J/g, and the attenuation rate of the latent heat of GO–MCPCMs crystallization at a mass fraction of 0.075% is 4.3% after 500 solid–liquid cycles. Therefore, the addition of GO can improve the thermal stability of the mirabilite composite phase-change material, and graphene oxide/mirabilite composite phase-change material prepared has a good thermal cycle stability and a long service life.

As a kind of essential hydrated salt phase change energy storage materials, mirabilite with high energy storage density and mild phase-transition temperature has excellent application potential in the problems of solar time and space mismatch. However, there are some disadvantages such as supercooling, substantial phase stratification and leakage problem, limiting its further applications. In this work, for the preparation of shaped mirabilite phase change materials (MPCMs), graphene (GO), sodium carboxymethyl cellulose (CMC), and carbon nanofibers (CNFs) were used as starting materials to prepare lightweight CMC/rGO/CNFs carbon aerogel (CGCA) as support with stable shape, high specific surface area, and well-arranged hierarchically porous structure. The results show that CGCA has regular layered plentiful pores and stable foam structure, and the pore and sheet interspersed structure in CGCA stabilizes PCMs via capillary force and surface tension. The hydrophilic aerogels supported MPCMs decrease mirabilite leaking and reduce supercooling to around 0.7‒1 °C. The latent heats of melting and crystallization of CGCA-supported mirabilite phase change materials (CGCA-PCMs) are 157.1 and 114.8 J·g−1, respectively. Furthermore, after 1500 solid‒liquid cycles, there is no leakage, and the retention rate of crystallization latent heat is 45.32%, exhibiting remarkable thermal cycling stability.

Carbon sponge can be used as a carrier for phase-change materials due to its advantages of low density, large pore volume, and high thermal conductivity. A carbon sponge with certain graphitization characteristics and a porosity of 96.30% was synthesized as a carrier with absorbent cotton and MgO as raw materials, and a composite phase-change material encapsulated by a porous carbon sponge was prepared with Na2SO4·10H2O/Na2HPO4·12H2O as a phase-change medium. The results show that the adsorption amount of carbon sponges prepared at 700, 800 ℃ and 900 ℃ to the phase-change materials is 60, 75 and 102 times greater than their weights, respectively. Also, the solid-liquid phase-change cycle performance of the carbon sponge-encapsulated materials prepared at different temperatures was discussed at 5–60 ℃. After 5 000 cycles, the latent heat of the phase-change material is still > 200 J·g–1, which is reduced by 13%, and the thermal conductivity increasing rate is > 50%. The composite phase-change material encapsulated by porous carbon sponge has promising application prospects in the field of solar energy storage.

以Na2SO4·10H2O-Na2CO3·10H2O-NaCl三元相变体系为基液,采用两步法制备氧化石墨烯(GO)芒硝基相变纳米流体(GSPCNs).结果表明:纳米GO在温度为35℃以上超声分散于芒硝基相变材料中具有较好的分散稳定性;在35～50℃的温度下,GO-GSPCNs的黏度随时间恒定,无触变性;在35℃下,剪切速率大于30 s-1时,GO-GSPCNs是牛顿型流体,剪切速率小于30 s-1时呈非牛顿剪切变稀行为,服从宾汉姆(Bingham)流体模型,一致性指数高于0.999.在剪切应力为100 Pa时,GO-GSPCNs黏度随着温度升高而降低.经1 200次固-液循环后,不同体积分数的GO-GSPCNs流变行为在低剪切速率时发生变化,循环后的流体黏度降低,流动阻力减小.

本工作以纳米碳粉为原料,浓酸及氨水、乙醇等为改性剂,制备了含有亲水性基团的改性纳米碳粉,并通过两步法制备出纳米碳粉芒硝基纳米流体.结果表明:与未改性纳米碳粉相比,改性纳米碳粉表面均含有亲水性基团,能稳定分散在芒硝基纳米流体中.芒硝基纳米流体温度越低,粘度对体积分数变化的感知能力越强;纳米碳粉体积分数越低,粘度对温度变化的感知能力越弱.40℃下,添加0.25％(体积分数)改性纳米碳粉的芒硝基纳米流体,相比于未添加纳米颗粒的芒硝基相变材料,其导热系数平均增长11.93％.通过H-C模型可知,改性纳米碳粉在芒硝基纳米流体中的分散稳定性优于未改性纳米碳粉.

无机水合盐相变储能材料较低的导热系数导致了其缓慢的吸放热速率,限制了水合盐的实际应用.本工作以芒硝(Na2 SO4·10H2 O)为相变材料、聚丙烯酸钠(PSA)为支撑材料,利用硼砂改善相变体系的过冷度,借助高导热的碳纳米纤维(CNFs)来提升复合相变材料的导热系数.从SEM图中可知,CNFs-Na2 SO4·10H2 O/PSA被成功制备,且芒硝和功能化的CNFs嵌入到PSA形成的三维网络结构中.拉曼光谱和红外光谱的结果表明相变体系各组分之间具有良好的化学相容性.DSC曲线表明,聚丙烯酸钠与芒硝之间的相互作用使得体系相变行为得到调整,Na2SO4·10H2O/PSA的熔融焓和结晶焓分别为197.2 J/g和137.0 J/g.与Na2SO4·10H2O/PSA相比,CNFs-Na2SO4·10H2O/PSA的导热系数得到显著提升,固态热导率达到1.2 W/(m·K)左右,液态热导率达到1.0 W/(m·K)左右.此外,经过300次的循环试验,复合相变材料的熔融焓和结晶焓分别下降了23.3％、28.8％.