Inorganic phase change materials (PCMs), such as common eutectic salts-solar salt (60 wt% NaNO3+40 wt% KNO3) and Hitec salt (53 wt% KNO3+7 wt% NaNO3+40 wt% NaNO2)-are widely used in solar thermal power storage due to high stability and low cost. However, optimizing eutectic compositions requires extensive experiments, and material compatibility with pipelines/storage tanks remains a key challenge. Herein, nine NaOH-NaNO3 mixtures of varying molar ratios were melt-cooled and screened via DSC, yielding three eutectic formulations. The 6:4 NaOH:NaNO3 composite (NN-PCM) exhibited a phase transition temperature of 268 degrees C, enthalpy of 260 J/g (a 50 degrees C reduction from pure components), and a maximum service temperature of 480 degrees C. Corrosion tests at 300 degrees C for 1000 h in sealed vessels revealed increasing corrosion rates in 310S stainless steel, ductile iron, 304 stainless steel, and 45 steel. Post-test analyses confirmed NN-PCM retained eutectic properties: stable melting temperature (268 degrees C), 11-17 degrees C lower solidification temperature, and 7 % enthalpy reduction (20 J/g). This work offers insights into inorganic PCM applications in medium-to-high-temperature energy storage systems.

The NaOH-NaNO3 system exhibits excellent application potential in the medium-temperature thermal energy storage field owing to its high phase change enthalpy. However, when determining the eutectic composition ratio using the traditional proportion method, it is not only time-consuming and labor-intensive but may also miss the optimal ratio. In this study, the eutectic points of this composite system were predicted via FactSage software, yielding 3 sets of data. The corresponding molar ratios of NaOH/(NaOH + NaNO3) are 0.28, 0.6, and 0.81, respectively, and the prediction results were verified to be accurate through DSC analysis. Based on this, the eutectic material with a molar ratio of NaOH to NaNO3 of 6:4 was selected, designated as NN-PCM, and then compounded with 2-10 wt% expanded graphite (EG). Studies indicate that the sample compounded with 6 wt% EG (denoted as NN-PCM-6EG) is the optimal composite material: its thermal conductivity reaches 3.38 W/(m & sdot;K), which is a 256% increase compared to pure NN-PCM; its thermal diffusivity is 0.78 mm2/s, representing a 290% improvement; meanwhile, it exhibits good shape stability. Furthermore, the phase change enthalpy of this composite material is 114 J/g, with a phase change temperature of 262 degrees C. After 200 cycles, the fluctuation range of its phase change enthalpy is controlled within 3%. Verified by ANSYS thermal simulation, NN-PCM-6EG possesses an excellent thermal response rate; additionally, introducing a fin structure into the heat transfer system can significantly enhance the system's heat transfer efficiency.

To achieve efficient energy management and intelligent responsive control of phase change material (PCM), a composite PCM with simultaneous energy storage and superior photothermal conversion capability was developed. Carbon foam (CF) was served as matrix material, on which zinc oxide (ZnO) and polypyrrole (PPy) were allowed to deposited to form a hierarchical micro-nano interface, with stearic acid (SA) impregnated as a phase change component. The CF framework provided efficient thermal conduction pathways and elastic structural support, while the interfacial synergy between ZnO and PPy significantly enhanced light absorption and photothermal conversion efficiency. The optimal thermal performance was achieved at ZnO to PPy precursor concentration ratio of 1.5:1 (MCF/SA-2). Under light irradiation, the material possessed excellent photothermal response of 96.6%, high latent heat storage of 186.4 J & sdot;g-1, outstanding thermal cycling stability, and a remarkable shape recovery ratio of 97.7%. This work offers an effective strategy for developing solar-driven intelligent energy storage, programmable thermal regulation, and flexible adaptive systems, giving a huge potential for the future industrial use.

Phosphogypsum (PG), a massive industrial solid waste, consists primarily of calcium sulfate dihydrate (CSD), a promising material for thermochemical energy storage (TCES). However, CSD's high dehydration temperature (~140 °C) limits its compatibility with low-grade industrial waste heat and non-concentrating solar thermal sources. To lower this operating temperature, we introduced Zn2+ into a PG-based CSD system using a low water-to-solid ratio, non-equilibrium “dropwise addition–drying” hydration route. Structural and elemental analyses revealed that Zn2+ incorporated uniformly without forming independent crystalline phases, inducing an anisotropic unit-cell contraction of ~0.18%. Spectroscopic and microscopic characterizations demonstrated that Zn doping caused broadened coordination environments, nanoscale voids, planar disorder, and rough growth interfaces. Density Functional Theory (DFT) calculations indicated that ZnO bonds possess stronger orbital hybridization and higher local stability than CaO bonds, acting as the microscopic origin for strain accumulation and defect formation. Consequently, the apparent dehydration peak temperature decreased significantly from 141.5 °C in the undoped control to 73.7–97 °C in the Zn-doped samples. This reduction results from a dual mechanism: altered local bonding destabilizes bulk water molecules, while defect structures enhance water migration kinetics. To ensure cyclic stability and mitigate structural stress, the doped salts were composited with an expanded graphite (EG) matrix. Over 30 ex-situ dehydration–rehydration cycles, the optimal PG-Zn-5.4 composite maintained a dehydration peak of 97.0 °C and a gravimetric energy storage density of 434.1 J g−1. This study highlights transition-metal doping via non-equilibrium crystallization as a robust strategy for tuning low-temperature TCES materials.

In the fields of nuclear engineering and solar thermal utilization, low melting point alloys with excellent thermal conductivity and heat transfer performance have attracted extensive research as a new generation of heat transfer fluids, leading to many fundamental and important application issues. This study investigates the high-temperature corrosion behavior of Sn-50Bi-2Zn (wt.%) heat transfer alloy against 304 stainless steel (304), 310S heat-resistant steel (310S), and 20 carbon steel (20C) at 600 °C. Theoretical analysis, based on Fick’s diffusion law, and experimental measurements reveal significant differences in corrosion severity. After 473 h, 20 carbon steel exhibited the lowest corrosion layer thickness (0.07 mm), while 310S suffered the most severe corrosion (1.50 mm), exceeding 304SS (0.83 mm) by 81%. Diffusion coefficients derived from Sn penetration depths further quantified these trends: D310S = 2.51 × 10−7 mm2/s (6.8 × higher than 304: 3.7 × 10−8 mm2/s) and D20C = 2.87 × 10−10 mm2/s (128 × lower than 304SS). XRF analysis confirmed the dissolution of steel components into the molten alloy, with Fe, Cr, and Ni content increasing to 0.382 wt.%, 0.417 wt.%, and 0.694 wt.%, respectively, after 480 h. These results underscore the critical role of Ni content in accelerating Sn/Zn diffusion and pore formation, providing actionable insights for material selection in high-temperature heat transfer systems.

With the increasing power density of integrated circuits challenging traditional passive heat dissipation, novel materials such as phase change hydrogel are often required. In this work, a biomimetic sweating phase change composite hydrogel is presented where a Co-N/O coordination structure is fabricated via the coordination reaction of CoSO4 center dot 7H2O and ethanolamine. The hydrated salt phase change material, Na2SO4 center dot 10H2O, is embedded in a polyacrylamide matrix, and carbon nanotubes are introduced to construct a 3D thermal conduction pathway. During the phase change, Na2SO4 center dot 10H2O absorbs heat and releases water for evaporative cooling. The Co-N/O structure, acting as a hygroscopic site, adsorbs ambient moisture when the system is inactive, promoting the hydration and regeneration of Na2SO4 center dot 10H2O and enabling synergistic optimization. This composite hydrogel features a phase change enthalpy exceeding 130 J center dot g-1. The addition of carbon nanotubes boosts its thermal conductivity by 107 % to 0.793 W center dot m-1 center dot K-1. The Co-N/O structure significantly enhances its moisture absorption/desorption capabilities, with a moisture absorption rate of 4.71 g center dot g-1 at 95 % relative humidity and a maximum water absorption rate of 2.7 g center dot g-1 center dot h-1. At 30 % relative humidity, over 80 % of water is released within 50 min at 60 degrees C. In operation, it reduces the heating plate temperature by 8.6 degrees C and maintains a low temperature for 140 min, offering an efficient and eco-friendly solution for high-density electronic device heat dissipation.

Developing multifunctional composite phase change materials (PCMs) featuring enhanced photothermal energy conversion and storage performance is of vital importance, yet traditional organic PCMs suffer from inherent drawbacks, including leakage and poor thermal conductivity throughout the phase change process. To solve this problem, a new PCM design is provided, where stearic acid (SA) was employed as a latent heat storage unit, and carbon foam (CF) was served as a supporting framework. In this design, CNTs/SiC composite nanoparticles were uniformly dispersed into epoxy resin (ER) to fabricate a photothermal conversion coating. The modified epoxy resin (MER) coating acted as a protective effect for the internal PCMs, effectively mitigating leakage during phase transitions. With the incorporation of 9 wt% CNTs/SiC, the prepared composite PCMs retained the high latent heat (143.5J center dot g- 1) and excellent photothermal conversion efficiency (96.76 %). Furthermore, the latent heat of the material showed a minimal reduction of only 0.4 % following 200 thermal cycles. These results demonstrate the potential of composite PCMs for efficient solar energy harvesting and storage in thermal regulation systems.

Solid–liquid phase-change materials (PCMs) have attracted considerable attention in heat energy storage due to their appropriate phase-transition temperatures and high thermal storage density. The primary issues that need to be addressed in the wide application of traditional PCMs are easy leakage during solid–liquid phase transitions, low thermal conductivity, and poor energy conversion function. The heat transfer properties of PCMs can be improved by compounding with carbon materials. Carbon nanotubes (CNTs) are widely used in PCMs for heat storage because of their high thermal conductivity, strong electrical conductivity, and high chemical stability. This study investigates the thermal properties of 1-octadecanol (OD) modified with different diameters and amounts of CNTs using the melt blending method and the ultrasonic dispersion method. The aim is to enhance thermal conductivity while minimizing latent heat loss. The physical phase, microstructure, phase-change temperature, phase-transition enthalpy, thermal stability, and thermal conductivity of the OD/CNTs CPCMs were systematically studied using XRD, FTIR, SEM, DSC, and Hot Disk. Moreover, the heat charging and releasing performance of the OD/CNTs CPCMs was investigated through heat charging and releasing experiments, and the relationship among the composition–structure–performance of the CPCMs was established.

In order to solve the low thermal conductivity and leakage challenges of phase change materials (PCMs), a high-performance composite phase change material (CPCM) by integrating nickel foam (NF), carbon nanotubes (CNTs), and polydopamine (PDA) is developed. A three-dimensional (3D) porous NF/CNTs@PDA framework was constructed through oxidative self-polymerization of PDA on NF surfaces, followed by ultrasonic-assisted CNTs impregnation. CNTs-NF interfacial bonding was strengthened and interfacial thermal resistance was reduced by the PDA coating, as demonstrated in experimental results, leading to enhanced thermal conductivity. Light absorption and heat conduction were further optimized by CNTs. The optimized CPNF-9/PEG composite exhibited a thermal conductivity of 0.899 W m(-1) K-1, representing an 565.93 % enhancement over pure PEG (0.135 W m(-1) K-1). The melting and crystallization enthalpies of the material were 121.13 J g(-1) and 113.44 J g(-1) respectively, and solar-thermal tests indicated a 95.37 % conversion efficiency. After 200 thermal cycles, the composite maintained stable phase change latent heat (loss rate <3 %) and structural integrity, indicating excellent cyclic durability. Furthermore, leakage resistance tests at 80 degrees C revealed minimal mass loss (2 % over 100 min), highlighting its suitability for high-temperature applications. The work provides a novel strategy for designing efficient solar-thermal energy storage systems, with potential applications in solar-thermal management and renewable energy conversion technologies.

Stability and multifunctionality greatly extend the applications of phase change materials (PCMs) for thermal storage and management. Herein, CuS and Fe3O4 nanoparticles were successfully loaded onto cotton-derived carbon to develop a multifunctional interface with efficient photothermal conversion and electromagnetic interference (EMI) shielding properties. 1,3:2,4-di-(3,4-dimethyl) benzylidene sorbitol (DMDBS) and expanded graphite (EG) formed an organic/inorganic three-dimensional network framework to encapsulate 1-octadecanol (OD) by self-assembly. Finally, multifunctional shape-stabilized PCMs (SSPCMs) with the sandwich structure were prepared by the hot-press process. Multifunctional SSPCMs with high load OD (91%) had favorable thermal storage density (200.6 J/g), thermal stability, and a relatively wider available temperature range with improved thermal conductivity to support the thermal storage and management realization. Furthermore, due to the synergistic enhancement of two nanoparticles and the construction of the carbon network with cotton carbon and EG, highly efficient photothermal conversion (94.4%) and EMI shielding (68.9 dB average, X-band) performance were achieved at about 3 mm thickness, which provided the possibility of the multifunctional integration of PCMs. Conclusively, this study provides new insights towards integrating solar energy utilization with the comprehensive protection of related electronics.

The significant importance of developing phase change materials (PCMs) lies in their capability to meet diverse usage needs, particularly in the sphere of solar energy utilization. In this work, a thermal storage substrate was formed by adsorbing stearic acid in a biocarbon skeleton via vacuum impregnation. A composite PCM with multifunctional properties was subsequently synthesized by modifying the carbon mesh with copper sulfide (CuS) and zinc oxide (ZnO), compounding it onto the surface of the heat storage substrate. The biocarbon skeleton possesses a well-graded pore structure, which offers a significant number of channels for efficient heat transfer and effective electromagnetic shielding. The composite PCM retained a latent heat exceeding 155 J center dot g(-1). The integration of the biocarbon skeleton and modified carbon mesh led to a remarkable 119.42 % enhancement in thermal conductivity within the composite system, as compared to pure stearic acid. Furthermore, granular ZnO and nanoflower-like CuS are effectively integrated on the surface of the carbon mesh, facilitating the formation of localized surface heterojunctions. The composite system exhibits excellent broad-spectrum light absorption capability, producing a significantly elevated photothermal conversion efficiency of 88.93 %. Moreover, the semiconductor effect contributes to a remarkable degradation efficiency of 99.33 % for methylene blue. Significantly, the composite material demonstrates exceptional electromagnetic shielding capability, yielding a total shielding effectiveness exceeding 40 dB. The composite system also demonstrated outstanding thermal and cycling stability, with a negligible latent heat loss of merely 1.9 % even after undergoing 500 thermal cycles. This work proposes a pragmatic methodology to accomplish the functional integration of PCMs.

The slow heat transfer rate, leakage susceptibility, and low photothermal conversion efficiency of the phase change materials (PCMs) may limit their application in thermal energy storage. To tackle this problem, photothermal composites (MoS2-rGO) were prepared by hydrothermal synthesis method, and then polyethylene glycol6000 (PEG-6000) and MoS2-rGO composites were encapsulated in polyacrylamide (PAM) by free radical polymerization to form an integrated photothermal storage system. The melting enthalpy (Delta Hm) of the light-thermal phase change gel (LTPCG) was 140.9 J/g and the crystallization enthalpy (Delta Hc) was 134.8 J/g when the PEG6000 loading reached 85 %. After 300 cycles, the Delta Hm and Delta Hc were 137.7 and 132.1 J/g, respectively, which were 2.3 % and 2.1 % lower than the initial values, demonstrating excellent thermal storage durability. In addition, under simulated solar irradiation conditions, the MoS2-rGO composites were able to capture photons and rapidly transfer phonons with high efficiency, achieving a photothermal conversion efficiency of 87.5 %. The prepared composite PCM has excellent thermal storage and photothermal properties, which are of practical significance for the efficient use of solar energy.

It is indisputable that the impact of buildings on global energy demand. To address the issue of excessive energy consumption in buildings, this manuscript proposes the preparation of a flexible composite phase change films with excellent solar energy absorption conversion and thermal management capabilities. In this paper, composite phase change material was obtained by adsorbing paraffin into expanded graphite (EG) using vacuum adsorption method. The photothermal material copper sulfide-carbon nanotubes (CuS-CNTs) was synthesized by hydrothermal reaction. The dispersion of EG and carbon nanotubes (CNTs) in polyvinylidene fluoride (PVDF) matrix was enhanced under the influence of polyvinylpyrrolidone (PVP). The flexible and bendable films were finally prepared by using the non-solvent-induced phase separation method. The latent heat of the film reaches 63.63 J/ g, and the thermal conductivity of the film system approaches to 0.53 W/(m & sdot;K) through the adsorption of the high thermal conductivity enhanced phase EG and the intervention of CNTs. The photothermal conversion ability of CuS-CNTs improves the photothermal performance of the film, and the solar energy utilization reaches 46.2 % under simulated sunlight. The experimental results show that the prepared films can effectively convert solar energy into thermal energy and store it in the form of latent heat, and the films can release the energy in the form of heat again at low temperatures. Utilizing this property, the film can be applied to the field of building materials, which demonstrates great potential and prospect in reducing energy consumption and carbon emission in buildings. The prepared composite phase change film for photothermal conversion provides a new idea for modern building thermal management materials.

In this work, hierarchical porous ceramics based on diatomite with both high strength and low thermal conductivity were prepared by low-temperature sintering using modified diatomite and dolomite as the main raw materials. In particular, dolomite served both as a pore-forming agent to produce CO2 gas and as a ceramic component to produce porous MgO in situ. The prepared porous ceramics exhibited a hierarchical pore structure, retaining 2-300 nm nano-pores of the diatomite itself while using dolomite decomposition to produce 1-10 mu m macro-pores and porous MgO with inter-layer pore sizes of 50-300 nm. The main phases of porous ceramics were cristobalite phase, pyroxene phase, wollastonite phase and MgO phase with special structure. The effect of dolomite addition on the mechanical properties and thermal insulation of porous ceramics was investigated. It was found that the addition of 30% dolomite resulted in a porous ceramic with a porosity of 59.8% and the most favorable pore size distribution. At this time, the presence of wollastonite and pyroxene-like products in the porous ceramics contributed to the highest compressive and bending strengths of 29.66 MPa and 7.22 MPa, respectively. The lowest thermal conductivity of the porous ceramics reached 0.094 W & sdot;m- 1K-1, which can be attributed to the synergistic effect of the hierarchical pores and the increasing interfacial thermal resistance. Overall, the prepared hierarchical porous ceramics exhibited great potential as an alternative material to ceramic fiber insulation in high-temperature kilns.

Multiform NiO nanowalls with a high specific surface area were constructed in situ on carbon foam (CF) to construct NiO@CF/OD composite phase change materials (CPCMs). The synthesis mechanism, microstructures, thermal management capability, and photothermal conversion of NiO@CF/OD CPCMs were systematically studied. Additionally, the collaborative enhancement effects of CF and multiform NiO nanowalls on the thermal properties of OD PCMs were also investigated. NiO@CF not only maintains the porous 3D network structure of CF, but also effectively prevents the aggregation of NiO nanosheets. The chemical structures of NiO@CF/OD CPCMs were analyzed using XRD and FTIR spectroscopy. When combined with CF and NiO nanosheets, OD has high compatibility with NiO@CF. The thermal conductivity of NiO@CF/OD-L CPCMs was 1.12 W/m·K, which is 366.7% higher than that of OD. The improvement in thermal conductivity of CPCMs was theoretically analyzed according to the Debye model. NiO@CF/OD-L CPCMs have a photothermal conversion efficiency up to 77.6%. This article provided a theoretical basis for the optimal design and performance prediction of thermal storage materials and systems.

Phase change materials limit practical applications due to their relatively weak thermal conductivity and leakage resistance. The present work focuses on the development of a novel composite PCM (CA-TD/ZnO/EG), which was prepared by adsorbing a binary mixture of n-decanoic acid-tetradecanol (CA-TD) based on the combination of expanded graphite (EG) and zinc oxide (ZnO) nanoparticles. A new support material, ZnO/EG, was assembled by depositing specially shaped ZnO onto the surface of an expanded graphite substrate using an atomic deposition method. In addition to maintaining the porous structure of EG and preventing the leakage of CA-TD, the ZnO/EG reduces the interfacial thermal resistance between the substrate and the PCM molecules, which leads to the maximisation of the thermal conductivity. The prepared CA-TD/ZnO/EG-10 composite has a phase transition temperature of 19.5 °C, a heat of 157.3J/g, and a thermal conductivity of (6.131W·m-1·K-1) improved by 351.7% compared to the CA-TD material. Its faster heat transfer rate is directly reflected in the infrared image, with a small enthalpy change of 1.2% during 200 cycles of heating-cooling, as well as some photothermal conversion capability. The results of this paper can provide prospects for the functional design, modification, and enhancement of composite PCM.

Hydrated salt phase change materials have great application value in passive thermoregulation fields due to their low phase change temperature. However, their practical applications are limited by problems such as leakage and phase separation, which require urgent attention. To solve these problems, in this study, a W/O emulsion system was constructed by sol -gel method, and microencapsulated composites with graphene oxide (GO) as the thermally conductive reinforcing phase, silica as the shell material, and calcium chloride hexahydrate (CaCl2.6H(2)O, CCH) as the core material was prepared. The regular spherical SiO2 shell layer effectively reduces the possibility of leakage of the core material. The excellent thermal conductivity of GO increases the thermal conductivity of the composites by about 41.14 % compared with that of pure CCH and maintains a latent heat of >114.1 J/g. The encapsulation of SiO2 and the introduction of GO improve the thermal cycling stability of the composites. After 150 thermal cycles, the composites still had 96.5 % (110.1 J/g) latent heat and 99.6 % (0.708 W.m 1.K- 1) thermal conductivity. The GO/SiO2@CCH microencapsulated composites had good temperature regulation. This study provides a promising solution for preparing hydrated salt-based shape-stabilized composites and expands their applications in construction and other fields.

The development of microencapsulated phase change materials (PCMs) integrating solar photothermal conversion and storage holds significant for solar energy utilization. Herein, this study developed an efficient lightdriven phase change microcapsule system by encapsulating paraffin within a brookite TiO2 shell through solgel interfacial polymerization, followed by wrapping titanium nitride (TiN)/carbon nanotubes (CNTs) nanocomposites on the shell surface. The microcapsule system exhibited a regular spherical core-shell structural morphology. The encapsulation of TiO2 and the introduction of the highly thermal conductivity enhancement phase increased the thermal conductivity of the microcapsule system by approximately 151.5 % compared to pure paraffin while maintaining latent heat of over 135 J & sdot;g- 1. Furthermore, TiN/CNTs were combined with the microcapsule shell through hydrogen bonds and shared electron pairs, constructing localized surface plasmon resonance (LSPR)-enhanced heterojunction. The microcapsule system demonstrated excellent broad-spectrum light absorption capacity, resulting in a remarkable 112.01 % enhancement in the optimum photothermal conversion efficiency. Concurrently, the degradation rate of MB was increased by 59.52 % due to the synergistic catalytic action of photothermal, semiconductor, and LSPR effects. The microcapsule system also exhibited excellent thermal and cycling stability, with only 1.6 % latent heat loss after 500 thermal cycles. This study provides a promising strategy for developing energy storage microcapsule composite PCMs for the efficient collection and utilization of solar energy.