Shape-stabilized Composite Phase Change Materials Research Articles

Development of CaCl2·6H2O-mannitol/SiO2 shape-stabilized composite phase change material for the radiant cooling panel system

Radiant cooling panel systems are now popular solution for low carbon buildings, so has received great attention of researchers. Current development, however, is that radiant cooling panel systems have low cooling efficiency and cause high pressure on national energy supply during peak energy consumption periods. This study, therefore, has developed a novel composite phase change material (CPCM) coupled with a typical radiant cooling panel system, providing longer indoor comfort duration and less temperature fluctuation, while also alleviating the pressure on national energy supply during peak energy consumption. In this study, eutectic hydration salt of CaCl2·6H2O and mannitol have been combined with SiO2 to prepare a shape-stabilized CPCM. It has been placed in a test room to justify the impact of the new material. Experimental results have demonstrated some major properties of this material, namely, a melting point of 20.7 °C, a high latent heat value of 119.8 J/g, and a supercooling degree of 1.3 °C, as well as good stability and thermal reliability. Therefore, it can be used as a good solution for radiant cooling panel systems. Comparing the results with another test room with ordinary radiant cooling panels, the room with the new CPCM panel showed less indoor temperature fluctuation and 73 % longer indoor comfort duration. This work provides further development of using hydrated salts and CPCMs with different phase change temperatures in radiant cooling panel systems.

Stable and reliable PEG/TiO2 phase change composite with enhanced thermal conductivity based on a facile sol-gel method without deionized water

Some shortcomings exist in organic phase change materials, including leakage susceptibility, low thermal conductivity, and preparation complexity. Herein, polyethylene glycol/titanium dioxide shape-stabilized composite phase change material (PEG/TiO2 ss-CPCM) was fabricated by facile sol-gel method without deionized water using tetrabutyl titanate (TBOT) as precursor. In this composite, not adding deionized water prolonged the gelation time, allowing PEG to bind as much TiO2 as possible and enhancing energy storage capability; TiO2 acted as the supporting framework to maintain the material's shape stability and enhance thermal conductivity. The melting and crystallization phase change enthalpies of prepared PEG/TiO2 ss-CPCM were 128.3 J/g and 113.1 J/g with an encapsulation efficiency of 74.14 % when PEG: TBOT = 1.5: 1. After repeating 300 thermal cycles, the phase change enthalpy remained almost constant. Besides, the thermal conductivity of PEG/TiO2 ss-CPCM was 1.22 times that of PEG, and the potential for thermal management applications. The advantages (energy storage capability, shape stability in thermal environments, thermal reliability, and thermal management) of the PEG/TiO2 ss-CPCM prepared by facile synthesis, not only propose a phase change material with excellent thermal properties and shape stabilization but provide a green and feasible strategy for the fabrication of PEG/TiO2 composite phase change materials utilizing the sol-gel method.

Conceptual design and numerical analysis of a miscibility gap alloy-based solid-state thermal battery for electric vehicles

Heating the passenger cabin of electric vehicles at low temperatures consumes a large amount of battery power, resulting in a significant reduction in cruising range. On-board thermal energy storage is an effective way to improve the cruising range of electric vehicles in winter. Miscibility gap alloy is a new type of shape-stabilized composite phase change material, which has the advantages of high energy storage density, high thermal conductivity, low cost, and good safety. Therefore, using it to heat electric vehicles can increase their cruising range, prolong battery life, and reduce cost. In this paper, the concept of a compact on-board solid-state thermal battery based on miscibility gap alloy is proposed for the first time, and the heat charging, thermal insulation and heat discharging performance of the design are analysed based on numerical simulations. The results show that the thermal battery can reach a heat storage density of 553.8 Wh/L, and the average heat discharging power can reach 1.326 kW. The results of this paper can provide guidance for the engineering development of miscibility gap alloy-based solid-state thermal batteries.

Anisotropic and hierarchical porous boron nitride/graphene aerogels supported phase change materials for efficient solar-thermal energy conversion

The formation of shape-stabilized composite phase change materials (CPCMs) with special structure is an efficient strategy to prevent the leakage of phase change materials (PCMs) and improve the solar-thermal conversion ability. In this work, graphene and boron nitride nanosheets (BBNS) were prepared by the magnesiothermic reduction SHS method in CO2 and N2 atmosphere, respectively. Then, an anisotropic and hierarchical porous boron nitride/graphene aerogel with three-dimensional network was constructed by directional ice-freezing method using carboxymethyl cellulose as supporting framework and adhesive, and polyethylene glycol (PEG) was impregnated to prepare novel CPCMs. The CPCMs had enthalpies of 150∼160 J/g, and a highest thermal conductivity of 0.390 W/(m·K), which was around 47% higher than that of pure PEG. The ability of the CPCMs to convert solar energy to thermal energy was significantly enhanced. Under a simulated light intensity of sunlight (100 mW/cm2), its solar-thermal conversion efficiency reaches 94.92%, and after 20 min of irradiation, the surface temperature can reach 72 °C. These CPCMs are promising for the efficient use of renewable solar energy due to their high solar-thermal conversion efficiency and thermal storage capabilities.

Numerical simulation and optimization of compact latent heat exchanger with micro-channel plate in shape-stabilized composite phase change material

To enable the rapid provision of domestic hot water, this study presents the independent design of a plate heat exchanger featuring a large heat exchange area and a compact structure. Utilizing a sandwich structure, the thermal storage unit integrates two shaped composite phase change materials (CPCM), namely sodium acetate trihydrate (SAT)/expanded graphite (EG) blocks of identical thickness — in conjunction with a micro-channel heat exchange plate. Multiple thermal storage units are stacked to create the heat exchanger. Experimental validation of the heat transfer performance of this thermal energy storage heat exchanger is conducted, accompanied by the establishment of a heat transfer model elucidating the interaction between the phase change material (PCM) and the fluid. The investigation explores the impact of varying thicknesses of shape-stabilized CPCM, thermo-physical parameters of CPCM, and flow rates on enhancing the thermal efficiency of the thermal energy storage heat exchanger. Results indicate a competitive relationship between the phase change enthalpy and thermal conductivity of CPCM under constant density. Increasing the mass fraction of SAT effectively boosts its heat storage density. However, this improvement is counterbalanced by a reduction in CPCM's thermal conductivity, resulting in diminished heat transfer rates within the material and reduced efficiency in transferring heat between the material and the fluid. Optimal performance is achieved when the mass fraction of sodium acetate trihydrate is 80 wt% and the CPCM thickness is 20 mm. At these parameters, the thermal energy storage heat exchanger exhibits the highest heat transfer efficiency. Furthermore, the heat exchanger is capable of producing 197.86 kg of hot water in 1365 s at an inlet flow rate of 300 L/h, achieving an impressive discharging efficiency of 82.73 %. These findings underscore the feasibility of employing the mini-channel plate thermal energy storage heat exchanger for the rapid preparation of domestic hot water.

Converting bio-waste rice into ultralight hierarchical porous carbon to pack polyethylene glycol for multifunctional applications: Experiment and molecular dynamics simulations

A structural-functional integrated shape-stabilized composite phase change material (PCM) was synthesized by converting biowaste rice into ultralight (0.08 g/cm3) hierarchical porous carbon (CNR) to pack polyethylene glycol (PEG) PCM. The thermal property and corresponding mechanism were analyzed. The results show that the composite PCM exhibits excellent thermal storage efficiency (93.3 %), considerable solar photothermal conversion efficiency and superior thermal stability. The interfacial thermal resistance (ITR) of PEG/CNR is 73 % lower than graphene foam-based composite PCM thus a fast transient temperature response. Particularly, the package of PEG endowed composite PCM with elastic characteristic thereby an enhanced compressive strength. Furthermore, covering PEG/CNR results in a delay of approximately 1.3 times in reaching the peak temperature on the surface of electronic components, and a delay of 5 times in cooling time. This study presents solid guidelines for societal development that is sustainable and makes some recommendations for construction of composite PCMs combining multifunctional applications.

Design of a stearic acid/boron nitride/expanded graphite multifiller synergistic composite phase change material for thermal energy storage

• Stearic acid was encapsulated by various fillers. • A shape-stabilized composite phase change material was prepared. • Thermal and cycling stability of the prepared composite are excellent. • Thermal conductivity of the prepared composite is 6.349 W•m −1 •K −1 . In order to solve the problems of low thermal conductivity and easy liquid leakage of a stearic acid (SA), the composite phase change material(PCM) was prepared by adding boron nitride (BN) and expanded graphite (EG) to melted SA, and its thermal conductivity, crystal structure, chemical stability, thermal stability, cycle stability, leakage characteristics, heat storage/release characteristics, and temperature response characteristics were characterized. The results showed that the addition of BN and EG significantly improved the thermal conductivity of the material, and they efficiently adsorbed melted SA. The maximum load of SA was 76 wt. % and there was almost no liquid leakage. Moreover, the melting enthalpy and temperature were 154.20 J • g − 1 and 67.85°C, respectively. Compared with pure SA, the SA/BN/EG composite showed a lower melting temperature and a higher freezing temperature. In addition, when the mass fraction of BN and EG was 12 wt. %, the thermal conductivity of the composite was 6.349 W • m −1 • K −1 , which was 18.619 times that of SA. More importantly, the composite showed good stability for 50 cycles of heating and cooling, and the SA / BN / EG-12 hardly decomposes below 200°C, which implies that the working performance of the composite PCM is relatively stable within the temperature range of 100°C. Therefore, the composite can exhibit excellent thermal stability in the field of building heating.

Biomass-Based Shape-Stabilized Composite Phase-Change Materials with High Solar-Thermal Conversion Efficiency for Thermal Energy Storage.

To alleviate the increasing energy crisis and achieve energy saving and consumption reduction in building materials, preparing shape-stabilized phase-change materials using bio-porous carbon materials from renewable organic waste to building envelope materials is an effective strategy. In this work, pine cone porous biomass carbon (PCC) was prepared via a chemical activation method using renewable biomaterial pine cone as a precursor and potassium hydroxide (KOH) as an activator. Polyethylene glycol (PEG) and octadecane (OD) were loaded into PCC using the vacuum impregnation method to prepare polyethylene glycol/pine cone porous biomass carbon (PEG/PCC) and octadecane/pine cone porous biomass carbon (OD/PCC) shape-stabilized phase-change materials. PCCs with a high specific surface area and pore volume were obtained by adjusting the calcination temperature and amount of KOH, which was shown as a caterpillar-like and block morphology. The shape-stabilized PEG/PCC and OD/PCC composites showed high phase-change enthalpies of 144.3 J/g and 162.3 J/g, and the solar-thermal energy conversion efficiencies of the PEG/PCC and OD/PCC reached 79.9% and 84.8%, respectively. The effects of the contents of PEG/PCC and OD/PCC on the temperature-controlling capability of rigid polyurethane foam composites were further investigated. The results showed that the temperature-regulating and temperature-controlling capabilities of the energy-storing rigid polyurethane foam composites were gradually enhanced with an increase in the phase-change material content, and there was a significant thermostatic plateau in energy absorption at 25 °C and energy release at 10 °C, which decreased the energy consumption.

Beeswax as a potential replacement of paraffin wax as shape stabilized solar thermal energy storage material: An experimental study

Thermal Energy Storage (TES) using paraffin wax as Phase Change material (PCM) has been widely used for solar to thermal energy conversion and storage application. Being petroleum by-product, production of paraffin wax have embodied environmental impact and high carbon footprint. Beeswax can replace paraffin's as one of the clean, sustainable, eco-friendly and potential TES PCM. However, TES potential of Beeswax was not investigated thoroughly in previous literatures. Also, limited study has been found which evaluates solar to thermal conversion potential of Beeswax. This study presents a comprehensive analysis of TES performance of Beeswax supported by Bentonite clay and loaded with Graphite was evaluated. Bentonite clay was used as supporting material and Graphite powder is used as additive in varying percentage to form Shape Stabilized Composite Phase Change Material (SSCPCM). SSCPCM was initially investigated for anti-leakage behaviour and was found that Bentonite can hold maximum 40 wt% of Beeswax without leakage above phase transition temperature. Thermal energy storage parameters, thermal degradation, solar to thermal conversion performance, chemical stability, surface morphology, and thermal conductivity were evaluated. Bentonite and graphite has shown good morphology to form SSCPCM samples. Also, SSCPCM has proved to be chemically and physically stable thermal energy storage material. Melting enthalpy of 101.79, 100.66, 98.80, 100.43, 96.51, and 105.01 at melting point of 59.43, 58.88, 58.12, 57.98, 57.36, and 57.11 of SSCPCM-0, SSCPCM-1, SSCPCM-3, SSCPCM-5, SSCPCM-7, and SSCPCM-9 was obtained. Adding Graphite has reduced supercooling of SSCPCM samples maximum by 84.13 %. Increasing additives in PCM improves heating rate and thermal conductivity of the SSCPCM.

Preparation and thermal properties of phase change energy storage composite material based on modified fly ash

Fly ash (FA) is a kind of porous solid waste from coal-fired power plant, It is nominated as adsorption carrier for solid-liquid phase change material (PCM), While shape-stabilized composite phase change materials (SSCPCM) prepared directly has low thermal performance due to limited adsorption capacity of FA. Therefore, modification methods have become increasingly attractive, and four modification methods were investigated to improve the adsorption capacity of FA. Modification treatment experiment proved that the surface structure of FA is significantly corroded. Test analysis displays that the surface microspheres in FA have abundant particles and pores by destroying the Si–O–Si and Si–O–Al network structures. The mass ratio of Al/Si increased from 0.59 to 0.726, and the specific surface area of FA has been greatly increased. Experimental results indicate that alkali modification followed by high-temperature calcination is the desirable process for FA. For obtaining high thermal performance materials, two kinds of SSCPCM were prepared according to the mass ratio of 65:35 by vacuum adsorption while Alkali modified FA serves as carrier, binary eutectic of lauric acid-stearic acid (LA-SA) and lauric acid-myristic acid (LA-MA) serves as PCM respectively. The LA-SA/AFA-OH (NaOH alkali leaching treatment for FA) and LA-MA/AFA-OH (NaOH alkali leaching treatment for FA) could reach 54.49 J/g and 47.15 J/g and the phase transition temperature (PTT) is 37.45 °C and 32.36 °C, respectively. The SSCPCM has good thermal, chemical and morphological stability over 500 thermal cycles, while the LA-MA/AFA-OH had higher stability and less thermal performance slightly. Research finding provide a feasible process for composite modification of FA, and application scope is extended due to high thermal performance of composites.

Low-cost, thermo-conductive, hydrophobic, and shape-stabilized porous carbonized watermelon peel embedded phase-change materials for solar-energy-saving and conversion

The traditional phase change materials (PCMs) exhibited leakage problems, poor thermal conductivity, low solar-thermal conversion ability, and high cost. Therefore, a low-cost shape-stabilized composite PCM was prepared by impregnating n-Eicosane into the carbonized watermelon peel (CWP) coated with manganese oxide (MnO2) nanosheets (MnO2@CWP). The prepared MnO2@CWP-C20 composite PCMs have a good shape-stability, high thermal-conductivity (0.58 W/m K), high phase-change enthalpy (220 J/g), high energy conversion/storage efficiency (94.5%), outstanding cycle stability, hydrophobicity, and self-cleaning properties. The shape-stabilized MnO2@CWP-C20 composites PCMs not only provide a simple approach for the efficient utilization of solar energy but also expand the applications of low-cost biomass waste, thanks to their exceptional features.

Thermal energy storage performance of hierarchical porous kaolinite geopolymer based shape-stabilized composite phase change materials

Phase change materials (PCMs) are prospective energy materials that are widely applied in building energy conservation, waste heat recovery, infrared stealth technology and solar dynamic power system. The enhancement of heat transfer and leak-proof performance are critical to PCMs. Although geopolymers have been applied in thermal energy storage, meanwhile, hierarchically porous geopolymers have already shown superb performance in various functional applications, to the authors’ knowledge, no report concerning the application of hierarchical porous ones have been issued. This paper concerns the preparation of a shape-stabilized composite PCMs, consisting of hierarchically porous kaolinite-based geopolymer (PKG) embedding polyethylene glycol 4000 (PEG4000), which shows promising prospects in thermal energy storage. Optimized porous geopolymer matrices feature high porosity (>83%), combined with high specific surface area (4.7 m2/g) and thermal conductivity (TC, 1.324 W·m−1·K−1). Furthermore, the shape-stabilized composite PCMs show excellent thermal energy storage properties: loading rate of 80.93 wt%, latent heat of 168.80 J g−1 and TC of ∼0.36 W·m−1·K−1 at 20–30 °C, which is 1.64 times of the TC of pure PEG4000. Finally, the photothermal conversion performances of the shape-stabilized composite PCMs were also simulated.

Investigation on properties of phase change foamed concrete mixed with lauric acid-hexadecanol/fumed silica shape-stabilized composite phase change material

This experimental study developed a phase change foamed concrete (PCFC) with suitable temperature regulation and heat storage capabilities utilizing experimental design and numerical simulation. With the porous material adsorption method, a shape-stabilized composite phase change material (PCM) was prepared using fumed silica to absorb Lauric acid-Hexadecanol (LA-HD) binary eutectic. Through the Differential Scanning Calorimetry (DSC), Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectrometer (FT-IR), Thermal Gravimetric Analyzer (TGA) and liquid leakage tests, the results indicate that the best mass ratio of LA to HD in LA-HD binary eutectic is 53:47. The maximum adsorption ratio of fumed silica for LA-HD is 60 % (wt). The adsorption process is only a physical combination without chemical reaction, and the proposed composite PCM has stable morphological structures and physical properties. The effect of composite PCM on the dry density, compressive strength and thermal properties of PCFC was explored by changing the content (5 %, 10 %, 15 %, 20 %, 25 %, 30 %) of composite PCM in PCFC. The finite element software ABAQUS was used to establish the model of the PCFC wall, and its heat storage and temperature regulating performance was studied. The experiment results show that the dry density, compressive strength and thermal conductivity of the PCFC gradually decrease with the increase of composite PCM. When the content of composite PCM is 30 %, the dry density, compressive strength and thermal conductivity reach the minimum values of 579.6 kg/m3, 1.192 MPa and 0.105 W/(m·K), respectively. With the increase of composite PCM, the phase change temperature, latent heat and specific heat capacity of foam concrete also increase. When the content of composite PCM is 30 %, the phase change temperature is 36.13 °C, the latent heat is 35.02 J/g, and the specific heat capacity is 2467 J/(kg·°C). The finite element simulation results show that when the PCFC with 30 % composite PCM is placed in the middle of the wall, the inside surface temperature fluctuation range of the PCFC-wall-2 is 27.293 °C ∼ 28.707 °C, and the temperature difference is 1.414 °C, which is 0.0738 °C and 0.047 °C lower than that of PCFC-wall-1 and PCFC-wall-3, respectively; the time for PCFC-wall-2 to reach the peak and valley temperature is delayed by 0.1667 h than the other two walls. The results indicate that using PCFC in buildings can reduce the energy required for building cooling or heating and affect energy saving and environmental protection. Moreover, PCFCs arranged in the middle of the wall has better heat storage and temperature regulation effect than those arranged on both sides.

Long term properties of cement-based material incorporated with n-octadecane/diatomite composite SSPCM

The energy-saving concrete was developed by incorporating n-octadecane and diatomite composite shape-stabilized phase change materials (OC/D SSPCMs) into cement concrete. OC/D SSPCMs were prepared by vacuum impregnation of barrel diatomite. The results show that the melting point and enthalpy of OC/D SSPCMs are 25.02 °C and 60.26 J/g, and OC/D SSPCMs have good dispersion and compatibility in cement paste. As a structure-function integrated material, energy-saving concrete with compressive strength of 33.5 MPa has a broad application prospect. Self-designed room test results reveal that energy-saving concrete can reduce the indoor temperature by 4.5 °C. Long-term thermal/mechanical properties, volume deformation and microstructure after thermal cycling treatment were investigated. The results indicate that phase transformation behavior has a huge negative effect on the compressive strength and deformation tendency of energy-saving concrete, being mainly attributed to the significant volume evolution with the temperature of PCM and PCM encapsulation leakage.

Hydrate salt/fumed silica shape-stabilized composite phase change material with adjustable phase change temperature for radiant floor heating system

Radiant floor heating system combined with hydrate salt phase change materials (PCMs) can obtain energy savings along with improving thermal comfort. However, the inappropriate phase change temperature and the leakage of PCM limit its further applications. Here, sodium acetate trihydrate (SAT)-potassium chloride (KCl)-urea composite phase change material (CPCM) was composited with fumed silica (SiO2) to prepare shape-stabilized CPCM (SSCPCM) with adjustable phase change temperature for use in floor radiant heating. The effects of the mass fraction of SiO2 on phase change properties, and shape-stabilized ability of SSCPCM were emphatically studied. Besides, the morphology, porous structure analysis and chemical compatibility and related thermal properties of SSCPCM were discussed detailedly. The results manifested that SiO2 could not only regulate the melting temperature of SAT-KCl-urea CPCM, but also stabilize CPCM into its porous structure with large surface area and high porosity. Meanwhile, SSCPCM with 30 wt% SiO2 exhibited a good shape stability, and melted at 40.85 °C with high latent heat of 132.6 J/g, low supercooling degree of 0.29 °C as well as good thermal stability and thermal reliability. The result comparison of two test rooms confirmed that phase change floor radiant heating system can effectively increase the duration of indoor thermal comfort. All good thermal properties of SSCPCM make it prospective potential in radiant floor heating system for building energy efficiency.

Shape-stabilized composite phase change material for thermal insulation of cotton fabrics with sandwich structure

Disodium phosphate dodecahydrate was hybrid with n-octadecane as the phase change material (PCM) by reversed-phase emulsification. The cellulose sponge obtained based on cellulose nanocrystals was used as the support material to fabricate a shape-stable composite phase change material (CPCM) through impregnation. It was laminated with cotton fabric to obtain a sandwich structure thermal insulation fabric. An infrared spectrometer, scanning electron microscope, differential thermal scanning calorimeter, and other equipment were used to characterize the morphology, chemical groups, and latent heat properties of CPCMs and thermal insulation fabrics. The results displayed that the cellulose sponge had a porosity of 99.03%, a density of 0.012 g/cm3, and could withstand 1900 times its weight. When the mass proportion of PCM in the composite system was 67.5%, its latent heat energy was 84.44 J/g, which also revealed optimal shape stability. Compared to the original fabric, the thermal insulation efficiency of the sandwich structured fabric was increased by 17.7%∼18.2%, and the photothermal conversion rate reached 25.88%, with good application performance.

Integration of lauric acid/zeolite/graphite as shape stabilized composite phase change material in gypsum for enhanced thermal energy storage in buildings

The effectiveness of Gypsum plaster loaded with Shape Stabilized Composite Phase Change Material (SSCPCM) in regulating indoor temperature of the building is experimentally investigated in this study. SSCPCM is composed of Gypsum/Lauric acid/Zeolite loaded with varying percentage of Graphite (0 wt%, 5 wt%, and 10 wt%). The SSCPCM-0, SSCPCM-5, and SSCPCM-10 were characterized for morphology, physical structure, chemical structure, thermal energy storage capabilities, thermal stability, and thermal conductivity using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Fourier Transformation Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry, Thermo Gravimetric Analysis (TGA), and thermal conductivity meter respectively. The results suggest that SSCPCM have excellent surface morphology and shows good chemical, thermal and physical stability. Thermal energy storage capacity of 81.08 J/g, 74.02 J/g, and 54.30 J/g at thermal conductivity of 0.242 W/mK, 0.427 W/mK, and 0.774 W/mk were shown by SSCPCM-0, SSCPCM-5, and SSCPCM-10 respectively. Additionally, SSCPCM-5 has shown superior thermal reliability by maintaining the thermo-physical characteristics after 1000 thermal cycles. These SSCPCMs were used to prepare GPCM, GPCM-5, and GPCM-10 composite gypsum plaster and five day real outdoor testing was conducted by applying them on indoor roof and south wall of cubicles. GPCM has effectively improves the indoor temperature profile in comparison with GPCM-5 and GPCM-10.

A novel one-step ultraviolet curing fabrication of myristic acid-resin shape-stabilized composite phase change material for low temperature thermal energy storage

In this work we present for the first time a simply, fast and efficient process for the fabrication of form-stable composite phase change material (PCM) by ultraviolet (UV)-curing technique. Simply by UV-curing of the PCM with a desired UV curable carrier for several minutes, a neoteric UV-cured composite that suitable for low temperature thermal energy storage (TES) can be fabricated. The feasibility of such a novel technique is demonstrated by investigating a case of myristic acid (MA) dispersed into a UV curable resin containing polyurethane acrylate (PUA). The results show that a crosslinked structure is formed in the composite after UV-curing due to the occurrence of photochemical reaction, which offer sufficient paths to accommodate the PCM, endowing the composite with the great ability to maintain the structure stabilization and prevent the liquid leakage. A good physical and chemical compatibility has been achieved in the composite and 40 wt% of UV-curing resin grants the composite optimum formula at which a melting temperature of 52 °C and an energy storage density over 210.8 kJ/kg at temperature ranged 25–100 °C are obtained. The results also reveal that the material mechanical strength can be linked to the UV-curing duration. For a given V-curing time of 5–30 mins, the composite mechanical strength is measured over 25–34 MPa, almost over twice as high as that of high-density polyethylene (HDPE) and styrene ethylene butylene styrene (SEBS) based composites. Owing to the high shape strength and excellent thermal cycling performance, such UV-curable composites can be utilized for modular design of TES devices, and also be used to precisely and directionally produce TES devices through additive manufacturing. This work exploits a new perspective for the energy-saving and time-effective fabrication of shape stabilized composite PCMs for low temperature thermal energy storage.

Hierarchical Ni-plated melamine sponge and MXene film synergistically supported phase change materials towards integrated shape stability, thermal management and electromagnetic interference shielding

1 Hierarchical Ni@MS/RCG was prepared by electroless plating and sol-gel methods. 2 MX/Ni@MS/RCG/PEG PCMs were fabricated via a facile encapsulation approach. 3 MX/Ni@MS/RCG/PEG PCMs exhibit good shape stability and superb cyclic reliability. 4 MX/Ni@MS/RCG/PEG PCMs show high thermal conductivity and EMI shielding performance. Along with the integrated and miniaturized development of advanced electronic devices, phase change materials (PCMs) simultaneously with efficient thermal management and high electromagnetic interference (EMI) shielding effectiveness (SE) are ungently demanded. Herein, the shape-stabilized MXene/Ni-platted melamine sponge/Regenerated cellulose/Graphene nanoplate/Polyethylene glycol (MX/Ni@MS/RCG/PEG) composite PCMs comprising hierarchical Ni@MS/RCG and MXene film were fabricated via a facile encapsulation approach. Hierarchical Ni@MS/RCG hybrid aerogel was prepared by electroless plating and sol-gel methods, and MXene film was obtained using vacuum-assisted filtration procedure. The synergistic effect of conductive Ni@MS/RCG networks and tight MXene film endows MX/Ni@MS/RCG/PEG composite PCMs with good shape stability, high cyclic reliability, large latent heat of phase change (154.3 J g –1 ), excellent thermal conductivity (TC, 0.47 W m –1 K –1 ) and favorable EMI shielding performance (32.7 dB). The TC of acceptable 0.47 W m –1 K –1 is observed for MX/Ni@MS/RCG-5/PEG at a rather low GNP content of merely 0.39 wt%. In addition, the temperature variation of MX/Ni@MS/RCG-5/PEG is a lot faster than that of pure PEG in the heating/cooling process, revealing the remarkable energy storage and release efficiency for the composite PCMs. This investigation has taken an important step towards shape-stabilized composite PCMs with both effective thermal management and high EMI SE for promising applications in electronic packaging and advanced energy.

Highly thermal conductive shape-stabilized composite phase change materials based on boron nitride and expanded graphite for solar thermal applications.

Phase change heat storage technology is a good way to solve the problem that the temperature of solar hot water outlet is affected by the time domain. A stearic acid (SA)-benzamide (BA) eutectic mixture is a potential phase change material (PCM), but it still has the disadvantages of low thermal conductivity and liquid leakage. In this work, a new high thermal conductive shape-stabilized composite PCM was prepared by adding boron nitride (BN) and expanded graphite (EG) to a melted SA-BA eutectic mixture using an ultrasonic and melt adsorption method, and its phase change temperature, latent heat, crystal structure, morphology, thermal conductivity, chemical stability, thermal stability, cycle stability and leakage characteristics were characterized. The results indicates that the addition of BN and EG significantly improved the thermal conductivity of the SA-BA eutectic mixture, and they efficiently adsorbed the melted SA-BA eutectic mixture. Besides, when the mass fractions of BN and EG are 15 wt% and 20 wt%, respectively, the 15BN20EG composite has almost no liquid phase leakage. When the melting enthalpy and temperature of 15BN20EG are 132.35 J g-1 and 65.21 °C, respectively, the thermal conductivity of the 15BN20EG is 6.990 W m-1 K-1, which is 20.601 times that of the SA-BA eutectic mixture. Moreover, 15BN20EG shows good thermal stability after 100 cycles and good chemical stability below 100 °C. Therefore, the 15BN20EG composite is considered as a potential candidate for solar thermal applications.