Form-stable Composite Phase Change Research Articles

Cellulose nanofibril/polypyrrole hybrid aerogel supported form-stable phase change composites with superior energy storage density and improved photothermal conversion efficiency

The development of phase change materials (PCMs) with high energy storage density, enhanced photothermal conversion efficiency and good form-stability is essential for practical application in utilization of solar energy. Herein, novel PCM composites (CPPCMs) with extremely high energy storage density and superb solar-thermal conversion performance were fabricated by introducing n-octacosane into three-dimensional (3D) porous cellulose nanofibril (CNF)/polypyrrole (PPy) hybrid aerogels. Due to the strong encapsulation capability of CNF/PPy hybrid aerogels (CPAs), the synthesized PCM composites maintained perfect shape stability above the melting point of n-octacosane. Further investigation showed CPPCMs exhibited extremely high latent heat in the range of 239.4–258.4 J/g and high loading rate of n-octacosane (up to 96%). The melting/cooling cycling test and thermogravimetric analysis indicated the composite PCMs possessed excellent cyclic stability and thermal stability. Moreover, simulated sunlight test showed that the photothermal conversion efficiency of CPPCMs significantly improved with the increased content of polypyrrole in the PCM composites. In conclusion, the obtained PCM composites, which exhibited excellent shape stability, superior solar-heat conversion capability and extremely high energy storage density, showed considerable potential for practical utilization and storage of solar energy.

Surface modification effects in phase change material-infiltrated attapulgite

Attapulgite has nanoporous structure and is an excellent supporting material for the preparation of form stable composite phase change materials (FSCPCMs). However, the effects of surface characteristics of attapulgite on the attapulgite based FSCPCMs were unclear. In this work, the effect of surface modification on the properties of different kinds of attapulgite-based FSCPCMs was investigated. First, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (KH792) was used to modify attapulgite. Then, a series of FSCPCMs were prepared by adsorbing three kinds of phase change materials (PCM) with modified attapulgite (M-ATP). The crystallization and thermal properties of these FSCPCPMs were investigated. The results showed that, the surface modification improves the crystallinity and the latent heat of the FSCPCMs when paraffin or polyethylene glycol are used as the PCM. When the mass fraction of the PCM is 40%, the surface modification increases the latent heat of the paraffin/attapulgite FSCPCM and the polyethylene glycol/attapulgite FSCPCM by 31.5% and 27.8%, respectively. After 800 cooling and heating cycles, the thermal properties of paraffin/M-ATP and polyethylene glycol/M-ATP are still stable. The results were explained by analyzing the interaction between the PCM and the attapulgite. This study provides new ideas to improve the thermal properties of FSCPCMs through surface modification.

Preparation and performances of form-stable polyethylene glycol/methylcellulose composite phase change materials

A series of polyethylene glycol (PEG) /methylcellulose (MC) composites with various PEG mass loading (10%-50 wt%) were prepared via physical blending method as a new type of form-stable composite phase change material (CPCM). The transimission, chemical compatibility, thermal and mechanical properties of form-stable PEG/MC CPCMs were characterized using polarized optic microscopy (POM), Fourier transform infrared (FT-IR) spectrometer, differential scanning calorimetry (DSC), thermal gravimetric analyzer (TGA), and mechanical tester. For PEG/MC composite membranes, the addition of PEG had some effects on the transparency of membranes. As the PEG content reaches 20% (mass fraction), the composites exhibited phase change energy storage capacity. When PEG content increase further, the fusion or solidification enthalpies of the composites raised gradually. The mechanic tests displayed that the fracture strength and elastic modulus of the PEG/MC composites reduced as the PEG loadings increased. While the elongation at break increased first and then decreased. The novel PEG/MC CPCM exhibited suitable thermal performances for latent heat energy storage.

Synthesis and characterization of polyethylene glycol/modified attapulgite form-stable composite phase change material for thermal energy storage

Attapulgite with a nanoporous structure is an excellent supporting material to solve leakage of polyethylene glycol (PEG). However, when raw attapulgite is used as a supporting material, the latent heat storage capacity of PEG/ raw attapulgite form stable composite phase change material (FSCPCM) cannot be fully utilized. In this work, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (KH792) was initially modified attapulgite with amino groups firstly. A new form stable composite phase change material (FSCPCM) was prepared by adsorbing PEG into this modified attapulgite (N-ATP). The pore structure, leakage and thermal energy storage performance of this FSCPCM were investigated. Those results indicated that, compared to raw attapulgite, using N-ATP as a supporting material improved the crystallinity of PEG in the FSCPCM. Due to this improvement, the latent heat of the FSCPCM was significantly enhanced accordingly. Differential Scanning Calorimetry (DSC) measurements showed the latent heat of the PEG/N-ATP FSCPCM increased by 86.7% from the PEG/raw attapulgite FSCPCM and was close to the theoretical latent heat. Thermal conductivity analyses indicated the thermal conductivity of the PEG/N-ATP FSCPCM improved relative to of PEG. The thermogravimetric analysis (TGA), leakage testing and thermal cycling tests indicated that the PEG/N-ATP FSCPCM also had good thermal reliability, good thermal stability and leakage-proof performance. Moreover, relative to PEG/raw attapulgite FSCPCM, cement incorporated PEG/N-ATP FSCPCM has better heat storage capacity and strength.

Coal-based ultrathin-wall graphitic porous carbon for high-performance form-stable phase change materials with enhanced thermal conductivity

Creating coal-based new materials and finding their new applications are important for sustainable chemistry and engineering of coals. Here, we prepared a new kind of coal-derived three-dimensional graphitic porous carbon (denoted as GPC) for form-stable composite phase change materials. The ultrathin graphitic walls of this material enhanced thermal conductivity and shape stability. This hierarchical porous material exhibits a specific surface area of 1351 m2·g−1, which is rarely achieved in coal-derived carbons. It provides a high loading capacity of solid-liquid phase change materials (e.g., paraffin) with shape stability and high specific thermal storage density. The loaded 90 wt% paraffin@GPC composite achieved a reversible melting enthalpy of 187.4 kJ·kg−1, standing for a 7.8% increase than the theoretical value calculated from the loading amount. In addition, the highly porous GPC provides abundant sites for solidification nucleation of paraffin and therefore obtains high endo-/exo-thermal stability. The thin graphitic walls of GPC render the 90 wt% composite with an enhanced thermal conductivity of 0.58 W·m−1·K−1, which is beneficial to deliver rapid thermal transfer from outside in. The structural and thermal properties of this low-cost coal-based GPC reveal new potential applications for thermal storage.

Polyethylene Glycol Based Form Stable Composite Phase Change Material: A Review

In the present study polyethylene glycol based form stable composite phase change materials have been reviewed. Due to different molecular weight of polyethylene glycol, it contains different melting temperature. So, it can be used at various engineering applications. But, less thermal conductivity and leakage during phase transformation hampers the utilization of polyethylene glycol. To overcome these huddles various researchers develops form stable composite kind of phase change material with the incorporation of porous material and thermal conductivity enhancing material. Thermal, physical and mechanical properties of the composite phase change materials were investigated by the different authors. A number of results indicated that with addition of different form stabilized material the thermal, chemical and mechanical properties have been improved.

Lauric acid/bentonite/flake graphite composite as form-stable phase change materials for thermal energy storage

The main purpose of this paper was to synthesize a novel form-stable composite phase change material (PCM). Herein, bentonite-based PCMs were synthesized by impregnating Na-bentonite clay with lauric acid (LA) through a vacuum impregnation method. Flake graphite (FG) was used to enhance the thermal conductivity of the composite PCMs. In addition, FG also helped block the leakage of the PCMs. It is worth noting that with the addition of FG, the period of melting and solidifying of composite PCMs were decreased to some extent. Meanwhile, the thermal conductivity of the PCMs has been obviously improved. Moreover, the synthesized composite PCM exhibited a favorable performance of reliability after 200 thermocycling test. Hence, this study showed that the developed composite PCM has the potential to be applied in thermal energy storage systems.

A high heat storage capacity form-stable composite phase change material with enhanced flame retardancy

A high heat storage capacity form-stable composite phase change material (CPCM) with enhanced flame retardancy that integrated modified glass fibers with form-stable PCM was proposed. The modified glass fibers were wrapped by a composite flame retardant coating. The thermal and flame retardant properties of the CPCM were measured and compared to other CPCM samples. The results of vertical burning test indicated that the glass fibers improved the mechanical properties of the CPCM and prevented it from fracturing during the burning process. The modified glass fibers could further improve the flame retardancy of CPCM, and V-0 burning rating was achieved while the content of paraffin was maintained at 70 wt%, which means the proportion of flame retardants could be reduced. TGA results showed that the modified glass fibers could enhance the thermal stability and retard the degradation process of the CPCM, and the char residue was increased to 15.3%. Thermal cycling results indicated that the CPCM has good thermal reliability. The results of cone calorimeter test indicated that the peak heat release rate (PHRR) of flame retardant form-stable CPCM dropped by 58.8%, and the combustion rate could be greatly slowed down due to the protection of carbon layers formed by modified glass fibers. In addition, the thermal conductivity of CPCMs were greatly enhanced and the CPCM has good thermal reliability.

Preparation and Properties of Lauryl Alcohol-Caprylic Acid Eutectics/Activated Charcoal Composites as Shape-stabilized Phase Change Materials for Cold Energy Storage

A novel form-stable composite phase change materials for cold energy storage were prepared using physical blending adsorption method. In the shape-stabilized composites, lauryl alcohol (LA) and caprylic acid (CA) were employed as phase change materials, which were blended together at specific mass ratio based on theoretical calculations. Activated charcoal (AC) was selected as supporting material due to its advantages like large specific surface area and high thermal conductivity. The composites were characterized by field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectrometer (FT-IR), differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA). The results of FE-SEM and FT-IR displayed that the eutectics of LA and CA was well absorbed and dispersed homogeneously into the porous network structure of the AC and the melted eutectics was not easy to leak from the reticular structure. Moreover, there was only physical absorption between the eutectic mixture and AC. The results of DSC and TGA indicated that phase change temperature and latent heat of the prepared composites increased with the increase of the binary eutectics mass ratio and AC can enhance the thermal stability of composites. The composites with the mass ratio 60% of the eutectics melted at – 0.21 ℃ with a latent heat enthalpy of 28.08 J/g and solidified at – 2.33 ℃ with a latent solidification enthalpy of 29.70 J/g. The prepared composites will contribute to cold energy storage of low temperature range.

Alkylated Nanofibrillated Cellulose/Carbon Nanotubes Aerogels Supported Form-Stable Phase Change Composites with Improved n-Alkanes Loading Capacity and Thermal Conductivity.

The exploitation of phase change materials (PCMs) with excellent shape stability, considerable latent heat storage capacity, and superior thermal conductivity is essential for their applications in heat storage and thermal regulation. Here, form-stable composite PCMs based on n-octacosane, nanofibrillated cellulose (NFC), and carbon nanotubes (CNTs) were successfully obtained by impregnating n-octacosane into the alkylated NFC/CNTs hybrid aerogels. The three-dimensional interconnected porous aerogels could adequately support the melted n-octacosane and prevent the leakage problem due to strong capillary force and surface tension. After treatment with alkylated modification, the affinity between NFC/CNTs aerogels and n-alkanes was significantly improved, resulting in excellent shape stability, improved thermal reliability, and high n-alkanes loading capacity for the as-prepared composite PCMs. The differential scanning calorimetry analysis showed that composite PCMs based on the alkylated NFC/CNTs aerogels exhibited an extremely high phase change enthalpy ranging from 250.9 to 252.9 J/g. Furthermore, the thermal conductivity and photothermal conversion and storage efficiency of the synthesized PCMs were effectively enhanced by the introduction of CNTs. Thus, the synthesized composite PCMs exhibit considerable potential for practical application in heat storage and thermal regulation.

Wood-based composite phase change materials with self-cleaning superhydrophobic surface for thermal energy storage

Form-stable composite phase change materials, as thermal energy storage technology, show great promise for reducing energy consumption and relieving current energy shortage problems. However, porous supporting materials and most phase change materials are hydrophilic and hygroscopic, which cause crack-formation at the interfaces between supporting materials and phase change materials and decrease in thermal energy storage capacity of composite phase change material in wet or humid environment. There are almost no reports concerning this topic. Herein, form-stable and superhydrophobic composite phase change materials are fabricated by spraying superhydrophobic coating on the surface of composite phase change materials, in which delignified wood acts as a supporting material to protect against liquid leakage of 1-tetradecanol. The superhydrophobic composite phase change materials possess large water contact angle of 155° and superhydrophobic stability at 20–100 °C and pH 3–12, which prevents supporting materials and phase change materials from contacting with moisture in wet environment. In addition, the superhydrophobic composite phase change materials exhibit large latent heat of fusion (125.40 J/g), 29.58 J/g higher than that of composite phase change materials without superhydrophobic coating in wet environment. Moreover, the superhydrophobic composite phase change materials possess excellent thermal reliability and stability, efficient solar-to-thermal energy conversion and self-cleaning property, which are potential in the application of advanced energy-related devices and systems for thermal energy storage in wet or humid environment.

Form-Stable Phase-Change Composites Supported by a Biomass-Derived Carbon Scaffold with Multiple Energy Conversion Abilities

The integration of conductive carbon supports with organic phase-change materials (PCMs) enables the development of energy conversion and thermal energy storage systems. Herein, we propose a facile...

Highly thermally conductive and flexible phase change composites enabled by polymer/graphite nanoplatelet-based dual networks for efficient thermal management

Dual polymer and aligned graphite nanoplatelet networks enable highly thermally conductive, flexible, leakage-proof and form-stable phase change composites.

Bioinspired roll-to-roll solar-thermal energy harvesting within form-stable flexible composite phase change materials

Roll-to-roll charging of flexible composite phase change materials enables fast solar-thermal energy harvesting within bulk storage media.

Flame-retardant and form-stable phase change composites based on black phosphorus nanosheets/cellulose nanofiber aerogels with extremely high energy storage density and superior solar-thermal conversion efficiency

Flame-retardant PCMs with high energy storage density and superior solar-thermal conversion efficiency were fabricated by impregnating n-octacosane into CNF/BP aerogels.

Light absorptive polymeric form-stable composite phase change material for thermal storage

Light absorptive polymeric form-stable composite phase change tablet (RGO-PARB/MA) was prepared by dip-coating myristic acid (MA) tablets into layers of polymer coating solution with reduced graphene oxide (RGO). RGO serves as light absorptive material to harvest sunlight and converts it to thermal energy to be stored in PCM. Ultraviolet (UV)-Visible absorption analysis showed that RGO absorbs UV and visible light at the absorption peak of 255 nm. In this study, a new in-house experimental setup was also developed to quantitatively measure stored heat energy, solar energy conversion, and storage efficiency in the outdoor environment. RGO-PARB/MA tablet with 1.5 wt% RGO loading had the highest amount of stored heat energy which was 48.91% higher than tablet without RGO. The average solar energy conversion and storage efficiency of 1.5 wt% RGO-PARB/MA tablet was about 21%. The melting temperature and latent heat of 1.5 wt% RGO-PARB/MA tablet were 54.79 ± 0.07 °C and 119.91 ± 6.67 J/g, respectively. Thermal cycle test shows that the composite phase change material has good thermal durability, withstanding up to 1000 thermal cycles (2.7 years) with changes in thermal properties less than 2%.

Form-stable phase change materials based on delignified wood flour for thermal management of buildings

In this work, form-stable phase change composites (PCCs) was prepared based on wood flour (WF), the by-product of timber industry, via delignification and impregnation with myristyl alcohol (MA). After delignification, the micro-channel structure inherited from wood was still maintained and unblocked in delignified wood flour (dWF), which are beneficial to accommodate and restrict solid-liquid phase change materials (PCMs). The dWF/MA PCCs exhibit excellent leakage-proof properties even at temperature much higher than the melting point of MA and high phase change enthalpy. The dWF/MA PCCs were further used to fabricate composite boards by bonding with urea–formaldehyde (UF) resin. The temperature management effect of dWF/MA/UF boards was tentatively demonstrated through constructing building models and measuring the inner temperature-time curves. This work provides a promising way to fully utilize and functionalize WF and broad its application in energy-related areas.

Preparation and thermal property analysis of a novel phase change heat storage material

Hydrated salt of aluminium potassium sulfate dodecahydrate (APSD)/expanded graphite (EG) form-stable composite phase change material (PCM) has been prepared. Hydrated salt of aluminium potassium sulfate dodecahydrate used as the PCM was firstly modified by using nucleator and thickener with the aiming at solving the supercooling and phase separation. Sulfurized EG is selected as supporting matrix to overcome leakage and low thermal conductivity of MAPSD. Furthermore, hydrophilic and hydrophobic groups on the surface of the expanded graphite is oriented by carrying out titanate coupling agent, which could restrict the volatilization of crystal water and solve the poor cyclic stability problems of APSD. The thermal performance of modified APSD (MAPSD) and modified EG (MEG)/MAPSD composite PCMs are tested and analyzed by using Differential Scanning Calorimeter (DSC), Hot Disk Thermal Constant Analyzer and a small-scale experimental device. The DSC analysis showed that the melting enthalpy of form-stable composite PCM containing 80 wt% APSD and MAPSD are 473.52 and 641.75 J/g, and their corresponding melting points are 84.39 and 84.34 °C, respectively. The 100 times melt-freeze cyclic tests revealed that the mass of MAPSD decreases by 45.57%. However, the mass of MEG/MAPSD composite PCMs decreases by only 7.91% when the sample density (ρ) of 900 kg/m3 and mass fraction of MEG with 20%, which could still maintain its original shape perfectly without any change. What’s more, the effective thermal conductivity of MEG/MAPSD composite PCM (6.157 W/(m·K)) is about 11 times higher than that of pure APSD (0.55 W/(m·K)) and Agari-Uno model is used to predict the thermal conductivity of composite PCMs with different MEG contents. The average deviation is only 3.91% between experimental and predicted value. All the results indicate that the form-stable MAPSD/MEG composite PCMs can be considered as high-performance latent heat storage materials and the great potential for practical application in solar thermal utilization.

Hydrophilic modification of expanded graphite to develop form-stable composite phase change material based on modified CaCl2·6H2O

Cold energy storage using phase change materials (PCMs) in air-conditioning system is a favorable solution to the improvement of energy efficiency. In this work, the hydrophilic modification of EG through TiO2 coating was conducted to improve the compatibility of EG with modified CaCl2·6H2O PCM. Subsequently, the compressed modified EG (MEG) block was immersed into the melted modified CaCl2·6H2O to develop form-stable composite PCM. The results of contact angle and adsorption capacity tests confirmed that MEG possessed an enhanced hydrophilicity and improved adsorption property for modified CaCl2·6H2O PCM in comparison to EG. The results of SEM and pore analysis revealed that MEG still retained its inherent mesopore structure, contributing to the adsorption of MEG on the melted modified CaCl2·6H2O. The obtained composite PCM melted at 10.67 °C with the melting enthalpy of 88.39 J/g and a negligible supercooling degree (0.18 °C) as well as the enhanced thermal conductivity (8.831 W m−1K−1). Besides, the composite PCM exhibited a good thermal stability. The modified CaCl2·6H2O/MEG composite PCM shows good application prospects in cold energy storage, providing a new routine for improving the compatibility of EG with salt hydrates.

Multifunctional wood based composite phase change materials for magnetic-thermal and solar-thermal energy conversion and storage

In recent years, multifunctional form-stable composite phase change materials have been the research focus in the field of thermal energy storage. In this work, magnetic wood-based composite phase change materials are prepared via the impregnation of a compound of 1-tetradecanol and Fe3O4 nanoparticles into delignified balsa wood. Delignified balsa wood, which has porous structure with low density and high loading content of over 80%, was used as a supporting material. The addition of Fe3O4 nanoparticles provides an excellent magnetic property and improves the solar-to-thermal conversion efficiency of the composite. Benefiting from the magnetothermal effect, the magnetic wood-based composite phase change materials can be heated under an alternating magnetic field. Also, the magnetic wood-based composite phase change materials exhibit large latent heat (179 J/g), excellent thermal reliability after 100 heating-cooling cycles, and outstanding shape stability. And they have good thermal stability below 112 ℃. Considering the easy processing and excellent property, the magnetic wood-based composite phase change materials have great prospect in multifunctional thermal energy storage in practical applications.