Leakage Of Phase Change Materials Research Articles

Insights into effect of lignocellulosic biomass framework types on bio-based shape stable composite phase change materials

The utilization of biomass waste as framework materials to inhibit the leakage of phase change material (PCMs) has gained widespread attention. In this work, three new kinds of shape stable composite phase change materials (sscPCMs) were prepared which combined with stearic acid (SA) and peanut shell powders (PSP), poplar wood powders (PWP), and corn straw powders (CSP), respectively. The influence of lignocellulosic biomass types on the thermal energy storage performance of sscPCMs was studied by comparing three types of sscPCMs. The research results indicated that SA/CSP exhibited superior properties in terms of load capacity and thermal energy storage performance. According to leakage experiments the load capacity of SA/PSP, SA/PWP and SA/CSP was 31.67 %, 44.69 %, and 50.09 %, respectively. The phase change latent heat of SA/PSP, SA/PWP, and SA/CSP was 55.78, 84.27 and 98.47 J/g, respectively. In addition, the relationship between biomass component content and load rates was studied. The results showed that there was a positive correlation between the loading rates of SA and the ratio of holocellulose (cellulose + hemicellulose) to lignin. The results provided a promising approach for the selection of lignocellulosic biomass framework materials.

Multiscale Porous Architecture Consisting of Graphene Aerogels and Metastructures Enabling Robust Thermal and Mechanical Functionalities of Phase Change Materials

AbstractPassive thermal energy storage systems using phase change materials (PCMs) are promising for resolving temporal‐spatial overheating issues from small‐ to large‐scale platforms, yet their poor shape stability due to solid–liquid transition incurs PCM leakage and weak resistance against mechanical disturbance, limiting practical applications. While foam‐stable templates for PCMs have shown complement, they reveal massive leakage and collapse of liquefied PCMs under external loads or impacts. Herein, a multiscale porous architecture consisting of graphene aerogels (GAs) and meta structures enabling robust thermal‐mechanical functionalities of PCMs (3D‐MPGA) toward sustainable phase change thermal energy storage composites is reported. 3D‐printed mechanical metamaterials employing octet‐truss cells provide supportive strength and directionally‐assisted leakage reduction, while GAs serve as porous templates with surface‐interfacial contacts, thereby fixing paraffin wax as PCM inside their nano/micropores. The 3D‐MPGA shows intrinsic thermal characteristics of bulk PCMs, and improved thermal‐mechanical‐chemical stability, confirmed by long‐term heating‐cooling cycle tests over 10 h. Moreover, it exhibits highly reinforced strength (200–5000%) within a low density across ambient and melting temperatures, and maintains original shapes in the liquefied PCMs without severe leakage, against external loads. This work inspires rational strategies for advancing robust thermal‐mechanical functionalities for PCM‐based thermal energy storage systems.

High thermal conductivity composite phase change material with Zn2+ metal organic gel and expanded graphite for battery thermal management

Phase change materials (PCMs) with promising potential thermal energy is stored and released much thermal energy during phase change process, which has greatly prospect in building energy conservation, waste heat recovery, energy storage, electrical vehicles (EVs) and other fields. Nevertheless, the low thermal conductivity and easy leakage of PCM is still a challenge to restrict its fasting development. Traditional supporting material is hard to reconcile antileakage and thermal conductivity of composite PCM (CPCM). Herein, the polyethylene glycol (PEG) with three-dimensional Zn2+ metal–organic gel (ZnHGL) as high-thermal conductivity support framework, styrene–butadiene–styrene block copolymer (SBS) and expanded graphite (EG) has been designed and prepared PZSE with high thermal conductivity, accompany with double transferring heat and supporting network structure. In contrast with pure PEG, the thermal conductivity of PZSE2 is increased by obvious 8.7 times when Zn2+ metal–organic gel and SBS with the proportion of 1:1, the mass maintenance rate and latent heat storage capacity are increased to 99.5 % and 103.64 J/g, respectively. Further, the thermal imaging camera indicate that PZSE2 exhibit a stable temperature-regulation property, which is benefited to extend the time to adjust the temperature. Additionally, the maximum temperature and temperature differential of the battery module with PZSE2 can be maintained within 60 °C and 6 °C, respectively, even at 1.5C discharge rate after ten cycling process. It indicates that the battery module with PZSE2 has optimum thermal management effect. Therefore, PZSE with metal–organic gel and EG can provide a promising candidate utilization in thermal regulation of EVs and energy storage.

A novel cement mortar comprising natural zeolite/dodecyl alcohol shape stable composite phase change material for energy effective buildings

Investigations into Phase Change Materials (PCMs) for heat storage in facilities have gained significance, contributing to indoor temperature regulation, decreased energy usage, and improved building efficiency, thereby supporting sustainability initiatives. However, the issue of PCM leakage during the heating phase has constrained its thermal energy storage (TES) prospective at large scaled-practices. Addressing this concern, the present study emphases on elimination of the leakage problem of dodecyl alcohol (DA) as a PCM with appropriate melting temperature for building TES request by its impregnating into the natural zeolite (NZ) as a low cost host matrix. In the second stage of the work, using the developed shape stable-NZ/DA (SS-NZ/DA) composite PCM in cement mortar instead of sand, novel cementitious mortars with enhanced thermal properties were created by incorporating different weight percentages (25 %, 50 %, 75 %, and 100 %) compared to the mortar comprising NZ. Experimental works were carried out to analyze the shape-stability, TES features, cycling TES stability and thermal endurance of the SS-NZ/DA composite as well the physical properties, mechanical strength, and solar temperature regulation performance of the SS-NZ/DA included mortars. The SS-NZ/DA demonstrated the melting enthalpy of 107.5 J/g at 19.47 °C and a freezing enthalpy of 106.1 J/g at 19.86 °C. The performance test results obtained under real weather conditions indicated that the integration of SS-NZ/DA into mortar presented maximum drop of 10 % and 9.26 % in peak indoor temperature at the SS-CPCM slab surface and the center of SS-CPCM slab-cabin, respectively, accompanied by an approximate 3-hour time delay. Mortars with SS-NZ/DA composite PCM exhibited a decreased dry unit weight (1189 kg/m3) and thermal conductivity (0.394 W/mK) while experiencing a moderate strength loss (4.5 MPa). These favorable physico-mechanical properties, TES characteristics and thermal management capability make the novel cementitious mortar containing composite PCM as an energy-efficient material for creating thermo-regulative building components. In this study, the natural, economical, and environmentally friendly nature of the NZ material used for PCM impregnation, its ability to contain a high percentage of PCM (up to 45 %) without any leakage issues, is the most fundamental and important characteristic of the composite used. The most unique feature of this composite mortar is the ability to achieve sufficient mechanical and thermal properties in cementitious mortars produced using this composite material without any leakage problems.

Studying the Improvement of Solar Collector Mechanism with Phase Change Materials

This study delves into the integration of phase change materials (PCM) in solar thermal collector systems to address this challenge. By incorporating nano encapsulated PCMs, researchers have mitigated concerns surrounding PCM leakage, revolutionizing the potential of solar collector systems to elevate energy efficiency, diminish carbon emissions, and yield manifold benefits. This article comprehensively investigates the design and utilization of solar phase change energy storage devices and examines the transformative impact of employing nano-coated phase change materials (Nano capsules) to augment solar collector performance. The integration of paraffin-based PCM and the insulation of the collector system have been crucial in optimizing heat retention and operational efficacy. The composition of the PCM involves a balanced blend of octadecane phase-change particles and water as the base fluid, designed to maximize thermal performance. Analysis of the experimental findings demonstrates the dynamic thermal behavior of the nano encapsulated phase change material, revealing distinctive temperature profiles about fluid dynamics and absorbent characteristics. Notably, the study emphasizes the nuanced trade-offs associated with the conductivity and melting temperature of the Nano encapsulated PCM, yielding valuable insights into energy storage capacity limitations and thermal performance variations throughout diurnal cycles. Central to the investigation, the optimal nanoparticle proportion is elucidated, shedding light on its pivotal role in modulating PCM performance. Furthermore, findings underscore the complex interplay between nanoparticle volume fraction and thermal fluid temperature, providing critical perspectives on optimizing PCM-enhanced solar collector systems.

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.

High value utilization of waste peanut shell: Prepared novel shape stable composite phase change materials with high thermal conductivity

To address the leakage and low thermal conductivity issues of phase change materials (PCMs), this study aims to prepare high thermal conductivity shape stable composite phase change materials (sscPCMs) using waste peanut shell. Employing pyrolysis technology, waste peanut shell has been successfully converted into high-performance framework materials. In addition, it also compared the thermal energy storage performance of shape stable composite stearic acid/peanut shell biochar (ss-cSA/PSC) with that of shape stable composite stearic acid/peanut shell (ss-cSA/PS). Excitingly, the thermal energy storage performance of ss-cSA/PSC has been significantly improved. Specifically, the thermal conductivity of ss-cSA/PSC reached 0.527 W/(m·K), which is 3.2 times higher than that of pure SA and 2.4 times higher than that of ss-cSA/PS. In addition, the phase change latent heat of ss-cSA/PSC can reach 70.59 J/g, which is 27.2% higher than that of ss-cSA/PS. The high thermal conductivity and phase change latent heat highlighted its significant superiority in the field of thermal energy storage. Furthermore, ss-cSA/PS and ss-cSA/PSC have been characterized by SEM, FTIR, XRD, and TGA. The results indicated that both two kinds of sscPCMs have excellent chemical compatibility, thermal reliability, and thermal stability. In summary, PSC is an economical, environmentally friendly, and sustainable framework material which used to prevent the leakage of PCMs and improve the thermal performance.

Experimental Study and Mechanism Analysis of Paraffin/Sisal Composite Phase Change Energy Storage Fiber Prepared by Vacuum Adsorption Method.

Sisal fiber exhibits a fibrous and porous structure with significant surface roughness, making it highly suitable for storing phase change materials (PCMs). Its intricate morphology further aids in mitigating the risk of PCM leakage. This research successfully employs vacuum adsorption to encapsulate paraffin within sisal fiber, yielding a potentially cost-effective, durable, and environmentally friendly phase change energy storage medium. A systematic investigation was carried out to evaluate the effects of sisal-to-paraffin mass ratio, fiber length, vacuum level, and negative pressure duration on the loading rate of paraffin. The experimental results demonstrate that a paraffin loading rate of 8 wt% can be achieved by subjecting a 3 mm sisal fiber to vacuum adsorption with 16 wt% paraffin for 1 h at -0.1 MPa. Through the utilization of nano-CT imaging enhancement technology, along with petrographic microscopy, this study elucidates the mechanism underlying paraffin storage within sisal fiber during vacuum adsorption. The observations reveal that a substantial portion of paraffin is primarily stored within the pores of the fiber, while a smaller quantity is firmly adsorbed onto its surface, thus yielding a durable phase change energy storage medium. The research findings contribute to both the theoretical foundations and the available practical guidance for the fabrication and implementation of paraffin/sisal fiber composite phase change energy storage mediums.

Thermal Performance of Lignocellulose’s By-Product Wallboards with Bio-Based Microencapsulated Phase Change Materials

The growing availability and decreasing cost of microencapsulated phase change materials (PCMs) present an opportunity to develop innovative insulation materials for latent heat energy storage. By integrating PCMs with traditional insulation materials, it is possible to enhance the thermal capacity of a building by up to 2.5-times, virtually without increasing the building’s mass. To improve buildings’ indoor structural performance, as well as improving their energy performance, microencapsulated PCMs are integrated into wallboards. The integration of microencapsulated PCMs into the wallboard solves the PCM leakage problem and assures a good bond with the building materials to achieve better structural performance. The novelty of this research is the application of encapsulated phase change material dispersion and technology for its incorporation into the structure of hemp shives and longitudinally milled wood chip-based insulation boards, using cold pressing technology to reduce the energy consumption of board production. As a result, low-density insulation boards for indoor application were produced by varying their structure and the amount of phase change materials in the range of 5% to 15% by board mass. The obtained board prototypes can be used as microclimate and thermoregulation elements of interiors, as well as functional aesthetic elements of interior design.

A Dual Encapsulation Strategy for High-Temperature Micro PCM Particles with High Cyclic Durability.

Addressing critical issues such as high-temperature corrosion, leakage, degradation, and subpar cyclic performance is imperative for phase change materials (PCMs), prompting the development of appropriate encapsulation techniques to surmount these challenges. In this study, a dual encapsulation strategy is proposed for high-temperature micro PCM particles. Al-Si core is microencapsulated via the "solvent evaporation-heating curing" method. Subsequently, TiO2 is employed as the skeleton material for form-stable encapsulation of PCM microcapsules by "cold pressed sintering". Detailed analysis of the crystalline phase transformation mechanism in the sintering synthesis pathway of TiO2 underscore its potential as a robust structural material with exceptional thermal stability. Furthermore, the incorporation of hexagonal boron nitride (hBN) results in a substantial enhancement of the thermal conductivity of the composites, increasing by 121.1-131.3%. The prepared form-stable phase change microcapsules (FSPCMs) are subjected to 5000 thermal cycles in the air atmosphere. There is no observed PCM leakage or composite ruptures in the FSPCM. Moreover, the oxidized mass gain is merely 3.3%, signifying exceptional oxidation resistance. Thermophysical analysis indicates that FSPCM can retain 91.3% of the enthalpy after 2000 cycles, with over 80% preservation after 5000 cycles, underscoring its remarkable cyclic thermal durability.

Innovative flexible thermal storage textile using nanocomposite shape-stabilized phase change materials

A novel flexible thermal storage system based on organic phase change materials (PCMs) deposited on a non-woven polyester (PET) substrate is described in this article. Thermally regulating effects were created via encapsulation of polyethylene glycol (PEG) in carbon nanofibers (CNFs) to manufacture a shape-stable phase change material (SSPCM). Improvement in the thermal conductivity (TC) of the system was obtained by incorporating reduced graphite oxide nanoparticles (rGONP) into the CNFs. A new method was applied to load and secure the manufactured SSPCMs on the fibrous substrate so that an acceptable level of flexibility was preserved (change in bending length less than 30%). The sample performance was evaluated by measuring its thermal properties. The physical properties, wash fastness, abrasion resistance, morphology, and PCM leakage of the samples were also assessed. The results point to a good thermal storage ability of the samples with characteristic phase change temperature ranges of 30.1–31.4 °C and 19.2–24.3 °C for melting and freezing, respectively, and a latent heat of 8.9–22.9 J g−1 for meting and 11.2–21.4 J g−1 for freezing. The use of the CNF-rGONP for PEG enhanced the TC of the system by 454%, thus providing a rapid thermal response, and efficiently prevented the leakage of PEG. Finally, the loading and fixation method on the non-woven substrate allowed an acceptable level of durability with less than 4% of weight loss during washing and abrasion tests. This system provides a promising solution for rapid response, flexible thermal storage wearables.

Development of artificial leak-free phase change material (PCM) aggregates using emulsion technique, cementless binder, and cold-bonded pelletization

The present study developed new leak-free artificial PCM aggregates using an emulsion technique, cementless binder, and cold-bonded pelletization (hereafter, PCM-surfactant-aggregate) and significantly increased the PCM quantity in aggregates without PCM leakage, which was demonstrated from differential scanning calorimetric (DSC) and thermogravimetry (TG) results. The PCM-water-emulsion was produced by using a non-ionic surfactant, Pluronic P123, and used as mixing water to produce cementless artificial aggregates using Ca(OH)2-Na2CO3-activated fly ash and cold-bonded pelletization. The produced artificial PCM-surfactant-aggregates showed no material separation during preparation and no visual PCM leakage on the surface and were lightweight aggregates in terms of compressive strength (ASTM C330). In the concrete testing results, the 28-day compressive strength was 18.1 MPa when all fine and coarse aggregates were replaced with artificial PCM-surfactant-aggregates and the thermal conductivity decreased with increasing aggregate content. The testing on the heated concrete specimens having PCM-surfactant-aggregates indicated no PCM leakage, no dimensional change, and no strength reduction due to the PCM phase transition from solid to liquid. Overall, the concrete containing PCM-surfactant-aggregates showed an increase in the lowest temperature and a decrease in the highest temperature in the temperature profile of the indoor space in the dynamic heat flow test.

Soft-hard complex microsphere strategy to construct high-temperature form-stable phase change material for melt-spun temperature-regulating fibers

Phase change materials (PCMs) have excellent temperature regulation ability and are usually used in smart wearable devices. However, PCMs prepared by traditional methods cannot be applied to high-temperature (>230 °C) melt spinning, and leakage of PCM is prone to occur during spinning. This work successfully prepared a series of PCMs with high thermal form-stable by the strategy of capillary adsorption of inorganic porous materials and surface microchemical crosslinking and proved that it can effectively solve the above-mentioned problems of high-temperature melt-spinning temperature regulating fibers. This PCM prepared by combining porous SiO2 adsorption and chemical crosslinking of polyethylene glycol derivatives exhibits excellent heat resistance at 130 °C for 40 min. In addition, polycaprolactam (PA6) was selected as the polymer matrix, and PA6-based temperature regulating fibers with excellent temperature regulating functions were prepared. The thermal response time of the fabric prepared from this fiber in the hot environment is 782 s, and the maximum temperature difference is 5.4 °C. Moreover, the exothermic duration in cold environment is 427 s, and the maximum temperature difference is 2.3 °C. This shows that the prepared temperature regulating fiber has good application prospect in heat-regulating devices.

Backfill thermal properties improvement using granular phase change materials and graphite

Phase change materials (PCMs) are ideal for thermal energy storage due to latent heat release or absorption at target temperatures. Hence, adding PCMs into backfill materials of ground heat exchangers for example, can enhance the borehole thermal energy storage capacity and the corresponding shallow geothermal system performance. However, the heat transfer efficiency between the borehole and surrounding ground might be reduced because of the low thermal conductivity of PCMs. Incorporating additives with high thermal conductivity can reduce the lowering effect of PCMs on the overall thermal conductivity of the mixture while maintaining a desirable thermal capacity. This work mixes encapsulated PCMs (EPCMs), graphite and recycled glass fines, aiming to develop green backfill materials with excellent thermal properties. The heat capacity and thermal conductivity of the mixtures with different fractions of the components are measured in a laboratory. The measured data agree with simulated results. Better thermal properties can be achieved with specific fractions of components, and the findings could help geothermal systems design for better energy utilisation.
 Geothermal energy is one of the promising renewable energy sources and its utilisation can be an alternative to fossil fuels. A geothermal system requires a ground source heat exchanger with pipes installed inside a borehole, and backfill materials filling the gap between the pipe heat exchanger and the ground. Thus, the thermal properties of backfill materials are essential to the geothermal energy extraction process and influence the corresponding shallow geothermal system performance [2]. PCMs are used to improve the thermal storage capacity of backfill materials because they can absorb and release heat at a relatively constant temperature [1]. To avoid problems of leakage and volume change of PCMs during a phase change, encapsulated PCMs (EPCMs) are better suited in backfill materials [5]. However, mixtures including PCMs may hinder heat transfer because of their low thermal conductivity. Therefore, other additives with high thermal conductivity can be used to resist the low heat transfer rate [3]. Even though the thermal properties of backfill materials are fundamental to the geothermal energy extraction process, their dependence on the amount of added PCMs and other additives has not been investigated yet. This work mixes EPCMs, graphite and recycled glass fines, aiming to develop green backfill materials with excellent thermal properties. The heat capacity (), thermal conductivity () and thermal diffusivity () of the mixtures with different fractions of the components are measured in a laboratory.
 SEM images of materials used, recycled glass fines, EPCMs and graphite, are shown in Figure 1(a). Cylindrical containers with a diameter of 44 mm and a height of 57 mm are used to prepare samples of mixtures. Each sample has the controlled volume fractions of components indicated by Figure 1(b) while keeping a constant overall porosity of 0.47. A decagon KD2 Pro thermal analyzer with a dual thermal needle measures the thermal properties of samples kept at 4 °C when EPCMs are in the solid phase and 45 °C when EPCMs are in the liquid phase. The geometrical mean model is used for theoretical estimations of values for comparison against experimental results [4].
 
 The thermal conductivity () of the mixtures increases with increasing graphite volume while decreasing with increasing EPCMs volume, as shown in Figure 1(c). The difference between under solid EPCMs and liquid EPCMs is limited. The heat capacity () rises with increasing EPCMs volume but declines with the increase of graphite volume, and it is higher when EPCMs are liquid than solid. It can be observed that a trade-off between the improvement of and the reduction of exists. Hence, the thermal diffusivity (), which depends on the ratio of to , is also investigated as presented in Figure 1(d). It decreases with the increase of EPCMs volume but grows with increasing graphite volume. Besides, it is higher under solid EPCMs than that under liquid EPCMs. This indicates the backfilling materials have a faster thermal response to the change of surrounding temperature under solid EPCMs.

Advancements in Phase Change Materials in Asphalt Pavements for Mitigation of Urban Heat Island Effect: Bibliometric Analysis and Systematic Review.

This research presents a dual-pronged bibliometric and systematic review of the integration of phase change materials (PCM) in asphalt pavements to counteract the urban heat island (UHI) effect. The bibliometric approach discerns the evolution of PCM-inclusion asphalt research, highlighting a marked rise in the number of publications between 2019 and 2022. Notably, Chang'an University in China has emerged as a leading contributor. The systematic review addresses key questions like optimal PCM types for UHI effect mitigation, strategies for PCM leakage prevention in asphalt, and effects on mechanical properties. The findings identify polyethylene glycols (PEGs), especially PEG2000 and PEG4000, as prevailing PCM due to their wide phase-change temperature range and significant enthalpy during phase transitions. While including PCM can modify asphalt's mechanical attributes, such mixtures typically stay within performance norms. This review emphasises the potential of PCM in urban heat management and the need for further research to achieve optimal thermal and mechanical balance.

Preparation and Experimental Study of Phase Change Materials for Asphalt Pavement.

This study aimed to address the issue of high-temperature challenges in asphalt pavement by developing two types of phase change materials (PCMs) for temperature control. Encapsulated paraffin wax particles (EPWP) and encapsulated myristic acid particles (EMAP) were synthesized using acid-etched ceramsite (AECS) as the carrier, paraffin wax (PW) or myristic acid (MA) as the core material, and a combination of epoxy resin and cement as the encapsulation material. The investigation encompassed leakage tests on PCMs; rutting plate rolling forming tests; SEM, FTIR, XRD, and TG-DSC microscopic tests; as well as heat storage and release tests and temperature control assessments using a light heating device. The study revealed the following key findings. Both types of PCMs exhibited no PCM leakage even under high temperatures and demonstrated low crushing ratios during rut-forming tests. Microscopic evaluations confirmed the chemical stability and phase compatibility of the constituents within the two types of PCMs. Notably, the phase change enthalpies of EPWP and EMAP were relatively high, measuring 133.31 J/g and 138.52 J/g, respectively. The utilization of AECS as the carrier for PCMs led to a substantial 4.61-fold increase in the adsorption rate. Moreover, the PCMs showcased minimal mass loss at 180 °C, rendering them suitable for asphalt pavement applications. The heat storage and release experiments further underscored the PCMs' capacity to regulate ambient temperatures through heat absorption and release. When subjected to light heating, the maximum temperatures of the two types of phase change Marshall specimens were notably lower by 6.6 °C and 4.8 °C, respectively, compared to standard Marshall specimens. Based on comprehensive testing, EPWP displayed enhanced adaptability and demonstrated substantial potential for practical implementation in asphalt pavements.

Thermal performance enhancement of high durability alloy microencapsulated phase change material (MEPCM)/ceramic composites based on industrial graphene

Metallic phase change material (PCM)/ceramic composites have emerged as promising candidates for medium and high-temperature thermal energy storage (TES) due to their excellent performance. However, challenges associated with leakage and oxidation in metals, along with the limited thermal conductivity of ceramic matrices, restrict further performance enhancement. Herein, an alloy microencapsulated phase change material (MEPCM) is prepared as a PCM using the “double-layer coating, sacrificial inner layer” method, followed by compounding it with a ceramic matrix and industrial graphene (IG). Based on this, a novel IG/SnBi58 MEPCM/ceramic composite is prepared and its performances are investigated. The results show that the composite with 12 wt% IG exhibits optimum performance: a thermal conductivity of 5.75 W/(m·K), 86.1% higher than without IG, melting enthalpy of 73.71 J/cm3, and compressive strength of 49.38 MPa. Furthermore, the microencapsulation of alloys fundamentally solves the PCM leakage issue within the composite and enables its good component compatibility. The heat storage density reaches 399.1 MJ/m3, over 2.3 times that of traditional quartz sensible heat storage materials. Owing to the thermally expanded cavities created by “double-layer coating, sacrificial inner layer” method, the prepared MEPCM demonstrates high thermal reliability, so the composite maintains stable thermal properties and chemical structure after 500 thermal cycles. Finally, the comparative analysis reveals that the composite combines higher thermal conductivity, compressive strength, heat storage density, and thermal cycle stability than other composite heat storage materials. This work provides a new strategy to meet the demand for high-performance heat storage materials in medium-temperature TES applications.

Microencapsulated phase change material through cellulose nanofibrils stabilized Pickering emulsion templating

Phase change materials (PCMs) possess remarkable capability to store and release substantial amounts of energy during the processes of melting and crystallization across a wide temperature range, thus holding great promise in applications related to temperature regulation and thermal energy storage. Herein, to effectively address PCM leakage and enhance thermal conduction, PCM microcapsules with melamine–formaldehyde resin (MF) shell were prepared using in situ polymerization of Pickering emulsions stabilized by cellulose nanofibrils (CNFs). CNFs were selected as the stabilizers for the Pickering emulsions and as reinforcing nanofillers for the MF shell, owing to their excellent emulsifying capability, high mechanical strength, and sustainable nature. Paraffin wax (PW) was utilized as the PCM material. The resulting PCM microcapsules with MF resin shells and PW core had a diameter ranging from 2 to 4 µm. Results showed that microcapsule with the core–shell ratio of 2 (Micro-2.0) exhibited the highest latent heat of crystallization and latent heat of fusion, measuring approximately 128.40 J/g and 120.23 J/g, respectively. The encapsulation efficiency of Micro-2.0 was determined to be approximately 79.84%.

Preparation of Microencapsulated Phase Change Materials from Sulfonated Graphene Stabilized Pickering Emulsion.

Microencapsulated phase change materials (MCPCM) as a green energy storage material not only prevent leakage of phase change materials but also increase the heat transfer area of phase change materials. Extensive previous work has shown that the performance of MCPCM depends on the shell material and MCPCM with polymers, as the shell material suffers from low mechanical strength and low thermal conductivity. In this study, a novel MCPCM with hybrid shells of melamine-urea-formaldehyde (MUF) and sulfonated graphene (SG) was prepared by in situ polymerization using SG-stabilized Pickering emulsion as a template. The effects of SG content and core/shell ratio on the morphology, thermal properties, leak-proof properties, and mechanical strength of the MCPCM were investigated. The results showed that the incorporation of SG into the shell of MUF effectively improved the contact angles, leak-proof performance, and mechanical strength of the MCPCM. Specifically, the contact angles of MCPCM-3SG were reduced by 26°, the leakage rate was reduced by 80.7%, and the breakage rate after high-speed centrifugation was reduced by 63.6% compared to MCPCM without SG. These findings suggest that the MCPCM with MUF/SG hybrid shells prepared in this study has great potential for application in thermal energy storage and management systems.

Effect of two organic phase change materials on the thermal performance of asphalt pavements

ABSTRACT Higher temperature is one of the key reasons for thermal distresses in asphalt pavement. It also adds to the Urban Heat Island (UHI) effect as it influences the near-surface air temperature. To design cooler pavements, phase change materials (PCMs) can be incorporated into asphalt pavements. However, considering the negative effects of PCM leakage on the physical and rheological properties of asphalt binder, a cent-percent effective core-shell encapsulated PCM suitable for asphalt pavement applications was developed under this study. With the incorporation of two organic mixture (OM) based PCMs, i.e., OM-35 and OM-42, a peak decrease in the pavement surface temperature of 3.05 °C and 4.36 °C, respectively were observed under the field condition. Furthermore, from the long-term thermal performance assessment, it was found that the magnitude of temperature reduction depends on the phase change temperature and latent heat of PCM. The season of occurrence of the peak temperature reduction depends on the phase change temperature of the PCM. Due to PCM solidification, the increase in night-time pavement surface temperature was observed to be about half of that during day time. Further, the statistical analysis reveals that the decrease in pavement surface temperature due to PCM incorporation is significant and consistent.