While solid‐state materials are commonly classified as covalent, ionic, or metallic, there are cases that defy these iconic bonding mechanisms. Phase‐change materials (PCMs) for data storage are a ...prominent example: they have been claimed to show “resonant bonding,” but a clear definition of this mechanism has been lacking. Here, it is shown that these solids are fundamentally different from resonant bonding in the π‐orbital systems of benzene and graphene, based on first‐principles data for vibrational, optical, and polarizability properties. It is shown that PCMs and related materials exhibit a unique mechanism between covalent and metallic bonding. It is suggested that these materials be called “incipient metals,” and their bonding nature “metavalent”. Data for a diverse set of 58 materials show that metavalent bonding is not just a superposition of covalent and metallic cases, but instead gives rise to a unique and anomalous set of physical properties. This allows the derivation of a characteristic fingerprint of metavalent bonding, composed of five individual components and firmly rooted in physical properties. These findings are expected to accelerate the discovery and design of functional materials with attractive properties and applications, including nonvolatile memories, thermoelectrics, photonics, and quantum materials.
Metavalent bonding is introduced, defined in terms of physical properties, and identified in a class of inorganic solids. This includes phase‐change materials and thermoelectrics previously referred to as “resonantly” bonded. Metavalent bonding is shown to be a unique and fundamental bonding mechanism in solids: it is located between covalent and metallic interactions, but clearly distinct from both.
•PCM-cooled and PCM-heated BTMS are reviewed.•Phase change fluid (PCF), flexible phase change material (FPCM) and Hybrid cooling are analyzed.•The flammability of organic PCM needs to be solved for ...BTMS.•The stability of inorganic PCM needs to be solved for BTMS.•Various issues and challenges of BTMS based on PCM are identified.
It is known that the performance of a power battery is greatly affected by temperature. The battery pack needs an efficient thermal management system to make the power battery work in a reasonable temperature range. Battery thermal management system (BTMs) based on phase change materials (PCM), as a passive thermal management method, has the advantages of low operating cost and good temperature uniformity. This paper mainly introduces the BTMs based on PCM, including the cooling and heating system based on PCM. For the cooling system of PCM, the performance of composite phase change materials (CPCM) and its heat transfer enhancement, phase change fluid (PCF), flexible phase change materials (FPCM), and hybrid cooling systems are analyzed. For the PCM heating system, the PCM latent heat for preheating of the power battery in a cold environment has also been discussed. Finally, this paper concluded that the next research directions should focus on the improvement of thermal conductivity of PCM, flame retardancy of organic PCM, thermal stability of inorganic PCM, PCF and FPCM, and PCM-based coupled battery thermal management.
In this study, a novel hybrid composite PCM was manufactured by adsorbing octadecane into the porous supporting material based on the aluminum nitride (AlN) material, which owned high thermal ...conductivity. Meanwhile, a layer of nanocapsule PCM was coated on its surface for increasing the latent heat and achieving the PCM encapsulation. The results showed that the AlN efficiently enhanced the thermal conductivity of the composite PCM, and the addition of nanocapsule PCM further improved the stability and latent heat of the composite PCM. The composite PCM melted at 26.12 °C with a latent heat of 116.26 kJ/kg and solidified at 25.02 °C with a latent heat of 115.96 kJ/kg. In addition, the leakage problem of pure PCM was solved, and the thermal conductivity of composite PCM was 3.5 W/(m·K), which was 17.5 times of pure PCM. More importantly, the dynamic thermal performance exhibited the composite PCM as an energy storage material for buildings was able to lower the fluctuation of building temperature in winter. Therefore, the as-prepared composite PCM is a desirable candidate for building energy storage systems.
•A novel thermal enhanced composite phase change material with aluminium nitride is developed.•The proposed composite is characterized by DSC for latent heat storage.•The thermal conductivity of proposed material is improved up to 3.5 W/(m·K).•Stability performance of the proposed compound is excellent with nanocapsules covered.
This study deals with the preparation and characterization of the composites of polyethylene glycol (PEG)/the synthesized polymeric solid-solid phase change material (SSPCM) as novel form stable ...phase change material (FSPCM) for thermal energy storage. The synthesized SSPCM can play two roles in the FSPCM: the supporting material and the phase change working substance. The influence of PEG content on crystalline properties and phase change behaviors of the FSPCMs was investigated. The polarizing optical microscopy (POM) images of FSPCMs show that all FSPCMs have the spherocrystal morphology, and the spherocrystal size of SSPCM increases with the increasing of PEG percent. The results from differential scanning calorimetry (DSC) indicate that the prepared FSPCMs with different PEG contents have high thermal storage density, and the enthalpy efficiency of them is much higher than that of the traditional FSPCMs due to the synergistic phase change effect of PEG and SSPCM. The Fourier transform infrared spectroscopy (FTIR) spectrum and DSC curve of the FSPCMs after thermal cycling are almost the same as those of the original samples, which indicates that the FSPCMs have excellent thermal reliability and reusability. The work not only supplied a kind of novel FSPCMs with high performances, but also proposed a new way to solve the problem of enthalpy decline of traditional FSPCMs and synthesized polymeric SSPCMs compared with solid-liquid PCMs.
•A polymeric SSPCM was synthesized and used as the supporting material of FSPCMs.•The FSPCMs composed of SSPCM and PEG have the property of synergistic phase change.•The FSPCMs with spherocrystal have high enthalpy and good thermal reliability.•The FSPCMs have much higher enthalpy efficient than that of the traditional FSPCMs.
This paper investigates three different configurations of a hybrid battery thermal management system (BTMS) using phase change material (PCM) as passive and air coolant as active cooling system. The ...PCM surrounded the battery cell is encapsulated in three different vessel cross-sections as circular, rectangular, and hexagonal with equal volumes. Each of these BTMS consists of 12 Sony 18650 batteries with the same pack holder. The thermal management of the battery pack is examined in the course of different charging and discharging rates. Results reveal that the thermal performance of both hexagonal and circular PCM vessels show generally the same behavior. Utilization the latent heat as the passive coolant in the battery thermal management is the strong point, which results show that the circular PCM configuration is the best one. However, in the high rate of charging or discharging condition, the uniform air channel around the rectangular shape makes a more efficient cooling compared to the other arrangements.
•Investigate on the hybrid active-passive battery thermal management system (BTMS) is the main objective.•Phase change material (PCM) as passive and air coolant as an active cooling system are considered.•A transient numerical study conducted on the three different PCM encapsulation shape.•Uniform shape of PCM encapsulation (circular shape) is the thermal efficient in the passive cooling.•Uniform air channel, rectangular shape of PCM encapsulation is thermal efficient in the active cooling.
In the study, polyethylene glycol (PEG), lithium nitrate (LiNO3), and sodium sulfate (Na2SO4) were employed as the low-, middle-, and high-temperature heat storage media, respectively. A series of ...novel shape-stabilized phase change materials were tailored by a post-preparation method with previously synthesized radial-like mesoporous silica and their structural and thermal properties were characterized. The silica was synthesized through a facile self-assembly process using cetyltriethylammonium bromide as the main template and tetraethyl orthosilicate as silica precursor. The obtained phase change composites showed good shape stability and high thermal energy storage capacity. The morphology and structure of the radial-like mesoporous silica were investigated after combining with different heat storage media. These composites exhibited excellent thermal stability, chemical compatibility, and thermal reliability. The efficient silica support has opened up some new application of energy materials based on novel phase change material/silica composites, such as energy conversion and heat storage for different temperature requirements.
•Radial-like mesoporous silica sphere was prepared.•PEG/silica, LiNO3/silica and Na2SO4/silica were prepared.•“Phase change silica” has excellent thermal performance and outstanding thermal reliability and stability.
The present review is an extensive overview of the research progress obtained in the field of Phase Change Material (PCM) integrated with solar thermal applications. Solar energy has become an ...attractive method of using clean energy to eliminate the shortage and environmental drawbacks of fossil fuels but it needs energy storage to bridge the mismatch between times of energy demand and energy supply. Latent Heat Storage (LHS) in PCMs is the most suitable solution for thermal energy storage due to their high latent heat. In this review, special attention is given to recent publications in the field of PCM integrated with solar thermal applications along with the material problems and possible solutions. Finally, future directions on possible studies and applications are proposed.
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•Organic PCM shows a appropriate phase change point considering the ambient temperature.•Shape stabilisation is the most prevailing incorporation because friendly and cheap ...operation.•Physical properties of PCM composites should get attention as equivalent to thermal properties.•The performance of PCM relies heavily on the ambient condition of construction.
Building construction deserves many attentions due to its huge energy consumption, while Phase Change Materials (PCMs) provide positive solutions for improving energy efficiency and enhancing the thermal properties of construction materials. However, PCMs also present some negative impacts, such as weakening mechanical properties and increasing costs, chemical instability and so on. In this paper, the main characteristics of PCMs, design and incorporating methods, effects on energy consumption and construction reliability are comprehensively reviewed and discussed. Although many materials have the capacity of phase change, some organic PCMs are more suitable due to the higher latent heat and favourable phase change point in buildings, when eutectic PCMs present greater potential to become the optimal one but much effort is required for investigations. Current design methods and application in construction materials can meet the essential requirements, but the effectiveness is inadequate, including low efficiency of phase changing, leading to low energy storage. Subsequently, some promising research direction and critical areas for optimization are also proposed accordingly in this paper. Future development of PCMs, including novel PCM and efficient incorporation, real applications and functions in buildings are proposed. Additionally, multifunctional construction materials combining PCM deserve much attention and possess promising prospect for energy saving in sustainable and energy efficient building construction.
•MEPCMs with thermal expansion void were successfully prepared.•MEPCMs with thermal expansion void exhibit good thermal cycling durability.•Metal-based MEPCMs exhibit excellent heat transfer ...performance.
Microencapsulated phase change materials (MEPCMs) have great application prospects in medium/high temperature thermal energy storage. However, it might rupture due to the thermal expansion of PCMs during the phase change process, which greatly reduces its service life and seriously restricts its development. Herein, an innovative technique to encapsulate PCMs was presented. A thermal expansion void was successfully constructed inside the MEPCMs by “double-layer coating, sacrificial inner layer” method to accommodate volume expansion of PCMs. Scanning electron microscope (SEM), differential scanning calorimeter (DSC), Powder X‐ray diffraction (XRD) and other characterizations revealed the microstructure and thermal performance of MEPCMs. The results showed that MEPCMs with thermal expansion void exhibit better thermal performance and longer thermal cycle life than that of MEPCMs without thermal expansion void. Based on this method, the rupture problem of MEPCMs caused by thermal expansion of PCMs during phase change process can be solved thoroughly. Furthermore, “double-layer coating, sacrificial inner layer” method is also suitable for microencapsulation of other metals and it provides a new perspective for medium or high temperature metal microencapsulation.
•Melting heat transfer of nano-enhanced n-octadecane-mesoporous silica addressed.•The presence of nanoparticles induces non-Newtonian phase change behavior.•A deformed mesh technique is employed to ...track the phase change interface.•The phase change interface is at an exact fusion temperature.•The presence of the nano-particles decreases the melting intensity.
The heat transfer removal from heated elements in different engineering devices is the main challenge for each engineer in various fields. This problem can be solved using an effective heat-transfer agent or by increasing the heat transfer surface. The present work is devoted to an opportunity to use the phase change material with nanoparticles for an intensification of heat removal within a gap between two coaxial vertical isothermal cylinders. The analysis was performed numerically using the Galerkin finite element approach in the case of the non-Newtonian nature of the nano-enhanced PCM. The power-law was used for the description of the non-Newtonian behavior of the considered material. For the solution to the Stefan problem, a deformed mesh method, based on the Arbitrary Lagrangian–Eulerian (ALE), was used. The developed computational code was validated using the numerical and experimental data of other authors. The effects of the nanoparticles volume fraction, aspect ratio and Fourier number on the melting process were investigated. It has been revealed that the inclusion of nanoparticles within the phase change material leads to both less intensive melting of the material and a reduction of the average Nusselt number.
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