Preparation, thermal properties and thermal reliability of eutectic mixtures of fatty acids/expanded vermiculite as novel form-stable composites for energy storage

Recent advancements in battery thermal management system (BTMS): A review of performance enhancement techniques with an emphasis on nano-enhanced phase change materials

Because of their numerous benefits such as high charge cycle count, low self-discharge rate, low maintenance requirements, and tiny footprint, Li-batteries have been extensively employed in recent times. However, mostly Li-batteries have a limited lifespan of up to three years after production, may catch fire if the separator is damaged, and cannot be recharged when they are fully depleted. Due to the significant heat generation that li-batteries produce while they are operating, the temperature difference inside the battery module rises. This reduces the operating safety of battery and limits its life. Therefore, maintaining safe battery temperatures requires efficient thermal management using both active and passive. Thermal optimization may be achieved battery thermal management system (BTMS) that employs phase change materials (PCMs). However, PCM's shortcomings in secondary heat dissipation and restricted thermal conductivity still require development in the design, structure, and materials used in BTMS. We summarize new methods to control temperature of batteries using Nano-Enhanced Phase Change Materials (NEPCMs), air cooling, metallic fin intensification, and enhanced composite materials using nanoparticles which work well to boost their performance. To the scientific community, the idea of nano-enhancing PCMs is new and very appealing. Hybrid and ternary battery modules are already receiving attention for the li-battery life span enhancement ultimately facilitating their broader adoption across various applications, from portable electronics to electric vehicles and beyond.

Expanded Vermiculite/D-Mannitol as Shape-Stable Phase Change Material for Medium Temperature Heat Storage

Aiming to promote the application of D-mannitol in the field of phase change thermal storage, obstacles, including low thermal storage efficiency and high supercooling, should be properly disposed of. The adoption of adaptable and low-cost supporting materials to make shape-stable phase change materials (ss-PCMs) affordable is a primary solution to solve the above shortcomings. In this study, high-performance ss-PCM for effective medium-temperature heat storage was prepared using expanded vermiculite as the support for D-mannitol preservation. Among the three candidates that treated the raw vermiculite by dilute acid, calcination, and microwave heating, the calcinated expanded vermiculite (CV) was characterized as the most suitable one. After impregnating D-mannitol into the CV carrier by vacuum, a melting enthalpy of 205.1 J/g and a crystallization enthalpy of 174.1 J/g were achieved by the as-received CV/D-mannitol ss-PCM. Additionally, the supercooling of the ss-PCM was reduced to 45.6 °C. The novel CV/D-mannitol ss-PCM also exhibited excellent reusability and stability. All the findings indicate that the abundant and inexpensive CV exhibited great potential as the supporting material for D-mannitol-based ss-PCMs, which allow effective waste heat recovery and temperature regulation.

An Overview of the Nano-Enhanced Phase Change Materials for Energy Harvesting and Conversion

This review offers a critical survey of the published studies concerning nano-enhanced phase change materials to be applied in energy harvesting and conversion. Also, the main thermophysical characteristics of nano-enhanced phase change materials are discussed in detail. In addition, we carried out an analysis of the thermophysical properties of these types of materials as well as of some specific characteristics like the phase change duration and the phase change temperature. Moreover, the fundamental improving techniques for the phase change materials for solar thermal applications are described in detail, including the use of nano-enhanced phase change materials, foam skeleton-reinforced phase change materials, phase change materials with extended surfaces, and the inclusion of high-thermal-conductivity nanoparticles in nano-enhanced phase change materials, among others. Those improvement techniques can increase the thermal conductivity of the systems by up to 100%. Furthermore, it is also reported that the exploration of phase change materials enhances the overall efficiency of solar thermal energy storage systems and photovoltaic-nano-enhanced phase change materials systems. Finally, the main limitations and guidelines for future research in the field of nano-enhanced phase change materials are summarized.

Expanded vermiculite supported capric-palmitic acid composites for thermal energy storage

In this study, the potential application of expanded vermiculite (EVM) as the supporting material and capric-palmitic acid (CA-PA) binary eutectic as the adsorbent mixture to fabricate a form-stable composite CA-PA/EVM by a vacuum impregnation method was investigated. The prepared form-stable composite CA-PA/EVM was then characterized by scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TG), differential scanning calorimetry (DSC) and a thermal cycling test. The maximum loading capacity and melting enthalpy of CA-PA/EVM could reach 51.84% and 67.5 J g^-1. Meanwhile, the thermal physical and mechanical properties of the CA-PA/EVM-based thermal energy storage mortars were examined to determine if the composite material based on the newly invented CA-PA/EVM material can be employed for energy conservation and efficiency in the building field. In addition, the law of full-field deformation evolution of CA-PA/EVM-based thermal energy storage mortar under uniaxial compression failure was studied based on digital image correlation (DIC) technology, which provides certain guiding significance for the application of CA-PA/EVM-based thermal energy storage mortars in practical engineering.

Experimental Research on the Preparation of K2CO3/Expanded Vermiculite Composite Energy Storage Material

Thermochemical adsorption energy storage is a potential energy utilization technology. Among these technologies, the composite energy storage material prepared by K₂CO₃ and expanded vermiculite (EVM) shows excellent performance. In this paper, the influence of the preparation process using the impregnation method and vacuum impregnation method on K₂CO₃/EVM composite material is studied. The preparation plan is further optimized with the solution concentration and the expanded vermiculite particle size as variables. In the experiment, mercury intrusion porosimetry (MIP) is used to measure the porosity and other parameters. Additionally, with the help of scanning electron microscopy (SEM), the morphological characteristics of the materials are obtained from a microscopic point of view. The effects of different preparation parameters are evaluated by comparing the experimental results. The results show that the K₂CO₃ specific gravity of the composite material increases with the increase of the vacuum degree, up to 70.440 wt.% (the vacuum degree is 6.7 kPa). Expanded vermiculite with a large particle size (3~6 mm) can carry more K₂CO₃, and content per cubic centimeter of K₂CO₃ can be as high as 0.466 g.

Enhancing the Heat Storage Performance of a Na2HPO4·12H2O System via Introducing Multiwalled Carbon Nanotubes

The hydrated salt disodium hydrogen phosphate dodecahydrate (DHPD, Na₂HPO₄·12H₂O) has a suitable phase transition temperature and high latent heat of phase transition. Still there are problems such as supercooling, phase separation, and low thermal conductivity. In this paper, DHPD, sodium carboxymethyl cellulose (CMC), aluminum oxide (Al₂O₃), and poly(vinylpyrrolidone) (PVP) are used to configure DHPD-CAP to suppress supercooling and phase separation successfully. Multiwalled carbon nanotubes (MWCNTs) are used to stabilize DHPD-CAP phase-change materials and improve the thermal conductivity of pure DHPD. Further studies show only a physical interaction between MWCNTs and DHPD, and no new phases are generated. The addition of MWCNTs can also promote the nucleation of the DHPD-CAP composite, and the corresponding latent heat of phase change shows a trend of increasing and then decreasing with the increase of MWCNT content. Compared with DHPD after one cycle, the latent heat of DHPD-CAP/MWCNT₄ increases by 36.19%. With the addition of MWCNTs, the thermal stability of the composites is improved compared to pure DHPD. The DHPD-CAP/MWCNT₄ composite has good stability after many cycles.

Review on the Integration of Phase Change Materials in Building Envelopes for Passive Latent Heat Storage

Latent heat thermal energy storage systems incorporate phase change materials (PCMs) as storage materials. The high energy density of PCMs, their ability to store at nearly constant temperature, and the diversity of available materials make latent heat storage systems particularly competitive technologies for reducing energy consumption in buildings. This work reviews recent experimental and numerical studies on the integration of PCMs in building envelopes for passive energy storage. The results of the different studies show that the use of PCMs can reduce the peak temperature and smooth the thermal load. The integration of PCMs can be done on the entire building envelope (walls, roofs, windows). Despite many advances, some aspects remain to be studied, notably the long-term stability of buildings incorporating PCMs, the issues of moisture and mass transfer, and the consideration of the actual use of the building. Based on this review, we have identified possible contributions to improve the efficiency of passive systems incorporating PCMs. Thus, fatty acids and their eutectic mixtures, combined with natural insulators, such as vegetable fibers, were chosen to make shape-stabilized PCMs composites. These composites can be integrated in buildings as a passive thermal energy storage material.

Enhancement of Thermo-Physical Properties of Expanded Vermiculite-Based Organic Composite Phase Change Materials for Improving the Thermal Energy Storage Efficiency

In this work, expanded vermiculite (EVM) was modified by acid leaching with different concentrations (0.01, 0.05, and 0.1 mol/L) of HCl solution to obtain three kinds of acid-modified EVM (AEVM-1, AEVM-2, and AEVM-3, respectively). In the composite, polyethylene glycol (PEG) was served as a phase change material (PCM), while EVM and AEVM were served as supporting matrixes. Then, graphite was served as an additive to enhance thermal conductivity, and a series of shape-stabilized composite PCMs (PEG/EVM, PEG/AEVM-1, PEG/AEVM-2, PEG/AEVM-3, and PEG-C/AEVM-3 ss-CPCMs) were prepared by physical impregnation. The latent heats of PEG/AEVM-3 and PEG-C/AEVM-3 in the melting process were 154.8 and 144.7 J/g, respectively, which increased by 22.7 and 14.7%, respectively, compared with that of PEG/EVM, indicating that acid modification effectively enhanced the heat storage capacity. The thermal conductivity of PEG-C/AEVM-3 was 0.43 W/mK, which was 65.4 and 48.3% higher than that of PEG and PEG/EVM, respectively. The results of Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and the thermal cycle test indicated that PEG-C/AEVM-3 reflected favorable chemical stability, thermal stability, and thermal reliability. Therefore, the prepared PEG-C/AEVM-3 with high latent heat and acceptable thermal conductivity was a promising composite PCM in the field of building energy storage.

Bringing naturally-occurring saturated fatty acids into biomedical research

This review introduces naturally-occurring saturated fatty acids (NSFAs) and their biomedical applications, including controlled drug release, targeted drug delivery, cancer therapy, antibacterial treatment, and tissue engineering.

Study of Phase-Transition Characteristics of New Composite Phase Change Materials of Capric Acid-Palmitic Acid/Expanded Graphite

A new composite phase change material of capric acid-palmitic acid/expanded graphite (CA-PA/EG) with the optimum mass ratio of EG equated to 8:1 was prepared by the physical adsorption method. It was observed that the eutectic point of CA-PA binary system was reached at 22.1 °C, and CA-PA was uniformly distributed into the pores of EG by physical interaction. The melting and freezing temperatures of CA-PA/EG obtained by differential scanning calorimeter (DSC) were 23.05 and 20.82 °C, respectively, while the corresponding latent heats were 139.7 and 131.8 J/g, respectively. It had good thermal and chemical stability, and there was almost no leakage of liquid binary phase change materials after 1000 melting-freezing cycles. According to the experimental results of the thermogravimetry (TG) analyzer as well as heat storage and release, CA-PA/EG has excellent thermal reliability and heat resistance and the high thermal conductivity of EG promotes the thermal energy storage and release rate of CA-PA. Thus, CA-PA/EG is suitable as a phase change energy storage material for building energy conservation.

Bio-Based Phase Change Materials Incorporated in Lignocellulose Matrix for Energy Storage in Buildings—A Review

Due to growing consciousness regarding the environmental impact of fossil-based and non-sustainable materials in construction and building applications, there have been an increasing interest in bio-based and degradable materials in this industry. Due to their excellent chemical and thermo-physical properties for thermal energy storage, bio-based phase change materials (BPCMs) have started to attract attention worldwide for low to medium temperature applications. The ready availability, renewability, and low carbon footprint of BPCMs make them suitable for a large spectrum of applications. Up to now, most of the BPCMs have been incorporated into inorganic matrices with only a few attempts to set the BPCMs into bio-matrices. The current paper is the first comprehensive review on BPCMs incorporation in wood and wood-based materials, as renewable and sustainable materials in buildings, to enhance the thermal mass in the environmentally-friendly buildings. In the paper, the aspects of choosing BPCMs, bio-based matrices, phase change mechanisms and their combination, interpretation of life cycle analyses, and the eventual challenges of using these materials are presented and discussed.

Fabrication and Thermal Properties of Capric Acid/Calcinated Iron Tailings/Carbon Nanotubes Composite as Form-Stable Phase Change Materials for Thermal Energy Storage

In this study, a novel form-stable phase change material (FSPCM) consisting of calcination iron tailings (CIT), capric acid (CA), and carbon nanotubes (CNT) was prepared using a simple direct melt impregnation method, and a series of tests have been carried out to investigate its properties. The leakage tests showed that CA can be retained in CIT with a mass fraction of about 20 wt.% without liquid leakage during the phase change process. Moreover, the morphology, chemical structure, and thermal properties of the fabricated composite samples were investigated. Scanning electron microscope (SEM) micrographs confirmed that CIT had a certain porous structure to confine CA in composites. According to the Fourier transformation infrared spectroscope (FTIR) results, the CA/CIT/CNT FSPCM had good chemical compatibility. The melting temperature and latent heat of CA/CIT/CNT by differential scanning calorimeter (DSC) were determined as 29.70 °C and 22.69 J/g, respectively, in which the mass fraction of CIT and CNT was about 80 wt.% and 5 wt.%, respectively. The thermal gravity analysis (TGA) revealed that the CA/CIT/CNT FSPCM showed excellent thermal stability above its working temperature. Furthermore, the melting and freezing time of CA/CIT/CNT FSPCM doped with 5 wt.% CNT reduced by 42.86% and 54.55% than those of pure CA, and it showed better heat transfer efficiency. Therefore, based on the above analyses, the prepared CA/CIT/CNT FSPCM is not only a promising candidate material for the application of thermal energy storage in buildings, but it also provides a new approach for recycling utilization of iron tailings.

Capric Acid Hybridizing Fly Ash and Carbon Nanotubes as a Novel Shape-Stabilized Phase Change Material for Thermal Energy Storage

Capric acid (CA) is one of the most promising phase change materials to be used in reducing the energy consumption of buildings due to its suitable phase change temperature and high latent heat. In this paper, a novel shape-stabilized phase change material (SSPCM) is fabricated by "hazardous waste" fly ash (FA) via simple impregnation method along with CA and carbon nanotubes (CNTs). In this composite, raw FA without any modification serves as the carrier matrix to improve structural strength and overcome the drawback of the leakage of liquid CA. Simultaneously, CNTs act as an additive to increase the thermal conductivity of composites. The results of leakage tests indicate that CA was successfully confined as 20 wt % in the composite. Then, various characterization techniques were adopted to investigate the structure and properties of the prepared SSPCM of CA/FA/CNT. Scanning electron microscopy and Fourier transform infrared spectroscopy results showed that CA was well adsorbed into the microstructure of FA, and there was no chemical interaction between the components of the composites. Thermogravimetric analysis results demonstrated that the SSPCM presented good thermal stability. Differential scanning calorimetry results indicated that the melting temperature and freezing temperature of CA/FA/CNT were 31.08 and 27.88 °C, respectively, and the latent heats of CA/FA/CNT during the melting and freezing processes were 20.54 and 20.19 J g^-1, respectively. Moreover, compared to the CA and CA/FA, the heat transfer efficiency of CA/FA/CNT was significantly improved by doping 1, 3, 5, and 7 wt % of CNT. All of the results suggest that CA/FA/CNT possessed comfortable melting and freezing temperatures, excellent thermal stability, high latent heat value, and favorable thermal conductivity, and therefore, it is a suitable thermal storage material for building applications. Simultaneously, CA/FA/CNT can improve the comprehensive utilization level of FA.

Mullite Stabilized Palmitic Acid as Phase Change Materials for Thermal Energy Storage

In this paper, mullite was adopted in order to absorb Palmitic Acid (PA) via a direct impregnation method. The prepared PA/mullite form-stable phase change materials (FSPCM) were systematically characterized by the Leakage Test (LT), Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Differential Scanning Calorimeter (DSC), Thermogravimetry (TG) and Cooling Curve Method (CCM). The results indicated that, among these composites with different mass fractions of PA, the sample with the 32 wt % Palmitic Acid has the best properties without any leakage. The enthalpy of 32%PA/68%mullite FSPCM is 50.8 J/g for melting process, and 58.3 J/g for solidifying process. The phase change point of 32%PA/68%mullite FSPCM is 64.1 °C for melting and 58.7 °C for solidifying. The heat storage efficiency of the PA/mullite FSPCM was enhanced considerably by adding mullite. The leakage and thermal properties of PA/mullite FSPCM were discussed and the performance of the FSPCM has been apparently improved.

Carbon nanotube/paraffin/montmorillonite composite phase change material for thermal energy storage

A composite phase change material (PCM) comprised of organic montmorillonite (OMMT)/paraffin/grafted multi-walled nanotube (MWNT) is synthesized via ultrasonic dispersion and liquid intercalation. The microstructure of the composite PCM has been characterized to determine the phase distribution, and thermal properties (latent heat and thermal conductivity) have been measured by differential scanning calorimetry (DSC) and a thermal constant analyzer. The results show that paraffin molecules are intercalated in the montmorillonite layers and the grafted MWNTs are dispersed in the montmorillonite layers. The latent heat is 47.1 J/g, and the thermal conductivity of the OMMT/paraffin/grafted MWNT composites is 34% higher than that of the OMMT/paraffin composites and 65% higher than that of paraffin.

A Study on a Novel Phase Change Material Panel Based on Tetradecanol/Lauric Acid/Expanded Perlite/Aluminium Powder for Building Heat Storage

Phase change material (PCM) used in buildings can reduce the building energy consumption and indoor temperature fluctuation. A composite PCM has been fabricated by the binary eutectic mixture of tetradecanol (TD) and lauric acid (LA) absorbed into the expanded perlite (EP) using vacuum impregnation method, and its thermal conductivity was promoted by aluminium powder (AP) additive. Besides, the styrene-acrylic emulsion has been mixed with the composite PCM particles to form the protective film, so as to solve the problem of leakage. Thus, a novel PCM panel (PCMP) has been prepared using compression moulding forming method. The thermal property, microstructure characteristic, mechanical property, thermal conductivity, thermal reliability and leakage of the composite PCM have been investigated and analysed. Meanwhile, the thermal performance of the prepared PCMP was tested through PCMPs installed on the inside wall of a cell under outdoor climatic conditions. The composite PCM has a melting temperature of 24.9 °C, a freezing temperature of 25.2 °C, a melting latent heat of 78.2 J/g and a freezing latent heat of 81.3 J/g. The thermal conductivity test exposed that the thermal conductivity has been enhanced with the addition of AP and the latent heat has been decreased, but it still remains in a high level. The leakage test result has proven that liquid PCM leaking has been avoided by the surface film method. The thermal performance experiment has shown the significant function of PCMP about adjusting the indoor temperature and reducing the heats transferring between the wall inside and outside. In view of the thermal performance, mechanical property and thermal reliability results, it can be concluded that the prepared PCMP has a promising building application potential.

Building Energy Storage Panel Based on Paraffin/Expanded Perlite: Preparation and Thermal Performance Study

This study is focused on the preparation and performance of a building energy storage panel (BESP). The BESP was fabricated through a mold pressing method based on phase change material particle (PCMP), which was prepared in two steps: vacuum absorption and surface film coating. Firstly, phase change material (PCM) was incorporated into expanded perlite (EP) through a vacuum absorption method to obtain composite PCM; secondly, the composite PCM was immersed into the mixture of colloidal silica and organic acrylate, and then it was taken out and dried naturally. A series of experiments, including differential scanning calorimeter (DSC), scanning electron microscope (SEM), best matching test, and durability test, have been conducted to characterize and analyze the thermophysical property and reliability of PCMP. Additionally, the thermal performance of BESP was studied through a dynamic thermal property test. The results have showed that: (1) the surface film coating procedure can effectively solve the leakage problem of composite phase change material prepared by vacuum impregnation; (2) the optimum adsorption ratio for paraffin and EP was 52.5:47.5 in mass fraction, and the PCMP has good thermal properties, stability, and durability; and (3) in the process of dynamic thermal performance test, BESP have low temperature variation, significant temperature lagging, and large heat storage ability, which indicated the potential of BESP in the application of building energy efficiency.

Do carboximide-carboxylic acid combinations form co-crystals? The role of hydroxyl substitution on the formation of co-crystals and eutectics

Carboxylic acids, amides and imides are key organic systems which provide understanding of molecular recognition and binding phenomena important in biological and pharmaceutical settings. In this context, studies of their mutual interactions and compatibility through co-crystallization may pave the way for greater understanding and new applications of their combinations. Extensive co-crystallization studies are available for carboxylic acid/amide combinations, but only a few examples of carboxylic acid/imide co-crystals are currently observed in the literature. The non-formation of co-crystals for carboxylic acid/imide combinations has previously been rationalized, based on steric and computed stability factors. In the light of the growing awareness of eutectic mixtures as an alternative outcome in co-crystallization experiments, the nature of various benzoic acid/cyclic imide combinations is established in this paper. Since an additional functional group can provide sites for new intermolecular inter-actions and, potentially, promote supramolecular growth into a co-crystal, benzoic acids decorated with one or more hydroxyl groups have been systematically screened for co-crystallization with one unsaturated and two saturated cyclic imides. The facile formation of an abundant number of hydroxybenzoic acid/cyclic carboximide co-crystals is reported, including polymorphic and variable stoichiometry co-crystals. In the cases where co-crystals did not form, the combinations are shown invariably to result in eutectics. The presence or absence and geometric disposition of hydroxyl functionality on benzoic acid is thus found to drive the formation of co-crystals or eutectics for the studied carboxylic acid/imide combinations.

Development of Composite PCMs by Incorporation of Paraffin into Various Building Materials

In this research, we focused on the development of composite phase-change materials (CPCMs) by incorporation of a paraffin through vacuum impregnation in widely used building materials (Kaolin and ground granulated blast-furnace slag (GGBS)). The composite PCMs were characterized using environmental scanning electron microscopy (ESEM), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. Moreover, thermal performance of cement paste composite PCM panels was evaluated using a self-designed heating system. Test results showed that the maximum percentage of paraffin retained by Kaolin and GGBS was found to be 18% and 9%, respectively. FT-IR results show that CPCMs are chemically compatible. The phase-change temperatures of CPCMs were in the human comfort zone, and they possessed considerable latent-heat storage capacity. TGA results showed that CPCMs are thermally stable, and they did not show any sign of degradation below 150 °C. From thermal cycling tests, it was revealed that the CPCMs are thermally reliable. Thermal performance tests showed that in comparison to the control room model, the room models prepared with CPCMs reduced both the temperature fluctuations and maximum indoor center temperature. Therefore, the prepared CPCMs have some potential in reducing peak loads in buildings when applied to building facade.

Eutectics as improved pharmaceutical materials: design, properties and characterization

Eutectics are a long known class of multi-component solids with important and useful applications in daily life. In comparison to other multi-component crystalline solids, such as salts, solid solutions, molecular complexes and cocrystals, eutectics are less studied in terms of molecular structure organization and bonding interactions. Classically, a eutectic is defined based on its low melting point compared to the individual components. In this article, we attempt to define eutectics not just based on thermal methods but from a structural organization view point, and discuss their microstructures and properties as organic materials vis-a-vis solid solutions and cocrystals. The X-ray crystal structure of a cocrystal is different from that of the individual components whereas the unit cell of a solid solution is similar to that of one of the components. Eutectics are closer to the latter species in that their crystalline arrangement is similar to the parent components but they are different with respect to the structural integrity. A solid solution possesses structural homogeneity throughout the structure (single phase) but a eutectic is a heterogeneous ensemble of individual components whose crystal structures are like discontinuous solid solutions (phase separated). Thus, a eutectic may be better defined as a conglomerate of solid solutions. A structural analysis of cocrystals, solid solutions and eutectics has led to an understanding that materials with strong adhesive (hetero) interactions between the unlike components will lead to cocrystals whereas those having stronger cohesive (homo/self) interactions will more often give rise to solid solutions (for similar structures of components) and eutectics (for different structures of components). We demonstrate that the same crystal engineering principles which have been profitably utilized for cocrystal design in the past decade can now be applied to make eutectics as novel composite materials, illustrated by stable eutectics of the hygroscopic salt of the anti-tuberculosis drug ethambutol as a case study. A current gap in the characterization of eutectic microstructure may be fulfilled through pair distribution function (PDF) analysis of X-ray diffraction data, which could be a rapid signature technique to differentiate eutectics from their components.

Enhanced performance and interfacial investigation of mineral-based composite phase change materials for thermal energy storage

A novel mineral-based composite phase change materials (PCMs) was prepared via vacuum impregnation method assisted with microwave-acid treatment of the graphite (G) and bentonite (B) mixture. Graphite and microwave-acid treated bentonite mixture (GBm) had more loading capacity and higher crystallinity of stearic acid (SA) in the SA/GBm composite. The SA/GBm composite showed an enhanced thermal storage capacity, latent heats for melting and freezing (84.64 and 84.14 J/g) was higher than those of SA/B sample (48.43 and 47.13 J/g, respectively). Addition of graphite was beneficial to the enhancement in thermal conductivity of the SA/GBm composite, which could reach 0.77 W/m K, 31% higher than SA/B and 196% than pure SA. Furthermore, atomic-level interfaces between SA and support surfaces were depicted, and the mechanism of enhanced thermal storage properties was in detail investigated.