Inorganic Phase Change Materials Research Articles

A VIKOR based selection of phase change material for thermal energy storage in solar dryer system

Phase Change Material (PCM) has vast applications in Thermal Energy Storage (TES). An efficient thermal energy storage system design depends on properly selecting PCM. This study found a detailed and organized process for evaluating PCMs for the design of latent heat based thermal energy storage that includes pre-screening, ranking, and objectively evaluating performance utilizing Multi-Criteria Decision-Making (MCDM) methods. Among some PCMs suitable for low-temperature thermal energy storage applications, organic PCMs are a desirable option over inorganic PCMs. The following properties, such as melting point temperature, latent heat, thermal conductivity, specific heat capacity, density, and cost, are considered in PCM selection. This work aims to select an eco-friendly, economical, and thermal-efficient PCM for low temperature (40 °C – 70 °C) solar dryer application from the thirteen identified PCM’s. VIKOR technique is used to select the suitable PCM from the identified PCMs like Natural Soya Wax, Bee Wax (C15 H31 COO C30 H61), Paraffin Wax, Palm Wax, Stearic Acid (CH3(CH2)16 CO2), Lauric Acid (C12 H24 O2), Palmitic Acid (C16 H32 O2), Medicine Paraffin Wax, RT55, RT60, P116, Shellac Wax (C30 H50 O11), and CR + 55A. This technique ranks the identified PCM using the appropriate properties. Paraffin wax ranks at the top, satisfying all the required properties. The results showed that this technique is a feasible tool for choosing the appropriate PCM.

OPTIMIZATION AND THERMAL PERFORMANCE INVESTIGATION OF CYLINDRICAL RODS FILLED WITH PCM MATERIAL USING CFD SIMULATION METHOD

A phase-change material (PCM) thermal energy storage (TES) has been studied as part of a project to develop a solar-based room-heating system for extreme cold areas using ANSYS Fluent. The purpose of using a PCM thermal storage is to overcome the intermittency of solar and provide room heating during nighttime as a sustainable and clean solution. A computational fluid dynamic (CFD) model is developed for a cubical TES unit having an array of cylindrical rods of stainless steel filled with inorganic PCM as thermal storage media. Heat-transfer fluid (HTF) selected for this study is water. In the present study, the diameter of cylindrical rods is optimized by comparing the melting characteristics of PCM with three different diameters, and thermal performance of the selected option is investigated and discussed. ANSYS Fluent software is used for numerical modeling of a commercially available inorganic PCM material Save-HS48 (Pluss Advanced Technologies, India) and the results were validated using experimental data provided by the PCM manufacturer. 3D transient option with solidification and melting in Ansys Fluent software is selected for the investigation. A four-hour charging time is assumed for the numerical modeling and discharging for a particular case was studied with suitable assumptions for full-cycle analysis. Thermo-physical properties of Save-HS48 PCM are found to be suitable for solar room-heating application and effectiveness of all the cases simulated in the present study provides suitable results for further experimental study of a PCM-TES unit.

Self-repairing thermal energy storage gels demonstrating superior thermophysical properties and wearability towards personal thermal management in static and dynamic modes

It is still a big challenge to develop state-of-art thermal energy storage materials based on phase-change materials (PCMs) with superior thermophysical properties and wearability for efficient advanced personal thermal management (PTM). A novel strategy for synthesizing thermal energy storage gel with sandwich structure by confining the inorganic PCM gel in the organic PCM gel was proposed to maximize the advantages of inorganic PCMs, organic PCMs and gel materials. Octadecane and sodium sulfate decahydrate were selected as the organic PCM and inorganic PCM, respectively to satisfy the requirements of the working temperature of PTM. The thermal energy storage gels with sandwich structure demonstrate superior thermophysical properties, such as the absence of supercooling (0 °C), high latent heat (158.65 J g−1), high form-stability (no leakage), high cyclic stability (200 cycles) and high economic benefits (4.85 × 10−3 ¥ J−1). Besides, they also have excellent wearability, such as high flexibility, self-healing feature and high biocompatibility. Due to the synergistic enhancement effect and various merits, the novel thermal energy storage gels are successfully utilized in the wearable PTM for human body thermal comfort. The inorganic–organic combination methodology is promising for the highly efficient applications of PCMs in the next-generation PTM.

Electrically-triggered nucleation of supercooled sodium acetate trihydrate phase change composites

Phase change energy storage technology has broad applications in many engineering fields, such as building energy conservation, aerospace, and thermal management of electric equipment. However, the inorganic phase change materials suffer a lot from supercooling, phase separation, and low thermal conductivity. Therefore, this paper aims at developing a novel electrically-triggered phase change composite by making use of its supercooling characteristics, achieving a controllable release of latent heat as it is wanted. Polished by radial and axial grinding respectively, both surface-triggered electrodes (STE) with a uniform rough structure and point-triggered electrodes (PTE) with the gradient rough structure were prepared to investigate the effect of surface structure on the electrical crystallization. The 100-cycle test results indicated the newly-prepared electrode achieved a stable electrically-triggering ability. The oxidation rate of electrodes was significantly affected by interface characteristics of the gas–liquid-solid interfaces. What’s more, the effect of voltage and supercooling degree on the crystallization behaviours, like induction time, morphology, and growth of the dendrite, and heat transfer process, were comprehensively investigated. With the increase of the supercooling degree, the dendrite shape gradually changed from acicular crystal to flocculent crystal, and the induction time decreased rapidly. To improve the thermal conductivity, a novel phase change composite using sodium acetate trihydrate/carboxymethyl cellulose/expanded graphite (SAT/CMC/EG) was developed. Considering both thermal conductivity and electrical nucleation, the optimized mass ratio of SAT: CMC: EG was 100:1:8. These research findings would provide valuable guidance in the intelligently-controllable energy storage technology.

Photothermally induced, reversible phase transition in methylammonium lead triiodide

<h2>Summary</h2> Metal halide perovskites (MHPs) undergo structural phase transitions, from lower to higher symmetry, upon heating. Although phase transitions have been investigated by optical, thermal, and diffraction methods, most measurements are quasi-static and do not inform on the fundamental timescale of their phase transitions. Here, we investigate the timescale of the orthorhombic-to-tetragonal phase transition in methylammonium lead triiodide using nanosecond transient absorption spectroscopy. Using mid-infrared pulses to impulsively heat the material held right below the phase-transition temperature, we observe a clean signature of transient, reversible orthorhombic-to-tetragonal transition on the tens-of-nanoseconds timescale. A high degree of transient phase transition is observed accounting for one-third of the steady-state counterpart. Compared with inorganic phase-change materials, the orders-of-magnitude-slower phase transition in MAPbI₃ suggests a large energy barrier for activating the hydrogen-bond network and the accompanying cooperative octahedral rotations. Our approach paves the way for unraveling phase-transition dynamics in MHPs and other hybrid materials.

Lignin-g-polycaprolactone as a form-stable phase change material for thermal energy storage application

Lignocellulosic biomass is mostly found in municipal waste by-products, and a major component of this waste is made up of the macropolymer, lignin, which is usually hard to valorize and causes environmental pollution issues. Valorizing lignin through their hydroxy groups has been intensively researched for various purposes and therefore, is a promising green alternative sustainable material. Lignin can be used as a composite phase change material (PCM) as compared to conventional organic and inorganic PCMs. In this work, Lignin-g-polycaprolactone (PCL) was prepared by grafting of alkaline lignin with PCL via the ring-opening polymerization reaction using triazabicyclodecane (TBD) as an organic catalyst. A comparison study of the physically mixed lignin with PCL, and Lignin-g-PCL was conducted to investigate the differences in their thermophysical properties. The chemical structure of Lignin-g-PCL was verified by nuclear magnetic resonance (NMR), and the products were separated by molecular weight via gel permeation chromatography (GPC), revealing the PCL was successfully grafted onto the lignin via the ring-opening polymerization. Differential scanning calorimetry (DSC) results showed that the phase transition temperature of Lignin-g-PCL was approximately 51.3 °C, with a latent heat value of 61.16 J/g. Thermal cycling test up to 100 cycles also revealed its thermal stability and reliability in applications. Thermogravimetric analysis (TGA) confirmed its thermal degradation temperatures at 300–400 °C which was much higher than its melting temperature 51.3 °C. Lignin-g-PCL also showed superior form stability in contrast to both its pristine counterparts and physically mixed samples based on a form stability and leakage test. Lastly, Lignin-g-PCL demonstrated its potential application as a PCM via a thermal absorption test where its solid-solid phase change was most apparent during cooling and was able to exhibit thermoregulation of about 2 min at near body temperature of about 39 °C.

Performance Assessment of Direct Vapor Generation Solar Organic Rankine Cycle System Coupled with Heat Storage

Phase change materials employed as thermal energy storage can aid in maximizing the use of stored solar energy. The current research examined the impact of three kinds of phase change materials (PCMs) on the dynamic performance of a solar organic Rankine cycle (ORC) system based on a direct vapor production. A number of evacuated flat plate collectors, a condenser, an expander, and an organic fluid pump make up this system. The thermodynamic cycle model of the direct vapor generation (DVG) solar ORC system was combined with the finite difference model of a phase change material heat storage tank created in MATLAB. The effect of PCMs (Organic, Inorganic and Eutectic PCMs) on the collector, ORC, and system efficiency, net power output, PCM temperature, and heat stored was studied weekly, monthly, and annually. Among the selected PCMs, Mg(NO3)2.6H2O had the highest system efficiency at 9.34%; KNO3-NaNO2 had the highest net power output at 33.80 kW; and MgCl2.6H2O stored the maximum energy of 20.18 MJ annually. Under the given operational and boundary conditions, the spring and fall were preferable to the summer and winter months for storing heat from phase change materials.

Developing a novel thermo-regulating cotton fabric using inorganic eutectic phase change material

Developing a novel thermo-regulating cotton fabric using inorganic eutectic phase change material

Preparation and thermal properties of novel inorganic-organic eutectic composite material with high latent heat and thermal conductivity based on aluminum sulfate salt

Potassium aluminum sulfate dodecahydrate (Alum) and ammonium aluminum sulfate dodecahydrate (AAS) are two potential inorganic phase change materials with high transformation enthalpy. To make them more flexible to match temperature requirements of various fields, the melting temperature needs to be manipulated but less effect on latent heat. In this work, two novel eutectic mixtures of Alum-E and AAS-E were obtained by adding erythritol (E) with high latent heat into aluminum sulfate salts. The results denoted that the melting temperatures of the two eutectic mixtures were 72.46 °C and 73.20 °C when containing 35 wt% and 37 wt% erythritol, respectively. It was worth noting that they still possessed high latent heat of 243.4 J/g and 257.4 J/g. Considering the stability of NH4+ at high temperature, Alum-E was chosen to fabricate Alum-E/EG (expanded graphite) composite material with high thermal conductivity via melt-blending method. EG not only increased the thermal conductivity from 0.61 W/(m·K) to 10.95 W/(m·K) as an excellent enhanced heat transfer carrier, but also prevented leakage of Alum-E/EG composite material effectively as a porous adsorption carrier when contained 15 wt% EG. Moreover, the thermal stability tests indicated that Alum-E possessed favorable thermal stability after 250 heat-cooling cycles. Above all, the obtained composite energy storage material is a promising candidate for afterheat recovery and medium and low-temperature energy storage areas else.

Studies of eutectic hydrated salt/polymer hydrogel composite as form-stable phase change material for building thermal energy storage

The inorganic phase change material (PCM) is a promising energy storage material in the construction field because of their characteristics, such as high latent heat, low price and nonflammability. However, from the perspective of construction engineering applications, conventional inorganic phase change materials have some inherent performance defects, such as high phase change temperature, phase separation and leakage. To overcome these performance deficiencies, a novel eutectic hydrated salt/polymer hydrogel composite form-stable phase change material (HP-FSPCM) suitable for building thermal storage was developed, which used Na2SO4·10H2O–Na2CO3·10H2O eutectic salt (SCES) as PCM, sodium polyacrylate (PAAS) as thickener and packaging material, borax as nucleating agent and flake graphite as thermal conductivity enhancer. The phase change temperature and crystal structure characteristics of SCES were analyzed by means of step cooling curve method and X-ray diffraction technique (XRD). The microstructure and thermal properties of HP-FSPCM were tested and analyzed by scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and transient planar thermal conductivity instrument. The test results showed that the cross-linked network formed by PAAS can eliminate the phase separation and leakage of SCES, and the latent heat value, melting temperature and crystallization temperature of HP-FSPCM were 165.5 J/g, 22.4 °C and 13.8 °C, respectively. The thermal cycle reliability of HP-FSPCM was tested, the latent heat loss of HP-FSPCM was only 2.2% after 300 thermal cycles.

Thermal characteristics enhancement of Na2HPO4⋅12H2O/expanded graphite form-stable composite phase change material by the cationic surfactant modification

Phase change materials (PCMs) are widely used for their effectively thermal energy storage and conversion. Na2HPO4⋅12H2O (DHPD) is a promising inorganic PCM, as it possesses large heat enthalpy and suitable phase change temperature. Hexadecyl trimethyl ammonium chloride (CTAC) hydrophilic structure of composite PCM (CPCM) was formed, because of the poor sealing stability of expanded graphite (EG). Indeed, there is the solid intermolecular attraction between cations of CTAC and the water of DHPD, thereby improving the thermal characteristics. The heat enthalpy of EG/CTAC 0.1-DHPD (ECCD-0.1) CPCM was 299 J/g, and the thermal conductivity of ECCD-0.1 CPCM was 1.411 W/m⋅K. The ECCD-CPCMs showed a great cyclic stability which remained stable after 500 melting-solidification cycles.

Encapsulation of inorganic phase change thermal storage materials and its effect on thermophysical properties: A review

Latent heat energy storage has received lots of concern on account of its high energy storage density and almost constant operating temperature. Phase change materials (PCM) possess unavoidable defects, like flammability, low thermal conductivity, subcooling, phase separation, etc. Encapsulation techniques have been adopted to address these challenges. Many efforts have been devoted to this by researchers, but the bulk of the work is based on organic PCMs, and particularly, reviews on encapsulating organic PCMs are frequent. In contrast, there are only a handful of comprehensive reviews on encapsulating inorganic PCMs, which hardly deliver complete information. Therefore, this review aims to provide a comprehensive look at the recent research advances for encapsulated inorganic PCMs. Two broadly adopted encapsulation methods are observed: core-shell encapsulated PCM and shape-stabilized PCM. Three main preparation processes for core-shell encapsulation (in situ polymerization, solvent evaporation and sol-gel methods) are described. The two former techniques are mostly adopted for the microencapsulated hydrated salt PCMs and forming organic shells. The latter is suitable for inorganic shells. The porous skeleton materials widely adopted for shape-stabilized PCMs are presented. The advantages and disadvantages of porous carbon, porous clay minerals, porous silica, and other materials were evaluated. In addition, thermophysical properties, such as supercooling, phase separation, phase change temperature, tent heat, thermal conductivity and thermal cycling reliability are discussed. It was found that encapsulation technology can have positive effects on thermophysical properties. It is hoped that this work will assist readers in gaining a comprehensive insight into the development of inorganic PCMs.

Compact latent heat exchanger for the fast supply of hot water with serpentine tubes in shape-stabilized composite phase change material and auxiliary electric heating

• A composite phase change material-based heat exchanger is designed. • The composite phase change material owns a large enthalpy of 252 J/g. • An electric heating film is introduced to improve the heating efficiency. To realise a fast supply of hot water, this study proposes a compact latent heat exchanger. This heat exchanger consists of a certain number of heat-exchange plates. In each plate, serpentine tubes are wrapped with an inorganic composite phase change material (CPCM), Ba(OH) 2 ·8H 2 O/modified expanded graphite (MEG). An auxiliary electric heating film is attached to the face of the entire heat exchanger to improve the heating efficiency. The parameters of the plate, such as thickness, tube pass number, thermo-physical properties of the CPCM, flow rate, auxiliary heating power size, and position are numerically evaluated to achieve the best performance of this heat exchanger. The reliability of the simulation method is verified by comparing the simulated results with the experimental data in previous study. The simulation results indicate that a plate with a thickness of 15 mm, plate tube pass number of 10, and CPCM with a Ba(OH) 2 ·8H 2 O mass fraction of 85.8 wt% is the optimal choice. Based on the optimal conditions, 196.48 kg of hot water over 40 ℃ can be produced in 875 s and the average power reaches 23 kW. Furthermore, with the addition of a heating film (3600 W), the mass of heated water can be increased by nearly 50 kg.

Thermophysical Properties of Inorganic Phase-Change Materials Based on MnCl2·4H2O

Manganese (II) chloride tetrahydrate, classified as an inorganic phase-change material (PCM), can be used as a thermal energy storage material, saving and releasing thermal energy during its phase transitions. In this study, thermophysical properties, such as phase change temperatures, latent heat, and thermal conductivities, of four types of MnCl2·4H2O PCMs were investigated under single and dual phases (liquid-, solid-, and dual-phase PCMs) using differential scanning calorimetry (DSC) and a heat flow meter. PCMs with a liquid or dual phases exhibited superheating issues, and their melting temperatures were 7 to 10 °C higher than the reference melting temperatures. The PCMs had latent heats between 146 and 176 J/g in the temperature range of 23 to 45 °C under the endothermic process. Severe supercooling during the exothermic process was observed in all as-received specimens, but was mitigated in the homogenization-treated specimen, which sustained an increase in solidification temperature of about 15 °C compared with the as-received and treated PCMs. The diffusivities of PCMs were between 9.76 × 10−6 and 2.35 × 10−5 mm2/s. The diffusivities of the PCMs in the solid phase were higher than those in the liquid phase. During the initial holding time of the endothermic process, the PCM in the liquid phase could not be fully solidified due to an insufficient initial holding time and very low diffusivity, which caused superheating during the DSC measurement. Moreover, in the exothermic process, a fast cooling rate of 5 °C/min and low thermal diffusivity caused supercooling. In particular, the diffusivity of the liquid PCM was lower than those of the solid PCM and other PCMs, which caused extremely high supercooling during the DSC measurement. This paper provides the thermophysical properties of MnCl2·4H2O PCMs, which are not available in the literature. The homogeneity of PCMs in their initial states and their heating/cooling rates were identified, and constitute important factors for accurately measuring the thermophysical properties of PCMs.

An Overview on the Use of Phase Change Material (PCM) for PV Cooling

The thermal management processes for PhotoVoltaic (PV) cooling applications, increase PV systems’ overall efficiency and yield to a maximized power generation. Accordingly, this paper investigates recent PV thermal management methods, which involve the use of Phase Change Material (PCM) under the back of PV modules. Compared to other cooling methods (such as air and water based methods) PCM based techniques show less need for maintenance, are environment-friendly, and have a longer life cycle. Since PCM are diverse in nature, and many methods exist to guide their selection procedure, this paper begins by revealing different types of PCM, which are found to be as Organic, Inorganic, Eutectic and Commercial PCM, with the characteristics of each. After acknowledging different PCM natures, a selection process is established based on either the melting temperature, latent heat, or thermal conductivity of PCM. Results have shown that Commercial PCM are the best option followed by Organic PCM, due to their improved chemical aspects when compared with Inorganic and Eutectic PCM. Concerning PCM selection criteria, the easiest yet sufficient process is based on the melting temperature method, due to the simplified calculations when compared to other thermic quantities. At the end, future work recommendations are declared, related to PCM lifecycle assessment and cooling/heating cycles effects on PV entropy.

Investigational study on improving the yield from hybrid PV/T modified conventional solar still with enhanced evaporation and condensation technique - An experimental approach

ABSTRACT Renewable energy source is insisted in all areas of technology, especially the adaptation of solar power for various purposes. The present investigational study is carried out to improve the efficiency of PV/T solar still using enhanced evaporation and condensation technique. A DC-powered blower is fixed inside single slope solar still which increases the turbulence of evaporated vapor from the saline water inside the solar still while the condensation is improved using the cover cooling technique. The experiment is conducted on a constant water depth of 1 cm with three different blow rate periods (5 min, 10 min, and 15 min). The blower runs and stops for 30 seconds time period in all blow rates. To improve the efficiency of the photovoltaic system, an inorganic phase change material (PCM) (Glauber salt (Na2SO4.10H2O) is used underneath the PV panel for cooling the panel. To obtain a higher production rate of distilled water, a nickel-chromium (NiCr) heater is placed in the solar still which is powered by the integrated solar PV system. This proposed work helps to enhance the freshwater production process from saline water and also solar power production. From this investigation, it is observed that the proposed PV/T solar still gives an improved overall thermal and electrical efficiency of almost 12.5% and 11.5% respectively, and is superior as compared to the conventional solar still.

Effect of expanded graphite on the thermal conductivity of sodium sulfate decahydrate (Na2SO4·10H2O) phase change composites

Inorganic salt hydrate phase change materials (PCMs) are of interest for near-room temperature thermal energy storage (TES) systems, but their low thermal conductivity, ~ 0.5 W/m-K, limits their performance. In this work, we report the thermal conductivity and bulk density of composites containing sodium sulfate decahydrate (SSD) Na2SO4·10H2O with three types of graphite: expanded graphite (EG), milled EG (MG), and graphite nanoplatelets (GnP). The effect of these thermophysical properties on TES performance is presented. The composites were made using a readily scalable one-pot synthesis procedure with graphite received as-is. A 583% increase in thermal conductivity (4.1 W/m-K) was achieved with 25 wt% EG. However, as EG fraction increases, bulk density decreases and thermal conductivity plateaus. This ultimately resulted in lower thermal performance at higher EG fractions despite higher thermal conductivity. This highlights the tradeoff between PCM composite properties and performance, and why thermal conductivity is insufficient to describe PCM thermal performance. GnP is added to EG-SSD to increase bulk density and energy storage density, but these density improvements do not offset lower thermal conductivity and thus thermal performance declined. Similarly, MG-SSD composites had a higher bulk density and energy storage density, but lower thermal conductivity and thermal performance than EG-SSD composites at similar compositions. Atomistic molecular dynamics simulations were performed to understand the structure-property relationship of graphite-SSD interfaces. The simulations support the hypothesis that atomic level contact resistance between graphite and SSD increases thermal resistance at the interfaces resulting in effectively lower bulk thermal conductivity in MG-SSD compared to EG-SSD.

A study on frost and high-temperature resistance performance of supercooled phase change material-based flat panel solar collector

Easy freezing and overheating of the flat panel solar collector (FPSC) limits its large-scale application. In addition to the characteristics of high heat storage density and low price, inorganic supercooling phase change materials (PCMs) also have a large difference between their melting and freezing points, which fully meets the needs of FPSCs. In this paper, a new type of supercooled PCM as an FPSC was designed and studied, and a computational fluid dynamics (CFD) model was verified by experiments. Simulations were done to analyze the effects of different structures and PCM properties on the thermal efficiency and cooling rate of the collector. The results showed that the efficiency increase rate of the absorber plate was about 15% when the absorber plate was in direct contact with the PCM under neutralization. For the PCM with a melting point of 323.15 K and a supercooling degree of 30 K, the increase rate of the cooling time can reach more than 15% compared with that of a non-supercooled PCM. The structure of FPSC was optimized, and the thickness of PCM was studied in typical geographic areas. Except for Chengdu, the reliability index of the supercooled phase change material FPSC (SPCM-FPSC) in winter and summer was found to increase to more than 0.5 compared with 0.1 for ordinary FPSCs. It was found that the SPCM-FPSC significantly improved the freezing and high-temperature resistance of collectors in various regions. These results provide a strategy for the promotion and application of FPSCs in harsh outdoor environments.

Preparation and performance of magnetic phase change microcapsules with organic-inorganic double shell

Magnetic microcapsulated phase change materials can achieve rapid magnetic localization temperature regulation and magnetic separation recycling. However, the efficient encapsulation of both inorganic magnetic material and organic phase change material is a challenge due to their poor compatibility. In this work, an aqueous dispersion containing methylol melamine and sodium alginate loaded with magnetic Fe 3 O 4 nanoparticles (SA-Fe 3 O 4 ) was prepared and mixed with a paraffin emulsion. After methylol melamine was initiated to in-situ polymerize at the interface of the paraffin emulsion droplets, primary magnetic phase change microcapsules (P-MPCM) composed of a paraffin core and SA-Fe 3 O 4 /melamine formaldehyde resin composite shell were formed. Then, SiO 2 sol particles were adsorbed on the surface of P-MPCM to form the final MPCM with a polymer-SiO 2 double-shell (PS-MPCM). The magnetic polymer-SiO 2 double-shell endows the PS-MPCM with rapid magnetic responsiveness (can be quickly collected under magnetic fields), high phase change enthalpy (184.4 J·g-1) and excellent structural stability. The phase change enthalpy and saturation magnetization of PS-MPCM have changed little after 200 thermal cycles. At the same time, the excellent photothermal conversion efficiency (93.9%) of PS-MPCM benefits for solar energy conversion utilization in actual application. This work provides a new way to obtain MPCM with high thermal conductivity (0.64 W·m-1·K-1), rapid magnetic response and excellent reusability, which can be potentially applied for directional temperature regulation. Magnetic polymer-SiO 2 double-shell phase change microcapsule (PS-MPCM) was prepared. PS-MPCM exhibits high encapsulation ratio of paraffin and Fe 3 O 4 nanoparticles (NPs). Sodium alginate was introduced to achieve efficient and stable loading of Fe 3 O 4 NPs. PS-MPCM exhibits excellent thermal conductivity, magnetic response and reusability. PS-MPCM can be potentially applied for magnetic localization temperature regulation.

Energy dissipation in phase change salogels under shear stress

Phase change salogels are physical networks designed to shape stabilize salt hydrate phase change materials (PCMs) and inhibit the leakage of molten PCM. In contrast to chemically crosslinked gels, salogels can restructure by breaking of prior and reforming of new bonds. Therefore, salogels are susceptible to dissipate energy during deformations due to the nature of physical bonds. In the present work, different concentrations of diethylenetriamine, as a physical crosslinker, were added to a constant concentration of polyvinyl alcohol (PVA) in a high-salinity environment of a fluid inorganic PCM (lithium nitrate trihydrate), and network viscoelasticity was studied using oscillatory rheology. The energy dissipated was calculated by computing the area inside Lissajous stress-strain curves performed at various strain amplitudes and a constant frequency of 1 rad/s. The results of energy dissipation as a function of salogels' crosslinker concentration has a minimum when crosslinker concentration is ≅ 5–7 wt%. tes with the maximum point in the salogels' shear modulus graph. Lissajous plots' intracycle moduli analysis were used to quantify the observed non-linear behavior within a cycle of oscillation and proposed internal structure changes during deformation. Three regions based on the variation of dissipation energy with strain amplitudes (γ) for each salogel network were identified: region I (γ < ∼10%): linear viscoelastic region, region II (∼10% < γ < ∼100%): intermediate strain region with shear thickening behavior and, region III (γ > ∼100%): large deformation region with shear thinning behavior. Our results show that while most bonds are breaking at high strain amplitudes, there is a possibility of interchain reformation at intermediate shear strains due to the polymer chain alignment, which can slow down energy dissipation in this region. This study enhances the fundamental understanding of salogels’ microstructural response to non-linear deformation, which would benefit energy storage applications subjected to large deformations such as conformable packs and pillows.