Refrigerant Materials Research Articles

Utilizing Phase Change Materials for Sun-Powered Refrigerators: Experimental Validation in Outdoor Environments

Utilizing Phase Change Materials for Sun-Powered Refrigerators: Experimental Validation in Outdoor Environments

Kinetic origin of hysteresis and the strongly enhanced reversible barocaloric effect by regulating the atomic coordination environment

Hysteresis is an inherent property of first-order transition materials that poses challenges for solid-state refrigeration applications. Extensive research has been conducted, but the intrinsic origins of hysteresis remain poorly understood. Here, we report a study of the kinetic origin of hysteresis and the enhanced barocaloric effect (BCE) in MnCoGe-based alloys with ~2% nonmagnetic In atoms. First-principles calculations demonstrate that substituting In atoms at Ge sites rather than Co sites results in a lower energy barrier, indicating a narrower hysteresis for the former. Combining neutron powder diffraction (NPD) with magnetic and calorimetric measurements completely verified the theoretical prediction. Electron local function (ELF) calculations further reveal the atomic coordination origin of regulated hysteresis due to weaker Co–Ge bonds when In atoms replace Ge, which is opposite to Co sites. Moreover, we experimentally investigate the BCE and find that although MnCo(Ge0.98In0.02) has a lower barocaloric entropy change ΔSP than does Mn(Co0.98In0.02)Ge, the reversible ΔSrev of the former is advantageous owing to a smaller hysteresis. The maximum ΔSrev of MnCo(Ge0.98In0.02) is 1.7 times greater than that of Mn(Co0.98In0.02)Ge. These results reveal the atomic-scale mechanism regulating hysteresis and provide insights into tailoring the functional properties of novel caloric refrigeration materials.

Tuning the Magnetocaloric and Structural Properties of La0.67Sr0.28Pr0.05Mn1-x Co x O3 Refrigeration Materials

Abstract The impact of the structural, magnetic, and magnetocaloric effect of perovskite manganites La0.67Sr0.28Pr0.05Mn1-x Co x O3 (x = 0.05, 0.075, and 0.10) is investigated. LSPMCO crystallizes as a rhombohedral structure with R-3c space groups. As the Co content increases, the cell volume expands, the Mn-O-Mn bond angle reduces, and the length of the Mn-O bond rises. The samples show irregular submicron particles under the Zeiss scanning electron microscopy. The particle size becomes larger with the amount of doping. The chemical composition of the samples is confirmed by X-ray photoelectron spectroscopy (XPS). The ferromagnetic (FM) to paramagnetic (PM) phase transition occurs near the Curie temperature (TC), and all transitions are second order phase transitions (SMOPT) characterized by minimal thermal and magnetic hysteresis. Critical behavior analysis indicates that the critical parameters of LSPMCO closely align with those predicted by the mean field model. The TC declines with Co doping and reaches near room temperature (302 K) at x = 0.075. The maximum magnetic entropy change (-Δ S M max) at x = 0.05 is 4.27(J/kg·K), and the relative cooling power (RCP) peaks at 310.81 J/K. Therefore, the system holds significant potential for development as a magnetic refrigeration material, meriting further professional and objective evaluation.

Large cryogenic magnetocaloric effect in Na5Gd4F(SiO4)4

The adiabatic demagnetization refrigeration based on the magnetocaloric effect of magnetic materials has been regarded as an effective technology to attain sub-Kelvin temperature. In this article, the magnetic properties and MCE of Na5Gd4F(SiO4)4 compound are investigated. Due to the high Gd3+ ion/anion ligand ratio and weak magnetic interaction, Na5Gd4F(SiO4)4 exhibits a large magnetic entropy change of 49.6 J·kg−1·K−1 under magnetic field change of 0–7 T at 2.6 K, which surpasses the commercial magnetic refrigerant Gd3Ga5O12 under the same conditions. Besides, its refrigeration capacity and the relative cooling power under magnetic field change of 0–7 T reaches up to 308.9 J·kg−1 and 406.7 J·kg−1, respectively. These properties indicate that Na5Gd4F(SiO4)4 compound is a promising magnetic refrigeration material.

The crystal structures, magnetic interactions and cryogenic magnetocaloric effects for NaGdXO4 (X=Si, Ti) compounds

The development of ultra-low temperature magnetic refrigeration technologies demands magnetic refrigeration materials with excellent properties. Hence, improving performances of magnetic refrigerants has always been a significant scientific issue in magnetic refrigeration field. In this article, the relationship of crystal structures, magnetic interactions and magnetocaloric effect (MCE) for NaGdSiO4 and NaGdTiO4 has been investigated. NaGdSiO4 and NaGdTiO4 both crystallizes orthogonal structure, but the significant difference of unit cell parameters and symmetries results in different arrangement of Gd atoms. The distorted crystal structure and weaker magnetic between Gd3+ ions make NaGdSiO4 exhibit larger MCE with the maximum magnetic entropy change (-∆SM) of 49.0J·kg-1·K-1 at 2.8K. Comparably speaking, NaGdTiO4, which is a quasi-triangular antiferromagnet, possesses a stronger magnetic interaction between Gd3+ ions with the maximum -∆SM of 31.9J·kg-1·K-1 at 2.6K. These results confirm the importance of magnetic interactions for magnetic refrigeration materials, and, more broadly, they highlight the significance of crystal structures in that field.

The second-order magnetic transformation and magnetocaloric effect in all-d-metal Heusler ribbon Ni35Co15Mn34Ti16

The new all-d-metal Heusler alloys with good mechanical properties are candidates for magnetocaloric materials compared other famous refrigeration materials. In this work, Ni35Co15Mn34Ti16 ribbon with a second-order magnetic transformation was investigated for magnetoclaoric effect. It crystalizes pure B2 structure at room temperature and undergoes a SOMT at Curie temperature in austenite (TCA = 358 K) between paramagnetic and ferromagnetic phase. A large saturation magnetization (MS) at 5 K is 166 emu/g. The maximum values of magnetic entropy change (−ΔSM) and the temperature-averaged entropy change TEC(10 K) reach 1.62(3.42) J kg−1 K−1 and 1.64 (3.44) J kg−1 K−1 with magnetic field change (ΔH) of 20(50) kOe, respectively, which are comparable to most of other all-d-metal Heusler alloys.

Enhanced magnetic refrigeration capacities of Er6FeSb2 by manganese substitution

Er6FeSb2 is a potential magnetic refrigeration material that can work at the liquid hydrogen temperature range. This work enhances the magnetic refrigeration performance of Er6Fe1-xMnxSb2 by Mn substitution. Mn doping increases the cell volume while maintaining the compound’s crystal structure type. It also results in an increase in the charge density distribution between Er1 and Fe/Mn. As the Mn content increases, the ferromagnetic exchange is enhanced, and the TC continuously increases. The Mn doping induces spin reorientation at low temperature, transforming compounds from traditional magnetocaloric effects to table-like magnetocaloric effects, greatly enlarge the cooling temperature range. When the content of Mn increases from x = 0 to x = 0.3, the δTFWHM increases from 26 K to 62 K, the −(ΔSM)max decreases from 12.1 J/(kg·K) to 5.9 J/(kg·K), and the RCP first increases and then decreases, reaching the maximum value of 435.0 J/kg at x = 0.2. This study opens a new path for the search of magnetic refrigeration material with large cooling temperature range.

Gd Metal-Organic Framework Thin Film for On-Chip Local Magnetic Refrigeration.

Dense metal-organic frameworks with high spin paramagnetic nodes are competitive materials for cryogenic magnetic refrigeration, particularly in applications for which local cooling is advantageous. We focus on obtaining thin films of gadolinium formate, which has a large volumetric magnetocaloric effect. Continuous and homogeneous deposits of gadolinium formate are successfully formed on silicon by means of aerosol jet printing, with control over the film thickness from 0.35 μm up to 2.5 μm. The excellent cooling power of the deposits is evidenced via direct measurements of the cooling of a 200 μm silicon wafer down to sub-K temperatures by a single demagnetization from 1 T and 2 K, thereby demonstrating the potential of this approach for on-chip local magnetic refrigeration.

HoDyGdCoAl high-entropy amorphous alloys working at full temperature range for hydrogen liquefaction with large magnetocaloric effects

Cryogenic magnetic refrigeration materials based on magnetocaloric effect can be used for hydrogen liquefaction. In this work, glass formation ability (GFA), magnetocaloric effect (MCE), refrigeration performance of melt-extracted HoDyGdCoAl amorphous ribbons have been investigated. Amorphous ribbons undergo a second order magnetic phase transition which achieve a table-like behavior broaden the range of magnetic transition temperature in hydrogen liquefaction.The maximum magnetic entropy change (-ΔSmaxM), the δTFWHM and the refrigeration capacity (RC) achieved 10.9 J/ (kg K), 84.2 K and 742.4 J/ kg (x = 5) and 11.2 J/ (kg K), 69.8 K and 643.0 J/ kg (x = 20) under a magnetic field change of 7 T, respectively. Combining wide magnetic transition temperature and large refrigerant capacity, the present amorphous ribbons can be used as potential magnetic refrigerant materials in hydrogen liquefaction temperature region.

Magnetic properties and large low-field magnetocaloric effect of RFe2Si2 (R = Ho, Tm) compounds

Nowadays, magnetic refrigerant technology has drawn much attention for its environmental friendliness. Those magnetic materials possessing giant low-field magnetocaloric effect (MCE) performance are of great importance for practical applications, especially at low temperatures. Herein, we present a detailed study on polycrystalline magnetocaloric compounds HoFe2Si2 and TmFe2Si2. HoFe2Si2 exhibits a transition from antiferromagnetic to paramagnetic phase at 2.2 K, while no long-range magnetic ordering is observed in TmFe2Si2 even temperature down to 2 K. For both compounds, they showed large low-field magnetic entropy change (−ΔSM) with the peak values of 10.6 and 7.9 J kg−1 K−1 under field change of 0–2 T for HoFe2Si2 and TmFe2Si2, respectively, which is comparable or even larger than some low-temperature magnetocaloric materials. In addition, the characteristic of second-order magnetic transitions of both compounds were confirmed on basis of Arrott plots and mean-field theory criterion. The low magnetic ordering temperatures, large low-field MCE performance along with the feature of second order phase transition for HoFe2Si2 and TmFe2Si2 indicate that both compounds are promising candidate for magnetic refrigerant materials at liquid helium temperature.

Magneto-mechanical coupling in ferromagnetic shape memory alloys: Mechanical experimental investigation under magnetic field in NiMnGaCu alloy

Ferromagnetic shape memory alloys attracted increasing interest as multicaloric materials for solid state refrigeration. The most effective field coupling is achieved through the combination of the magnetic and mechanical induction of thermoelastic martensitic transformation. In the present work, we present an experimental investigation on NiMnGaCu polycrystalline cast alloy, by means of an experimental setup for compression tests in isothermal conditions under a longitudinal magnetic field. The setup has been ad hoc designed and developed specifically for this purpose. In this way, we can measure the elastocaloric and magnetocaloric effect at the same time. Moreover, the evolution of the entropy changes ΔS and the functional caloric parameters vs the magnetic field is evaluated. The application of magnetic field seems to act like a supplementary mechanical longitudinal stress. These preliminary results are fundamental to achieve a comprehensive understanding and modeling of coupled multicaloric phenomena.

Effect of Cu addition on the physical and mechanical properties of a Ni–Mn–In–Co polycrystalline shape memory alloy

The martensite transformation (MT), magnetocaloric effect (MCE), and mechanical properties of the polycrystalline Ni46Mn36In14Co4 (Co4) alloys with doping of 4 at.% Cu were examined. A large magnetization change (ΔM, 92 emu/g), large magnetic entropy change (ΔSM, 37.3 J kg−1K−1), high refrigerant capacity (RC, 261 J kg−1), relatively high sensitivity to magnetic fields (2.8 K/T), and two-way magnetic-field-induced MT were attained at approximately room temperature. Moreover, the compressive fracture strength and strain of the alloy reached 335 MPa and 7.4 %, respectively. Finally, the mechanism of the excellent combination properties of the Ni42Mn36In14Co4Cu4 (Co4Cu4) alloy was discussed. This study can aid in the development of high-performance magnetic refrigeration and intelligent actuator materials.

Superhydrophobic stereocomplex-type polylactide/ultra-fine glass fibers aerogel for passive daytime radiative cooling

Passive daytime radiative cooling (PDRC) technology offers a green and sustainable strategy for cooling, eliminating the need for external energy sources through its exceptional efficiency in heat radiation and sunlight reflection. Despite its benefits, the widespread usage of non-biodegradable PDRC materials has unfortunately caused environmental pollution and resource wastage. Furthermore, the effectiveness of outdoor PDRC materials can be significantly diminished by rainfall. In this work, a superhydrophobic composite aerogel composed of stereocomplex-type polylactide and ultra-fine glass fiber has been successfully developed through simple physical blending and freeze-drying, which exhibits low thermal conductivity (36.26 mW m−1 K−1) and superhydrophobicity (water contact angle up to 150°). Additionally, its high solar reflectance (91.68 %) and strong infrared emissivity (93.95 %) enable it to effectively lower surface temperatures during daytime, resulting in a cooling effect of approximately 3.8 °C below the ambient temperature during the midday heat of summer, with a cooling power of 68 W/m2. This aerogel offers an environmentally friendly and sustainable approach for the utilization of radiative refrigeration materials, paving the way for environmental protection and sustainable development.

Enhancing elastocaloric performance: Ti-doped Co–V-Ga bulk polycrystalline alloys with minimal stress hysteresis

Currently, practical applications of shape memory alloy (SMA) solid elastocaloric refrigeration materials are limited by low elastocaloric effect (eCE), high applied stress, and large stress hysteresis (Δσhys). Here, we introduce a composition design strategy using Ti-doped Co–V-Ga SMAs to address these challenges. We combine first-principles calculations and experiments to verify this strategy. Our results show that the lattice distortion caused by the significant difference in atomic radius after Ti doping produces a solid solution strengthening effect inside the alloy, which significantly improves the superelasticity of the alloy, delays the plastic deformation of the austenite phase, and the volume fraction of martensitic transformation increases significantly. The newly developed Co51.7V31.3Ga16Ti1 bulk polycrystalline alloy exhibits a remarkable adiabatic temperature change (ΔTad) of −10 K at room temperature under a low stress of 400 MPa, a minimum Δσhys of 18 MPa, and a high coefficient of performance COPmat of 31.9. Importantly, the 100-cycle loading-unloading test at 350 MPa is done, and it reveals that the ΔTad for the Ti0 alloy was only 3.9 K, while it reached 6.2 K for the Ti1 alloy, marking a noteworthy 59 % performance enhancement. From the simplicity of the fabrication process to the comprehensive performance of the material, it exhibits a promising advantage for practical cooling applications This study presents a feasible design strategy for large-scale production of high-performance bulk polycrystalline alloys with high eCE, low stress, and Δσhys.

Magnetic properties improvement in La0.67Sr0.33MnO3 perovskite powder with praseodymium / nickel doping

Among refrigeration materials, AMnO3 has garnered significant attention due to its unique physical properties, such as the magnetocaloric effect. In this study, we synthesize La0.67Sr0.33-xPrxMn0.975Ni0.025O3 (LSPMNO x=0.05, 0.10, and 0.15) using the sol-gel method. We explored room-temperature refrigeration materials by adjusting the doping levels of Pr ions. All samples, analyzed using XRD, HRTEM, and SAED, exhibit single-phase structures belonging to the R-3c space group. SEM, EDS, and TEM observations revealed that the samples are submicron particles with a uniform distribution of elements. MPMS test results indicate that LSPMNO undergoes a second order magnetic phase transition. With increasing Pr content, the Curie temperature (TC) gradually decreases, while the magnetic entropy change (∆SM) and relative cooling power (RCP) increase. Notably, La0.67Sr0.28Pr0.15Mn0.975Ni0.025O3 achieves an RCP of up to 306.63 J/kg, which is 74.79 % that of Gd.

Exploring Magnetocaloric Materials for Sustainable Refrigeration near Hydrogen Gas Liquefaction Temperature

AbstractMagnetocaloric materials have the ability to undergo temperature changes when subjected to varying magnetic fields. These materials are of interest due to their potential for innovative cooling applications. This review article summarizes materials that exhibit magnetic ordering within the temperature range required for gas liquefaction and explores their potential applications through the magnetocaloric effect (MCE). The gas liquefaction temperature range is typically assumed to be 20–77 K, however, this study specifically summarizes materials that have a transition temperature near to the hydrogen liquefaction temperature (≈20K). This review article aims to showcase ongoing research on magnetic materials for hydrogen liquefaction. Driven by the depletion of natural resources and environmental concerns, the search for environmentally sustainable fuels has intensified, making hydrogen a promising alternative. However, the liquefaction of hydrogen is highly energy‐intensive. The investigation focuses on identifying and understanding these materials and assessing their suitability for environmentally friendly and sustainable cooling technologies. By harnessing the magnetocaloric effect, these materials exhibit temperature changes in response to an applied magnetic field, offering advantages over traditional cooling methods that are 20–50% more efficient. The review aims to furnish researchers with essential information that can help modify magnetocaloric effect (MCE) materials, enabling them to achieve the desired magnetic ordering temperature conducive to the liquefaction of hydrogen.

Multi-objective optimization and 3E analysis for solar-driven dual ejector refrigeration and phase change material as thermal energy storage

Ejector refrigeration cycles have garnered attention due to their inherent advantages, including simplicity, the ability to leverage low-temperature energy sources, and reduced reliance on high electrical power requirements. Optimizing these systems becomes pivotal, given the inherent challenges of low efficiency in ejector refrigeration cycles. This study explores an ejector refrigeration cycle incorporating a secondary ejector to recover expansion energy from the condenser. Solar collectors provide the necessary heat for the cycle, utilizing phase change materials for thermal storage. Initially, the impact of five key parameters, generator temperature, condenser temperature, evaporator temperature, collector area, and storage tank volume, on the cycle's performance is thoroughly investigated. Subsequently, a three-objective optimization is executed, resulting in optimal values for the mentioned parameters: 83.4 °C for the generator temperature, 35.8 °C for the condenser temperature, 6.8 °C for the evaporator temperature, 82 m2 for the collector area, and 4 m3 for the storage tank volume. The analysis of energy, exergy and exergeoeconomics for the optimal point showed that the exergy efficiency for the ejector and solar cycle is 6.78 % and 10.74 %, respectively. Also, the COP of the refrigeration cycle was obtained as 0.1858. The results showed that the solar fraction is equal to 65.4 %, and the highest amount of exergy destruction is related to solar collectors, which is equal to 8.136 kW.

Achieving Ultrahigh Electrocaloric Response in (Bi0.5Na0.5)TiO3-Based Ceramics through B-Site Defect Engineering.

Lead-free electrocaloric (EC) ferroelectrics are considered ideal for the next generation of environmentally friendly solid-state refrigeration materials. However, their inferior performance compared to lead-based materials significantly restricts their potential application. According to phase-field simulations, it is predicted that the pinning effect of a moderate number of defects can effectively enhance the reversible polarization response associated with the entropy change. Herein, sodium-bismuth titanate (BNT) ceramics with high spontaneous polarization are selected to construct B-site defects by introducing Li+ and Nb5+. Under an electric field of 6 kV mm-1, ultrahigh EC temperature changes of ΔTpos = 1.77 and ΔTneg = 1.49 K are achieved at 65 °C by direct measurement (ΔTneg > 1 K over 55-120 °C). Furthermore, ΔTneg remains above 0.70 K in the temperature range from 25 to 130 °C, exhibiting immense potential for practical applications. This study offers a promising direction for optimizing the EC response in defect systems.

A cryogenic magnetic refrigerant: Magnetocaloric study of EuB2O4 compound

Adiabatic demagnetization refrigeration (ADR) technology has the advantage of not relying on helium-3 resources and gravity compared to traditional ultra-low temperature refrigeration technology. The key to the development of ADR technology is finding magnetic refrigeration materials with brilliant magnetocaloric properties. In this study, polycrystalline EuB2O4 was successfully prepared by solid-phase reaction method. The analysis of magnetic susceptibility curves and first-principles calculations reveals a magnetic phase transition from antiferromagnetic (AFM) to paramagnetic (PM) of EuB2O4, with TN = 0.72 K. The magnetic entropy change (-ΔSM) is evaluated up to 5 T, with the maximum value of 19.4 J·kg−1K−1 (88.7 mJ·cm−3K−1), 35.0 J·kg−1K−1 (160.0 mJ·cm−3K−1) and 50.8 J·kg−1K−1 (232.2 mJ·cm−3K−1) at around T = 1.3 K and under μ0ΔH = 1 T, 2 T and 5 T, respectively, which were significantly higher than those of the commercial magnetic refrigerant Gd3Ga5O12. The large -ΔSM suggest that EuB2O4 is a potentially great magnetic refrigerant for obtaining ultra-low temperature.

Enhanced cryogenic magnetocaloric performance and the existence of short-range magnetic correlations in frustrated diamond geometries

The magnetocaloric effect in the cryogenic temperature regime has gained enormous attention due to its application in the field of cryogenic refrigeration technology, which is required for quantum computing, space sciences and basic research activities. In this context, Gd- and Dy-based frustrated systems are considered as promising cryogenic magnetocaloric materials. Hence, in this paper the magnetic and magnetocaloric properties of GdTaO4, GdNbO4 and DyNbO4 are comprehensively investigated. Structural analysis suggests that these compounds crystallize in a monoclinic structure, wherein magnetic ions form an elongated diamond geometry. Analysis of magnetization, heat capacity and field-dependent magnetic entropy changes confirms the presence of short-range magnetic correlations in these compounds. Additionally, a remarkably large magnetic entropy change and relative cooling power are noted. The mechanical efficiency is found to be comparable to (or even better than) those reported for good magnetic refrigerants. Our study suggests that GdTaO4, GdNbO4 and DyNbO4 can be regarded as promising cryogenic magnetic refrigerant materials.