Value Of Entropy Change Research Articles

Spectroscopic and in silico evaluation of hesperetin, aglycone flavanone, as a prospective regulatory ligand for human salivary α-amylase

The insight into the binding mechanism of hesperetin, an aglycone flavanone, with human salivary α-amylase (HSAA), simulated under physiological salivary condition, was explored using various spectroscopic approaches and in silico method. Hesperetin effectively quenched the intrinsic fluorescence of HSAA and the quenching was mixed quenching mechanism. The interaction perturbed the HSAA intrinsic fluorophore microenvironment and the enzyme global surface hydrophobicity. The negative values of ΔG for thermodynamic parameters and in silico study revealed the spontaneity of HSAA-hesperetin complex while the positive values of enthalpy change (ΔH) and entropy change (ΔS) showed noticeable involvement of hydrophobic bonding in the stabilization of the complex. Hesperetin was a mixed inhibitor for HSAA with a K I of 44.60 ± 1.63 μM and having apparent inhibition coefficient (α) of 0.26. Macromolecular crowding, given rise to microviscosity and anomalous diffusion, regulated the interaction. Sodium ion (Na +) created high ionic strength, also, modulated the interaction. The in silico study proposed the preferential binding of hesperetin at the active cleft domain of HSAA with the least energy of −8.0 kcal/mol. This work gives a novel insight on the potentials of hesperetin as a future prospective medicinal candidate in the management of postprandial hyperglycemic condition. Communicated by Ramaswamy H. Sarma

Observation of superior magnetocaloric performance in multicomponent (Ce0.71Pr0.07Nd0.22)2Fe17-xAlx (x = 0.6, 0.8) compounds

Magnetocaloric effect (MCE) in multicomponent (Ce0.71Pr0.07Nd0.22)2Fe17-xAlx (x = 0.6, 0.8) alloys was studied using the heat capacity and magnetization data. Both the samples crystallize in a rhombohedral Th2Zn17-type structure. The maximum values of magnetic entropy change (-ΔSM) without hysteresis loss are found to be 1.19 Jkg−1K−1 and 1.23 Jkg−1K−1 with relative cooling power (RCP) values of 52.3 Jkg−1 and 66.4 Jkg−1 under an applied field change of 0–1 T for x = 0.6 and 0.8, respectively. Meanwhile, a wide working temperature range (44/54 K) and a large adiabatic temperature change (ΔTad) of 5.6/5.8 K were also achieved for the present compounds.

Excellent Magnetocaloric Performance of the Fe87Ce13-xBx (x = 5, 6, 7) Metallic Glasses and Their Composite.

The novel Fe87Ce13-xBx (x = 5, 6, 7) metallic glass (MG) ribbons were fabricated in this work. The compositional dependence of glass forming ability (GFA), magnetic and magnetocaloric properties of these ternary MGs, and the mechanism involved was investigated. The GFA and Curie temperature (Tc) of the MG ribbons were found to improve with the boron content, and the peak value of magnetic entropy change (-ΔSmpeak) reaches a maximum of 3.88 J/(kg × K) under 5 T when x = 6. Based on the three results, we designed an amorphous composite that exhibits a table-shape magnetic entropy change (-ΔSm) profile with a rather high average -ΔSm (-ΔSmaverage~3.29 J/(kg × K) under 5 T) from 282.5 K to 320 K, which makes it a potential candidate for the highly efficient refrigerant in a domestic magnetic refrigeration appliance.

Emergent evolution of first-order phase transitions from magneto-structural to magneto-elastic in MnCo1−y Fe y Ge1−x Si x alloys

The emergent evolution of first-order phase transitions from magneto-structural to magneto-elastic and magnetocaloric effect (MCE) have been investigated by X-ray diffraction, differential scanning calorimetry and magnetization measurements. Applying the isostructural alloying principle, the martensitic transition temperature (T M) increases effectively and the Curie temperatures of the two phases increase slightly by substituting the Si content (x). With an appropriate amount of Fe and Si content, an emergent first-order antiferromagnetic–ferromagnetic magnetoelastic transition with thermal hysteresis in the martensitic state occurs for MnCo0.7Fe0.3Ge1–x Si x (x = 0.15–0.40) alloys, which results from the decrease in the nearest-neighbor Mn–Mn distance. Moreover, the values of magnetic entropy change (ΔS M), refrigeration capacity (RC) and temperature-averaged entropy change (TEC, 10 K) with ΔH = 50 kOe reach −12.2 J kg−1 K−1, 112.8 J kg−1 and 11.4 J kg−1 K−1 for MnCo0.7Fe0.3Ge0.8Si0.2 undergoing the ferromagnetic magneto-structural transition in the Curie temperature window. The results facilitate the magnetocaloric/magnetoelastic performance and tunability of multiple phase states in a wider temperature range.

Evolution of structure, magnetic phase transition and magnetocaloric effect of GdNiSi1-xAlx (0 ≤ x ≤ 0.3) alloys

The magnetocaloric effects can be enhanced in GdNiSi1-xAlx (0 ≤ x ≤ 0.3) alloys by Al doping. The substitution amount is limited to x = 0.3. GdNiSi and GdNiSi0.9Al0.1 alloys exhibit an antiferromagnetic ground state and the phase transition temperatures are 13 K and 10 K under 0.05 T, respectively. GdNiSi0.8Al0.2 and GdNiSi0.7Al0.3 alloys exhibit a ferromagnetic ground state and the phase transition temperatures are 18 K and 26 K under 0.05 T, respectively. These alloys undergo the field-induced first-order metamagnetic transition from antiferromagnetic to ferromagnetic states. For Δμ0H of 0–7 T, the values of the maximum magnetic entropy change (the relative cooling power) are 7.7 J/kgK (173.1 J/kg), 11.4 J/kgK (303.2 J/kg), 14.3 J/kgK (447.9 J/kg) and 13.0 J/kgK (494.4 J/kg) in GdNiSi1-xAlx (x = 0, 0.1, 0.2 and 0.3) alloys.

Direct and inverse magnetocaloric effects in the antiferromagnetic rare earth (RE) rich RE6Ni2.25Al0.75 (RE = Dy, Ho and Er) compounds

The magnetic refrigeration (MR) by utilizing the magnetocaloric effect (MCE) of magnetic solids has been considered a promising, environmentally benign, energy-efficient cooling technology. However, the lack of promising magnetic substances has slowed the development of its active application. To identify suitable candidate materials, we herein identified the structural and magnetic properties together with the MCE and magnetocaloric performances of rare earth (RE) rich RE6Ni2.25Al0.75 (RE = Dy, Ho and Er) compounds. All the RE6Ni2.25Al0.75 compounds are confirmed to crystallized in orthogonal Ho6Co2Ga-type structure and underwent paramagnetic to antiferromagnetic magnetic transitions. Moreover, large direct (conventional) and inverse MCEs have been observed in all the RE6Ni2.25Al0.75 compounds. The values of peak magnetic entropy changes, temperature-averaged magnetic entropy changes with 5 K-lift and relative cooling powers under magnetic field change of 0–7 T are evaluated to be − 4.44 J/kg-K, − 4.38 J/kg-K and 230.6 J/kg for Dy6Ni2.25Al0.75, to be − 12.68 J/kg-K, − 12.26 J/kg-K and 378.2 J/kg for Ho6Ni2.25Al0.75, and to be − 17.52 J/kg-K, − 17.33 J/kg-K and 465.7 J/kg for Er6Ni2.25Al0.75, respectively.

Multi-principal rare-earth Gd-Tb-Dy-Ho-Er alloys with high magnetocaloric performance near room temperature

Magnetocaloric materials with enhanced magnetocaloric effect and high magnetic transition temperature are crucial for magnetic refrigeration, a novel cooling technology featuring high energy efficiency, low noise and superb environmental friendliness. In this study, a series of Gdx(TbDyHoEr)1-x (x=0.2–0.9) rare-earth alloys with a single-phase HCP (hexgonal-close-packed) structure, were developed utilizing a multi-principal element alloying strategy. It was found that the Gd0.8(TbDyHoEr)0.2 alloy exhibits a high magnetic transition temperature (i.e., ∼268 K), and concurrently enhanced magnetocaloric properties with a maximum magnetic entropy change value of 10.53 J kg−1 K−1 under a field change of 5 T and a refrigerant capacity value of 751.8 J kg−1. Notably, for these multi-principal element alloys, the maximum magnetic entropy change is essentially linearly correlated with the configuration entropy of mixing while the magnetic transition temperature scales with the de Gennes factor, which can be interpreted as a manifestation of ideal solid solutions. This work provides important implications for designing high-performance magnetocaloric materials for magnetic refrigeration.

Investigation of thymine as a potential cancer biomarker employing tryptophan with nanomaterials as a biosensor

Tryptophan and tryptophan-based nanomaterials sensors in a solution have been developed to directly evaluate thymine. The determination of thymine has been done via quenching of the fluorescence of tryptophan and tryptophan-based nanomaterials such as graphene (Gr), graphene oxide (GO), gold nanoparticles (AuNPs), gold-silver nanocomposite (Au-Ag NC) in a physiological buffer. As the concentration of thymine rises, the fluorescence of tryptophan and tryptophan/nanomaterials becomes less intense. Trp, Trp/Gr, and tryptophan/(Au-Ag) NC systems' quenching mechanisms were dynamic, but tryptophan /GO and tryptophan/AuNPs' quenching mechanisms were static. The linear dynamic range for the determination of thy by tryptophan and tryptophan /nanomaterials is 10 to 200 μM. The detection limits for tryptophan, tryptophan /Gr, tryptophan /GO, tryptophan /AuNPs, and tryptophan/Au-Ag NC were 3.21, 14.20, 6.35, 4.67and 7.79 Μm, respectively. Thermodynamic parameters for the interaction of the Probes with Thy include the enthalpy (H°) and entropy (S°) change values, were assessed, as well as the binding constant (Ka) of Thy with Trp and Trp-based nanomaterials. A recovery study was conducted utilizing a human serum sample after the addition of the required quantity of the investigational thymine.

Effect of Nd doping on the crystallographic, magnetic, and magnetocaloric properties of NdxGd3−xCoNi

The crystal structure, magnetic and magnetocaloric properties, and the critical behavior of representative compounds in the pseudo-ternary NdxGd3−xCoNi series have been investigated (x = 0.15, 0.5, 1.0, and 1.5). All these phases are isotypic with the parent compound Gd3CoNi, crystallizing with the monoclinic Dy3Ni2-type (mS20, C2/m, No. 12). All samples present a paramagnetic to ferromagnetic (PM-FM) second order phase transition with decreasing Curie temperature as the Nd concentration is increased (TC = 171, 150, 120, and 96 K, respectively) and, at lower temperatures, there is a spin reorientation, which leads to a complex magnetic ground state. The critical exponents (β, γ, and δ) have been retrieved for the PM-FM transitions. On the one hand, in x = 0.15, 0.5, and 1.5 the value of γ ≈ 1 indicates that the magnetic interactions are long-range order while the values of β point to a certain deviation from the 3D-Heisenberg universality class; on the other hand, NdGd2CoNi has a particular critical behavior, as β is close to the mean field model while γ is close to the uniaxial 3D-Ising one. Concerning the magnetocaloric properties, the magnetic entropy change and refrigerant capacity present competitive values, interesting for cryogenic applications. Finally, the thermal diffusivity values of these compounds are extremely good for practical magnetocaloric refrigeration systems, as they are in the range 1.5–3 mm2/s.

Adsorption kinetic and thermodynamic studies of the dyeing process of pineapple leaf fibre with berberine dye and modeling of associated interactions

There are on-going investigations on the utilization of pineapple leaf fibre (PALF) as a cheap, safe, and eco-friendly natural fibre. The present work aimed to improve PALF preparation using ultrasonication, investigate the adsorption kinetic and thermodynamic aspects of PALF dyed with berberine dye, and to assess their associated molecular interactions. It was found that concomitant PALF exposure to NaOH solution (5% w/v) plus ultrasonication for 20 min successfully removed non-cellulosic substances from the fibre surface in a very much shorter time compared with the traditional non-ultrasound assisted method (24 h). An adsorption isotherm study of dyeing, the treated fibre with the natural yellow dye berberine revealed a strong adsorption dependence on the pH of the berberine solution with optimal uptake occurring at pH 9–10. A deeper assessment of the mode of dye binding was undertaken by DFT − based calculations on a model cellulose unit and berberine. It revealed that the interaction between berberine and cellulose (PALF) at pH 9.00 was likely to be substantially stronger than at lower pH. From the adsorption kinetic results, a higher affinity and more dye uptake were observed before equilibrium was reached. The adsorption isotherm data could be represented by the Langmuir isotherm (R 2 > 0.99). The enthalpy change (ΔH°) and entropy change (ΔS°) values of dyeing were found to be −17.0 kJ mol−1 and −19.4 J mol−1 K−1 respectively, which pointed to the dye adsorption being an exothermic process. The negative standard affinity (Δµ o) values at the different temperatures of 30, 60, and 80 °C were −11.2, −10.6, and −10.2 kJ mol−1, respectively. It affirmed the dye adsorption process as a spontaneous one. Higher temperatures resulted in a lower affinity and reduced dye uptake compatible with the process being exothermic. Berberine is a potentially useful natural dye for PALF without the need for additives.

Critical behavior and room temperature magnetocaloric effect of La-doped Pr0.7Sr0.3MnO3 compounds

In this work, we present the critical and the magnetocaloric properties of Pr0.7-xLaxSr0.3MnO3 compounds around room temperature. The samples exhibit a single phase with an orthorhombic structure. However, the lattice parameters increase with an increase in La content (x). The Curie temperature (TC) of the ferromagnetic (FM)-paramagnetic (PM) phase transition of compounds increases from 256 K for x = 0–319 K for x = 0.3. We observed a large magnetocaloric effect with high maximum magnetic entropy change (|ΔSmax|) values occurring around room temperature, corresponding to |ΔSmax| = 6.65 and 5.21 J/kgK under a magnetic field change (ΔH) of 50 kOe for x = 0.2 and 0.3, respectively. We also pointed out that the change in |ΔSmax| obeys an exponential function of ΔH (|ΔSmax| ∼ ΔHn), where the value of field exponent (n) is approximately 0.52. Furthermore, the critical behavior around TC for compounds with x = 0.2 and 0.3 has been investigated. The results indicate that these compounds undergo a second-order phase transition with the critical parameters (β = 0.311, γ = 1.137, and δ = 4.656 at TC = 298.4 K for x = 0.2; and β = 0.319, γ = 1.098, and δ = 4.442 at TC = 318.7 K for x = 0.3) that are quite close to those expected for the 3D-Ising model. This suggests the existence of the short-range magnetic interactions in these compounds.

Effects of Ca substitution on magnetic and magnetocaloric properties in PrBa1-xCaxMn2O6 system

In this study, we have examined the effect of Ba substitution by Ca on the magnetic, and magnetocaloric properties of PrBa1-xCaxMn2O6 (x = 0, 0.2 and 0.3) double perovskite manganites produced using sol-gel method. The samples were indexed in orthorhombic structure (with space group of Pbnm). The temperature-dependent magnetization, M(T), measurements indicate that all samples have a magnetic phase transition from ferromagnetic (FM) to paramagnetic (PM) state with increasing temperature. Curie temperature (TC) decreases with increasing Ca content in the main lattice. From the magnetic field dependence of magnetization measurements, M(H), maximum magnetic entropy change (−ΔSMmax) values were calculated as 4.07, 4.12, and 5.04 Jkg−1K−1 under 5 T for PrBaCaMn2O6, PrBa0.8Ca0·2Mn2O6, and PrBa0.7Ca0·3Mn2O6 samples, respectively. Relative cooling power (RCP) values below 5 T were determined as 214.16, 227.14 and 279.62 Jkg-1 based on the increasing Ca content. The −ΔSMmax and RCP values enhance with increasing Ca content, respectively. The nature of the phase transition, checked by Banerjee criterion and Franco's universal master curves, was found to be second order magnetic phase transition (SOMT).

Synthesis of nanostructured novel ion-imprinted polymer for selective removal of Cu2+ and Sr2+ ions from reverse osmosis concentrated brine

This study aims to prepare an ion-imprinted polymer (IIP) using copper sulfate as a template and potassium persulfate as an initiator to selectively adsorb copper ions (Cu2+) from aqueous solutions and in an attempt to also test its applicability for removing strontium ions (Sr2+). The prepared polymer was denoted by IIP-Cu. Various physical and chemical characterizations were performed for the prepared IIP-Cu. The scanning electron microscopy and transmission electron microscopy analyses confirmed the cavities formed after the removal of the template. It also indicated that the IIP-Cu had a rough and porous topology. The X-ray photoelectron spectroscopy confirmed the successful removal of the Cu template from IIP-Cu. The Brunauer-Emmet-Teller revealed that the surface area of IIP-Cu is as high as 152.3 m2/g while the pore radius is 8.51 nm. The effect of pH indicated that the maximum adsorption of Cu2+ was achieved at pH 8 with 98.7%. Isotherm studies revealed that the adsorption of Cu2+ was best explained using Langmuir models with a maximum adsorption capacity of 159 mg/g. The effect of temperature revealed that an increase in temperature had an adverse impact on Cu2+ removal from the aqueous solution, which was further confirmed by thermodynamic studies. The negative value of standard enthalpy change (−4.641 kJ/mol) revealed that the adsorption of Cu2+ onto IIP-Cu was exothermic. While the continuous increase in Gibbs free energy from −6776 kJ/mol to −8385 kJ/mol with the increase in temperature indicated that the adsorption process was spontaneous and feasible. Lastly, the positive value of the standard entropy change (0.023 J/mol.K) suggested that the Cu2+ adsorption onto IIP-Cu had a good affinity at the solid-liquid surface. The efficiency of the prepared IIP-Cu was also tested by studying the adsorption capacity using Sr2+ and real brine water. The results revealed that IIP-Cu was able to remove 63.57% of Sr2+ at pH 8. While the adsorption studies revealed that the experiment was best described using the Langmuir model with a maximum adsorption capacity of 76.92 mg/g. Additionally, IIP-Cu was applied in a real brine sample, which consisted of various metal ions. The highest percentage of Cu2+ removal was 90.6% and the lowest was 65.63% in 1:4 and 1:1 brine ratios, respectively. However, this study indicates the successful application of IIP-Cu in a real sample when it comes to the effective and efficient removal of Cu2+ in a solution consisting of various competing ions.

Photogenic MnO2/Ag metal nanocomposites and their dye adsorbing activities

Manganese dioxide/silver (MnO2/Ag) nanoparticles were fabricated by using KMnO4-NaBH4 redox reaction at room temperature. The optical and structural properties of MnO2/Ag were determined using UV–visible and Fourier transform infrared spectroscopies. The morphology was established with scanning and transmission electron microcopies, and X-ray diffraction. MnO2/Ag showed excellent adsorbing activity to the removal of Congo red. The various kinetic models were used to determine the rate of dye removal. Congo red adsorption onto MnO2Ag proceeds through the pseudo-second-order kinetic model. Langmuir adsorption capacity (Q0max = 97.1 mg/g), and sorption intensity (n = 1.6) were estimated with Langmuir and Freundlich adsorption isotherm models for 250 mg/L Congo red. Elovich model suggest the adsorption of Congo red with the MnO2Ag proceeds through the film diffusion. The positive values of enthalpy changes (ΔH0), entropy changes (ΔS0), and negative Gibbs free energy changes (ΔG0) showed that the Congo red adsorption process was endothermic, spontaneous, and chemisorption process followed with physical mechanism. The results showed that the removal efficiency decreases from 98% to 89% after the six consecutive experiments.

The study of magnetocaloric effect in the electrodeposited thin films of M3[Cr(CN)6]2·zH2O (M = Fe and Cr)

The electrodeposited thin films of Prussian blue analogs, Fe3[Cr(CN)6]2·zH2O (FeCr) and Cr3[Cr(CN)6]2·zH2O (CrCr), were investigated, focusing in particular on their magnetocaloric properties. Both samples show magnetocaloric effect (MCE) reaching the peak values of magnetic entropy change of 10 J·kg−1K−1 for FeCr and 0.71 J·kg−1K−1 for CrCr at μ0ΔH = 5 T, and 23 K and 218 K, respectively. The temperature averaged entropy change (TEC) was evaluated in the wide temperature range, resulting in TEC(3) = 9.9 J·kg−1K−1 and TEC(20) = 8.7 J·kg−1K−1 for FeCr, and TEC(3) = 0.71 J·kg−1K−1 and TEC(20) = 0.67 J·kg−1K−1 for CrCr. The magnetocaloric master curves indicate the second-order phase transition in FeCr and the presence of acomplicated magnetically ordered phase of CrCr below the corresponding critical temperature.

Effect of Mn substitution on plateau pressure regulation of the Ti0.92Zr0.1Cr1.6−xMnxFe0.4 alloys for primary hydrogen compressor

The Ti0.92Zr0.1Cr1.6−xMnxFe0.4 (x = 0.15, 0.3, 0.45, 0.6 at%) alloys were synthesized by vacuum electric arc furnace. The effect of Mn substitution on plateau pressure regulation of these alloys was investigated for the primary hydrogen compressor. With increasing Mn content, the hydrogen absorption/desorption plateau pressures of the Ti0.92Zr0.1Cr1.6−xMnxFe0.4 (x = 0.15, 0.3,0.45,0.6 at%) alloys increased, the plateau slope factor decreased, meanwhile, both enthalpy and entropy change values decreased. The Ti0.92Zr0.1Cr1.0Mn0.6Fe0.4 alloy had the best comprehensive performance. Based on the pressure composition isotherms measurement, the plateau pressure and hydrogen storage capacity were obtained at 298–363 K. The hydrogen absorption/desorption curves of the Ti0.92Zr0.1Cr1.0Mn0.6Fe0.4 alloy at 353 and 363 K were firstly tested by experiment method. At 298 K, the hydrogen absorption plateau pressure and maximum capacity were 7.82 MPa and 1.79 wt%. At 363 K, the hydrogen desorption plateau pressure and maximum capacity were 27.21 MPa and 1.54 wt%. Hydrogen pressure from 8 MPa to 25 MPa was successfully obtained at 298–363 K, satisfying operating temperature and pressure requirements for the primary hydrogen compression materials.

Removal of Chromium (VI) from Aqueous Solution Using Activated Carbon Derived from Modified Bambara Nut Shells (Vignasubterranea (L.) verdc.)

Adsorption of Cr (VI) ions from aqueous solution using activated carbon derived from Bambara nut shells (BBNSAC) was investigated using batch adsorption technique. The maximum removal of Cr (VI) ions onto BBNSAC corresponding to 68.00 mg/g was achieved at pH 2, adsorbent dosage 0.01 g and contact time of 60 minute. The Equilibrium data of adsorption revealed that the adsorption of Cr (VI) ions showed better fitting to Langmuir isotherm in comparison to Freundlich, Temkin and Dubinin-Radaushkevich isotherm models. The value of Langmuir monolayer coverage was 55.56 mg/g. However, the kinetics of adsorption was best described by pseudo second-order model with highest correlation coefficient, R2 value of 0.984. Thermodynamics parameters of adsorption revealed negative value of Gibb’s free energy (∆G) indicating a feasible and spontaneous adsorption process whereas the positive value of change in enthalpy (∆H) indicates that the adsorption process was endothermic in nature while the positive value of change in entropy (∆S) revealed that there is an increase in randomness at solid-solution interface during adsorption process.

Adsorption of Tetracycline by Magnetic Mesoporous Silica Derived from Bottom Ash—Biomass Power Plant

In recent years, the contamination of the aquatic environment with antibiotics, including tetracyclines, has drawn much attention. Bottom ash (BA), a residue from the biomass power plant, was used to synthesize the magnetic mesoporous silica (MMS) and was utilized as an adsorbent for tetracycline (TC) removal from aqueous solutions. The MMS was characterized by Fourier transform-infrared (FTIR), X-ray diffraction (XRD) pattern, and scanning electron microscopy (SEM). Optimum conditions were obtained in overnight incubation at 60 °C, a pH of 6–8, and an adsorption capacity of 276.74 mg/g. The isotherm and kinetic equations pointed to a Langmuir isotherm model and pseudo-first-order kinetic optimum fitting models. Based on the very low values of entropy changes (ΔS°), the negative value of enthalpy changes (ΔH°) (−15.94 kJ/mol), and the negative Gibbs free-energy changes (ΔG°), the adsorption process was physisorption and spontaneous.

Manipulation of the microstructure and properties of La(Fe,Si)13 alloys via solidification kinetics

The microstructural features of as-cast alloys are predominantly influenced by the fabrication process, which eventually determine the properties. In the present work, we demonstrate that the microstructure (e.g., composition, phase constitution and distribution) and the magnetocaloric properties of the La(Fe,Si)13 alloys can be effectively tailored by tuning the solidification kinetics. La(Fe,Si)13 alloys with different dimensions were prepared by suction casting and jet casting. Finite element (FE) simulations reveal a difference in the temperature gradient along the solidification path of the rapid solidification process. The microstructure difference between the edge and center regions in the as-cast ingots along the solidification direction is increased for the samples with larger diameter. This can be attributed to the different solidification kinetics as predicted by the FE simulations. More homogeneous microstructure can be observed in the samples with a smaller size. The largest magnetic entropy change value of 16 J/kg·K can be obtained in thin plates, which is comparable to that of master bulk alloy. Our thorough study of solidification mechanisms during rapid solidification provides research basis for manipulating the microstructure homogeneity and the related properties, which also paves the way for the study of other rapid-solidificated materials.

Relating microstructure to magnetocaloric properties in RE36Tb20Co20Al24 (RE = Gd, Dy or Ho) high-entropy metallic-glass microwires designed by binary eutectic clusters method

The new high-entropy metallic-glasses (HE-MGs) are designed by using Dy and Ho to replace Gd in Gd36Tb20Co20Al24 alloy based on the binary eutectic clusters method. Compared with the equiatomic Gd25Tb25Co25Al25 HE-MG, the non-equiatomic RE36Tb20Co20Al24 (RE = Gd, Dy, or Ho) alloys show better glass-forming ability, which is attributed to the deep binary eutectic compositions used for alloy design. All RE36Tb20Co20Al24 alloys undergo second-order magnetic transition. An extreme peak value of magnetic entropy change is obtained as 10.3 J kg–1 K–1 (5 T) for the Ho36Tb20Co20Al24 alloy. In-situ high-energy synchrotron X-ray diffraction was conducted to observe the microstructural difference among non-equiatomic samples at cryogenic temperatures. The results indicate that Gd36Tb20Co20Al24 alloy possesses a relatively large average value of the dispersion of local clusters at a low-temperature range. This, combined with the critical exponent β close to 0.5 of Gd36Tb20Co20Al24 alloy, leads to its widest working temperature span among non-equiatomic samples. This work successfully establishes the connection between microstructure and magnetocaloric properties of HE-MGs, which is beneficial for understanding the physical mechanism of the magnetocaloric behaviors of HE-MGs.