High Configurational Entropy Research Articles

Preparation, phase stability, and magnetization behavior of high entropy hexaferrites

The polycrystalline SrFe12O19 samples deeply substituted up to at.67% by Al3+, Ga3+, In3+, Co3+, and Cr3+ cations with a high configurational mixing entropy were prepared by solid-phase synthesis. Phase purity and unit cell parameters were obtained from XRD and analyzed versus the average ionic radius of the iron sublattice. The crystallite size varied around ∼4.5μm. A comprehensive study of the magnetization was realized in various fields and temperatures. The saturation magnetization was calculated using the Law of Approach to Saturation. The accompanying magnetic parameters were determined. The magnetic crystallographic anisotropy coefficient and the anisotropy field were calculated. All investigated magnetization curves turned out to be nonmonotonic. The magnetic ordering and freezing temperatures were extracted from the ZFC and FC curves. The average size of magnetic clusters varied around ∼350nm. The high values of the configurational mixing entropy and the phenomenon of magnetic dilution were taken into account.

(MgCoNiCuZn)O-coated ceramic membrane: Preparation, microstructure, and properties

Ceramic pristine membrane was prepared and coated with (MgCoNiCuZn)O slurry by dip-coating procedure. According to the XPS results, the high-entropy oxide was coated effectively on the pristine membrane surface. XRD measurement showed that a single-phase rock-salt structure was obtained in the coated-membrane calcined at 1000 °C. SEM measurements indicated that a uniform coating could be observed on the surface of the coated membranes and EDS exhibited approximately even distribution of five metals. The water contact angle increased when (MgCoNiCuZn)O was coated on the surface of membrane, which was attributed to the high configuration entropy. The porosity of coated membrane changed from 64.7% to 62.2% as the coating number, implying that coating had no significant effect on the porosity of pristine membrane. The coated membrane exhibited a high pure water flux and carbon retention. For the membrane coated with three layers of high-entropy ceramic, the pure water flux and rejection ratio of carbon black reached 706 L m−2 h−1·bar−1 and 96.54%, respectively. The coated membrane also exhibited good long-term stability and corrosion resistance under acidic or alkaline environment.

Inert Mg Incorporation to Break the Activity/Stability Relationship in High-Entropy Layered Hydroxides for the Electrocatalytic Oxygen Evolution Reaction

Ni-based layered double hydroxides (LDHs) have been demonstrated as the most active catalyst for the oxygen evolution reaction in alkaline media but suffer from poor stability. Herein, we report the rational breaking of the activity/stability trade-off by a strategy of inert Mg-involved high-entropy coordination. The as-developed high-entropy FeCoNiMg-LDH nanosheets exhibit not only high catalytic activity (302 mV at 100 mA cm–2) but also an unprecedented stability with almost no performance decline at a large current density of 300 mA cm–2. The combined structural investigations and theoretical calculations reveal that the synergistic electronic coupling provides active Ni in desired electronic states, leading to an optimized adsorption energy of intermediates, while the construction of high configuration entropy as well as the formation of the Mg–O interfacial bond can effectively mitigate phase segregation and transformation and thus improve the stability. The current insights into unveiling the composition–activity–stability of high-entropy coordination may provide valuable guidance for the design of catalysts for various electrochemical reactions.

Supersaturation and dissolvable α-Cr phase enable superior oxidation resistance in FeCrNi medium-entropy alloys

Increasing Cr content in Fe-based alloys is expected to improve oxidation and corrosion resistances, but its effectiveness always degrades because of the over-doping induced precipitation of harmful σ-FeCr and Cr23C6 phases. In this study, the precipitation and oxidation behaviors of FexCrNi alloys were systematically investigated. It is found that the precipitation behavior could be controlled by adjusting the Cr content. The α-Cr phase precipitates at 800 °C in supersaturated FeCrNi medium-entropy alloy (MEA), while it is absent in Fe3CrNi alloy due to the lower Cr content. FeCrNi MEA shows much better oxidation resistance than Fe3CrNi, the oxidation rate constant of FeCrNi is two to three orders lower than that in the Fe3CrNi alloy. The oxidation activation energy of FeCrNi (545 kJ/mol) is much higher than that of the Fe3CrNi alloy (80 kJ/mol), which can be attributed to the synergistic effects of α-Cr dissolution, high configuration entropy and Cr supersaturation. Unlike σ-FeCr and Cr23C6 in stainless steels, the metastable α-Cr phase can be controllably introduced in FeCrNi as a “Cr resource”, and will dissolve during long-term oxidation to provide the required Cr element for the stabilization of the Cr2O3 scale. These discoveries shed new insights into the innovative design of stainless materials for heat-resistance structural applications.

On correlations between local chemistry, distortions and kinetics in high entropy nitrides: An ab initio study

High entropy alloys (HEAs) have triggered significant scientific interest due to their unusual structural stability combined with excellent mechanical and other functional properties. Recently, the high-entropy concept has also been applied to the field of protective coatings. We use ab initio calculations to provide an unbiased insight into their behavior at the atomic level. Namely, we focus on the interplay between high entropy (chemical complexity), sluggish diffusion, and (local) lattice distortions in the example of high configurational entropy sublattice nitride (HESN) ceramics. We show that the high entropy itself is not a guarantee for the sluggishness of diffusion (as quantified by migration barriers). Next, we propose a relation between the local distortions (measured by the width of lattice bond length distributions) and activation energies. The presented results provide examples that the core effects, characterizing the exceptional properties of HEAs, are system-specific and hence highlight the need for analyzing each system of interest individually.

High entropy effect on double exchange interaction and charge ordering in half doped Nd0.5Sr0.5MnO3 manganite

The entropy stabilized oxides i.e., the so-called high-entropy oxides are of great interest in recent time due to their intriguing physical properties. This new category of advanced materials is stabilized by the high configurational entropy of randomly mixed elements, where a specific lattice site is populated by five or more elements. The present study is devoted to explore the high entropy effect in well-known charge ordered manganite Nd0.5Sr0.5MnO3 where a delicate balance exists between the ferromagnetic double exchange and the antiferromagnetic superexchange interactions. Powder X-ray diffraction analyses confirm phase purity of the samples. FE-SEM imaging revealed the microstructure and elemental mapping confirmed the chemical homogeneity of the samples as well as nominal cationic composition. Bond valence sum (BVS) calculation using refinement parameters supports the expected cationic valence in all the samples. Replacement of Nd3+ by five trivalent cations as in (La0.1Pr0.1Nd0.1Gd0.1Bi0.1)Sr0.5MnO3 with larger average A-site ionic radius,<rA>and smaller size variance, σ2 compared with Nd0.5Sr0.5MnO3 dramatically suppressed the ferromagnetic double exchange interaction. This observation is in contrast with the expected variation in<rA>and σ2. In (La0.1Nd0.1Gd0.1Bi0.1Y0.1)Sr0.5MnO3 with smaller<rA> and marginally higher σ2 the ferromagnetic state ceases to exist. In both the multicationic compositions, a long-range antiferromagnetic state is evolved around 200 K with the retention of charge ordering. In the high entropy (La1/6Nd1/6Dy1/6Ca1/6Ba1/6Sr1/6)MnO3 composition with nominal<rA> and larger σ2 values the high temperature long-range ordering is completely suppressed and a new antiferromagnetic state is evolved at 45 K without manifestation of any charge ordering. This composition also avoids magnetic frustration unlike the dopant variant with larger σ2. The present investigation thus highlights the role of local lattice distortion or high entropy effect apart from the<rA>and σ2 in manganites.

High-Entropy Alloy Coatings Deposited by Thermal Spraying: A Review of Strengthening Mechanisms, Performance Assessments and Perspectives on Future Applications

Thermal spray deposition techniques have been well-established, owing to their flexibility in addressing degradation due to wear and corrosion issues faced due to extreme environmental conditions. With the adoption of these techniques, a broad spectrum of industries is experiencing continuous improvement in resolving these issues. To increase industrial-level implementation, state-of-the-art advanced materials are required. High-entropy alloys (HEAs) have recently gained considerable attention within the scientific community as advanced materials, mainly due to their exceptional properties and desirable microstructural features. Unlike traditional material systems, high-entropy alloys are composed of multi-component elements (at least five elements) with equimolar or nearly equimolar concentrations. This allows for a stable microstructure that is associated with high configurational entropy. This review article provides a critical assessment of different strengthening mechanisms observed in various high-entropy alloys developed by means of deposition techniques. The wear, corrosion, and oxidation responses of these alloys are reviewed in detail and correlated to microstructural and mechanical properties and behavior. In addition, the review focused on material design principles for developing next-generation HEAs that can significantly benefit the aerospace, marine, oil and gas, nuclear sector, etc. Despite having shown exceptional mechanical properties, the article describes the need to further evaluate the tribological behavior of these HEAs in order to show proof-of-concept perspectives for several industrial applications in extreme environments.

Cold Spray Coatings of Complex Concentrated Alloys: Critical Assessment of Milestones, Challenges, and Opportunities

Complex concentrated alloys (CCAs) are structural and functional materials of the future with excellent mechanical, physical, and chemical properties. Due to the equiatomic compositions of these alloys, cost can hinder scalability. Thus, the development of CCA-based coatings is critical for low-cost applications. The application of cold spray technology to CCAs is in its infancy with emphasis on transition elements of the periodic table. Current CCA-based cold spray coating systems showed better adhesion, cohesion, and mechanical properties than conventional one-principal element-based alloys. Comprehensive mechanical behavior, microstructural evolution, deformation, and cracking of cold spray CC-based coatings on the same and different substrates are reviewed. Techniques such as analytical models, finite element analysis, and molecular dynamic simulations are reviewed. The implications of the core effects (high configurational entropy and enthalpy of mixing, sluggish diffusion, severe lattice distortion, and cocktail behavior) and interfacial nanoscale oxides on the structural integrity of cold spray CCA-based coatings are discussed. The mechanisms of adiabatic heating, jetting, and mechanical interlocking, characteristics of cold spray, and areas for future research are highlighted.

Dry abrasive wear and solid particle erosion assessments of high entropy alloy coatings fabricated by cold spraying

Recent advances in advanced metallic alloys have enabled the development of high entropy alloys (HEAs) for extreme engineering environments. HEAs are characterized by their mixing of elements with equimolar concentrations or near to equimolar concentrations, which enables the formation of solid-solution structures due to inherent high configurational entropy. With the advancement of HEAs, the attractiveness of these alloys as cold-sprayed coatings for wear resistant surfaces has been increasing. In the present study, a low-pressure cold spraying technique was employed to fabricate two new mechanically alloyed AlCoCrFeMoW and AlCoCrFeMoV HEA coatings. The phase formations, microstructure evolutions, and average microhardness of the fabricated HEA coatings were systematically investigated, in order to assess their resistance to dry abrasive wear and solid-particle erosion. The results showed that the cold-sprayed HEA coatings exhibited refined microstructure and low porosity, with the presence of body-centered cubic (BCC1 and BCC2) structures and CrMo intermetallic phases. Microhardness results revealed that AlCoCrFeMoV HEA coatings achieved the highest average hardness of around 561±63HV, such that it was 35% and 52% higher than that of AlCoCrFeMoW and AlCoCrFeMo HEA coatings, respectively. Dry abrasive wear results showed lower wear rates were achieved for AlCoCrFeMoV HEA coatings (590×10−6mm3/Nm), followed by AlCoCrFeMoW (660×10−6mm3/Nm) and AlCoCrFeMo HEA coatings (720×10−6mm3/Nm). However, damage during solid particle erosion was found to be higher in case of AlCoCrFeMoV HEA coatings compared to the other two coatings, suggesting no apparent correlation with microhardness values. These results suggest that the existence of high weight fractions of solid-solution phases in conjunction with refined microstructure and low porosity resulted in improved resistance to abrasive loading for the AlCoCrFeMoV HEA coatings but undermine performance and resistance to solid particle erosion damage.

In-situ construction of all-scale hierarchical microstructure and thermoelectric properties of (Sr0.25Ca0.25Ba0.25La0.25)TiO3/Pb@Bi composite oxide ceramics

SrTiO3-based oxides have been investigated as a promising n-type thermoelectric material at high temperatures; however, the relatively high thermal conductivity results in inferior thermoelectric performance. The lattice thermal conductivity can be significantly reduced by high-entropy engineering via severe lattice distortion. However, high configuration entropy also causes the deterioration of carrier mobility and restrains electron transport resulting in low electrical conductivity. In this work, the low lattice thermal conductivity of 1.7 W/(m·K) at 1 073 K and significantly improved electrical conductivity of 112 S/cm from 60 S/cm can be achieved in n-type (Sr0.25Ca0.25Ba0.25La0.25)TiO3/Pb@Bi composites ceramics with core-shell grains of all-scale hierarchical microstructure. The effects of the complex microstructure of core-shell grains as well as the precipitated Pb@Bi particles on electrons and phonons transport properties were systematically explored. ZTmax of 0.18 was obtained for the SPS-1200, which was 1.5 times that of pure high-entropy (Ca0.2Sr0.2Ba0.2La0.2Pb0.2)TiO3 samples prepared by a solid-state method. This improvement in thermoelectric performance contributes to the addition of Bi2O3 into the high-entropy (Sr0.2Ca0.2Ba0.2Pb0.2La0.2)TiO3 matrix resulting in multiphase core-shell grain structure combined with well-dispersed nano-sized metal Pb@Bi precipitates in the matrix. This feasible strategy of in-situ constructing all-scale hierarchical nanostructures can also be applied to enhance the performance of other thermoelectric systems.

Mechanistic insights into the crystallization of coamorphous drug systems.

In our previous study, the coamorphous formulation of lurasidone hydrochloride (LH) with saccharin (SAC) showed significantly enhanced dissolution and physical stability compared to crystalline/amorphous LH. However, the coamorphous system is still in amorphous state, and has the tendency to recrystallization, which will in turn result in the loss of above advantages. In this study, the crystallization kinetics under isothermal and non-isothermal conditions was investigated. Compared to amorphous LH, coamorphous LH-SAC showed 68.3-361.2 and 2.6-6.1 times lower crystallization rates in glassy state and supercooled liquid state, respectively. After co-amorphization, the addition of SAC changed the crystallization mechanism of amorphous LH from nucleation-controlled to diffusion-controlled manner. Amorphous LH followed the site-saturated nucleation, whereas the coamorphous system exhibited a fixed number of nuclei. The non-isothermal crystallization indicated amorphous LH and coamorphous LH-SAC showed two-dimensional (JMAEK 2) and three-dimensional (JMAEK 3) growth of nuclei, respectively. Furthermore, coamorphous LH-SAC exhibited higher molecular mobility and dynamic fragility (mD) than amorphous LH, which is kinetically unfavorable for its physical stability. However, from thermodynamic perspective, coamorphous LH-SAC had a higher configurational entropy, i.e., a higher entropy barrier for crystallization, which is beneficial to hinder its crystallization. Therefore, it was concluded that the higher configurational entropy rather than the molecular mobility was proposed to be responsible for its improved stability. In addition, molecular dynamics simulations with miscibility, radial distribution function and binding energy calculations suggested coamorphous components exhibited good miscibility and strong intermolecular interactions, which was also conductive to the enhancement in its stability. This study offers an in-depth understanding about the effect of the coformer on the crystallization kinetics of coamorphous systems, and points out the important contribution of the configurational entropy in stabilizing the coamorphous systems.

Preparation of novel (MgCoNiCuZn)O high-entropy ceramic membrane and its dye separation

(MgCoNiCuZn)O high entropy ceramic (HEC) membrane was prepared successfully by phase inversion and calcination, and was used to remove Congo red. Raman spectra and XRD measurements showed complete transformation to single rock salt phase, and EDS exhibited uniform distribution of five metals. The hydrophilicity of HEC membrane became weak due to low free energy which was attributed to the high configuration entropy. The porosity of HEC membrane decreased and densification took place as the temperature enhanced, yielding the increase of bending strength. When the HEC membrane was calcined at 1040 ℃, the pure water flux and Congo red rejection reached 881.5 L/(m2·h) and 99.35%, respectively. The HEC membrane exhibited good long-term stability. When continuous filtration was performed for 10 h, the pure water flux ranged from 857.5 to 879 L/(m2·h), while Congo red rejection changed from 98.85% to 99.32%. The HEC membrane showed good chemical stability under weakly acidic and strong alkaline conditions.

Excellent mechanical properties of CoNiCr-based MP159 multicomponent alloys at ambient and cryogenic temperatures

The L12-strengthened high-entropy alloys (HEAs) exhibit excellent mechanical properties. The commercial CoNiCr-based MP159 superalloy with high configuration entropy up to that of HEAs is revisited. And the coherent L12 nano precipitates with different sizes and volume fractions are introduced into MP159 alloys by tuning the aging time. Especially at 298 K, the alloys after aging for 10 h can achieve a good combination of 1360 MPa high tensile strength and 41% tensile strain. In contrast, the tensile strength is as high as 1710 MPa, and the tensile strain remains at 45% at cryogenic temperatures, much better than most of HEAs with similar composition. Importantly, the optimal size of the precipitates is calculated to be 41 nm. The present work provides a basic guidance for developing nano-precipitated CoNiCr-based alloys with high mechanical performances.

Tensile behavior of hexagonal rare-earth-based low, medium, and high entropy alloys: Strengthening effect of configurational entropy

In the equiatomic hexagonal close packed high entropy alloy Ho-Dy-Y-Gd-Tb, there is a discrepancy, called the Gibbs paradox, between the extraordinary similarity of the constituent rare earth elements and its calculated configurational entropy. Equiatomic alloys made from one to five rare earth elements, with varying configurational entropy, are investigated for this work to evaluate this paradox in the context of tensile behavior. Assuming comparable microstructures and minimized solid solution strengthening due to the similarity of the constituent elements, a possible strengthening effect of the high configurational entropy is assessed. The alloys are successfully prepared via arc melting with comparable grain sizes and near equiatomic compositions. X-Ray diffraction, and elemental mappings with energy-dispersive X-Ray spectroscopy indicate single-phase microstructures in all alloys except for Ho–Y and Ho-Y-Gd. Tensile tests at room temperature show that the tensile strength of the single-phase alloys lies in the range of the pure elements, which confirms the hypothesis of minimized solid solution strengthening. Those alloys containing additional phases as well as the high entropy alloy show pronounced brittle behavior. No direct correlation between tensile behavior at room temperature and configurational entropy is observed. We state that this alloy system is a suitable candidate for evaluating the Gibbs paradox and disproving an entropy effect on the tensile behavior of this alloy system. This work contributes to understanding mechanical properties and the influence of configurational entropy on the hexagonal close packed high entropy alloy Ho-Dy-Y-Gd-Tb.

Entropy-Stabilized Multicomponent Porous Spinel Nanowires of NiFeXO4 (X = Fe, Ni, Al, Mo, Co, Cr) for Efficient and Durable Electrocatalytic Oxygen Evolution Reaction in Alkaline Medium.

Cost-effective electrochemical water splitting technology hinges on the development of efficient and durable catalysts for oxygen evolution reaction (OER). Spinel oxides (formula: AxB3-xO4) are structurally stable for real applications. Much effort has been devoted to improving the catalytic activity. Here, we report a eutectic dealloying strategy to activate the porous spinel NiFe2O4 nanowires with up to four metal cation substitutions. As-obtained spinel NiFeXO4 (X = Fe, Ni, Al, Mo, Co, Cr) delivers a benchmark current density of 10 mA·cm-2 at an overpotential of only 195 mV, outperforming most spinel phase OER electrocatalysts and comparable to the state-of-the-art NiFe hydroxides. It is stable for over 115 h of electrolysis. Aberration-corrected transmission electron microscopy, high-resolution electron energy loss spectroscopy, and atomic-scale strain mappings reveal that the multivalent cation substitutions result in substantial lattice distortion and significant electronic coupling of metal 3d and O 2p orbitals for increased covalency. Further theoretical calculations suggest that the NiFeXO4 are stabilized by the high configurational entropy, and their synergy favors the absorption of H2O molecules and lowers the adsorption energy barrier of the OOH* intermediate. The improved intrinsic activity together with the highly nanoporous structures contribute to the appealing apparent catalytic performances. The work demonstrates an effective approach for the synthesis of stable multicomponent spinel oxides and highlights the effectiveness of the multication substitution strategy for producing highly durable and active spinel catalysts, which meet multiplexed structure and superior property requirements in practical applications.

Structures and room-temperature magnetic properties of entropy-modulated Gd&lt;sub&gt;2&lt;/sub&gt;Co&lt;sub&gt;17&lt;/sub&gt; based intermetallic compounds

&lt;sec&gt;The entropy-modulated material has been a hot topic due to its unique design concept and excellent properties. However, previous studies of entropy-modulated materials mainly focused on the alloys with simple face-centered cubic, or body-centered cubic, or hexagonal close-packed structures. In this work, the design concept of entropy-modulation is introduced into Gd&lt;sub&gt;2&lt;/sub&gt;Co&lt;sub&gt;17&lt;/sub&gt; based intermetallic compound, and the effect of high configuration entropy on the structural stabilization and room-temperature magnetic properties of Gd&lt;sub&gt;2&lt;/sub&gt;Co&lt;sub&gt;17&lt;/sub&gt; based intermetallic compound are studied systematically.&lt;/sec&gt;&lt;sec&gt;The samples are prepared by vacuum Arc melting technology in an ultrahigh-purity Ar atmosphere and followed by annealing at 1000 ℃ for 8 days and finally by quenching in cool water. The fine powders are prepared by grinding the ingots in an agate mortar. The powder XRD and SEM-EDS are used to check the crystal structures and chemical compositions. To study the magnetic properties, the column-like samples are prepared by mixing the fine powder and epoxy with a weight ratio of 1∶1, and then aligned under an applied field of 1 T at room temperature.&lt;/sec&gt;&lt;sec&gt;The high configuration entropy is found to play an important role in the structural stabilization and magnetic properties of Gd&lt;sub&gt;2&lt;/sub&gt;Co&lt;sub&gt;17&lt;/sub&gt; based medium- and high-entropy intermetallic compounds. The XRD patterns and Rietveld structural refinement results confirm that all the samples are single-phase. The structure depends on the effective atomic radius &lt;i&gt;R&lt;/i&gt;&lt;sub&gt;&lt;i&gt;A&lt;/i&gt;&lt;/sub&gt;, the structure of entropized Gd&lt;sub&gt;2&lt;/sub&gt;Co&lt;sub&gt;17&lt;/sub&gt; based intermetallics can be stabilized into rhombohedral Th&lt;sub&gt;2&lt;/sub&gt;Zn&lt;sub&gt;17&lt;/sub&gt;-type with &lt;i&gt;R&lt;/i&gt;&lt;sub&gt;A &lt;/sub&gt;&gt; 1.416 or hexagonal Th&lt;sub&gt;2&lt;/sub&gt;Ni&lt;sub&gt;17&lt;/sub&gt;-type with &lt;i&gt;R&lt;/i&gt;&lt;sub&gt;A&lt;i&gt; &lt;/i&gt;&lt;/sub&gt;&lt; 1.4105. According to thermodynamic calculations of entropized Gd&lt;sub&gt;2&lt;/sub&gt;Co&lt;sub&gt;17&lt;/sub&gt; intermeatllics, the atomic radius difference Δ&lt;i&gt;r&lt;/i&gt; ranges from 0.55% to 1.81%, and the mixing enthalpy &lt;inline-formula&gt;&lt;tex-math id="M3"&gt;\begin{document}$ \Delta {{\boldsymbol{H}}}_{{\rm{m}}{\rm{i}}{\rm{x}}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20221995_M3.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20221995_M3.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; is corresponding to 0 for the rare earth site, –4 to –1 kJ/mol for the transition metal site, and –8.54 to –5.13 kJ/mol between rare earth and transition metal sites. It is suggested that all the thermodynamic parameters meet the criteria for the formation of single-phase medium- and high-entropy intermetallic compounds. The configuration entropy changes from 0.69R to 1.39R. The room temperature magnetic properties are significantly improved by the modulation of entropized design at rare earth and transition metal sublattices. The entropization enhances the saturation moments of all samples, which can be explained with a modified magnetic valence model. The value of &lt;inline-formula&gt;&lt;tex-math id="M4"&gt;\begin{document}${N}_{{\rm{sp}}}^{\uparrow }$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20221995_M4.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20221995_M4.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; (the number of the electrons in the unpolarized sp conduction bands) increases from 0.3 to 0.4 after entropization, the indirect interaction between rare earth and transition metal sublattice is increased, the spin moment of s conducting electron as a medium of two sublattices is enhanced, and the magnetic moment is increased. The entropization also induces magnetic anisotropy to transform from basal plane to easy axis for the entropized design at transition metal sublattice and the coercivity of rare earth to increase.&lt;/sec&gt;

Effect of configurational entropy on phase formation, structure, and magnetic properties of deeply substituted strontium hexaferrites

Solid solutions based on SrFe 12 O 19 strontium hexaferrite with deep (up to at.67%) co-substitution of triply charged Fe 3+ iron cations by triply charged diamagnetic Al 3+ aluminum, Ga 3+ gallium, and In 3+ indium cations, as well as by paramagnetic Co 3+ cobalt and Cr 3+ chromium cations, were obtained by conventional ceramic technology. This type of substitution leads to the formation of high-entropy phases. The phase composition of the obtained samples was studied by powder X-ray diffraction. The configurational mixing entropy was calculated for all the obtained samples, and its influence on the processes of phase formation was studied. The unit cell parameters are calculated and their dependences on the 〈r B 〉 average ionic radius of the iron sub-lattice are plotted. The average grain size varied within 2–5 μm. The field and temperature properties of the magnetization of the obtained samples were studied. The M s saturation magnetization is determined using the Law of Approach to Saturation. The M r residual magnetization, SQR loop squareness and H c coercivity are also determined. Based on the obtained data, the k magnetic crystallographic anisotropy coefficient and the H a anisotropy field are calculated. All the obtained and calculated values are plotted depending on the 〈r B 〉 average ionic radius of the iron sub-lattice. All plotted dependencies are non-linear. The T mo magnetic ordering and T f freezing temperatures are obtained from the ZFC and FC magnetization data. The cluster nature of the magnetic behavior for all the samples is revealed. The average cluster diameter reaches ∼ 400 nm. The interpretation of the magnetic properties is made taking into account the effect of high configurational mixing entropy and magnetic dilution of the iron sub-lattice.

Influence of high configuration entropy on damping behaviors of Ti-Zr-Hf-Ni-Co-Cu high entropy alloys

TiNi-based shape memory alloys (SMAs) have been used as damping materials to eliminate noise and mechanical vibration. However, their application is limited by low working temperatures and damping capacity. In this work, two novel Ti-Zr-Hf-Ni-Co-Cu high entropy shape memory alloys (HESMAs) with different transformation temperatures and damping properties were investigated. The results show that Ti25Zr8Hf17Ni30Co5Cu15 has superior damping performance arising from martensitic transformation, shape memory effect (thermal cycle at constant load) as well as superelasticity. Compared to traditional TiNi-based SMAs, the as-cast HESMAs exhibit a much higher ultrahigh yield strength (∼2 GPa) and storage modulus (∼50 GPa). The high configuration entropy of the HESMAs with high uneven internal stress and severe lattice distortion is revealed as the underlying mechanisms governing distinctive damping performance. The effects of high configuration entropy and microheterogeneity on the martensitic transformation behavior and damping performance of HESMAs are clarified in this work, which provides a basis for designing alloys with superior damping properties.

High-entropy alloy nitride nanofilms via a co-sputtering method enable superior optical performance and thermal robustness

• HEN (ZrNbMo-Al-N) films are prepared through a reactive magnetron co-sputtering method. • A tri-layer SSA is fabricated based on HEN (ZrNbMo-Al-N) films. • The absorbers on Cu substrates show high absorptance (96.2%) and low emittance (6.6%). • The absorbers on SS Substrates exhibit superior thermal robustness at 400 °C. High-entropy ceramics are a new class of solar-thermal material with high configurational entropy, lattice distortion, and flexible component space. In this work, we report a tri-layer solar selective absorber based on high-entropy nitride (ZrNbMo-Al-N), which can be deposited on various substrates through reactive magnetron co-sputtering. The absorbers on Cu substrates exhibit a remarkable solar absorptivity of 96.2% and a suppressed thermal emissivity of 6.6%. Moreover, the absorbers on stainless steel (SS) substrates show superior thermal robustness. After annealing at 400 °C for 168 h in a vacuum condition, they retain a high absorptivity of 94.4% and a low thermal emissivity of 9.8%.

Efficient solar energy harvesting enabled by high-entropy ceramic nanofilms through a co-sputtering method

Recent advances in high-entropy ceramic nanofilms have unlocked new possibilities for preparing high-performance solar-thermal conversion materials. Due to their species diversity and structure distinctiveness, these materials provide huge room to exploit more appropriate compositions for boosting solar-thermal performance. Herein, we report a spectrally selective absorber based on high-entropy ZrNbMo-Cr-N ceramic nanofilm prepared by magnetron co-sputtering. Enabled by interface interference and intrinsic absorption effects, the as-deposited absorber exhibits a high solar absorptance of 96.3%, suppressed thermal emittance of 18.8%@400 ºС, and solar-thermal conversion efficiency of 85.4% under 400 ºС and 100 suns. Besides, due to the high configuration entropy of the absorption layers, the absorber exhibits superior thermal robustness after annealing at 400 ºС for 7 days. Further, the absorber can be well deposited on various substrates, including flexible cotton. Radiated by simulated sunlight, those absorber shows a good temperature response; in particular, the surface temperature of the absorber on cotton readily increases to 80 ºС with 50 s under 1 sun. Featured with those competitive merits, the high-entropy ceramic nanofilm absorber empowers a distinct paradigm to investigate solar-thermal conversion, rendering it attractive for various solar-thermal applications.