High Entropy Amorphous Alloys Research Articles

Engineering Topological and Chemical Disorder in Pd Sites for Record-Breaking Formic Acid Electrocatalytic Oxidation.

Designing palladium-based formic acid oxidation reaction (FAOR) catalysts to achieve significant breakthroughs in catalytic activity, pathway selectivity, and toxicity resistance is both urgent and challenging. Here, these challenges are addressed by pioneering a novel catalyst design that incorporates both topological and chemical disorder, developing a new class of PdCuLaYMnW high-entropy amorphous alloys with a porous network (Net-Pd-HEAA) as a highly active, selective, and stable FAOR electrocatalyst. This novel Net-Pd-HEAA demonstrates record-breaking FAOR performance, achieving the mass and specific activities of 5.94 A mgPd -1 and 8.94mA cm-2, respectively, surpassing all previously reported Pd-based catalysts and showing strong competitiveness against advanced Pt-based catalysts. Simulataneously, Net-Pd-HEAA exhibits extraordinary stability in accelerated durability tests (ADT) and chronoamperometry (CA) tests. Advanced characterization and in situ, spectral analysis reveal that the extremely disordered atomic structure effectively regulates the geometric and electronic structure of the Pd sites, enhancing active intermediate coverage, facilitating dehydrogenation pathway, and inhibiting the production/adsorption of CO. Furthermore, when employed as the anode catalyst in proton exchange membrane water electrolysis (PEMWE), Net-Pd-HEAA only requires a potential of 1.28V to obtain a current density of 1 A cm-2, and operates stably in a highly corrosive electrolyte for over 100 h.

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.

An assessment of the mechanically alloyed equiatomic FeCoNiMnSi high entropy amorphous alloy for non-isothermal crystallization kinetics and magnetocaloric refrigeration application

We studied an equiatomic FeCoNiMnSi high entropy amorphous alloy successfully processed via mechanical alloying technique. The structural, magnetic, and magnetocaloric characteristics of the resulting materials were examined using X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and a vibrating sample magnetometer. The structural analysis showed a prominent amorphous phase formation as the milling time increases from t = 0–35h of mechanical alloying. The differential scanning calorimetry was employed to investigate the non-isothermal crystallization kinetics of the 35-h milled sample. The results revealed that the milled powder consists of a single exothermic peak with its apparent activation energy (Eg, Ex, Ep) being determined using the Kissinger, Ozawa, and Augis-Bennett equations. The findings exhibit Ex > Ep > Eg, representing that nucleation is more complicated than the growth mechanism during the crystallization process. Meanwhile, under non-isothermal conditions, the Kissinger-Akahira-Sunose, Friedman, and Flynn-Wall-Ozawa models were calculated using the local activation energies that agree with the apparent activation energy. Furthermore, the Johson-Mehl-Avrami-Kolmogorov exponent (n) and Avrami-Ozawa combined [F(T)] models exhibit high-dimensional nucleation and growth with an increasing nucleation rate enabled by lowering the local activation energies as a function of degree of conversion with respect to temperature. In magnetic measurements, a feasible mathematical model was proposed as a novel strategy for predicting the value of saturation magnetization as a milling time function. The model has an exceptional predictive capability, confirmed by fitting other research outcomes. Finally, the proposed system also delivers the best magnetocaloric properties with a maximum magnetic entropy change of 3.70 Jkg−1 K−1 at 150 K curie temperature and a refrigeration capacity of 252.86 J/kg with 1000 Oe applied magnetic field.

Cryogenic temperature magnetocaloric effect and critical behavior of GdDyErAlM (M=Fe, Co, Ni) high entropy amorphous alloys

High entropy amorphous alloys (HE AMs) have attracted extensive interest lately due to their superior magnetocaloric properties. However, the critical behavior and mechanical properties have received less research, which restricts their applications. This work presented a comprehensive investigation of the magnetocaloric effect (MCE), critical behavior, and mechanical performance of quinary Gd20Dy20Er20Al20M20 (M = Fe, Co, Ni) HE AMs. All samples exhibited distinct spin glass-like behavior below TC and competitive MCE around hydrogen liquefaction temperature range. Excellent MCE was achieved by the HE AMs through a second-order phase transition from paramagnetic state to ferromagnetic state at 79 K for Fe, 41 K for Co, and 36 K for Ni. Among them, the maximum magnetic entropy change (-ΔSM)max of Gd20Dy20Er20Al20Co20 amorphous alloys was 9.59 J kg−1 K−1 under 0–5 T. Furthermore, RC and RCP of Gd20Dy20Er20Al20Fe20 amorphous alloys were respectively 519 J kg−1 and 613 J kg−1, larger than that of most RE-based amorphous alloys. For all samples, the critical behavior of the phase transition approached the mean field model, and this responded to the long-range ordering of the magnetic interaction. The bending plasticity of Gd20Dy20Er20Al20M20 (M = Fe, Co, Ni) HE AMs were 0.78, 1.03, 0.89, respectively. The adjustable Tc, large (-ΔSM), high RCP, and outstanding mechanical properties suggested Gd20Dy20Er20Al20M20 (M = Fe, Co, Ni) HE AMs may find utility as magnetic refrigerants in low-temperature applications.

Microstructural stability and mechanical property of AlCrFeMoTi high-entropy amorphous alloy thin films under He+ ions irradiation

High-entropy amorphous materials have recently proved exceptional radiation resistance, showing potential as a candidate materials for nuclear industry applications. This study synthesized nearly equi-atomic AlCrFeMoTi high-entropy amorphous thin films with a thickness of about 499 nm using magnetron sputtering. The prepared films were subjected to low dose, 0.5 MeV He+ ion irradiation, with varying irradiation damage ranging from 0.01 to 0.1 displacement per atom (dpa). Increasing the irradiation dose led to a decrease in the radius of the inner diffraction halo (r) and an increase in the crystal-like order, indicating an irradiation-induced structural relaxation process within the amorphous matrix. This relaxation results in more efficient atomic packing, yielding a denser amorphous structure and enhanced hardness of AlCrFeMoTi high-entropy amorphous thin films. This study demonstrates that AlCrFeMoTi high-entropy amorphous thin films exhibit remarkable radiation resistance, with stable microstructure and mechanical properties under He+ irradiation, making them promising candidates for applications in the nuclear industry.

Novel nanoporous amorphous/nanocrystalline composite structured RuNiFeCo multicomponent alloys with exceptional catalytic activity for ammonia borane hydrolytic dehydrogenation

The pursuit of high-efficient and cost-effective catalysts for hydrogen generation is imperative to address the energy crisis. Herein, nanoporous RuNiFeCo alloys (np-RuNiFeCo) with high catalytic activity for ammonia borane (AB) hydrolytic dehydrogenation have been prepared by dealloying Fe25NixCo40-xRu5B30 (x = 0–40) high-entropy amorphous alloys with low Ru content. The np-RuNiFeCo are composed of an amorphous/hexagonal close-packed Ru nanocrystalline dual-phase structure and exhibit a uniform nanopore/ligament bicontinuous architecture. The morphology, composition, and AB hydrolysis catalytic properties of the np-RuNiFeCo can be regulated by varying the Ni/Co content in the precursors, and the best catalytic activity with a high turnover frequency value of 148.2 molH2molRu‐1min‐1 and a low apparent activation energy of 25.3 kJmol‐1 was obtained when x = 30. Density functional theory simulations indicate that the presence of Ni, synergizing with Fe and Co, promotes electron transfer to Ru and enhances the adsorption energies of both AB and H2O molecules while reducing the activation barrier for cleaving the H2O molecule, leading to enhanced intrinsic catalytic activity of the alloy. The exceptional catalytic performance of the np-RuNiFeCo arises from the synergy of multiple principal elements, nanoporous morphology, and amorphous/nanocrystalline heterogeneous interface. In addition, the mechanisms of dealloying and nanoporous structure formation have been discussed based on surface diffusion.

Influence of metalloid element B on the microstructure and performances of novel FeCoNiVB high-entropy amorphous alloys

The influence of metalloid element B content on the microstructure, microhardness, thermal stability and anti-corrosion properties of (Fe1/4Co1/4Ni1/4V1/4)100-xBx (x = 16 ∼ 32 at.%) high-entropy amorphous alloys was studied systematacially. Results showed that the investigated alloy ribbons owned fully glassy nature. The average microhardness and crystallization onset temperature of these glassy ribbons were over 958 HV0.2 and 757 K, respectively. The self-corrosion potentials of samples were −0.541 ∼ −0.484 V and the most positive potential could reach −0.484 V for the Fe20Co20Ni20V20B20 alloy ribbons. Besides, this equiatomic specimen also owned the smallest corrosion current density of 5.87 × 10−6 A/cm2 and the largest polarization resistance of 9635.7 Ω·cm2. The experimental characterization analysis of alloy ribbons’ immersion tests further proved the credibility of measurement results. Therefore, it is indicated that the equiatomic FeCoNiVB high-entropy amorphous alloy possesses the best corrosion resistance in 3.5 wt% NaCl solution among studied samples and this alloy can be also viewed as a potential functional protective material combined with the anti-corrosion performance, wear resistance and thermal stability.

Composition Design Strategy for High Entropy Amorphous Alloys.

High entropy amorphous alloys (HEAAs) are materials that have received much attention in recent years. They exhibit many unique properties; however, research on their composition design method has not been deep enough. In this paper, we summarized some effective composition design strategies for HEAAs. By adjusting the atomic ratio from quinary bulk metallic glasses, Ti20Zr20Cu20Ni20Be20 HEAA with a high fracture strength of 2315 MPa was designed. By similar element addition/substitution, a series of Ti-(Zr, Hf, Nb)-Cu-Ni-Be HEAAs was developed. They possess good glass-forming ability with a maximum critical diameter of 30 mm. Combining elements from those ternary/quaternary bulk metallic glasses has also proved to be an effective method for designing new HEAAs. The effect of high entropy on the property of the alloy, possible composition design methods, and potential applications were also discussed. This paper may provide helpful inspiration for future development of HEAAs.

Plasma sprayed CoNiCrMoNb(BSi) high-entropy amorphous alloy coating: The effect of spraying power on microstructure, mechanical and tribological properties

Plasma spraying was used to fabricate the CoNiCrMoNb(BSi) high-entropy amorphous alloy (HEAA) coatings. The microstructure, mechanical, and tribological properties of these coatings were studied as a function of spraying power. The results show that the as-sprayed coating was composed of an amorphous phase and a minor FCC phase. An increased amorphous content was obtained at an increased spraying power, leading to improvements in hardness and wear resistance. However, the porosity in the coatings got worsen when the power levels were insufficient or excessive, which deteriorated the mechanical and tribological properties of these coatings. The spraying power was optimized to 45 kW to provide a higher amorphous content and reduced porosity, resulting in improved hardness and increased wear resistance. This study has clarified the techniques used to tailor the microstructure in the plasma spraying process, as well as the fundamental principles for enhancing the mechanical and tribological properties. These findings hold considerable importance for the practical applications of HEAA coatings in engineering. In summary, the results suggested that the manipulation of spraying power was crucial in achieving a substantial amorphous phase and preventing the occurrence of porosity in plasma-sprayed HEAA coatings.

Effect of Mn content on crystallization behaviors and magnetic properties of FeCoNiBMn high-entropy amorphous alloys

FeCoNi-based high-entropy alloys (HEAAs) attracted much attention because of their good thermodynamic stability, mechanical properties and soft magnetic properties. In this paper, Fe22Co22Ni22B34-xMnx (x = 6–22 at%) HEAAs were designed and the effects of Mn on the crystallization behaviors, magnetic performance, and mechanical property were investigated. The crystallization behaviors of the FeCoNiBMn HEAAs are: 1) 12–16 at% Mn: am → am’ + M23B6 → M23B6 + fcc; 2) 18 at% Mn: am → am’ + bcc + M23B6 → bcc + M23B6 → fcc + M23B6; and 3) 20–22 at% Mn: am → am’ + bcc → bcc + M23B6 → fcc + M23B6. Two parameters ΩA and VEC are proposed to predict the primary precipitates of FeCoNi-based HEAAs. All as-spun ribbons exhibit excellent soft magnetic properties with a very low coercivity (Hc) of less than 1.5 A/m and a maximum saturation magnetization (Bs) of 0.82 T. The 14 at% Mn alloy exhibits very low Hc of less than 4 A/m even after complete crystallization. Magnetic properties and Vickers hardness of crystalline ribbons are closely related to crystallization behaviors.

Room temperature nanoindentation creep behavior of CoNiCrMo-based high entropy amorphous alloy coatings prepared by HVAF

The present study aimed to explore the creep behavior of CoNiCrMo-based high entropy amorphous alloy coatings at room temperature using nanoindentation creep experiments. The coatings were subjected to different loading rates to assess their performance. The findings indicate that the high entropy effect of the (Co0.33Ni0.33Cr0.23Mo0.1)80-xNbx(B0.7Si0.3)20 (x = 0, 2 and 4 at. %) high entropy amorphous alloy coatings has a notable impact on the creep resistance and facilitates a uniform plastic deformation during creep. The shear transition zone (STZ) size and the free volume content during creep deformation exhibit an increase in response to the concentration of Nb. This phenomenon can be attributed to the elevated atomic packing density and the hindered movement of atoms resulting from the incorporation of Nb. Nb content has a favorable impact on the creep stress index, increasing creep stress. Also, the high concentration of Nb is found to mitigate the propensity of the stress exponent to drop with increasing loading rates. The high entropy effect of the as-sprayed coatings promotes high creep resistance and homogenous creep deformation.

Influence of Si and Mn on the Phase Formation, Crystallization Kinetics, and Enhanced Magnetic Properties of Mechanically Alloyed NiCoFe(SiMn)x High Entropy Amorphous Alloys

Influence of Si and Mn on the Phase Formation, Crystallization Kinetics, and Enhanced Magnetic Properties of Mechanically Alloyed NiCoFe(SiMn)x High Entropy Amorphous Alloys

Microstructure, Non-isothermal Crystallization Kinetics and Magnetic Behaviour Study of [FeCoNi100-x(SiMn)x] High Entropy Amorphous Alloys Synthesized by Mechanical Alloying

Microstructure, Non-isothermal Crystallization Kinetics and Magnetic Behaviour Study of [FeCoNi100-x(SiMn)x] High Entropy Amorphous Alloys Synthesized by Mechanical Alloying

Microstructure, mechanical properties and tribological behaviors of (Co0.33Ni0.33Cr0.23Mo0.1)80−xNbx(B0.3Si0.7)20 high entropy amorphous alloy coatings

The (Co0.33Ni0.33Cr0.23Mo0.1)80−xNbx(B0.3Si0.7)20 high entropy amorphous alloy coatings (denoted as Nbx, x = 0, 2 and 4 at%) are successfully prepared by HVAF thermal spraying. The microstructure, mechanical properties and tribological behaviors of the as-sprayed coatings were comparatively investigated. The microstructure of as-sprayed coatings consists of amorphous phases, face-centered cubic (FCC) and (Cr, Mo)xB phases. Notably, the GFA (Glass-forming ability) of the as-sprayed coatings is improved and the precipitation of (Cr, Mo)xB phases is limited with the addition of Nb. The face-centered cubic (FCC) and (Cr, Mo)xB phases decrease with the Nb content increasing, and the Nb4 coating almost has a full amorphous structure. The Vickers hardness improves from 568.2 HV of Nb0 coating to 707.9 HV of Nb4 coating. The nanoindentation results indicate that the addition of Nb enhances the plastic deformation resistance and uniform deformation capacity of the coatings. For the as-sprayed coatings, the evolutions of tribological behaviors are consistent with the structural and mechanical variations. The addition of Nb decreases the oxidation wear and adhesion wear during friction process, which are the main wear failure mechanisms of as-sprayed coatings. The wear resistances of Nb4 coatings is increased by 49.54 % compared with that of the Nb0 coating, and the friction running-in time is decreased by 18.26 %.

Thermal stability and corrosion behavior of a novel Zr22.5Ti22.5Hf22.5Ni22.5Ta10 high-entropy amorphous alloy

The present study reasonably designed and prepared a novel Zr22.5Ti22.5Hf22.5Ni22.5Ta10 high-entropy amorphous alloy with excellent thermal stability and corrosion resistance. The hysteresis diffusion effect caused by the high mixing entropy of the multi-principal system affects the formation of the crystalline phase and thus improves thermal stability. The alloy exhibits excellent corrosion resistance compared to 316 L in 3.5 wt% NaCl solution. The XPS results indicate that the passive film of Zr22.5Ti22.5Hf22.5Ni22.5Ta10 passive film is rich in oxides of Zr, Ti, Hf, and Ta, which has excellent resistance to chloride ion attack.

Effect of Si and B on the Electrochemical Behavior of FeCoNiCr-Based High-Entropy Amorphous Alloys

The ability to produce high-entropy alloys with an amorphous structure, so-called high-entropy metallic glasses (HEMGs), offers the possibility to produce new compositions with good mechanical properties and resistance to corrosion. In this study, corrosion behavior was studied in two HEMGs, FeCoNiCrB and FeCoNiCr(BSi). In both cases, the total amount of metalloid atoms was kept constant at 20 at.%. The electrochemical behavior of these alloys was studied by means of linear polarization resistance (LPR) measurements and electrochemical impedance spectroscopy in a 3 wt.% NaCl solution. The effect of corrosion was characterized by using X-ray photoelectron spectroscopy (XPS) and the surface morphology was checked using a scanning electron microscope (SEM). The results show that samples with B but without Si exhibit better corrosion resistance due to its chemical homogeneity and lack of structural heterogeneity.

High-Temperature Rheological Behavior and Composition Design of Hf-Be-Ti-Zr-Cu-Ni High-Entropy Amorphous Alloy

High-Temperature Rheological Behavior and Composition Design of Hf-Be-Ti-Zr-Cu-Ni High-Entropy Amorphous Alloy

In-situ construction and repair of high catalytic activity interface on corrosion-resistant high-entropy amorphous alloy electrode for hydrogen production in high-temperature dilute sulfuric acid electrolysis

Producing high-purity hydrogen from water electrolysis using intermittent renewable electricity is fascinating and challenging. Noble metal-based high-entropy alloy with near-equimolar mixed elements have unique properties including cocktail effect, high entropy effect and lattice distortion effect, which are beneficial to improve catalytic performance and reduce the amount of noble metal. Taking advantages of excellent mechanical properties, high thermal stability and corrosion resistance, as well as chemical uniformity and tunability, equiatomic high-entropy metallic glass PdPtCuNiP was employed to construct nanosponge-like architecture with uniform nanopores via a precise strategy of potentiostatic electrochemical dealloying, which presented superior hydrogen evolution reaction (HER) electrocatalytic performance in hot dilute H2SO4. The Tafel slope is 34.2 mV dec−1 and the overpotential corresponding to 10 mA cm−2 is 35.4 mV, outperforming commercial Pt/C catalyst and most currently available electrocatalysts. Furthermore, even electrocatalytic performance of nanoporous PdPtCuNiP is degraded tinily by hot dilute H2SO4 accordng to power-off or low-voltage operation of water-electrolysis system, it can be directly refreshed by in-situ potentiostatic polarization in the electrolyzer. We believe the strategy of in-situ construction and repair of nanostructured electrocatalytic surface on high-entropy alloy in this study will call for more endeavors to realize the practicality of hydrogen production in harsh acidic electrolyte.

Vacuum brazing of YSZ ceramic and TC4 alloy with a Ti20Zr20Hf20Cu20Ni20 high entropy amorphous alloy

The joint embrittlement induced by bulky intermetallic compounds (IMCs) formed during brazing greatly impairs the bonding strength of Yttria-stabilized zirconia (YSZ) ceramic and Ti6Al4V (TC4) alloy. To inhibit the growth of IMCs and prevent the formation of bulky phases, in this work, a Ti20Zr20Hf20Cu20Ni20 high-entropy amorphous alloy was innovatively used for brazing YSZ- TC4. The microstructure and mechanical properties of the joint brazed at different temperatures were studied in detail. The results show that the joint is mainly composed of the α-Ti solid solution phase and eutectoid microstructure which composites of α-Ti matrix and fine acicular (Ti, Zr, Hf)2(Cu, Ni) second phase. Through thermodynamic calculation, it was determined that the synergistic interaction of multi-principal elements significantly increased the mixing entropy of the joint and hence facilitated the formation of solid solution phases, inhibiting the formation of bulky IMCs. The maximum shear strength of the joint can be reached 240.5 MPa with the brazing parameters of 960 °C and 10 min, which was much higher than most of the commonly used Ag–Cu or Ti-based filler metal. This research proves that using high entropy amorphous alloy as filler metal is a promising method to reduce the formation of intermetallic compounds in the interfacial microstructure of brazed joints.

FeCoNiMnCuTi high entropy amorphous alloys and M50Ti50 (M = Fe, Cu, FeCoNiMnCu) amorphous alloys: Novel and efficient catalysts for heterogeneous photo-Fenton decomposition of Rhodamine B

Traditional Fe based amorphous alloys (Fe-Si-B system) with good Fenton-like performance have attracted great attention in dye wastewater decomposition. However, their relative low catalytic stability, narrow pH working range and expensive constituent elements impede the corresponding application. In addition, discovering new application of high entropy alloys in catalytic degradation besides decolorization of azo dyes has already been a scientific research hotspot. Consequently, in this work, M50Ti50 (M = Fe, Ni, Cu, FeCoNiMnCu) amorphous alloys, FeCoNiMn high entropy alloys and FeCoNiMnCuTi high entropy amorphous alloys were prepared by one-step ball milling method and then used as Fenton-like catalysts. The average particle sizes of the prepared Fe50Ti50, Ni50Ti50, Cu50Ti50, (FeCoNiMnCu)50Ti50, FeCoNiMn and FeCoNiMnCuTi were measured to be 22.3, 27.8, 26.5, 17.1, 15.4 and 19.5 μm, respectively. Among them, Fe50Ti50, Cu50Ti50, (FeCoNiMnCu)50Ti50 and FeCoNiMnCuTi exhibited superior photo-Fenton performances: 4 min UV decomposition rates of RhB solution are up to 82.77%, 85.96%, 75.23% and 88.19%, respectively, which would be the promising Fenton-like catalysts for industrial dye wastewater treatment. In particular, this is the first report on dye degradation behavior of equiatomic high entropy amorphous alloys and Cu based amorphous alloys were firstly developed to be a photo-Fenton catalyst.