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Oxidation resistance is critical for high-entropy diborides (HEBs) to be used as thermal structural components under oxygen-containing high-temperature environments. Here, we successfully realize the exploitation of (Zr, Ta, Cr, W) B2HEBs with superior oxidation resistance by comprehensively screening their compositions. To be specific, 21 kinds of HEB-xTM (x= 0–25 mol%, TM = Zr, Ta, Cr, and W) samples are fabricated via an ultrafast high-temperature sintering technique. The as-fabricated HEB-5Cr samples show the best oxidation resistance at 1673 K among all the samples. Subsquent oxidation investigations further confirm the as-fabricated HEB-5Cr samples possess superior oxidation resistance with the parabolic oxidation behavior across 1473–1773 K. Such superior oxidation resistance is believed to result from the multi-component synergistic effects. Particularly, the Ta5+and W4+cations with high ionic field strengths can promote the formation of 4B–O–4B linkages between [BO4] tetrahedrons by charge balance, which can stabilize the three-dimensional skeletal structure of B2O3glass and consequently result in an improved viscosity of the B2O3glassy layer. In addition, the ZrO2and Cr2O3with high melting points can dissolve into the B2O3glass to increase its glass transition temperature, leading to an enhanced viscosity of the B2O3glassy layer.

Establishing an efficient and robust data-driven approach to predict the phase formation of high-entropy ceramics (HECs) is essential to accelerate the discovery of novel HECs. In a recent issue of Nature, Divilov and coworkers have developed a disordered enthalpy-entropy descriptor to rapidly quantify the synthesizability of HECs, which provides a feasible solution to accelerate the experimental discovery of synthesizable HECs at scale.

The unique combination of a series of thermal properties and water-oxygen corrosion resistance is crucial for high-entropy disilicates serving as environmental barrier coating materials. Here, we report a novel (Gd1/7Dy1/7Ho1/7Er1/7Tm1/7Yb1/7Lu1/7)2Si2O7high-entropy disilicate (7HERED) that simultaneously possesses excellent match of coefficient of thermal expansion with SiCf/SiC composites across 473–1973 K, ultralow thermal conductivity (1.5 Wm−1K−1at 1273 K), superior high-temperature stability up to 1973 K, and water-oxygen corrosion resistance at 1673 K. Such superior properties are attributed to the high-entropy and lattice-distortion effects. Our 7HERED shows great potential as a next-generation environmental barrier coating material.

A unique optimized of core–shell structural B4C nanopowder, sintering aid additive of Si, and high-pressure sintering technique has been used to process nanocrystalline B4C–SiC ceramics with enhanced mechanical properties. C-coated B4C nanopowder was initially uniformly mixed with micron Si of different content by ball-milling. B4C–SiC composites with a homogenous distribution of SiC in B4C matrix were subsequently obtained by sintering the mixed powders at 6 GPa and 1600 °C. The added Si reacted with submicron amorphous carbon layer and amorphous carbon nanoshell to form dispersed SiC nanocrystals and Si–C phase filled at B4C grain boundaries and pores, respectively. The prepared composite had the most outstanding mechanical properties when the Si content in the precursor was 15 wt%, with a hardness reaching 37.8 GPa and a fracture toughness reaching 7.3 MPa·m1/2. Microstructural characterizations indicated that the multi deflection of nanoscale crack caused by intergranular fracture, the covalent bonding of Si–C phase at the grain boundary, and the abundant nanotwin substructure were jointly responsible for the superior performance in hardness and fracture toughness.

The development of high-entropy borides with combined structural and functional performance holds untold scientific and technological potential, yet relevant studies have been rarely reported. In this work, we report nanocrystalline (La0.25Ce0.25Nd0.25Eu0.25)B6high-entropy rare-earth hexaboride (HEReB6-1) ceramics fabricated through the high-pressure sintering of self-synthesized nanopowders for the first time. The as-fabricated samples exhibited a highly dense (96.3%) nanocrystalline (94 nm) microstructure with major (001) fiber textures and good grain boundaries without any impurities, resulting in a remarkable mechanical, electrical, and thermionic emission performance. The results showed that the samples possessed outstanding comprehensive mechanical properties and a high electrical resistivity from room temperature to high temperatures; these were greater than the average values of corresponding binary rare-earth hexaborides, such as a Vickers hardness of 23.4 ± 0.6 GPa and a fracture toughness of 3.0 ± 0.4 MPa•m1/2at room temperature. More importantly, they showed high emission current densities at elevated temperatures, which were higher than the average values of the corresponding binary rare-earth hexaborides. For instance, the maximum emission current density reached 48.3 A•cm−2at 1873 K. Such superior performance makes the nanocrystalline HEReB6-1 ceramics highly suitable for potential applications in thermionic emission cathodes.

Ultrafine-grained (Sm0.2Gd0.2Dy0.2Er0.2Yb0.2)2Zr2O7high-entropy zirconates with single fluorite structure have been fabricated by high-pressure sintering of the self-synthesized nanopowders for the first time. The as-sintered samples exhibit a good microstructure with a grain size of 220 nm and a relative density of 96.8%, which yield excellent comprehensive mechanical properties with a high Vickers hardness of 12.5 GPa and a high fracture toughness of 3.4 MPa·m1/2. In addition, the as-sintered samples possess a good thermostability with the grain growth rate of 30 nm/h, and a low thermal conductivity of 1.57 W·m−1·°C−1at room temperature. The superior mechanical and thermal properties are primarily attributed to the “high-entropy” and grain-refinement effects and good interface bonding.

Exploiting functional characteristics of high-entropy boride materials is critical for extending their potential applications in harsh environments. Herein we develop high-entropy diboride (HEB2) nanoparticles with efficient catalytic performance by engineering their compositions. Based on the theoretical analysis of the lattice size difference and mixing enthalpy of HEB2and the self-propagating combustion mode of the system, six different compositional HEB2nanoparticles are synthesized viaa facile, rapid, and low-cost combustion synthesis method. By engineering their compositions, we achieve the efficient catalytic ability of HEB2nanoparticles in persulfate activation towards antibiotics removal, namely the highest tetracycline removal efficiency of 93.5%. Further investigations of the adsorption energy and the charge density difference of various adsorption sites viadensity functional theory confirm that the outstanding catalytic ability mainly originates from the Ti constituent rather than the high-entropy effect. In addition, a potential catalytic mechanism of HEB2towards persulfate activation for antibiotics degradation is proposed based on the detected reactive oxygen species and the computational reaction energy barrier. This study not only provides theoretical basis for their component design in the efficient catalytic degradation of antibiotics, but also shows a promising application of HEB2for removal of emerging contaminants from environmental water matrices.

Developing superior oxidation resistance of high-entropy diborides is critical for extending their potential applications in harsh environments. Herein, we developed non-equimolar (Hf,Zr,Ta,W)B2high-entropy diborides with superior oxidation resistance by adjusting W contents for the first time. The as-fabricated (Hf0.28Zr0.28Ta0.28W0.15)B2samples are predicted to possess superior oxidation resistance at 1473–1773 K through the oxidation depth quantitative analysis obtained by machine learning, which is attributed to the reason that the moderate WO3can effectively inhibit the volatilization of B2O3. Furthermore, a four-layered structure is found in the generated product layers at 1773 K, which is due to the preferential oxidation of Hf and Zr elements at low oxygen partial pressure and the different diffusion activation energies of oxide products. The preferential oxidation of Hf and Zr elements is further demonstrated by the computational phase stability diagrams, and oxygen adsorption energies and charge transfer between oxygen atoms and different metal adsorption sites viafirst-principles calculations. Such superior performance endows (Hf0.28Zr0.28Ta0.28W0.15)B2with potential applications as ultrahigh-temperature structural materials.

The development of high-entropy carbide nanoparticles merits untold scientific and technological potential, yet their synthesis remains a challenge using conventional synthetic techniques. Herein we present a facile, rapid and low-cost route for the combustion synthesis of (Ta0.25Nb0.25−Zr0.25Ti0.25)C high-entropy carbide (HEC-1) nanoparticles by self-propagating reaction of metal oxides, carbon and Mg mixture precursors in NaF salt media for the first time. The combustion synthesis possibility of HEC-1 is first analyzed theoretically from thermodynamic aspects, and then the ultrafine HEC-1 nanoparticles (average particle size: ∼19 nm) are synthesized successfully by the combustion synthesis technique at combustion temperature of ∼1487 K, duration of 63 s, and heating rate of ∼68 K s−1. The as-synthesized HEC-1 nanoparticles possess high compositional uniformity and low oxygen impurity content of 2.98 wt%. To prove their utility, the as-synthesized HEC-1 nanoparticles are utilized as an effective persulfate activation catalyst for the degradation of tetracycline pollutant in groundwater or wastewater and a removal efficiency of ∼65.5% for tetracycline is obtained after 10 h.

The high-purity and superfine high-entropy zirconate nanopowders, namely (Y0.25La0.25Sm0.25Eu0.25)2Zr2O7nanopowders, without agglomeration, were successfully synthesized via polymerized complex method at low temperatures for the first time. The results showed that the crystallinity degree, lattice strain, and particle size of the as-synthesized powders were gradually enhanced with the increase of the synthesis temperature from 800 to 1300 °C. The as-synthesized powders involved fluorite phase in the range of 800–1200 °C while they underwent the phase evolution from fluorite to pyrochlore at 1300 °C. It is worth mentioning that the as-synthesized powders at 900 °C are of the highest quality among all the as-synthesized powders, which is due to the fact that they not only possess the particle size of 11 nm without agglomeration, but also show high purity and good compositional uniformity.

The goal of this research was to reveal the protective effect and mechanism of fibroblast growth factor-1 (FGF1) on oxidative stress injury of H9c2 cells induced by hydrogen peroxide (H2O2). The effects of various concentrations of H2O2and FGF1 on the activity of H9c2 cells were analyzed by Real Time Cell Analysis (RTCA). The content of ROS, calcium ion, mitochondrial membrane potential and apoptosis were detected by fluorescence probe, the mRNA expression of Bcl-2, Bax and Caspase-3 were detected by real-time PCR to evaluate whether FGF1 has ability to resist the apoptosis of cardiomyocytes caused by oxidative damage. The results showed that the proliferation of H9c2 cells could be inhibited after being treated with 200 μM H2O2for 12 h, and 100 μg/ml FGF1 could increase the proliferation rate of H9c2 cells, mitochondrial membrane potential and the mRNA expression of Bcl-2, and reduce the ROS accumulation, the level of apoptosis, the content of intracellular calcium and the mRNA expression of Bax and Caspase-3 caused by H2O2. The results showed that FGF1 could regulate oxidative stress by improving mitochondrial function and inhibit the H2O2-induced apoptosis in H9c2 cells.

High-entropy nanomaterials have been arousing considerable interest in recent years due to their huge composition space, unique microstructure, and adjustable properties. Previous studies focused mainly on high-entropy nanoparticles, while other high-entropy nanomaterials were rarely reported. Herein, we reported a new class of high-entropy nanomaterials, namely (Ta0.2Nb0.2Ti0.2W0.2Mo0.2)B2high-entropy diboride (HEB-1) nanoflowers, for the first time. Formation possibility of HEB-1 was first theoretically analyzed from two aspects of lattice size difference and chemical reaction thermodynamics. We then successfully synthesized HEB-1 nanoflowers by a facile molten salt synthesis method at 1423 K. The as-synthesized HEB-1 nanoflowers showed an interesting chrysanthemum-like morphology assembled from numerous well-aligned nanorods with diameters of 20–30 nm and lengths of 100–200 nm. Meanwhile, these nanorods possessed a single-crystalline hexagonal structure of metal diborides and highly compositional uniformity from nanoscale to microscale. In addition, the formation of the as-synthesized HEB-1 nanoflowers could be well interpreted by a classical surface-controlled crystal growth theory. This work not only enriches the categories of high-entropy nanomaterials but also opens up a new research field on high-entropy diboride nanomaterials.

Nanocrystalline HfB2powders were successfully synthesized by molten salt synthesis technique at 1373 K using B and HfO2as precursors within KCl/NaCl molten salts. The results showed that the as-synthesized powders exhibited an irregular polyhedral morphology with the average particle size of 155 nm and possessed a single-crystalline structure. From a fundamental aspect, we demonstrated the molten-salt assisted formation mechanism that the molten salts could accelerate the diffusion rate of the reactants and improve the chemical reaction rate of the reactants in the system to induce the synthesis of the high-purity nanocrystalline powders. Thermogravimetric analysis showed that the oxidation of the as-synthesized HfB2powders at 773–1073 K in air was the weight gain process and the corresponding oxidation behavior followed parabolic kinetics governed by the diffusion of oxygen in the oxide layer.

High-entropy ceramics (HECs) are gaining significant interest due to their huge composition space, unique microstructure, and adjustable properties. Previously reported studies focus mainly on HECs with the multi-cationic structure, while HECs with more than one anion are rarely studied. Herein we reported a new class of HECs, namely high-entropy alumino-silicides (Mo0.25Nb0.25Ta0.25V0.25)(Al0.5Si0.5)2(HEAS-1) with multi-cationic and -anionic structure. The formation possibility of HEAS-1 was first theoretically analyzed from the aspects of thermodynamics and lattice size difference based on the first-principles calculations and then the HEAS-1 were successfully synthesized by the solid-state reaction at 1573 K. The as-synthesized HEAS-1 exhibited good single-crystal hexagonal structure of metal alumino-silicides and simultaneously possessed high compositional uniformity. This study not only enriches the categories of HECs but also will open up a new research field on HECs with multi-cationic and -anionic structure.

Herein we establish formation ability descriptors of high-entropy rare-earth monosilicates (HEREMs) viathe data-driven discovery based on the high-throughput solid-state reaction and machine learning (ML) methods. Specifically, adequate high-quality data are generated with 132 samples synthesized by the self-developed high-throughput solid-state reaction apparatuses, and 30 potential descriptors are considered in ML simultaneously. Two classifications are proposed to study the phase formation of HEREMs viathe ML approach combined with the genetic algorithm: (Ⅰ) to distinguish pure HEREMs (X) from other phases and (Ⅱ) to categorize the detail phases of HEREMs (X2, X1, or X2+X1). Four formation ability descriptors (rMe¯, EF¯, δEg, and δZ∗) with a high validation accuracy (96.2%) are proposed as the optimal combination for Classification Ⅰ, where a smaller rMe¯is determined to have the most significant influence on the formation of HEREMs. For Classification Ⅱ, a 100% validation accuracy is achieved by using only two formation ability descriptors (rion¯and δZ∗), where the rion¯is analyzed to be the dominant feature and a lower rion¯is beneficial to the formation of X2-HEREMs. Based on our established formation ability descriptors, 6,045 unreported multicomponent silicates are explored, and 3,478 new HEREMs with 2,700 X2-and 423 X1-HEREMs are predicted.

Diabetic nephropathy (DN) is a common cause of end-stage kidney disease (ESKD) all over the world. Sitagliptin, an inhibitor of DPP-IV plays a beneficial role in type 2 diabetic nephropathy. The purpose of this study was to explore the effect and mechanism of sitagliptin on renal injury in type 1 diabetic mice. Streptozotocin (STZ) induced type 1 diabetic mice were treated with oral administration of sitagliptin (15 mg/kg/ day) for 4 weeks. The results showed that sitagliptin treatment did not change the levels of blood glucose in STZ induced type 1 diabetic mice. Sitagliptin attenuates diabetic nephropathy by significantly inhibiting 24 h proteinuria, renal injury and fibrosis. Sitagliptin can inhibit the expression level of TGF-β1 and the other related fibrosis factors in renal tissue of type 1 diabetic mice while delaying the progression of type 1 diabetic nephropathy. These results indicated that sitagliptin treatment is potentially a new strategy for treating type 1 diabetic nephropathy.

Herein we reported a simple chemical vapor deposition approach to synthesize single crystal α-Al2O3microrods with diameters of 2–4 μm and lengths of 10–30 μm on the as-prepared SiC-Si-Al2O3ceramics based on the screw dislocation growth. Two types of evidence for screw dislocation growth have been conclusively observed in the as-synthesized microrods: scanning electron microscopy analysis reveals that the representative morphology feature of the screw dislocation growth is the stepwise spiral terrace configuration and the growth kinetics of the as-synthesized microrods follows the prediction of the dislocation growth mechanism as described by Burton-Cabrera-Frank theory. This work provides not only a new method for synthesizing Al2O3microrods but also a new insight into the growth mode for Al2O3microrods.

Understanding the initial oxidation mechanism is critical for studying the oxidation resistance of high-entropy diborides. However, related studies are scarce. Herein, the initial oxidation mechanism of (Zr0.25Ti0.25Nb0.25Ta0.25)B2high-entropy diborides (HEB2-1) is investigated by first-principles calculations at the atomic level. By employing the two-region model method, the most stable surface of HEB2-1 is determined to be (112¯0) surface. The dissociative adsorption process of the oxygen molecule on the HEB2-1-(112¯0) surface is predicted to proceed spontaneously, where OO bond breaks and each oxygen atom is chemisorbed on the most preferable hollow site. The adsorption energy and the diffusion barrier of the oxygen atom on the (112¯0) surface of HEB2-1 are in the vicinity of the average level of the corresponding four individual diborides. In addition, ab initio molecular dynamics simulations indicate a high initial oxidation resistance of HEB2-1 at 1000 K. Our results are beneficial to further designing the high-entropy diborides with excellent oxidation resistance.

In order to improve ablation resistance of carbon/carbon (C/C) composites, SiC nanowires were prepared on C/C composites surface in prior through chemical vapor reaction before HfC coating. SiC nanowires grew randomly and had good combination with HfC coating. SiC nanowires toughed HfC coating had lower linear and mass ablation rates than original HfC coating. The surface was much flatter and exhibited smaller cracks in center region. The ablation mechanism of HfC coating has been changed by SiC nanowires. Thicker HfO 2 fused layer was formed on the surface of the toughed HfC coating, which could provide efficient protection for C/C composites. Therefore, SiC nanowires toughed HfC coating behaved in better ablation resistance. [ABSTRACT FROM AUTHOR]