Open Access Research Article Issue
Data-driven discovery of formation ability descriptors for high-entropy rare-earth monosilicates
Journal of Materiomics 2024, 10 (3): 738-747
Published: 20 December 2023
Abstract Collect

Herein we establish formation ability descriptors of high-entropy rare-earth monosilicates (HEREMs) via the 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 via the 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.

Open Access Research Article Issue
Atomic-level insights into the initial oxidation mechanism of high-entropy diborides by first-principles calculations
Journal of Materiomics 2024, 10 (2): 423-430
Published: 02 August 2023
Abstract Collect

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)B2 high-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 (110) surface. The dissociative adsorption process of the oxygen molecule on the HEB2-1-(110) 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 (110) 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.

Open Access Research Article Issue
Ultrafine-grained high-entropy zirconates with superior mechanical and thermal properties
Journal of Materiomics 2023, 9 (2): 370-377
Published: 17 October 2022
Abstract Collect

Ultrafine-grained (Sm0.2Gd0.2Dy0.2Er0.2Yb0.2)2Zr2O7 high-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·℃−1 at room temperature. The superior mechanical and thermal properties are primarily attributed to the “high-entropy” and grain-refinement effects and good interface bonding.

Open Access Research Article Issue
Synthesis of the superfine high-entropy zirconate nanopowders by polymerized complex method
Journal of Advanced Ceramics 2022, 11 (1): 136-144
Published: 24 December 2021
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The high-purity and superfine high-entropy zirconate nanopowders, namely (Y0.25La0.25Sm0.25Eu0.25)2Zr2O7 nanopowders, 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 ℃. The as-synthesized powders involved fluorite phase in the range of 800-1200 ℃ while they underwent the phase evolution from fluorite to pyrochlore at 1300 ℃. It is worth mentioning that the as-synthesized powders at 900 ℃ 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.

Open Access Research Article Issue
Chrysanthemum-like high-entropy diboride nanoflowers: A new class of high-entropy nanomaterials
Journal of Advanced Ceramics 2020, 9 (3): 339-348
Published: 05 June 2020
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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)B2 high-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.

Open Access Research Article Issue
Molten salt synthesis, formation mechanism, and oxidation behavior of nanocrystalline HfB2 powders
Journal of Advanced Ceramics 2020, 9 (1): 35-44
Published: 05 February 2020
Abstract PDF (11.7 MB) Collect

Nanocrystalline HfB2 powders were successfully synthesized by molten salt synthesis technique at 1373 K using B and HfO2 as 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 HfB2 powders 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.

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