Search

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.

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.

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.