Sm-composition engineering of (Hf, Zr, Ta, Sm)B2 high-entropy diborides for superior oxidation resistance

Abstract

Herein we realize the development of (Hf, Zr, Ta, Sm)B2 high-entropy diborides (HEBs-Sm) with superior oxidation resistance by engineering the compositions of Sm. Specifically, HEBs-Sm with 0–25 mol% Sm contents are first fabricated via borothermal reduction and hot-pressing sintering. Then the HEB-18Sm is predicted to possess the best oxidation resistance at 1473–1773 K via machine learning based on the oxidation depth. Ab initio molecular dynamics simulations indicate that moderate (Sm, Hf, Zr, Ta)2O3 oxidation product facilitates the formation of a three-dimensional skeletal structure in B2O3, which increases the viscosity of B2O3 glass and therefore improves the oxidation resistance of HEBs-Sm.