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Exploring radiation damage in (Hf0.2Zr0.2Ta0.2Ti0.2Nb0.2)C high-entropy carbide ceramic: Integrating experimental and atomistic investigations

Research Authors
Gaowei Zhang, Nabil Daghbouj, A. T. AlMotasem, Zhongqiang Fang, Tao Wang, Jian Zhang, Tongming Zhang, Jun Li, Junjun Zhou, Shuai Xu , Renda Wang , Lu Wu , Fangfang Ge , Tomas Polcar , Wentuo Han
Research Abstract

This study investigates the intricate mechanisms that govern irradiation damage in high-entropy ceramic materials. Specifically, we synthesized (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)C high-entropy carbide ceramics (HECC) with a single-phase rock-salt structure using spark plasma sintering. These ceramics were then subjected to irradiation with 1.08 MeV C ions, resulting in a dose of 7.2 dpa (dpa: displacements per atom) at both room temperature (RT) and 500 °C. To understand the resulting damage structure, we analyzed bulk irradiated HECC samples using Grazing Incidence X-ray Diffraction (GIXRD) and Transmission Electron Microscope (TEM) at both irradiation temperatures. GIXRD analysis revealed an average tensile strain out-of-plane of 0.16% for RT irradiation and 0.14% for irradiation at 500 °C. In addition, TEM analysis identified a buried damaged band, approximately 970 nm thick, under both irradiation temperatures. By employing the bright field TEM imaging technique under kinematic two-beam conditions, dislocation loops of both a/3 〈111〉{111} and a/2 〈110〉{110} types within the damaged band were observed. Furthermore, our analysis indicated an increase in the average size of the total dislocation loops within the band from 1.2 nm to 1.4 nm as the density decreased. Importantly, no amorphization, precipitates, or voids were detected in the damaged band under both irradiation temperatures. Density functional theory (DFT) simulations indicated that carbon predominantly resides in 〈110〉 split interstitial sites causing lattice expansion, while vacancies, particularly Nb, induced compression along the c-axis. Carbon atoms tend to bond when collectively present in the <110> split interstitial sites, contributing to the formation of interstitial loops.

Research Date
Research Department
Research Journal
International Journal of Refractory Metals and Hard Materials
Research Publisher
Elsevier
Research Rank
Q1
Research Vol
123
Research Website
https://www.sciencedirect.com/science/article/abs/pii/S0263436824002038?via%3Dihub
Research Year
2024
Research Pages
106755