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Nano Research

Article Title

Unexpected Kirkendall effect in twinned icosahedral nanocrystals driven by strain gradient

Authors

Jingbo Huang, State Key Laboratory of Silicon Materials, School of Materials Science & Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027, China
Yucong Yan, State Key Laboratory of Silicon Materials, School of Materials Science & Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027, China Advanced Technology Department, SAIC Motor Corporation Limited, Shanghai 201804, China
Xiao Li, State Key Laboratory of Silicon Materials, School of Materials Science & Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027, China
Xurong Qiao, State Key Laboratory of Heavy Oil Processing, School of Materials Science and Engineering, China University of Petroleum, Qingdao 266580, China
Xingqiao Wu, State Key Laboratory of Silicon Materials, School of Materials Science & Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027, China
Junjie Li, State Key Laboratory of Silicon Materials, School of Materials Science & Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027, China
Rong Shen, State Key Laboratory of Silicon Materials, School of Materials Science & Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027, China
Deren Yang, State Key Laboratory of Silicon Materials, School of Materials Science & Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027, China
Hui Zhang, State Key Laboratory of Silicon Materials, School of Materials Science & Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027, China

Keywords

Kirkendall effect, diffusion coefficient, interdiffusion, chemical potential, icosahedral nanocrystals, strain gradient

Abstract

Nanoscale Kirkendall effect has been widely used for rationally fabricating high-quality hollow nanocrystals, but often requires the intrinsic diffusion coefficient of out-diffusion materials higher than that of in-diffusion components. Here we demonstrate an unexpected Kirkendall effect that occurs in diffusing intrinsically faster Cu atoms into Pd icosahedra, leading to the formation of PdCu alloyed hollow nanocrystals. The control experiment with Pd octahedra replacing icosahedra indicates the critical role of twin boundaries in facilitating such unexpected Kirkendall effect. In addition, geometric phase analysis and density functional theory calculation show that out-diffusion of Pd atoms in the icosahedra is faster than in-diffusion of Cu atoms, particularly through the twin boundaries, upon the strain gradient with an inward distribution from tensile to compressive strains. The unexpected Kirkendall effect is also found in the interdiffusion of Ag and Pd atoms in Pd icosahedra. Our finds break the limitation of the intrinsic diffusion coefficient for the synthesis of hollow nanocrystals through Kirkendall effect and are expected to enormously enrich the family of hollow nanocrystals which have shown great potential in broad areas, such as fine chemical production, energy storage and conversion, and environmental protection. This work also provides a deep understanding in the diffusion behavior of atoms upon the strain gradient.

Graphical Abstract

Publisher

Tsinghua University Press

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