Unexpected Kirkendall effect in twinned icosahedral nanocrystals driven by strain gradient
- PDF / 4,427,865 Bytes
- 9 Pages / 612 x 808 pts Page_size
- 39 Downloads / 149 Views
Unexpected Kirkendall effect in twinned icosahedral nanocrystals driven by strain gradient Jingbo Huang1, Yucong Yan1,2, Xiao Li1, Xurong Qiao3, Xingqiao Wu1, Junjie Li1, Rong Shen1, Deren Yang1 (), and Hui Zhang1 () State Key Laboratory of Silicon Materials, School of Materials Science & Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027, China 2 Advanced Technology Department, SAIC Motor Corporation Limited, Shanghai 201804, China 3 State Key Laboratory of Heavy Oil Processing, School of Materials Science and Engineering, China University of Petroleum, Qingdao 266580, China 1
© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 19 March 2020 / Revised: 25 April 2020 / Accepted: 27 May 2020
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.
KEYWORDS Kirkendall effect, diffusion coefficient, interdiffusion, chemical potential, icosahedral nanocrystals, strain gradient
1
Introduction
As a fundamental metallurgy phenomenon, Kirkendall effect has received great research interests in many technological fields since firstly discovered by Smigelskas and Kirkendall in 1947 [1, 2]. Thanks to Alivisatos et al. [3], Kirkendall effect has been extended to nanoscale and widely used for rationally fabricating hollow nanocrystals in high-quality with tunable morphologies [4, 5], structures [6, 7], compositions [8, 9], and sizes [10]. Over the last decades, a rich variety of hollow nanocrystals made of alloys [5, 6, 11], oxides [12, 13], chalcogenides [14, 15], and phosphides [16] have been successfully generated through Kirkendal
Data Loading...
