title: In Situ Observation on Dislocation-Controlled Sublimation of Mg Nanoparticles.
abstract: Sublimation is an important endothermic phase transition in which the atoms break away from their neighbors in the crystal lattice and are removed into the gas phase. Such debonding process may be significantly influenced by dislocations, the crystal defect that changes the bonding environment of local atoms. By performing systematic defects characterization and in situ transmission electron microscopy (TEM) tests on a core--shell MgO-Mg system, which enables us to "modulate" the internal dislocation density, we investigated the role of dislocations on materials' sublimation with particular focus on the sublimation kinetics and mechanism. It was observed that the sublimation rate increases significantly with dislocation density. As the density of screw dislocations is high, the intersection of screw dislocation spirals creates a large number of monatomic ledges, resulting in a "liquid-like" motion of solid-gas interface, which significantly deviates from the theoretically predicted sublimation plane. Our calculation based on density functional theory demonstrated that the remarkable change of sublimation rate with dislocation density is due to the dramatic reduction in binding energy of the monatomic ledges. This study provides direct observation to improve our understanding on this fundamental phase transition as well as to shed light on tuning materials' sublimation by "engineering" dislocation density in applications.
authors.affiliation: Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University , Hangzhou, China , 310027.
authors.forename: Qian
authors.initials: Q
authors.lastname: Yu
authors.affiliation: Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University , Hangzhou, China , 310027.
authors.forename: Min-Min
authors.initials: MM
authors.lastname: Mao
authors.affiliation: Department of Materials Science and Engineering, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Qing-Jie
authors.initials: QJ
authors.lastname: Li
authors.affiliation: Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University , Hangzhou, China , 310027.
authors.forename: Xiao-Qian
authors.initials: XQ
authors.lastname: Fu
authors.affiliation: Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University , Hangzhou, China , 310027.
authors.forename: He
authors.initials: H
authors.lastname: Tian
authors.affiliation: Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University , Hangzhou, China , 310027.
authors.forename: Ji-Xue
authors.initials: JX
authors.lastname: Li
authors.affiliation: Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University , Hangzhou, China , 310027.|Department of Mechanical Engineering and Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Scott X
authors.initials: SX
authors.lastname: Mao
authors.affiliation: Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University , Hangzhou, China , 310027.
authors.forename: Ze
authors.initials: Z
authors.lastname: Zhang
keywords: Dislocation density; Mg nanoparticles; monatomic ledge; sublimation rate; “liquid-like” motion