Abstract
Cavitation and hollow structures can be introduced in nanomaterials via the Kirkendall effect in an alloying or reaction system. By introducing dense nanoscale twins into copper nanowires (CuNWs), we change the surface structure and prohibit void formation in oxidation of the nanowires. The nanotwinned CuNW exhibits faceted surfaces of very few atomic steps as well as a very low vacancy generation rate at copper/oxide interfaces. Together they lower the oxidation rate and eliminate void formation at the copper/oxide interface. We propose that the slow reaction rate together with the highly effective vacancy absorption at interfaces leads to a lattice shift in the oxidation reaction. Our findings suggest that the nanoscale Kirkendall effect can be manipulated by controlling the internal and surface crystal defects of nanomaterials.
Highlights
Cavitation and hollow structures can be introduced in nanomaterials via the Kirkendall effect in an alloying or reaction system
We report the oxidation of a CuNW as an example to demonstrate how cavitation in nanomaterials is eliminated by modifying the nanoscale surface structure with a high-density nanoscale coherent twin boundary (CTB)
The CuNW surface turns into a faceted structure of a very low atomic step density when intercepted by abundant CTBs, which decreases the rates of copper oxidation and vacancy generation at copper/oxide interfaces
Summary
Cavitation and hollow structures can be introduced in nanomaterials via the Kirkendall effect in an alloying or reaction system. The influences of CTBs on dislocation glide, electron transport and atomic diffusion are different from those of ITB and high-angle GBs. Recent experimental and modeling work towards understanding the effects of nanotwinned structure on mechanical and physical properties of metallic materials can be found in the review articles[12,13]. One recent study has shown that Kirkendall voiding is suppressed at the interface between a solder alloy and a -oriented copper film with dense CTBs in parallel to film surface because excess vacancies are eliminated by abundant ITBs15. Nanoscale materials such as nanoparticles (NPs) and nanowires (NWs) usually have a limited capacity for lattice shift. A slow and orderly vacancy absorption behavior at interfaces causes a lattice shift without void formation in the oxidation reaction
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