Single-Crystal Nanorings Formed by Epitaxial Self-Coiling of Polar Nanobelts

Science

Volumn 303, Issue 5662, 2004, Pages 1348-1351

  Kong, Xiang Yang ^a   Ding, Yong ^a   Yang, Rusen ^a   Wang, Zhong Lin ^a  

^a Georgia Institute of Technology   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

BONDING; DEFORMATION; ELASTICITY; ELECTROSTATICS; SINGLE CRYSTALS; ZINC OXIDE;

NANOBELTS; NANORINGS;

NANOSTRUCTURED MATERIALS;

ZINC OXIDE;

NANOTECHNOLOGY;

ARTICLE; CHEMICAL BINDING; CRYSTAL; CRYSTAL STRUCTURE; ELECTRICITY; ENERGY; PRIORITY JOURNAL; SCANNING ELECTRON MICROSCOPY; TRANSMISSION ELECTRON MICROSCOPY;

EID: 1442330252     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.1092356     Document Type: Article

References (21)

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12. There are three components of energy involved in the formation of ring structure: electrostatic interaction energy among the polar charges, surface area energy due to the decrease in surface area after chemically bonding the loops, and elastic deformation energy due to bending. The former two are usually called the surface energy, which includes the contribution from surface tension, but we separate them here for the convenience of discussion in the text. Electrostatic and deformation forces are long-range interactions, and chemical bonding is a short-range interaction. Self-coiling is possible if the decreased electrostatic energy surpasses the increased elastic deformation energy, which is the case for a thin and narrow nanobelt.
13. Sintering in ceramics usually involves mass transport and diffusion. By "epitaxial sintering" here, we mean that the two loops are chemically bonded epitaxially with the same crystal orientation, and there may be no diffusion involved. As the nanobelt grew along its axial direction as guided by the planar defect, it was being bonded down on the rim of the ring by electrostatic interaction. Because the melting point for a nanostructure can be as low as one-third of its bulk melting point, and the temperature required for sintering is usually one-third of the melting temperature, it is thus possible to chemically join the loops at 200° to 400°C.
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21. Support was provided by NSF (DMR-9733160), the NASA Vehicle Systems Program, and the Department of Defense Research and Engineering (DDR&E) program. We thank R. L. Snyder and J. Z. Zhang for comments.