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, 10 (4), 045004
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Inherent Tensile Strength of Molybdenum Nanocrystals

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Inherent Tensile Strength of Molybdenum Nanocrystals

Anatoly P Shpak et al. Sci Technol Adv Mater.

Abstract

The strength of Mo nanorods was measured under uniaxial tension. Tensile tests of 〈 110〉-oriented single-crystalline molybdenum rod-shaped specimens with diameters from 25 to 90 nm at the apex were conducted inside a field-ion microscope (FIM). The nanocrystals were free from dislocations, planar defects and microcracks, and exhibited the plastic mode of failure under uniaxial tension with the formation of a chisel-edge tip by multiple gliding in the [Formula: see text] and [Formula: see text] deformation systems. The experimental values of tensile strength vary between 6.3 and 19.8 GPa and show a decrease with increasing nanorod diameter. A molecular dynamic simulation of Mo nanorod tension also suggests that the strength decreases from 28.8 to 21.0 GPa when the rod diameter increases from 3.1 to 15.7 nm. The maximum values of experimental strength are thought to correspond to the inherent strength of Mo nanocrystals under uniaxial tension (19.8 GPa, or 7.5% of Young's modulus).

Keywords: field evaporation; field-ion microscopy; molybdenum; nanocrystal; strength.

Figures

Figure 1
Figure 1
formula image versus F plot for 〈 110〉-oriented molybdenum.
Figure 2
Figure 2
Real field at the specimen apex versus geometric field. 1, geometric field; 2, 3, and 4, obtained from equation (12) with r0 equal to 14, 25 and 50 nm, respectively; the inset is a TEM image of a molybdenum tip formed by field evaporation at 77 K (r0=50 nm).
Figure 3
Figure 3
FIM image of monocrystalline molybdenum nanorod before failure at 77 K (a) and corresponding stereographic projection (b).
Figure 4
Figure 4
FIM images of monocrystalline molybdenum nanocrystal after failure at 77 K at V0/Vp=0 (a) and V0/Vp=0.55 (b). The high-voltage pulse duration is 20 ns.
Figure 5
Figure 5
Tomographic 2D reconstruction of the chisel cross section obtained from a layer-by-layer field evaporation sequence (a) and sketch of chisel-edge-type failure due to plastic deformation of a nanotip (b).
Figure 6
Figure 6
Tensile strength of molybdenum nanocrystals at 77 K; the inset shows a TEM image of the molybdenum tip after chisel-edge-type failure.

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