Inherent tensile strength of molybdenum nanocrystals

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 (112) [111] and (112)[111] 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).

Atomic mechanisms governing upper limit on the strength of nanosized crystals

“…Unlike macrosized single crystals, nanosized crystals of such transition metals, as Fe, Mo, W, are ductile even at low temperatures. In [4] this was experimentally exhibited for Mo nanoneedles. As it was noted above, this is due to local shear instability in the subsurface layer of a nanosized crystal.…”

“…The experiments were carried out in an ultra-high-vacuum two-chamber field ion microscope (FIM) [4,5] with needle-shaped specimens cooled to 77 K. Field ion images were formed by using helium atoms under a pressure of 10 -3 Pa; the residual gas pressure was about 10 −5 Pa. For in situ mechanical testing, the specimens were prepared from 0. 15 The surface density of ponderomotive forces at the apex of a nanoneedle was determined as [5] …”

Physical properties of elongated inorganic nanoparticles

“…Cu whiskers for instance have shown significantly high yield strengths, of the order of a few GPa [563]. Tensile tests of dislocation and microcrack free ⟨110⟩-oriented single crystalline elongated molybdenum nanoparticles, with diameters ranging from 25 to 90 nm (at the apex region) were conducted inside a field-ion microscope (FIM) [564]. The experimental values of tensile strength varied between 6.3 and 19.8 GPa and increased with decreasing nanorod diameter.…”

Relation between the strength and dimensionality of defect-free carbon crystals

“…The critical value of the force at the moment of instability of the graphene sheet was determined by Eqs. (1) and (2). According to the results obtained, the strength of atomic bonds in graphene for armchair direction was 8.9 nN and for zigzag direction-8.3 nN.…”

“…Removal of defects is an alternative way to increase the material strength. Nanosized crystals are an example of this [1][2][3]. However, new factor appears in this case, which influences strength essentially.…”