24 research outputs found
A molecular simulation analysis of producing monatomic carbon chains by stretching ultranarrow graphene nanoribbons
Atomistic simulations were utilized to develop fundamental insights regarding
the elongation process starting from ultranarrow graphene nanoribbons (GNRs)
and resulting in monatomic carbon chains (MACCs). There are three key findings.
First, we demonstrate that complete, elongated, and stable MACCs with fracture
strains exceeding 100% can be formed from both ultranarrow armchair and zigzag
GNRs. Second, we demonstrate that the deformation processes leading to the
MACCs have strong chirality dependence. Specifically, armchair GNRs first form
DNA-like chains, then develop into monatomic chains by passing through an
intermediate configuration in which monatomic chain sections are separated by
two-atom attachments. In contrast, zigzag GNRs form rope-ladder-like chains
through a process in which the carbon hexagons are first elongated into
rectangles; these rectangles eventually coalesce into monatomic chains through
a novel triangle-pentagon deformation structure under further tensile
deformation. Finally, we show that the width of GNRs plays an important role in
the formation of MACCs, and that the ultranarrow GNRs facilitate the formation
of full MACCs. The present work should be of considerable interest due to the
experimentally demonstrated feasibility of using narrow GNRs to fabricate novel
nanoelectronic components based upon monatomic chains of carbon atoms.Comment: 11 pages, 6 figures, Nanotechnology accepted versio
Measurement of the Ideal Strength of Graphene Nanosheets
The uniaxial tensile strength of graphene nanosheets at 77 K was determined by the method of loading two dimensional nano objects with strong electric fields. It was shown that, for graphene sheets 0.5 to 2.8 nm thick, the maximum strength within the measurement error does not depend on the thickness of the sheets. The average strength, due to significant statistical dispersion, was 43 lower than its maximum value 92 GPa . The strength of graphene nanosheets is almost an order of magnitude greater than the strength of nanoneedle samples made from original carbon fibres. Evidence that graphene nanosheet strength does not depend upon sheet depth indicates the achievement of the ideal strength of these object
Inherent tensile strength of molybdenum nanocrystals
The strength of Mo nanorods was measured under uniaxial tension. Tensile tests of lang 110rang-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 (11ar{2})[111] and (112)[11ar{1}] 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)