A plausible mechanism for the evolution of helical forms in nanostructure growth

Bandaru, Prabhakar R.; Daraio, Chiara; Yang, Keqin; Rao, Apparao M.

doi:10.1063/1.2723189

Cited by 61 publications

(49 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It is also noted that the above mechanisms cannot be invoked for amorphous carbon nanocoils [16] and compound (e.g., boron carbide) nanowires. [13] To provide a comprehensive explanation, we have proposed a thermodynamic model, [25] where helix/coil formation is explained on the basis of the interactions between specific catalyst particles and the growing nanostructure. We use the degree of wettability of the nanostructure surface by the catalysts as a criterion for coiling.…”

mentioning

confidence: 99%

Rational Synthesis of Helically Coiled Carbon Nanowires and Nanotubes through the Use of Tin and Indium Catalysts

et al. 2007

Self Cite

View full text Add to dashboard Cite

Helically coiled carbon nanotubes (HCNTs) and nanowires (HCNWs) represent novel nanostructural morphology and have technological and scientific significance. Their potential applications [1] span high frequency electronics, [2] tactile and magnetic [3] sensors, and structural foams for cushioning and energy dissipation. [4,5] It is also interesting to make a connection between the CVD synthesized helical carbon nanostructures to organic forms found in nature, such as DNA and proteins, and indeed, these structures can be used for templates in collagen growth. [6] It was also suggested that a coil could correspond [7] to a sequence of alternating metallic/semiconducting junctions, which is very interesting from the point of view of application to nanoelectronic systems. [8,9] While several groups have previously reported on the synthesis of coiled nanostructures using chemical vapor deposition (CVD), patterned substrates [10][11][12][13][14][15][16] were always used.While mostly HCNWs are seen, there have also been a few reports on the synthesis of HCNTs. [17,18] Patterned growth of coiled nanotubes based on using previously aligned straight CNTs as templates was also demonstrated. [19] It is typically found that such methods, in addition to limiting the amount of material due to the catalyst distribution, is often accompanied by the formation of linear multiwalled nanotubes. [20] It would be desirable to develop a process that is independent of the underlying substrate, utilizing gas-phase synthesis alone, [18] with controllable coiling characteristics (i.e., length, pitch etc.). In this paper, we report on a liquid-precursor-based synthesis method which has the additional advantage that either coiled nanotubes or nanowires, with differing electrical and mechanical properties, [5,8,21] can be fabricated. We provide a rational explanation for the distinct growth modes based on an analysis of the binary equilibrium phase diagrams, where the mutual affinity of secondary catalysts (In/Sn), with the primary catalyst (Fe) in the ferrocene-xylene mixture, promotes nanotube/-wire formation. Coiled carbon nanostructures have been predicted to be energetically stable, [22] and various mechanisms have been posited for their formation. While the curvature, in the case of helically coiled single-walled nanotubes could possibly be due to the regular insertion of pentagon-heptagon pairs at the junctions, [23] it is unclear if a similar mechanism could hold for multiwalled nanotubes and HCNWs. Other formation mechanisms invoke localized stresses and anisotropic rates of carbon deposition [19,24] on faceted catalyst particles.[17] However, there is no experimental evidence for the above, as it is seen that helical structure is induced even though catalyst particles are not obviously present in the structure. It is also noted that the above mechanisms cannot be invoked for amorphous carbon nanocoils [16] and compound (e.g., boron carbide) nanowires. [13] To provide a comprehensive explanation, we have proposed a thermodynamic model...

show abstract

mentioning

confidence: 99%

Rational Synthesis of Helically Coiled Carbon Nanowires and Nanotubes through the Use of Tin and Indium Catalysts

et al. 2007

Self Cite

View full text Add to dashboard Cite

show abstract

“…More recently, Fonseca et al (2007) studied the effect of catalyst shape on the cross-sectional shape of nanosprings and discussed the possibility of growth of normal and binormal nanosprings. In addition, Amelinckx et al (1994) proposed a spatial velocity hodograph-based model to interpret the helical growth of carbon nanotubes, and Bandaru et al (2007) addressed the formation mechanisms of helical nanotube/fibres from the viewpoint of thermodynamics.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic surface effects on the formation of chiral morphologies of nanomaterials

Wang

Qin

et al. 2011

Proc. R. Soc. A.

View full text Add to dashboard Cite

Nanomaterials with chiral morphologies hold promise for a wide diversity of technologically important applications in such fields as micro/nano-electromechanical systems and medical engineering. Understanding the mechanisms underlying the formation of chiral morphologies of natural and synthesized materials remains an issue of crucial significance. In this study, a refined Kirchhoff rod model taking into account anisotropic surface effects is employed to describe quasi-one-dimensional nanomaterials with complicated spatial morphologies. It is shown that anisotropic surface stresses can induce the formation of rich morphologies of nanomaterials. A general shape equation of nanowires is derived by the variational method of energy. Thereby, the effects of anisotropic surface properties, bulk elastic properties and cross-sectional sizes on the chiral morphologies of nanomaterials are quantitatively investigated, and the conditions for the formation of binormal nanohelices are given. The physical mechanism addressed in this study is verified by our recent experiments on tuning the twisting chirality of polymer lamellae via surface treatments. Our analysis suggests that one can design and adjust the morphology of synthesized nanohelices by tailoring or functionalizing their surfaces during fabrication. This study is also helpful in interpreting the formation of such artificial and biological chiral materials as the flagella of bacterial and self-assembled helical ribbons.

show abstract

“…1(a)] under impact of a drop ball has been reported [12]. The experiment consisted of producing arrays of bundles of CCNTs [13,14], letting a stainless steel bead fall down on the forest of CCNTs, and measuring the dynamic force at the wall below the forest during the stages of penetration and restitution. The analysis of the forest's morphology after impact has shown no trace of plastic deformation and a full recovery of the foamlike layer of CCNTs under various impact velocities.…”

mentioning

confidence: 99%

Entanglement and the Nonlinear Elastic Behavior of Forests of Coiled Carbon Nanotubes

et al. 2008

Self Cite

View full text Add to dashboard Cite

Helical or coiled nanostructures have been objects of intense experimental and theoretical studies due to their special electronic and mechanical properties. Recently, it was experimentally reported that the dynamical response of a foamlike forest of coiled carbon nanotubes under mechanical impact exhibits a nonlinear, non-Hertzian behavior, with no trace of plastic deformation. The physical origin of this unusual behavior is not yet fully understood. In this Letter, based on analytical models, we show that the entanglement among neighboring coils in the superior part of the forest surface must be taken into account for a full description of the strongly nonlinear behavior of the impact response of a drop ball onto a forest of coiled carbon nanotubes.

show abstract

A plausible mechanism for the evolution of helical forms in nanostructure growth

Cited by 61 publications

References 39 publications

Rational Synthesis of Helically Coiled Carbon Nanowires and Nanotubes through the Use of Tin and Indium Catalysts

Rational Synthesis of Helically Coiled Carbon Nanowires and Nanotubes through the Use of Tin and Indium Catalysts

Anisotropic surface effects on the formation of chiral morphologies of nanomaterials

Entanglement and the Nonlinear Elastic Behavior of Forests of Coiled Carbon Nanotubes

Contact Info

Product

Resources

About