Kinetics of Nanotube and Microfiber Scission under Sonication

Lucas, Antoine; Zakri, Cécile; Maugey, Maryse; Pasquali, Matteo; Schoot, Paul van der; Poulin, Philippe

doi:10.1021/jp906296y

Cited by 181 publications

(180 citation statements)

References 55 publications

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“…5,21 Indeed, exfoliation goes hand-in-hand with tube scission, and long tubes break more easily than short ones. 49 In fact, wide tubes break less easily than narrow ones, casting doubt on the assumption of independent length and width distributions that we presumed so far. This turns out to be a crucial insight.…”

Section: Realistic Size Distributionsmentioning

confidence: 79%

Connectivity percolation of polydisperse anisotropic nanofillers

Otten¹,

Schoot²

2011

The Journal of Chemical Physics

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127

168

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We present a generalized connectedness percolation theory reduced to a compact form for a large class of anisotropic particle mixtures with variable degrees of connectivity. Even though allowing for an infinite number of components, we derive a compact yet exact expression for the mean cluster size of connected particles. We apply our theory to rodlike particles taken as a model for carbon nanotubes and find that the percolation threshold is sensitive to polydispersity in length, diameter, and the level of connectivity, which may explain large variations in the experimental values for the electrical percolation threshold in carbon-nanotube composites. The calculated connectedness percolation threshold depends only on a few moments of the full distribution function. If the distribution function factorizes, then the percolation threshold is raised by the presence of thicker rods, whereas it is lowered by any length polydispersity relative to the one with the same average length and diameter. We show that for a given average length, a length distribution that is strongly skewed to shorter lengths produces the lowest threshold relative to the equivalent monodisperse one. However, if the lengths and diameters of the particles are linearly correlated, polydispersity raises the percolation threshold and more so for a more skewed distribution toward smaller lengths. The effect of connectivity polydispersity is studied by considering nonadditive mixtures of conductive and insulating particles, and we present tentative predictions for the percolation threshold of graphene sheets modeled as perfectly rigid, disklike particles.

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Section: Realistic Size Distributionsmentioning

confidence: 79%

Connectivity percolation of polydisperse anisotropic nanofillers

Otten¹,

Schoot²

2011

The Journal of Chemical Physics

Self Cite

127

168

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“…This same power law captures the dependence of length on sonication energy, showing that sonication time and power have a combined effect (4). Yet the literature disagrees on the power law exponent m. Various values for this exponent have been reported: m ∼ 0.5 (5) and m ∼ 0.22 (4).…”

mentioning

confidence: 78%

“…Prior studies have monitored the effects of sonication on CNT dispersion quality and length (3)(4)(5)(6)(7). Most of these studies sonicated a sample under controlled conditions and monitored bundle diameter and length.…”

mentioning

confidence: 99%

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Competing mechanisms and scaling laws for carbon nanotube scission by ultrasonication

Pagani

Green

Poulin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Dispersion of carbon nanotubes (CNTs) into liquids typically requires ultrasonication to exfoliate individuals CNTs from bundles. Experiments show that CNT length drops with sonication time (or energy) as a power law t −m . Yet the breakage mechanism is not well understood, and the experimentally reported power law exponent m ranges from approximately 0.2 to 0.5. Here we simulate the motion of CNTs around cavitating bubbles by coupling Brownian dynamics with the Rayleigh-Plesset equation. We observe that, during bubble growth, CNTs align tangentially to the bubble surface. Surprisingly, we find two dynamical regimes during the collapse: shorter CNTs align radially, longer ones buckle. We compute the phase diagram for CNT collapse dynamics as a function of CNT length, stiffness, and initial distance from the bubble nuclei and determine the transition from aligning to buckling. We conclude that, depending on their length, CNTs can break due to either buckling or stretching. These two mechanisms yield different power laws for the length decay (0.25 and 0.5, respectively), reconciling the apparent discrepancy in the experimental data.T he dispersion of carbon nanotubes (CNTs) in liquids is critical for the use of CNTs in applications ranging from biomedical sensors to structural composites (1). However, CNTs form insoluble bundles and ropes during production due to van der Waals attraction. Commonly, CNTs are exfoliated and dispersed in liquids by sonication, where energy is supplied to the system as ultrasonic waves. These waves induce cavitation, which leads to progressive exfoliation of bundles into individual CNTs. Understanding dispersion by sonication is critical for the use of CNTs in biological and materials applications (2).Prior studies have monitored the effects of sonication on CNT dispersion quality and length (3-7). Most of these studies sonicated a sample under controlled conditions and monitored bundle diameter and length. Although sonication decreases bundle diameter at short times as individual CNTs are exfoliated, it also cuts the CNTs. Shortening has been observed for both singlewalled and multiwalled CNTs (SWNTs and MWNTs) (4, 5).Similar shortening occurs during sonication of polymer solutions (5,(8)(9)(10)(11)(12), where the mechanism is well established; cavitation induces high strain rates in the liquid, stretching polymer molecules to failure. Although the mechanism of CNT shortening remains unclear, there are some similarities between sonicated polymers and CNTs. Like polymers, CNTs show a nonrandom cutting pattern; i.e., they break near their center of mass (CoM) (5). Similar to polymers, the kinetics of CNT shortening are length-dependent, and sonicated CNTs approach a limiting length, below which no shortening occurs (6, 13). Evidence suggests that thermal effects (due to local temperature rise during bubble collapse) are negligible and mechanical effects dominate (6,14,15).Experiments consistently report a power law relation between CNTs' average length and sonication time L ∼ t −m . Th...

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“…SDS is a surfactant that stabilizes the nanotubes in water. The dispersions are homogenized by a sonication treatment during 90 min using a Branson S-450D tip sonicator operating at 40 W. Sonication induces the scission of the nanotubes (32)(33)(34)(35) and the average length of the nanotubes after the present treatments is about 500 nm. The quality of the dispersion is assessed before fiber spinning.…”

Section: Methodsmentioning

confidence: 99%

Kinetics of fiber solidification

Mercader

Lucas

Derré

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Many synthetic or natural fibers are produced via the transformation of a liquid solution into a solid filament, which allows the wet processing of high molecular weight polymers, proteins, or inorganic particles. Synthetic wet-spun fibers are used in our everyday life from clothing to composite reinforcement applications. Spun fibers are also common in nature. Silk solidification results from the coagulation of protein solutions. The chemical phenomena involved in the formation of all these classes of fibers can be quite different but they all share the same fundamental transformation from a liquid to a solid state. The solidification process is critical because it governs the production rate and the strength that fibers can sustain to be drawn and wound. An approach is proposed in this work to investigate the kinetics of fiber solidification. This approach consists in circulating solidifying fibers in the extensional flow of a surrounding liquid. Such as polymers in extensional flows, the fibers break if resultant drag forces exceed the fiber tensile strength. The solidification kinetics of nanotube composite fibers serves as a validation example of this approach. The method could be extended to other systems and advance thereby the science and technology of fiber and textile materials. It is also a way to directly visualize the scission of chain-like systems in extensional flows.diffusion | elongational | microfluidic | rheology

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Kinetics of Nanotube and Microfiber Scission under Sonication

Cited by 181 publications

References 55 publications

Connectivity percolation of polydisperse anisotropic nanofillers

Connectivity percolation of polydisperse anisotropic nanofillers

Competing mechanisms and scaling laws for carbon nanotube scission by ultrasonication

Kinetics of fiber solidification

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