Computational Investigation of Large-Diameter Carbon Nanotubes in Bundles for High-Strength Materials

Onuoha, C. Emmanuel; Drozdov, Grigorii; Liang, Zhiyong; Odegard, Gregory M.; Siochi, Emilie J.; Dumitrică, Traian

doi:10.1021/acsanm.0c01462

Cited by 10 publications

(21 citation statements)

References 30 publications

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“…[206] Collapsed CNTs into a "dog-bone" structure have the advantage of greater innertube friction and higher density; tightbinding atomistic calculations have demonstrated a Young's modulus of 1100 GPa. [208] Amorphous carbon, [205] oligomeric by-products from CVD reactors, [209] and post-process cross-lin king [175,195,[210][211][212] tie individual CNTs together, increasing their overall strength. Finite element analysis [205] demonstrated that, for perfectly packed, aligned, and impurity free CNT fibers under load, the stress distribution varies substantially in the radial direction, being stronger on the surface and tapering off in the fiber core.…”

Section: Extrinsic Characteristicsmentioning

confidence: 99%

A Meta‐Analysis of Conductive and Strong Carbon Nanotube Materials

2021

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A study of 1304 data points collated over 266 papers statistically evaluates the relationships between carbon nanotube (CNT) material characteristics, including: electrical, mechanical, and thermal properties; ampacity; density; purity; microstructure alignment; molecular dimensions and graphitic perfection; and doping. Compared to conductive polymers and graphitic intercalation compounds, which have exceeded the electrical conductivity of copper, CNT materials are currently one‐sixth of copper's conductivity, mechanically on‐par with synthetic or carbon fibers, and exceed all the other materials in terms of a multifunctional metric. Doped, aligned few‐wall CNTs (FWCNTs) are the most superior CNT category; from this, the acid‐spun fiber subset are the most conductive, and the subset of fibers directly spun from floating catalyst chemical vapor deposition are strongest on a weight basis. The thermal conductivity of multiwall CNT material rivals that of FWCNT materials. Ampacity follows a diameter‐dependent power‐law from nanometer to millimeter scales. Undoped, aligned FWCNT material reaches the intrinsic conductivity of CNT bundles and single‐crystal graphite, illustrating an intrinsic limit requiring doping for copper‐level conductivities. Comparing an assembly of CNTs (forming mesoscopic bundles, then macroscopic material) to an assembly of graphene (forming single‐crystal graphite crystallites, then carbon fiber), the ≈1 µm room‐temperature, phonon‐limited mean‐free‐path shared between graphene, metallic CNTs, and activated semiconducting CNTs is highlighted, deemphasizing all metallic helicities for CNT power transmission applications.

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Section: Extrinsic Characteristicsmentioning

confidence: 99%

A Meta‐Analysis of Conductive and Strong Carbon Nanotube Materials

2021

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“…The experimental data are also in agreement with recent atomistic simulations of monodisperse bundles showing a critical N/d ratio in the range 0.29 -0.5 nm -1 . 37 Note also that an implication from equation ( 4) is that atmospheric pressure has a minor effect on collapse compared to geometric factors of the constituent CNTs and their arrangement in bundles.…”

Section: Flexural Rigidity and Buckling Pressurementioning

confidence: 99%

Identification of Collapsed Carbon Nanotubes in High-Strength Fibers Spun from Compositionally Polydisperse Aerogels

Vila

Hong

Park

et al. 2021

ACS Appl. Nano Mater.

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Carbon Nanotubes (CNTs) of sufficiently large diameter and a few layers self-collapse into flat ribbons at atmospheric pressure, forming bundles of stacked CNTs that maximize packing and thus CNT interaction. Their improved stress transfer by shear makes collapsed CNTs ideal building blocks in macroscopic fibers of CNTs with high-performance longitudinal properties, particularly high tensile properties as reinforcing fibres. This work introduces cross-sectional transmission electron microscopy of FIB-milled samples as a way to univocally identify collapsed 2 CNTs and to determine the full population of different CNTs in macroscopic fibers produced by spinning from floating catalyst chemical vapour deposition. We show that close proximity in bundles is a major driver for collapse and that CNT "stoutness" (number of layers/diameter), which dominates the collapse onset, is controlled by the growth promotor. Despite differences in decomposition route, different C precursors lead to similar distributions of the ratio layers/diameter. The synthesis conditions in this study give a maximum fraction of collapsed CNTs of 70% when using selenium as promotor, corresponding to an average of 0.25 layer/nm.

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“…As thin-walled structures, small diameter CNTs may undergo a transformation from circular to hexagonal cross section at about 1.5-1.7 GPa. 55,56 Therefore, the rigid distinct element model employed here is not fully valid in this regime.…”

Section: Journal Of Applied Physicsmentioning

confidence: 99%

Densification of single-walled carbon nanotube films: Mesoscopic distinct element method simulations and experimental validation

Drozdov

Ostanin

et al. 2020

Journal of Applied Physics

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Nanometer-thin single-walled carbon nanotube (CNT) films collected from the aerosol chemical deposition reactors have gathered attention for their promising applications. Densification of these pristine films provides an important way to manipulate mechanical, electronic, and optical properties. To elucidate the underlying microstructural level restructuring, which is ultimately responsible for the change in properties, we perform large scale vector-based mesoscopic distinct element method simulations in conjunction with electron microscopy and spectroscopic ellipsometry characterization of pristine and densified films by drop-cast volatile liquid processing. Matching with the microscopy observations, pristine CNT films with a finite thickness are modeled as self-assembled CNT networks comprising entangled dendritic bundles with branches extending down to individual CNTs. Simulations of these films under uniaxial compression uncover a soft deformation regime extending up to an ∼75% strain. When removing the loads, the pre-compressed samples evolve into homogeneously densified films with thickness values depending on both the pre-compression level and the sample microstructure. The significant reduction in thickness is attributed to the underlying structural changes occurring at the 100 nm scale, including the zipping of the thinnest dendritic branches.

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Computational Investigation of Large-Diameter Carbon Nanotubes in Bundles for High-Strength Materials

Cited by 10 publications

References 30 publications

A Meta‐Analysis of Conductive and Strong Carbon Nanotube Materials

A Meta‐Analysis of Conductive and Strong Carbon Nanotube Materials

Identification of Collapsed Carbon Nanotubes in High-Strength Fibers Spun from Compositionally Polydisperse Aerogels

Densification of single-walled carbon nanotube films: Mesoscopic distinct element method simulations and experimental validation

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