Unusual Properties and Structure of Carbon Nanotubes

Dresselhaus, M. S.; Dresselhaus, G.; Jório, Ado

doi:10.1146/annurev.matsci.34.040203.114607

Cited by 474 publications

(317 citation statements)

References 118 publications

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“…The spectra consist of four well-known and characteristic CNT bands: [35][36][37] 1578 cm -1 (G band, attributed to in-plane C-C symmetric stretching vibrations in graphene sheets), 1335 cm -1 (D band, usually attributed to the presence of disordered carbon, as well as to the structural disorder, such as defective rings, presence of heteroatoms, dangling bond and vacancies, present in the graphene sheet), 2655 cm -1 (G' or 2D band, a second order band that is an overtone of the D band) and a weak shoulder at higher frequencies of the G-band at 1612 cm 13). According to the XRD and TG data previously discussed, these two treatments are more efficient at the removal of amorphous carbon.…”

Section: Resultsmentioning

confidence: 99%

The effect of different chemical treatments on the structure and stability of aqueous dispersion of iron- and iron oxide-filled multi-walled carbon nanotubes

Moraes¹,

Matos²,

Castro³

et al. 2011

J. Braz. Chem. Soc.

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O efeito de cinco diferentes tratamentos químicos (HNO 3 , H 2 SO 4 , H 2 O 2 , HNO 3 + H 2 SO 4 e HNO 3 + HCl) na homogeneidade, superfície, estrutura e dispersabilidade em água de nanotubos de carbono do tipo multi-paredes preenchidos com ferro ou óxido de ferro foi estudado através de difratometria de raios X (XRD), espectroscopias Raman, UV-Visível e fotoeletrônica de raios X (XPS), análise termogravimétrica (TG) e microscopia eletrônica de varredura (MEV). Os resultados indicaram que os tratamentos são efetivos na remoção de espécies carbonáceas diferentes de nanotubos, presentes na amostra. Com exceção do tratamento com H 2 O 2 , uma boa remoção das espécies contendo metal também foi observada. Além de aumentar a homogeneidade das amostras, os tratamentos também criam grupos carboxílicos e hidroxílicos superficiais, que afetam diretamente a dispersabilidade destas espécies em água. Dispersões estáveis de 2,24 × 10 -1 g L -1 de nanotubos em água foram obtidas após o tratamento com mistura de ácido sulfúrico e ácido nítrico.The effect of five different chemical treatments (HNO 3 , H 2 SO 4 , H 2 O 2 , HNO 3 + H 2 SO 4 and HNO 3 + HCl) on the homogeneity, surface chemistry, structure and dispersibility in water of ironand iron oxide-filled multi-walled carbon nanotube samples was evaluated by X-ray diffractometry (XRD), Raman, UV-Visible and X-ray photoelectron (XPS) spectroscopies, thermogravimetric analysis (TG) and scanning electron microscopy (SEM). The results indicate that the chemical treatments are generally effective in removing non-nanotube carbonaceous species present in the sample. With the exception of the H 2 O 2 treatment, the chemical treatments also offer good removal of free iron-species. Besides the increase in the sample homogeneity, the chemical treatments promoted an increase in the carboxyl and hydroxyl groups at the carbon nanotube surface, what directly affects the dispersibility of these carbon nanotubes in water. Dispersions of 2.24 × 10 -1 g L -1were obtained for the treated samples with a mixture of nitric and sulfuric acid. Keywords: carbon nanotubes, chemical treatment, CVD, nanostructures, nanomaterials IntroductionCarbon nanotubes (CNTs) have received much attention in the last years due to their extraordinary chemical and physical properties, arising from the combination of their typical morphology, structure and size.1 Many different processes have been described for the synthesis of CNTs. Among them, one of the most versatile is the catalytic chemical vapor deposition (CVD), which is based on the decomposition of a carbon source (usually a hydrocarbon) over metal nanocatalysts.2 Usually, the resulting samples are a mixture of CNTs and some impurities, such as other carbonaceous materials (graphite, amorphous carbon, fullerenes, carbon nano-structures, etc.) and the catalyst metal particles.3 These impurities are undesirable for a variety of applications, and different physical and/or chemical treatments are usually performed to remove them. 4 However, it should be noted th...

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Section: Resultsmentioning

confidence: 99%

The effect of different chemical treatments on the structure and stability of aqueous dispersion of iron- and iron oxide-filled multi-walled carbon nanotubes

Moraes¹,

Matos²,

Castro³

et al. 2011

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

show abstract

“…The mass ratio is defined as m 2 /m 1 and values of 0.1, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5,6,7,8,9, and 10 are considered. To isolate the effects of the phonon dispersion and mass density on thermal conductivity, we use classical (i.e., Boltzmann) statistics at a temperature of 500 K. Doing so compared to quantum statistics removes the frequency dependence of the specific heat from the thermal conductivity prediction.…”

Section: Methodology a Lattice Dynamics Calculationsmentioning

confidence: 99%

“…[1][2][3][4][5][6][7] For application in thermoelectric energy conversion, many previous studies have focused on how to reduce thermal conductivity. [8][9][10] Phonon scattering increases with increasing anharmonicity and defect concentration, resulting in lower thermal conductivity. In single species (i.e., monatomic) materials, larger atomic mass reduces the phonon group velocities and, thus, thermal conductivity.…”

Section: Introductionmentioning

confidence: 99%

Thermal conductivity of compound semiconductors: Interplay of mass density and acoustic-optical phonon frequency gap

Jain

McGaughey

2014

Journal of Applied Physics

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The thermal conductivities of model compound semiconductors, where the two species differ only in mass, are predicted using lattice dynamics calculations and the Boltzmann transport equation. The thermal conductivity varies non-monotonically with mass ratio, with a maximum value that is four times higher than that of a monatomic semiconductor of the same density. The very high thermal conductivities are attributed to a reduction in the scattering of optical phonons when the acoustic-optical frequency gap in the phonon dispersion approaches the maximum acoustic phonon frequency. The model system predictions compare well to predictions for real compound semiconductors under appropriate scaling, suggesting a universal behavior and a strategy for efficient screening of materials for high thermal conductivity. V C 2014 AIP Publishing LLC.

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“…The bands calculated in the third neighbor ETB model are shown as solid blue lines and the results of the nearest neighbor simple tight-binding model described in [34] are shown as red dash-dotted lines. In a SWNT with chiral indices (n, m), a translational vector T can be found parallel to the tube axis [34,75]. The translational vector is T = t 1 a 1 + t 2 a 2 ≡ (t 1 , t 2 ) where t 1 = (2m + n)/ gcd(2n + m, 2m + n) and t 2 = −(2n + m)/ gcd(2n + m, 2m+n) with gcd(i, j) being the greatest common divisor of two positive integers i and j.…”

Section: Electronic Statesmentioning

confidence: 99%

Theory of coherent phonons in carbon nanotubes and graphene nanoribbons

Sanders

Nugraha

Sato

et al. 2013

J. Phys.: Condens. Matter

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We survey our recent theoretical studies on the generation and detection of coherent radial breathing mode (RBM) phonons in single-walled carbon nanotubes and coherent radial breathing like mode (RBLM) phonons in graphene nanoribbons. We present a microscopic theory for the electronic states, phonon modes, optical matrix elements and electron-phonon interaction matrix elements that allows us to calculate the coherent phonon spectrum. An extended tight-binding (ETB) model has been used for the electronic structure and a valence force field (VFF) model has been used for the phonon modes. The coherent phonon amplitudes satisfy a driven oscillator equation with the driving term depending on the photoexcited carrier density. We discuss the dependence of the coherent phonon spectrum on the nanotube chirality and type, and also on the graphene nanoribbon mod number and class (armchair versus zigzag). We compare these results with a simpler effective mass theory where reasonable agreement with the main features of the coherent phonon spectrum is found. In particular, the effective mass theory helps us to understand the initial phase of the coherent phonon oscillations for a given nanotube chirality and type. We compare these results to two different experiments for nanotubes: (i) micelle suspended tubes and (ii) aligned nanotube films. In the case of graphene nanoribbons, there are no experimental observations to date. We also discuss, based on the evaluation of the electron-phonon interaction matrix elements, the initial phase of the coherent phonon amplitude and its dependence on the chirality and type. Finally, we discuss previously unpublished results for coherent phonon amplitudes in zigzag nanoribbons obtained using an effective mass theory.

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Unusual Properties and Structure of Carbon Nanotubes

Cited by 474 publications

References 118 publications

The effect of different chemical treatments on the structure and stability of aqueous dispersion of iron- and iron oxide-filled multi-walled carbon nanotubes

The effect of different chemical treatments on the structure and stability of aqueous dispersion of iron- and iron oxide-filled multi-walled carbon nanotubes

Thermal conductivity of compound semiconductors: Interplay of mass density and acoustic-optical phonon frequency gap

Theory of coherent phonons in carbon nanotubes and graphene nanoribbons

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