Defect-dependent annealing behavior of multi-walled carbon nanotubes

Bhalerao, G. M.; Sinha, A. K.; Sathe, V. G.

doi:10.1016/j.physe.2008.06.006

Cited by 26 publications

(20 citation statements)

References 14 publications

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“…The difference in thermal stabilities between CNTs under inert conditions may be explained by the defect density rather than the abundance of oxygenated functional groups or metal oxides. MWCNTs produced by CVD will generate additional defects when heated under inert conditions until a limiting temperature is reached, at which point the defects begin to heal [33]. If this temperature is not reached, then defects may continue to develop.…”

Section: Resultsmentioning

confidence: 99%

Detection of Carbon Nanotubes in Environmental Matrices Using Programmed Thermal Analysis

Doudrick

Herckès

Westerhoff³

2012

Environ. Sci. Technol.

102

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Carbon nanotube (CNT) production is rapidly growing, and there is a need for robust analytical methods to quantify CNTs at environmentally relevant concentrations in complex organic matrices. Because physical and thermal properties vary among different types of CNTs, we studied 14 single-walled (SWCNTs) and multiwalled CNTs (MWCNTs). Our aim was to apply a classic analytical air pollution method for separating organic (OC) and elemental carbon (EC) (thermal optical transmittance/reflectance, TOT/R) to environmental and biological matrices and CNTs. The TOT/R method required significant modification for this analysis, which required a better understanding of the thermal properties of CNTs. An evaluation of the thermal properties of CNTs revealed two classes that could be differentiated using Raman spectroscopy: thermally “weak” and “strong.” Using the programmed thermal analysis (PTA) method, we optimized temperature programs and instituted a set of rules for defining the separation of OC and EC to quantify a broad range of CNTs. The combined Raman/PTA method was demonstrated using two environmentally relevant matrices (cyanobacteria (CB) and urban air). Thermal evaluation of CB revealed it to be a complex matrix with interference occurring for both weak and strong CNTs, and thus a pretreatment method was necessary. Strong CNT masses of 0.51, 2.7, and 11 µg, corresponding to concentrations of 10, 54, and 220 µg CNT/g CB, yielded recoveries of 160 ± 29%, 99 ± 1.9%, and 96 ± 3.0%, respectively. Urban air was also a complex matrix and contained a significant amount (12%) of background EC that interfered with greatly weak CNTs and minimally with strong CNTs. The current detection limit at 99% confidence for urban air samples and strong CNTs is 55 ng/m3 (0.33 µg). Overall, the PTA method presented here provides an initial approach for quantifying a wide range of CNTs, and we identify specific future research needs to eliminate potential interferences and lower detection limits.

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Section: Resultsmentioning

confidence: 99%

Detection of Carbon Nanotubes in Environmental Matrices Using Programmed Thermal Analysis

Doudrick

Herckès

Westerhoff³

2012

Environ. Sci. Technol.

102

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“…[41] Recently, Raman spectroscopy has been exploited to investigate even the mechanical and electrical properties of CNT-based elastomers. [6] In another recent study defect-dependent annealing behavior of MWCNTs was studied by Bhalerao et al, [42] where I D /I G was used as an important parameter to examine the effect of annealing. The annealing of MWCNTs was carried out in hydrogen atmosphere at temperatures <1300 • C. Thus, it appears that I D /I G has been used for studying many different properties of SWCNTs and MWCNTs.…”

Section: Disorder and Purity Of The Carbonaceous Materialsmentioning

confidence: 99%

Characterization of carbon nanotube filters and other carbonaceous materials by Raman spectroscopy—II: study on dispersion and disorder parameters

Heise

Kuckuk

Srivastava

et al. 2011

J Raman Spectroscopy

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Recently, we have reported on the characterization of various carbonaceous materials including multiwalled carbon nanotube (MWCNT) filters, which have specific molecular filtering capabilities and good mechanical strength and can be produced in bulk as highly aligned arrays of bundles of CNTs. We have extended our studies using Fourier transform-Raman spectroscopy with 1064 nm excitation wavelength and a rotating sample holder in the region 1000-2800 cm −1 , in addition to 532 and 785 nm, which were used for Raman excitation in our previous study. Raman spectra were analyzed for band positions and line shape with special emphasis on the D-, G-and G -bands. For the single-walled species, Carbotrap and graphite spectra were also recorded with 488 nm excitation. A dispersion study has been made from the Raman data available with the different excitation wavelengths. Slight band shifts and band broadening could be observed under the two sample conditions, one with the stationary sample and the other with sample rotation. The spectral changes are related to the excessive heating caused in a stationary sample by laser irradiation. Based on our findings in this study combined with our earlier study, we can state that only a careful line shape analysis and study of intensity pattern of the D-and G-Raman bands under well-defined measurement conditions lends itself as a good measure of degree of alignment in the MWCNT bundles.

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“…There are many methods to produce CNTs among which CNTs grown by chemical vapour deposition (CVD) have higher defect density compared with CNTs synthesised by arc discharge and laser ablation methods [32]. Defects can also be introduced after growth of CNTs by different methods such as milling [33], oxidation [34], nitric acid treatment [31], potassium hydroxide treatment [35], plasma etching [36] and irradiation [37].…”

Section: Effect Of Defects On Hydrogen Storage Properties Of Carbon Nmentioning

confidence: 99%

“…Defects can also be introduced after growth of CNTs by different methods such as milling [33], oxidation [34], nitric acid treatment [31], potassium hydroxide treatment [35], plasma etching [36] and irradiation [37]. During heat-treatment of pristine CNTs, both defect generation and defect annealing processes take place [32].…”

Section: Effect Of Defects On Hydrogen Storage Properties Of Carbon Nmentioning

confidence: 99%

Relationship between microstructure and hydrogen storage properties of nanomaterials

Gubicza¹

2012

Defect Structure in Nanomaterials

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The infl uence of particle size, crystallite size and lattice defects on hydrogen storage capacity and absorptiondesorption kinetics of nanostructured materials is overviewed. It is shown that the particle and crystallite sizes, and catalyst play two different roles in the sorption process. By decreasing the particle and crystallite sizes, the required diffusion path of hydrogen is drastically reduced, which enhances the sorption kinetics signifi cantly. At the same time, catalysts have a promoting effect on dissociation or recombination of hydrogen molecules on the particles' surfaces and they also act as chemisorption sites. The lattice defects (dislocations, stacking faults and twin boundaries) facilitate the diffusion of hydrogen and the nucleation of hydride phases. It is revealed that large amounts of dislocations and/or planar faults are formed due to stresses induced by phase transformations in hydrogenation and dehydrogenation processes. The effect of defects on hydrogen storage capacity of carbon nanotubes is also reviewed.

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Defect-dependent annealing behavior of multi-walled carbon nanotubes

Cited by 26 publications

References 14 publications

Detection of Carbon Nanotubes in Environmental Matrices Using Programmed Thermal Analysis

Detection of Carbon Nanotubes in Environmental Matrices Using Programmed Thermal Analysis

Characterization of carbon nanotube filters and other carbonaceous materials by Raman spectroscopy—II: study on dispersion and disorder parameters

Relationship between microstructure and hydrogen storage properties of nanomaterials

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