Microstructural changes in carbon nanotubes induced by annealing at high pressure

“…Similar rearrangements have been reported by other groups. 18,19 The carbon K-edge spectra reveal differences that do not appear in the images, as shown in Fig. 2͑a͒.…”

mentioning

confidence: 97%

Transmission electron energy-loss spectroscopy study of carbon nanotubes upon high temperature treatment

Reed

Sarıkaya

Dalton

et al. 2001

Applied Physics Letters

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Two batches of carbon nanotube materials, grown with a pulsed-laser deposition technique but purified and heat treated under different conditions, are investigated with a combination of high- resolution transmission electron microscopy techniques, including electron nanodiffraction and low-loss and carbon K-edge electron energy-loss spectroscopy. These techniques were used to achieve a detailed profile of each material. Heat treating one batch at 1100 °C is shown to increase the sp2/sp3 hybridization ratio, while a 2150 °C treatment of the other batch fundamentally restructured the material from single walled to a mixture of amorphous and multiwalled material.

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Molecular “Glass” Blowing: From Carbon Nanotubes to Carbon Nanobulbs

Zhu

Schlögl³

et al. 2004

Advanced Materials

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rial has been developed based upon density-functional simulations rather than trial-and-error preparation procedures. In addition, we also expect that materials with N sp above 4.25 will also be good PC materials. This is in excellent agreement with the data compiled in Table 1. In this table we have collected all known phase-change alloys that show good properties in rewritable optical data storage (successful samples') and also two samples that are not suitable. Consistent with the arguments presented above we note from Table 1 that the N sp of successful PC materials is always larger than 4, and usually between 4.3 and 5. From Figure 3, we estimate that the critical value of N sp that distinguishes the rocksalt and the chalcopyrite structures is about 4.1.In summary, the DFT calculations presented here help to identify new and possibly superior phase-change materials. All phase-change materials reported are characterized by a cubic or near-cubic coordination, which is caused by the dominance of the p-electron bonding. The average number of valence electrons plays the crucial role in determining the structure of the semiconductor alloys studied here. For N sp = 4, we find that the stable structure of (Cu,Ag,Au)InTe 2 is the chalcopyrite phase with sp 3 -bonding, while for N sp = 4.5, the stable structure of (Cu,Ag,Au)SbTe 2 ternary alloys is the rocksalt structure with p-bonding. Results show that Te-based ternary materials will favor the suitable rocksalt structure if their N sp is bigger than 4.1. This simple criterion facilitates the search for new phase-change materials and opens the way to a more fundamental understanding of phase-change materials.

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Microstructural changes in carbon nanotubes induced by annealing at high pressure

Cited by 12 publications

References 27 publications

Carbon Nanotubes: Synthesis, Properties, and Applications

Carbon Nanotubes: Synthesis, Properties, and Applications

Transmission electron energy-loss spectroscopy study of carbon nanotubes upon high temperature treatment

Molecular “Glass” Blowing: From Carbon Nanotubes to Carbon Nanobulbs

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