Catalyst Composition, Morphology and Reaction Pathway in the Growth of “Super‐Long” Carbon Nanotubes

Joshi, Ravi; Engstler, Jörg; Houben, Lothar; Bar‐Sadan, Maya; Weidenkaff, Anke; Mandaliev, Peter; Issanin, Alexander; Schneider, Jörg J.

doi:10.1002/cctc.201000037

Cited by 34 publications

(34 citation statements)

References 33 publications

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“…The growth conditions (gas flow, heating and cooling rate, water flow, etc.) are described in [31][32][33]. TEM did not show deposition of amorphous carbon on the walls of the as-grown CNTs (Fig.…”

Section: Synthesis and Purity Of The Vacnt Arraysmentioning

confidence: 84%

Tribological properties of vertically aligned carbon nanotube arrays

Schaber

Heinlein

Keeley

et al. 2015

Carbon

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Section: Synthesis and Purity Of The Vacnt Arraysmentioning

confidence: 84%

Tribological properties of vertically aligned carbon nanotube arrays

Schaber

Heinlein

Keeley

et al. 2015

Carbon

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“…15 Wellcontrolled amounts of water vapor were introduced into the system by blowing a small amount of gas through a water bubbler by means of a water sensor ͑Michell Instruments͒. Al and Fe react together to produce bimetallic catalyst nanoparticles, which then catalyze the CNT growth.…”

Section: A Growth Of Cnt Blocksmentioning

confidence: 99%

Pronounced field emission from vertically aligned carbon nanotube blocks and bundles

Yilmazoglu

Joshi

Popp

et al. 2011

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Field emission from aligned carbon nanotube ͑CNT͒ blocks and bundles grown by two different chemical vapor deposition ͑CVD͒ methods were investigated. A single CNT block consists of about 1600 double-walled nanotubes per m 2 of area with an intertube distance in the range 15-20 nm, while a bundle consists of a few multiwalled CNTs, which contact each other in the tip region. Hydrogen/water assisted catalytic CVD on a silicon wafer resulted in ultrahigh aspect ratios for the CNT blocks with extremely high field enhancement coefficients Ͼ11 000, a turn-on field of 0.36 V / m, and good field emission stability. The water and hydrogen concentration ratio were found to be a critical parameter for establishing high quality, ultralong ͑up to 2 mm͒ CNT growth. The second CVD growth method used was a noncatalytic template assisted technique for bundle generation. Special self-organized anodic alumina films controlled the synthesis of highly aligned carbon nanotube arrays with the desired tube geometry and adjustable intertube distances. The CNT bundle generation was adjusted by the CNT tube diameter, wall thickness, and length-controlled growth. Subsequent etching of the Al 2 O 3 template resulted in substrateless flexible CNT bundles permitting simple gate electrode integration process. Field emission tests showed that the field enhancement factor, turn-on field, and field emission current density of the CNT cathode arrays could be optimized by adjusting the block or bundle distance. The authors obtained, for the block emitter, a smaller turn-on field and better stability. The block emitter with the better performance was additionally coated with CVD grown ZnO nanoparticles to obtain further improvement. The ZnO nanoparticle diameter was in the range of 15-20 nm. First results showed partial clustering of the ZnO particles suggesting the need for further optimization of the deposition.

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“…Insufficient hydrogen causes the oxidized catalyst Fe to be reduced incompletely, while excessive hydrogen converted the carbon production in the gas phase into the reagents, thus decreasing the overall driving force of the process [41]. Joshi et al [37,42,43] experimentally observed the role of water and hydrogen in terms of their influence on CNT growth, and point out that hydrogen controls the cracking of the carbon precursor ethylene, thereby controlling the purity as well as the number of walls of the CNTs grown. Schaber et al [44,45] investigated the tribological properties of densely-packed VACNTs and the morphology effect on the frictional coefficients.…”

Section: Introductionmentioning

confidence: 99%

Effect of Hydrogen Concentration on the Growth of Carbon Nanotube Arrays for Gecko-Inspired Adhesive Applications

Duan

et al. 2017

Coatings

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Vertically-aligned carbon nanotubes (VACNTs) have extraordinary structural and mechanical properties, and have been considered as potential candidates for creating dry adhesives inspired by adhesive structures in nature. Catalytic chemical vapor deposition is widely used to grow VACNTs; however, the influential mechanism of VACNT preparation parameters (such as H 2 concentration) on its adhesion property is not clear, making accurate control over the structure of VACNTs adhesive an ongoing challenge. In this article, we use electron beam-deposited SiO 2 /Al 2 O 3 as a support layer, Fe as catalyst, and C 2 H 4 /H 2 gas mixtures as a feed gas to prepare VACNTs, while varying the ratio of the reducing atmosphere (H 2 ) from 0% to 35%. VACNTs synthesized at a 15% H 2 concentration (5 mm × 5 mm in size) can support a maximal weight of 856 g, which indicates a macroscopic shear adhesive strength of 34 N/cm 2 . We propose a hydrogen-concentration-dependent model for the shear adhesive performance of VACNTs. By adjusting the amount of hydrogen present during the reaction, the morphology and quality of the prepared VACNTs can be precisely controlled, which significantly influences its shear adhesive performance. These results are advantageous for the application of carbon nanotubes as dry adhesives.

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Catalyst Composition, Morphology and Reaction Pathway in the Growth of “Super‐Long” Carbon Nanotubes

Cited by 34 publications

References 33 publications

Tribological properties of vertically aligned carbon nanotube arrays

Tribological properties of vertically aligned carbon nanotube arrays

Pronounced field emission from vertically aligned carbon nanotube blocks and bundles

Effect of Hydrogen Concentration on the Growth of Carbon Nanotube Arrays for Gecko-Inspired Adhesive Applications

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