Catalyst Poisoning by Amorphous Carbon during Carbon Nanotube Growth: Fact or Fiction?

Schünemann, Christoph; Schäffel, Franziska; Bachmatiuk, Alicja; Queitsch, Ute; Sparing, Maria; Rellinghaus, Bernd; Lafdi, Khalid; Schultz, L.; Büchner, B.; Rümmeli, Mark H.

doi:10.1021/nn2031066

Cited by 37 publications

(32 citation statements)

References 30 publications

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“…, the average CNT diameter is separated in a step function manner into two prominent temperature regimes (680–800 °C and 820–900 °C), which has never been observed due to the lack of wide temperature ranges from previous studies. The transition step in between is indicated by a dramatic diameter increase of ∼25 nm, which correlated well with data presented by Schünemann et al . While the SEM analysis shows the structural properties exhibiting a clear change at ∼800 °C, SEM has limited accuracy at the nanometer length scale, so a TEM analysis of the structural properties was also performed (as shown in Figs.…”

Section: Resultssupporting

confidence: 88%

“…The formation of non‐crystalline carbon particles at elevated temperature can be explained by excessive pyrolysis. Aside from a‐C conglomerates on top of CNT arrays, several previous investigations report that such high rate of hydrocarbon decomposition also results in forming amorphous coatings around the surface of individual CNTs, rapidly increasing the nanotube diameters . Our side‐view Raman spectroscopy (Fig.…”

Section: Resultsmentioning

confidence: 80%

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Effect of growth temperature on the synthesis of carbon nanotube arrays and amorphous carbon for thermal applications

Pham

Larkin

Lisboa

et al. 2017

Physica Status Solidi (a)

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Phone/Fax: þ86 10 623 32743Though carbon nanotube (CNT) arrays have tremendous potential due to their attractive mechanical, electrical, and thermal properties, the growth kinetics of CNTs are still not fully understood. Thus, we report on the effect of synthesis parameters, such as growth temperature, on the resulting arrays. In this work, CNT arrays were synthesized using catalytic chemical vapor deposition (CCVD) with furnace temperatures varying from 680 to 900 8C. Microscopy was used to investigate the effect of growth temperature on the structural properties, such as tube diameter, array length, and the amount of amorphous carbon produced at the top of the canopy as a growth by-product. Additionally, Raman spectroscopy was used to elucidate the effect growth temperature has on the resulting purity of the CNTs. It was then revealed that crystalline inhomogeneity exists along the length of the tubes with respect to crystallinity. Transmission electron microscopy (TEM) further determines the degree of tube crystallinity as well as the thickness of amorphous carbon coating around the nanotubes. Through both microscopy and spectroscopy, we found two distinct temperature regimes within the range of 680-900 8C. Below 800 8C, the growth of tube length and diameter remained relatively stagnant followed by a rapid growth rate above 800 8C with the highest tube crystallinity obtained within the regime of 800-840 8C. This indicates the presence of an important transitional temperature for CNT CCVD growth. Additionally, growth temperature was determined to play an important role in the amount of the resulting amorphous carbon by-product.

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Section: Resultssupporting

confidence: 88%

Section: Resultsmentioning

confidence: 80%

Effect of growth temperature on the synthesis of carbon nanotube arrays and amorphous carbon for thermal applications

Pham

Larkin

Lisboa

et al. 2017

Physica Status Solidi (a)

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“…The dark part corresponds to the graphene layers. The last layer located on the surface of the fibers, corresponds to an ultrathin amorphous carbon coating (Figure A), deposited during the synthesis of CNFs . Figure B shows the photograph of pCNFs with the irregular polyethylene layer on its surface as compared with the smoother surface of CNFs (Figure A).…”

Section: Resultsmentioning

confidence: 99%

Nanocomposites Prepared with High Density Polyethylene and Carbon Nanofibers Modified by Ethylene Plasma

Neira‐Velázquez

Borjas‐Ramos

Hernández‐Hernández³

et al. 2015

Plasma Processes & Polymers

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Carbon nanofibers (CNFs) are surface-modified by plasma polymerization using ethylene as monomer. The modified CNFs are suitable to be mixed with different polyethylenes. In this study, we mix them with high density polyethylene (HDPE). The plasma-coated CNFs (pCNFs) are then characterized by Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM) in the transmission mode (STEM). Treated and untreated CNFs are evaluated in water, chloroform, and 1,2,3-trichlorobenzene (TCB) to evaluate their effective dispersion in these three solvents. FTIR spectra showed signals corresponding to the organic part deposited on the surface of pCNFs. The TGA analysis makes it possible to confirm that pCNFs have a higher weight loss than CNFs because of the volatilization of the plasma polymerized ethylene coating. Dispersion tests showed that pCNFs dispersed well in TCB and chloroform solvents. To prepare nanocomposites, HDPE and CNFs are mixed well in a single-screw extruder with an attached sonication chamber at its exit. Nanocomposites containing 1% and 3% by weight of CNFs are prepared. The products are analyzed by the Young's modulus and evaluated for thermal stability.

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“…On the other hand, the vapor-liquid-solid (VLS) mechanism 12 and solution-liquid-solid (SLS) mechanism 13 are two typical growth mechanisms of one-dimensional nanostructures on the liquid-solid interface, which have been widely applied to guide the growth of zinc (Zn) oxide nanowires 14 15 , carbon nanotubes 16 17 , nanowires of elemental semiconductors 18 19 and compound semiconductors 20 21 etc. However, appropriate catalysts and high reaction temperature are required in these growth processes.…”

mentioning

confidence: 99%

One-dimensional Growth of Zinc Crystals on a Liquid Surface

Cheng

Pan

et al. 2016

Sci Rep

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The catalyst-free growth of nanocrystals on various substrates at room temperature has been a long-standing goal in the development of material science. We report the growth of one-dimensional zinc nanocrystals on silicone oil surfaces by thermal evaporation method at room temperature (20 ± 2 °C). Uniform zinc nanorods with tunable size can be obtained. The typical length and width of the nanorods are 250–500 nm and 20–40 nm, respectively. The growth mechanism can be attributed to the effect of the liquid substrate and the preferential growth direction of the crystals. This result provides a novel and simple way to fabricate the precursors (zinc crystals) for preparation of Zn-based semiconductors and other metallic crystals on liquid substrates.

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Catalyst Poisoning by Amorphous Carbon during Carbon Nanotube Growth: Fact or Fiction?

Cited by 37 publications

References 30 publications

Effect of growth temperature on the synthesis of carbon nanotube arrays and amorphous carbon for thermal applications

Effect of growth temperature on the synthesis of carbon nanotube arrays and amorphous carbon for thermal applications

Nanocomposites Prepared with High Density Polyethylene and Carbon Nanofibers Modified by Ethylene Plasma

One-dimensional Growth of Zinc Crystals on a Liquid Surface

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