Production Of Single-walled Nanotubes Research Articles

Influence of polarity on filling polymer molecules into carbon nanotubes

Using molecular dynamics (MD) simulation, we studied the influence of polarity of polymer chains and modified single-walled nanotubes (SWNTs) on filling polymer chains into SWNTs. The center of mass (COM) distance and the interaction energy between the polymer molecules and SWNTs, as well as non-bond energy (including van der Waals energy and electrostatics energy) differences (ΔE) between initial structure and final structure in the SWNTs–polymers systems were calculated. The simulations indicate that both the polarity of polymer molecules and the polarity of modified groups attached to SWNTs can obstruct filling polymer chains into SWNTs. The general conclusions may be of importance in the production of high-performance SWNTs–polymers nanocomposites and have important theoretical significance on the application of carbon nanotubes as drug carrier and transportation channels.

Growth model for plasma-CVD growth of carbon nano-tubes on Ni-sheets

The plasma enhanced chemical vapor deposition (PECVD) of carbon nano-tubes (CNT) on nickel sheets is considered as efficient production method of great technologically interest. Different morphologies of CNT on Ni-sheets can be achieved by a variation of the process parameters, like partial pressure of the acetylene and ammoniac inlet gas mixture, the total gas pressure, and temperature. The results are summarized in a detailed growth model based on thermodynamic considerations. The conclusion from this model is that the production of single-wall nano-tubes (SWCNT), which is more desirable than multi wall variants (MWCNT) or graphite nano-fibers (GNF), requires the fastest reaction velocity for CNT formation. The PECVD supports the CNT formation, but for enhancement of the reaction velocity additional inhibitors are required.

Computational fluid dynamics simulation of laser-ablated carbon plume propagation in varying background gases for single-walled nanotube synthesis.

A computational fluid dynamics study was conducted to model the plume resulting from the laser ablation of a carbon target in a laser ablation oven for the production of carbon single-walled nanotubes (SWNTs). The goal is to gain understanding into the fluid dynamics and thermodynamics of the plume to ultimately improve SWNT production techniques. The simulations were carried out with a 12-species, 14-reaction chemistry model that included carbon species from C to C6. Metal catalysts in the carbon target were ignored for these simulations. Simulation times ranged from immediate ablation onset to 8 ms past the initial onset of ablation. A secondary goal of the study was to compare computational results with experimental results for three different background gases in the laser ablation oven-argon, helium, and nitrogen. Computational results indicated that lighter carbon species were more quickly diffused into the background gas for helium and nitrogen, resulting in lower localized mass fractions of carbon nanotube "feedstock." The expectation is that this effect will reduce the production of carbon nanotubes, which has been confirmed by experimental evidence. From this investigation, a possible "indicator species" for the production of SWNT appears to be C5.

Optimization of the Amount of Catalyst and Reaction Time in Single Wall Nanotube Production

Optimization of the Amount of Catalyst and Reaction Time in Single Wall Nanotube Production

Thermodynamic Analysis of Carbon Nucleation on a Metal Surface

AbstractA thermodynamic analysis of the carbon nucleation on the metal surface was performed. From the consideration of the catalytic mechanisms of carbon deposit formation on the metal surface we concluded that majority of these mechanisms include some common steps. The most important of them is the step of nucleation of carbon deposit on the metal surface. The master equation for the dependence of critical radius of the nucleus on reaction parameters was obtained. This equation demonstrates that a variation of the reaction parameters, such as the temperature, the nature of metal catalyst and the degree of supersaturation of the metal-carbon solution, can lead to the formation of different carbon deposits, such as filamentous carbon, multi-wall nanotubes (MWNT) or single-wall nanotubes (SWNT). The analysis performed allows us to conclude that for selective production of SWNT the nucleation must proceed at high temperature on the surface of liquid metal particles (Fe, Co, Ni). For solid metal particles (Mo) a high degree of supersaturation with carbon is also required.

Controlled production of single-wall carbon nanotubes by catalytic decomposition of CO on bimetallic Co–Mo catalysts

The term `controlled production' of single-wall nanotubes (SWNT) implies the ability to control the selectivity towards SWNT by changing catalyst formulations and operating conditions, combined with a quantitative measurement of the SWNT obtained. In this contribution, a significant advancement towards the controlled production of SWNT is reported. A family of Co–Mo catalysts has been found to be able to produce SWNT with high selectivity, depending on the Co:Mo ratio, the temperature of operation, and the processing time. The optimization of the catalyst was possible by the application of a simple and direct method of quantification of the SWNT production.