Effect of a Metallocene Catalyst Mixture on CNT Yield Using the FC-CVD Process

Abstract

This work studies synthesis of carbon nanotube (CNT) sheet using the high temperature (1400 °C) floating catalyst chemical vapor deposition (FC-CVD) method. Three metallocenes—ferrocene, nickelocene, cobaltocene—and their combinations are used as precursors for metal catalysts in the synthesis process. For the carbon source, an alcohol fuel, a combination of methanol and n-hexane (9:1), is used. First, the metallocenes were dissolved in the alcohol fuel. Then, the fuel mixture was injected into a tube furnace using an ultrasonic atomizer with Ar/H2 carrier gas in a ratio of about 12/1. The synthesis of CNTs from a combination of two or three metallocenes reduces the percentage of metal catalyst impurity in the CNT sheet. However, there is an increase in structural defects in the CNTs when using mixtures of two or three metallocenes as catalysts. Furthermore, the specific electrical conductivity of the CNT sheet was highest when using a mixture of ferrocene and cobaltocene as the catalyst. Overall, the multi-catalyst method described enables tailoring certain properties of the CNT sheet. However, the standard ferrocene catalyst seems most appropriate for large-scale manufacturing at the lowest cost.

Insights into the Nucleation and Structure of Lignin-Based Carbon Nanotubes Synthesized Using Iron via Floating Catalyst Chemical Vapor Deposition

“…These carbon atoms first deposited on the surface of catalyst Fe particles and then precipitated and assembled into CNTs. 22,27 S atoms can reduce the potential energy of C atoms precipitating on the surface of catalyst Fe particles, accelerating the synthesis rate of CNTs. 28 Because Fe atoms will randomly fuse at high temperature, Fe particles often present different sizes and shapes.…”

“…8,21 Second, introducing catalysts inevitably leaves residual Fe in the final product, adversely impacting the structure, conductivity, and other properties of the nanotubes. 22 Therefore, understanding the effects of catalyst content and micromorphology on nanotube growth, structure, and performance, as well as efficient production of high-purity nanotubes, is very necessary and meaningful.…”

Carbon Hybrid Materials—Design, Manufacturing, and Applications

“…A modified gas phase pyrolysis (floating catalyst) method is used to perform the synthesis of CNT fabric. The synthesis for the horizontal floating catalyst method has been described in our previous article [ 2 , 31 ]. The fuel mixture consists of a 9:1 methanol (Sigma Aldrich, St. Louis, MO, USA, 99.8%) and hexane (Fisher Scientific, Waltham, MA, USA, 95%) mixture, 1% ferrocene (Sigma Aldrich, St. Louis, MO, USA, 98%), and 0.3% thiophene (Sigma Aldrich, St. Louis, MO, USA, 99%) mixed via a sonicator.…”

“…Carbon nanotubes are manufactured in various methods; however, chemical vapor deposition (CVD) is the most common way of synthesizing CNTs [ 1 , 2 ]. The floating catalyst CVD method can produce CNTs > 1 mm long.…”

Carbon-based electrically conductive materials for bone repair and regeneration

“…74 Currently, the most affordable and scalable technique to produce CNTs is using chemical vapor deposition (CVD), during which a gaseous carbon precursor is thermally decomposed in the presence of metal catalysts and subsequently deposited inside a nanostructured tubing. 75,76 The scalability of this approach ensures the use of carbon-based materials and remains an attractive avenue in clinical-scale production. However, it is not the only method through which CNTs can be produced.…”