Kinetics of Carbon Nanotubes and Graphene Growth on Iron and Steel: Evidencing the Mechanisms of Carbon Formation.

Luís Sousa Lobo,Sónia A C Carabineiro

doi:10.3390/nano11010143

Luís Sousa Lobo, Sónia A C Carabineiro

Open Access

https://doi.org/10.3390/nano11010143

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Abstract

Carbon formation on steel has recently become an active research area with several important applications, using either carbon nanotubes (CNTs) or graphene structures. The production of vertically aligned CNT (VACNT) forests with combined metals has been explored with important results. Detailed kinetics is the best approach to understand a mechanism. The growth behavior seems complex but can be simplified through the knowledge of the three more common alternative reaction mechanisms/routes. The time required to optimize the production and properties might be reduced. The mechanistic proposal reported in 1971 was better explained recently. The volcano shape Arrhenius plot reported is observed only when Fe, Co, and Ni are used as reaction catalysts. Other metals are catalytically active at higher temperatures, following a different route, which does not require surface catalysis decomposition of the reactive gas. C2H2 and low olefins react well, but CH4 is not reactive via this surface catalysis route. Optimizing production of CNTs, research work is usually based on previous experience, but solid-state science-based studies are available.

Highlights

Carbon formation has become an active research area, since 1990
Co are of particular interest up to 600 ◦ C and Fe up to 650 ◦ C, because they are active in surface catalysis of C2 H2 and low olefins, their (111) surfaces being the most active above those temperatures
The route operating below the temperature of surface catalysis is the same as at higher temperatures, but an alternative carbon growth route (“alternative mechanism”) operates with most transition metals

Summary

Introduction

Carbon formation has become an active research area, since 1990. Ni and. The route operating below the temperature of surface catalysis is the same as at higher temperatures, but an alternative carbon growth route (“alternative mechanism”) operates with most transition metals. In this case, the role of the metal is just to allow interstitial carbon atoms diffusion, dissolving in the side of the nanoparticles and nucleating and growing CNTs on the opposite side. The kinetics and alternative mechanisms of carbon formation have been recently revised by Lobo (check Figure 1) [5]. Detailed reviews on studies of carbon formation from gases in the period 1930–1965 are available, which are very useful to get information on the experimental behavior observed and on possible mechanisms operating [1,2,6].

Arrhenius

Recent Experimental Work

Explanation

Role of Solid-State Chemistry in CNTs Growth Mechanism

CNTs Application Areas

Conclusions