Novel synthesis route to graphene using iron nanoparticles
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Tsengming Chou Department of Chemical Engineering and Materials Science, Laboratory for Multiscale Imaging, Stevens Institute of Technology, Hoboken, New Jersey 07030, USA
Zafar Iqbal Department of Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, New Jersey 07102, USA (Received 2 January 2014; accepted 20 June 2014)
Graphene is currently one of the most extensively studied materials because it displays a number of unique structural and electronic properties. A variety of methods are currently available for the growth of graphene; however, few are viable for large scale, cost-effective production of high quality graphene. Here, a novel growth process for few layer graphene using chemical vapor deposition (CVD) and a commercial iron nanopowder catalyst is described. This method is readily scalable so it can be used to produce a large volume of graphene sheets. Graphene sheets made from this process were characterized by Raman spectroscopy, and scanning and transmission electron microscopy. Raman spectroscopy shows that the product consists of few layer graphene sheets. This is the first reported method of utilizing nanoparticles to synthesize graphene by a CVD process, which typically produces multiwalled carbon nanotubes. A possible mechanism for the formation of graphene by this modified CVD process is discussed. I. INTRODUCTION
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.165
multiwalled carbon nanotubes. Nickel particles were previously utilized as a catalyst to grow graphene, but the process used micrometer (generally ,30 lm)-sized particles. This resulted in large area graphene sheets, but overall yields were low.4 Copper and nickel are typically the catalytic metals of choice to grow graphene,5–8 although iron has been widely used as a catalyst for the growth of related carbon nanostructures such as carbon nanotubes, and iron films have been shown to grow graphene.9,10 If iron is used both as a matrix and catalyst to form metal–graphene nanocomposites, a number of structural applications become possible. This is because iron and steel have great intrinsic mechanical strength, especially when they have a particle size in the nanoscale regime.11 Iron also easily connects carbon structures that could form hierarchical architectures and arrays.12–15 However, since carbon is more soluble in iron than in copper, single layer graphene may be more difficult to grow on iron, but strong iron–carbon bonds would lead to high strength metal–graphene nanocomposites. The CVD growth of graphene on spherical nanoparticles of transition metals would be unlikely to occur because this would typically result in the formation of amorphous carbon or carbon nanotubes.12–16 Theoretically, there are two possible pathways for the formation of graphene on spherical nanoparticles. One is a ‘flower’based model, and the other is a ‘wall’-based model. The flower-based model would involve layers of carbon encircling the iron catalyst particles, and once a critical
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