A peculiar composite structure of carbon nanofibers growing on a microsized tin whisker
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In this work, we report a method to synthesize a peculiar composite structure of tubular carbon nanofibers (CNFs) growing on a microsized tin (Sn) whisker. The material used is a commercially available copper clad laminate (CCL). The CCL is composed of a surface copper (Cu) layer and a bottom polymer (phenol-formaldehyde resin) board, in which the polymer board is used as the carbon source. Using lithography and lift-off techniques, the Cu layer was patterned to a stripelike Cu trace. A Sn thin film was then evaporated on the polymer board near the Cu trace. To release the residue stress that resulted from the evaporation; Sn whiskers with diameters of about 2 to 5 m were formed on the Sn thin film after evaporation. By passing an electric current through the Cu trace, the Cu trace was heated due to Joule heating and served as a heating source for the thermal decomposition of phenol-formaldehyde. After heat treatment, the CNFs grew on the surface of the Sn whiskers with tubular hollow-cored structure. The diameter of the tubular CNFs is about hundreds of nanometers and their length can reach several micrometers. The growth mechanism of the brushlike composite structure is also discussed.
I. INTRODUCTION
Carbon nanostructures, such as carbon nanofibers (CNFs) and carbon nanotubes (CNTs), have attracted great interest during the last few decades because of their distinctive properties and the possibility of applying them in some technological fields such as anode materials of lithium ion batteries,1 biomaterials,2 fuel cells,3 biosensors,4 field emission devices,5 and hydrogenstorage materials.6 Various approaches have been developed to synthesize the one-dimensional (1D) CNFs and CNTs such as arc-discharge7–9 and catalytic decomposition of hydrocarbons.10–12 The catalytic decomposition of hydrocarbons is usually termed as chemical vapor deposition (CVD) and is regarded as a more economic method to synthesize the carbon nanostructures. The synthesized CNFs and CNTs typically have a nanoscale diameter and a length that can grow up to the scale of micrometers. In general, the catalytic decomposition of hydrocarbons uses nanoscale metallic particles as the catalysts and also requires a substrate to support the catalyst particles. The substrates are usually plane and don’t participate in the synthesis of carbon nanostructures. In this
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0326 2668
http://journals.cambridge.org
J. Mater. Res., Vol. 23, No. 10, Oct 2008 Downloaded: 16 Mar 2015
present work, we report a peculiar composite structure of tubular CNFs growing on the surface of a microsized tin (Sn) whisker. The appearance of the composite structure is like a brush. Unlike the regular plane and nonreactive substrates, the Sn whisker is columnlike and is likely to play a role similar to the catalyst. The approach used is simple and can be conducted under an atmospheric condition.
II. EXPERIMENTAL PROCEDURES
Figure 1(a) shows a schematic of a commercially availabl
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