Electrodeposition of Ni Catalyst on Tungsten Substrates and Its Effect on the Formation of Carbon Nano- and Micro-coils
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Electrodeposition of Ni Catalyst on Tungsten Substrates and Its Effect on the Formation of Carbon Nano- and Micro-coils Erik Einarsson, Jun Jiao, Josie Prado1 , George M. Coia 2 , Jeremy Petty, and Logan Love Department of Physics, Portland State University Portland, Oregon 97207, U.S.A. 1 Department of Chemical Engineering, Oregon State University Corvallis, Oregon 97331, U.S.A. 2 Department of Chemistry, Portland State University Portland, Oregon 97207, U.S.A. ABSTRACT Carbon micro-coils and nano-coils were produced in high yield from nickel catalyst particles electrochemically deposited onto tungsten substrates. Various electrochemical deposition techniques were used to produce the nickel catalyst particles. These particles catalyzed the chemical vapor deposition (CVD) of acetylene at 800°C, resulting in growth of carbon microand nano-coils. Linear-sweep (cyclic) voltammetry produced catalyst particles which resulted in single- filament coils intermixed with thin nanotubes over most of the substrate surface. Passing the same amount of charge by constant current electrolysis produced nickel particles that decomposed carbon but did not grow coils. Catalyst particles deposited by constant current electrolysis grew nanocoils similar to linear-sweep voltammetry but in small, localized, highyield patches. The coils produced were either spring- like micro-coils of low pitch and large diameter or rope- like nano-coils of higher pitch and smaller diameter. High-resolution transmission electron microscopy (HRTEM) showed typical graphite fringes in the filaments, but did not reveal an internal tubular structure. Catalyst particles were often detected at the ends of the coils. INTRODUCTION Their uniqueness and interesting properties have prompted many researchers to investigate carbon coils [1-4]. Not unlike other carbon micro- and nano-structures, carbon coils have many potential applications such as micro-springs, micro-sensors, magnetic beam generators, and electromagnetic shielding materials [5]. For some applications the substrate on which these coils are grown would play an important role. Tungsten is a very practical substrate because of its strength, high melting point, and use as a high-performance material. Various catalyst-substrate combinations have been used to grow carbon micro- and nano-coils, but we are the first to produce carbon coils from nickel catalyst electrochemically deposited onto tungsten. In this research, the effects of various electrochemical techniques used to deposit nickel onto tungsten substrates were investigated. EXPERIMENT Nickel (Ni) catalyst particles were electrochemically deposited onto tungsten (W) by three different electrochemical deposition techniq ues: linear-sweep voltammetry, constant current
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electrolysis, and constant potential electrolysis. The electrolyte solution was 1.0 M in NaCl, 1.0 M in NH4 Cl, and 10 mM in Ni(NO3 )2 ·6H2O, and was basified to pH 8.3 by addition of concentrated NH4 OH [6]. A three-compartment glass electrochemical cell was used, and t
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