Synthesis of Nanocarbons Using a Large Volume AC Plasma Reactor
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Synthesis of Nanocarbons Using a Large Volume AC Plasma Reactor M. Hamady, D. Sheppard, K. Seddighi, A. Sarawagi, B. Scott, K. Wilcox*, A. Gerber*, L.P.F. Chibante University of New Brunswick, Chemical Engineering (*Mechanical Engineering) 15 Dineen Dr., Fredericton, E3B 5A3, New Brunswick, Canada ABSTRACT There is an opportunity for scaling up, optimizing, and controlling the process of production of nanoparticles due to their numerous diverse applications. We present a system for continuous, high rate production of nanoparticles, particularly those of carbon, using large volume thermal plasma based on a three-phase diverging electrode configuration. The goal of using this 3-phase plasma reactor is to have a plasma arc that is scalable, self-stabilizing, and low maintenance, with sufficient plasma volume to maximize residence time of feed materials for evaporation to atomic species. Plasma carrier gas, typically inert gas such as helium, is injected into the reactor allowing the vaporization of any feedstock due to plasma temperatures >5000 ºC. Controlling plasma enthalpy, diffusion/temperature gradients and carbon feed rates allow the controlled growth of clusters leading to nanoparticles less than 100 nm. Once the desired size is achieved the gas stream is expanded to reduce the reaction rate and quenched by natural cooling to chamber walls or injection of a cooling gas stream, preferably of the same composition as plasma carrier gas. Recoverable yields in the nanoparticle-laden gas stream are then isolated by standard means (filtration, cyclone separation, electrostatic precipitation), and the plasma gas and unreacted feedstock are routed to the plasma reactor for recycling. Computational Fluid Dynamics (CFD) is employed to measure and predict fluid flow, energy/temperature, and other species distributions in the plasma process. INTRODUCTION Carbon is an abundant raw material and as the basis of earth’s ecosystem is the most studied element in the periodic table. Consequently, a very large knowledge base is already in existence to manipulate carbon-based products. Nanocarbons (Figure 1) have moved quickly from a novel laboratory curiosity through rapid characterization and now are nearing commercial application. Due to their interesting properties and high symmetry, they have proven beneficial as precursors for diamond synthesis [1], polymer composites[2], selective catalysis [3], anti-oxidant/ free-radical inhibitors [4], Figure 1. Structure of some allotropes of carbon. solar cells [5], fuel cells or batteries [6], liquid crystal displays (LCD) [7], organic light emitting diodes (OLEDs) [8], even as anti-viral agents against HIV virus [9] among other applications.
Current methods of production of nanocarbons are laser ablation [10], solar ablation [11, 12], combustion of hydrocarbons [13], chemical vapor deposition (CVD) [14] and arc plasma [15, 16]. Though these production techniques appear to be dissimilar methods there are common requirements for nanocarbon formation. These requirements necessary for indu
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