Synthèse de nanostructures de carbone en utilisant un réacteur à plasma d'induction à haute fréquence
Fullerenes and nanotubes are new forms of carbon nanostructures that have exhibited important physical and chemical properties with a wide range of future applications such as in nanoelectronic, optic and medicine. The work presented here is focused on the investigation of the synthesis of carbon nanostructures. The main objectives of this research are: (1) to explore the induction plasma technology to in-continuous synthesize carbon nanostructures, and (2) to predict fullerene formation throughout theoretical studies. The methodology used in the experimental design is based on the vaporization of carbon-bearing reactants followed by the condensation of the carbon gas. The experimental apparatus consisted of a continuous flow type reactor equipped with a high frequency plasma torch operated at 3 MHz. Theoretical thermodynamic studies were carried out to predict the equilibrium composition of fullerenes at several operating conditions. These studies involved the more recent thermodynamic data reported on fullerenes. Additionally, a new kinetic approach was used to evaluate the chemical kinetics behavior of the carbon species involved in the formation mechanism of fullerenes. This approach considers fullerene growth by a sequential addition of C[subscript 2] and C[subscript 3] molecules. A series of preliminary experimental tests were conducted to evaluate the process ability to produce fullerenes. In these tests acetylene (C[subscript 2]H[subscript 2] ), tetrachloroethylene (C[subscript 2]Cl[subscript 4]) and carbon black (CB) were used as carbon source and iron (Fe), nickel (Ni) and yttrium (Y) as catalyst. Additionally, a complete statistical factorial design with four factors at two levels was also developed. This design studied the effect of the system operating parameters on the C 60 fullerene yield. The operating parameters involved in the study were: (1) reactor pressure (40 and 66 kPa), (2) plate power (20 and 40 kW), (3) carbon-bearing ratio (2 and 4%mol) and (4) raw material feed rate (2 and 4 g/min). In this study, mixtures of CB-Ni were used as raw material. Throughout the study, emission spectroscopy analyses were performed to evaluate the overall temperature of the vaporization process and C[subscript 2] density. Furthermore, several techniques, such as UV spectrophotometry, HPLC chromatography, surface area, thermogravimetric analysis and scanning and transmission electron microscopy were also used to analyze the soot produced in the plasma process.--Résumé abrégé par UMI.
- Génie – Thèses