Condensation of Carbon Vapour in the Microwave Oven
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Condensation of Carbon Vapour in the Microwave Oven Oxana V. Kharissova1, Israel Nieto Lopez1, Ubaldo Ortiz Méndez2, Juan A. Aguilar2 and Moisés Hinojosa Rivera2. 1 Facultad de Ciencias Físico-Matemáticas, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, N.L., México, C.P.66450. E-mail [email protected] 2 Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, N.L., México, C.P.66450. E-mail [email protected] ABSTRACT This work is devoted to microwave heating of graphite for studying the processing of carbon nanotubes (CNTs) by graphite vaporization. We have applied heating by microwaves (MW) (power 800W, frequency 2.45 GHz) in air at 20-90 min. The oven temperature was approximately 1200°C. The condensed material was collected on a fused silica target. After deposition, the morphology of carbon nanotubes was studied by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and Transmission Electron Microscopy (TEM). The samples were found to contain nanotubes, nanoparticles and fibers (at 1.30-2.80 micrometers to 6-11 micrometers) which appeared to be highly graphitized. It was observed that multi-walled nanotubes (MWNT´s) were produced by this method. INTRODUCTION Multi-walled carbon nanotubes (MWNT´s) were first discovered in 1991 [1]. The walls of this kind of nanotubes consist of multi-layered coaxial cylinders of carbon atoms. In 1993, the other kind of nanotubes, called single-walled carbon nanotubes (SWNT´s), was discovered by NEC and IBM, respectively. Unlike MWNT´s, the walls of SWNT´s have only a single-layer of carbon atoms. Composed of pure carbon, carbon nanotubes are hollow cylinders with a few nanometers in diameter. The honeycomb structure of carbon atoms on the cylinder walls is similar to that of graphite. Due to such special arrangement of carbon atoms, several distinctive properties of carbon nanotubes have been extensively studied. Numerous potential applications, such as flat panel displays [2], chemical sensors [3], hydrogen storage [4], etc., have been proposed. A number of methods such as arc discharge [5], laser vaporization [6], pyrolysis [7,8], plasma-enhanced [9,10] or thermal chemical vapor deposition (CVD) [11,12], have been developed for the production of CNTs. The synthesis of CNT´s is often accompanied by the formation of other forms of carbon, such as fullerenes, polyhedral particles and amorphous forms of carbon. In many instances purification of CNT´s (removal of side products) is necessary [13]. The microwave (MW) irradiation technique is widely applied in some areas of chemistry [14] and technology to produce or degrade various materials and chemical compounds [15], as well as in the study of chemical processes. Some of its advantages are: a) rapid heating is simply achieved; b) the energy is accumulated in the material; c) the environment do not need to be heated, so energy savings are possible; d) there is no direct contact between the energy source and the material; e) the heati
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