Effect of Nanostructure on the Thermal Oxidation of Atomized Iron
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0899-N07-01.1
Effect of Nanostructure on the Thermal Oxidation of Atomized Iron M. Kumar 1, N. Rawat 1 and K.S.V. Santhanam 1,2 Center For Materials Science and Engineering, 2Department of Chemistry Rochester Institute of Technology, Rochester, NY 14623
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Abstract The effect of nanostructure on the thermal oxidation of atomized iron has been o investigated. Above 500 C atomized iron is oxidized in the presence of air. However, when iron is compacted with multiwalled carbon nanotubes (MWCNT) this oxidation is shifted by more o than 100 C. Iron is protected by the nanostructure environment A large number of compositions of atomic ratios of iron and MWCNT have been examined in this study to understand the effect in detail. The effect of nanostructure in the thermal oxidation of iron is interpreted as due to iron atom experiencing extensive overlap and confinement effect causing spin transfer. Based on the theoretical calculations reported in the literature this confinement effect of iron is suggested to produce a transformation from 3d64s2 to an effective configuration of 3d84s0 producing spintronics effect. Key words: Multiwalled carbon nanotubes, atomized iron, thermogravimetric analysis, thermal oxidation INTRODUCTION The interaction of transition metals with carbon has been of interest in recent times and has been theoretically studied using density function calculations (1-6). An understanding of the interaction is of importance in synthesizing new materials having nanostructures. With carbon nanotubes this interaction can be considered in two ways; in one way iron atom as interacting with the outside surface of the tube that is dependent on configurational geometry. In this case an effective configuration of 3d74s1 can be picturized for the iron atom. In the second case the iron atom is considered to be inside the nanotube resulting in higher hybridization with effective configuration of 3d84s0 (1). This interaction inside the carbon nanotube results in anti ferromagnetic ordering (2). Doping of transition metal atoms inside the carbon nanotube has also been considered theoretically for understanding spintronics (3). These calculations suggest that iron atom adsorbing on hexagonal center of the nanotube as having the most stable configuration.(4). When a carbon nanotube interaction is with magnetic materials it results in magnetization of the nanotubes. (7-9). For example, with ferromagnetic metal a spin polarized charge transfer occurs at the interface between carbon nanotube and the ferromagnetic metal with the result a spin transfer of about 0.1 ยต B per contact carbon atom (7) has been determined by magnetic force microscopy. Insertion of a magnetic atom into carbon nanotube will have applications in recording devices and magnetic inks (10). Several investigations have also been carried out on the properties of transition metals on carbon (11-16). Films formed by the interaction of transition metal with carbon have been studied for UV reflectivity in the range of 6-36 nm (14) and magnetic properties (9).
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