Decoration of silicon carbide nanotubes by CoFe 2 O 4 Spinel nanoparticles.
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Decoration of silicon carbide nanotubes by CoFe2O4 Spinel nanoparticles. Claude Estournès1, Cuong Pham-Huu2, Nicolas Keller2, Marc J. Ledoux2, Groupe des Matériaux Inorganiques Institut de Physique et Chimie des Matériaux de Strasbourg UMR7504 CNRS-ULP-ECPM 23 rue du Loess 67037 Strasbourg Cedex France 2 Laboratoire de Chimie des Matériaux Catalytiques, ECPM, GMI, CNRS, Université Louis Pasteur, 25 rue Becquerel, 67087 Strasbourg Cedex 2, France. 1
ABSTRACT Silicon carbide nanotubes have been prepared and decorated with CoFe2O4 spinel. These nanocomposites were prepared by incipient wetness impregnation of the dried SiC support with a stoichiometric aqueous solution of the cobalt and iron nitrates. After drying, subsequent annealing treatments were performed under air in the temperature range 873 to 1073 K. X-ray diffraction and high resolution transmission electron microscopy reveal the presence of spinel nanoparticles at the surface of the tubes. Magnetic properties of the nanocomposites show in the magnetic field explored (up to 5 T) that saturation magnetization is not observed neither at room temperature nor at 5Kelvin. The nanometric character and the nature of the spinel particles are also confirmed by the coercive field (1.6 T) observed at low temperature and the curie temperature.
INTRODUCTION The design and synthesis of materials of nanometer size are currently the subject of intense research because their properties differ considerably from those of the corresponding bulk materials. Many researchers have been active in preparing systems in which magnetic nanocrystalline particles are separated by means of a non-magnetic material in order to improve the magnetic properties. Bulk cobalt ferrite CoFe2O4 is usually assumed to have a collinear ferrimagnetic spin structure. It is a partially inverse spinel, the ratio Fe(A)/Fe(B) depends on the prepartion process. Co-ferrite has a very high cubic magnetocrystalline anisotropy accompanied by a reasonable saturation magnetization. These properties make it a promising material, whether or not nanoparticles can be prepared, for use in the production of isotropic permanent magnets, magnetic recording and magnetic fluids. A number of techniques (chemical reactions [1-4], hydrothermal method [5], microemulsion [6,7], sonochemistry [8], mechanical alloying [9] and glass crystallisation [10]) were recently used for producing fine pure Co-ferrite powders. However, studies on supported or embedded CoFe2O4 nanoparticles are rare [11] compared to, say, works done in metal/oxide thin films or composites. The matrices or supports commonly used for nanocomposites are either polymers or oxides like silica or alumina. Unluckily, these phases may degrade or react with the magnetic phase upon thermal treatment. Silicon carbide is a well known chemically inert material, which does not react with the supported phase. It has been reported that despite the chemical inertness of its surface SiC exhibits a relatively good dispersion capacity for metals or oxide phases, due to the prese
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