Preparation and Magnetic Properties of Fe Nanoparticles by Chemical Vapor Condensation Process
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Preparation and Magnetic Properties of Fe Nanoparticles by Chemical Vapor Condensation Process C. J. Choi1, B. K. Kim1 and X. L. Dong2 1 Korea Institute of Machinery and Materials, 66 Sangnam-Dong, Changwon, Kyungnam 641010, Korea 2 Laboratory of Ultrafine Particles, Shenyang Polytechnic University, 110023, Shenyang, Peoples’ Republic of China ABSTRACT Nano-sized Fe particles were synthesized by Chemical Vapor Condensation (CVC) Process using the precursor of iron carbonyl (Fe(CO)5) as the source. We investigated the microstructures, magnetic properties of the Fe nanoparticles and their oxidation behavior during annealing systematically by means of HRTEM, DTA-TG, Mössbauer spectroscopy. The prepared particle was nearly spherical shape and core-shell type structure. The magnetic states of Fe nanoparticles changed from superparamagnetism to ferromagnetism with the particle size and microstructure. Oxidation heat treatment leads to the successive appearance of oxide phases. INTRODUTION In recent years, much attention has been paid to synthesize and investigate nanoparticles, because of their wide range of potential applications [1]. Especially magnetic nanopaticles can have special characteristic of exhibiting single-domain magnetism and can be used in magnetic tapes, ferrofluid, magnetic refrigerants, etc, because of their ultrafine size less than magnetic domain size [2]. Various techniques for the preparation of nanoparticles have been developed such as vapor condensation, spray pyrolysis, spark erosion and mechanical milling, etc [3,4]. Among them, chemical synthesis of nanoparticles is a rapidly growing field with a great potential in making useful materials. Using this method, chemical homogeneity is achieved at the molecular scale and the particle size can be reduced to a nanoscale regime. Rapid condensation of metallic vapor produces fine-grained structures. This attractive process is very flexible and quite suitable for preparing small quantities of material, demonstrating unique properties. In the present work, we synthesized Fe nanoparticles by Chemical Vapor Condensation (CVC) method from organometallic precursor of iron pentacarbonyl (Fe(CO)5) [5]. The structural and magnetic properties of free-standing nanoparticles were investigated. W9.37.1
EXPERIMENTAL DETAILS The basic setup for CVC is similar to that described in literature elsewhere [5,6]. To produce iron nanoparticles, various carrier gases are fed through a heated bubbling units containing the liquid iron pentacarbonyl (Fe(CO)5) precursor. The flow of the carrier gas entrains precursor vapor and pass through the heated furnace in which the precursor pyrolyzes and condenses into clusters or particles. The synthesized powders are scraped off and collected from a rotating chiller cooled by liquid nitrogen. Experiments were conducted with a tubular furnace uniformly heated at a temperature between 400 and 1100oC. The morphologies and lattice images of particles were determined with HRTEM (High Temperature Transmission Electron Microscopy). Identific
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