Materials Science Forum Vol. 570

Abstract: Crystallization of the amorphous metallic alloy Fe73.5 Cu1Nb3 Si8.5 B14 was investigated by ferromagnetic resonance (FMR), small angle in situ X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC). Only one crystalline phase was observed by WAXS and only one peak was observed by DSC. The activation energies, calculated from FMR and DSC data, were 287 kJ.mol-1 and 313.4 kJ.mol-1, respectively. The values calculated for the Avrami exponent were 0.98 (FMR) and 1.4 (DSC). These values correspond to different mechanisms of nucleation and growth; however, the SAXS /WAXS results suggest that the dominant mechanisms are nucleation and growth of crystals from small dimensions.

Abstract: In the present work the crystallization process of an aluminum-based amorphous metal have been investigated. Rapidly quenched Al85Ce5Ni10 ribbon has been produced by melt-spinning. The amorphous structure evolution during heating has been studied by a combination of X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Thermograms obtained in continuous heating regime reveal a glass transition, Tg, resulting in a supercooled liquid temperature range of ∼16°C. Multiple crystallization events were observed by isothermal annealing of the as-quenched melt-spun ribbon at temperatures below Tg; precipitation of a metastable phase in the amorphous matrix has been observed. Further heating at increasing temperatures resulted in complete crystallization with α-Al and intermetallic compounds. Kinetics analyses indicate that crystallization occurs though nucleation and three-dimensional growth.

Abstract: The present paper reports a simple calculation of the size and shape dependent melting temperature of nanoparticles. The melting temperature of any nanoparticle basically depends on the ratio of surface atoms to the total atoms. Significant melting temperature suppression is observed when the particle size approaches the sub-20 nm range. The behavior of melting temperature is similar for the larger nanoparticles of all considered shapes but differs significantly for small nanoparticles. Different melting temperature is predicted for the nanoparticles of the same size in different shapes.

Abstract: In this work a novel approach for the preparation of Fe3O4/PANI (polyaniline) thin film composite containing magnetic nanoparticles is presented. Magnetite (Fe3O4) nanoparticles have been coated by PANI and the PANI chains have been doped by 10-camphorsulfonic acid (CSA). The doped composite is soluble in common organic solvents. Thin films of composites of polyaniline (PANI) were casted from m-cresol. Several characterization techniques were employed in order to determine composition, structure and magnetic properties of the nanocomposite film (Xray diffraction, transmission electron microscopy, TEM, Scanning electron microscopy, SEM, and optical microscopy). The magnetization data were obtained from M(H) hysteresis loops and zero field cooling – field cooling, ZFC-FC. Magnetic measurements evidence a ferromagnetic behaviour of the obtained composite, at room temperature with saturation magnetization of about 3.4 emu/g and coercivity of 42 Oe. The temperature dependences of the conductivity of the films follows the         = − 1 / 2 ( ) exp T T To o σ σ law, which has been explained within the framework of the onedimensional variable-range-hoping (1D-VRH) model. Application of 1T magnetic field increases the resistivity of the film and the temperature slope dependence.

Abstract: Fe-Si alloys have excellent soft magnetic properties, specially around 12 at% Si. However, its industrial application is limited because of the lack of ductility, which causes cracking during rolling operations for the fabrication of thin sheets. The reason of the brittleness of the high silicon alloys is a disorder/order reaction at low temperatures. The aim of this work is to analyze the effect of the addition of Aluminum on the crystalline structure of Fe-Si alloys. Samples with a chemical composition of Fe88Si12 and Fe87Si12Al1 (at%) were prepared by Spray Forming. The structure was studied by means of X-ray diffraction and Mössbauer Spectroscopy. The presence of the DO3 and α- Fe phases were observed

Abstract: The purpose of this paper is to research and develop a new nanofluid synthesis system that uses plasma arc as heat source to fabricate nanofluid having high suspension stability. This system uses high temperature produced by plasma arc system to cause transient vaporization to metal, which is then followed by the induction of vaporized metallic gas into the collection piping by the induction system. At the same time, it mixes thoroughly with the pre-condensed deionized water, and the mixture is then underwent a rapid cooling process. Because of low temperature, the metallic gas condenses into nanoparticles, which is finally stored in the collection tank in the form of nanofluid. This paper discusses the influence of working current towards the fabricated Al2O3 nanoparticle. Also, based on the Al2O3nanofluid having different pH values, it analyzes into the suspension stability of its Zeta potential value. Furthermore, it investigates into the absorption properties of Al2O3 nanofluid towards UV/Vis. Besides, as known from the experimental result of the fuel calorific test, when the weight concentration of the Al2O3 nanofluids that is produced by a better fabrication is 3%, it explores into its good combustion efficiency towards 92 unleaded gas.