Recent Developments in Advanced Materials and Processes

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Authors: M. Marinović-Cincović, Guillaume Wang, Michel Fedoroff, Z.V. Šaponjić, S.K. Milonjić, J.M. Nedeljković
Abstract: A synthetic procedure based on thermal hydrolysis of iron(III) chloride solutions for the preparation of hematite (α-Fe2O3) and ferricoxychloride (FeOCl) colloids consisting of nanoparticles (NPs) is described. Transmission electron microscopy indicated that both colloids consisted of particles smaller than 10 nm. X-ray diffraction measurements revealed transformation of FeOCl NPs into α-Fe2O3 NPs after a few months. The phase transformation was explained in terms of redissolution – recrystallization process. UV-vis spectroscopy was used for precise determination of the band gap of α-Fe2O3.
Authors: S.K. Milonjić, Smiljka D. Čupić, Lj.S. Čerović
Abstract: The sorption of ferric and ferrous ions from aqueous solutions on the silica powder, obtained from colloidal dispersion of silica (silica sol), was studied as a function of their concentrations and solution pH. The amount of sorbed ferric and ferrous ions increases with increasing final pH of the solution. The sorption isotherms are of high-affinity type. A sorption mechanism of ferric and ferrous ions from aqueous solutions on silica is proposed.
Authors: Miha Drofenik, M. Kristl, Darko Makovec, Aljoša Košak
Abstract: Sonochemically assisted co-precipitation has been used to prepare nanosized manganesezinc- ferrite powder. A suspension of constituent hydroxides was ultrasonically irradiated for various times with high-intensity ultrasound radiation (20 kHz, 750 W) using a direct-immersion titanium horn. The average grain size and magnetization of the synthesized MnZn-ferrite nanoparticles gradually increases with the time of ultrasonic irradiation.
Authors: Amelia Montone, Jasna Grbović Novaković, Lj. Stamenković, Anna Lisa Fiorini, Luca Pasquini, Ennio Bonetti, Marco Vittori Antisari
Abstract: The influence of the Co addition and synthesis route on desorption properties of MgH2 were investigated. Ball milling of MgH2-Co blends was performed under Ar using different milling intensities and different weight ratios. Microstructural and morphological characterization, performed by XRD and SEM, show a huge correlation with thermal stability and hydrogen desorption properties investigated by DSC. A complex desorption behaviour is correlated with the dispersion of the catalytic particles that appears to play a main role in desorption performances. The optimum catalyst concentration was found to be around 10 wt.%, while the optimum value of the ball to powder ratio was 10:1.
Authors: V. Dondur, Nenad Radić, Boško Grbić, Miha Drofenik
Abstract: In this paper the adsorption and oxidation of CO on nanocrystalline Au/γ-Fe2O3, Au/α- Fe2O3, γ-Fe2O3 and a series of mixed ferrite with MnxZn1-xFe2O4 composition are investigated. The catalysts were prepared by co-precipitation method and characterized using X-ray diffraction (XRPD), specific surface (BET), transition electron spectroscopy (TEM) and magnetization measurements. A temperature programmed desorption (TPD) study of the water and CO interaction with nanocrystalline adsorbents is presented. The catalytic activities towards CO oxidation increased in the following order: γ-Fe2O3 < MnxZn1-xFe2O4 < Au/γ-Fe2O3 .
Authors: Marija Maletin, Željka Cvejić, S. Rakić, L.M. Nikolić, Vladimir V. Srdić
Abstract: Advances in nanoscale electronics require superior ceramic powders, preferable prepared with techniques for the direct synthesis of crystalline nanoparticles. Zinc ferrite (ZnFe2O4) nanopowders were prepared by co-precipitation method, from nitrate precursors. Crystalline powders having the single-phase cubic spinel structure were directly synthesized at temperature ≥80°C in the presence of NaOH. The obtained powders are agglomerated with ultra-fine crystallites having the average crystallite size about 3-4 nm.
Authors: Snezana Bošković, D. Djurović, B. Matović, M. Čančarević, Z. Dohčević-Mitrović, Zoran V. Popović, Matvei Zinkevich, Fritz Aldinger
Abstract: One of the methods for powder synthesis that is both cost and time effective is the selfpropagating room temperature synthesis. We applied this method to synthesize rare earth doped ceria nanopowders. Since they exhibit very high ionic conductivity at intermediate temperatures these compositions are attractive for a new generation of nanostructured ceramics applicable in solid oxide fuel cells as electrolytes. In this paper we paid our attention to the reaction based on methathetical pathway, whereby solid solution nanopowders of rare earth elements with ceria were obtained at room temperature. Compositions of Ce1-xRexO2-δ (Re = Y , Nd) were synthesized with x ranging from 0 to 0.20. The reaction course is discussed and the properties of the obtained powders are presented.
Authors: M. Šćepanović, M. Grujić-Brojčin, Z. Dohčević-Mitrović, Zoran V. Popović
Abstract: Nanosized titanium dioxide (TiO2) powders in anatase phase were prepared by laserinduced pyrolysis. Specific surface area of as-grown powders measured by BET method was between 77 and 110 m2/g. The particle sizes (14.4-20.6 nm) estimated from these data coincide well with the crystallite sizes (12.3-17.4 nm) determined by XRD measurements. The mean particle sizes (35-41 nm) obtained from the subsequent SEM measurements refer to considerable agglomeration of nanoparticles. Raman spectroscopy has been used to investigate the structural properties as well as the changes under laser irradiation of TiO2 nanopowders. The blueshift and broadening of the lowest frequency Eg Raman mode were analyzed using a phonon-confinement model which includes strain effect and broadening associated with the size distribution. Influence of the nonstoichiometry and anharmonic effects on this mode have been also investigated. Besides, different changes in Raman spectra after the laser irradiation in vacuum were observed for the nanopowders with different strain values.
Authors: Lydia Mančić, G. del Rosario, Z. Marinković, O. Milošević
Abstract: The yttrium-aluminium garnet phase (YAG) represents a suitable host material for solidstate lasers and is widely used for various display applications being doped with rare-earth ions. Introduction of Ce3+ ion as a luminescence centre transforms it from insulating to effective phosphor material capable of emitting radiation in the visible spectrum. In this work Ce3+ doped YAG powder was obtained via aerosol route using nitrate precursor solution. Well-crystallized targeted phase was obtained after additional thermal treatment. A combination of different analysis techniques (differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy with determination of image metrology, energy dispersive spectroscopy, transmission electron microscopy) is used to obtain detailed information about the structural and morphological powder properties. The effects of both processing parameters and post annealing treatment conditions are discussed from the viewpoint of establishing the best relationship between them and produced YAG:Ce3+ crystal structure.
Authors: Lj. Vulićević, N. Ivanović, A. Maričić, A. Vučković, N. Popović, S. Vardić
Abstract: Structural, magnetic and electrical properties of iron oxide nano-sized powders synthesised electrochemically under various conditions are presented. The influence of the temperature and current density of synthesis on particular powder characteristics is established. Possibilities for co-existence of various phases and their impact on powder properties, as well as feasible paths of phase relaxation and transition during non-isothermal heating are investigated, too. In this way, optimal procedures for the preparation and stabilisation of iron oxides nano-sized powders of different characteristics are evaluated.

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