Compact Ag@fe3o4 Core-shell Nanoparticles By Means Of Single-step Thermal Decomposition Reaction

A temperature pause introduced in a simple single-step thermal decomposition of iron, with the presence of silver seeds formed in the same reaction mixture, gives rise to novel compact heterostructures: brick-like Ag@Fe3O4 core-shell nanoparticles. This novel method is relatively easy to implement, and could contribute to overcome the challenge of obtaining a multifunctional heteroparticle in which a noble metal is surrounded by magnetite. Structural analyses of the samples show 4 nm silver nanoparticles wrapped within compact cubic external structures of Fe oxide, with curious rectangular shape. The magnetic properties indicate a near superparamagnetic like behavior with a weak hysteresis at room temperature. The value of the anisotropy involved makes these particles candidates to potential applications in nanomedicine.4Brown, M.A., Effects of the operating magnetic field on potential nmr contrast agents (1985) Magn. Reson. 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PrestoPronto: A code devoted to handling large data sets

International audienceThe software PrestoPronto consist to a full graphical user interface (GUI) program aimed to execute the analysis of large X-ray Absorption Spectroscopy data sets. Written in Python is free and open source. The code is able to read large datasets, apply calibration, alignment corrections and perform classical data analysis, from the extraction of the signal to EXAFS fit. The package includes also programs with GUIs] to perform, Principal Component Analysis and Linear Combination Fits. The main benefit of this program is allow to follow quickly the evolution of time resolved experiments coming from Quick-EXAFS (QEXAFS) and dispersive EXAFS beamlines

Controlled Mechanochemical Synthesis And Hydrogen Desorption Mechanisms Of Nanostructured Mg2coh5

Magnesium complex hydrides are attractive for hydrogen storage applications, mainly due to their high volumetric capacities and to their relatively low cost. In this work, nanocrystalline Mg2CoH5 was synthesized with very high yields (97%) by reactive milling cobalt and magnesium under relatively mild processing conditions (30 bar of H2 pressure and 12 h of milling). The behavior of the milled Mg2CoH5 during heating was studied by a combination of several techniques including DSC, QMS, TGA and in-situ synchrotron XRD. It is shown for the first time that two different mechanisms of hydrogen desorption take place. At low temperatures (up to 325°C), some hydrogen is released by a diffusional mechanism with no change in the crystalline structure of the high temperature γ-Mg2CoH5 phase. At higher temperatures, above 325°C, the γ-Mg2CoH5 phase becomes unstable and the complex hydride decomposes into Mg, Co and H2. This is the first work to report the diffusional hydrogen desorption mechanism for the Mg2CoH5 or any other complex hydride. Furthermore, a complete description of the allotropic β-Mg2CoH5 to γ-Mg2CoH5 phase transition is provided.40315041515Satyapal, S., Petrovic, J., Read, C., Thomas, G., Ordaz, G., The US Department of Energy 's National Hydrogen Storage Project: Progress towards meeting hydrogen-powered vehicle requirements (2007) Catal Today, 120, pp. 246-256Huot, J., Ravnsbaek, D.B., Zhang, J., Cuevas, F., Latroche, M., Jensen, T.R., Mechanochemical synthesis of hydrogen storage materials (2013) Prog Mater Sci, 58, pp. 30-75Yvon, K., Complex transition-metal hydrides (1998) Chimia, 52, pp. 613-619Zolliker, P., Yvon, K., Fischer, P., Schefer, J., Dimagnesium cobalt(I) pentahydride, Mg2CoH5, containing square-pyramidal CoH5 4- anions (1985) Inorg Chem, 24, pp. 4177-4180Huot, J., Hayakawa, H., Akiba, E., Preparation of the hydrides Mg2FeH6 and Mg2CoH5 by mechanical alloying followed by sintering (1997) J Alloy Compd, 248, pp. 164-167Selvam, P., Yvon, K., Synthesis of Mg2FeH6, Mg2CoH5 and Mg2NiH4 by High-pressure sintering of the elements (1991) Int J Hydrogen Energ, 16, pp. 615-617Chen, J., Takeshita, H.T., Chartouni, D., Kuriyama, N., Sakai, T., Synthesis and characterization of nanocrystalline Mg2CoH5 obtained by mechanical alloying (2001) J Mater Sci, 36, pp. 5829-5834Zhang, J.X., Cuevas, F., Zaidi, W., Bonnet, J.P., Aymard, L., Bobet, J.L., Highlighting of a single reaction path during reactive Ball milling of Mg and TM by quantitative H2 Gas sorption analysis to form ternary complex hydrides (TM = Fe, Co, Ni) (2011) J Phys Chem C, 115, pp. 4971-4979Asselli, A.A.C., Botta, W.J., Huot, J., Formation reaction of Mg2FeH6: Effect of hydrogen Absorption/desorption kinetics (2013) Mater Res-Ibero-Am J, 16, pp. 1373-1378Asselli, A.A.C., Jorge, A.M., Ishikawa, T.T., Botta, W.J., Mg2FeH6-based nanocomposites with high capacity of hydrogen storage processed by reactive milling (2012) Mater Res-Ibero-Am J, 15, pp. 229-235Asselli, A.A.C., Leiva, D.R., Jorge, A.M., Ishikawa, T.T., Botta, W.J., Synthesis and hydrogen sorption properties of Mg2FeH6-MgH2 nanocomposite prepared by reactive milling (2012) J Alloy Compd, 536, pp. S250-S254Leiva, D.R., Villela, A.C.D., Paiva-Santos, C.D., Fruchart, D., Miraglia, S., Ishikawa, T.T., High-yield direct synthesis of Mg2FeH6 from the elements by reactive milling (2011) Solid State Phenomen, 170, pp. 259-262Leiva, D.R., Zepon, G., Asselli, A.A.C., Fruchart, D., Miraglia, S., Ishikawa, T.T., Mechanochemistry and H-sorption properties of Mg2FeH6-based nanocomposites (2012) Int J Mater Res, 103, pp. 1147-1154Bab, M.A., Mendoza-Zelis, L., A model for the kinetics of mechanically assisted gas-solid reactions (2004) Scr Mater, 50, pp. 99-104Bab, M.A., Mendoza-Zelis, L., Damonte, L.C., Nanocrystalline HfN produced by mechanical milling: Kinetic aspects (2001) Acta Mater, 49, pp. 4205-4213Figueroa, S.J.A., Gibson, D., Mairs, T., Pasternak, S., Newton, M.A., Di Michiel, M., Innovative insights in a plug flow microreactor for operando X-ray studies (2013) J Appl Crystallogr, 46, pp. 1523-1527Varin, R.A., Czujko, T., Chiu, C., Wronski, Z., Particle size effects on the desorption properties of nanostructured magnesium dihydride (MgH2) synthesized by controlled reactive mechanical milling (CRMM) (2006) J Alloy Compd, 424, pp. 356-364Liang, G., Huot, J., Boily, S., Van Neste, A., Schulz, R., Catalytic effect of transition metals on hydrogen sorption in nanocrystalline ball milled MgH2-Tm (Tm = Ti, V, Mn, Fe and Ni) systems (1999) J Alloy Compd, 292, pp. 247-252Gennari, F.C., Castro, F.J., Formation, composition and stability of Mg-Co compounds (2005) J Alloy Compd, 396, pp. 182-192Norek, M., Nielsen, T.K., Polanski, M., Kunce, I., Plocinski, T., Jaroszewicz, L.R., Synthesis and decomposition mechanisms of ternary Mg2CoH5 studied using in situ synchrotron X-ray diffraction (2011) Int J Hydrogen Energ, 36, pp. 10760-10770Fernandez, I.G., Meyer, G.O., Gennari, F.C., Hydriding/dehydriding behavior of Mg2CoH5 produced by reactive mechanical milling (2008) J Alloy Compd, 464, pp. 111-117Fernandez, I.G., Meyer, G.O., Gennari, F.C., Reversible hydrogen storage in Mg2CoH5 prepared by a combined milling-sintering procedure (2007) J Alloy Compd, 446, pp. 106-109Veron, M.G., Condo, A.M., Gennari, F.C., Effective synthesis of Mg2CoH5 by reactive mechanical milling and its hydrogen sorption behavior after cycling (2013) Int J Hydrogen Energ, 38, pp. 973-981Zaluski, L., Zaluska, A., Strom Olsen, J.O., Nanocrystalline metal hydrides (1997) J Alloy Compd, 253, pp. 70-7

Electronic structures of cyclometalated palladium complexes in the higher oxidation states

The electronic and redox properties of a series of cyclometalated Pd complexes with oxidation states of +2, +3 and +4 were examined using a range of currently available spectroscopic and electrochemical techniques. Changes in metal–ligand bond lengths were established by X-ray crystallography and correctly predicted by DFT calculations, from which the frontier orbitals and partial atomic charges can be obtained. X-ray absorption spectroscopy (XAS) revealed interesting XANES features that suggest a synergistic relationship between metal–ligand interactions. The electrochemical study of the Pd(II) dimer was found to contain two sequential oxidative potentials indicative of a weak metal–metal interaction

Low temperature rolling of AZ91 alloy for hydrogen storage

The hydrogen storage properties of a commercial AZ91 magnesium alloy were investigated after processing by cold rolling in two different conditions: (a) extensive cold rolling at room temperature (CR); (b) rolling with the immersion of the alloy in liquid nitrogen bath after 05 rolling passes. This second condition is named as low temperature rolling (LTR). A full microstructural characterization including scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), X-ray photoelectron and positron annihilation life time spectroscopy (XPS and PALS) were performed in the processed alloys. The hydrogen storage properties were measured using a Sievert-type apparatus. The AZ91-alloy is composed by the β-Mg and Mg17Al12 phases, and after processing by CR, an intense peak broadening and strong [002] texture were observed in the alloys. The LTR processing resulted in a more fragile material containing more microcracks and exposed interfaces than the conventionally cold rolled one. The LTR sample also presented a more refined microstructure in comparison with CR sample. These features resulted in superior hydrogen storage properties for the LTR sample in comparison with the CR sample. In addition, the effect of surface contamination was also studied in detail and it was found to play a significant role during the activation kinetics.Fil: Floriano, R.. Universidade Estadual de Campinas; BrasilFil: Leiva, D. R.. Universidade Federal do São Carlos; BrasilFil: Melo, G. C.. Universidade Federal do São Carlos; BrasilFil: Ishikawa, T. T.. Universidade Federal do São Carlos; BrasilFil: Huot, J.. Universite Du Quebec A Trois-rivieres; CanadáFil: Kaufman, M.. Department of Metallurgical and Materials Engineering; Estados UnidosFil: Figueroa, S.J.A.. Centro Nacional de Pesquisa Em Energia E Materiais; BrasilFil: Mendoza Zélis, Luis Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Damonte, Laura Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Botta, W.J.. Universidade Federal do São Carlos; Brasi