Papers by Author: Claudio Shyinti Kiminami

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Authors: Gisele Ferreira De Lima, Mauricio Mhirdaui Peres, Sebastiano Garroni, Maria Dolors Barò, Santiago Surinyach, Claudio Shyinti Kiminami, Claudemiro Bolfarini, Walter José Botta Filho, Alberto Moreira Jorge
Abstract: Samples of a 2Mg-Fe (at.%) mixture were produced by high energy ball-milling (HEBM) with ball to powder ratio = 20:1, in an argon gas atmosphere, in 190 ml vials (sample-1) to produce powders and in 300 ml vials (sample-2) to produce plates. Both samples were cold-pressed into preforms. The preforms were then extruded at 300°C at a ram speed of 1mm/min., with the following extrusion ratios: sample-1 at 3/1 to ensure porosity and sample-2 at 5/1 to increase the adhesion of the plates. The resulting bulks from samples 1 and 2 were hydrogenated for 24h in a reactor under 15 bar of H2 to produce the Mg2FeH6 complex hydride, and at 11 bar of H2 to produce both the complex hydride and MgH2 hydride. In addition, sample-1 was severely temperature-hydrogen cycled to verify its microstructural stability and the influence of grain size on the sorption properties. XRD patterns showed Mg(hc), Fe(ccc) and Mg2FeH6 in both samples, and sample-2 also contained MgH2 and MgO (attributed to processing contamination). DSC results demonstrated that the initial desorption temperature of sample-1 was lower than that of sample-2. However, sample-2 showed faster desorption kinetics, presenting a desorption peak about 73°C below that of sample-1. This could be attributed to the activation/catalyst effect of the MgH2 hydride. The improvement in sorption properties was attributed mainly to porosity and to the type of employed catalysts.
Authors: F. Saporiti, A.H. Kasama, B. Arcondo, Walter José Botta Filho, Claudio Shyinti Kiminami, Claudemiro Bolfarini, Fernando Audebert
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
Authors: E.M. Mazzer, Claudio Shyinti Kiminami, P. Gargarella, R.D. Cava, L.A. Basilio, C. Bolfarini, W.J. Botta, J. Eckert, T. Gustmann, S. Pauly
Abstract: Shape memory alloys (SMAs) are a class of material that undergoes a reversible shape change after a plastic deformation. The recovery of the original shape is possible due to a structural transformation upon heating to a critical temperature. The shape memory effect is related to a martensitic-austenitic transformation from a phase with a low symmetry (martensite) to a high-temperature phase (parent phase) [1]. Cu-based shape memory alloys have the advantage of large thermal and electrical conductivities and the system Cu-Al-Ni alloys are quite attractive due to better stabilisation against aging phenomena [2].
Authors: Claudio Shyinti Kiminami, N.D. Bassim, Michael J. Kaufman, M.F. Amateau, T.J. Eden, J.M. Galbraith
Authors: Carlos Triveño Rios, C. Bolfarini, Walter José Botta Filho, Claudio Shyinti Kiminami
Abstract: In this work, the microestrutural characterization and mechanical properties of atomized Al-9Si-3Cu alloy powders and extruded samples are presented. The microstructure was evaluated by a combination of X-ray diffraction, optical microscopy and scanning electron microscopy. The mechanical properties of extruded samples were also characterized by tensile test and hardness measurements. The results revealed that the powder particles and the extruded samples are constituted by α-Al, intermetallic and metastable phases. The extruded samples obtained by the use of smaller atomized particles show lower ductility than with larger particles. The same behavior was observed with low extrusion temperature than with high temperatures. It was also observed minor variations in the yield strength and hardness with variation in the size of the powder particles.
Authors: C. Triveño Rios, Conrado R. M. Afonso, Claudemiro Bolfarini, Walter José Botta Filho, Claudio Shyinti Kiminami
Abstract: Bulk glassy alloys based on the Fe-Co-B-Si-Nb system have already achieved high levels of mechanical strength. The present work investigated the microstructural evolution of Fe43.2Co28.8B19.2Si4.8Nb4 alloy during the spray forming and wedge mold casting processes, with emphasis on the formation of amorphous phase. The microstructure was evaluated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The region outer the spray deposit showed the formation of an amorphous structure with a thickness of ~2.5 mm, while that of the wedge-shaped sample exhibited a thickness of up to ~1.5 mm, suggesting that both processes show a promising potential for the production of bulk glass alloys.
Authors: J.B. Fogagnolo, M.F. de Oliveira, Claudio Shyinti Kiminami, Claudemiro Bolfarini, Walter José Botta Filho
Authors: J.B. Fogagnolo, Claudio Shyinti Kiminami, Claudemiro Bolfarini, Walter José Botta Filho
Authors: C.A.D. Rodrigues, Daniel Rodrigo Leiva, K.R. Cardoso, Claudio Shyinti Kiminami, Walter José Botta Filho
Authors: C. Triveño Rios, Santiago Suriñach, Maria Dolores Baró, Claudemiro Bolfarini, Walter José Botta Filho, Claudio Shyinti Kiminami
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.
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