Papers by Author: Kotaro Hanada

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Authors: Jose Brito Correia, Vanessa Livramento, Nobumitsu Shohoji, Elena Tresso, Kazunori Yamamoto, Tomitsugu Taguchi, Kotaro Hanada, Eiji Osawa
Abstract: Copper has widespread use as engineering material, because of its structural and functional properties, notably high thermal and electrical conductivity. A major drawback of this base metal and its alloys is a relatively low hardness. This precludes its utilization in applications in which both high conductivity and high strength/hardness are needed, e.g. in injection moulds for plastics. Nanostructured metals and nanocomposites are ways to address the low hardness problem, provided the nanostructured material is thermally stable during processing and service. In the present research, composite powders, with 5 to 30 at % nanodiamond, were consolidated into bulk samples. The copper-nanodiamond composite powders were vacuum encapsulated and extruded at 600°C. A significant proportion of the initial hardness in the powders is retained after extrusion. Transmission electron microscopy (TEM) of the extruded material indicates good bonding between the nanodiamond particles and the copper matrix. Raman spectroscopy on the consolidated samples evidences the presence of graphite, possibly due to partial disintegration of ultradisperse nanodiamond agglomerates.
Authors: Daniela Nunes, Vanessa Livramento, Jose Brito Correia, Kotaro Hanada, Patrícia Almeida Carvalho, R. Mateus, Nobumitsu Shohoji, H. Fernandes, C. Silva, Eduardo Alves, Eiji Osawa
Abstract: Due to their interesting properties copper-based materials have been considered appropriate heat-sinks for first wall panels in nuclear fusion devices. The concept of property tailoring involved in the design of metal matrix composites has led to several attempts to use nanodiamond (nDiamond) as reinforcement. In particular, nDiamond produced by detonation has been used to reinforce copper. In the present study, powder mixtures of copper and nDiamond with 20 at. % C were mechanically alloyed (MA) and consolidated via hot extrusion or spark plasma sintering (SPS). The hardness evolutions as well as the structural characterization of as-milled nanocomposite powders and consolidated samples are reported. Density measurements indicate that the consolidation outcome varies significantly with the process used. Transmission electron microscopy (TEM) inspection of the extrusion consolidated sample revealed bonding at the interface between copper and nDiamond particles. The nDiamond size distribution was determined from TEM observations. The results obtained are discussed in terms of consolidation routes.
Authors: Kotaro Hanada, Hitomi Yamaguchi
Abstract: This paper describes the development of spherical iron-based composite powder with carried alumina abrasive grains made by a plasma spray technique. Carbonyl iron powder (7.2 μm average size) and alumina abrasive grains (0.3 μm average size) are sprayed into the plasma flame from the respective nozzles simultaneously, or their mechanical mixture is directly plasma-sprayed. In case of the composite powder obtained by the direct spray method, the alumina abrasives are well carried on the carbonyl iron particles. However, a plasma current of more than 100 A causes melting and vaporizing of the alumina abrasives;, consequently the carbonyl iron and alumina abrasives are separated. The magnetic abrasive experiments with the composite powder developed are made for SUS304 stainless steel plate, and the result shows that the developed composite powder has high potential abrasive performance.
Authors: Kotaro Hanada, Yusuke Hashiura, Ryutaro Maeda, Toshio Sano, Hideaki Negishi
Authors: Kotaro Hanada, A. Imahori, H. Negishi, Toshio Sano, Masao Mayuzumi
Authors: Kunio Matsuzaki, Kanichi Hatsukano, Kotaro Hanada, T. Shimizu, T. Sano
Authors: Kunio Matsuzaki, Kanichi Hatsukano, Y. Torisaka, Kotaro Hanada, Toru Shimizu, M. Kato
Abstract: Mg-Al-Zn alloys containing 0.5% Ca were strip cast into sheets with a thickness of about 1.0mm by twin roll caster. It is found that the addition of Ca to Mg95Al5-XZnX (wt%)alloys prevents the oxidation and burning of molten, and makes the melting and casting easy. The as-cast Mg96Al4Zn0.5Ca0.5 alloy sheet has few cracks at the edge. With increasing Zn content, the generation of cracks occurs more markedly. The as-cast alloys have equiaxed grains with an average grain size of 10 μm. A fine microstructure is obtained. All the samples consist of single hcp-Mg phase. The yield and ultimate tensile strength of the as-cast sheets are in the range of 180 to 200 MPa and 265 to 275 MPa, respectively. The alloy Mg95Al2Zn2.5Ca0.5 shows an elongation of 21% as well as a high strength of 275 MPa. The annealing at 400 °C causes an improvement of elongation to 24% and 30% for Mg96Al4Zn0.5Ca0.5 and Mg95Al2Zn2.5Ca0.5,respectively. A further enhancement of mechanical properties is expected by an appropriate thermomechanical treatment. The as-cast Mg96Al4Zn0.5Ca0.5 sheet was deep drawn at 250°C and a drawing ratio of 2.0 without cracking . In summery, the Ca added Mg alloys are suitable for the production of Mg alloy sheets by strip casting and the cast alloy sheet have high strength with ductility and good formability
Authors: Toru Shimizu, Kotaro Hanada, Satoru Adachi, Masahito Katoh, Kanichi Hatsukano, Kunio Matsuzaki
Abstract: Stainless steel sludge is generated as a waste in the grinding process, and the possibility of recycling stainless steel is considered here. Generally, stainless steel grinding sludge ranging about 10,000 are generated per a year in Japan, and most of it is discarded or re-melted with scrap steel. In this study, we considered the possibility of using the stainless steel sludge as metal powder for MIM or raw material for metal foam. For the MIM process, the metal powder will need some improvement, and flotation and spheroidizing processes of the sludge are necessary. For fabrication of the metal foam, untreated sludge can be used, and steel foam about 90% porosity is produced.
Authors: Kunio Matsuzaki, Kotaro Hanada, Kanichi Hatsukano, Toru Shimizu
Authors: Noboru Nakayama, Masao Mayuzumi, Kotaro Hanada, Toshio Sano, Ryo Tominaga, Hiroyuku Takeishi
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