Takeshi Fukami

Bio: Takeshi Fukami is an academic researcher from University of Hyogo. The author has contributed to research in topics: Amorphous metal & Nanocrystalline material. The author has an hindex of 10, co-authored 42 publications receiving 344 citations.

Formation of metal-TiN/TiC nanocomposite powders by mechanical alloying and their consolidation

Abstract: Fe–TiN, Ni–TiN, and SUS316–TiC nanocomposite powders were prepared by ball-milling Fe–Ti, Ni–Ti, and SUS316–TiC powder mixtures in a nitrogen or argon gas atmosphere. Fe–63vol.% TiN and Ni–44–64vol.% TiN milled powders were dynamically compacted by use of a propellant gun to produce bulk materials of nanocrystalline structure and having grain sizes between about 5 and 400 nm. SUS316–2.8–5.6vol.% TiC milled powders were consolidated by hot isostatic pressing (HIP) to produce bulk materials having grain sizes between about 100 and 400 nm. The possibility of using fine-dispersed TiN/TiC particles to pin grain boundaries and thereby maintain ultra-fine grained structures of grain sizes down to the nanocrystalline scale has been discussed.

Microstructure and mechanical properties of neutron-irradiated ultra-fine-grained SUS316L stainless steels and electrodeposited nanocrystalline Ni and Ni–W alloys

Abstract: In order to overcome the irradiation embrittlement in metallic materials, ultra-fine grained SUS316L steels with their grain sizes between 0.1 and 1 μm have been developed by mechanical alloying, and nanocrystalline Ni and Ni–W alloys with their grain sizes between about 6 nm and 20 μm have been developed by electrodeposition. In order to clarify the effects of the neutron irradiation on mechanical properties of the nanocrystalline materials, Vickers microhardness measurements and transmission electron microscopy (TEM) were performed before and after the irradiation of 1.14 × 10 23 and 1.14 × 10 24 n/m 2 . When the grain sizes were less than about 0.3 μm in the SUS316L and the Ni–W alloys, Vickers hardness was almost unchanged, and the irradiation defects could not observed by TEM.

Viscosity Measurements of Zr55Cu30Al10Ni5 and Pd40Cu30Ni10P20 Supercooled Liquid Alloys by Using a Penetration Viscometer

Abstract: Viscosity of Zr 55 Cu 30 Al 10 Ni 5 and Pd 40 Cu 30 Ni 10 P 20 supercooled liquid alloys having bulk metallic glass forming ability has been measured by using a penetration viscometer with a cylindrical probe under high speed heating conditions at heating rates between 20 and 400°C/ min in the temperature range from the glass transition temperatures (Tg) up to above the crystallization temperatures. The viscosity of these alloys decreased with increasing the heating rate and tended to saturate at the heating rate of 200°C/min and above. Their viscosity could be well represented by the Arrhenius relation. The activation energies for viscous flow for Zr 55 Cu 30 Al 10 Ni 5 and Pd 40 Cu 30 Ni 10 P 20 supercooled liquid alloys were about 350 and 250kJ/mol, respectively. The viscosity was also fitted by a Vogel-Fulcher-Tammann (VFT) relationship over the entire temperature range.

Temperature dependence of heat capacity and electrical resistivity of Zr-based bulk glassy alloys

Abstract: The specific heat at constant pressure ( C p ) and electrical resistivity ( ρ ) of Zr 55 Al 10 Cu 35 , Zr 55 Al 10 Cu 30 Ni 5 and Zr 55 Al 10 Cu 25 Ni 10 bulk glassy alloys were measured in the temperature range below 300 K It was found that the measured C p of the Zr 55 Al 10 Cu (35− X ) Ni X ( X =0, 5 and 10 at%) alloys are almost the same The coefficient of electronic specific heat ( γ exp ) and the Debye temperature ( θ D ) of the Zr 55 Al 10 Cu 30 Ni 5 alloy were found to be 405 mJ mol −1 K −2 and 278 K, respectively The ρ of the Zr 55 Al 10 Cu 35 Ni 5 alloy increased as the temperature decreased in the temperature range between approximately 28 and 300 K The ρ of the alloy with the X =5 decreased abruptly below approximately 28 K The ρ of the Zr 55 Al 10 Cu 35 and Zr 55 Al 10 Cu 25 Ni 10 alloys increased with decreasing temperature in the temperature range between 18 and 300 K

Structural evolution during mechanical milling of nanometric and micrometric Al2O3 reinforced Al matrix composites

Abstract: The morphological and microstructural changes during mechanical milling of Al powder mixed with 5 vol% nanoscaled alumina particles (35 nm) were studied. The milling was performed in a planetary ball mill under argon atmosphere for various times up to 24 h. The process was also conducted for Al and Al–5 vol% Al 2 O 3 (1 μm) powders to explore the role of reinforcement nanoparticles on the mechanical milling stages. The results showed that the addition of hard particles accelerate the milling process, leading to faster work hardening rate and fracture of the aluminum matrix. Meanwhile, the structural evolution during mechanical milling of the microcomposite powder occurred faster than that of the nanocomposite powder. The result of X-ray diffraction analysis by Williamson–Hall method determined that the so-called crystallite size and lattice strain of the Al matrix of nanocomposite are smaller than that of the microcomposite. Meantime, the particle size distribution and bulk powder density of the two composites were found to be rather equal after 20 h milling, but they were significantly different from those of the unreinforced Al. The mechanisms of mechanical milling for the reinforced and unreinforced Al powders are addressed with stressing on the role of alumina particles.

High temperature Seebeck coefficient metrology

Abstract: We present an overview of the challenges and practices of thermoelectric metrology on bulk materials at high temperature (300 to 1300 K). The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at high temperature. This has led to the implementation of nonideal practices that have further complicated the confirmation of reported high ZT materials. To ensure meaningful interlaboratory comparison of data, thermoelectric measurements must be reliable, accurate, and consistent. This article will summarize and compare the relevant measurement techniques and apparatus designs required to effectively manage uncertainty, while also providing a reference resource of previous advances in high temperature thermoelectric metrology.

Ni-W electrodeposited coatings: Characterization, properties and applications

Abstract: Nowadays, application of nanocrystalline nickel-tungsten (Ni-W) alloys is receiving a great interest because they are an efficient replacement for hard chromium coatings owing to their premium hardness, wear, and corrosion properties. Moreover, heat-treated nanocrystalline Ni-W alloys demonstrate proper mechanical properties as well as thermal stability at high temperatures. The current paper reviews different aspects of electrodeposition, microstructure, corrosion, oxidation, wear, and mechanical properties Ni-W alloys and nano/micro composites. Besides, heat treatment effects on properties and thermal stability of these alloys are also reviewed.

Nano-fabrication with metallic glass-an exotic material for nano-electromechanical systems.

Abstract: Completely glassy thin films of Zr-Al-Cu-Ni exhibiting a large supercooled liquid region (DeltaT(x) = 95 K), very smooth surface (R(a) = 0.2 nm) and high value of Vickers hardness (H(v) = 940) were deposited by sputtering. The micro/nano-patterning ability of these films is demonstrated by focused ion beam etching (smallest pattern approximately 12 nm), as well as by the imprint lithography technique (smallest feature approximately 34 nm). These glassy films having very good mechanical and chemical properties, combined with superb nano-patterning ability, integrateable with silicon integrated circuit technology, are promising for fabrication of a wide range of two- or three-dimensional components for future nano-electromechanical systems.