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Your search keyword '"Tomoharu Tokunaga"' showing total 4 results
Start Over Author "Tomoharu Tokunaga" Journal materials transactions
4 results on '"Tomoharu Tokunaga"'

2. Apparent Sintering Activation Energy Estimated by Master Sintering Curves for 8 mol% Y2O3 Doped ZrO2 Polycrystals during Shrinkage-Rate Controlled Flash Sintering.

Author

Masao Koike, Ayu Kodaira, Tomoharu Tokunaga, and Takahisa Yamamoto

Subjects
POLYCRYSTALS, SINTERING, KIRKENDALL effect, SPECIFIC gravity, MICROWAVE sintering, ACTIVATION energy, BIOACTIVE glasses, LOW temperatures
Abstract

The apparent activation energy of sintering for 8-mol%-Y2O3-doped ZrO2 during shrinkage-rate-controlled flash sintering was determined using a master sintering curve. The activation energy during SCF sintering was found to decrease from approximately 700 to 430 kJ/mol with density. The activation energy in a high-density region is approximately similar value of lattice diffusion, 460 kJ/mol. The relative density range over which the decrease in activation energy occurred during SCF sintering was smaller than during thermal sintering and further moved to a lower temperature range. The increase in shrinkage rate at lower temperatures that occurs during SCF sintering could be considered to be related to this decrease in activation energy. [ABSTRACT FROM AUTHOR]

Published
2023
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3. Environment-Sensitive Thermal Coarsening of Nanoporous Gold

Author

Takeshi Fujita, Satoko Kuwano-Nakatani, Daichi Umetsu, Katsuhiko Chiba, Yuta Yamamoto, Shigeo Arai, Nobuo Tanaka, Kazuki Uchisawa, Yu Kase, Mingwei Chen, Yusuke Kowata, and Tomoharu Tokunaga

Subjects
Materials science, Mechanics of Materials, Nanoporous, Mechanical Engineering, Thermal, General Materials Science, Nanotechnology, Condensed Matter Physics
Published
2015

4. Fabrication and Characterization of Supersaturated Al-Mg Alloys by Severe Plastic Deformation and Their Mechanical Properties

Author

Tomoharu Tokunaga, Kenji Kaneko, Tetsuro Hata, and Zenji Horita

Subjects
Supersaturation, Fabrication, Materials science, Mechanical Engineering, Alloy, Metallurgy, engineering.material, Condensed Matter Physics, Microstructure, Indentation hardness, Grain size, Mechanics of Materials, Transmission electron microscopy, engineering, General Materials Science, Severe plastic deformation
Abstract

Excess amount of Mg was intentionally added to fabricate supersaturated ultra-fine grained Al-Mg alloy by high pressure torsion (HPT). Their microstructures and mechanical properties were examined by X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and Vickers microhardness test. It was confirmed that the minimum grain size reached ~40 nm and maximum microhardness 292 Hv at the Mg content with 30 mass%. Further increase of the amount of Mg resulted the formation of β-Al 3 Mg 2 and decrease of microhardness.

Published
2009

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