The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Yukichi Umakoshi - One of the best experts on this subject based on the ideXlab platform.
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Electron Irradiation induced crystallization and amorphization in Fe77Nd4.5B18.5 metallic glass
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Akihiro Nino, Takeshi Nagase, Yukichi UmakoshiAbstract:Abstract Electron Irradiation induced phase transformation behavior in Fe 77 Nd 4.5 B 18.5 (number indicate at.%) metallic glass was investigated. The melt-spun amorphous phase could not keep the original structure under Electron Irradiation at 298 K. α-Fe, Nd 2 Fe 14 B and Fe 17 Nd 2 phases precipitated from the amorphous phase. There was a great difference in phase selection in a crystallization process between thermal annealing and Electron Irradiation. The Nd 2 Fe 14 B and Fe 17 Nd 2 intermetallic compounds transformed to an amorphous phase under Electron Irradiation at 121 K, while the amorphization of α-Fe solid solution did not occur. A unique nanocrystalline structure which cannot be realized by thermal crystallization was formed through Electron Irradiation induced crystallization and amorphization.
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Electron Irradiation induced nano-crystallization in Zr66.7Ni33.3 amorphous alloy and Zr60Al15Ni25 metallic glass
Intermetallics, 2007Co-Authors: Takeshi Nagase, Mitsuo Nakamura, Yukichi UmakoshiAbstract:Abstract Electron Irradiation induced phase transformation behavior of an amorphous phase in Zr66.7Ni33.3 alloy, and an amorphous phase or supercooled liquid in Zr60Al15Ni25 alloy was investigated. The amorphous phase could not maintain the original glassy structure under Electron Irradiation at 298 K, and f.c.c.-solid solution precipitated under Electron Irradiation in both alloys. The precipitation of C16-Zr2Ni, big-cube (metastable f.c.c.-based Zr2Ni intermetallic compound), Zr6Al2Ni and Zr5AlNi4 crystalline phases from an amorphous phase was not observed during Electron Irradiation induced crystallization. The amorphous phase in Zr60Al15Ni25 metallic glass shows the highest phase stability against Electron Irradiation induced crystallization among Zr66.7Cu33.3, Zr66.7Ni33.3, Zr65Al7.5Ni27.5, Zr60Al15Ni25 and Zr65Al7.5Ni10Cu17.5 alloys. In Zr60Al15Ni25 metallic glass, Electron Irradiation promoted the precipitation of f.c.c.-solid solution and Zr6Al2Ni crystalline phases from the supercooled liquid.
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Phase Transformation in Fe81.0Zr9.0B10.0 Metallic Glass during Thermal Annealing and Electron Irradiation
Isij International, 2006Co-Authors: Takeshi Nagase, Yukichi UmakoshiAbstract:Solid-state phase transitions in Fe 81 Zr 9 B 10 alloy were investigated focusing on crystallization and amorphization introduced by thermal process and mechanical process of Electron Irradiation. Melt-spun amorphous phase can not maintain their original structure under thermal heated state at 828 K and Electron Irradiation at 103 and 298 K, crystallization of this phase occurred. There was a great difference in crystallization behavior between thermal annealing and Electron Irradiation. Metastable α-Mn type crystalline phase precipitated through thermal crystallization, while nano-crystalline b.c.c. solid solution was formed through Electron Irradiation induced crystallization. The α-Mn type crystalline phase underwent solid-state amorphization by Electron Irradiation at 103 and 298 K. Both amorphization and crystallization were observed in Fe 81 Zr 9 B 10 alloy under Electron Irradiation in spite of same Irradiation conditions, resulting in the occurrence of crystal-to-amorphous-to-crystal (C-A-C) transition.
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Electron Irradiation Induced Phase Transformation in Nd2Fe14B Alloy
Materials Transactions, 2006Co-Authors: Akihiro Nino, Takeshi Nagase, Yukichi UmakoshiAbstract:Transformation and change in the microstructure of Nd2Fe14B compound under Electron Irradiation were examined. The Nd2Fe14B compound did not maintain its original structure under Electron Irradiation and was transformed to an amorphous phase through solid-state amorphization. With further Electron Irradiation, crystallization of the amorphous phase occurred forming a nano-crystalline structure. The phase selection of Electron Irradiation induced crystallization depended strongly on the Irradiation temperature; nanocrystalline � -Fe phase precipitated in the amorphous phase at 104 K, while a nanoduplex structure composed of � -Fe, compounds and residual amorphous phase was formed at 298 K. Electron Irradiation induced phase transformation is a very effective method to control the nanocrystalline structure in Fe-Nd-B alloy. [doi:10.2320/matertrans.47.1762]
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Control of a Nanocomposite Structure in Fe86Nd9B5 Alloy by Electron Irradiation
Materials Transactions, 2006Co-Authors: Akihiro Nino, Takeshi Nagase, Yukichi UmakoshiAbstract:Change in nanocomposite structure in rapidly solidified Fe 86 Nd 9 B 5 alloy during Electron Irradiation was investigated. Nanocrystalline structure composed of α-Fe, Fe 3 B, Nd 2 Fe 14 B and Nd 2 Fe 23 B 3 crystalline phases was formed by rapid solidification. Electron Irradiation can introduce amorphization of intermetallic compounds and crystallization of an amorphous phase, resulting in the formation of a novel nanocomposite structure in which α-Fe and Nd 2 Fe 14 B nanocrystals are embedded in the amorphous matrix. The mechanism of nanocomposite structure formation was discussed based on the phase stability of amorphous and crystalline phases under Electron Irradiation.
Pulickel M Ajayan - One of the best experts on this subject based on the ideXlab platform.
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metal semiconductor transition in single walled carbon nanotubes induced by low energy Electron Irradiation
Nano Letters, 2005Co-Authors: Aravind Vijayaraghavan, Kenichi Kanzaki, Saturo Suzuki, Yoshihiro Kobayashi, Hiroshi Inokawa, Pulickel M AjayanAbstract:We report the effect of low-energy (1 keV) Electron beam Irradiation on gated, three-terminal devices constructed from metallic single-walled carbon nanotubes. Pristine devices, which exhibited negligible gate voltage response at room temperature and metallic single-Electron transistor characteristics at low temperatures, when exposed to an Electron beam, exhibited ambipolar field effect transistor (room temperature) and single-Electron transistor (low temperature) characteristics. This metal-semiconductor transition is attributed to inhomogeneous electric fields arising from charging during Electron Irradiation.
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the formation annealing and self compression of carbon onions under Electron Irradiation
Chemical Physics Letters, 1997Co-Authors: F. Banhart, T Fuller, Ph Redlich, Pulickel M AjayanAbstract:Abstract Electron Irradiation-induced basal plane disordering in single- and multi-shell carbon nanotubes and onions is found to be inhibited at Irradiation temperatures above 300°C. Irradiation-induced defects anneal out due to the thermally activated migration of interstitials at elevated temperatures and leave behind perfectly coherent shells of high tensile stability. Continuous loss of atoms as a result of sputtering induces a surface tension which can be identified as the origin of the formation and self-compression of spherical concentric-shell carbon onions.
Takeshi Nagase - One of the best experts on this subject based on the ideXlab platform.
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Electron Irradiation induced crystallization and amorphization in Fe77Nd4.5B18.5 metallic glass
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Akihiro Nino, Takeshi Nagase, Yukichi UmakoshiAbstract:Abstract Electron Irradiation induced phase transformation behavior in Fe 77 Nd 4.5 B 18.5 (number indicate at.%) metallic glass was investigated. The melt-spun amorphous phase could not keep the original structure under Electron Irradiation at 298 K. α-Fe, Nd 2 Fe 14 B and Fe 17 Nd 2 phases precipitated from the amorphous phase. There was a great difference in phase selection in a crystallization process between thermal annealing and Electron Irradiation. The Nd 2 Fe 14 B and Fe 17 Nd 2 intermetallic compounds transformed to an amorphous phase under Electron Irradiation at 121 K, while the amorphization of α-Fe solid solution did not occur. A unique nanocrystalline structure which cannot be realized by thermal crystallization was formed through Electron Irradiation induced crystallization and amorphization.
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Electron Irradiation induced nano-crystallization in Zr66.7Ni33.3 amorphous alloy and Zr60Al15Ni25 metallic glass
Intermetallics, 2007Co-Authors: Takeshi Nagase, Mitsuo Nakamura, Yukichi UmakoshiAbstract:Abstract Electron Irradiation induced phase transformation behavior of an amorphous phase in Zr66.7Ni33.3 alloy, and an amorphous phase or supercooled liquid in Zr60Al15Ni25 alloy was investigated. The amorphous phase could not maintain the original glassy structure under Electron Irradiation at 298 K, and f.c.c.-solid solution precipitated under Electron Irradiation in both alloys. The precipitation of C16-Zr2Ni, big-cube (metastable f.c.c.-based Zr2Ni intermetallic compound), Zr6Al2Ni and Zr5AlNi4 crystalline phases from an amorphous phase was not observed during Electron Irradiation induced crystallization. The amorphous phase in Zr60Al15Ni25 metallic glass shows the highest phase stability against Electron Irradiation induced crystallization among Zr66.7Cu33.3, Zr66.7Ni33.3, Zr65Al7.5Ni27.5, Zr60Al15Ni25 and Zr65Al7.5Ni10Cu17.5 alloys. In Zr60Al15Ni25 metallic glass, Electron Irradiation promoted the precipitation of f.c.c.-solid solution and Zr6Al2Ni crystalline phases from the supercooled liquid.
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Phase Transformation in Fe81.0Zr9.0B10.0 Metallic Glass during Thermal Annealing and Electron Irradiation
Isij International, 2006Co-Authors: Takeshi Nagase, Yukichi UmakoshiAbstract:Solid-state phase transitions in Fe 81 Zr 9 B 10 alloy were investigated focusing on crystallization and amorphization introduced by thermal process and mechanical process of Electron Irradiation. Melt-spun amorphous phase can not maintain their original structure under thermal heated state at 828 K and Electron Irradiation at 103 and 298 K, crystallization of this phase occurred. There was a great difference in crystallization behavior between thermal annealing and Electron Irradiation. Metastable α-Mn type crystalline phase precipitated through thermal crystallization, while nano-crystalline b.c.c. solid solution was formed through Electron Irradiation induced crystallization. The α-Mn type crystalline phase underwent solid-state amorphization by Electron Irradiation at 103 and 298 K. Both amorphization and crystallization were observed in Fe 81 Zr 9 B 10 alloy under Electron Irradiation in spite of same Irradiation conditions, resulting in the occurrence of crystal-to-amorphous-to-crystal (C-A-C) transition.
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Electron Irradiation Induced Phase Transformation in Nd2Fe14B Alloy
Materials Transactions, 2006Co-Authors: Akihiro Nino, Takeshi Nagase, Yukichi UmakoshiAbstract:Transformation and change in the microstructure of Nd2Fe14B compound under Electron Irradiation were examined. The Nd2Fe14B compound did not maintain its original structure under Electron Irradiation and was transformed to an amorphous phase through solid-state amorphization. With further Electron Irradiation, crystallization of the amorphous phase occurred forming a nano-crystalline structure. The phase selection of Electron Irradiation induced crystallization depended strongly on the Irradiation temperature; nanocrystalline � -Fe phase precipitated in the amorphous phase at 104 K, while a nanoduplex structure composed of � -Fe, compounds and residual amorphous phase was formed at 298 K. Electron Irradiation induced phase transformation is a very effective method to control the nanocrystalline structure in Fe-Nd-B alloy. [doi:10.2320/matertrans.47.1762]
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Control of a Nanocomposite Structure in Fe86Nd9B5 Alloy by Electron Irradiation
Materials Transactions, 2006Co-Authors: Akihiro Nino, Takeshi Nagase, Yukichi UmakoshiAbstract:Change in nanocomposite structure in rapidly solidified Fe 86 Nd 9 B 5 alloy during Electron Irradiation was investigated. Nanocrystalline structure composed of α-Fe, Fe 3 B, Nd 2 Fe 14 B and Nd 2 Fe 23 B 3 crystalline phases was formed by rapid solidification. Electron Irradiation can introduce amorphization of intermetallic compounds and crystallization of an amorphous phase, resulting in the formation of a novel nanocomposite structure in which α-Fe and Nd 2 Fe 14 B nanocrystals are embedded in the amorphous matrix. The mechanism of nanocomposite structure formation was discussed based on the phase stability of amorphous and crystalline phases under Electron Irradiation.
John W Palmour - One of the best experts on this subject based on the ideXlab platform.
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impact of high energy Electron Irradiation on high voltage ni 4h sic schottky diodes
Applied Physics Letters, 2017Co-Authors: V V Kozlovski, A A Lebedev, M E Levinshtein, S L Rumyantsev, John W PalmourAbstract:We report the results of the high energy (0.9 MeV) Electron Irradiation impact on the electrical properties of high voltage Ni/4H-SiC Schottky diodes. Within the range of the Irradiation dose from 0.2 × 1016 cm−2 to 7 × 1016 cm−2, Electron Irradiation led to 6 orders of magnitude increase in the base resistance, appearance of slow relaxation processes at pico-ampere current range, and increase in the ideality factor.
David E Luzzi - One of the best experts on this subject based on the ideXlab platform.
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Electron Irradiation effects in single wall carbon nanotubes
Journal of Applied Physics, 2001Co-Authors: Brian W Smith, David E LuzziAbstract:We determine, with excellent agreement between theory and experiment, the behavior of single wall carbon nanotubes during uniform Electron Irradiation. Calculations utilizing known ejection threshold energies predict that an isolated nanotube will damage preferentially on surfaces that lie normal to the Electron beam. A minimum incident Electron energy of 86 keV is required to remove a carbon atom by a knock-on collision for this geometry. Higher Electron energies are required for any other geometry, and at energies exceeding 139 keV every atom on a nanotube is susceptible to ballistic ejection. Transmission Electron microscopy observations of nanotubes using 80–400 keV Electrons corroborate these conclusions. Based upon empirical observations, we also explain damage processes in nonisolated nanotubes.