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Journal Articles

Intrinsic factors responsible for brittle versus ductile nature of refractory high-entropy alloys

Tsuru, Tomohito; Han, S.*; Matsuura, Shutaro*; Chen, Z.*; Kishida, Kyosuke; Lobzenko, I.; Rao, S.*; Woodward, C.*; George, E.*; Inui, Haruyuki*

Nature Communications (Internet), 15, p.1706_1 - 1706_10, 2024/02

 Times Cited Count:0 Percentile:0(Multidisciplinary Sciences)

Refractory high-entropy alloys (RHEAs) have attracted attention because of their potential for use in ultrahigh-temperature applications. Unfortunately, their body-centered-cubic (BCC) crystal structures make them more brittle than the ductile and fracture-resistant face-centered-cubic (FCC) HEAs. RHEAs also display significantly lower creep strengths than a leading Ni-base superalloy and its FCC matrix. To overcome these drawbacks and develop RHEAs into viable structural materials, improved fundamental understanding is needed of factors that control strength and ductility. Here we investigate two model RHEAs, TiZrHfNbTa and VNbMoTaW, and show that the former is plastically compressible down to 77 K, whereas the latter is not below 298 K. We find that hexagonal close-packed (HCP) elements in TiZrHfNbTa lower its dislocation core energy, increase its lattice distortion, and lower its shear modulus relative to VNbMoTaW whose elements are all BCC, leading to the formers higher ductility and modulus-normalized yield strength. Consistent with our yield strength models, primarily screw dislocations are present in TiZrHfNbTa after deformation, but equal numbers of edge and screw segments in VNbTaMoW. Dislocation cores are compact in VNbTaMoW and extended in TiZrHfNbTa, and different macroscopic slip planes are activated in the two RHEAs, which we attribute to the concentration of HCP elements. Our findings demonstrate how electronic structure changes related to the ratio of HCP to BCC elements can be used to control strength, ductility, and slip behavior to develop the next generation of high-temperature materials for more efficient power plants and transportation.

Journal Articles

Model intercomparison of atmospheric $$^{137}$$Cs from the Fukushima Daiichi Nuclear Power Plant accident; Simulations based on identical input data

Sato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; Qu$'e$lo, D.*; et al.

Journal of Geophysical Research; Atmospheres, 123(20), p.11748 - 11765, 2018/10

 Times Cited Count:40 Percentile:84.89(Meteorology & Atmospheric Sciences)

A model intercomparison of the atmospheric dispersion of $$^{137}$$Cs emitted following the Fukushima Daiichi Nuclear Power Plant accident was conducted by 12 models to understand the behavior of $$^{137}$$Cs in the atmosphere. The same meteorological data, horizontal grid resolution, and an emission inventory were applied to all the models to focus on the model variability originating from the processes included in each model. The multi-model ensemble captured 40% of the observed $$^{137}$$Cs events, and the figure-of-merit in space for the total deposition of $$^{137}$$Cs exceeded 80. Our analyses indicated that the meteorological data were most critical for reproducing the $$^{137}$$Cs events. The results also revealed that the differences among the models were originated from the deposition and diffusion processes when the meteorological field was simulated well. However, the models with strong diffusion tended to overestimate the $$^{137}$$Cs concentrations.

Journal Articles

High-pressure radiative conductivity of dense silicate glasses with potential implications for dark magmas

Murakami, Motohiko*; Goncharov, A. F.*; Hirao, Naohisa*; Masuda, Ryo*; Mitsui, Takaya; Thomas, S. M.*; Bina, C. R.*

Nature Communications (Internet), 5, p.5428_1 - 5428_6, 2014/11

 Times Cited Count:19 Percentile:51.35(Multidisciplinary Sciences)

Journal Articles

Progress with DC photoemission electron sources

Dunham, B.*; Benson, S.*; Hernandez-Garcia, C.*; Suleiman, R.*; Nishimori, Nobuyuki; Rao, T.*; Yamamoto, Masahiro*

Proceedings of 50th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs (ERL '11) (Internet), p.10 - 29, 2011/10

Journal Articles

Current transient effect in N-channel 6H-SiC MOSFET induced by heavy ion irradiation

Lee, K. K.*; Laird, J. S.*; Oshima, Takeshi; Onoda, Shinobu; Hirao, Toshio; Ito, Hisayoshi

Materials Science Forum, 645-648, p.1013 - 1016, 2010/04

no abstracts in English

Journal Articles

Progress on the heating and current drive systems for ITER

Jacquinot, J.*; Albajar, F.*; Beaumont, B.*; Becoulet, A.*; Bonicelli, T.*; Bora, D.*; Campbell, D.*; Chakraborty, A.*; Darbos, C.*; Decamps, H.*; et al.

Fusion Engineering and Design, 84(2-6), p.125 - 130, 2009/06

 Times Cited Count:24 Percentile:82.24(Nuclear Science & Technology)

The electron cyclotron (EC), ion cyclotron (IC), neutral beam (NB) and, lower hybrid (LH) systems for ITER have been reviewed in 2007/2008 in light of progress of physics and technology. Although the overall specifications are unchanged, notable changes have been approved. Firstly, the full 73MW should be commissioned and available on a routine basis before the D/T phase. Secondly, the possibility to operate the NB at full power during the hydrogen phase requiring new shine through protection; IC with 2 antennas with increased robustness; 2 MW transmission systems to provide an easier upgrading of the EC power; the addition of a building dedicated to the RF power sources and to a testing facility for acceptance of diagnostics and heating port plugs. Thirdly, the need of a plan for developing, in time for the active phase, a CD system such as LH suitable for very long pulse operation of ITER was recognized.

Journal Articles

Hybridization between the conduction band and 3$$d$$ orbitals in the oxide-based diluted magnetic semiconductor In$$_{2-x}$$V$$_x$$O$$_3$$

Kobayashi, Masaki*; Ishida, Yukiaki*; Hwang, J. I.*; Song, G. S.*; Takizawa, Masaru*; Fujimori, Atsushi; Takeda, Yukiharu; Okochi, Takuo*; Okane, Tetsuo; Saito, Yuji; et al.

Physical Review B, 79(20), p.205203_1 - 205203_5, 2009/05

 Times Cited Count:7 Percentile:33.14(Materials Science, Multidisciplinary)

Journal Articles

The Role of ion track structure on high-injection carrier dynamics in high-speed Si and III-V optoelectronic sensers

Laird, J. S.*; Onoda, Shinobu; Hirao, Toshio; Edmonds, L.*; Oshima, Takeshi

IEEE Transactions on Nuclear Science, 54(6), p.2384 - 2393, 2007/12

 Times Cited Count:8 Percentile:51.13(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Design of electron cyclotron heating and current drive system of ITER

Kobayashi, Noriyuki; Bigelow, T.*; Bonicelli, T.*; Cirant, S.*; Denisov, G.*; Heidinger, R.*; Henderson, M.*; Hogge, J.-P.*; Piosczyk, B.*; Ramponi, G.*; et al.

AIP Conference Proceedings 933, p.413 - 416, 2007/10

Since the EDA 2001, Design of Electron Cyclotron Heating and Current Drive (ECH&CD) System have been modified due to progress of physics understanding and change of interface. Nominal RF power 20 MW is injected by four upper launchers or one equatorial launcher. RF beams are steered by a front steering mirror. DCHV power supply will be composed of IGBT pulse step modulators because of high frequency modulation and design flexibility to three different types of 170 GHz gyrotrons from three parties. The RF power is transmitted by 63.5 mm dia corrugated waveguide and switched by a waveguide switch between the upper launcher and the equatorial launcher. A start-up system for initial discharge is composed of three 127.5 GHz gyrotrons and dedicated DCHV power supply. Three of transmission lines are shared between 170 GHz and 127.5 GHz gyrotrons to inject start-up RF beam through the equatorial launcher. R&Ds for high power long pulse have been on-going to obtain a reliable ITER ECH&CD system.

Journal Articles

The Search for magnetic order in $$delta$$-Pu metal using muon spin relaxation

Heffner, R. H.; Oishi, Kazuki; Fluss, M. J.*; Morris, G. D.*; MacLaughlin, D. E.*; Shu, L.*; Chung, B. W.*; McCall, S. K.*; Bauer, E. D.*; Sarrao, J. L.*; et al.

Journal of Alloys and Compounds, 444-445, p.80 - 83, 2007/10

 Times Cited Count:8 Percentile:48.44(Chemistry, Physical)

We summarize the results of muon spin relaxation ($$mu$$SR) measurements carried out in$$alpha$$- and $$delta$$-Pu and in the superconducting state ofPuCoGa$$_5$$. In Pu metal, interest has centered on whether or not magnetic order exists in the hightemperature fcc $$delta$$ phase,The Pu metal studies were designed to search for evidence of magnetic ordering, andhave set the most stringent limits to date for the ordered moment. In PuCoGa$$_5$$ the temperature dependence of themagnetic penetration depth $$lambda$$(T) was investigated in a fresh sample and again in the same sampleafter 400 days of aging. We find $$lambda$$(T)$$propto$$ T for T $$<$$ Tc/2, indicating a line of nodes in thesuperconducting order parameter. Remarkably, the temperature dependence of $$lambda$$(T) is littlechanged even after significant radiation damage.

Journal Articles

Transient currents generated by heavy ions with hundreds of MeV

Onoda, Shinobu; Hirao, Toshio; Laird, J. S.*; Mishima, Kenta; Kawano, Katsuyasu*; Ito, Hisayoshi

IEEE Transactions on Nuclear Science, 53(6), p.3731 - 3737, 2006/12

 Times Cited Count:16 Percentile:72.68(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Comparison of above bandgap laser and MeV ion induced single event transients in high-speed Si photonic devices

Laird, J. S.*; Hirao, Toshio; Onoda, Shinobu; Ito, Hisayoshi; Johnston, A.*

IEEE Transactions on Nuclear Science, 53(6), p.3312 - 3320, 2006/12

 Times Cited Count:14 Percentile:68.04(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Effects of $$gamma$$ and heavy ion damage on the impulse response and pulsed gain of a low breakdown voltage Si avalanche photodiode

Laird, J. S.*; Onoda, Shinobu; Hirao, Toshio; Ito, Hisayoshi; Becker, H.*; Johnston, A.*

IEEE Transactions on Nuclear Science, 53(6), p.3786 - 3793, 2006/12

 Times Cited Count:10 Percentile:56.9(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Effects of $$gamma$$ and heavy ion damage on the time-resolved gain of a low breakdown voltage Si avalanche photodiode

Laird, J. S.*; Onoda, Shinobu; Hirao, Toshio; Becker, H.*; Johnston, A.*; Ito, Hisayoshi

Proceedings of 7th International Workshop on Radiation Effects on Semiconductor Devices for Space Application (RASEDA-7), p.37 - 40, 2006/10

no abstracts in English

Journal Articles

Limits for ordered magnetism in Pu from muon spin rotation spectroscopy

Heffner, R. H.; Morris, G. D.*; Fluss, M. J.*; Chung, B.*; McCall, S.*; MacLaughlin, D. E.*; Shu, L.*; Oishi, Kazuki; Bauer, E. D.*; Sarrao, J. L.*; et al.

Physical Review B, 73(9), p.094453_1 - 094453_5, 2006/03

 Times Cited Count:33 Percentile:77.08(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Heavy ion and pulsed laser SET measurements in ultrahigh speed MSM GaAs photodetectors

Laird, J. S.; Hirao, Toshio; Onoda, Shinobu; Ito, Hisayoshi

IEEE Transactions on Nuclear Science, 52(5), p.1504 - 1512, 2005/10

 Times Cited Count:7 Percentile:44.84(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

High-injection carrier dynamics generated by MeV heavy ions impacting high-speed photodetectors

Laird, J. S.; Hirao, Toshio; Onoda, Shinobu; Ito, Hisayoshi

Journal of Applied Physics, 98(1), p.013530_1 - 013530_14, 2005/07

 Times Cited Count:45 Percentile:80.53(Physics, Applied)

no abstracts in English

Journal Articles

Characterization of charge generated in silicon carbide n$$^{+}$$p diodes using transient ion beam-induced current

Oshima, Takeshi; Sato, Takahiro; Oikawa, Masakazu*; Yamakawa, Takeshi; Onoda, Shinobu; Wakasa, Takeshi; Laird, J. S.; Hirao, Toshio; Kamiya, Tomihiro; Ito, Hisayoshi; et al.

Nuclear Instruments and Methods in Physics Research A, 541(1-2), p.236 - 240, 2005/04

 Times Cited Count:9 Percentile:55.92(Instruments & Instrumentation)

In order to develop particle detectors based on SiC semiconductor, SiC pn-diodes were irradiated with microbeam of 15MeV oxygen ions. The transient current was measured using the single ion hit transient ion beam induced current (TIBIC) system at TIARA. As the results, peak intensity of transient current induded by ion irradiation increased and falltime decreased with increasing applied bias. By the integration of transient current, the charge collection was estimated. It was found that charges generated in deeper region beyond the depletion layer can be collected by the funneling effect.

Journal Articles

Analysis of transient ion beam induced current in Si PIN Photodiode

Onoda, Shinobu; Hirao, Toshio; Laird, J. S.; Okamoto, Tsuyoshi*; Koizumi, Yoshiharu*; Kamiya, Tomihiro

Nuclear Instruments and Methods in Physics Research B, 231(1-4), p.497 - 501, 2005/04

 Times Cited Count:3 Percentile:30.25(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Anomalous gain mechanisms during single ion hit in avalanche photodiodes

Laird, J. S.; Hirao, Toshio; Onoda, Shinobu; Wakasa, Takeshi; Yamakawa, Takeshi; Abe, Hiroshi; Oyama, Hidenori*; Kamiya, Tomihiro

JAERI-Review 2004-025, TIARA Annual Report 2003, p.14 - 16, 2004/11

no abstracts in English

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