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Journal Articles

Observation of field-induced single-ion magnetic anisotropy in a multiorbital Kondo alloy (Lu,Yb)Rh$$_2$$Zn$$_{20}$$

Kitazawa, Takafumi; Ikeda, Yoichi*; Sakakibara, Toshiro*; Matsuo, Akira*; Shimizu, Yusei*; Tokunaga, Yo; Haga, Yoshinori; Kindo, Koichi*; Nambu, Yusuke*; Ikeuchi, Kazuhiko*; et al.

Physical Review B, 108(8), p.085105_1 - 085105_7, 2023/08

Journal Articles

Structure of nitride layer formed on titanium alloy surface by N$$_{2}$$-gas exposure at high temperatures

Takeda, Yusuke; Iida, Kiyoshi*; Sato, Shinji*; Matsuo, Tadatoshi*; Nagashima, Yasuyuki*; Okubo, Nariaki; Kondo, Keietsu; Hirade, Tetsuya

JPS Conference Proceedings (Internet), 25, p.011023_1 - 011023_3, 2019/03

In this study, we prepared samples under two different conditions, (1) 810$$^{circ}$$C, for 600 min, and (2) 850$$^{circ}$$C, for 720 min. A depth-profile analysis of the surfaces of the samples is conducted through Doppler broadening (DB) measurements of positron annihilation $$gamma$$ rays using a slow positron beam. It was indicated that many of positrons annihilated in defects near the surface. According to the TEM image, there are nano-crystal grains near the surface and then positrons can diffuse in the grains and annihilate in defects at the grain boundaries. Furthermore, DB measurements indicated that there is a depth dependence on the chemical composition where positrons annihilate. EDS spectroscopy measurements also indicated that there is a depth dependence of impurities such as Vanadium. These results indicated change of the chemical composition at the grain boundaries.

Journal Articles

Structure of nitride layer formed on titanium alloy surface by N$$_{2}$$-gas exposure at high temperatures

Takeda, Yusuke; Iida, Kiyoshi*; Sato, Shinji*; Matsuo, Tadatoshi*; Nagashima, Yasuyuki*; Okubo, Nariaki; Kondo, Keietsu; Hirade, Tetsuya

Journal of Physics; Conference Series, 791(1), p.012022_1 - 012022_4, 2017/02

 Times Cited Count:1 Percentile:41.91(Physics, Multidisciplinary)

Titanium alloy is widely used for applications such as golf club heads and structural materials for aircrafts. The surface can be exceedingly hardened by nitriding treatment that initiates defects, but there are some difficulties on use of titanium nitride because the layer can be exfoliated by stress. Therefore, we prepared samples in two different treatment conditions, (1) 810$$^{circ}$$C 600 min and (2) 850$$^{circ}$$C 720 min and performed depth profile analysis of Doppler broadening of positron annihilation $$gamma$$-rays (DB) for these samples. According to a calculation of nitrogen diffusion depth, the nitride layer should be only about 0.05-0.1$$mu$$m. However, the depth profile analysis of the DB measurement indicated that the defects introduced by nitriding treatment extended to a depth of 0.5$$mu$$m.

Journal Articles

Isoscalar giant resonances in the Sn nuclei and implications for the asymmetry term in the nuclear-matter incompressibility

Li, T.*; Garg, U.*; Liu, Y.*; Marks, R.*; Nayak, B. K.*; Madhusudhana Rao, P. V.*; Fujiwara, Mamoru*; Hashimoto, Hisanobu*; Nakanishi, Kosuke*; Okumura, Shun*; et al.

Physical Review C, 81(3), p.034309_1 - 034309_11, 2010/03

 Times Cited Count:107 Percentile:97.52(Physics, Nuclear)

Journal Articles

Magnetic and dielectric properties of YbFe$$_{2-x}$$Mn$$_{x}$$O$$_{4}$$ (0$$underline{<}$$x$$underline{<}$$1)

Yoshii, Kenji; Ikeda, Naoshi*; Michiuchi, Takamasa*; Yokota, Yusuke*; Okajima, Yuka; Yoneda, Yasuhiro; Matsuo, Yoji*; Horibe, Yoichi*; Mori, Shigeo*

Journal of Solid State Chemistry, 182(7), p.1611 - 1618, 2009/06

 Times Cited Count:15 Percentile:51.37(Chemistry, Inorganic & Nuclear)

We have investigated the magnetic and dielectric properties of YbFe$$_{2-x}$$Mn$$_{x}$$O$$_{4}$$ (0$$underline{<}$$x$$underline{<}$$1), which is an Fe-site-substituted system of new multiferroic oxides RFe$$_{2}$$O$$_{4}$$ (R=Y, Ho-Lu). X-ray diffraction measurements show that a solid solution is formed between YbFe$$_{2}$$O$$_{4}$$ (x=0) and YbFeMnO$$_{4}$$ (x=1) for 0$$underline{<}$$x$$underline{<}$$1. The valence of the Mn ion is determined to be $$sim$$2+, consistently with the suppression of low-temperature magnetization by the Mn substitution. The magnetic transition temperature and the dielectric constant decrease monotonically with increasing x. This result plausibly confirms that the magnetic and dielectric properties in oxides isostructural with RFe$$_{2}$$O$$_{4}$$ are governed by the electron transfer between Fe-site ions, unlike ordinary ferroelectrics and dielectrics, in which the ionic displacement plays a key role. The possibility for application is briefly discussed.

Journal Articles

Stoichiometric study of the dielectric and magnetic properties in charge frustrated system LuFe$$_{2}$$O$$_{4}$$

Michiuchi, Takamasa*; Yokota, Yusuke*; Komatsu, Takuma*; Hayakawa, Hironori*; Kuroda, Tomoko*; Maeda, Daisuke*; Matsuo, Yoji*; Mori, Shigeo*; Yoshii, Kenji; Hanasaki, Noriaki*; et al.

Ferroelectrics, 378(1), p.175 - 180, 2009/00

 Times Cited Count:18 Percentile:59.55(Materials Science, Multidisciplinary)

We have synthesized the samples of LuFe$$_{2}$$O$$_{4}$$, which shows the ferroelectricity due to charge ordering of Fe ions, under several different reducing conditions using a CO$$_{2}$$-CO flow. The reducing condition was changed by changing a flow ratio of CO$$_{2}$$ and CO. It was found that the flow ratio of CO$$_{2}$$/CO of about 5 provided the sample with the highest magnetic transition temperature of 240-250 K. This sample showed the dielectric constant of 10000 at room temperature. The imaginary part of the dielectric response offered the activation energy of 0.4-0.5 eV, which is slightly larger than that reported previously (about 0.3 eV). We will perform further investigation of the physical properties of this sample to clarify full details and their origin of LuFe$$_{2}$$O$$_{4}$$.

Journal Articles

Magnetic and dielectric properties of HoFe$$_{2}$$O$$_{4}$$ and R$$_{1-x}$$R'$$_{x}$$Fe$$_{2}$$O$$_{4}$$ (R, R': rare earths)

Yoshii, Kenji; Yoneda, Yasuhiro; Maeda, Daisuke*; Yokota, Yusuke*; Michiuchi, Takamasa*; Komatsu, Takuma*; Ikeda, Naoshi*; Matsuo, Yoji*; Mori, Shigeo*

Japanese Journal of Applied Physics, 47(9), p.7599 - 7602, 2008/09

 Times Cited Count:8 Percentile:33.23(Physics, Applied)

We have investigated the physical properties of HoFe$$_{2}$$O$$_{4}$$ and R$$_{1-x}$$R'$$_{x}$$Fe$$_{2}$$O$$_{4}$$ (R, R': rare earths). Dielectric measurements showed their dielectric constants of 1000 at around room temperature, which is characteristic of the RFe$$_{2}$$O$$_{4}$$ series (R: rare earths). However, the magnetic transition temperatures and the coherency in dielectric response were found to be different from those of RFe$$_{2}$$O$$_{4}$$ reported so far. Interestingly, these materials suggested higher ferroelectric temperatures than those reported so far, suggesting a possibility of application of these materials.

Journal Articles

Hexafluoro complex of rutherfordium in mixed HF/HNO$$_{3}$$ solutions

Toyoshima, Atsushi; Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Akiyama, Kazuhiko*; Goto, Shinichi*; Ishii, Yasuo; Nishinaka, Ichiro; Sato, Tetsuya; Nagame, Yuichiro; et al.

Radiochimica Acta, 96(3), p.125 - 134, 2008/03

 Times Cited Count:29 Percentile:84.99(Chemistry, Inorganic & Nuclear)

Formation of an anionic fluoride-complex of element 104, rutherfordium (Rf) produced in the $$^{248}$$Cm($$^{18}$$O,5n)$$^{261}$$Rf reaction was studied by an anion-exchange method based on an atom-at-a-time scale. It was found that the hexafluoro complex of Rf, [RfF$$_{6}$$]$$^{2-}$$, was formed in the studied fluoride ion concentrations of 0.0005 - 0.013 M. Formation of [RfF$$_{6}$$]$$^{2-}$$ was significantly different from that of the homologues Zr and Hf, [ZrF$$_{6}$$]$$^{2-}$$ and [HfF$$_{6}$$]$$^{2-}$$; the evaluated formation constant of [RfF$$_{6}$$]$$^{2-}$$ is at least one-order of magnitude smaller than those of [ZrF$$_{6}$$]$$^{2-}$$ and [HfF$$_{6}$$]$$^{2-}$$.

Journal Articles

Extraction behavior of rutherfordium into tributylphosphate from hydrochloric acid

Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Ishii, Yasuo; Tome, Hayato; Sato, Tetsuya; Nishinaka, Ichiro; Ichikawa, Takatoshi; Ichikawa, Shinichi; et al.

Radiochimica Acta, 95(1), p.1 - 6, 2007/01

 Times Cited Count:16 Percentile:70.17(Chemistry, Inorganic & Nuclear)

no abstracts in English

Journal Articles

Chemical studies on rutherfordium (Rf) at JAERI

Nagame, Yuichiro; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko; Ishii, Yasuo; Sato, Tetsuya; Hirata, Masaru; Nishinaka, Ichiro; Ichikawa, Shinichi; et al.

Radiochimica Acta, 93(9-10), p.519 - 526, 2005/00

 Times Cited Count:31 Percentile:87.03(Chemistry, Inorganic & Nuclear)

no abstracts in English

Oral presentation

Formation of anionic chloride complex of Rutherfordium (Rf)

Tsukada, Kazuaki; Toyoshima, Atsushi; Haba, Hiromitsu*; Asai, Masato; Akiyama, Kazuhiko*; Ishii, Yasuo; Tome, Hayato*; Nishinaka, Ichiro; Sato, Tetsuya; Ichikawa, Takatoshi; et al.

no journal, , 

no abstracts in English

Oral presentation

TBP reversed-phase extraction chromatography of Rutherfordium in the HCl solution

Toyoshima, Atsushi; Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Akiyama, Kazuhiko*; Ishii, Yasuo; Tome, Hayato*; Nishinaka, Ichiro; Sato, Tetsuya; Ichikawa, Takatoshi; et al.

no journal, , 

no abstracts in English

Oral presentation

Chloride complex formation of Rf in HCl and CH$$_{3}$$OH mixed solution

Tsukada, Kazuaki; Toyoshima, Atsushi; Haba, Hiromitsu*; Asai, Masato; Akiyama, Kazuhiko*; Ishii, Yasuo; Tome, Hayato; Nishinaka, Ichiro; Sato, Tetsuya; Ichikawa, Shinichi; et al.

no journal, , 

no abstracts in English

Oral presentation

Analysis of surface structure of titanium alloy nitride by slow positron beam

Takeda, Yusuke; Iida, Kiyoshi*; Sato, Shinji*; Matsuo, Tadatoshi*; Nagashima, Yasuyuki*; Okubo, Nariaki; Kondo, Keietsu; Hirade, Tetsuya

no journal, , 

The impact stress exfoliates a Nitride surface layer on Titanium alloy prepared in some conditions. So we prepared specimens in two different conditions, (1) 810$$^{circ}$$C, 600min and (2) 850$$^{circ}$$C, 720min, and performed depth profile analysis of their surfaces with Doppler broadening measurements of positron annihilation $$gamma$$-rays (DB) that is sensitive for defects by Slow Positron beams. Although the specimens (2) is harder than (1) according to the Vickers Hardness test, DB results indicated that defect layer of specimen (1) is thicker than (2). It means that the defect layer thickness was not the cause of surface hardening. Furthermore, chemical elements at the positron annihilation sites could be analyzed qualitatively by DB and the change of the composition appeared in deeper region than the defect layer. The defect layer depth does not match the depth where chemical composition changes by DB appeared. TEM and EDS observation showed different tendency from the results by DB. It is because positrons probe specific sites, and the combination of these methods will be a strong tool to investigate surface structures.

Oral presentation

Heat capacity measurements of cement materials

Sasada, Yuto*; Miyazaki, Yuji*; Nakano, Motohiro*; Matsuo, Yusuke*; Walker, C.*; Sasamoto, Hiroshi; Mihara, Morihiro

no journal, , 

Cementitous materials are to be used in large quantities in the geological disposal of highly radioactive TRU waste. Thermodynamic data on cement hydrate minerals are important to model the long-term dissolution behavior of cement materials during the reaction of these materials with groundwater. Portlandite (Ca(OH)$$_{2}$$) is a major component (20 to 25 wt%) of hydrated Portland cement. Low temperature heat capacity measurements of three types of portlandite (low purity, high purity, and large crystal) showed purity dependence. The large crystal sample followed Debye's T$$^{3}$$ rule at low temperatures, while the high and low purity samples showed upturn of heat capacity, possibly due to difference in absorbed water vapor and/or calcite (CaCO$$_{3}$$) contamination. Heat capacities of the cement hydrates (ettringite:Ca$$_{6}$$(Al(OH)$$_{6}$$)$$_{2}$$(SO$$_{4}$$)$$_{3}$$(H$$_{2}$$O)$$_{n}$$ and monosulfate:Ca$$_{4}$$Al$$_{2}$$(OH)$$_{12}$$(SO$$_{4}$$)(H$$_{2}$$O)$$_{n}$$) exhibited phase transitions associated with the hydration water.

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