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Journal Articles

Analysis of atomistic structural deformation characteristics of calcium silicate hydrate in 53-year-old tricalcium silicate paste using atomic pair distribution function

Bae, S.*; Jee, H.*; Suh, H.*; Kanematsu, Manabu*; Shiro, Ayumi*; Machida, Akihiko*; Watanuki, Tetsu*; Shobu, Takahisa; Morooka, Satoshi; Geng, G.*; et al.

Construction and Building Materials, 237, p.117714_1 - 117714_10, 2020/03

 Times Cited Count:1 Percentile:100(Construction & Building Technology)

Journal Articles

Pair distribution function analysis of nanostructural deformation of calcium silicate hydrate under compressive stress

Bae, S.*; Jee, H.*; Kanematsu, Manabu*; Shiro, Ayumi*; Machida, Akihiko*; Watanuki, Tetsu*; Shobu, Takahisa; Suzuki, Hiroshi

Journal of the American Ceramic Society, 101(1), p.408 - 418, 2018/01

 Times Cited Count:6 Percentile:41.07(Materials Science, Ceramics)

Despite enormous interest in calcium silicate hydrate (C-S-H), its detailed atomic structure and intrinsic deformation under an external load are lacking. This study demonstrates the nanostructural deformation process of C-S-H in tricalcium silicate (C$$_{3}$$S) paste as a function of applied stress by interpreting atomic pair distribution function (PDF) based on in situ X-ray scattering. Three different strains in C$$_{3}$$S paste under compression were compared using a strain gauge and the real and reciprocal space PDFs. PDF refinement revealed that the C-S-H phase mostly contributed to PDF from 0 to 20${AA}$ whereas crystalline phases dominated that beyond 20${AA}$. The short-range atomic strains exhibited two regions for C-S-H: I) plastic deformation (0-10 MPa) and II) linear elastic deformation ($$>$$10 MPa), whereas the long-range deformation beyond 20${AA}$ was similar to that of Ca(OH)$$_{2}$$. Below 10 MPa, the short-range strain was caused by the densification of C-S-H induced by the removal of interlayer or gel-pore water. The strain is likely to be recovered when the removed water returns to C-S-H.

Journal Articles

Maximizing $$T_c$$ by tuning nematicity and magnetism in FeSe$$_{1-x}$$S$$_x$$ superconductors

Matsuura, Kohei*; Mizukami, Yuta*; Arai, Yuki*; Sugimura, Yuichi*; Maejima, Naoyuki*; Machida, Akihiko*; Watanuki, Tetsu*; Fukuda, Tatsuo; Yajima, Takeshi*; Hiroi, Zenji*; et al.

Nature Communications (Internet), 8, p.1143_1 - 1143_6, 2017/10

 Times Cited Count:37 Percentile:9.91(Multidisciplinary Sciences)

Journal Articles

Mineralogical characterization of radioactive particles from Fukushima soil using $$mu$$-XRD with synchrotron radiation

Motai, Satoko*; Mukai, Hiroki*; Watanuki, Tetsu; Owada, Kenji; Fukuda, Tatsuo; Machida, Akihiko; Kuramata, Chisaki*; Kikuchi, Ryosuke*; Yaita, Tsuyoshi; Kogure, Toshihiro*

Journal of Mineralogical and Petrological Sciences, 111(5), p.305 - 312, 2016/10

 Times Cited Count:11 Percentile:38.29(Mineralogy)

no abstracts in English

Journal Articles

Investigation of elastic deformation mechanism in as-cast and annealed eutectic and hypoeutectic Zr-Cu-Al metallic glasses by multiscale strain analysis

Suzuki, Hiroshi; Yamada, Rui*; Tsubaki, Shinki*; Imafuku, Muneyuki*; Sato, Shigeo*; Watanuki, Tetsu; Machida, Akihiko; Saida, Junji*

Metals, 6(1), p.12_1 - 12_11, 2016/01

 Times Cited Count:2 Percentile:78.91(Materials Science, Multidisciplinary)

Elastic deformation behaviors of as-cast and annealed eutectic and hypoeutectic Zr-Cu-Al bulk metallic glasses (BMGs) were investigated on a basis of different strain-scales determined by X-ray scattering and the strain gauge. The microscopic strains determined by Direct-space method (DSM) and Q-space method (QSM) were compared with the macroscopic strain measured by the strain gauge, and the difference in the deformation mechanism between eutectic and hypoeutectic Zr-Cu-Al BMGs was investigated by their correlation. The eutectic Zr$$_{50}$$Cu$$_{40}$$Al$$_{10}$$ BMG obtains more homogeneous microstructure by free-volume annihilation after annealing, improving a resistance to deformation but degrading ductility because of a decrease in the volume fraction of WBRs (Weakly-Bonded Regions) with relatively high mobility. On the other hand, the as-cast hypoeutectic Zr$$_{60}$$Cu$$_{30}$$Al$$_{10}$$ BMG originally has homogeneous microstructure, but loses its structural and elastic homogeneities because of nanocluster formation after annealing. Such structural changes after annealing might develop unique mechanical properties showing no degradations of ductility and toughness for the structural-relaxed hypoeutectic BMGs.

Journal Articles

Melting of Pb charge glass and simultaneous Pb-Cr charge transfer in PbCrO$$_{3}$$ as the origin of volume collapse

Yu, R.*; Hojo, Hajime*; Watanuki, Tetsu; Mizumaki, Masaichiro*; Mizokawa, Takashi*; Oka, Kengo*; Kim, H.*; Machida, Akihiko; Sakaki, Koji*; Nakamura, Yumiko*; et al.

Journal of the American Chemical Society, 137(39), p.12719 - 12728, 2015/10

 Times Cited Count:15 Percentile:45.43(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Thermal expansion of a Au-Al-Yb intermediate valence quasicrystal

Watanuki, Tetsu; Kashimoto, Shiro*; Ishimasa, Tsutomu*; Machida, Akihiko; Yamamoto, Shin*; Tanaka, Yukinori*; Mizumaki, Masaichiro*; Kawamura, Naomi*; Watanabe, Shinji*

Solid State Communications, 211, p.19 - 22, 2015/06

 Times Cited Count:3 Percentile:79.82(Physics, Condensed Matter)

The thermal expansion of a Au-Al-Yb intermediate-valence quasicrystal has been studied by X-ray diffraction measurements. We have found anomalous thermal expansion behavior, namely zero thermal expansion below 50 K. By comparison with an isostructural Au-Al-Tm quasicrystal, the contribution of the Yb valence variation was extracted, and it was shown that its negative thermal expansion component due to the valence shift toward the divalent state by cooling compensated for the positive thermal expansion of the original lattice.

Journal Articles

New PbTiO$$_{3}$$-type giant tetragonal compound Bi$$_{2}$$ZnVO$$_{6}$$ and its stability under pressure

Yu, R.*; Hojo, Hajime*; Oka, Kengo*; Watanuki, Tetsu; Machida, Akihiko; Shimizu, Keisuke*; Nakano, Kiho*; Azuma, Masaki*

Chemistry of Materials, 27(6), p.2012 - 2017, 2015/03

 Times Cited Count:18 Percentile:35.73(Chemistry, Physical)

no abstracts in English

Journal Articles

X-ray absorption spectroscopy and novel electronic properties in heavy fermion compounds YbT$$_{2}$$Zn$$_{20}$$ (T: Rh and Ir)

Honda, Fuminori*; Hirose, Yusuke*; Miyake, Atsushi*; Mizumaki, Masaichiro*; Kawamura, Naomi*; Tsutsui, Satoshi*; Watanuki, Tetsu; Watanabe, Shinji*; Takeuchi, Tetsuya*; Settai, Rikio*; et al.

Journal of Physics; Conference Series, 592(1), p.012021_1 - 012021_5, 2015/03

 Times Cited Count:1 Percentile:50.19

no abstracts in English

Journal Articles

Compositional dependence of hydrogenation properties in Ti$$_{1+y}$$(Fe$$_{1-x}$$Mn$$_{x}$$)$$_{1-y}$$ ($$0.2 leq x leq 0.5$$, $$0 leq y leq 0.08$$)

Sakaki, Koji*; Kim, H.*; Machida, Akihiko; Watanuki, Tetsu; Nakamura, Yumiko*

Nippon Kinzoku Gakkai-Shi, 79(3), p.112 - 117, 2015/03

 Times Cited Count:0 Percentile:100(Metallurgy & Metallurgical Engineering)

no abstracts in English

Journal Articles

Effect of a quenching rate on hydrogen storage properties of V$$_{0.79}$$Ti$$_{0.2}$$Zr$$_{0.01}$$

Kim, H.*; Sakaki, Koji*; Asano, Kota*; Ikeda, Kazutaka*; Otomo, Toshiya*; Machida, Akihiko; Watanuki, Tetsu; Nakamura, Yumiko*

Nippon Kinzoku Gakkai-Shi, 79(3), p.131 - 136, 2015/03

 Times Cited Count:0 Percentile:100(Metallurgy & Metallurgical Engineering)

no abstracts in English

Journal Articles

Structure refinement for the $$alpha$$-$$varepsilon$$ transition of iron by using EXAFS

Ishimatsu, Naoki*; Sata,Yusuke*; Maruyama, Hiroshi*; Watanuki, Tetsu; Kawamura, Naomi*; Mizumaki, Masaichiro*; Irifune, Tetsuo*; Sumiya, Hitoshi*

Hoshako, 28(1), p.3 - 11, 2015/01

no abstracts in English

Journal Articles

Improvement of hydrogen storage properties of Mg$$_{1-x}$$Pr$$_{x}$$Ni$$_{4}$$ by Changing Mg/Pr ratio

Sakaki, Koji*; Terashita, Naoyoshi*; Kim, H.*; Majzoub, E. H.*; Proffen, T.*; Machida, Akihiko; Watanuki, Tetsu; Tsunokake, Shigeru*; Nakamura, Yumiko*; Akiba, Etsuo*

Sumato Purosesu Gakkai-Shi, 3(6), p.359 - 366, 2014/11

no abstracts in English

Journal Articles

Reduction and unusual recovery in the reversible hydrogen storage capacity of V$$_{1-x}$$Ti$$_x$$ during hydrogen cycling

Kim, H.*; Sakaki, Koji*; Saita, Itoko*; Enoki, Hirotoshi*; Noguchi, Kazuo*; Machida, Akihiko; Watanuki, Tetsu; Nakamura, Yumiko*

International Journal of Hydrogen Energy, 39(20), p.10546 - 10551, 2014/07

 Times Cited Count:9 Percentile:69.63(Chemistry, Physical)

The effect of the vanadium content on the cyclic stability of V-Ti binary alloys was investigated. V$$_{1-x}$$Ti$$_x$$, $$x=$$ 0.2 and 0.5 samples were hydrogenated and dehydrogenated at 410 K and 553 K respectively, for more than 100 times. During hydrogen cycling, reduction in the reversible hydrogen storage capacity was clearly observed from both samples. In addition, the shape of the pressure-composition-isotherm curves was significantly altered over the testing cycle period; the absorption and desorption plateaus got markedly inclined and the hysteresis became evidently smaller. We found that even after the hydrogen storage capacity of V$$_{1-x}$$Ti$$_x$$ was significantly reduced, at low enough temperature V$$_{1-x}$$Ti$$_x$$ was able to absorb hydrogen as much as it did at the first cycle.

Journal Articles

Disproportionation reaction of LaH$$_2$$ at high pressure and low temperature

Machida, Akihiko; Watanuki, Tetsu; Kawana, Daichi*; Aoki, Katsutoshi

Journal of Physics; Conference Series, 500(2), p.022001_1 - 022001_5, 2014/05

 Times Cited Count:0 Percentile:100

We found that LaH$$_2$$ decomposed into two different molar-volume phases at 11 GPa at room temperature through synchrotron radiation X-ray diffraction (SR-XRD) measurements. Observed decomposition suggests that the H-poor and H-rich phases are spontaneously formed by pressurization, namely, a pressure-induced disproportionation reaction. Observed disproportionation reaction accompanies the transfer of the H atoms between the interstitial sites. Diffusivity of the H atoms suppresses as the temperature decreases. Hence we have investigated this disproportionation of LaH$$_2$$ in the low H diffusivity case at low temperature.SR-XRD measurements at high pressure and low temperature were carried out at BL22XU, SPring-8. We found the disproportionation at 13.5 GPa even at 200 K. The volume fraction of the H-poor phase at 200 K is larger than that at room temperature. The disproportionation at low temperature will be discussed on the basis of the X-ray diffraction data.

Journal Articles

Degradation mechanism against hydrogenation cycles in Mg$$_{2-x}$$Pr$$_x$$Ni$$_4$$ ($$x$$ = 0.6 and 1.0)

Sakaki, Koji*; Terashita, Naoyoshi*; Kim, H.*; Majzoub, E. H.*; Machida, Akihiko; Watanuki, Tetsu; Tsunokake, Shigeru*; Nakamura, Yumiko*; Akiba, Etsuo*

Journal of Physical Chemistry C, 118(13), p.6697 - 6705, 2014/04

 Times Cited Count:11 Percentile:54.51(Chemistry, Physical)

We present an investigation of the degradation mechanism against hydrogenation cycles in Mg$$_{2-x}$$Pr$$_x$$Ni$$_4$$ ($$x$$ = 0.6 and 1.0). Mg$$_{1.0}$$Pr$$_{1.0}$$Ni$$_{4}$$ shows significant degradation and loss of capacity after only a few cycles, while Mg$$_{1.4}$$Pr$$_{0.6}$$Ni$$_{4}$$ did not show any reduction of hydrogen storage capacity until 100 cycles. The peak broadening of X-ray diffraction patterns and accumulation of lattice strain were observed concomitantly with an increase of hydrogenation cycles only in Mg$$_{1.0}$$Pr$$_{1.0}$$Ni$$_{4}$$. These changes were not observed in Mg$$_{1.4}$$Pr$$_{0.6}$$Ni$$_{4}$$. In pair distribution function patterns, $$r$$-dependent peak broadening was observed and it became significant with an increasing number of cycles in Mg$$_{1.0}$$Pr$$_{1.0}$$Ni$$_{4}$$, suggesting an increase of the dislocation density. Mg$$_{1.4}$$Pr$$_{0.6}$$Ni$$_{4}$$ showed higher hardness and more pulverization upon hydrogenation than Mg$$_{1.0}$$Pr$$_{1.0}$$Ni$$_{4}$$.

Journal Articles

Momentum-resolved resonant inelastic X-ray scattering on a single crystal under high pressure

Yoshida, Masahiro*; Ishii, Kenji; Jarrige, I.*; Watanuki, Tetsu; Kudo, Kazutaka*; Koike, Yoji*; Kumagai, Kenichi*; Hiraoka, Nozomu*; Ishii, Hirofumi*; Tsuei, K.-D.*; et al.

Journal of Synchrotron Radiation, 21(1), p.131 - 135, 2014/01

 Times Cited Count:3 Percentile:75.87(Instruments & Instrumentation)

Journal Articles

Origin of degradation in the reversible hydrogen storage capacity of V$$_{1-x}$$Ti$$_{x}$$ alloys from the atomic pair distribution function analysis

Kim, H.*; Sakaki, Koji*; Ogawa, Hiroshi*; Nakamura, Yumiko*; Nakamura, Jin*; Akiba, Etsuo*; Machida, Akihiko; Watanuki, Tetsu; Proffen, T.*

Journal of Physical Chemistry C, 117(50), p.26543 - 26550, 2013/12

 Times Cited Count:27 Percentile:27.21(Chemistry, Physical)

Reduction in reversible hydrogen storage capacity with increasing hydrogenation and dehydrogenation cycle number is observed in numerous hydrogen storage materials, but the mechanism behind this unfavorable change has not been elucidated yet. In this study, we have investigated the development of structural defects or disorders in V$$_{1-x}$$Ti$$_x$$H$$_2$$, $$x$$ = 0, 0.2, and 0.5, during the first 15 hydrogen absorption and desorption cycles using the atomic pair distribution function (PDF) analysis of synchrotron X-ray total scattering data to find out the possible structural origin of the poor cyclic stability of V$$_{1-x}$$Ti$$_x$$ alloys.

Journal Articles

Formation of NaCl-type lanthanum monohydride under high pressure; Discovery of novel rare-earth metal hydride using synchrotron radiation X-ray and neutron

Machida, Akihiko; Honda, Mitsunori*; Hattori, Takanori; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Oshita, Hidetoshi*; Ikeda, Kazutaka*; Otomo, Toshiya*

Hamon, 23(2), p.131 - 136, 2013/05

Recently, we have revealed formation of NaCl-type LaD using synchrotron radiation X-ray diffraction and neutron diffraction measurements under high pressure. Previously, we have found that LaH$$_2$$ decomposes into two phases,which have different hydrogen compositions, the H-poor and H-rich phases, at 11 GPa at room temperature by synchrotron radiation X-ray diffraction. Recent neutron diffraction measurements on LaD$$_2$$ confirmed the formation of a NaCl-type LaD as the D-poor phase. This is the first observation of a formation of the rare-earth metal monodeuteride. Present result indicates that that rare-earth metal can form a series of stoichiometric hydrides,such as mono-, di-, and trihydride with the fcc metal lattice.

Journal Articles

Formation of an Fe-H complex anion in YFe$$_{2}$$; Adjustment of imbalanced charge by additional Li as an electron donor

Matsuo, Motoaki*; Saito, Hiroyuki; Machida, Akihiko; Sato, Ryutaro*; Takagi, Shigeyuki*; Miwa, Kazutoshi*; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Orimo, Shinichi*

RSC Advances (Internet), 3(4), p.1013 - 1016, 2013/01

 Times Cited Count:16 Percentile:43.91(Chemistry, Multidisciplinary)

166 (Records 1-20 displayed on this page)