Yamauchi, Hiroki; Metoki, Naoto; Watanuki, Ryuta*; Suzuki, Kazuya*; Fukazawa, Hiroshi; Chi, S.*; Fernandez-Baca, J. A.*
Journal of the Physical Society of Japan, 86(4), p.044705_1 - 044705_9, 2017/04
Neutron diffraction experiments have been carried out to characterize the magnetic structures and order parameters in an intermediate phase of NdB showing the successive phase transitions at K, K, and K. The observed patterns in phase II () are successfully explained by postulating a planar structure with static magnetic moments in the tetragonal -plane. We have found that the magnetic structure in phase II can be uniquely determined to be a linear combination of noncolinear "all-in/all-out"-type and "vortex"-type antiferromagnetic structures. We propose that the quadrupolar interaction holds the key to stabilizing the noncollinear magnetic structure and quadrupolar order. Here, the frustration in the Shastry - Sutherland lattice would play an essential role in suppressing the dominance of the magnetic interaction.
Sekine, Yurina; Endo, Hitoshi*; Iwase, Hiroki*; Takeda, Shigeo*; Mukai, Sadaatsu*; Fukazawa, Hiroshi; Littrell, K. C.*; Sasaki, Yoshihiro*; Akiyoshi, Kazunari*
Journal of Physical Chemistry B, 120(46), p.11996 - 12002, 2016/11
The detailed structure of a nanogel formed by self-association of cholesterol-bearing pullulans (CHP) was determined by contrast variation small-angle neutron scattering. The decomposition of scattering intensities into partial scattering functions of each CHP nanogel component, i.e., pullulan, cholesterol, and the cross-term between the pullulan and the cholesterol allows us to investigate the internal structure of the nanogel. The effective spherical radius of the skeleton formed by pullulan chains was found to be about 8.1 nm. In the CHP nanogel, there are about 19 cross-linking points where a cross-linking point is formed by aggregation of trimer cholesterol molecules with the spatially inhomogeneous distribution of the mass fractal dimension of 2.6. The average radius of the partial chains can also be determined to be 1.7 nm. As the result, the complex structure of the nanogels is coherently revealed at the nanoscopical level.
Sekine, Yurina; Kobayashi, Riki*; Chi, S.*; Fernandez-Baca, J. A.*; Suzuya, Kentaro; Fujisaki, Fumika*; Ikeda, Kazutaka*; Otomo, Toshiya*; Fukazawa, Tomoko*; Yamauchi, Hiroki; et al.
JPS Conference Proceedings (Internet), 8, p.033009_1 - 033009_6, 2015/09
Neutron diffraction profiles of low-DO-content poly-N,N,-dimethylacrylamide (PDMAA) hydrogels were measured from 100 to 300 K to investigate the structure and properties of water in hydrogels. A broad diffraction observed at temperatures lower than 220 K indicates the existence of amorphous ice in the hydrogels at low temperatures. During the heating process, diffraction peaks from ice crystals appear in the profiles. These peaks indicate that cubic ice and hexagonal ice exist at T 220 K. We refined the structure parameters of these ices in the hydrogel, which indicate the existence of low-density ice in the hydrogel.
Sekine, Yurina; Takagi, Hajime*; Sudo, Sayoko*; Kajiwara, Yutaro*; Fukazawa, Hiroshi; Fukazawa, Tomoko*
Polymer, 55(24), p.6320 - 6324, 2014/11
To investigate the effects of structure of polymer side chains on structure of water in hydrogels, Raman spectra of polyacrylamide (PAA) and poly-,-dimethylacrylamide (PDMAA) hydrogels were measured. PAA and PDMAA have similar chemical structures, except for the side chain structure. The result shows that the frequency of the OH stretching mode for the PAA hydrogel decreases as the water content decreases, while that for the PDMAA hydrogel increases. We conclude that most of the bound water molecules in the PAA hydrogel form four strong hydrogen bonds with the hydrophilic groups in the side chain of PAA, whereas those in the PDMAA hydrogel form weak hydrogen bonds with surrounding water molecules. The water structure is an important factor governing the physical and chemical properties of gel materials.
Sekine, Yurina; Fukazawa, Tomoko*; Aizawa, Mamoru*; Kobayashi, Riki*; Chi, S.*; Fernandez-Baca, J. A.*; Yamauchi, Hiroki; Fukazawa, Hiroshi
Journal of Physical Chemistry B, 118(47), p.13453 - 13457, 2014/08
Neutron diffraction patterns for deuterated poly-,,-dimethylacrylamide (PDMAA) hydrogels were measured from 10 to 300 K to investigate the structure and properties of water in the gels. Diffraction peaks observed below 250 K indicate the existence of ice in the hydrogels. Some diffraction peaks from the ice are at lower diffraction angles than those in ordinary hexagonal ice (Ih). These shifts in peaks indicate that the lattice constants of the and axes in the ice are about 0.29% and 0.3% higher than those in ice Ih, respectively. The results show that bulk low-density ice can exist in PDMAA hydrogels. The distortions in the lattice structure of ice imply significant interactions between water molecules and the surrounding polymer chains, which play an important role in the chemical and mechanical properties of the hydrogel.
Arakawa, Masashi*; Kagi, Hiroyuki; Fernandez-Baca, J. A.*; Chakoumakos, B.*; Fukazawa, Hiroshi
Geophysical Research Letters, 38, p.L16101_1 - L16101_5, 2011/08
The existence of ferroelectric ice XI with ordered hydrogen in space becomes of interest in astronomy and physical chemistry because of the strong electrostatic force. However, the influence was believed to be limited because it forms at narrow temperature range. From neutron diffraction experiments, we found that small hydrogen-ordered domains exist at significantly higher temperature and the domains induce the growth of "bulk" ice XI. The small ordered domain is named "memory" of hydrogen ordered ice because it is the residual structure of ice XI. Since the memory exists up to at least 111 K, most of ices in the solar system are hydrogen ordered and may have ferroelectricity. The small hydrogen-ordered domains govern the cosmochemical properties of ice and evolution of icy grains in the universe.
Fukazawa, Hiroshi; Arakawa, Masashi*; Kagi, Hiroyuki; Yamauchi, Hiroki; Chakoumakos, B. C.*; Fernandez-Baca, J. A.*
Physics and Chemistry of Ice 2010, p.421 - 428, 2011/03
Whether or not ice in the universe exists as ferroelectric is a question that has attracted interest in astrophysics and physical chemistry, because long-range electrostatic forces, caused by the ferroelectricity, might be an important factor for materials evolution and hydrogen bonding. From neutron diffraction and scattering measurements, we have studied ice with impurities, such as potassium, sodium and lithium, that acted as a catalyst. Time-resolved diffraction experiments show that ferroelectric ice XI with hydrogen-ordered arrangement nucleates and grows with time for about 5 days. We found that the doped ice that has once been converted to ice XI is a stronger ferroelectric ice than that has never been converted. We also show the existence of the ferroelectric ice under high-pressure and its formation from compressed amorphous ice.
Arakawa, Masashi*; Kagi, Hiroyuki; Fernandez-Baca, J. A.*; Chakoumakos, B. C.*; Fukazawa, Hiroshi
Physics and Chemistry of Ice 2010, p.329 - 338, 2011/03
We measured neutron diffraction profiles of KOD, NaOD, LiOD, Ca(OD), and ND-doped ices. Ice XI, which is a hydrogen-ordered phase of normal ice (ice Ih), was observed in the KOD and NaOD-doped ices although Ca(OD) and ND-doped ice did not transformed to ice XI. The mass fraction of ice XI to that of the doped ice () was estimated using Rietveld analysis for each doped ice. The value of the doped ice, which had once experienced being ice XI, was larger than that of the doped ice, which had never experienced being ice XI. The large value of the doped ice indicates that small hydrogen-ordered domains remained above the transition temperature between ice XI and Ih. Our results suggest that large amounts of ice on icy bodies in our solar system can transform to ice XI. In this paper, we discussed the existence of the small hydrogen-ordered domains in space and the evolution of icy grain.
Igawa, Naoki; Taguchi, Tomitsugu; Fukazawa, Hiroshi; Yamauchi, Hiroki; Utsumi, Wataru
Journal of the American Ceramic Society, 93(8), p.2144 - 2146, 2010/08
The neutron powder diffraction measurement of LiCoNiMnO was carried out and the crystal structure and scattering density distribution were analyzed by Rietveld refinement and the maximum entropy method to estimate the Li diffusing pathway. Rietveld refinement showed that the structure was basically the same as LiCoO: a -3 space group, with Li and O mainly occupying the 3 and 6 sites, and Co, Ni and Mn randomly occupying the 3 site. Approximately 4% of the Li and Ni atoms exchanged their original sites (3 and 3) to occupy 3 and 3, respectively. Based on maximum entropy method analyses, we surmise that Li atoms moved on the (001), (003) and (00-3) planes and diffused through the 3-9-3 sites on those planes.
Nippon Kessho Gakkai-Shi, 52(4), p.219 - 225, 2010/08
The complex behavior of water and the unusual properties of ferroelectric ice XI continue to attract much interest. Whether ice in the space exists as ice XI, is an important question, because long range electrostatic forces caused by the ferroelectricity might be an important factor for planet formation. From neutron diffraction experiments, we found the temperature and pressure conditions for the transformation of the largest fraction of ice into ferroelectric ice. It suggests that myriad big icy-bodies, which exist as dwarf planets and Kuiper Belt Object, consist of thick ferroelectric-ice surface. Furthermore, we report spectral and vibrational properties of ferroelectric ice investigated by inelastic neutron scattering and infrared absorption measurements. Because the spectral properties of ferroelectric ice are clearly different from those of ordinary ice, the distinct ferroelectric ice in the universe is detectable using infrared telescopes and planetary exploration.
Igawa, Naoki; Taguchi, Tomitsugu; Hoshikawa, Akinori*; Fukazawa, Hiroshi; Yamauchi, Hiroki; Utsumi, Wataru; Ishii, Yoshinobu*
Journal of Physics and Chemistry of Solids, 71(6), p.899 - 905, 2010/06
Crystal structures of carbon dioxide deuterohydrate were studied by neutron powder diffraction at temperatures from 10 to 200 K. Maps of scattering length density distribution were obtained using a maximum entropy method, which clarified the motion of CO molecules in the hydrate. In small cages, the carbon atom of the CO molecule is at the center of the cage, and the oxygen atoms of CO revolve freely around the carbon atom. In large cages, the carbon atom also is at the center of the cage, but the oxygen atoms tend to revolve around the carbon atom along the plane parallel to the hexagonal facets of the cage.
Arakawa, Masashi*; Kagi, Hiroyuki; Fukazawa, Hiroshi
Journal of Molecular Structure, 972(1-3), p.111 - 114, 2010/05
We measured the neutron powder diffraction of 0.013 M KOD-doped DO ice to investigate the formation process of ice XI, a hydrogen-ordered phase of ice Ih. The doped ice Ih transformed to ice XI after annealing at 57 and subsequently at 68 K. The mass fraction of ice XI to that of the doped ice () was estimated using Rietveld analysis for each sample. The value of the doped ice, which had once experienced being ice XI ( = 0.23), was larger than that of the doped ice, which had never experienced being ice XI ( = 0.14). Results indicate that small hydrogen-ordered domains remained in the ice Ih, which had once trans- formed to ice XI, and accelerated the phase transition from ice Ih to ice XI. Results further suggest that large amounts of ice on icy bodies in our solar system can transform to ice XI, which might be detectable using infrared telescopes or planetary exploration in the near future.
Radioisotopes, 59(3), p.239 - 247, 2010/03
The complex behavior of water and the unusual properties of proton ordering in ferroelectric ice crystal continue to attract much interest. Whether ice in the space exists as proton-ordered ices, is an important question. Some ordered ices have ferroelectricity, and long range electrostatic forces caused by the ferroelectricity might be an important factor for planet formation. From neutron diffraction experiments, we found the temperature conditions for the transformation of the largest fraction of ice into ferroelectric ice using the lowest level of impurity dopant. It suggests that myriad big icy-bodies, which exist as dwarf planets and Kuiper Belt Object, consist of thick ferroelectric-ice surface.
Nagasaki, Takanori*; Shiotani, Shinya*; Igawa, Naoki; Yoshino, Masahito*; Iwasaki, Kota*; Fukazawa, Hiroshi; Utsumi, Wataru
Journal of Solid State Chemistry, 182(10), p.2632 - 2639, 2009/10
We propose a new method, a difference maximum entropy method (MEM) analysis of the neutron diffraction data, for revealing the detailed structure around hydrogen atoms in proton-conducting oxides. This MEM analysis uses the differences between the structure factors of protium- and deuterium-dissolved crystals. Simulations demonstrate that it not only provides the distribution of hydrogen atoms alone, but also improves the spatial resolution of MEM mapping around hydrogen atoms. Applied to actual diffraction data of protium- and deuterium-dissolved BaSnInO at 9 K, difference MEM analysis reveals that O-D bonds mostly tilt towards the second nearest oxygen atoms, and that the distributions of deuterium and oxygen atoms are probably insignificant in interstitial regions.
Arakawa, Masashi; Kagi, Hiroyuki; Fukazawa, Hiroshi
Astrophysical Journal; Supplement Series, 184(1), p.361 - 365, 2009/09
Infrared absorption spectra of ice were obtained at 4, 60, 100, 140, 160, and 240 K to make spectroscopic observations of hydrogen ordering at low temperatures. A broad peak observed at around 850 cm (11.7-181 m) was derived from libration of water molecules. The peak width was notably narrower at temperatures less than 140 K. A decrease in the peak width occurring in accordance with the formation of ice with ordered arrangements of hydrogen atoms was suggested from incoherent inelastic neutron-scattering studies. These results are consistent with ordering of hydrogen atoms. Existence of hydrogen-ordered ice in space is the subject of continuing astronomical debate. Our results demonstrate that the ordered ice in space is detectable using infrared telescopes and planetary exploration.
Shimoyama, Tomotaka*; Tojo, Takeo*; Kawaji, Hitoshi*; Atake, Toru*; Fukazawa, Hiroshi; Igawa, Naoki
Solid State Ionics, 180(6-8), p.560 - 562, 2009/05
The neutron diffraction of BaZrScO with and without proton were measured and analyzed by Rietveld method and Maximum Entropy Method. We found that the location of proton is 12 site near oxygen ion. The heat capacity of sample with proton is larger than that without proton. This difference is discussed in term of the changes of the crystal structure and lattice vibrations due to the dissolution of proton.
Machida, Akihiko; Otomo, Toshiya*; Hattori, Takanori; Fukazawa, Hiroshi
Koatsuryoku No Kagaku To Gijutsu, 19(1), p.24 - 30, 2009/02
We have investigated the fundamental properties of metal hydrides or hydrogen storage materials. The interest is focused on basic understanding of the hydrogen-metal interactions in metal hydride systems. Neutron scattering technique, which is capable of determining hydrogen positions and bonding states, is a key tool to investigate the interactions, and becomes significantly powerful when combined with high pressure technique, which realizes high hydrogen density states by compression of metal lattices. In this article, we present high-pressure neutron scattering techniques using Paris-Edinburgh cell and hydrogen-gas cell under development at J-PARC and JRR-3.
Nippon Kessho Gakkai-Shi, 51(1), p.84 - 85, 2009/02
Our neutron diffraction study suggests that icy interior inside cool planets is ferroelectric. The super-dense ferroelectric ice, possessing the ability to carry a charge, could have had important effects on geological events on cool planets.
Fukazawa, Hiroshi; Hoshikawa, Akinori*; Chakoumakos, B. C.*; Fernandez-Baca, J. A.*
Nuclear Instruments and Methods in Physics Research A, 600(1), p.279 - 281, 2009/02
We measured time-resolved neutron powder diffraction of ices doped with very small amounts of some catalysts using the wide-angle neutron diffractometer (WAND) at the High Flax Isotope Reactor (HFIR) in Oak Ridge, Tennessee. We succeeded in making ferroelectric ice, which prepared at high pressures (0.2 and 0.4 GPa), in a 60 to 75 K temperature range over tens hours. Neutron diffraction experiments confirmed the existence of a large ferroelectric structure in the sample. Therefore, thick surface (about 500 Km) of ferroelectric ice may exist on cold icy bodies, such as, Pluto and Kuiper Belt Objects (KBO). It suggests that about 70% of Pluto body is ferroelectric ice. Future telescope or planetary probe will be able to detect the huge ferroelectric-ice mass. In this symposium we report recent results at the HFIR and our future plan using higher intensity neutron beam.
Yamauchi, Hiroki; Ishii, Yoshinobu*; Igawa, Naoki; Fukazawa, Hiroshi; Utsumi, Wataru
JAEA-Research 2008-077, 28 Pages, 2008/10
The neutron powder diffractometer, HRPD, can provide high-resolution data that meet the many users' needs until now. On the other hand, the demand of high-efficiency is growing in the recent years. In order to improve the source intensity and measurement efficiency, the authors tried to develop asymmetric reflection-type Ge monochromators. The mosaic crystals (20 in the horizontal direction) were cut at an angle of 40 relative to the Ge,3,3,1 reflecting planes. The diffraction results of standard Si samples reveal that peak intensities by the asymmetric type are improved 1.2 times larger than those by the existing symmetric type, but integrated intensities are almost comparable each other. For mosaic crystals, asymmetric reflections in compression geometry intensify the current density, but reflectivity is always less than that in symmetric reflections, and thus the suppression of the reflectivity just cancels out the enhancement of the current density.