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Journal Articles

Downward terrestrial gamma-ray flash observed in a winter thunderstorm

Wada, Yuki*; Enoto, Teruaki*; Nakazawa, Kazuhiro*; Furuta, Yoshihiro; Yuasa, Takayuki*; Nakamura, Yoshitaka*; Morimoto, Takeshi*; Matsumoto, Takahiro*; Makishima, Kazuo*; Tsuchiya, Harufumi

Physical Review Letters, 123(6), p.061103_1 - 061103_6, 2019/08

AA2018-0706.pdf:0.79MB

 Times Cited Count:22 Percentile:87.28(Physics, Multidisciplinary)

Journal Articles

Gamma-ray glow preceding downward terrestrial gamma-ray flash

Wada, Yuki*; Enoto, Teruaki*; Nakamura, Yoshitaka*; Furuta, Yoshihiro; Yuasa, Takayuki*; Nakazawa, Kazuhiro*; Morimoto, Takeshi*; Sato, Mitsuteru*; Matsumoto, Takahiro*; Yonetoku, Daisuke*; et al.

Communications Physics (Internet), 2(1), p.67_1 - 67_9, 2019/06

 Times Cited Count:27 Percentile:91.38(Physics, Multidisciplinary)

Journal Articles

Termination of electron acceleration in thundercloud by intracloud/intercloud discharge

Wada, Yuki*; Bowers, G. S.*; Enoto, Teruaki*; Kamogawa, Masashi*; Nakamura, Yoshitaka*; Morimoto, Takeshi*; Smith, D.*; Furuta, Yoshihiro*; Nakazawa, Kazuhiro*; Yuasa, Takayuki*; et al.

Geophysical Research Letters, 45(11), p.5700 - 5707, 2018/06

 Times Cited Count:19 Percentile:78.9(Geosciences, Multidisciplinary)

Journal Articles

Hierarchically self-organized dissipative structures of filler particles in poly(styrene-$$ran$$-butadiene) rubbers

Yamaguchi, Daisuke; Yuasa, Takeshi*; Sone, Takuo*; Tominaga, Tetsuo*; Noda, Yohei*; Koizumi, Satoshi*; Hashimoto, Takeji*

Macromolecules, 50(19), p.7739 - 7759, 2017/10

 Times Cited Count:8 Percentile:37.66(Polymer Science)

We elucidated the spatial distribution of filler particles in cross-linked poly(styrene-$$ran$$-butadiene) rubbers (SBR) developed under a typical fillers/rubbers compounding process as one of dissipative structures formed under a stress field imposed on the given system. The dispersion state of the fillers in SBR was clarified on the basis of hierarchical structures consisting of five structure levels. More specifically, it has the following characteristics depending on the specific interactions: Small, compact clusters build up compact mass-fractal structures, while large, loose clusters build up open mass-fractal structures.

Oral presentation

Analysis of dispersion of fillers in functionalized SSBR/filler composites by using neutron and X-ray scattering

Yamaguchi, Daisuke; Koizumi, Satoshi; Yuasa, Takeshi*; Sone, Takuo*; Tominaga, Tetsuo*

no journal, , 

A comprehensive small-angle scattering analyses on the dispersion state of fillers in rubber/filler compounds was investigated. Recently, an effective size reduction of dispersible units of the fillers and consequential improvement of the property of the hysteresis loss was attained in the end functionalized S-SBR/filler system. To get more insight into the hierarchical structure of those systems, a complementary use of different contrasts between neutron and synchrotron X-ray was attempted in this study. Each different profile of neutron and X-ray scattering suggested two dominant structures within the system: one is the higher-order aggregations of the filler particles and the other is originated from vulcanized SBR matrices.

Oral presentation

Analysis of dispersion state of fillers in functionalized S-SBR/filler composites

Yamaguchi, Daisuke; Koizumi, Satoshi; Yuasa, Takeshi*; Sone, Takuo*; Tominaga, Tetsuo*

no journal, , 

A comprehensive ultrasmall- and small-angle scattering analysis on the dispersion state of fillers in rubber/filler compounds is investigated. Recently, an effective size reduction of dispersible units of the fillers and consequential improvement of the property of the hysteresis loss was attained in the end functionalized S-SBR/filler system. Here S-SBR denotes solution polymerization styrene-butadiene rubber. To get more insight into the hierarchical structure of those systems, a complementary use of different contrasts between neutron and synchrotron X-ray was attempted. The different q-dependence of the scattering profiles taken by neutron and by X-ray suggested that two dominant structures exist in the system: one is the higher-order aggregations of the fillers and the other is the density fluctuations due to the vulcanization. By modification of the chain end of SBR with a functional group having the affinity for the fillers, the scattering signals originated from the vulcanization of SBR hardly changed, whereas those originated from the aggregation of the fillers distinctly changed. This tendency strongly supports the above scenario for the improvement of mechanical property of rubber/filler compounds.

Oral presentation

Hierarchical structure in multi-component rubber/filler system

Yamaguchi, Daisuke; Koizumi, Satoshi; Yuasa, Takeshi*; Sone, Takuo*; Tominaga, Tetsuo*

no journal, , 

Small-angle scattering analyses of rubber/filler compounds is investigated. An effective size reduction of dispersible units of the fillers and consequential improvement of the mechanical property was attained in the end functionalized S-SBR/filler system. To get more insight into the hierarchical structure of those systems, a complementary use of neutron and synchrotron X-ray was attempted. The obtained scattering profiles suggested that two dominant structures exist in the system: one is the higher-order aggregations of the fillers and the other is the density fluctuations due to the vulcanization. By modification of the SBR, the scattering signals originated from the vulcanization of SBR hardly changed, whereas those originated from the aggregation of the fillers changed. This tendency strongly supports the above scenario for the improvement of mechanical property of rubber/filler compounds.

Oral presentation

Study of silica particle dispersion in styrene-btadiene rubber by spin contrast variation technique

Noda, Yohei; Yamaguchi, Daisuke; Hashimoto, Takeji; Koizumi, Satoshi; Tominaga, Tetsuo*; Sone, Takuo*; Yuasa, Takeshi*

no journal, , 

For investigating the dispersion state of silica particles in styrene-butadiene rubber composites, we measured its small angle neutron scattering with polarizing its proton spins. By proton spin polarization, we can control the coherent scattering length for neutron beam. As a result, we succeeded in abstracting the scattering profile only from the silica particles.

Oral presentation

Spin contrast variation study of silica-filled styrene-butadiene rubber

Noda, Yohei; Yamaguchi, Daisuke; Hashimoto, Takeji; Koizumi, Satoshi; Tominaga, Tetsuo*; Sone, Takuo*; Yuasa, Takeshi*

no journal, , 

For silica-filled styrene-butdiene rubber samples, we measured small angle neutron scattering with the proton spins in the samples being aligned to one direction. As a result, we precisely determined the silica particles' dispersion by the abstracted partial scattering function.

Oral presentation

Spin contrast variation technique for a multi-component system; A Study of silica-filled styrene-butadiene rubber

Noda, Yohei; Yamaguchi, Daisuke; Hashimoto, Takeji; Koizumi, Satoshi; Yuasa, Takeshi*; Tominaga, Tetsuo*; Sone, Takuo*

no journal, , 

For silica-filled styrene-butadiene rubber, we measured small angle neutron scattering with the proton spins in the sample being aligned to one direction. We succeeded in determination of the silica particles' dispersion by analyzing the abstracted partial scattering function of the silica particles.

Oral presentation

Spin contrast variation study of fuel-efficient tire rubber

Noda, Yohei; Yamaguchi, Daisuke; Hashimoto, Takeji; Shamoto, Shinichi; Koizumi, Satoshi; Yuasa, Takeshi*; Tominaga, Tetsuo*; Sone, Takuo*

no journal, , 

We have developed a spin contrast variation technique. Our target is hydrogeneous solid materials such as polymer and rubber, which are not easy to be deuterated and can absorb a vapor of a stable free radical, TEMPO, which serves as an electron spin source necessary for high proton spin polarization (P) through dynamic nuclear polarization. By use of this vapor permeation technique, we succeeded in polarizing silica-filled SBR rubber, which is a material for fuel-efficient tire. From the polarized SANS profiles obtained with various P values, we succeeded in separating the partial scattering function of silica, which is considered to be a key factor for the fuel-efficiency.

Oral presentation

Small angle neutron scattering study with contrast variation by dynamic nuclear polarization; Application to silica-filled styrene-butadiene rubber

Noda, Yohei; Yamaguchi, Daisuke; Hashimoto, Takeji; Shamoto, Shinichi; Koizumi, Satoshi; Tominaga, Tetsuo*; Sone, Takuo*; Yuasa, Takeshi*

no journal, , 

We will report the result of the small angle neutron scattering study of silica-filled SBR rubber with contrast variation by dynamic nuclear polarization. As a result of this study, we succeeded in precise evaluation of silica particles' dispersion state in composite rubber materials, which has been known to have strong effect on the fuel-efficiency or tire rubber.

Oral presentation

A Complemental use of SANS and SAXS for the analysis of multi-component hierarchical structure

Yamaguchi, Daisuke; Noda, Yohei; Koizumi, Satoshi; Hasegawa, Yoshio*; Hishinuma, Yukio*; Suzuki, Masashi*; Kodama, Hiroto*; Onuma, Masato*; Oba, Yojiro*; Yuasa, Takeshi*; et al.

no journal, , 

Nowadays industrial materials tend to include a variety of additives and to be a composite of them to satisfy a high request for intelligent function and durability. Elucidation of such a multi-component and hierarchical structure is really a tough work but indispensable to learn the fundamentals of relation between the structure and property and to attain a reasonable improvement of those materials. Combined use of small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) often gives a good clue to decompose the total scattering of the organic/inorganic composite into the partial scattering from a particular component. Two examples will be demonstrated here for extracting the structural information from the composite specimen via this method; one is the distribution of the dopant nitrogen atoms in the porous photocatalyst and the other is the dispersion state of fillers in the rubber matrix.

Oral presentation

Proton spin contrast variation approaches; From basic polymer to fuel-efficient tire rubber

Noda, Yohei; Yamaguchi, Daisuke; Hashimoto, Takeji; Shamoto, Shinichi; Koizumi, Satoshi; Yuasa, Takeshi*; Tominaga, Tetsuo*; Sone, Takuo*

no journal, , 

We have developed a proton spin contrast variation technique. It has been known that a good DNP performance is achieved in a polyethylene sample absorbed a vapor of TEMPO radical as an electron spin source. We recently applied this technique to silica-filled SBR rubber, which is used for tread rubber of fuel-efficient tires. Finally, we successfully evaluated silica particles' dispersion state precisely, which is supposed to have great effect on tire's fuel efficiency.

Oral presentation

Structural analysis of fuel-efficient tire rubber in nanometer scale by spin contrast variation technique

Noda, Yohei; Yamaguchi, Daisuke; Hashimoto, Takeji; Shamoto, Shinichi; Koizumi, Satoshi; Yuasa, Takeshi*; Tominaga, Tetsuo*; Sone, Takuo*

no journal, , 

We applied proton spin contrast variation technique to silica filled SBR rubber, which is widely used for a fuel-efficient tire. In this technique, vapor sorption of TEMPO radical as an electron spin source played an important role for achieving high degree of proton spin polarization. As a result, we successfully evaluated the dispersion state of silica particles, which is known to be a key factor for tire's fuel efficiency.

Oral presentation

Contrast variation in small angle neutron scattering by polarizing proton spins; Structural analysis of silica-filled SBR rubber

Noda, Yohei; Yamaguchi, Daisuke; Hashimoto, Takeji; Shamoto, Shinichi; Koizumi, Satoshi*; Yuasa, Takeshi*; Tominaga, Tetsuo*; Sone, Takuo*

no journal, , 

The outline of contrast variation method by dynamic nuclear polarization, which we have developed, will be explained. As a recent achievement, we applied this technique to silica-filled SBR rubber, which is widely used for fuel-efficient tire, and succeeded in revealing its detail structure which have not been obtained. Additionally, we will mention merits which will be obtained by introducing new techniques in solid state NMR field.

Oral presentation

Small-angle neutron scattering as a useful tool for green innovation materials

Yamaguchi, Daisuke; Noda, Yohei; Koizumi, Satoshi*; Yuasa, Takeshi*; Sone, Takuo*; Tominaga, Tetsuo*; Takenaka, Mikihito*; Amino, Naoya*

no journal, , 

Using a combined ultra-small-angle and small-angle scattering methods with both of neutron and X-ray probes, we characterized hierarchical structures of silica and/or carbon black filler particles dispersed in solution polymerized poly(styrene-random-butadiene) rubber (SBR). Two types of SBR were employed for the preparation of filler/rubber compounds; one possesses a newly developed functionalized chain-end (f-SBR), which has an affinity for filler particles and the other is a conventional SBR (n-SBR) without any special interaction with fillers. Combined small-angle scattering measurements clarified that the average-size of aggregated fillers dispersed in f-SBR matrix is smaller than that dispersed in n-SBR matrix.

Oral presentation

A Discussion for the dispersion/aggregation of silica or carbon black particles

Yamaguchi, Daisuke; Yuasa, Takeshi*; Sone, Takuo*; Tominaga, Tetsuo*

no journal, , 

Using a combined ultra-small-angle and small-angle scattering (CSAS) method, we characterized hierarchical structures of silica and/or carbon black filler particles dispersed in solution polymerized poly(styrene-random-butadiene) rubber (SBR). Two types of SBR were employed for the preparation of filler/rubber compounds; one possesses a newly developed functionalized chain-end (f-SBR), which has an affinity for filler particles and the other is a conventional SBR (n-SBR) without any special interaction with fillers. CSAS measurements clarified that the average-size of aggregated fillers dispersed in f-SBR matrix is smaller than that dispersed in n-SBR matrix. In addition, those aggregated fillers either in f-SBR or in n-SBR exhibited their own mass-fractal dimensions in their higher-order structures.

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