Rev. High Pressure Sci. Technol.

Vol.10  No.4 (2000) Abstract

Rev. High Pressure Sci. Technol. 10-4,275-282(2000)
Computer Simulation of Supercritical Water and Aqueous Solutions
吉井範行* 三浦伸一** 岡崎 進**
Noriyuki YOSHII Shinichi MIURA Susumu OKAZAKI
In the recent decade, many computational studies as well as physicochemical experiments such as neutron diffraction and NMR spectroscopic measurements have actively been done in order to clarify the structure and dynamics of supercritical water and its solutions. In particular, studies on hydrogen bonding in supercritical water have been attracting much interest from physical chemists. Long-ranged structure and the relevant collective motion have also been investigated in detail. For supercritical solutions, thermodynamic properties such as solubility and the microscopic structure of ion hydration have been studied. Here, recent progress in computational studies on the structure and dynamics of the fluids is reviewed.

[supercritical water, aqueous solution, computer simulation, structure, dynamics, cluster]
*〒240-0196 横須賀市長坂2-6-1 (財)電力中央研究所横須賀研究所プラント熱工学部
Thermal Engineering Department, Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka 240-0196
**〒226-8502 横浜市緑区長津田町4259 東京工業大学総合理工学研究科物質電子化学専攻
Department of Electronic Chemistry, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502

Rev. High Pressure Sci. Technol. 10-4,283-289(2000)
Dynamics Structural Analysis of Supercritical Water
松林伸幸 中尾奈穂子 中原勝
The rotational dynamics of water in super- and subcritical conditions is investigated by measuring the spin-lattice relaxation time T1 of heavy water (D2O). The experimentally determined T1 is shown to be governed by the quadrupolar mechanism even in the supercritical conditions and to provide the second-order reorientational correlation time t2R of the O-D axis. It is then found that while t2R decreases rapidly with the temperature on the saturation curve, it remains on the order of several tens of femtoseconds when the density is varied at a temperature above the critical. The comparison of t2R with the angular momentum correlation time shows that the inertial effect is operative in the rotational dynamics of supercritical water. The dependence of t2R on the hydrogen bonding state is also examined in combination with computer simulations, and the effect of the hydrogen bonding on the rotational dynamics in supercritical water is found to be weaker than but to be on the same order of magnitude as that in ambient water on the relative scale. Actually, although t2R is divergent in the limit of zero density, it is observed to increase with the density when the density is above ~1/3 of the critical.

[supercritical water, rotational dynamics, reorientational relaxation time, NMR spin-lattice relaxation time, inertial effect, hydrogen bonding]
〒611-0011 京都府宇治市五ヶ庄 京都大学化学研究所 界面物性研究部門
Division of Solution and Interface Chemistry, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011

Rev. High Pressure Sci. Technol. 10-4,290-296(2000)
Dynamic Behavior of Anion and Solute/Solvent in Fluids at High Pressures and Temperatures
生島 豊   相沢 崇史
Yutaka IKUSHIMA   Takafumi AIZAWA
In this article, we have dealt not only with the dynamic behavior of nitrate anion in aqueous zinc nitrate solution at high temperatures and a fixed pressure but also with photoreduction of benzophenone by N,N,-diethylaniline in supercritical carbon dioxide with time-resolved absorption techniques. In the former cases the perpendicular orientational relaxation time (t) of the anion significantly decreases with increasing temperature up to 340℃; the values of twere 1.86 and 0.25 ps at 20 and 340℃, respectively. In the latter the rate constant at 40℃ decreased greatly with increasing pressure from 9.8 to 17.2 MPa, which is considered to be due to the local aggregation of carbon dioxide around benzophenone and/or N,N,-diethylaniline.

[supercritical fluids, rotational relaxation, nitrate anion, Raman analysis, photoreduction, benzophenone, time-resolved absorption]
〒983-8551 仙台市宮城野区苦竹4-2-1 工業技術院東北工業技術研究所
National Industrial Research Institute of Tohoku, 4-2-1 Nigatake, Miyagino-ku, Sendai 983-8551

Rev. High Pressure Sci. Technol. 10-4,297-304(2000)
Temperature and Pressure Effects on the Spin-Lattice Relaxation Times of Solvent Molecules
in Electrolyte Solutions
上野 正勝 吉田 亨次*
Masakatsu UENO Koji YOSHIDA
To elucidate the effect of ions on the solvent structures in view of the dynamics of solvent molecules, the spin-lattice relaxation times (T1) of solvent molecules (D2O and DMSO) in various electrolyte solutions were measured in a relatively wide range of temperature under atmospheric pressure, and those of D2O at moderate temperature under high pressure. From the behaviors of rotational correlation times (tc) and their activation energies (Ea) of solvent molecules (D2O) hydrated to the ions, the ions are classified into structure-making and structure-breaking ions. These characteristics obtained in aqueous solutions were compared with those in non-aqueous solutions (DMSO). Finally the pressure effects on tc in D2O solutions are discussed focusing on the pressure dependence of the hydrophobic hydration.

[NMR, spin-lattice relaxation time, NMR B-coefficient, two-state model, rotational correlation time, electrolyte solution, heavy water, dimethyl sulfoxide]
〒610-0321京田辺市多々羅都谷1-3 同志社大学工学部機能分子工学科
Department of Molecular Science and Technology, Faculty of Enfineering, Doshisha University, Kyotanabe, Kyoto 610-0321
* 〒814-0180 福岡市城南区七隈8-19-1 福岡大学理学部化学科
Department of Chemistry, Faculty of Science, Fukuoka University, Jonan-ku, Fukuoka 814-0180

Rev. High Pressure Sci. Technol. 10-4,305-311(2000)
Pressure Effect on the Solvation and Rotational Dynamics in Solution
原 公彦 伊藤 直樹
Kimihiko HARA Naoki ITO
The purpose of this article is to discuss the effect of pressure on the solvation dynamics and the rotational reorientation dynamics in solution, which have been studied by measuring the picosecond time-dependent fluorescence Stokes shift (TDFSS) and picosecond time-dependent fluorescence rotational depolarization (TDFRD) at high pressures. At the time scale longer than the present time resolution of ca. 20 ps, whose dynamics correspond to the molecular motion in n-alcohol solvent viscosity greater than 0.2 mPa s, the solvation and rotational reorientation dynamics are well characterized by the simple continuum prediction. In a restricted state as in a micellar environment, a nondiffusive pressure effect is observed.

[time-dependent fluorescence Stokes shift, time-dependent fluorescence anisotropy, solvation time, rotational reorientation time, viscosity, continuum model]
〒606-8502 京都市左京区北白川追分町 京都大学大学院理学研究科
Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502

Rev. High Pressure Sci. Technol. 10-4,312-318(2000)
Analyses of ultrahigh pressure materials by an analytical electron microscope
藤野清志a    宮島延吉b   富岡尚敬c
Kiyoshi FUJINO  Nobuyoshi MIYAJIMA  Naotaka TOMIOKA
Analyses of ultrahigh pressure materials by an analytical electron microscope (AEM) are reviewed. AEM provides important advantages for analyzing synthetic and natural ultrahigh pressure materials because it enables us to analyze both structure and composition of these materials down to tens of nm-sized grains. Using AEM, several new high-pressure minerals were discovered in shocked meteorites, and new phases and new phase transformation behaviors were recognized in ultrahigh pressure experiments under the Earth's lower mantle conditions.

[analytical electron microscope, ultrahigh pressure materials, shocked meteorites, Earth's lower mantle]
a〒060-0810 札幌市北区北10条西8丁目 北海道大学大学院理学研究科地球惑星科学専攻
Division of Earth and Planetary Sciences, School of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo 060-0810
b(現住所)Bayerisches Geoinstitut, Universitat Bayreuth, D-95440 Bayreuth, Germany
c(現住所)Department of Geology, Arizona State University, Tempe, Arizona 85287-1404, USA

Rev. High Pressure Sci. Technol. 10-4,319-325(2000)
Fabrication of Structural Materials by the Combination of Self-Propagating High-Temperature Synthesis (SHS) and High-Pressure Technology
廣田 健*  中根 慎護†  芳仲 捷*   山口 修*
Self-propagating high-temperature synthesis (SHS) is currently developed for the production of intermetallic compounds and ceramic powders. SHS has some features, i.e., a very short synthetic time, low energy consumption, high productivity, and furthermore synthesizing novel materials which cannot be prepared by solid state reaction and powder metallurgy. This paper reviews recent research trends and progress related to the structural materials fabricated by the combination of SHS and high-pressure technology. Especially, the characteristics of dense sintered composite materials by spark plasma sintering (SPS) are described, focusing on their microstructures and mechanical properties.

[self-propagating high-temperature synthesis (SHS), high-pressure technology]
*〒610-0321 京都府京田辺市多々羅 同志社大学工学部機能分子工学科
Dept. of Molecular Science and Technology, Faculty of Engineering, Doshisha Unibersity, Tatara, Kyo-tanabe, Kyoto, 610-0321
†〒520-8639 滋賀県大津市晴嵐2-7-1 日本電気硝子(株)技術部第三グループ
Technical Division, Nippon Electric Glass Co., Ltd, Seiran 2-7-1, Otsu, Shiga, 520-8639

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