Rev. High Pressure Sci. Technol. 9-2,109-116(1999)
Glassy States and Two Types of Polyamorphism
|Glass transformations, glass transition temperatures, various glassy states under elevated pressures, and polyamorphism are reviewed. There are two types of polyamorphism in the glassy states: the first is that produced from the history of glass-forming conditions, and the second is that produced from changes in the structure of liquids. A critical point of structural polyamorphism is deduced from the recent experiments on the first-order like glass-glass transition of tetrahedral glasses. The critical point locates on the equilibrium liquid surface in the P-V-T space under an elevated pressure below the glass transition temperature, but above the Kauzmann temperature. The low-temperature limit of the liquid under the critical pressure is the critical point; and the liquid, except the critical pressure, vitrifies gradually without any transition. The equations of the glassy states are briefly discussed.
[Glass, glass transition, glassy state, polyamorphism, pressure history, low-density glass, high-density glass, phase transition, critical point, Kauzmann temperature, equation of states]
|〒376-8515 群馬県桐生市天神町1-5-1 群馬大学工学部生物化学工学科
Bioscience Department, Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515
Rev. High Pressure Sci. Technol. 9-2,117-125(1999)
─ 高圧下の実験を中心に ─
Glass Transitions of Molecular Materials Studied by Calorimetry
─ Focused on High Pressure Experiments ─
|Our recent calorimetric studies on the glass transition, especially for the high pressure experiments, are reviewed in this article. The materials examined are molecular liquids with relatively simple molecular structure. The content of the article is as follows.
(2) Adiabatic Calorimeter under High Pressure
(3) Configurational Entropy and Short-Range Ordering
(4) Configurational Entropy and a Relaxation Time
(5) Pressure Dependence of Glass Transition and Adam-Gibbs Theory.
(6) Prigogine-Defay Ratio and Internal Parameter Theory
(7) Structural Relaxation in (Volume)-(Internal Energy)-(Gibbs Energy) Space
(8) Concluding Remarks
[glass transition, molecular liquid, calorimetry, dilatometry, heat capacity, configurational entropy, high pressure, Adam-Gibbs theory, internal parameter theory]
|〒560-0043 大阪府豊中市待兼山町1-1 大阪大学大学院理学研究科化学専攻
Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043
Rev. High Pressure Sci. Technol. 9-2,126-133(1999）
Neutron Scattering Study of Dynamics in Glassy State;Recent Topics
|筑紫 格 金谷 利治
Itaru TSUKUSHI Toshiji KANAYA
|We review some recent developments in glassy dynamics research using neutron scattering. We focus on the following three topics: (i) low-energy excitation, (ii) fast βprocess, (iii) dynamic heterogeneity in glassy state. In the first and second topics, we show that recent research on glassy materials with various degrees of disorder provide useful information about the microscopic origin of low-energy excitation and fast βprocess. In the third topic, a non-Gaussian parameter is introduced to evaluate dynamic heterogeneity of glassy materials through mean square displacement, and a correlation between the non-Gaussian parameter and fragility index is pointed out . Distribution functions of the mean square displacement are evaluated on the basis of Gaussian, log-Gaussian and bimodal distributions.
[incoherent inelastic neutron scattering, low-energy excitation, fast β process, non-Gaussian parameter, log-normal distribution, bimodal distribution, fragility]
|〒611-0011 京都府宇治市五ヶ庄 京都大学化学研究所
Institute for Chemical Research, Kyoto University, Uji, Kyoto-fu, 611-0011
Rev. High Pressure Sci. Technol. 9-2,134-141(1999)
Kinetic Heterogeneities in Highly Supercooled Liquids
|山本 量一 小貫 明
Ryoichi YAMAMOTO Akira ONUKI
|Highly supercooled liquids with soft-core potentials are studied via molecular dynamics simulations in two and three dimensions in quiescent and sheared conditions. We may define bonds between neighboring particle pairs unambiguously owing to the sharpness of the first peak of the pair correlation functions. Upon structural rearrangements, they break collectively in the form of clusters whose sizes grow with lowering the temperature T. The bond life time tb, which depends on T and the shear rate g, is on the order of the usual structural or a relaxation time ta in weak shear gta≪ 1, while it decreases as1/g in strong shear gta ≫ 1 due to shear-induced cage breakage. Accumulated broken bonds in a time interval (〜 0.05tb) closely resemble the critical fluctuations of Ising spin systems. For example, their structure factor is well fitted to the Ornstein-Zernike form, which yields the correlation length x representing the maximum size of the clusters composed of broken bonds. We also find a dynamic scaling relation, tb 〜 x z, valid for any T and g with z=4 in two dimensions and z=2 in three dimensions. The viscosity is of order tb for any T and g, so marked shear-thinning behavior emerges. The shear stress is close to a limiting stress in a wide shear region. We also examine the motion of tagged particles in shear in three dimensions. The diffusion constant is found to be of order tb-n with n=0.75 〜 0.8 for any T and g, so it is much enhanced in strong shear compared with its value at zero shear. This indicates breakdown of the Stokes-Einstein relation in accord with experiments. The origin of the breakdown is discussed in detail.
[glass transition, supercooled liquids, molecular dynamics simulation, kinetic heterogeneity, rheology, diffusion, Stokes-Einstein relation]
|〒606-8502 京都市左京区北白川追分町 京都大学理学部物理学第一教室
Department of Physics, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502
Rev. High Pressure Sci. Technol. 9-2,142-145(1999)
|Erythrocyte Aggregation Enhanced by Hydrostatic Pressure|
|Yoshiharu TOYAMA, Shinji OHKAWA,
Toshiaki DOBASHI and Akio SAKANISHI
|The effects of pressure on the aggregation of swine erythrocytes were investigated by monitoring the erythrocyte sedimentation rate under high pressure, up to 40 MPa. The aggregation of erythrocytes in plasma was proportionally enhanced by pressure, whereas aggregation of erythrocytes was not observed in saline solution up to 40 MPa. These results suggest that the adhesion energy between erythrocytes is not directly affected by pressure, but through a change in the interaction energy between plasma components and erythrocytes.
[erythrocyte, plasma, aggregation, sedimentation rate, high pressure]
|Department of Biological and Chemical Engineering, Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan|
Rev. High Pressure Sci. Technol. 9-2,146-153(1999)
A Guide for High Pressure Experiments
−Laboratory-made Piston-Cylinder Apparatus−
|Procedures for in-laboratory construction of an autofrettaged cylinder is described, including design, choice of the materials, machining as well as heat treatment of the cylinder. Details of high pressure-high temperature experiments up to 1 GPa and 400℃ are given with special emphasis on encapsulation and sealing techniques.
[piston-cylinder, design, material selection, machining]
|〒606-8502 京都市左京区北白川追分町 京都大学理学部化学科
Division of Chemistry，Graduated School of Science，Kyoto University，Sakyo-ku，Kyoto 606-8502
Rev. High Pressure Sci. Technol. 9-2,154-159(1999)
Research and Development at RIST
|The Research Institute for Solvothermal Technology (RIST), opened in September 1997 to carry out research related to high-temperature and high-pressure fluid technology. RIST has recently developed new technologies using supercritical fluids, especially carbon dioxide and water, in areas related to the environment, such as the treatment of organic waste, the production of new materials, such as new-carbon substances, materials for batteries and electromagnetic wave absorption; and in the area of energy and resources, such as the conversion or the recycling of industrial plastic waste. This paper also describes the general concept of solvothermal technology, critical phenomena, the philosophy on high pressure research development and the problems of joint research projects with the cooperation of enterprises, universities and government.
［solvothermal technology, high pressure, high temperature, supercritical fluid, carbon dioxide, water］
|〒761-0301 香川県高松市林町2217-43 高温高圧流体技術研究所
Research Institute for Solvothermal Technology
京都市左京区下鴨森本町 15 (財)生産開発科学研究所内
Tel (075)721-0376 Fax (075)723-9629