Language：English  

DOI： 10.1063/1.5054577

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

We have examined the conditions under which the breakdown of the Stokes-Einstein (SE) relation occurs in pure Lennard-Jones (LJ) fluids over a wide range of temperatures and packing fractions beyond the critical point. To this end, the temperature and packing-fraction dependence of the self-diffusion coefficient, D, and the shear viscosity,eta(sv), were evaluated for Xe using molecular dynamics calculations with the Green-Kubo formula. The results showed good agreement with the experimental values. The breakdown was determined in light of the SE equation which we have recently derived for pure LJ liquids: D eta(sv) = (k(B)T/2 pi)(N/V)(1/3), where k(B) is the Boltzmann constant, T is the temperature, and N is the particle number included in the system volume V. We have found that the breakdown occurs in the lower range of the packing fraction, eta < 0.2, and derived the SE relation in its broken form as D eta(sv) = 0.007(1 - eta)(-5) eta(-4/3)(k(B)T/epsilon)(n)k(B)T (N/V)(1/3), where n increases from 0 up to 1 with the decreasing eta. The equation clearly shows that the breakdown mainly occurs because the packing-fraction dependence does not cancel out between D and eta(sv) in this region, which is attributed to the gaseous behavior in the packing-fraction dependence of the shear viscosity under a constant number density. In addition, the gaseous behavior in the temperature dependence of the shear viscosity also partially causes the breakdown.

DOI： 10.1103/PhysRevE.95.052122

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

The present study evaluates the thermal design of a blanket system using Flinabe in order to facilitate further discussions on its applicability as a self-cooled liquid blanket system. Molecular dynamics simulations were performed to evaluate the Prandtl number of mixtures in five compositions (LiF-NaF-BeF2 = 31-31-38, 36-27-37, 42-22-36, 49-16-35, and 67-0-33). Thermofluid analysis was carried out to estimate the temperature margin and pressure drop per unit length in a simple geometry model of the blanket system. The Prandtl number of Flinabe is above 100 at 400 degrees C. The present study reveals that Flinabe remarkably relaxes the design conditions compared to Flibe as a coolant owing to its low melting point. In contrast, the pressure drop per unit length of Flinabe is higher than that of Flibe because the viscosity exponentially increases at low temperature. The temperature margin is quite dependent on the heat load on the first wall. If the pressure drop per unit length is around 1.0 MPa/m, the heat load value must be approximately below 0.7 MW/m(2).

DOI： 10.1080/15361055.2017.1330623

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The Benford law states that the frequencies of decimal digits at the first place of numbers corresponding to various kinds of statistical or experimental data are not equal changing from 0.3 for 1 to 0.04 for 9. The corresponding frequencies' distribution is described by the logarithmic function. As is shown in the present article, the Benford distribution is a particular case of a more general mathematical statement. Namely, if a function describing the dependence between two measurable quantities has a positive second derivative, then the mentioned above frequencies decrease for digits from 1 to 9. The exact Benford distribution is valid for the exponential function only. Explicit expressions for frequencies of leading digits are obtained and specified for the power, logarithmic, and tangent functions as examples. The kinematic experiment was performed to illustrate the above results. Also the tabulated data on thermal conductivities of liquids confirm the proposed formula for frequencies' distribution. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physa.2016.06.054

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Na+ ions play important roles on the physical and chemical properties of aluminosilicate glasses. It is known that they strongly modify the network of tetahedral SiO4 and AlO4 units, but the microscopic details on how they alter the local structure remain to be fully established. Here we address this issue by performing classical molecular dynamics simulations over a wide range of glasses compositions. The simulations include atomic polarization and deformation effects through the use of a DFT-parametrized aspherical ion model (AIM), which is carefully validated against experimental data (bond lengths, neutron and X-ray diffraction, and NMR spectroscopy). We show that the structure of the glasses is a subtle interplay between the nature of bridging/nonbridging oxides and the arrangement of Na+ ions around them. This reflects, in particular, on the oxide instantaneous dipole moments.

DOI： 10.1021/acs.jpcc.6b08052

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

In order to mimic the Brownian particle in liquid, molecular dynamics calculations of dilute solutions of spherical fullerene molecules with various sizes in liquid Ar were performed. To establish the scaling equation for self-diffusion coefficient, D, of the fullerenes, the dependence of D was examined on the mass ratio of solute to solvent and on the energy-parameter ratio used in the Lennard-Jones potentials. The dependence on the energy-parameter ratio remains up to C-540, whereas D rapidly becomes independent of the mass ratio with increasing mass of the solute. The product of the scaling equations obtained for the D of the solute and for shear viscosity,eta(sv), for the solvent gives a relation which replaces the Stokes-Einstein relation based on the hydrodynamics. The present expression does not need both the boundary conditions and the hydrodynamic particle size, but instead the energy-parameter ratio, packing fraction of solvent, and bare size of solute. From the viewpoint of the tackiness at the boundary, the cage correlation function around the diffusing particle was examined; it was found that the decay time of the function depends mainly on the the energy-parameter ratio. Therefore, the energy-parameter ratio accounts for the main part of both the boundary conditions and the hydrodynamic particle size in the Stokes equation, which have so far been ill-defined in any molecular theories.

DOI： 10.1103/PhysRevE.93.050104

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

A simple and direct evaluation method for concentration fluctuation (CF), using molecular dynamics simulation, is presented and applied to Lennard Jones liquid mixtures and an aqueous solution of 1-propanol. The method is intuitive and straightforward, and the results are consistent with those based on the Kirkwood Buff integrals. It enables us to quantitatively and visually observe the time evolution of the mesoscopic CF.

DOI： 10.1246/cl.150952

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Explicit expressions of the self-diffusion coefficient, D-i, and shear viscosity, eta(sv), are presented for Lennard-Jones (LJ) binary mixtures in the liquid states along the saturated vapor line. The variables necessary for the expressions were derived from dimensional analysis of the properties: atomic mass, number density, packing fraction, temperature, and the size and energy parameters used in the LJ potential. The unknown dependence of the properties on each variable was determined by molecular dynamics (MD) calculations for an equimolar mixture of Ar and Kr at the temperature of 140 K and density of 1676 kg m(-3). The scaling equations obtained by multiplying all the single-variable dependences can well express D-i and eta(sv) evaluated by the MD simulation for a whole range of compositions and temperatures without any significant coupling between the variables. The equation for D-i can also explain the dual atomic-mass dependence, i.e., the average-mass and the individual-mass dependence; the latter accounts for the "isotope effect" on D-i. The Stokes-Einstein (SE) relation obtained from these equations is fully consistent with the SE relation for pure LJ liquids and that for infinitely dilute solutions. The main differences from the original SE relation are the presence of dependence on the individual mass and on the individual energy parameter. In addition, the packing-fraction dependence turned out to bridge another gap between the present and original SE relations as well as unifying the SE relation between pure liquids and infinitely dilute solutions. (C) 2015 AIP Publishing LLC.

DOI： 10.1063/1.4934627

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

TiO2 and SiO2 are materials with unique importance in materials science. They are often modelled using conventional force fields, but including polarization effects is compulsory for enhancing the accuracy of the simulations. Here we parameterize a force field for the two materials in the framework of the polarizable ion model. The parameterization is performed via a generalized force-fitting methodology using DFT calculations as reference data. We show that it is possible to generate a force field in which the same parameters are used for the oxide ion in both SiO2 and TiO2, and which is able to reproduce accurately the equilibrium structure of their various crystalline polymorphs, as well as glassy silica.

DOI： 10.1088/0965-0393/23/7/074005

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER NUCLEAR SOC  

This study evaluates the physical properties of the molten salt Flinabe, using molecular dynamics simulations to discuss its applicability to a fusion blanket system. More specifically, the simulations calculate the density and viscosity of Flinabe to facilitate further discussion of the applicability from the viewpoint of the heat removal of the first wall. The results of the simulations are compared with data reported in earlier publications, which support the validity of the simulations. This study reveals that Flinabe tends to have lower viscosity than Flibe even when they contain almost the same BeF2. Analyzing the results of the simulations confirms that the degree of polymerization in Flinabe correlates with its viscosity, as that in Flibe does. The analyses also revealed, however, that the correlation in the case of Flibe is not directly applicable to the case of Flinabe.

DOI： 10.13182/FST14-975

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

A polarisable ion model is parameterised for the whole series of molten alkali halides by using first-principles calculations based on density functional theory. Viscosity, electrical conductivity and thermal conductivity are determined using molecular dynamics simulations via the Green-Kubo formulae and confronted to experimental results. The calculated transport coefficients are generally in much better agreement than those obtained with the empirical Fumi-Tosi potentials. The inclusion of polarisation effects significantly decreases the viscosity and thermal conductivity, while it increases the electrical conductivity. The individual dynamics of the ions is analysed using the Stokes-Einstein relation. The anion behaviour is always well represented using the slip boundary condition, while for cations there is an apparent shift from slip to stick condition when the ionic radius decreases. This difference is interpreted by subtle changes in their coordinating environment, which are maximised in the case of Li+ cation.

DOI： 10.1080/00268976.2015.1046527

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

An explicit expression of the Stokes-Einstein (SE) relation in molecular scale has been determined for pure Lennard-Jones (LJ) liquids on the saturated vapor line using a molecular dynamics calculation with the Green-Kubo formula, as D eta(sv) = kT xi(-1)(N/V)(1/3), where D is the self-diffusion coefficient, eta(sv) the shear viscosity, k the Boltzmann constant, T the temperature,. the constant, and N the particle number included in the system volume V. To this end, the dependence of D and eta(sv) on packing fraction, eta, and T has been determined so as to complete their scaling equations. The equations for D and eta(sv) in these states are m(-1/2) (N/V)(-1/3) (1 - eta)(4) epsilon T-1/2 and m(1/2) (N/V)(2/3) (1 - eta)(-4) epsilon T-1/2(0), respectively, where m and epsilon are the atomic mass and characteristic parameter of energy used in the LJ potentials, respectively. The equations can well describe the behaviors of D and eta(sv) for both the LJ and the real rare-gas liquids. The obtained SE relation justifies the theoretical equation proposed by Eyring and Ree, although the value of xi is slightly different from that given by them. The difference of the obtained expression from the original SE relation, D eta(sv) = (kT/2p)sigma(-1), where sigma means the particle size, is the presence of the eta(1/3) term, since (N/V)(1/3) = (6/pi)(1/3) sigma(-1)eta(1/3). Since the original SE relation is based on the fluid mechanics for continuum media, allowing the presence of voids in liquids is the origin of the eta(1/3) term. Therefore, also from this viewpoint, the present expression is more justifiable in molecular scale than the original SE relation. As a result, the eta(1/3) term cancels out the s dependence from the original SE relation. The present result clearly shows that it is not necessary to attribute the deviation from the original SE relation to any temperature dependence of particle size or to introduce the fractional SE relation for pure LJ liquids. It turned out that the. dependence of both D and eta(sv) is similar to that in the corresponding equations by the Enskog theory for hard sphere (HS) fluids, although the T dependence is very different, which means that the difference in the behaviors of D and eta(sv) between the LJ and HS fluids are traceable simply to their temperature dependence. Although the SE relation for the HS fluids also follows D eta(sv) = kT xi(-1)(N/V)(1/3), the value of xi is significantly different from that for the LJ liquids.

DOI： 10.1103/PhysRevE.91.012111

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Language：English   Publishing type：Part of collection (book)   Publisher：Wiley Blackwell  

Octahedral ionic species are known to exist in molten rare earth chlorides as well as molten alkali metal chlorides containing UO22+ ions. This phenomenon can be utilized in the pyrochemical reprocessing of nuclear spent fuels (MOX co-deposition) in which candidate molten salt solvent systems to stabilize UO22+ and/or PuO22+ ions were proposed for a molten CsCl-NaCl system. Lanthanum trichloride reported in MS8 was replaced by yttrium trichloride since both compounds are known to have different crystal structures but form the same types of octahedral complex anions and their clusters on melting. In the present work, not only the ionic species existing in the molten CsCl-NaCl-YCl3 system but also the short-range structure of the molten CsCl-NaCl solvent system was studied in some detail by pulsed neutron diffraction. No complexation occurred in any solvent melt, but the formation of octahedral complex ions such as YCl63- and the clustering of these were detected by the addition of YCl3.

DOI： 10.1002/9781118448847.ch6f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The thermal conductivities of molten alkali fluorides (LiF, NaF, and KF) and their mixtures (LiF NaF, LiF KF, and NaF-KF binaries and LiF NaF KF ternary) are predicted using molecular dynamics simulation with the Green-Kubo method. A polarizable ion model is used to describe the interionic interactions. All the systems except LiF KF and LiF NaF-KF mixtures follow a scaling law: it is proportionnal to m(A)(-1/2)(N/V)(2/3), where m(A) is the arithmetic average of the ionic species masses in a given melt and N is the total number of ions included in the system volume V. In LiF KF and LiF-NaF-KF mixtures a significant departure from the scaling law is observed. By examining separately the effects of the cation mass and size asymmetry in LiF KF mixtures, we show that both of them account for half of the deviation. Finally, we observe that the temperature dependence of the thermal conductivity is very small in these molten fluorides.

DOI： 10.1021/jp411781n

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The origin of both weak temperature dependence and packing fraction dependence of T-1/4 eta(3/2) in the thermal conductivity of the simple Lennard-Jones (LJ) liquid is explored. In order to discuss the relative contributions from attractive or repulsive part of the interaction potential separately, the thermal conductivity of a series of Weeks-Chandler-Anderson (WCA) fluids is calculated by molecular dynamics simulations. The results show that the repulsive part plays the main role in the heat conduction, while the attractive part has no direct effect on the thermal conductivity for a given packing fraction. By investigating WCA fluids with potentials of varying softness, we explain the difference observed between the LJ liquids such as argon and Coulombic liquids such as NaCl. (C) 2014 AIP Publishing LLC.

DOI： 10.1063/1.4868438

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

Dynamic structure factor of charge density was evaluated by MD simulation for molten LiI with artificially varied ionic masses. The dispersion curve was obtained from the peak frequency of collective excitation. The peak frequency at zero wavevector and the modulus of group velocity were estimated from the dispersion curves, as a function of ionic mass. The peak frequency at zero wavevector shows that the optic mode can be thermally excited for all the molten alkali halides. This suggests the ideas that the charge-density modes may dominate the thermal transport in these systems, and that insensitivity of the thermal conductivity of molten alkali halides to details of interionic potentials can be attributed to the behavior. The obtained modulus of group velocity was roughly proportional to m(G)(-1/2), where m(G) is the geometric average of anion and cation masses. This suggests that it may partially replace the mass term in the expression of thermal conductivity. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.82.152

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Language：English   Publishing type：Research paper (scientific journal)  

The thermal conductivity of rare gases in liquid and dense fluid states has been evaluated using molecular dynamics simulation with the Lennard-Jones (LJ) potentials and the Green-Kubo (GK) formula. All the calculated thermal conductivities are in very good agreement with experimental results for a wide range of temperature and density. Special attention was paid to temperature and packing-fraction dependence which is nontrivial from dimensional analysis on the LJ potentials and the GK formula. First, the temperature dependence of T1/4 was determined from the calculations at constant densities. Secondly, in order to obtain the dependence on packing fraction from that on number density separately, a scaling method of particle and/or cell size was introduced. The number density dependence of (N/V)2/3 which is expected from the dimensional analysis of the GK formulas was confirmed and the packing-fraction dependence of η3/2 was determined by using the scaling method. It turned out that the summarized functional form of m-1/2(N/V)2/3η3/2T1/4 can well express both the calculated and experimental thermal conductivities for Ar, Kr, and Xe, where m is the atomic mass. The scaling method has also been applied to molten NaCl and KCl so that it has been found that the thermal conductivity has the packing-fraction dependence of η2/3 which is much weaker than that of the simple LJ liquids. © 2014 American Physical Society.

DOI： 10.1103/PhysRevE.89.022129

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER/PLENUM PUBLISHERS  

A definition suitable for the average ionic mass used for two kinds of expressions of the thermal conductivity for molten alkali halides has been explored from the viewpoint of the difference in anion and cation masses. One is the scaling equation, lambda proportional to m(-1/2) (N/V)(2/3), where m is the average ionic mass between the anion and cation and N/V is the number density, which was previously obtained from molecular dynamics (MD) simulation. The other is the equation used in the corresponding-states (CS) analysis which has been applied to the thermal conductivities calculated by the MD simulation. Among some representative definitions, it turned out that a simple arithmetic average is best for the equation. As an estimation method of the thermal conductivity, it was shown that both equations have comparable precision. It was indicated that considering the difference in ionic masses between the anion and cation is important for building a more precise correlation in the CS analysis.

DOI： 10.1007/s10765-014-1593-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The thermal conductivity of rare gases in liquid and dense fluid states has been evaluated using molecular dynamics simulation with the Lennard-Jones (LJ) potentials and the Green-Kubo (GK) formula. All the calculated thermal conductivities are in very good agreement with experimental results for a wide range of temperature and density. Special attention was paid to temperature and packing-fraction dependence which is nontrivial from dimensional analysis on the LJ potentials and the GK formula. First, the temperature dependence of T-1/4 was determined from the calculations at constant densities. Secondly, in order to obtain the dependence on packing fraction from that on number density separately, a scaling method of particle and/or cell size was introduced. The number density dependence of (N/V)(2/3) which is expected from the dimensional analysis of the GK formulas was confirmed and the packing-fraction dependence of eta(3/2) was determined by using the scaling method. It turned out that the summarized functional form of m(-1/2)(N/V) (2/3)eta T-3/2(1/4) can well express both the calculated and experimental thermal conductivities for Ar, Kr, and Xe, where m is the atomic mass. The scaling method has also been applied to molten NaCl and KCl so that it has been found that the thermal conductivity has the packing-fraction dependence of eta(2/3) which is much weaker than that of the simple LJ liquids.

DOI： 10.1103/PhysRevE.89.022129

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Language：English   Publishing type：Part of collection (book)   Publisher：Elsevier Inc.  

In recent years, molecular modeling has become an indispensable tool for studying the structure and dynamics of molten salts. In this chapter, we first provide a short description of the state-of-the-art models and methods used for modeling molten salts at the atomic scale. In particular, we discuss the importance of polarization effects for obtaining accurate results. We then give some examples of the structure of several molten salts, as yielded by the simulations. We finish by describing how the transport properties, which encompass the diffusion coefficients, electrical conductivities, viscosities, and thermal conductivities, are computed. By comparing the values given by the simulations to reference experimental data, we show that this technique can now be considered as highly predictive. © 2013 Elsevier Inc. All rights reserved.

DOI： 10.1016/B978-0-12-398538-5.00001-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

The thermal conductivities of molten (Na-K)Cl systems have been evaluated using equilibrium molecular dynamics simulation within the framework of Fumi-Tosi potential models. An expression for the thermal conductivity of binary ionic mixtures was derived from the phenomenological equations between flux densities and their conjugate forces in the related transport processes. Each transport coefficient was evaluated using the Green-Kubo formula. The statistical errors of thermal conductivity evaluated using six kinds of the coefficients in these mixtures were estimated to be ca. 7-12%, depending on composition, which is comparable with the case for single molten NaCl evaluated using three kinds of the coefficients. The calculation results for the equimolar mixture show that the thermal conductivity depends strongly on density, but only weakly on temperature. Furthermore, all the calculated thermal conductivities of the mixtures scale with m (-1/2) (N/V)(2/3), where m is the average ionic mass and N/V is the number density. These results regarding temperature and density dependencies and scaling with m (-1/2) (N/V)(2/3) are common to the previous results for a series of single molten alkali halides.

DOI： 10.1080/08927022.2011.564171

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Thermal conductivities of ionic compounds (NaCl, MgO, Mg(2)SiO(4)) are calculated from equilibrium molecular dynamics simulations using the Green-Kubo method. Transferable interaction potentials including many-body polarization effects are employed. Various physical conditions (solid and liquid states, high temperatures, high pressures) relevant to the study of the heat transport in the Earth's mantle are investigated, for which experimental measures are very challenging. By introducing a frequency-dependent thermal conductivity, we show that important coupled thermoelectric effects occur in the energy conduction mechanism in the case of liquid systems.

DOI： 10.1088/0953-8984/23/10/102101

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

Basic research in actinide chemistry and physics is indispensable to maintain sustainable development of innovative nuclear technology. Actinides, especially minor actinides of americium and curium, need to be handled in special facilities with containment and radiation shields. To promote and facilitate actinide research, close cooperation with the facilities and sharing of technical and scientific information must be very important and effective. A three-year-program "Basic actinide chemistry and physics research in close cooperation with hot laboratories", ACTILAB, was started to form the basis of sustainable development of innovative nuclear technology. In this program, research on actinide solid-state physics, solution chemistry and solid-liquid interface chemistry is made using four main facilities in Japan in close cooperation with each other, where basic experiments with transuranium elements can be made. The O-17-NMR measurements were performed on (Pu0.91Am0.09)O-2 to study the electronic state and the chemical behaviour of Am and Cm ions in electrolyte solutions was studied by distribution experiments.

DOI： 10.1088/1757-899X/9/1/012018

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Ultrasonic wave velocities in small trabeculae of bovine femur were investigated using a micro-Brillouin scattering technique. Our micro-Brillouin scattering system enables the measurement of wave velocities in the GHz range over a minute area (diameter: approximately 10 mu m). Using thin trabecular specimens with a thickness of about 150 mu m, the distribution of longitudinal wave velocity in a trabecula was observed. In the direction parallel to the trabecular alignment, the velocity changed depending on the measurement position. We measured 20 different trabeculae in our specimens, and the average wave velocities in each trabecula were similar at approximately 4.92 x 10(3) m/s. In addition, the difference in average velocity was not statistically significant between trabeculae that align in the bone axis or anterior-posterior directions. These data tell us the possibility that the average wave properties are similar in all trabeculae. (c) 2010 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.49.07HB05

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Ultrasonic wave velocities in a small trabecula of bovine femur were investigated using micro-Brillouin scattering technique. Our micro-Brillouin scattering system enables the measurement of wave velocities in the GHz range over a minute area (diameter: approximately 10 μm). Using thin trabecular samples with thickness of about 150 μm, the distribution of longitudinal wave velocity in a trabecula was observed. In the direction parallel to the trabecula, the velocity changed due to the measured point. The average velocities of each trabecula were similar and approximately 4.92×10 3 m/s, despite the difference of trabecular shape (aspect ratio). In addition, the difference was not statistically significant between trabeculae which align in bone axis or anterior-posterior directions. The effects of trabecular direction and aspect ratio on the velocity were not statistically significant. These data tell us the possibility that the average elastic properties are similar in all trabeculae. ©2009 IEEE.

DOI： 10.1109/ULTSYM.2009.5441395

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

Local structure of molten lanthanum trichloride - alkali chloride ternary systems was analyzed in terms of Raman spectroscopy and pulsed neutron diffraction in order to accelerate the realization of pyrochemical reprocessing of nuclear spent fuels. In particular, not only vibrational modes of ionic species existing in molten LaCl3-ACl-NaCl (A = Li, K, Rb, and Cs) systems but also short. range structure in molten LaCl3-CsCl-NaCl system on behalf of the systems described before were reported in some detail, the salt combinations of which could be of prototype in the reprocessing of UO2 and/or PuO2.

DOI： 10.5796/electrochemistry.77.736

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Expressions for the energy current of a system of charged, polarizable ions in periodic boundary conditions are developed in order to allow the thermal conductivity in such a system to be calculated by computer simulation using the Green-Kubo method. Dipole polarizable potentials for LiCl, NaCl, and KCl are obtained on a first-principles basis by "force matching" to the results of ab initio calculations on suitable condensed-phase ionic configurations. Simulation results for the thermal conductivity, and also other transport coefficients, for the melts are compared with experimental data and with results obtained with other interaction potentials. The agreement with experiment is almost quantitative, especially for NaCl and KCl, indicating that these methodologies, perhaps with more sophisticated forms for the potential, can be used to predict thermal conductivities for melts for which experimental determination is very difficult. It is demonstrated that the polarization effects have an important effect on the energy current and are crucial to a predictive scheme for the thermal conductivity.

DOI： 10.1063/1.3086856

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The thermal conductivities of a series of molten alkali halides have been evaluated by using molecular dynamics simulation within the framework of Fumi-Tosi potential models. Although the calculated results showed 0%-50% larger values than experimental results depending on system, they are in agreement with each other in showing both negative temperature and ionic mass dependence. In order to clarify the cause of the negative temperature dependence in more detail, the thermal conductivity under constant temperature or constant density was evaluated for all alkali chlorides and all sodium halides. The calculations reveal that the thermal conductivity depends strongly on density but only weakly on temperature. While the integrated value of the autocorrelation function for energy current increases with temperature, this is canceled out by the reciprocal temperature factor in relation to the thermal conductivity. With increasing density the integrated value increases, and this dominates the behavior of the thermal conductivity. By repeating the calculations with different ionic masses, we have concluded that the thermal conductivity is a function of m(-1/2)(N/V)(2/3), where m is the geometric mean of ionic mass between anion and cation and N/V is the number density.

DOI： 10.1063/1.3064588

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

To evaluate microscopic bone elasticity without contribution from macroscopic structures, a micro-Brillouin scattering technique was used. Our micro-Brillouin scattering system enables the measurement of wave velocities in the GHz range over a minute area (diameter: approximately 10 mu m). We have applied this technique to thinly sliced bovine trabecular bone and collagen film. The average wave velocity in one trabecula was approximately 4.8 x 10(3) m/s which was much higher than the velocity in the collagen film. The velocity anisotropy near the trabecular nodes was weak but complicated. In addition, these velocities were also higher than velocities in the cortical bone, which were in the MHz range. These investigations show the possibility of using the Brillouin scattering technique to evaluate microscopic bone elasticity, which is closely related to the quality of bone matrix. [DOI: 10.1143/JJAP.47.4205]

DOI： 10.1143/JJAP.47.4205

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Language：English   Publisher：INSTITUTE OF PURE AND APPLIED PHYSICS  

As the first step in realizing the simple and nondestructive measurement of shear waves in the GHz range, a technique involving Brillouin scattering and a ZnO shear wave transducer is proposed. Making use of transmitted shear waves, we have succeeded in observing a strong Stokes Brillouin peak in the quartz sample. This technique can be applied to the measurement of anisotropic layers and small samples. © 2007 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.46.4626

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Brillouin scattering is an efficient nondestructive and noncontact measurement method to obtain the wave properties of thin layers at hypersonic frequencies. The reflection induced Theta A (RI Theta A) scattering geometry enables the simultaneous measurement of the phonons, which propagate in each direction of wave vectors of q(Theta A) ( propagation in the film plane) and q(180) ( back scattering). Using this scattering geometry, we could observe the refractive indices and birefringence of the piezoelectric poly-vinylidene fluoride (PVDF)film as a function of temperature. By introducing the microscopic technique, the elastic anisotropy and refractive index measurements in the minute area of polycrystalline ZnO films were also performed. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ultras.2006.05.162

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Barium borate xBaO-(1-x)B2O3 and lithium borate xLi(2)O-(1-x)B2O3 glasses were investigated by x-ray absorption spectroscopy at the boron K-edge and barium L-III-edge. This is the first XAS work at the K edge of boron in lithium borate and barium borate glasses. A resonant peak at the B K-edge was observed at around 194.6 eV, its intensity and area decrease with increasing the amount of four-coordinated B changed by increasing the modifier oxide content and reach their minima at 45 mol% BaO and 40 mol% Li2O. Ba N-II,N-III-edges were also observed. With increasing BaO content in barium borate glasses, the local structure around Ba changes from a single shell structure of six-coordinated O atoms at a Ba-O interatomic distance of 2-77 angstrom to a two-shell structure with distances 2.67 and 2.90 angstrom and coordination numbers four and 3-4, respectively.

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The short rangestructure of 0(.) 05Al(2)O(3),xNa,O.(0(.)95-x)B2O3 glasses (0(.)10 < x < 0(.)45) has been investigated using molecular dynamics calculations employing a fully ionic model. Regardless of x, the coordination number of oxygen atoms around the Al atom was approximately four. It was found that these Al atoms are present as network formers of AlO4 units in the glasses in the same manner as are BO4 units, and that they cause a decrease of the coordination number of 0 around Na. It is suggested that the exclusively formed AlO4 units may suppress the conversion of the BO3 unit to the BO4 unit caused by an increase of Na2O. The decrease of the fraction of four coordinated boron atoms, N-4, due to the addition of Al2O3 is supported by the results obtained from preliminary neutron diffraction measurements.

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Barium aluminoborate glasses with 10-60 mol% BaO content and 1-40 mol% Al2O3 content have been investigated by x-ray absorption spectroscopy (XAS) at the Ba L-III-edge, B K-edge and Al K-edge. With increasing BaO content, the Ba-O distance, RBa-O, and the coordination number, N-Ba change from a single coordination shell of 6 oxygen atoms at 2.74 angstrom to a double shell of 3.5 oxygen atoms at 2.68 angstrom and 3.0 oxygen atoms at 2.91 angstrom. The local structure of B and Al atoms changes in the Al2O3 high content region of these glasses. With increase of Al2O3 content, both local structures around B and Al atoms change from BO4 to BO3 units and from AlO4 to AlO6 units, respectively.

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From the radial distribution analysis of X-ray diffraction, the nearest neighbor La-Cl distance and coordination number of Cl around La in molten LaCl3 were estimated to be about 0.28 nm and nearly equal to 6, respectively. On the other hand, according to the XAFS measurements, the coordination number of Cl around La was evaluated at about 7. As a result, the local structure of molten LaCl3 was thought to be described as an octahedral-like coordination scheme where La was surrounded by about six or seven Cl's. This finding led to the formation of octahedral complex ion, LaCl63-, which was in agreement with results of Raman spectroscopy by other authors. The La-La distance was evaluated at about 0.5 nm from the position of a weak and broad second peak in the correlation function g(r), suggesting that a distorted corner-sharing connection of two octahedral complex species was predominant in the melt. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2005.04.037

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The structures of molten LaCl3 and molten CsCl-NaCl mixtures were studied by Raman spectroscopy. Ionic association in these melts was discussed according to the information of vibrational modes. Complex species of the octahedral type, LaCl63-, was formed in the melt and no association was observed in the molten CsCl-NaCl system.

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The local structures of molten LaCl3 and solid LaOCl at elevated temperatures were deduced from radial distribution analyses through La-L-III absorption-edge XAFS technique. The nearest neighbor La-Cl distance and the coordination number of Cl around La in molten LaCl3 have so far been reported to be about 0.28 nm. and nearly equal to 6 from the X-ray diffraction analysis. But the coordination number of Cl around La was evaluated at about 7 according to XAFS technique. By comparing the above results, the local structure of molten LaCl3 was considered whether it would be described as an octahedral-like coordination scheme where La was surrounded by about six to seven Cl's or the distinct schemes. A similar discussion was made on LaOCl with less solubility against molten salts.

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Raman spectra have been obtained for peroxide ion in Na2\O2 up to 950 K Drastic changes were observed in the spectra around 780 K, which could be attributed to the phase transition between the beta and alpha forms. The spectra of peroxide ions in molten NaOH were also obtained at 610 K, just above the eutectic temperature, and the peak could be observed up to 900 K for the melt containing 20 mol% Na2O2. This evidently shows that peroxide ions are able to be present in molten NaOH. An analysis of the peak position suggested the analogous local structure around peroxide ions in the melt with that in the crystal.

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We performed trial MD simulations for molten (Na-2Cs)Cl containing 10 wt% Of UO22+ at 1100 K. In order to incorporate different function forms between alkali halides and UO2, the Tosi-Fumi potentials used for the former were converted to the function form of the latter. From the viewpoints of both the bulk structure and local structure around UO22+, dependence of these structures was examined on the charge distribution in UO22+ using pair distribu tion functions, the coordination number, and snapshots. It was found that the bulk structure of the solvent was not influenced by the charge distribution in UO22+, although the local structure of UO22+ depended strongly on that in UO22+. Homogeneous dispersion of the UO22+ ions was observed in the case of the charge distribution in UO22+ with (Zu, Zo) = (4, -1), and the coordination number of Cl- around the U atoms was four.

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Raman spectra have been obtained for alpha- and beta-NaFeO2, Na3FeO3, Na8Fe2O7, Na5FeO4, and Na4FeO3 from room temperature up to 833 K in the powder state under an inert atmosphere. The comparison of the spectra showed good applicability of Raman spectroscopy to the identification of these sodium iron double oxides. We have therefore investigated the corrosion reaction of a steel surface with Na2O2 powder using in situ Raman spectroscopy. The obtained spectra showed that a corrosion reaction occurs under 833 K and the corrosion product was identified as Na5FeO4. A reaction mechanism for the corrosion based on the above results is proposed as follows: the system of Fe + Na2O2 produces corrosive melt under 833 K; it spreads over the surface of iron; the melts with a Na-rich composition produce Na5FeO4 in the initial state; the corrosion products distribute homogeneously on the surface. The corrosion reaction in a homogeneous powder mixture of Fe and Na2O2 has also been investigated using Raman spectroscopy with the help of XRD and DTA methods. The corrosion products were identified as double oxides whose compositions correspond to the stoichiometric molar ratio of Na to Fe in the starting materials, while the products from the surface reaction of steel with Na2O2 tended to have a specified composition of Na5FeO4. The difference was reasonably explained using the mechanism presented above. It was found from the DTA measurements that Na2O2, in contrast to Na2O and NaOH, has particularly strong corrosivity for iron.

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According to the radial distribution analysis of PbCl2 melt through pulsed neutron diffraction (PND), the Cl-coordination numbers around Pb were found to be about 4, corresponding to the peak at r = 2.84 angstrom in the correlation function G(r), and to be about 2 at r = 3.40 angstrom, respectively. These two peaks were thought to form the first coordination shell. On the contrary, the Br-coordination number around Pb was estimated at about 4. Although PbCl2 and PbBr2 have the same crystal structure, the short-range structure of the melts was quite different from each other. (c) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jpcs.2004.06.056

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Although the melt structure of glass-forming ZnCl2 has so far been well studied, there exists quite little information on the structural change due to anion-substitution. In the present work, the short-range structure of ZnCl2-ZnBr2 mixture melts was analyzed systematically by time-of-flight pulsed neutron diffraction techniques, Raman spectroscopy, molecular orbital calculations, and molecular dynamics simulations. According to radial distribution analysis, it was found that there were tetrahedral structural units of ligand-substituted [ZnClnBr4-n](2-) (n=0-4) in these melts, not implying the simple mixing of [ZnCl4](2-) and [ZnBr4](2-) units. Further detailed estimation indicated that the ligand-substituted complex anions were linked with each other by sharing a common anion. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.stam.2004.03.008

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Molecular dynamics (MD) simulations and X-ray scattering experiments have been carried out on liquid 1-propanol. The radial distribution functions obtained from these two methods were in good agreement with each other. On the basis of the hydrogen-bond number and the angular correlation functions of the four sequentially hydrogen-bonded O atoms derived from the MD calculation, it was found that the hydrogen-bonded O atoms preferentially form a planar zigzag chain structure, but that the plane undulates like a wave.

DOI： 10.1023/B:JOSL.0000043642.62263.69

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Reflection-induced ThetaA Brillouin scattering (RIThetaA) is introduced to investigate the opto-acoustic anisotropy of uniaxially stretched polyvinylidene fluoride (PVDF) films (0.04 mm in thickness). Although the films are not perfectly transparent, their elastic and optical anisotropy could be investigated nondestructively. The optical anisotropy, which is observed as birefringence, showed a clear decrease near the Curie temperature (T-c).

DOI： 10.1143/JJAP.43.2916

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A new optical geometry for Brillouin scattering measurement of thin films is proposed. Making use of the two incident laser beams focused on the sample, simultaneous measurements of 90A scattering and back scattering were performed. The strong scattering peaks in the spectra enabled simultaneous measurements of hypersonic wave velocity and refractive index. Actually, the appearance of anisotropy in the polypropylene (PP) film was continuously observed as an increase of birefringence during the ultra-drawing process.

DOI： 10.1143/JJAP.42.5865

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A Brillouin scattering technique has been applied to investigate the ultra-drawing process of polypropylene films. The gradual elastic changes during the drawing process showed the appearance of anisotropy and birefringence of the sample. Devising the optical geometry of Brillouin scattering measurement, continuous changes of the birefringence during ultra-drawing were. clearly observed. These data were compared with the data obtained using a polarizing microscope, which were acquired at specific points of the drawing process.

DOI： 10.1143/JJAP.42.3080

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Pulsed neutron diffraction experiments were performed on SrO.xB(2)O(3) (x=2, 3 and 4) and Na2O.xB(2)O(3) (x=7/3, 4 and 9) glasses. With the help of molecular dynamics (MD) simulation using simple isotropic pair potentials, the cation dependence of the short range structure is discussed in order to investigate the role of metal oxides. Previous results for calcium and barium borate glasses have also been modified using improved analytical methods. For alkaline earth oxides, the fraction of B atoms coordinated by four nearest neighbour 0 atoms shows that the number of four coordinated B atoms in the alkaline earth borate glasses increases with increasing cation size, whereas that in alkali borate glasses decreases with increasing cation size. On the other hand, there are only small differences between sodium and alkaline earth borate glasses in the cation dependence of the other parameters such as the peak position and asymmetry of the BO correlation. Results from neutron diffraction experiments are in good agreement with those from MD calculations.

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The surface wave velocity of the SiC layer on the Si substrate was investigated by the Brillouin scattering method. The quasi Rayleigh wave on the SiC layer was clearly observed, showing velocity dependence on the crystalline structure.

DOI： 10.1143/JJAP.41.3374

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Language：English   Publisher：Acoustical Society of Japan  

The effects of tensile stress on the hypersonic wave velocities in polymer films were analyzed using Brillouin scattering method. The longitudinal wave velocities in the directions of the stress or perpendicular to the stress during the tensile test were measured. The initial velocity profile of the polymer films during the tensile test was found to be similar with the stress behavior.

DOI： 10.1250/ast.22.375

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The structure of vitreous MO . nB(2)O(3) (M = Ca and Ba; n = 2, 3 and 4) has been studied by pulsed neutron diffraction measurement with the help of molecular dynamics (MD) simulation. The first and second peaks assigned to the nearest-neighbor B-O and O-O correlations, respectively, in the obtained total pair distribution functions shifted little with increasing MO content, while the asymmetry of the first peak increased significantly with MO content, these results are different from those for potassium borate glasses. It was inferred that the BO3 and BO4 units are better defined in these alkaline-earth borate glasses than those in the potassium borate glasses. Both the full-width at half maximum (FWHM) of the first peak and the average co-ordination number of O around B clearly increased as MO content increased which is the same behavior with alkali borate glasses. The fraction of four-co-ordinated B showed a larger deviation from x/(1 - x) for CaO-B2O3 glasses than that for BaO-B2O3 glasses which shows a different dependence of the deviation on cation size from that in alkali borate glasses, and is in good agreement with the results from MID simulation. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(01)00662-7

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We have performed molecular dynamics (MD) simulations for vitreous P2O5 using isotropic pair potentials composed only of coulombic and repulsive interactions. The P-O pair distribution function obtained had the two distinguishable peaks expected from the results of neutron diffraction experiments, in the nearest-neighbor P-O correlation. The neutron-weighted real-space correlation function was also in semiquantitative agreement with that obtained from the experimental results. The distribution of the coordination number for O around P and P around O showed that most P atoms form tetrahedral PO4 units in the glass, and that three-fifths of O atoms are bridging oxygen atoms. O-B, and the remaining are terminal oxygen atoms, O-T. The pair distribution functions for P-O-B and P-O-T show that the PO4 units have three long P-O-B bonds and one short P-O-T bond. We have concluded that the short-range structure obtained for vitreous P2O5 agrees well with the picture derived from many experiments. This fact indicates that the short-range structure of vitreous P2O5 can be described mainly by both charge ordering and packing based on the differences in ionic charge and size between cation and anion.

DOI： 10.2320/matertrans.42.2242

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The structures of K2O-B2O3 glasses and melts have been studied by high-temperature Raman spectroscopy. With an increase in the K2O content and with increasing temperature, the boroxol rings, which only consist of B theta (3) triangular units, were converted into pentaborate groups which consist of B theta (4) tetrahedral (theta = bridging oxygen atom) and B theta (3) units in the 10 and 20 mol% K2O-B2O3 glasses/melts. In the 30 mol% K2O-B2O3 glass/melt, the Raman spectra indicated a structural change in the borate species from B theta (4) tetrahedral units to metaborate, B theta O-2(-), triangular units with non-bridging oxygen with increasing temperature. The fraction of four-coordinated boron atoms, N-4, obtained from deconvolution of the Raman bands was gradually reduced above the glass transition temperature and converged to a constant value over 1400 K. This phenomenon could be explained by a thermodynamic process. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(01)00752-9

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The effect of tensile stress on the hypersonic wave velocities of polymer films was investigated using a Brillouin scattering method. From the real-time measurements during the tensile test, an interesting behavior of the longitudinal wave velocity has been observed. By comparing the velocity profile with the stress-strain curve, velocity changes indicate that the small scale deformation of the film propagates from the edge to the center and gradually spreads. These results point out the possibility of the Brillouin scattering method as a useful tool for nondestructive and real-time measurement of the stress and deformation in the sample.

DOI： 10.1143/JJAP.40.3511

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We have studied the structure of (xK(2)O(.)yAl(2)O(3))(.)2B(2)O(3) (x+0.75, 0.5, 0.45, x+y=1) and (xCaO(.)yAl(2)O(3))(.)2B(2)O(3) (x=0.75, 0.5, 0.375, x+y=1) glasses by soft x-ray XAFS measurements. There are 6 oxygen atoms around K and Ca in (CaO-Al2O3)(.)2B(2)O(3) glasses and K(2)O(.)2B(2)O(3) glass and 4.2-4.7 aroudn K in (K2O-Al2O3)(.)2B(2)O(3) glasses. The mean K-O and Ca-O distances are 2.74-2.78 and 2.40-2.44 Angstrom, respectively. The fraction of AlO6 as AlO4 is 53.6% in (0.75 CaO(.)0.25 Al2O3)(.)2B(2)O(3) glass and 23.3% in (0.375 CaO(.)0.625 Al2O3)(.)2B(2)O(3) glass, respectively. These results are in good agreement with our MD calculations.

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Molecular dynamics (MD) simulations have been performed for alkaline earth borate glasses using purely ionic potential functions. We present some results concerning the pair correlation functions, g(r), the running coordination numbers n(r), the distance distribution functions for B with its third or fourth nearest neighbour O ions, p(r(BO)) and the angular distribution functions for O-(B) over cap O, p(theta (OBO)). The composition dependence of the most probable distances between adjacent O and Ca or Ba and the mean coordination number of O around Ca or Ba is in good agreement with our XAFS results.

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The structure of pressure compacted vitreous B(2)O(3) has been studied by neutron diffraction using the LAD spectrometer at the ISIS spallation pulsed neutron source to provide the necessary high real space resolution to investigate small changes in interatomic distances and coordination numbers. The data are in excellent agreement with previous x-ray diffraction results brit of much higher real space resolution. The density compaction results from the break tip of boroxol groups with increasing pressure but, once the pressure is released. pressure compacted vitreous B(2)O(3) relaxes over a period of several days during which the original boroxol ring fraction is restored

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The short-range structure of K2O-9TeO(2) and K2O-4TeO(2) in amorphous states such as glass and melt has been investigated by X-ray diffraction (XRD) and semi-empirical molecular orbital calculation (AM1-MOPAC method). The structure of amorphous alkali tellurites consisted of the TeO4 trigonal bipyramids (tbp) and the TeO3 trigonal pyramids (tp). Confirmed in the present work is that the TeO4 trigonal bipyramids characteristics of TeO2-based glasses transform into TeO3 trigonal pyramids with increasing modifier K2O content and a rise of temperature. The usage of XRD and MOPAC enabled us to comprehend in some details what to happen in phase transition from glasses to melts, (C) 2000 Elsevier Science S.A. All rights reserved.

DOI： 10.1016/S0925-8388(00)01080-X

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

A curing process of epoxy adhesive layers has been investigated by an ultrasonic pulse spectroscopy and a Brillouin scattering technique. Observed longitudinal elastic wave velocities in the curing layer depended on the velocity in the prepolymer used. From this result, we suggest a simple nondestructive method for the estimation of sample T-g (glass transition temperature) during cure. The estimated T-g values were in good accordance with the T-g values easured by differential scanning calorimetry.

DOI： 10.1143/JJAP.39.2950

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOCIETY INC  

We have investigated the thermal conductivity of some molten alkali metal halides by molecular dynamics simulation and the Green-Kubo formula in an equilibrium. state. The calculated results agreed quantitatively with the experimental ones within 7-55%. On the other hand, they were qualitatively in good agreement with each other: their temperature dependence was weakly negative similarly to most of simple liquids while they decreased as the mass of cation or anion increased.

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The structure of alkali berate glasses and melts with 10, 20 and 30 mol% K2O have been studied by high-temperature Raman spectroscopy. Not only with an increase of K2O content but also with increasing temperature, boroxol rings in the potassium berate glass/melt have converted to pentaborate groups which consist of BO4- tetrahedra (O = bridging oxygen atom) and metaborate, BO2O-, triangular units. Furthermore, Raman spectra have indicated a structural change of berate species from BO4 tetrahedral units to BO3 triangles with non-bridging oxygen with increasing temperature in 30 mol% K2O-B2O3 glass. The fraction of four-coordinated boron atoms, N-4, was obtained and found to exhibit a gradual reduction above the glass transition temperature in this glass.

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We have evaluated the thermal conductivity in SiO2 glass at elevated temperature by Molecular Dynamics (MD) calculation and the Green-Kubo formula in an equilibrium state using the purely ionic pair interaction potential functions. The estimated uncertainty for the thermal conductivity was +/-25% at 981 K and +/-8% at 1978 K. Our results were in agreement with those of the experiment by Wray and Connolly within 20-35% at 981:1978 K. The calculated thermal conductivity showed a positive temperature dependence, which also agreed with the experimental results. It was found that the calculated values did not depend on total ion number in the system. We have concluded that semiquantitatively reliable results were given by the present MD calculation with the potential functions.

DOI： 10.2320/matertrans1989.40.1258

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Cerium zirconium oxides with the composition CeZrO4 were prepared by oxidizing in O-2 at 873 K precursors with the composition CeZrO3.5+delta (delta < 0.3). The precursors were prepared by reducing the t'-(Ce0.5Zr0.5)O-2 phase at 873 less than or equal to T-red less than or equal to 1573 K. The CeZrO4 compounds together with the precursors were characterized by powder X-ray diffraction and IR and Raman spectroscopies. In the case of 1323 less than or equal to T-red. less than or equal to 1573 K, the precursors were identified as having the pyrochlore-type Ce2Zr2O7+2 delta phase with delta < 0.06. When the reduction temperature was decreased, the ordering level between Ce and Zr ions was decreased in the pyrochlore-type phase. The CeZrO4 compounds obtained by oxidizing the pyrochlore-type precursors were identified as the kappa-CeZrO4 phase in which Ce and Zr ions are in an ordered arrangement similar to that of the pyrochlore-type structure. The space group of the K phase was not the same as that of the pyrochlore-type structure. In the case of T-red less than or equal to 1123 K, cubic CaF2-related-type (Ce0.5Zr0.5)O(3.5+delta)/2 phases with 0.1 < delta < 0.3 were obtained. When the precursor obtained at T-red. = 1123 K was oxidized, a tetragonal phase appeared, but its Raman spectrum was different from that seen in the t' phase. This phase was identified to be a novel t(meta)'-(Ce0.5Zr0.5)O-2 phase, because it transformed into the t' phase by annealing above 1173 K under an O-2 atmosphere. When the precursor obtained at T-red. = 873 It was oxidized, the t'-(Ce0.5Zr0.5)O-2 phase identical to the starting sample appeared. The structural difference between t(meta)' and t' phases was estimated to be in their oxygen parameter, z, for the 4d site in the space group of P4(2)/nmc. The oxygen parameter for the t(meta)' phase is closer to 0.25 than that for t' phase. It was shown that the temperature and holding time for precursor preparation and the oxygen content delta are important factors for the structure of the reoxidized CeZrO4 compound. (C) 1999 Academic Press.

DOI： 10.1006/jssc.1999.8420

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The structural change of K2O-TeO2 glasses (xK(2)O:TeO4, x:5, 10, 15, 20, 25 and 30 mol%) from room temperature to a temperature higher than the melting point (T-m) was studied by the use of Raman spectroscopy, XRD (X-ray diffraction), X-ray RDF (radial distribution function) and XAFS (X-ray absorption fine structure) spectroscopy. The Raman results indicated that TeO4 trigonal bipyramid (tbp) units convert to TeO3 trigonal pyramid (tp) units with increasing temperature and by the addition of K2O to the K2O-TeO2 glasses. We found that a 10K(2)O.90TeO(2) (mol%) glass mainly consists of TeO4 tbp unit, while 20K(2)O.80TeO(2) (mol%) and 30K(2)O.90TeO(2) (mol%) glasses are composed of the mixture of TeO4 tbp and TeO3 tp units. The high-temperature XRD and X-ray RDF results are in agreement with the results of high-temperature Raman spectroscopy. Furthermore, the XAFS spectroscopy shows that potassium ions have a similar local structure in all of the K2O-TeO2 glasses studied. (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3093(99)00392-0

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We have investigated the calculation conditions necessary for precise and efficient evaluation of the thermal conductivity of a molten salt based upon the equilibrium Green-Kubo formula by molecular dynamics simulation. The suitable parameters are also presented for the Ewald sums in the calculations of the interionic force and the energy current. The statistical error was estimated at +/-10 % under the calculation conditions. The dependence of the calculated results was examined on various calculation conditions. The number of time steps of at least 50000, which corresponds to 200 ps, was required in order to obtain a fully converged value of the time integral of the correlation functions. No significant dependence was found on the number of particles used in the simulated system compared with the statistical error. The dependence on the time step, the interval between time origins when the correlation functions were sampled, and the upper integral limit for the correlation functions was negligible compared with the statistical error. The addition of a small velocity vector to the ions, however, significantly influenced the calculated value of the thermal conductivity.

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Brillouin and Raman scattering measurements have been applied for the investigation of GeO2 glasses densified under high pressures up to 9 GPa at 673 K. The density of obtained glasses increases with an increase of applied pressure. It increases significantly around 3 GPa, however shows a peak at 6 GPa. A significant increase is also observed in hypersonic wave velocity, and longitudinal and shear moduli around 3 GPa. These results are well explained by amorphous-amorphous transition. In Raman scattering measurement, vibrational modes illustrate continuous changes of local structures with increasing applied pressures up to 9 GPa. Boson peaks show a maximum around 3 GPa, which indicates the minimum correlation length. These data suggest a change in the intermediate-range structure.

DOI： 10.1143/JJAP.38.3062

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Wave properties (wave velocity and attenuation) in epoxy adhesive layers during cure were investigated. Longitudinal and shear wave properties in the GHz region were measured by the Brillouin scattering technique using 90 degrees A-scattering geometry. The longitudinal and shear wave properties showed similar changes during cure. Compared with the ultrasonic wave properties in the MHz region, a clear frequency dispersion could be seen during cure, in the glass transition region. It is supposed that this dispersion results from a strong alpha relaxation. Longitudinal modulus and shear modulus were also obtained from the longitudinal and shear wave velocities. The longitudinal modulus was always proportional to the shear modulus during the entire curing process.

DOI： 10.1143/JJAP.38.3175

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The influence of two Ti-precursors, TiO2 (anatase) and H2TiO3 (beta-titanic acid), on the purity and particle size of BaTiO3 powders prepared via hydrothermal synthesis is discussed. Amorphous H2TiO3 was found to be an excellent Ti-precursor material and offers several advantages over crystalline anatase. Phase pure powders which have small particle sizes, ca. 40-80 nm and narrow particle size distributions can be prepared at 180 degrees C after 24 h using H2TiO3 as a precursor material. Although the initial reaction is very fast, ca. 90% yield after 8-10 h, extended reaction periods at 180 degrees C are required in order to drive the reaction to completion. Lowering the reaction temperature from 180 to 85 degrees C does produce powders with even smaller particle sizes, however, very long reaction periods are required, e.g. > 72 h, to ensure complete reaction. Raman spectra of as-prepared and heat treated (1000 degrees C) powders with average particle sizes as small as ca. 29-40 nm indicate asymmetry within the TiO6 octahedra of the BaTiO3 lattice. These results contradict the widely cited 'critical' particle size theory for the stabilisation of the cubic polymorph, at least for particle sizes greater than ca. 20-40 nm. As-prepared powders contain many defects, primarily in the form of lattice OH- ions. Preliminary ac impedance spectroscopy data on samples heat treated to remove lattice hydoxyl ions demonstrate these materials to be modest proton conductors.

DOI： 10.1039/a805756g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：FREUND PUBLISHING HOUSE LTD  

Wave velocities and elastic moduli of B2O3 alkali oxide glasses have been obtained by a Brillouin scattering experiment. These concentration dependences increase with increasing alkali concentration Temperature dependence of the phonon frequency for B2O3-K2O glasses showed an obvious change at their glass transition temperature.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

The local structure obtained from calcium K-edge XAFS experiments in CaO-B2O3 glasses is described. The average coordination number of oxygen around Ca2+ ions and the mean distance for Ca-O are found to be approximately 6 and 2.40 similar to 2.41 Angstrom, respectively. The Ca2+ ions have a disordered octahedral geometry and a strong preference to reside in vicinity of negatively charged non-bridging and bridging oxygen in the large cages of the B-O network structure. The XAFS results are in good agreement with MD simulation results.

DOI： 10.7567/JJAPS.38S1.148

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

The structure at room temperature and structural change from room temperature to the temperature above melting point (T-m) of K2O-TeO2 glasses were studied by the use of XAFS spectroscopy, high temperature Raman spectroscopy, high-temperature XRD and X-ray RDF (Radial. Distribution Function). XAFS spectroscopy has indicated that K2O-TeO2 glasses consist of both TeO4 trigonal bipyramid (tbp) units and TeO3 trigonal pyramid (Cp) units, and high-temperature Raman results have indicated that TeO4 tbp units convert to TeO3 tp units with the increase of temperature and by the addition of K2O in the K2O-TeO2 glasses. The high-temperature XRD and X-ray RDF results were in good agreement with the results of the high-temperature Raman spectroscopy. Furthermore, the XAFS spectroscopy has shown that potassium ions have a similar local structure in all K2O-TeO2 glasses studied.

DOI： 10.7567/JJAPS.38S1.160

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

Brillouin scattering measurement has been carried out in B2O3-Li2O-LiCl glass. The observed Brillouin frequency shift increases with the addition of a modifier element (both Li2O and LiCl). However, if the ratio of B2O3 to the modifier is a constant, Brillouin frequency shift decreases with increasing LiCl concentration. In order to obtain additional information on the local structure, Raman scattering and density measurements have been performed. Raman spectra have been observed as a distinct peak near 780 cm(-1) which shows the formation of tetrahedrally coordinated boron. By increasing LiCl concentration, the Raman band near 780 cm(-1) decreases, but the band near 806 cm(-1) increases. This illustrates the breathing motion of oxygen in a boroxol ring. This result indicates that LiCl mainly modifies the B2O3 network without forming tetrahedrally coordinated boron.
By comparing the glass transition temperature (T-g) obtained from the temperature dependence of the Brillouin frequency shift with that from the results of differential scanning calorimetry (DSC) measurement, it is observed that both the values of T-g almost agree, The concentration dependence of T-g is discussed in terms of viscosity.

DOI： 10.1143/JJAP.37.2808

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

Ultrafine BaTiO3 prepared by a decomposition of an organometallic crystal with unity of Ba/Ti ratio (sol-crystal method) has been characterized. While the as-prepared product resulting from the decomposition of the organometallic crystal at room temperature was BaTiO3 with pseudo-cubic structure, the well-crystallized tetragonal polymorph was obtained by firing the as-prepared product above 1000 degrees C. Residual organic compounds, CO32- and OH- ions in the samples prevent the grain growth and tetragonal distortion of BaTiO3. We obtained quite higher room temperature permittivity (3700) at 1 kHz for the sample fired at 1200 degrees C than that (630) prepared by conventional solid-state reaction starting from BaCO3 and TiO2. Such a high value was probably due to the accomplishment of homogeneous cation stoichiometry, which was achieved by this preparation method via the organometallic crystal with stoichiometric Ba/Ti ratio.

DOI： 10.1023/A:1018697706704

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

The temperature dependence of elastic properties in a common epoxy prepolymer was investigated using Brillouin scattering and ultrasonic pulse spectroscopy. In the GHz region, the Brillouin shift frequency curve showed a sharp kink at about 250 K; which was in good accordance with T-g observed by DSC. The D-90R function calculated from the Brillouin shift frequency showed a clear dispersion at temperatures near 350 K, at which a broad peak of the Brillouin linewidth was observed. In the MHz region, ultrasonic wave attenuation also showed a peak near 285 K. Assuming that these changes result from the a relaxation in the glass transition region, the frequency-temperature behavior of the peaks was discussed in connection with the a relaxation in fully cured epoxy resin.

DOI： 10.1143/JJAP.36.2976

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

The solubility of NiO in 52mol% Li2CO3-48mol%Na2CO3 containing alkaline earth carbonate (CaCO3, SrCO3 and BaCO3) was mesured at 650 degrees C under dry CO2 atmosphere. The additives were up to 17mol%. The addition of alkaline earth carbonate reduced the solubility of NiO in half.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The structures of glassy Li-7X-KX-CsX-BaX2 (X=Cl, Br, and I) have been investigated by means of pulsed neutron diffraction experiment. The obtained total radial distribution functions were discussed with the help of the molecular dynamics simulation based on the Tosi-Fumi potential. The Li-X (X = Cl, Br, and I) distances in the three glasses are 2.37, 2.49, and 2.70 angstrom, respectively, which are 0.2-0.3 angstrom shorter than those in the rocksalt-type LiX crystals. For each system, it is found that the coordination number of the X- ions around the Li+ ions is about four when only the closely contacting X- ions are counted. Because of the 1:1 monovalent character of the present systems, the first coordination shell around the Li+ ions has the ill-defined outer extent, compared with the 4:2 and 2:1 charged systems such as SiO2 and ZnCl2. This causes the increase of the coordination number, from four to six, when all the near-neighbor X- ions are counted as the surrounding ions.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Molten carbonate fuel cells with four alkali carbonate eutectic mixtures of Li2CO3/Na2CO3/K2CO3 in the proportions 62/0/38, 43/0/57, 43/32/25 and 52/48/0 (mol %), have been operated using electrolyte matrices fabricated by tape casting. When the ratio of electrolyte volume to matrix pore volume was optimized, all of the test cells gave similar good performance.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

Molten-carbonate fuel cells with two types of alkali carbonate mixture as the electrolyte have been operated. The resulting cell performances have been compared in order to optimize the composition of each carbonate mixture. One electrolyte type is a mixture of the high lithium eutectic ((Li0.62K0.38)2CO3) and an alkaline-earth carbonate, while the other is a mixture of the lithium-sodium eutectic ((Li0.52Na0.48)2CO3) and an alkaline-earth carbonate. Additions of CaCO3, SrCO3 and BaCO3 have been used. A small amount of each alkaline-earth carbonate to both eutectics does not influence the cell performance. On the other hand, larger amounts reduce the cell performance. The required content of each additive to provide optimum cell performance depends on both the additive itself and the host eutectic. The temperature dependence of cell performance in the presence of the different additives has also been investigated. There is little difference between the behaviour of ((Li0.62K0.38K0.38)2-Ca)CO3, ((Li0.62K0.38)2-Ba)CO3 and ((Li0.52Na0.48)2-Ca)CO3. By contrast, high temperature dependence was found for ((Li0.62K0.38)2-Sr)CO3, ((Li0.52Na0.48)2-Sr)CO3 and ((Li0.52Na0.48)2-Ba)CO3.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Polarized and depolarized Raman scattering measurements have been performed for the stretching vibrational mode of OH- ion in molten MOH (M = Li, Na, K, Rb, and Cs). Vibrational and rotational autocorrelation functions, C-nu-(t) and C(r)(t), have been evaluated from Fourier transformation of the spectra. The relaxation rate of C-nu-(t) becomes more rapid and the asymmetry of the isotropic band becomes larger as the cation size becomes smaller. These results can be interpreted in terms of the coulombic interaction. Applying the two-parameters model based on the Kubo line shape theory to the observed spectra, it is suggested that the OH- ion apparently follows the fast modulation regime due to the libration of OH- ion. For all melts, the C(r)(t) has oscillatory character caused by libration of the OH- ion at small t < 0.1 ps. The function shows ordinary exponential decay at large t > 0.1 ps. The cation dependence of the libration at t < 0.1 ps and the rotational diffusion process at t > 0.1 ps were investigated separately. The larger the cation size becomes, the longer and larger the period and amplitude of the libration become, respectively. This indicates that in the libration process the OH- ion seems to have more extended space in the melt as the cation size becomes larger. With respect to the rotational diffusion process, the rate shows rather small cation dependence.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

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Language：Japanese   Publisher：The Physical Society of Japan  

<p>分子動力学（MD）シミュレーションによって単純液体の自己拡散係数と粘性率のスケーリング則を導出し、それらを組み合わせることで分子スケールにおけるStokes-Einstein則を導出した。さらに単純液体にフラーレンナノ粒子を希薄量溶存させたMD計算も行い、流体力学領域との接続性について考察した。</p>

DOI： 10.11316/jpsgaiyo.72.1.0_3200

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Language：English   Publishing type：Article, review, commentary, editorial, etc. (international conference proceedings)   Publisher：DESTECH PUBLICATIONS, INC  

The thermal conductivities of molten NaCl have been evaluated at temperatures from 1100 K to 1400 K by using molecular dynamics simulation with dipole interaction model. The results are in closer agreement with the experimental results by using the forced Rayleigh scattering method in comparison with previous calculation results by using the Fumi-Tosi potential model. While the results show an apparently negative temperature dependence, further calculations regarding both temperature dependence under constant density and density dependence under constant temperature reveal that the thermal conductivity depends strongly on density but only weakly on temperature in molten NaCl.

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Language：English   Publisher：Steering committee of symposium on ultrasonic electronics  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (other)   Publisher：電気化学会溶融塩委員会  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Epoxy resin has been used in the large field of engineering, for example, insulation and adhesive layers. The elastic properties of adhesive layers, however, have not been hardly investigated before. In addition, the final properties of cured layers, are closely related to the curing process. The investigation of elastic properties of curing resins, therefore, become very important to know the final properties of cured resins. In this study, We have evaluated the elastic properties of epoxy adhesive layers during cure by measuring ultrasonic wave velocity and attenuation in the GHz region.

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Language：Japanese   Publisher：Steering committee of symposium on ultrasonic electronics  

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Language：English   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

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Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪大学中之島センター  

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Venue：名古屋大学ES総合館ESホール  

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Venue：San Francisco, California, USA  

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