石川 毅彦

In order to investigate the progression of a core meltdown accident, it is necessary to understand the behavior of molten core materials. Zr-Fe alloys are one of the low-melting-temperature liquid phases that are thought to form in the early stages of bundle degradation. The objective of this study is to measure the thermophysical properties of Zr-Fe liquid alloys. Alloy samples with a composition of Zr1-xFex (x = 0.12, 0.24, and 0.50) were synthesized by arc melting, and their density, viscosity, and surface tension were measured using an electrostatic levitation technique. The results indicate that the density of Zr-Fe liquid alloys can be estimated by a linear combination of the measured or extrapolated densities of pure Zr and Fe. The viscosities of the Zr-Fe liquid alloys can be roughly estimated by extrapolating those of Zr to lower temperatures, although this method tends to underestimate the viscosity of alloys, especially for eutectic compositions. The values of the Zr-Fe liquid alloys' surface tensions are close to those of pure Zr.

Total hemispherical emissivity (epsilon(T)) and constant pressure heat capacity (C-p) of molten Nb, which has a high melting point, was measured using FT-IR combined with an electrostatic levitator. In order to heat the sample to temperatures higher than 2000 degrees C and avoid chemical reactions between the sample and a crucible, a containerless method was needed. By applying these methods, the measured epsilon(T) of molten Nb at the melting temperature was 0.29, and the C-p was calculated as 41.9 J . mol(-1) . K-1. Both data showed good agreement with the literature values. In addition, the result was compared with the Drude model and the difference of emissivity between Zr and Nb was discussed. (C) 2015 Elsevier Ltd. All rights reserved.

Bonding characteristics of liquid boron at 2500 K are studied by using high-resolution Compton scattering. An excellent agreement is found between the measurements and the corresponding Car-Parrinello molecular dynamics simulations. Covalent bond pairs are clearly shown to dominate in liquid boron along with the coexistence of diffuse pairs. Our study reveals the complex bonding pattern of liquid boron and gives insight into the unusual properties of this high-temperature liquid.

In this paper is presented a microgravity experiment system utilizing a high altitude balloon. The feature is a double shell structure of a vehicle that is dropped off from the balloon and a microgravity experiment section that is attached to the inside of the vehicle with a liner slider. Control with cold gas jet thrusters of relative position of the experiment section to the vehicle and attitude of the vehicle maintains fine microgravity environment. The design strategy of the vehicle is explained, mainly referring to differences from the authors' previous design. The result of the flight experiment is also shown to evaluate the characteristics of the presented system.

In order to measure the surface tension of high temperature melts with high viscosity, a sample rotation method was developed. An electrostatically levitated melt was spun with a rotating magnetic field, and the shape evolution of the sample was observed. Especially, the bifurcation behavior (shape transformation from axisymmetric to non-axisymmetric) was closely monitored by a high speed camera. The experiments confirmed that the rotation frequency at the bifurcation could be precisely measured by monitoring the fluctuation of the power of the beam of a He-Ne laser reflected at the sample surface, and thus, the surface tension could be calculated based on the theory by Brown and Scriven. The validity of this measurement technique was demonstrated with ZrCoAl bulk glass forming alloy. (C) 2014 The Japan Society of Applied Physics

The structure of high-temperature liquids is an important topic for understanding the fragility of liquids. Here we report the structure of a high-temperature non-glass-forming oxide liquid, ZrO2, at an atomistic and electronic level. The Bhatia-Thornton number-number structure factor of ZrO2 does not show a first sharp diffraction peak. The atomic structure comprises ZrO5, ZrO6 and ZrO7 polyhedra with a significant contribution of edge sharing of oxygen in addition to corner sharing. The variety of large oxygen coordination and polyhedral connections with short Zr-O bond lifetimes, induced by the relatively large ionic radius of zirconium, disturbs the evolution of intermediate-range ordering, which leads to a reduced electronic band gap and increased delocalization in the ionic Zr-O bonding. The details of the chemical bonding explain the extremely low viscosity of the liquid and the absence of a first sharp diffraction peak, and indicate that liquid ZrO2 is an extremely fragile liquid.

A pressurized electrostatic levitation furnace (PESLF) was used to measure the density of calcium aluminate with a composition of CaAl2O4 (CA) over a wide temperature range of 673-2300 K with an ultraviolet-based imaging technique. The density was measured in various gas atmospheres of O-2, air and N-2 at a chamber pressure of 4 x 10(5) Pa. The measurements under these different atmospheres suggested that the density increased when decreasing the oxygen atmosphere. The density obtained under N-2, air and O-2 gas atmosphere can be expressed as rho(T) N-2 = 2.91 x 10(3)-0.073(T-T-m), rho(T) air = 2.76 x 10(3)-0.075(T-T-m) and rho(T) O-2 = 2.70 x 10(3)-0.1(T-T-m) (kg m(-3)) (+/- 2%) with T-m = 1878 K, over the range 2200 to 673 K.

This review briefly describes the vacuum electrostatic levitation furnace developed by JAXA and the associated non-contact techniques used to measure the density, the surface tension and the viscosity of materials. The paper then presents a summary of the data taken with this facility in the equilibrium liquid and non-equilibrium liquid phases for the six platinum group metals (pgms): platinum, palladium, rhodium, iridium, ruthenium and osmium over wide temperature ranges that include undercooled and superheated phases. The presented data (density, surface tension and viscosity of Pt, Rh, Ir, Ru and Os and density of Pd) are compared with literature values.

Crystal-liquid interfacial free energy is important to understand in crystal study, for example, nucleation, crystal growth, and vitrification. Here, we report the nanosized nucleus-supercooled liquid interfacial free energy of early and late transition liquid metals using the electrostatic levitation (ESL) technique and classical homogeneous nucleation theory (CNT). For the estimation of the interfacial free energy, we obtained thermophysical parameters of the transition liquid metals (Ti, Fe, Ni, Zr, Nb, Rh, and Hf), such as hypercooling limit (Delta T-hyp), specific heat (C-p), total hemispherical emissivity (epsilon(T)), and density (rho). The estimated interfacial free energies of Ti, Ni, and Zr agreed well with a previous report having similar hypercooling limit and fusion enthalpy, while Fe, Nb, Rh, and Hf show different values from the report. This reflects the importance of accurate measurement of the two quantities. The obtained Turnbull's coefficients (alpha) of the liquid metals is higher than 0.45. The interfacial free energy is discussed with configurationally different local order of the crystal and the liquid.

The viscosities of molten InSb, GaSb, and InxGa1-xSb (x = 0.2 and 0.4) were measured as a function of temperature using an oscillating viscometer for fundamental understanding of the physical properties for fabricating high quality InGaSb multicomponent semiconductor crystals. The measured values showed good Arrhenius linearity for InSb, GaSb, and InxGa1-xSb samples. The absolute values of the viscosity for InSb and GaSb agreed with a previous study. Also, it is suggested that the absolute values of the viscosity among the compounds are quite similar, and the results can be associated with their crystal structures.

The thermal properties of InSb, GaSb and InxGa1-xSb, such as the viscosity, wetting property, and evaporation rate, were investigated in preparation for the crystal growth experiment on the International Space Station (ISS). The viscosity of InGaSb, which is an essential property for numerical modeling of crystal growth, was evaluated. In addition, the wetting properties between molten InxGa1-xSb and quartz, BN, graphite, and C-103 materials were investigated. The evaporation rate of molten InxGa1-xSb was measured to determine the affinity of different sample configurations. From the measurements, it was found that the viscosity of InxGa1-xSb was between that of InSb and GaSb. The degree of wetting reaction between molten InxGa1-xSb and the C-103 substrate was very high, whereas that between molten InxGa1-xSb and quartz, BN, and graphite substrates was very low. The results suggest that BN and graphite can be used as materials to cover InSb and GaSb samples inside a quartz ampoule during the microgravity experiments. In addition, the difference of the evaporation rate of molten InxGa1-xSb, GaSb, and InSb was small at low, and large at high temperature. (C) 2013 COSPAR. Published by Elsevier Ltd. All rights reserved.

Electrostatic levitators have been around for more than 30 years and have become mature tools for the material science community. Originally developed as positioners for materials and fluid science experiments in space, they saw a myriad of offsprings throughout the world for ground-based research, not only in space agencies but also in governmental laboratories, in universities and in the industry. Electrostatic levitatoes eliminate any physical contact with a container allowing to process and study corrosive or high temperature materials in their solid or liquid phases. Moreover, heterogeneous contamination from the container being avoided, it is possible to reach and maintain supercooled and metastable phases. This, in turns, permits a host of fundamental and applied studies. The nucleation and solidification phenomena can be scrutinized, the atomic structure and dynamic of liquid and metastable phases can be probed and the physics of molten drops could be investigated. On a more applied standpoint, the measure of thermophysical properties and the synthesis of materials with new properties are also possible with current facilities. This paper first describes the principle of electrostatic levitation and retraces the development of various facilities throughout the world, focusing on the advances made by each research group. The capabilities of electrostatic levitation for materials processing and synthesis under different environments are then presented. The paper successively covers in length its contribution for the measurements of thermophysical properties and for fundamental studies using high energy particle beams. Finally, the outlook of electrostatic levitators and its attractiveness for space experiments in materials sciences are discussed. (C) 2013 Elsevier B.V. All rights reserved.

Crystal growth of alloy semiconductor has been under investigation at the International Space Station (ISS) to investigate growth kinetics at the solid-liquid interface, because microgravity can suppress the natural convection. In this study, we focused on InGaSb which is one of the promising ternary alloy semiconductors. As a preliminary experiment, wetting angle between the InGaSb and the materials of the ampoule and cartridge, such as quartz, carbon sheet, BN, and C-103 alloy, were measured to check their affinity of the configuration. The InGaSb exhibited much higher wetting ability on the C-103 substrate than that on the other substrates (quartz, BN, and graphite), and this result suggested C-103 can prevent leakage of the InGaSb samples in case the ampoule collapses in the cartridge. On the other hand, BN and graphite exhibited low wetting abilities with InGaSb; therefore, they are suitable materials for the ampoule because they do not significantly affect the InGaSb crystal growth. In another preliminary experiment, concentration of Te dopant, which was added to make striation in the grown crystal, was measured using inductively coupled plasma mass spectrometry (ICP-MS). It is confirmed that Te concentrations were relatively higher at the striation area.

本研究では，混晶半導体であるInxGa1-xSb (x =0, 0.2, 0.4, 1.0) 融液の粘度を回転振動法により測定した．粘度は結晶成長の数値計算に必須のパラメータの1つであり，数値計算の精度向上には粘度の組成依存性が必要となる．測定の結果，InxGa1-xSbにおいてもInSbやGaSbと同様に粘度はアレニウスの直線性を示すことが示された．また，InxGa1-xSbの粘度はGaSb，InSbの間の値となった．本研究は，国際宇宙ステーションで行われる混晶半導体結晶成長実験に関する数値計算のパラメータとして使用することを目的としている．

Rare-earth aluminate (RAlO3, R = La-Lu and Y) glass and crystalline phases were prepared by containerless levitation in an aerodynamic levitation furnace. In the RAlO3 system, La, Nd and Sm aluminum perovskites solidified as glass and Eu-Lu and Y aluminum perovskites solidified as crystalline phases. The glass forming region decreased with decreasing ionic radius of the rare-earth element. Scanning electron microscopy images and x-ray diffraction results revealed the formation of a single RAlO3 phase from the undercooled melt. The glass transition temperature, T-g, and density increased and the molar volume decreased with decreasing rare-earth element ionic radius. The refractive index at 589 nm exceeds 1.85 in each composition and a transparency of approximately 72% was achieved for the LaAlO3 glass. (C) 2013 AIP Publishing LLC.

Containerless levitation technique, where the undercooling can be treated as one of the major thermodynamic parameters, was used to study the influence of oxygen partial pressure (PO2) on the microstructure and physical properties of rare-earth orthoferrites RFeO3 (where R=Rare-earth element) in the PO2 ranges from 105 to 101Pa. The microstructure of the as-solidified samples changed into orthorhombic RFeO3 (o-RFeO3), metastable hexagonal RFeO3 (h-RFeO3), and Fe2+-containing RFe2O4 and a new metastable R3Fe2O7 phases with decreasing PO2. The effect of PO2 on the magnetic properties was indicated as that the saturation magnetization gradually increased for R = La to Yb and decreased for R = Lu with decreasing PO2 due to the formation of metastable and magnetic phases such as Fe3O4 and Fe.

Liquid state provides functions such as matter transport or a reaction field and plays an important role in manufacturing processes such as refining, forging or welding. However, experimental procedures are significantly difficult for an observation of solidification process of iron and iron-based alloys in order to identify rapid transformations subjected to fast temperature evolution. Therefore, in order to study the solidification in iron and iron-based alloys, we considered a combination of high energy X-ray diffraction measurements and an electrostatic levitation method (ESL). In order to analyze the liquid/solid fraction, the solidification of melted spherical specimens was measured at a time resolution of 0.1 seconds during rapid cooling using the two-dimensional time-resolved X-ray diffraction. Furthermore, the observation of particle sizes and phase identification was performed on a trial basis using X-ray small angle scattering with X-ray diffraction. © Published under licence by IOP Publishing Ltd.

JAXA has been utilizing Japanese Experiment Module "Kibo" of the International Space Station (ISS) since August 2008 and has obtained significant results through its first phase utilization. The primary purpose of this phase was to examine Kibo's capability as a space laboratory as well as to conduct selected scientific themes. In the second phase which began in 2010, we plan to challenge variety of themes to contribute to the society such as practical researches aiming industrial applications, technology demonstration for future space activities, and cultural and educational precursor experiments. The Electrostatic Levitation Furnace (ELF) is one of the experiment facilities for materials science, which will be on board Kibo in the near future. A unique feature of ELF is to levitate a sample material inside the furnace by means of Coulomb's force throughout the fusion/solidification experiments. By utilizing this capability JAXA plans to study thermo-physical properties of many kinds of the oxides which cannot be measured on earth. In addition, creation of new materials is another objective of space experiments using ELF. In the absence of gravity ELF can generate the ultimate environment for the materials, which is expected to contribute to a new discovery. This paper shows a detailed feature of ELF and its capability as well as typical experiments to be conducted in Kibo for the purposes of scientific research and industrial applications.

Viscosities of tungsten, rhenium, osmium, tantalum, and molybdenum have been measured by the oscillation drop method with an improved procedure. The measured data exhibit less-scatter than our previous measurements. Viscosity at the melting temperature of the investigated metals showed a good agreement with literature values and some predicted values. © 2013 Elsevier Ltd. All rights reserved.

A spectral emissivity measurement system combined with an electrostatic levitator was developed for high-temperature melts. The radiation intensity from a high-temperature sample was measured with a multichannel photospectrometer (MCPD) over the 700-1000 nm spectral range, while a Fourier transform infrared spectrometer (FTIR) measured the radiation over the 1.1-6 mu m interval. These spectrometers were calibrated with a blackbody radiation furnace, and the spectral hemispherical emissivity was calculated. The system's capability was evaluated with molten zirconium samples. The spectral hemispherical emissivity of molten zirconium showed a negative wavelength dependence and an almost constant variation over the 1850-2210 K temperature range. The total hemispherical emissivity of zirconium calculated by integrating the spectral hemispherical emissivity was found to be around 0.32, which showed good agreement with the literature values. The constant pressure heat capacity of molten zirconium at melting temperature was calculated to be 40.9 J mol(-1) K-1.

An ice crystal growth experiment was performed on board the International Space Station. The experiment was repeated 134 times with various undercooling conditions. Dendrite crystal growth velocity and tip radius were precisely measured by using a newly developed software. The results are compared with those obtained previously on the ground as well as with those reported by Glicksman et al. for Succinonitrile (SCN). The plot of the dimensionless velocity V as a function of the dimensionless undercooling Delta under microgravity revealed values that were consistently lower than those obtained under 1-G which indicates that thermal convection was suppressed. The plot of the dimensionless radius R-0 as a function of Delta showed a less scattered value. The stability factor sigma* became close to that of SCN when it was calculated using the geometrical mean radius.

In-situ identification of metastable phases formed from the undercooled LuFeO3 melt under controlled oxygen partial pressure Po-2 was studied by x-ray diffraction measurements at a synchrotron radiation source. Real-time observation of the formation and growth of individual phases during the single recalescence of Lu3Fe2O7 and LuFe2O4 phases at Po-2 of 1 x 10(3) Pa has been revealed by a high speed imaging system at 1 kHz. The obtained diffraction pattern of the metastable phase in the LuFeO3 system was consistent with that of the metastable and stable phases reported in the Lu-Fe-O system. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4712124]

Liquid state provides a function of matter transport or reaction field and plays an important role in manufacturing processes such as refining, forging or welding. However, experimental procedures are significantly difficult for an observation of solidification process of iron and iron-based alloys in order to identify rapid changing phenomena subjected to fast temperature evolution. Therefore, in order to study the solidification in iron and iron-based alloys, we considered a combination of high energy X-ray diffraction measurements and an electrostatic levitation method (ESL). ESL allows us to eliminate the confounding high-temperature-environment setup problems because it can levitate the specimen without a vessel in a high vacuum, and so ESL is suited to measure X-ray scattering of high temperatures or undercooled melts. In order to analyze the liquid/solid fraction, the solidification of melted spherical specimens was measured at a time resolution of 0.1 seconds during rapid cooling using the two-dimensional time-resolved X-ray diffraction. The mole fraction of solid phases was analyzed as a function of solidification time at each temperature and experimentally-studied the solidification phenomena for several seconds.

Metallic liquid silicon at 1787 K is investigated using x-ray Compton scattering. An excellent agreement is found between the measurements and the corresponding Car-Parrinello molecular dynamics simulations. Our results show persistence of covalent bonding in liquid silicon and provide support for the occurrence of theoretically predicted liquid-liquid phase transition in supercooled liquid states. The population of covalent bond pairs in liquid silicon is estimated to be 17% via a maximally localized Wannier function analysis. Compton scattering is shown to be a sensitive probe of bonding effects in the liquid state.

Viscosities of several refractory metals (titanium, nickel, zirconium, niobium, ruthenium, rhodium, hafnium, iridium and platinum) and terbium have been measured by the oscillation drop method with an improved procedure. The measured data were less scattered than our previous measurements. Viscosities at their melting temperatures showed good agreement with literature values and some predicted values.

The purpose of "Alloy Semiconductor" crystal growth project is to make clear the factors for crystal growth of a high-quality bulk alloy semiconductor by investigating (1) solute transport in liquid and (2) surface orientation dependence of growth kinetics under microgravity and terrestrial conditions. The temperature gradient furnace Gradient Heating Furnace (GHF) onboard "Kibo" is used for the growth of an In_xGa_1-xSb bulk crystal which is a potential substrate material of optoelectronic devices such as thermo-photo-voltaic cells and gas sensors, since the band gap and the lattice constant of the crystals are tuned by adjusting the composition. The current status of the space experiment project will be reported in the presentation.

To study the supercooling of many liquid metals with high melting temperatures, the investigation was performed for the cooling curves of electrostatic levitation (ESL) experiments, which had been originally obtained for the measurements of many physical properties. The largest supercooling over the literature values was found for liquid Ru (428 K), Ta (721 K), W (601 K), and Ir (438 K), where temperatures in the parentheses mean the supercooling of respective liquid metals. This indicates the validity of ESL for the supercooling experiments of liquid metals and alloys because of being rather free from the heterogeneous nucleation. This ESL was applied to the study of supercooling of homogeneous liquid phase in the composition range from 29 at% Nb to 71 at% Nb of eutectic Ni-Nb system, whose eutectic point is present at 40.5 at% Nb and 1448 K. The experimental result shows a poor supercooling tendency of homogeneous liquid phase around the eutectic composition in spite of large supercooling far apart from this eutectic composition. This characteristic feature was discussed based on the classical nucleation theory coupled with the knowledge recently found, the existence of concentration fluctuations in the homogeneous liquid phase near the eutectic point.

Ice crystal growth experiments in heavy water were carried out under microgravity to investigate the morphological transition from a disk crystal to a dendrite. Surprisingly, however, no transition was observed, namely, the disk crystal or dendrite maintained its shape throughout the experiments, unlike the results obtained on the ground. Therefore, we introduce a growth model to understand disk growth. The Gibbs-Thomson effect is taken into account as a stabilization mechanism. The model is numerically solved by varying both an interfacial tension of the prism plane and supercooling so that the final sizes of the crystals can become almost the same to determine the interfacial tension. The results are compared with the typical experimental ones and thus the interfacial tension is estimated to be 20 mJ/m2. Next, the model is solved under two supercooling conditions by using the estimated interfacial tension to understand stable growth. Comparisons between the numerical and experimental results show that our model explains well the microgravity experiments. It is also found that the experimental setup has the capability of controlling temperature on the order of 1/100 K. © 2011 American Physical Society.

Ice crystal growth experiments in heavy water were carried out under microgravity to investigate the morphological transition from a disk crystal to a dendrite. Surprisingly, however, no transition was observed, namely, the disk crystal or dendrite maintained its shape throughout the experiments, unlike the results obtained on the ground. Therefore, we introduce a growth model to understand disk growth. The Gibbs-Thomson effect is taken into account as a stabilization mechanism. The model is numerically solved by varying both an interfacial tension of the prism plane and supercooling so that the final sizes of the crystals can become almost the same to determine the interfacial tension. The results are compared with the typical experimental ones and thus the interfacial tension is estimated to be 20 mJ/m(2). Next, the model is solved under two supercooling conditions by using the estimated interfacial tension to understand stable growth. Comparisons between the numerical and experimental results show that our model explains well the microgravity experiments. It is also found that the experimental setup has the capability of controlling temperature on the order of 1/100 K.

Thermophysical properties of high temperature melts are important to better understand material processes such as casting, welding, and crystal growth. Containerless processing techniques combined with non-contact diagnostic methods play significant roles in thermophysical property measurements of high temperature melts because these methods can circumvent problems which arise from a reaction between container and melts. The electrostatic levitation method can measure density, surface tension, and viscosity of high temperature materials. Most of refractory metals including tungsten have been melted and their thermophysical data have been taken with this method. This paper briefly explains the technique and discusses the future measurements using microgravity environment in space. (C) 2011 The Japan Society of Applied Physics

Electrostatic levitation combined with laser heating is becoming a mature technique that has been used for several fundamental and applied studies in fluid and materials sciences (synthesis, property determination, solidification studies, atomic dynamic studies, etc.). This is attributable to the numerous processing conditions (containerless, wide heating temperature range, cooling rates, atmospheric compositions, etc.) that levitation and radiative heating offer, as well as to the variety of diagnostics tools that can be used. In this paper, we describe the facility, highlighting the combined advantages of electrostatic levitation and laser processing. The various capabilities of the facility are discussed and are exemplified with the measurements of the density of selected iron-nickel alloys taken over the liquid phase. Copyright © 2011 Paul-François Paradis et al.

To study the supercooling of many liquid metals with high melting temperatures the investigation was performed for the cooling curves of electrostatic levitation (ESL) experiments which had been originally obtained for the measurements of many physical properties The largest supercooling over the literature values was found for liquid Ru (428 K) Ta (721 K) W (601 K), and Ir (438 K) where temperatures in the parentheses mean the supercooling of respective liquid metals This indicates the validity of ESL for the supercooling experiments of liquid metals and alloys because of being rather free from the heterogeneous nucleation This ESL was applied to the study of supercooling of homogeneous liquid phase in the composition range from 29 at% Nb to 71 at% Nb of eutectic Ni-Nb system. whose eutectic point is present at 40 5 at% Nb and 1448 K The experimental result shows a poor supercooling tendency of homogeneous liquid phase around the eutectic composition in spite of large supercooling far apart from this eutectic composition This characteristic feature was discussed based on the classical nucleation theory coupled with the knowledge recently found the existence of concentration fluctuations in the homogeneous liquid phase near the eutectic point [doi 10 2320/matertrans MAW201025]

Surface tension and viscosity of molten vanadium were measured over a wide temperature range by the oscillating drop method in an electrostatic levitation furnace. Over the (2023 to 2517) K temperature range, the surface tension can be expressed as gamma(T)/(10(-3) N/m) = 1935 - 0.27 {(T - T(m))/K} with T(m) = 2183 K. Over the same temperature span, the viscosity can be expressed as eta(T)/(10(-3) Pa . s) = 1.23exp[2.27 . 10(4)/(RTK(-1))], where R is the gas constant. (c) 2010 Elsevier Ltd. All rights reserved.

Viscosity of liquid boron was measured over the temperature range from 2325 to 2556 K using an electrostatic levitation method combined with an oscillation drop technique. The results obtained revealed that the viscosity increases slowly with decreasing temperature from 2.2 mPa s at 2550 K to 2.6 mPa s at 2370 K, and substantially increases with further decrease in temperature below the melting temperature (T(m) = 2360 K), becoming as large as 6.4 mPa s at 2325 K. The increase in the viscosity suggests that clusters with extension may appear in supercooled liquid of boron.

The structural relaxation in a Zr55Cu30Ni5Al10 bulk metallic glass was investigated by volume and enthalpy relaxation at various temperatures. The relaxation kinetics was well described by a stretched exponential relaxation function, Phi(t) = exp[-(t/tau)(beta)]. The Kohlrausch index, beta, ranged from 0.35 to 0.69, while the temperature dependence of relaxation time, tau was best fitted by the Vogel-Fulcher-Tanmmann formula, tau(T) = tau(0) exp [D* T-0/(T - T-0)], with tau(0) = 1.1 x 10(-14) s, D* = 44.2 and T-0 = 311 K. Atomic volumes in the equilibrium liquid region were measured by the electrostatic levitation method and these volumes, together with volumes of relaxed glasses, were better described by the Cohen-Grest model than by the Cohen-Turnbull model. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Thermophysical properties of liquid gadolinium were measured using non-contact diagnostic techniques with an electrostatic levitator. Over the 1585 K to 1920 K temperature range, the density can be expressed as ρ (T) = 7.41 × 10 3 - 0.46(T - T m)(kg m -3) where T m = 1585 K, yielding a volume expansion coefficient of 6.2 × 10 -5 K -1. In addition, the surface tension data can be fitted as γ(T) = 8.22 × 10 2 - 0.097(T - T m) (10 -3 N m -1) over the 1613K to 1803K span and the viscosity as ρ (T) = 1.7exp[1.4 × 10 4/(RT)](10 -3 Pa s) over the same temperature range. © Springer Science+Business Media, LLC 2010.

The knowledge of thermophysical properties of active metals is critical to understand their metallurgical processes and further industrial applications. However, due to high reactivity and melt contamination from a crucible and gaseous environment, accurate values of the properties are hard to obtain using conventional methods such as the sessile-drop method. In the present Study, a vacuum electrostatic levitator was used to circumvent these difficulties and enabled the noncontact determination of thermophysical properties of liquid cerium even in an undercooled state. The data of density, surface tension, and viscosity of molten cerium were reported, as well as their temperature dependence.

We examined the Volume and viscosity of Zr-Cu-Al glass-forming liquid alloys to clarify the origin of a frozen free volume in glassy alloys. Since an excess free volume imparts toughness and ductility to glassy alloys, we attempted to increase this volume in glass structures so that they could be used as engineering materials. The maximum frozen excess free volume was observed in the ternary eutectic composition of the Zr-Cu-Al alloy system; however, its origin remains unclear. We attempted to reveal the mechanism of the formation of the frozen excess free volume in Zr-Cu-Al glassy alloys. (C) 2008 Elsevier B.V. All rights reserved.