Search

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, Tg, 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. [ABSTRACT FROM AUTHOR]

Understanding the liquid structure provides information that is crucial to uncovering the nature of the glass-liquid transition. We apply an aerodynamic levitation technique and high-energy X-rays to liquid (l)-Er2O3 to discover its structure. The sample densities are measured by electrostatic levitation at the International Space Station. Liquid Er2O3 displays a very sharp diffraction peak (principal peak). Applying a combined reverse Monte Carlo – molecular dynamics approach, the simulations produce an Er–O coordination number of 6.1, which is comparable to that of another nonglass-forming liquid, l-ZrO2. The atomic structure of l-Er2O3 comprises distorted OEr4 tetraclusters in nearly linear arrangements, as manifested by a prominent peak observed at ~180° in the Er–O–Er bond angle distribution. This structural feature gives rise to long periodicity corresponding to the sharp principal peak in the X-ray diffraction data. A persistent homology analysis suggests that l-Er2O3 is homologically similar to the crystalline phase. Moreover, electronic structure calculations show that l-Er2O3 has a modest band gap of 0.6 eV that is significantly reduced from the crystalline phase due to the tetracluster distortions. The estimated viscosity is very low above the melting point for l-ZrO2, and the material can be described as an extremely fragile liquid. Liquid structure at extremely high temperature: levitation and quantum beam provide insights Experiments on the International Space Station (ISS) and SPring-8 have revealed properties and structure of liquid at the atomic level. X-ray diffraction provides detailed knowledge of the atomic structure of crystalline materials, but the technique is not so useful for liquids. Experiments on liquids are difficult because of the high temperatures often needed to create the liquid. To circumvent the problem, Chihiro Koyama from the Japan Aerospace Exploration Agency, Shinji Kohara from the National Institute for Materials Science, and co-workers performed density and high-energy X-ray diffraction measurements on levitating liquid erbium oxides in an electrostatic levitation furnace on the ISS and an aerodynamic levitation furnace at SPring-8, respectively. By combining the experimental data with computer simulations, the team were able to model the liquid's structure and properties at both the atomic and electronic levels. The structure of a high-temperature non-glass forming liquid Er2O3 was investigated by a combination of density measurements in the International Space Station and synchrotron X-ray diffraction measurements utilizing levitation techniques with the aid of computational and advanced mathematical analyses. These multidisciplinary approaches revealed that unusually sharp diffraction peak in the liquid is originated from the formation of distorted tetraclusters whose homology is similar to that of the crystalline phase. [ABSTRACT FROM AUTHOR]

The phase relation between supercooled liquid silicon (l-Si) and amorphous silicon (a-Si) is discussed based on experimental results. Electrostatically levitated l-Si samples were supercooled down to low temperatures, 300 K below the melting temperature (Tcl: 1683 K), and solidified accompanied by the release of latent heat. It was found that solidified Si samples melted again at 1480 K caused by the latent heat. Also, it was found that the Si samples that rapidly quenched near the solidification temperature contained a large amount of a-Si with tetrahedral coordination. These two findings show that the supercooled l-Si samples solidified into a-Si and a-Si melted, confirming the idea of a first-order phase transition between two metastable phases proposed by Turnbull et al. [Metall. Mater. Trans. A 29, 1825 (1998)]. [ABSTRACT FROM AUTHOR]

Understanding the liquid structure provides information that is crucial to uncovering the nature of the glass-liquid transition. We apply an aerodynamic levitation technique and high-energy X-rays to liquid (l)-Er2O3 to discover its structure. The sample densities are measured by electrostatic levitation at the International Space Station. Liquid Er2O3 displays a very sharp diffraction peak (principal peak). Applying a combined reverse Monte Carlo – molecular dynamics approach, the simulations produce an Er–O coordination number of 6.1, which is comparable to that of another nonglass-forming liquid, l-ZrO2. The atomic structure of l-Er2O3 comprises distorted OEr4 tetraclusters in nearly linear arrangements, as manifested by a prominent peak observed at ~180° in the Er–O–Er bond angle distribution. This structural feature gives rise to long periodicity corresponding to the sharp principal peak in the X-ray diffraction data. A persistent homology analysis suggests that l-Er2O3 is homologically similar to the crystalline phase. Moreover, electronic structure calculations show that l-Er2O3 has a modest band gap of 0.6 eV that is significantly reduced from the crystalline phase due to the tetracluster distortions. The estimated viscosity is very low above the melting point for l-ZrO2, and the material can be described as an extremely fragile liquid.Liquid structure at extremely high temperature: levitation and quantum beam provide insights Experiments on the International Space Station (ISS) and SPring-8 have revealed properties and structure of liquid at the atomic level. X-ray diffraction provides detailed knowledge of the atomic structure of crystalline materials, but the technique is not so useful for liquids. Experiments on liquids are difficult because of the high temperatures often needed to create the liquid. To circumvent the problem, Chihiro Koyama from the Japan Aerospace Exploration Agency, Shinji Kohara from the National Institute for Materials Science, and co-workers performed density and high-energy X-ray diffraction measurements on levitating liquid erbium oxides in an electrostatic levitation furnace on the ISS and an aerodynamic levitation furnace at SPring-8, respectively. By combining the experimental data with computer simulations, the team were able to model the liquid’s structure and properties at both the atomic and electronic levels.The structure of a high-temperature non-glass forming liquid Er2O3 was investigated by a combination of density measurements in the International Space Station and synchrotron X-ray diffraction measurements utilizing levitation techniques with the aid of computational and advanced mathematical analyses. These multidisciplinary approaches revealed that unusually sharp diffraction peak in the liquid is originated from the formation of distorted tetraclusters whose homology is similar to that of the crystalline phase. [ABSTRACT FROM AUTHOR]

The thermoelectric properties of quaternary icosahedral AlPdReFe quasicrystals obtained by replacing Re with Fe in icosahedral AlPdRe quasicrystals have been studied according to the guiding principle of weakly bonded rigid heavy clusters (WBRHCs). Anisotropy in the microstructures of arc-melted and annealed samples was found, and the electrical and thermal conductivities are larger in the direction perpendicular to the bottom of the arc-melted button than in the parallel case. The dimensionless figure of merit (ZT) in the perpendicular direction was increased 2.6 times from 0.08 to 0.21 by Fe substitution for Re in the icosahedral AlPdRe quasicrystals, which was caused by the increase of the Seebeck coefficient and the decrease of the phonon thermal conductivity, and the increase of the electrical conductivity, expected and not for the WBRHCs, respectively. [ABSTRACT FROM AUTHOR]

With the advent of third-generation synchrotron sources and the development of light source techniques, X-ray scattering techniques have become feasible, leading to new approaches for studying the structures of disordered materials in a quantitative manner. We introduce a dedicated diffractometer for high-energy total X-ray scattering measurement and a newly developed anomalous X-ray spectrometer at SPring-8. As advanced methodologies for the measurement of liquids, we now offer three state-of-art levitation instruments for aerodynamic levitation, electrostatic levitation, and acoustic levitation at the SPring-8 beamlines, covering a wide temperature range of −40-3000 ℃. Furthermore, scientific investigations of glasses, liquids, and amorphous materials reported in the last five years at SPring-8 are reviewed. [ABSTRACT FROM AUTHOR]

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 μm 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 [ABSTRACT FROM AUTHOR]

Atomic motions and, especially, correlations in atomic motion over angstrom length scales are a sensitive probe of material properties: phonons in single crystals respond to the detailed interactions between atoms, including both short- and long-range forces, and screening thereof, while the atomic dynamics of liquids is intimately connected with nearly all aspects of liquid behavior. Scientific questions associated with measuring dynamics include the detailed nature of phase transitions, correlations of atomic motions with electronic or magnetic properties (superconductivity, ferro-electric behavior, magnetoelastic coupling, etc.), and also very practical issues, such as investigating elasticity. Not surprisingly, both from the point of view of basic science and for applications such as geology, there is strong desire to extend studies of atomic dynamics throughout material phase diagrams, into extreme conditions. [ABSTRACT FROM AUTHOR]

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 sessiledrop 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. [ABSTRACT FROM AUTHOR]

A compact electrostatic levitator was developed for the structural analysis of high-temperature liquids by x-ray diffraction methods. The size of the levitator was 200 mm in diameter and 200 mm in height and can be set up on a two axis diffractometer with a laboratory x-ray source, which is very convenient in performing structural measurements of high-temperature liquids. In particular, since the laboratory x-ray source allows a great amount of user time, preliminary or challenging experiments can be performed with trial and error, which prepares and complements synchrotron x-ray experiments. The present small apparatus also provides the advantage of portability and facility of setting. To demonstrate the capability of this electrostatic levitator, the static structure factors of alumina and silicon samples in their liquid phases were successfully measured. [ABSTRACT FROM AUTHOR]

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 O2, air and N2 at a chamber pressure of 4 × 105 Pa. The measurements under these different atmospheres suggested that the density increased when decreasing the oxygen atmosphere. The density obtained under N2, air and O2 gas atmosphere can be expressed as ρ(T) N2 = 2.91 × 103 − 0.073(T − Tm), ρ(T) air = 2.76 × 103 − 0.075(T − Tm) and ρ(T) O2 = 2.70 × 103 − 0.1(T − Tm) (kg m−3) (±2%) with Tm = 1878 K, over the range 2200 to 673 K. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]