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Accepted: 2018-12-01, 資料番号: SA1180327000

著者人数: 15名, Accepted: 2020-02-11, 資料番号: SA1190184000

This review briefl y 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.

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.

Accepted: 2010-02-07, 資料番号: SA1000813000

To understand the nature and behavior of rare earth metals in their liquid phases, accurate values of their physical properties are essential. However, to measure their physical properties, the samples should be maintained in liquid phases for prolonged time, and this raises a formidable challenge. This is mainly explained by their high melting temperatures (e.g., 1629 K for Tb), high vapor pressure, and the risk of melt contamination with a crucible or support. An electrostatic levitation furnace alleviated these difficulties and allowed the determination of density, surface tension, and viscosity of several metals above their melting temperature. Here, first, the levitation furnace facility and the noncontact diagnostic procedures were briefly discussed, followed by the explanation of their thermophysical property measurements over wide temperature ranges. The density was obtained using an ultraviolet-based imaging technique that allowed excellent illumination, even at elevated temperatures. Over the 1615 to 1880 K temperature span, the density measurements could be expressed as p ( T ) = 7.84 × 10 3 - 0.47 ( T - T m ) (kg · m −3 ) with T m = 1629 K, yielding a volume expansion coefficient α( T ) = 6.0 x 10 −5 (K −1 ). In addition, the surface tension and the viscosity could be determined by inducing a drop oscillation to a molten sample. Using this technique, the surface tension data could be expressed as σ( T ) = 8.93 x 10 2 - 0.10 ( T - T m )(mN · m −1 ) and those for viscosity as η( T ) = 0.583 exp [4.1 x 10 4 /( RT )] (MPa · s) over the 1690 to 1980 K temperature range.

Accepted: 2006-02-23, 資料番号: SA1000066000

Accepted: 2003-02-07, 資料番号: SA1002374000

Some thermophysical properties of liquid and supercooled palladium were measured using containerless techniques. Over the 1640–1875 K temperature interval, the density could be expressed as ρ(T)=10.66× 103 −0.77(T−Tm)(kg·m−3) and the ratio between the isobaric heat capacity and the hemispherical total emissivity could be rendered as (J·mol−1·K−1), where T m =1828 K. The volume expansion coefficient was also determined as 7.2 × 10−5 K−1.

Accepted: 2003-02-12, 資料番号: SA1002373000

Accepted: 2003-02-05, 資料番号: SA1002371000

Four thermophysical properties of both solid and liquid vanadium: the density, thermal expansion coefficient, molar heat capacity at constant pressure, and hemispherical total emissivity, are reported. These thermophysical properties were measured over a wide temperature range, including the undercooled state, with an electrostatic levitation furnace developed by the National Space Development Agency of Japan. Over the (l840–2240) K temperature range, the density of the liquid can be expressed as ρ(T)/( kg m −3 )=5.46·10 3 −0.49·(T−T fus )/ K with T fus =2183 K, yielding a volume expansion coefficient of the liquid α(T)=8.9·10 −5 K −1 . Similarly, over the (1700–2180) K temperature range, the density of the solid can be expressed as ρ(T)/( kg m −3 )=5.72·10 3 −0.52·(T−T fus )/ K , giving a volume expansion coefficient of the solid α(T)=9.1·10 −5 K −1 . The molar heat capacity at constant pressure of the liquid phase can be estimated as C p, m (T)/( J K −1 mol −1 )=48.78+2.75·10 −3 ( T − T fus )/K over the (l825–2225) K temperature range if the hemispherical total emissivity of the liquid phase remains constant at 0.32 over the temperature interval. Over the (1350–2180) K temperature span, the hemispherical total emissivity of the solid phase can be expressed as e T ( T )=0.38–2.52·10 −4 ·( T /K)+9.90·10 −8 ·( T 2 /K 2 ). The enthalpy of fusion has also been measured as 26.5 kJ mol −1 .

This paper describes a novel levitation furnace for the containerless structural study of superheated and undercooled materials by neutron scattering experiments. The article discusses the concept behind this electrostatic levitator and presents preliminary levitation and positioning control data of superheated and undercooled metallic samples. The paper also highlights the advantages of this facility, in particular vacuum conditions, sample position stability, long duration levitation times, and open field of view of the molten sample. Potential modifications of the apparatus for atomic structure and dynamic studies of dielectric oxides glass forming materials are also briefly addressed.

From 1997, the National Space Development Agency of Japan (NASDA) metastable research team has studied containerless materials processing to establish undercooled and nucleation processing techniques for oxides and high-melting-temperature metals as a preparation for flying the electrostatic levitation furnace on the International Space Station. This crucible-less facility allows samples to be deeply undercooled while avoiding nucleation on the sample surface. It allows not only precise measurements of the thermophysical properties of molten sample, but also permits material processing from the undercooled state. Of the four levitation techniques (acoustic, electromagnetic, electrostatic, aerodynamic), NASDA has concentrated on the development of an electrostatic levitation system, both for use in the ISS and for fundamental research on the ground. A promising containerless experiment of a ceramic oxide using the electrostatic containerless furnace under the microgravity condition offered by a sounding rocket (TR-IA No. 7) was also carried out in 1998 and is addressed in this paper. A novel aerodynamic levitation system was developed to adopt the drop tube which gave smooth cooling curves for molten Y 3 Al 5 O 12 (YAG) sample.

著者人数: 15名, 資料番号: SA1150061000

This article describes a hybrid electrostatic–aerodynamic levitation furnace for the containerless processing and study of oxide materials on the ground. Its operation principle relies on an aerodynamic levitator that allows sufficient electric charge to be accumulated on a sample, due to high-temperature heating, before electrostatic levitation can be effective. The article discusses the concept of this new levitator and presents the proof of the technical feasibility of electrostatically levitating and melting oxide material samples (BiFeO3, 49.5CaO–50.5Al2O3 mol %) in a pressurized atmosphere. In addition, superheating–undercooling cycles can be performed while maintaining an exceptional sample positioning stability along the three directions. Moreover, we report the first vitrification of dielectric oxide material samples (49.5CaO–50.5Al2O3 mol %) using an electrostatic levitation method. The article also discusses the advantages of this facility compared with other existing instruments for the contai...

Two new methods that substantially ease the processing and study of refractory metals, when an electrostatic levitation furnace is used, are reported. The first technique is concerned with preheating the sample on a pedestal, prior to launch, to a temperature (∼1500 K) at which thermionic emission dominates all other charging/discharging mechanisms that may be going on simultaneously. Launched into levitation at that temperature, the sample can be quickly heated to its molten state without encountering further charge loss problems. This procedure thus shortens substantially the time it takes to bring the samples to their final high temperature states at which their thermophysical properties can be measured. This technique can be applied to most materials whose melting temperatures are higher than their thermionic temperatures. The second technique described is an ultraviolet-based sample imaging configuration. Due to the excellent sample–background contrast it continuously provides during all phases of pr...

Accepted: 2004-10-19, 資料番号: SA1002380000

Oxygen-deficient h-BaTiO3 synthesized by noncontact processing exhibits a dielectric constant higher than 100 000 with a loss component of about 0.1 together with a weak temperature dependence in the range of 100 to 300 K. Dielectric constant dramatically dropped by 2 orders of magnitude below 70 K.

The density of neodymium-doped calcium aluminate (

Electrostatic levitation together with multibeam heating and ultraviolet imaging overcame contamination, imaging, and sample position stability problems associated with handling of liquid tantalum and rhenium. Here, the density [ρ(T)] of these metals is reported in the superheated and undercooled states. Over the 2760–3580 K interval, the density of tantalum was measured as ρ(T)=1.50×104−0.41(T−Tm) kg m−3, where the melting temperature Tm, was 3290 K. For rhenium, the density was determined (2700–3810 K) as ρ(T)=1.84×104−0.91(T−Tm), with Tm=3453 K. From these data, respective volume expansion coefficients of 2.7×10−5 and 4.9×10−5 K−1 were calculated. At Tm, the data agree well with the literature values.

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??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.

Accepted: 2011-06-30, 資料番号: SA1003078000

Accepted: 2014-09-24, 資料番号: SA1140204000

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.

Accepted: 2002-02-18, 資料番号: SA1002362000

Accepted: 2003-12-15, 資料番号: SA1002365000