Thermophysical Property Measurements of Supercooled and Liquid Rhodium

The density, the isobaric heat capacity, the surface tension, and the viscosity of liquid rhodium were measured over wide temperature ranges, including the supercooled phase, using an electrostatic levitation furnace. Over the 1820 to 2250 K temperature span, the density can be expressed as (T)=10.82×10³–0.76(T–T _m ) (kgm^–3) with T _m =2236 K, yielding a volume expansion coefficient (T)=7.0×10^–5 (K^–1). The isobaric heat capacity can be estimated as C _P (T)=32.2+1.4×10^–3(T–T _m ) (Jmol^–1K^–1) if the hemispherical total emissivity of the liquid remains constant at 0.18 over the 1820 to 2250 K interval. The enthalpy and entropy of fusion have also been measured, respectively, as 23.0 kJmol^–1 and 10.3 Jmol^–1K^–1. In addition, the surface tension can be expressed as (T)=1.94×10³–0.30(T–T _m ) (mNm^–1) and the viscosity as (T)=0.09 exp[6.4×10⁴(RT)] (mPas) over the 1860 to 2380 K temperature range.     

Thermophysical Property Measurements of Liquid Gadolinium by Containerless Methods

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 × 10³ − 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 × 10² − 0.097(T − T _m)(10⁻³ N · m⁻¹) over the 1613 K to 1803 K span and the viscosity as η(T) = 1.7exp[1.4 × 10⁴/(RT)](10⁻³ Pa · s) over the same temperature range.     

Thermophysical Properties of Containerless Liquid Iron up to 2500 K

Thermophysical properties of high temperature liquid iron heated with a CO₂ laser have been determined in an aerodynamic levitation device equipped with a high-speed camera and a three-wavelength pyrometer. Characteristic curves of the free cooling and heating of the drop can be used to determine the same apparent emissivity of solid and liquid iron and to calibrate pyrometers based on the known value of the melting point of iron, i.e., 1808 K. Examination of the recalescence of undercooled liquid iron and further solidification are used to obtain the ratio of the melting enthalpy versus the heat capacity of liquid iron as . The surface tension was determined from an analysis of the vibrations of liquid drops. Results are accurately described by (mJm^–2)=(1888±31)–(0.285±0.015) (T–T _m ) between 1750 K (undercooled liquid) and 2500 K. The density of liquid iron has been deduced from the image size and the mass of the liquid iron drops.     

Containerless Property Measurements of Liquid Palladium

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 (T)=10.66× 10³ –0.77(T–T_m)(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.     

静电悬浮条件下的材料典型热物理性质测量

随着对材料研究的逐渐深入,材料制备和材料分析的方法越来越重要,并且一些材料重要的物理性质是开展相关研究的基础。由于一些材料熔点高、难熔化,同时,传统手段无法避免容器壁的污染,或者无法在真空条件下进行试验避免气体的污染,或者由于实验性质原因只能测量特定的材料,这些方法很难测量材料在高温下过热过冷阶段的热物理性质。系统介绍了静电悬浮技术,这是一种新型的实现深过冷的方式,可以达到高温下对材料热物理性质进行测量的目的。静电悬浮技术使样品在两极板间悬浮,在悬浮的状态下采用激光对样品进行加热,使材料达到高温熔化,同时进行热物性的测量。对比了几种实现测量典型热物理性质的方法,了解静电悬浮的优势,并详细地介绍了静电悬浮技术对材料的熔体密度、热膨胀系数、表面张力和粘度系数以及比热的测量。     

Containerless Processing in Space—Thermophysical Property Measurements Using Electromagnetic Levitation

Electromagnetic levitation is a novel tool for measuring thermophysical properties of high-temperature metallic melts. Contamination by a crucible is avoided, and undercooling becomes possible. By exploiting the microgravity environment of an orbiting spacecraft, the positioning fields can be further reduced and undesired side effects of these fields can be minimized. After two successful Spacelab flights of the electromagnetic levitation facility TEMPUS, an advanced electromagnetic levitation facility is presently being studied for accommodation on the International Space Station, ISS. Due to the permanent nature of the ISS, an operational concept must be defined which allows the exchange of consumables without exchanging the entire facilty. This is accomplished by a modular design, which is presented. For all experiments, like measurement of specific heat, of surface tension and viscosity, of thermal expansion, and of electrical conductivity, noncontact diagnostic tools must be either improved or developed. Such tools are, for example, pyrometry, videography (high-speed and high-resolution), and inductive measurements. This paper summarizes the scientific results obtained so far and deduces some lessons learned that will be incorporated into the new design and will lead to both new results and a higher precision of the data.     

Non-Contact Measurements of the Thermophysical Properties of Hafnium-3 Mass% Zirconium at High Temperature

Several thermophysical properties of hafnium-3 mass % zirconium, namely the density, the thermal expansion coefficient, the constant pressure heat capacity, the hemispherical total emissivity, the surface tension and the viscosity are reported. These properties were measured over wide temperature ranges, including overheated and undercooled states, using an electrostatic levitation furnace developed by the National Space Development Agency of Japan. Over the 2220 to 2875 K temperature span, the density of the liquid can be expressed as _L (T)=1.20×10⁴–0.44(T–T _m ) (kgm^–3) with T _m =2504 K, yielding a volume expansion coefficient _L (T)=3.7×10^–5 (K^–1). Similarly, over the 1950 to 2500 K span, the density of the high temperature and undercooled solid -phase can be fitted as _S (T)=1.22×10⁴–0.41(T–T _m ), giving a volume expansion coefficient _S (T)=3.4×10^–5. The constant pressure heat capacity of the liquid phase can be estimated as C _PL (T)=33.47+7.92×10^–4(T–T _m ) (Jmol^–1K^–1) if the hemispherical total emissivity of the liquid phase remains constant at 0.25 over the 2250 K to 2650 K temperature interval. Over the 1850 to 2500 K temperature span, the hemispherical total emissivity of the solid -phase can be represented as _TS (T)=0.32+4.79×10^–5(T–T _m ). The latent heat of fusion has also been measured as 15.1 kJmol^–1. In addition, the surface tension can be expressed as (T)=1.614×10³–0.100(T–T _m ) (mNm^–1) and the viscosity as h(T)=0.495 exp [48.65×10³/(RT)] (mPas) over the 2220 to 2675 K temperature range.     

Thermophysical Properties of Undercooled Liquid Cu–Ni Alloys

Experimental data for the surface tension, density, and electrical resistivity of undercooled liquid Cu–Ni alloys of different compositions and at different temperatures are presented. The experiments were performed in facilities that combine the containerless positioning method of electromagnetic levitation with contactless measurement techniques. Although Cu–Ni alloys are rather simple from a chemical point of view, the data for density, surface tension, and electrical resistivity unveil the occurrence of short-range atomic order processes in the melt. For the density this manifests in a composition-dependent excess volume, for the surface tension in smaller values due to an increased surface segregation, and for the electrical resistivity in a deviation from the linear temperature dependence at low temperatures.     

Thermophysical Properties of Stable and Supercooled Liquid Carbon

Measurement Techniques - Temperature dependences of the isobaric heat capacity of stable and supercooled liquid carbon, which were obtained by processing thermograms of spontaneous cooling of...     

Thermophysical Property Measurements in Microgravity: Chances and Challenges

The microgravity environment offers considerable advantages for the measurement of thermophysical properties, in particular, for high-temperature metallic melts. The absence of containers and of convection are the two major benefits. This paper reviews past microgravity experiments dealing with thermophysical property measurements and discusses the methods used. An outlook into the space station era is also given with special emphasis on chances and challenges.     

Measurements of thermophysical properties of liquid metals by noncontact techniques

With the advent of containerless processing techniques such as electromagnetic levitation, it is now possible to study the properties of high-temperature liquid metalsin situ by applying sophisticated noncontact diagnostics, such as pyrometry and high-speed videography. Thermophysical properties of interest are, e.g., specific heat, thermal conductivity, and viscosity. Applying containerless processing, it is also possible to undercool the melt because of the lack of container-induced nucleation sites. This gives access to a metastable region of the phase diagram. The knowledge of thermophysical data in this region is very important, because undercooling plays a major role in any solidification process. The degree of undercooling not only determines the growth velocity, but also is crucial in selecting the eventually obtained metastable solid phase. In this paper, some recent developments are surveyed relating to the noncontact measurements of emissivity, specific heat, electrical conductivity, density, surface tension, and viscosity, as well as a discussion of possible experiments in microgravity.Paper presented at the Third Workshop on Subsecond Thermophysics, September 17–18, 1992, Graz, Austria.     

Thermophysical Properties of Undercooled Liquid Co80Pd20

The surface tension, viscosity, and electrical resistivity of liquid Co₈₀Pd₂₀were measured containerlessly for temperatures above and, especially, below the melting point. The first two quantities were measured with the help of the oscillating drop technique, the last one by an inductive method. The experiments have been performed under low gravity in the electromagnetic levitation facility TEMPUS during the MSL-1 Spacelab mission. This environment allowed us to measure for the first time the viscosity and electrical resistivity in the deeply undercooled state, where the Co₈₀Pd₂₀melt shows a magnetic ordering behavior. In this paper the measurement methods and results are presented.     

Thermophysical Property Measurements on Mold Materials: Thermal Expansion and Density

In order to optimize casting processes, computational models of solidification have proven to be very valuable to foundrymen. It is experimentally proven that the casting defects are primarily related to mold properties. During the eutectic growth the temperature rises, which is commonly referred to as recalescence. This has a strong effect on the mold walls, and mold wall movement can occur. The huge pressures generated at this time can block voids if mold is rigid. In green sand molds the moisture content will be reduced and mold wall will expand easily. According to previous research results, a distribution of thermophysical properties of the mold in the mold cavity, and the movement (expansion or contraction) of the mold and the metal interface are crucial for formation of many defects. The thermal expansion and bulk density of selected mold materials (olivine sand and zircon sand) and silica sand cores in transient regimes were determined in this study using a computer-controlled dual-pushrod dilatometer.Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22--27, 2003, Boulder, Colorado, U.S.A.     

Uncertainty Analysis of Thermophysical Property Measurements of Solids Using Dynamic Methods

This work reports on an analysis of thermophysical properties (thermal conductivity, thermal diffusivity, and specific heat capacity) measurements of solids using dynamic methods. The influence of temperature measurement uncertainty on the parameter estimation uncertainty is studied using a least-squares procedure. The standard and difference analyses are used for optimizing the experiment with respect to the data window or time interval of measurements. The analysis is applied to the extended dynamic plane source method, and the results of numerical computations are illustrated in the form of contour plots.     

Thermophysical Properties of 1,1,1,3,3-Pentafluorobutane (R365mfc)

This paper presents an experimental study on various thermophysical properties of a new fluoroalkane, 1,1,1,3,3-pentafluorobutane (R365mfc). The thermal conductivity of R365mfc was measured in the liquid phase near saturation conditions at temperatures between 263 and 333 K using a parallel plate instrument with an uncertainty of less than ±5%. For the measurement of the saturated liquid density between 273 and 353 K, a vibrating tube instrument was used. The uncertainty of the density measurements is less than ±0.1%. In addition, experimental data have been obtained for R365mfc under saturation conditions over a wide temperature range from about 253 to 460 K using light scattering techniques. Light scattering from the bulk fluid has been applied for measuring both the thermal diffusivity and the sound speed in the liquid and vapor phases. Light scattering by surface waves on a horizontal liquid–vapor interface has been used for the simultaneous determination of the surface tension and kinematic viscosity of the liquid phase. With the light scattering techniques, uncertainties of less than ±1.0, ±0.5, ±1.0, and ±1.2% have been achieved for the thermal diffusivity, the sound speed, the kinematic viscosity, and the surface tension, respectively.     

Surface Tension Measurements of Liquid Metals by the Quasi-Containerless Pendant Drop Method

The surface tensions of liquid metals, Zr, Ni, Ti, Mo, and Nb, have been measured at their melting points using the quasi-containerless pendant drop method. This method involves melting the end of a high-purity metal rod by bombardment with an electron beam to form a pendant drop under ultrahigh-vacuum conditions to minimize surface contamination. The magnified image of the drop is captured from a high-resolution CCD camera and digitized using a frame-grabber. The digital image is analyzed by reading the pixel intensities from a graphics file. The edge coordinates of the drop along rows and columns of pixels are searched by a computer program and stored in an array. An optimized theoretical drop shape is computed from the edge coordinates by solving the Young–Laplace differential equation to deduce the surface tension. The measured surface tensions are compared with available experimental results and theoretical calculations.     

Thermophysical properties of liquids at high pressures

Most of the thermophysical properties of fluids are greatly altered at high pressures, and the studies of these changes are of much scientific and technological importance. In this paper, the effects of temperature and pressure on the density, viscosity, and thermal conductivity of various liquids are described briefly, based on recent experimental results from the author's laboratory. The objectives of this investigation, methods of measurements, and some of the experimental results are reviewed, as well as the present aspects in this field. Several important problems to be interpreted are also pointed out from the present measurements.Presented at the Japan-United States Joint Seminar on Thermophysical Properties, October 24–26, 1983, Tokyo, Japan.