Measurement of thermophysical properties of lead by a submicrosecond pulse-heating method in the range 2000–5000 K

A submicrosecond ohmic pulse-heating technique with heating rates of more than 10⁹K· s^–1 allows the determination of such thermophysical properties as heat capacity and the mutual dependences among enthalpy, electrical resistivity, temperature, and volume up to superheated liquid states for lead. Also, an estimation of the critical point data is given from investigations at elevated static pressures.Paper presented at the First Workshop on Subsecond Thermophysics, June 20–21, 1988, Gaithersburg, Maryland, U.S.A.     

Thermophysical measurements on solid and liquid rhenium

A fast resistive heating technique was used to measure such thermophysical data of solid and liquid rhenium as enthalpy, specific heat, thermal volume expansion, and electrical resistivity. The measurements are performed with heating rates of slightly more than 10⁹ K · s ^–1 up to states of superheated liquid rhenium (7500 K).Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Combined DSC and Pulse-Heating Measurements of Electrical Resistivity and Enthalpy of Tungsten,Niobium, and Titanium

Measurements of thermophysical properties such as enthalpy, electrical resistivity, and specific heat capacity as a function of temperature starting from the solid state into the liquid phase for W, Nb, and Ti are presented in this work. An ohmic pulse-heating technique allows measurements of enthalpy and electrical resistivity from room temperature to the end of the stable liquid phase within 60 μ s. The simultaneous optical measurement of temperature is limited by the fast pyrometers with an onset temperature of T_min = 1200–1500 K; below these temperatures, the fast pyrometers are not sensitive. A differential scanning calorimeter (DSC) is used for determination of the specific heat capacity, and also to obtain enthalpy values in the temperature range of 600–1700 K. Combining the two methods entends the range of values of electrical resistivity and enthalpy versus temperature down to 600 K. Results on the metals W, Nb, and Ti are reported and compared to literature values. This paper is a continuation of earlier work. Paper presented at the Seventh International Workshop on Subsecond Thermophysics, October 6–8, 2004, Orléans, France.     

Thermophysical Properties of Five Binary Copper–Nickel Alloys

Thermophysical properties (e.g., specific enthalpy, heat of fusion, electrical resistivity, thermal volume expansion) are measured in the liquid phase up to very high temperatures by an extreme fast pulse-heating method. Heating rates of about 10⁸ K · s^?1 are applied by self-heating of wire-shaped metallic specimens with a current of approximately 10,000 A. Pure elements seem to be still close to thermal equilibrium as the obtained results are in good agreement with those obtained by static methods. However, this situation might be different for alloys. The rapid volume heating can shift diffusion-controlled phase transitions at heating to higher temperatures or even make them not noticeable anymore. The simple binary Cu–Ni system was chosen to test the heating rate dependence; this system is well known and shows complete miscibility in the liquid and solid ranges of interest. This study is a further step to test the performance of the fast pulse-heating method being applied to simple and more complex alloys. Measured results of enthalpy, heat of fusion, heat capacity, and electrical resistivity in the vicinity of the melting range are presented. The results of enthalpy and heat capacity agree with simple mixing rules. The measured electrical resistivity of different compositions is compared to results obtained by electromagnetic levitation measurements.     

A microsecond-resolution transient technique for measuring the heat of fusion of metals: Niobium

A microsecond-resolution pulse-heating technique is described for the measurement of the heat of fusion of refractory metals. The method is based on rapid resistive self-heating of the specimen by a high-current pulse from a capacitor discharge system and measurement of the current through the specimen, the voltage across the specimen, and the radiance temperature of the specimen as a function of time. Melting of the specimen is manifested by a plateau in the temperature versus time function. The time integral of the power absorbed by the specimen during melting yields the heat of fusion. Measurements gave a value of 31.1 kj · mol^–1 for the heat of fusion of niobium, with an estimated maximum uncertainty of ±5%. Electrical resistivity of solid and liquid niobium at its melting temperature was also measured.     

Investigation of the Heating Dynamics and Properties of Liquid Tungsten

The dynamics of electrical explosion of tungsten wires under water in microsecond times was studied. A new optical method for temperature measurement has been developed. For tungsten, uniform heating took place at 10¹¹<j(A·m^–2)<10¹², therefore one can use these regimes for the investigation of properties in the liquid phase. Temperature dependences of enthalpy, electrical resistivity, and specific heat for liquid tungsten are given and compared with literature values.     

Measurement of the enthalpy and specific heat of a Be2C-graphite-UC2 reactor fuel material to 1980 K

The enthalpy and specific heat of a Be₂C-Graphite-UC₂ composite nuclear fuel material have been measured over the temperature range 298–1980 K using both differential scanning calorimetry and liquid argon vaporization calorimetry. The fuel material measured was developed at Sandia National Laboratories for use in pulsed test reactors. The material is a hot-pressed composite consisting of 40 vol% Be₂C, 49.5 vol% graphite, 3.5 vol% UC₂, and 7.0 vol% void. The specific heat was measured with the differential scanning calorimeter over the temperature range 298–950 K, while the enthalpy was measured over the range 1185–1980 K with the liquid argon vaporization calorimeter. The normal spectral emittance at a wavelength of 6.5×10^–5 cm was also measured over the experimental temperature range. The combined experimental enthalpy data were fit using a spline routine and differentiated to give the specific heat. Comparison of the measured specific heat of the composite to the specific heat calculated by summing the contributions of the individual components indicates that the specific heat of the Be₂C component differs significantly from literature values and is approximately 0.56 cal · g^–1 · K ^–1 (2.3×10³J · kg^–1 · K ^–1) for temperatures above 1000 K.     

Measurement of the heat of fusion of tungsten by a microsecond-resolution transient technique

A microsecond-resolution pulse-heating technique was used for the measurement of the heat of fusion of tungsten. The method is based on rapid (100 to 125s) resistive self-heating of a specimen by a high-current pulse from a capacitor discharge system and measuring current through the specimen and voltage across the specimen as functions of time. Melting of a specimen is manifested by changes in the slope of the electrical resistance versus time function. The time integral of the power absorbed by a specimen during melting yields the heat of fusion. Measurements gave a value of 48.7 kJ · mol^–1 for the heat of fusion of tungsten with an estimated maximum uncertainty of ±6%. The electrical resistivity of solid and liquid tungsten at its melting temperature was also measured.Paper presented at the Third Workshop on Subsecond Thermophysics, September 17–18, 1992, Graz, Austria.     

A submicrosecond pulse heating system for the investigation of thermophysical properties of metals at high temperatures

A submicrosecond ohmic pulse heating technique is described for measurements of thermal properties of cylindrical metallic samples at high temperatures. Electrical and optical measurements for determination of thermophysical data such as enthalpy, specific heat, and electrical resistivity are presented. Effects that can falsify the results are discussed.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Measurement of the heat capacity of molybdenum (Standard Reference Material) in the range 1500–2800 K

Measurement of the heat capacity of molybdenum (Standard Reference Material 781 of the National Bureau of Standards) in the temperature range 1500–2800 K by a subsecond-duration, pulse-heating technique is described. The results of the measurements on three specimens are in agreement within 0.6%. The heat capacity of molybdenum in the temperature range 1500–2800 K based on the present results is expressed by the following function (standard deviation =0.5%): C _p =–3.0429+4.7215×10^–2 T–2.3139×10^–5 T ²+4.7090× 10^–9 T ³ where T is in K and C _p is in J · mol^–1 · K^–1. The inaccuracy of the reported results is estimated to be not more than 3%.     

The thermodynamic similarity of nitrogen,oxygen, and air

The thermodynamic similarity of nitrogen, oxygen, and air is established. The data for nitrogen are used to calculate the thermodynamic properties of oxygen at pressures of (1–1500)·10⁵ N/m² and temperatures of 170–1000 deg K. Tables of specific volume, enthalpy, entropy, and heat capacity of oxygen are given.     

Thermodynamic properties by levitation calorimetry — V. High-temperature heat content of liquid gallium

The heat content (enthalpy) of liquid gallium relative to the supercooled liquid state at 298.15 K has been measured by levitation calorimetry over the temperature range 1412–1630 K. Thermal energy increments were determined using an aluminum block calorimeter of conventional design. The sharp decrease of C _p with increasing temperature observed just above the melting point does not persist up to the high temperatures of the present work. When combined with recent laser-flash calorimetry results from the literature, the present work indicates that C _p is 26.46 ± 0.71 J · g-atom^–1 · K^–1 over the temperature range 587–1630 K.Paper presented at the Japan-United States Joint Seminar on Thermophysical Properties, October 24–26, 1983, Tokyo, Japan.     

Measurement of the heat of fusion of molybdenum by a microsecond-resolution transient technique

A microsecond-resolution pulse-heating technique was used for the measurement of heat of fusion of molybdenum. The method is based on rapid resistive self-heating of the specimen by a high-current pulse from a capacitor discharge system and measuring current through the specimen, voltage across the specimen, and radiance temperature of the specimen as functions of time. Melting of the specimen is manifested by a plateau in the temperature versus time function. The time integral of the power absorbed by the specimen during melting yields the heat of fusion. Measurements gave a value of 36.4 kJ · mol^–1 for the heat of fusion of molybdenum with an estimated maximum uncertainty of±6%.Paper presented at the First Workshop on Subsecond Thermophysics, June 20–21, 1988, Gaithersburg, Maryland, U.S.A.Formerly National Bureau of Standards     

Measurement of the heat of fusion of tantalum by a microsecond-resolution transient technique

The heat of fusion of tantalum was measured using a microsecond-resolution pulse-heating technique. The technique is based on rapid (about 100-s) resistive self-heating of a specimen by a high-current pulse from a capacitor discharge system and measuring the current through the specimen, voltage across the specimen, and radiance temperature of the specimen as functions of time. Melting of a specimen is manifested by a plateau in the radiance temperature versus time function. The time integral of the power absorbed by the specimen during melting yields the heat of fusion. Measurements gave a value of 34.8 kJ · mot^– for the heat of fusion of tantalum, with a total uncertainty of ±6%. Electrical resistivity of solid and liquid tantalum at its melting temperature was also measured.     

Thermophysical properties of solid and liquid tungsten

The thermophysical properties of solid and liquid tungsten have been measured up to an enthalpy ofH = 1.4 MJ · kg^–1 using an isobaric expansion technique. These measurements give the pressure, temperature, volume, enthalpy, electrical resistivity, and sound velocity as fundamental quantities. From these, other properties may be calculated, such as specific heat at constant volume and pressure, heat of fusion, isothermal and adiabatic bulk moduli and compressibilities, and thermodynamic. Results of these calculations are presented for liquid tungsten and compared with literature values where such data exist. These data will help in understanding liquid-metal phenomenology theoretically and in the design and modeling of exploding wires, foils, and fuses.Paper presented at the First Workshop on Subsecond Thermophysics, June 20–21, 1988, Gaithersburg, Maryland, U.S.A.     

Experimental investigation of vacancy effects in pure metals

The energy for the formation of vacancies in copper (2.1 · 10^–19 J (1.3 eV)), platinum (2.56 · 10^–19 J (1.6 eV)), and titanium (1.9 · 10^–19 J (1.2 eV)) are determined from the results of measurements of the enthalpy and heat capacity of the latter in deformed and annealed states.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 6, pp. 1013–1017, December, 1980.     

Measurement of thermophysical properties by a pulse-heating method: Thoriated tungsten in the range 1200 to 3600 K

Thoriated tungsten (tungsten, 98%: thorium oxide. 2 % ) is a widely used electrode material for inert-gas arc-welding. Data for the heat capacity, electrical resistivity. and hemispherical total emissivity of this material are reported for the temperature range 1200–3600 K. A subsecond pulse-heating technique was applied to rod specimens: radiance temperature was measured by high-speed pyrometry. Literature values of the temperature dependence of the normal spectral emissivity of tungsten were used to obtain true temperatures, using the melting point of thoriated tungsten as a calibration point. Reported uncertainties for the properties are 4 % for heat capacity, 1.5 % for electrical resistivity, and 7 % for hemispherical total emissivity.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Thermophysical Properties of the Zr–0.01Nb Alloy at Various Heating Rates and Repeated Cycles of Heating–Cooling

The results of an experimental study of the heat capacity, enthalpy, electrical resistivity, and spectral emissivity (for the wavelength of 0.65 m) of the Zr–0.01Nb alloy in the temperature range from 900 to 2000 K are presented. The study was carried out using subsecond pulse heating of the samples by passing electrical current through them. Experiments were conducted at different heating rates (10³ to 10⁴K·s^–1), and a series of experiments consisted of several cycles of pulse heating and subsequent cooling. The effect of these parameters on the temperature dependence of thermophysical properties in the region of the –transition was studied. With an increase in the heating rate, the temperature of the – transition, and the maximum in the heat capacity shifted to higher temperatures. There are significant differences in properties over the temperature range of the – transition for the various heating cycles.     

Measurement of the heat of fusion of titanium and a titanium alloy (90Ti-6Al-4V) by a microsecond-resolution transient technique

A microsecond-resolution pulse heating technique was used for the measurement of the heat of fusion of titanium and a titanium alloy (90Ti-6Al-4V). The method is based on rapid (50- to 100-s) resistive self-heating of the specimen by a high-current pulse from a capacitor discharge system and measuring, as functions of time, current through the specimen, voltage across the specimen, and radiance of the specimen. Melting of the specimen is manifested by a plateau in the measured radiance. The time integral of the net power absorbed by the specimen during melting yields the heat of fusion. The values obtained for heat of fusion were 272 J · g^–1 (13.0 kJ · mol^–1) for titanium and 286 J · g^–1 for the alloy 90Ti-6Al-4V, with an estimated maximum uncertainty of ±6% in each value.Paper presented at the Second Workshop on Subsecond Thermophysics, September 20–21, 1990, Torino, Italy.     

Enthalpy and Temperature of the Titanium Alpha-Beta Phase Transformation

The specific enthalpy and the temperature of the titanium - phase transformation were measured by a pulse-heating system operating in the millisecond time regime. The measurement technique is based on self-heating of a tube-shaped specimen from room temperature to the beta phase of titanium. A comparison between the measured phase transition temperature during heating and cooling of the specimen shows a difference of approximately 20 K. The temperature measured during the heating period is higher than the value obtained from the cooling cycle of the specimen. For the evaluation of the specific enthalpy of the alpha-beta transformation, the specific enthalpy versus temperature function of the beta phase of the heating period was extrapolated to the transition temperature obtained from the cooling cycle (1152 K). A total of 12 measurements on 3 tube-shaped specimens was made, an average value of 89.9 kJkg^–1 was obtained for the specific enthalpy of the transformation. The reproducibility of the measured specific enthalpy at the beginning and at the end of the transformation was 0.5%. The reproducibility of the phase transformation enthalpy as difference between the beginning and the end was 3%. The extended measurement uncertainty (at a confidence level of 95%) is estimated to be ±6% for the specific enthalpy of the transformation and ±6 K for the transformation temperature.