Thermodynamic properties of aluminum

This work reviews and discusses the data on the thermodynamic properties of aluminum available through May 1984. However, two papers dated 1985 which are useful to this work are also included. These properties include heat capacity, enthalpy, enthalpy of transition and melting, vapor pressure, and enthalpy of vaporization. The recommended values for heat capacity cover the temperature range from 0.1 to 2800 K. The recommended values for enthalpy, entropy, Gibbs energy function, and vapor pressure cover the temperature range from 298.15 to 2800 K.     

Thermodynamic properties of nickel

This work reviews and discusses the data and information on the thermodynamic properties of nickel available through May 1984. These properties include heat capacity, enthalpy, enthalpy of transition and melting, vapor pressure, and enthalpy of vaporization. The recommended values for heat capacity cover the temperature range from 1 to 3200 K. The recommended values for enthalpy, entropy, Gibbs energy function, and vapor pressure cover the temperature range from 298.15 to 3200 K.     

Thermodynamic properties of titanium

This work reviews and discusses the data and information on the thermodynamic properties of titanium available through May 1984. These properties include heat capacity, enthalpy, enthalpy of transition and melting, vapor pressure, and enthalpy of vaporization. The recommended values for heat capacity cover the temperature range from 1 to 3800 K. The recommended values for enthalpy, entropy, Gibbs energy function, and vapor pressure cover the temperature range from 298.15 to 3800 K.     

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.     

The melting point,latent heat of solidification,and enthalpy for both solid and liquid α-Al2O3 in the range 550–2400 K

In this paper the authors describe the use of a high-temperature drop calorimeter with autoadiabatic control for the measurment of the enthalpy of -Al₂O₃ in the temperature range 550 to 2400 K for both solid and liquid phases. Equations representing the enthalpy of both solid and liquid states are obtained from the data with the use of a computer. In addition to the melting point, T _m=2328±7 K, the latent heat of solidification, L=1137.90 J · g^–1, has also been determined. The results of the present work are compared with those reported in the literature.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Thermodynamic Properties and Decomposition of Lithium Hexafluoroarsenate, LiAsF6

The heat capacity of lithium hexafluoroarsenate is determined in the temperature range 50–750 K by adiabatic and differential scanning calorimetry techniques. The thermodynamic properties of LiAsF₆ under standard conditions are evaluated: C _p ⁰(298.15 K) = 162.5 ± 0.3 J/(K mol), S ⁰(298.15 K) = 173.4 ± 0.4 J/(K mol), ⁰(298.15 K) = 81.69 ± 0.20 J/(K mol), and H ⁰(298.15 K) – H ⁰(0) = 27340 ± 60 J/mol. The C _p(T) curve is found to contain a lambda-type anomaly with a peak at 535.0 ± 0.5 K, which is due to the structural transformation from the low-temperature, rhombohedral phase to the high-temperature, cubic phase. The enthalpy and entropy of this transformation are 5.29 ± 0.27 kJ/mol and 10.30 ± 0.53 J/(K mol), respectively. The thermal decomposition of LiAsF₆ is studied. It is found that LiAsF₆ decomposes in the range 715–820 K. The heat of decomposition, determined in the range 765–820 K using a sealed crucible and equal to the internal energy change U _r(T), is 31.64 ± 0.08 kJ/mol.     

Combined DSC and Pulse-Heating Measurements of Electrical Resistivity and Enthalpy of Platinum,Iron, and Nickel

Measurements of the enthalpy, electrical resistivity, and specific heat capacity as a function of temperature starting from the solid state up into the liquid phase for Fe, Ni, and Pt are presented. Two different measurement approaches have been used within this work: an ohmic pulse-heating technique, which allows – among others – the measurement of enthalpy, specific heat capacity, and electrical resistivity up to the end of the stable liquid phase, and a differential–scanning–calorimetry technique (DSC) which enables determination of specific heat capacity from near room temperature up to 1500 K. The microsecond ohmic pulse-heating technique uses heating rates up to 10⁸ K·s^–1 and thus is a dynamic measurement, whereas the differential–scanning–calorimetry technique uses heating rates of typically 20 K·min^–1 and can be considered as a quasi-static process. Despite the different heating rates both methods give good agreement of the thermophysical data within the stated uncertainties of each experiment. Results on the metals Fe, Ni, and Pt are reported. The enthalpy and resistivity data are presented as a function of temperature and compared to literature values.     

Thermal Property Measurements and Enthalpy Calculation of the Lithium Bromide+Lithium Iodide+1,3-Propanediol+Water System

The lithium bromide+lithium iodide+1,3-propanediol+water [LiBr/LiI mole ratio=4 and (LiBr+LiI)/HO(CH₂)₃ OH mass ratio=4] solution is being considered as a potential working fluid for an absorption chiller. Heat capacities at four temperatures, 283.15, 298.15, 313.15, and 333.15 K, were measured in the range from 50 to 70 mass%. In addition, the differential heats of dilution at 298.15 K were measured in the range from 45.3 to 71.8 mass%. Each individual data set was correlated with a proper regression equation with a high accuracy. A new enthalpy calculation method for the working fluids containing organics was proposed. The calculation method correlated the heat capacity (at various temperatures and concentrations) and the differential heat of dilution (at ambient temperature and various concentrations). The present method was applied for the construction of enthalpy–concentration (H–T–X) diagrams with high confidence.     

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.     

Thermodynamic Properties of Some Methylphosphonyl Dihalides From 15 to 335 °K

Measurements of the heat capacity of methylphosphonyl difluoride (CH₃POF₂), methyl phosphonyl dichloride (CH₃POCl₂), and methylphosphonyl chlorofluoride (CH₃POClF) were made from about 15 to 335 °K by means of an adiabatic calorimeter. These highly reactive and toxic substances were purified in a completely closed glass apparatus by combining slow crystallization and fractional melting procedures. The purities determined by the freezing-curve method are shown to be generally in agreement with those values obtained by the calorimetric method. From the results of the heat measurements, the triple-point temperature, heat of fusion, and their corresponding estimated uncertainties were found to be, respectively, 236.34±0.05 °K and 11,878±12 J/mole for CH₃POF₂, 306.14± 0.02 °K and 18,076±15 J/mole for CH₃POCl₂, and 250.70± 0.20 °K and 11,853±30 J/mole for CH₃POClF. Triple-point temperatures obtained by the freezing-curve method are in agreement with the above values. A table of smoothed values of heat capacity, enthalpy, enthalpy function, entropy, Gibbs free energy, and Gibbs free energy function from 0 to 335 °K was obtained from the data. The entropy and its corresponding estimated uncertainty for CH3POF2, CH3POCl2, and CH3POClF in their respective condensed phase at 298.15 °K and saturation pressure was found to be 208.3± 0.3, 164.8± 0.3, and 216.4± 0.4 J/deg mole, respectively. The entropies in the gaseous state at 298.15 °K and 1 atm pressure were found to be 312.7±3, 339.7±3, and 335.0±3 J/deg mole, respectively.     

Low-Temperature Heat Capacity and Thermodynamic Functions of AlH3 and AlD3

The thermodynamic properties of AlH₃ and AlD₃ were evaluated from low-temperature heat capacity measurements. For -AlH₃, C ⁰ _p (298.15 K) = 41.14 ± 0.13 J/(mol K), S ⁰(298.15 K) = 30.62 ± 0.14 J/(mol K), H ⁰(298.15 K) – H ⁰(0) = 5527 ± 15 J/mol, and ⁰(298.15 K) = 12.08 ± 0.06 J/(mol K). For -AlD₃, C ⁰ _p (298.15 K) = 50.82 ± 0.04 J/(mol K), S ⁰(298.15 K) = 36.74 ± 0.12 J/(mol K), H ⁰(298.15 K) – H ⁰(0) = 6801 ± 10 J/mol, and ⁰(298.15 K) = 13.93 ± 0.04 J/(mol K).     

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.     

Experimental Investigation of the Heat Capacity and Enthalpy of 12Kh18N9T and 12Kh18N10T (Chrome–Nickel–Titanium) Austenitic Steels in the Temperature Range from 300 to 1678 K

The results of experimental investigation of the enthalpy and of the true and mean heat capacity of 12Kh18N9T and 12Kh18N10T (chrome–nickel–titanium) austenitic stainless steels are given. The heat capacity is measured with an error of 1% in the temperature range from 300 to 900 K by the method of continuous adiabatic heating. The enthalpy and mean heat capacity are investigated by the method of mixtures in the temperature range from 1200 to 1678 K with an error of 1%. The experimental results are approximated by an unified equation for the temperature range from 298.15 to 1678 K using the least-squares method. The errors of calculated data are estimated.     

A thermodynamic property formulation for nitrogen from the freezing line to 2000 K at pressures to 1000 MPa

A new fundamental equation explicit in Helmholtz energy for thermodynamic properties of nitrogen from the freezing line to 2000 K at pressures to 1000 MPa is presented. A new vapor pressure equation and equations for the saturated liquid and vapor densities as functions of temperature are also included. The techniques used for development of the fundamental equation are those reported in a companion paper for ethylene. The fundamental equation and the derivative functions for calculating internal energy, enthalpy, entropy, isochoric heat capacity (C _v), isobaric heat capacity (C _p), and velocity of sound are also included in that paper. The property formulation using the fundamental equation reported here may generally be used to calculate pressures and densities with an uncertainty of ±0.1%, heat capacities within ± 2%, and velocity of sound values within ±2%. The fundamental equation is not intended for use near the critical point.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

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.     

A unified model for the cohesive enthalpy, critical temperature, surface tension and volume thermal expansion coefficient of liquid metals of bcc, fcc and hcp crystals

First the cohesive enthalpy of pure liquid metals is modeled, based on experimental critical temperatures of alkali metals. The cohesive enthalpies are scaled to the melting points of pure metals. The temperature coefficient of cohesive enthalpy is the heat capacity of the liquid metal. The surface tension and its temperature coefficient for pure liquid metals are modeled through the excess surface enthalpy, excess surface entropy and molar surface area supposing that the outer two surface layers of liquid metals are similar to the {1 1 1} plane of fcc crystals. The volumetric thermal expansion coefficient of liquid metals is scaled to the ratio of the heat capacity and cohesion enthalpy. From known values of melting point, heat capacity and molar volume the following calculated properties of liquid metals are tabulated: (i) cohesive enthalpy at melting point, (ii) cohesive energy of the solid metal at 0 K, (iii) critical temperature, (iv) surface tension at melting point, (v) volume thermal expansion coefficient, and (vi) temperature coefficient of surface tension. The present models are valid only for liquid metals of bcc, fcc or hcp crystals as only their structure and nature of bonding are similar enough to be treated together.     

Measurement of thermophysical properties by a pulse-heating method: Niobium in the range 1000–2500 K

Data for the heat capacity, electrical resistivity, hemispherical total emittance, and normal spectral emittance (at 898 nm) of niobium are reported for the temperature range 1000–2500 K. Measurements were based on a subsecond pulseheating technique. The results are discussed and compared with the literature values. Reported uncertainties for the properties are 3% for heat capacity, 1% for electrical resistivity, 5% for hemispherical total emittance, and 4% for normal spectral emittance.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Calorimetric Study of Rubidium Hexafluoroarsenate at Elevated Temperatures

The heat capacity of rubidium hexafluoroarsenate, RbAsF₆, was measured from 300 to 700 K by differential scanning calorimetry. The results indicate that the structural transformation from the rhombohedral to the cubic phase occurs in the range 305–436 K through an intermediate stable phase and reaches isothermal completion in a narrow temperature range of 407–409 K. The enthalpy of the transformation is 10.90 ± 0.03 kJ/mol, and its entropy is 26.39 ± 0.08 J/(K mol) = Rln24, which suggests that this structural transition is of the order–disorder type. The heat capacity data are used to evaluate the thermodynamic properties of RbAsF₆ in the range 300–700 K.     

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.     

New enthalpy increment flow calorimeter and measurements on a mixture of 68% methane and 32% propane

A new flow calorimeter for measuring isobaric enthalphy increment and Joule-Thomson effect was built and tested during the period 1987–1993. The calorimeter has several features that reduce the heat leakage better than previous designs; this includes thermal shields cooled by propane. a heat sink, and superinsulation on all piping. The temperature and pressure range covered by the calorimeter is 133 to 343 K and 0.17 to 14 MPa. Measurements on a mixture of 68.32% methane and 31.68% propane are presented. The enthalpy increment measurements have an average standard uncertainty of 0.08 kJ · kg^–1, or 0.22% of the enthalpy increment.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.