Alan Dinsdale

SGTE data for pure elements

Thermodynamic data for the condensed phases of 78 elements as currently used by SGTE (Scientific Group Thermodata Europe) are tabulated. SGTE is a consortium of seven organisations in Western Europe engaged in the compilation of a comprehensive, self consistent and authoritative thermochemical database for inorganic and metallurgical systems. The data are being published here in the hope that they will become widely adopted within the international community as a sound basis for the critical assessment of thermodynamic data, thereby, perhaps, limiting unnecessary duplication of effort. The data for each phase of each element considered aie presented as expressions showing, as a function of temperature, the variation of (a) G-HSER, the Gibbs energy relative to the enthalpy of the “Standard Element Reference” ie the reference phase for the element at 298.15 K and (b) the difference in Gibbs energy between each phase and this reference phase (ie lattice stability). The variation of the heat capacity of the various phases and the Gibbs energy difference between phases are also shown graphically. For certain elements the thermodynamic data have been assessed as a function of pressure as well as temperature. Where appropriate a temperature— pressure phase diagram is also shown. Throughout this paper the thermodynamic data are expressed in terms of J mol−1. The temperatures of transition between phases have been assessed to be consistent with the 1990 International Temperature Scale (ITS90).

MTDATA - thermodynamic and phase equilibrium software from the National Physical Laboratory

Abstract In the past, the complexity of the chemical and phase equilibria established during many industrial processes has prevented the kind of in-depth understanding of their thermodynamics necessary for successful and efficient process control. Predictive thermochemistry, as embodied within MTDATA, makes such an understanding possible. MTDATA allows equilibria to be calculated for multicomponent systems of practical interest, containing many different types of phase, from critically assessed data for their component binary and ternary subsystems. Very complicated calculations can be undertaken with as many as thirty different components and 500 phases being considered simultaneously. A number of modules are incorporated for critically assessing, manipulating and retrieving the data, making various types of calculation and plotting binary, ternary, multicomponent, and predominance area diagrams. Facilities are also available for users to link the complexities of phase equilibrium calculations within MTDATA to their own software or to third party commercial software packages enabling users to simulate unit operations within an industrial plant or to integrate kinetic effects. Special derivatives of MTDATA are also now being developed to provide the sophisticated capabilities within MTDATA to non-expert users for special applications using carefully designed graphical user interfaces, which are both easy to use, and which provide output specifically designed for the particular industrial need.

Metastable lattice stabilities for the elements

Abstract Lattice stabilities for the metastable FCC (Al), BCC (A2) and CPH (A3) allotropes of 43 elements have been evaluated. The results are based on (1) Assessed stable phase data; (2) Phase boundary extrapolations from binary alloy, and elemental pressure-temperature, phase diagrams; (3) A relationship between the entropy of fusion, crystal structure and melting point; (4) Stacking fault energies; (5) Periodic and group trends and (6) First principle electronic energy calculations. Qualitative trends proposed by previous thermochemical evaluations for the transition metals are to a large extent confirmed. However, the evaluated energy differences between the different crystal allotropes are substantially higher and can be closer in magnitude to those predicted by ab-initio electron energy calculations, although particular discrepancies, for example concerning Cr(FCC), still remain. Many of the changes proposed here arise from the reassessment of stable phase data, particularly with respect to recently measured heats of fusion of the high melting point elements.

The compound energy model for ionic solutions with applications to solid oxides

The application of the compound energy model to crystalline ionic phases is discussed and compared with the regular solution model. Its application to solutions with reciprocal reactions between cations on different sublattices is discussed with special reference to oxides. Examples are taken from various solutions between spinels, including cases with vacancies and interstitials. Problems connected with the choice of a state of reference for charged components in a multicomponent solution are addressed. This paper was presented at the International Phase Diagram Prediction Symposium sponsored by the ASM/MSD Thermodynamics and Phase Equilibria Committee at Materials Week, October21-23,1991, in Cincinnati, Ohio. The symposium was organized by John Morral, University of Connecticut, and Philip Nash, Illinois Institute of Technology.

The measurement of viscosity of alloys: a review of methods, data and models

Values of the viscosities of liquid metals are important in the prediction of fluid flow in many metallurgical manufacturing processes. This paper describes a number of methods used to measure the viscosity of liquid metals, including capillary, oscillating vessel, rotational bob or crucible, oscillating plate, draining vessel, levitation using the damping of surface oscillations and acoustic methods. A number of models used to estimate viscosity for elements, the temperature dependence of viscosity, and viscosity of multicomponent systems are also given, including the Andrade equation, Arrhenius equation, Hildebrands free volume theory, Chhabra models, Moelwyn-Hughes model and thermodynamic models. The scatter of data available in the literature are highlighted by comparing two reviews of data for elements.

The viscosity of aluminium and its alloys--A review of data and models

In this paper the available data for the measurement of viscosity of aluminium and its alloys are reviewed. Most measurements are performed with an oscillating vessel technique and the merits of this technique are discussed. The purity of the aluminium affects the measured viscosity values and we recommend a value of between 1.0–1.4 mPa·s for the pure element at the melting point. Although studies of the viscosity of aluminium alloys are limited, the effects of elemental additions to the alloy are similar to those for additions to the base metal. Thus an increase in concentration of Ti, Ni, Cr, Mn, Mg tends to increase the viscosity whereas the viscosity decreases with increasing Zn and Si concentrations. Also purification of an alloy decreases the viscosity. There is a wide variety of models ranging from those based on empiricism to thermodynamic methods. With the present quality of input data it is probably better to use a simple rather than a sophisticated model.

Thermodynamic and phase diagram data for the CaO-SiO2 system

Abstract A critical assessment of thermodynamic and phase diagram data for the CaO-SiO 2 system has been carried out using an extended Kapoor—Frohberg cellular model for the liquid phase. The assessment incorporates revised data for all the phases of the pure components expressed as the Gibbs energy relative to the weighted enthalpy of the elements in their standard reference states. The data for the intermediate compounds are expressed in the same form. The complete dataset therefore represents all the thermodynamic properties of all the phases as a function of temperature and composition.

Calculated phase equilibria for the CrFeNiSi system— I Ternary equilibria

Abstract A set of thermodynamic data for the calculation of phase equilibria for the OrPeNi rich portion of the CrFeNiSi system over the temperature range 650 to 1000 K has been provided. The equilibria are required to aid the interpretation of the structural behaviour of 18/8-type stainless steel fuel-cladding alloys during neutron irradiation. Themodynamic and phase diagram data for the stable phases in the CrSi, FeSi and NiSi systems have been critically assessed, and data for the unstable sigma phases in these and the CrNi and FeNi systems estimated. Provisional values for the lattice stabilities of the sigma form of the elements Cr, Fe, Ni and Si have also been provided. Isothermal sections for the CrFeNi system and the low silicon portions of the CrFeSi, CrNiSi and FeNiSi systems have been calculated for the temperature range 700 to 1173 K, and experimental phase diagram data for these systems critically assessed.

A Critical Assessment of Tnermodynamic and Phase Diagram Data for the Al-O System

A critical assessment of the thermodynamic and phase diagram data for the crystalline and liquid phases of the Ge-O system at ambient pressures has been carried out to provide a set of parameters which can be used as a basis for the calculation of ternary and multicomponent phase equilibria. The phase diagram reported by Massalski (Binary Alloy Phase Diagrams, ASM International, Materials Park, 1990) does not correctly reproduce the rather limited experimental information for the system. There is some inconsistency between the rather more extensive experimental thermodynamic data for the three phases of GeO2 stable at ambient pressures.

Predictive thermochemistry and phase equilibria of slags

It is well understood that the efficient recovery of values by pyrometallurgical processing of ores requires control of the slag chemistry. In an effort to improve the understanding of slags, a thermodynamic database on subsystems of the CaO-MgO-Fe-O-Al2O3-SiO2 system has been generated through critical assessment of the literature. Data for connecting systems of specific industrial interest are being added. The data can be combined using well-established thermodynamic principles to make calculations on the multicomponent systems of practical interest. Following a description of the calculations, this article illustrates specific applications of thermodynamic modeling to the extraction of copper, nickel, and precious metals; zinc extraction; purification of pig iron; meltdown in nuclear reactors; hot corrosion; and pollution control.