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Session Chairman: Y. A. Chang, Department of Materials Science & Engineering, University of Wisconsin, Madison, WI 53706-1595
OPENING REMARK: Y.A. Chang, Department of Materials Science & Engineering, University of Wisconsin, Madison, WI 53706-1595
2:05 pm KEYNOTE
CONSTITUTION AND THERMODYNAMICS OF MONOTECTIC ALLOYS: Prof. Dr. B. Predel, Max-Planck-Institut für Metallforschung, Inst. für Werkstoffwissenschaft, Seestrabe 92, D-70174 Stuttgart, Germany
Many binary systems exhibit miscibility gaps in the liquid state. It is well known that melts which are passing a miscibility gap on cooling, solidify to a regular consisting of two layers. Such metallic solid bodies are not interesting for technical applications and have also scarcely been investigated scientifically. Genuine interest in demixing systems only arised as it seemed possible to prevent layer formation under zero gravity. However, experiments in space have shown that even under migro-g conditions, phase separation is occurring, yet in another way as on earth and also not finely dispersed. Afterwards, there resulted an intensive disclosure of the thermodynamics and the kinetics of the separation of liquid immiscible phases. After the discussion of the results obtained it is indicated how layer formation can be prevented and a finely dispersed structure can be realized in order to enable technical use.
2:50 pm INVITED
ENTHALPY OF FORMATION OF LIQUID [TRANSITION METAL-sp METAL] BINARY ALLOYS: M. Gaune-Escard, J.P. Bros, IUSTI-UMR 129, Université de Provence, Centre de St-Jérôme, 13397 Marseille, France
With a fully automated high temperature calorimeter (Tmax = 1800K) and using the direct drop method, the molar integral of formation of the binary liquid alloys (Ga and In with Fe, Co, Ni, Rh, Pd, Ir, and Pt) have been measured with an accuracy of about 6%. From these results the molar partial enthalpies have been calculated and the transfer of electrons from the sp-metal to the transition metal has been deduced. Moreover some liquidus points of the equilibrium phase diagram of these systems have been obtained.
3:25 pm BREAK
3:40 pm INVITED
HIGH-TEMPERATURE THERMOCHEMISTRY OF INTERMETALLIC COMPOUNDS OF TRANSITION METALS AND RARE EARTH METALS WITH TiN: S.V. Meschel, O.J. Kleppa, James Franck Institute, University of Chicago, Chicago, IL 60637
A wide range of intermetallic compounds of transition metals and rare earth metals with tin have been studied by direct synthesis calorimetry at 1473 ± 2K. The results provide a picture of the systematic dependence of the standard enthalpy of formation of the compounds on the number of 3d-, 4d- and 5d-electrons in the considered transition metals, and on the number of f-electrons in the lanthanide metals. The results will be compared with earlier experimental data, where available, and with predictions from the semi-empirical model of Miedema and co-workers.
4:20 pm INVITED
APPLICATIONS OF EMF MEASUREMENTS IN THERMODYNAMIC STUDIES: A. Mikula, Institut für Anorganische Chemie, Universität Wien, Vienna, Austria
The use of emf measurements for the determination of thermodynamic properties of materials is reviewed. The development of a new galvanic cell techniques will be presented and their advantages and disadvantages in their application for certain problems will be discussed. There is a wide field for new applications of this technique like fuel cells, production of hydrogen, developments of new batteries, control of production processes and developments of new sensors. Scientific applications include kinetic measurements and studies of thermodynamic properties. This work will concentrate on the use of emf measurements of the thermodynamics of phase and reaction equilibria.
4:55 pm INVITED
HEAT CAPACITY OF LIQUID ALLOYS: F. Sommer, Max-Planck-Institut für Metallforschung, Institut für Werkstoffwissenschaft, Seestr. 75, D-70174 Stuttgart, Germany
Some specific features of the temperature and concentration dependence of the heat capacity Cp of ordering or segregating liquid alloys will be discussed. Some recent experimental Cp-data (e.g. Al-La-Ni, Bi-Ga, Al-In) obtained using a new adiabatic calorimeter are presented. The ability of some models to describe the different characteristics of the Cp(T,x)-course of liquid alloys is demonstrated. A direct connection between the thermodynamic properties of liquid alloys and the atomic transport properties like diffusion and viscosity will be described.
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