Over last decades numerous techniques of experimental thermodynamics in dependence on different aspects of phase diagram science and equilibria computation and prediction were applied. Some of them regard thermochemical measurements and thermodynamic equilibria measurements and they are able to estimate feature of phase diagrams or thermodynamic properties. Others involve methods enabling to characterise phases present in a system from the point of view of their structural feature, composition and phase abundance and also their morphology and physical chemical properties.
Both groups yield data which serve as input information for calculation of thermodynamic properties as well as of phase equilibria for various technically important systems.
Very typical technique is Knudsen effusion method. This method utilizes effusion of the gas being in equilibrium with sample (solid or liquid phase) through a small orifice.
This work presents data from Knudsen cell mass spectrometry coupled with differential scanning calorimetry. Instrument STA 409 CD / QMS 403/5 SKIMMER from firma Netzsch [1] applied for investigation of nickel based alloys as well as newly developed steels illustrates modern way how to collect source data leading to estimation of activities for particular components very trigly and effectively. Some data are compared with older ones obtained using home made equipment coupled with a monopole mass spectrometer [2]. Final data can be subsequently used for determination of thermodynamic properties using thermodynamic models involved in CALPHAD method [3].
Acknowledgement: MSM0021622410 and OC098.

[1] E. Kaisersberger, E. Post: Thermochim. Acta 324 (1998) 197.
[2] J. Vrestal and J. Tomiska: J. Non-Cryst. Solids 156-158 (1993) 429.
[3] N. Saunders, A. P. Miodovnik: 'CALPHAD, Pergamon Materials Series, Vol. 1, Elsevier Science, Amsterodam (1998).

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1. Activities of interstitial elements inside heat-resistant steels, filler alloys, and weld electrode materials