Zinn und Antimon in Legierungen

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A new program for DSC purity analysis

DSC purity determinations have become very popular today [3]. The latest edition of the Mettler software package for thermal analysis, TA72.S GraphWare, now comprises a powerful purity evaluation program. It is based on the simultaneous calculation of the mole ratio of the sum of the eutectic impurities, the melting point of the pure component, the melting point of the substance present and the linearization term. The portion of the melting curve investigated is selected appropriately.Experience has shown, that the applied heating rate is a very important parameter which influences the duration of the measurement and also the possible exposure to elevated temperature where decomposition can become a problem and last but not least the accuracy of the calculated impurity value.

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Zusammenfassung Die DSC-Reinheitsbestimmung ist heute eine weit verbreitete Methode, die mit einer einzigen Messung und unter Verwendung geeigneter Auswerteprogramme eine Bestimmung der absoluten eutektischen Reinheit einer Probe zulÄsst. Gleichzeitig können weitere thermodynamische Daten bestimmt werden, wie Schmelzpunkt der Probensubstanz und der reinen Hauptkomponente und die Schmelzenthalpie der Probe.Durch experimentelle Befunde konnte gezeigt werden, dass die Wahl der Aufheizrate kritisch ist in bezug auf die Genauigkeit und die Signifikanz der ermittelten Daten.

     

CEMS and DCEMS investigations of Al-implanted iron

-Fe surfaces were implanted with a nominal dose of 5×10¹⁷ Al ions/cm² at 50 keV and a current density of about 3.7 A/cm². Samples of different shapes and thicknesses have been used in order to test the influence of heat flow from specimen to target holder during implantation. Integral and energy differential (depth-selective)⁵⁷Fe conversion electron Mössbauer spectroscopy (CEMS and DCEMS) were employed. The spectra indicated a magnetic phase characterised by a broad hyperfine field distributionP(B _hf), a non-magnetic phase, and -Fe. The relative intensity of the non-magnetic phase was enhanced if the thermal contact during implantation became worse. An energy dependence of DCEM spectra in the L-electron range was observed. Model calculations using L-electron weight functions and experimental concentration profiles obtained by secondary neutral mass spectroscopy (SNMS) yielded fair agreement between calculated and experimental phase signals. The results demonstrate that the non-magnetic Fe-Al alloy phase with high Al concentration is located closer to the surface than the magnetic alloy phase, which extends to much larger depth than expected.     

Charge effects during surface analysis of poorly conducting inorganic materials

Summary The properties of surfaces and interfaces often determine the behaviour of materials in a given application: typical examples are all kinds of corrosion, segregation, sensor activity, wear and friction, adhesion of coatings, joining processes, sintering, etc. It is the aim of this paper to provide materials scientists with a better understanding of the limits of applying modern surface analysis methods (SIMS, AES, etc.) to materials with low room temperature electrical conductivity like most ceramics and glasses. One feature common to all methods deserves special attention: this is the influence of surface and near surface charges on the distribution of mobile ionic species in the near surface region of the sample to be analyzed. The origin of these charges and their order of magnitude as a function of the experimental parameters can be deduced from charge balance considerations: the main result is that self-compensating methods should be most favorable.     

Lanthanide transport in stabilized zirconias: interrelation between ionic radius and diffusion coefficient

The diffusion of all stable lanthanides was measured both in calcia stabilized zirconia (CSZ) and in yttria stabilized zirconia (YSZ) in the temperature range between 1,286 and 1,600 degrees C. The lanthanide diffusion coefficients obtained increase with increasing ionic radius. The experimental activation enthalpy of diffusion is near 6 eV for CSZ and between 4 and 5 eV for YSZ and is not strongly affected by the type of lanthanide. The results were correlated with defect energy calculations of the lanthanide diffusion enthalpy using the Mott-Littleton approach. An association enthalpy of cation vacancies with oxygen vacancies of about 1 eV (96 kJ/mol) was deduced in the case of CSZ, while there is no association in the case of YSZ. Furthermore, the change in diffusion coefficients can be correlated to the interaction parameter for the interaction between the lanthanide oxide with zirconia: The higher the interaction parameter, the higher the lanthanide diffusion coefficient.     

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