Thermodynamic analysis and phase equilibria investigation in Pb−Zn−Ag system
| Autor: | D Nada Strbac, T Dragana Zivkovic, M Aleksandra Mitovski, M Dusko Minic, M Dragan Manasijevic, T Ljubisa Balanovic |
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| Rok vydání: | 2010 |
| Předmět: |
Pb−Zn−Ag system
optical microscopy Ternary numeral system Chemistry General Chemical Engineering Thermodynamics Raoult's law desilvering of lead General Chemistry lcsh:Chemical technology Homogeneity (physics) thermodynamic prediction lcsh:TP1-1185 Ternary operation CALPHAD Phase diagram Thermodynamic process Eutectic system |
| Zdroj: | Hemijska Industrija, Vol 64, Iss 2, Pp 99-103 (2010) |
| ISSN: | 2217-7426 0367-598X |
| DOI: | 10.2298/hemind100115007m |
| Popis: | Physico-chemical processes that take place during the refining process in the extractive metallurgy of lead are associated with the ternary Pb-Zn-Ag system, hence it is necessary to study it from both theoretical and practical aspects. Such an investigation is important from the production point of view, because of the phenomena that occur during desilvering of lead which is one of the important stages in the lead refining process. The connection between the process of lead desilvering and the ternary Pb-Zn-Ag system was the reason for numerous investigations, both from a thermodynamic point of view and in terms of testing and determining the phase diagram, bearing in mind the theoretical and practical importance of knowledge about the processes that take place in the investigated system. The paper presents the results of thermodynamic analysis and investigation of phase equilibria of the Pb-Zn-Ag ternary system using the method of thermodynamic predictions and phase diagrams calculations, respectively, and the experimental results of metalography obtained by optical microscopy. The phase diagram of the vertical section Pb-Zn80Ag20 is presented, obtained by CALPHAD calculation methodology, and using PANDAT thermodynamic software, compared to experimental results obtained by DTA analysis. The results show a pronounced break in solubility, which is characteristic for the entire ternary Pb-Zn-Ag system. Also, it can be noticed that the thermodynamic properties follow the behavior of this system, which is expressed through positive deviation of Raoult's law, pointing to the lack of lead affinity compared to the other two components in the system. The optical microscopy results of the investigated system show the following: 1) sample L1 (98 mass% Pb): the structure of the observed section shows a double eutectic point (Pbsol+Zn-Agsol) which lies in the base of the primary crystals of lead (Pbsol); 2) samples L2-L5: the structure consists of a dual eutectic (Pbsol+Zn-Agsol) and primary crystals Zn-Agsol. Also, certain structural in homogeneity can be noticed as a consequence of stratification that occurs in the ternary Pb-Zn-Ag system. However, the metallographic investigation confirm the results obtained by defining the phase diagram and mutually agree relatively well in accordance to existing literature data. |
| Databáze: | OpenAIRE |
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