Aleksandra Mitovski

Comparative thermodynamic analysis and phase diagram prediction of the Ga-Sn-Zn system

Abstract The results of comparative thermodynamic analysis and phase diagram prediction of the Ga – Sn – Zn system are presented in this work. The thermodynamic study was done experimentally – using Oelsen calorimetry, for the section Ga – SnZneut, and analytically – according to the general solution model, for the whole system. Main thermodynamic quantities – integral and partial molar Gibbs excess energies, activities and activity coefficients were calculated over a wide temperature range. Additionally, the phase diagram of the section Ga – SnZneut was investigated using differential thermal analysis and predicted using the CALPHAD method. Comparison with available literature data showed reasonable agreement. The liquidus projection of the ternary Ga – Sn – Zn was also calculated.

Reaction mechanism and kinetics of sulfide copper concentrate oxidation at elevated temperatures

Sulfide copper concentrate from domestic ore deposit (Bor, Serbia) was subjected to oxidation in the air atmosphere due to a better understanding of reaction mechanism and oxidation of various sulfides present in the copper concentrate at elevated temperatures. Results of the initial sample characterization showed that concentrate is chalcopyrite–enargite-tennantite type, with an increased arsenic content. Characterization of the oxidation products showed the presence of sulfates, oxysulfates, and oxides. Based on predominance area diagrams for Me-S-O systems (Me = Cu, Fe, As) combined with thermal analysis results, the reaction mechanism of the oxidation process was proposed. The reactions which occur in the temperature range 25 – 1000 °C indicate that sulfides are unstable in the oxidative conditions. Sulfides from the initial sample decomposed into binary copper and iron sulfides and volatile arsenic oxides at lower temperatures. Further heating led to oxidation of sulfides into iron oxides and copper sulfates and oxysulfates. At higher temperatures sulfates and oxysulfates decomposed into oxides. Kinetic analysis of the oxidation process was done using Ozawa’s method in the non-isothermal conditions. The values for activation energies showed that the reactions are chemically controlled and the temperature is the most influential parameter on the reaction rates.

Thermal and structural characteristics of a eutectic Au-Ge alloy

Abstract The Au-Ge alloy is useful for bonding applications in microelectronic and optoelectronic packages. Also, recent investigations show that Au-Ge system could present a lead-free solder candidate. The results of characterization of the eutectic alloy from binary Au-Ge system are presented in this paper. Experimental research was done using thermal analysis (differential thermal analysis, DTA) and structural investigation by light optic microscopy (LOM) and scanning electron microscopy with EDS (SEM-EDS). The eutectic temperature of 359 °C was detected using thermal analysis, while eutectic structure was confirmed using microstructural analysis. Obtained results were compared with recent literature references and good mutual agreement was noticed.

Renewable Thermoenergetic Resources in the Pyrometallurgical Copper Production Process

Pyrometallurgical copper production is a big consumer of energy resources of all kinds. A large part of invested energy is used in the metallurgical process. The process products are holders of large energy amount that is lost uncontrolled in the environment, thereby affecting adversely the economic and environmental effects.