Dragan Manasijević

The thermochemical extraction of titanium group metals (Ti, Zr, Hf) is limited by the extreme thermodynamic stability of their oxides. This study presents a thermodynamic assessment of carbothermic, metallothermic, and halide-based processes using HSC Chemistry 10 software. Ellingham and predominance area diagrams (Ti-C-O, Zr-C-O, Hf-C-O) show that direct carbothermic reduction is inhibited by stable carbide formation, requiring temperatures above 1700 °C for Ti and above 2000 °C for Zr and Hf under high vacuum. Calcium is the only metal considered here that is thermodynamically capable of direct oxide reduction; however, kinetic barriers and product-layer formation limit its practical use. In contrast, carbochlorination lowers the thermodynamic barrier by converting stable oxides into volatile chlorides, which can subsequently be reduced by Mg or Na. This work provides a unified thermodynamic comparison that explains the industrial preference for the Kroll and Hunter processes and identifies favorable operating ranges for titanium group metal extraction.

In the present study, the Sn78Bi22 alloy was investigated as a potential solder material. The study focused on the evaluation of thermal diffusivity and thermal conductivity over a defined temperature range, differential scanning calorimetry (DSC) analysis, and an assessment of soldering behavior through measurements of contact angle, spreading area, spreading ratio, and intermetallic compound (IMC) layer thickness. The investigated alloy exhibited reduced thermal diffusivity and thermal conductivity compared with literature data for pure Sn. DSC analysis indicated a decrease in melting temperature compared with pure Sn reported in the literature, resulting from the addition of Bi. Soldering behavior was evaluated as favorable, characterized by a thin IMC layer, a low contact angle on a Cu substrate, and high spreading ratio and spreading area. Based on these results, the Sn78Bi22 alloy shows potential for lead-free soldering applications.

The development of reliable lead-free solder alloys remains essential for applications in the electronics industry. This paper investigates the mechanical, electrical, and microstructural properties of a Sn78Bi22 solder alloy. The alloy was prepared by melting and casting, followed by a homogenization heat treatment. Tensile testing, Vickers microhardness measurements, electrical conductivity testing, and SEM/EDS microstructural analysis were performed at room temperature. The investigated alloy exhibited enhanced ultimate tensile strength (~93 MPa) and microhardness (45.5 HV0.05) compared with pure Sn, while electrical conductivity decreased to 5.4 MS/m. These changes were attributed to solid-solution strengthening, grain refinement, and the formation of a Bi-rich secondary phase, which also promoted brittle fracture during tensile testing. Microstructural observations revealed a Sn matrix with finely distributed Bi-rich phases, particularly along grain boundaries. The results contribute additional experimental data on the mechanical, electrical, and microstructural characteristics of non-eutectic Sn-Bi solder alloys.

Ternary alloys of the Sn-Ag-Cu (SAC) system represent one of the most widely used lead-free solder materials due to their favorable mechanical properties and compliance with environmental regulations aimed at eliminating toxic lead from electronic components. Among these alloys, SAC338 (Sn-3.3Ag-0.8Cu) is recognized as one of the most promising alternatives to conventional Sn-Pb solders. Despite their ecological advantages, SAC alloys still exhibit challenges associated with the growth of intermetallic compounds and microstructural instability. The aim of this study was to investigate the influence of graphene nanosheet (GNS) additions on the microstructural properties of SAC composite. SAC composite containing up to 0.09 wt.% GNS were produced using powder metallurgy procedures. The results showed that the addition of GNS contributed to a more homogeneous microstructure and refinement of intermetallic phases such as Cu6Sn5 and Ag3Sn. The addition of GNS improves the wettability of the composite solder by reducing the wetting angle, which enables better spreading of the molten solder and improves the quality of solder joints. From an environmental perspective, these improvements contribute to enhanced durability and longer service life of electronic components, leading to reduced material consumption, lower maintenance frequency, and decreased generation of electronic waste.

In this paper, a thermodynamic analysis of rare earth metal extraction processes is presented. The thermodynamic stability of rare earth metal oxides, fluorides, and chlorides was analyzed, as well as the conditions for their reduction using various reducing agents. The study also examines the thermodynamic basis of the halogenation process of rare earth metal oxides, with predominance diagrams used to describe phase equilibria in metal-oxygen-halogen systems. These diagrams enable clear identification of the stability regions of oxides, oxyhalides, and halides and represent an important tool in the design of industrial processes. In addition, the paper links the results of thermodynamic calculations with industrial practice through an analysis of the most important rare earth metal production technologies. Particular emphasis is placed on the thermal effects of reactions and the energy requirements of metallothermic processes. The results confirm the importance of modern thermodynamic analysis and software tools in process optimization and in the selection of efficient technologies for rare earth metal production.