This study investigated the synthesis of Ag-SnO₂-ZnO by powder metallurgy methods and their subsequent electrical contact behavior. The pieces of Ag-SnO₂-ZnO were prepared by ball milling and hot pressing. The arc erosion behavior of the material was evaluated using homemade equipment. The microstructure and phase evolution of the materials were investigated through X-ray diffraction, energy-dispersive spectroscopy and scanning electron microscopy. The results showed that, although the mass loss of the Ag-SnO₂-ZnO composite (9.08 mg) during the electrical contact test was higher than that of the commercial Ag-CdO (1.42 mg), its electrical conductivity remained constant (26.9 ± 1.5% IACS). This fact would be related to the reaction of Zn₂SnO₄’s formation on the material’s surface via electric arc. This reaction would play an important role in controlling the surface segregation and subsequent loss of electrical conductivity of this type of composite, thus enabling the development of a new electrical contact material to replace the non-environmentally friendly Ag-CdO composite.

Currently, mining operations have increased the generation of tailings, which contain a variety of elements that can be valorized. In this research, tailing samples were leached with hydrochloric acid of concentrations greater than 3 M, considering the monitoring of iron, copper, aluminum, calcium and magnesium, as relevant elements of the leached solution. Time and temperature were also studied. The original tailing sample was taken by trial pits, and a size distribution analysis was performed. The process generated an insoluble solid, rich in aluminosilicates, and an acid liquid solution with different metal ions. Elemental analyses were performed on liquid samples by Atomic Absorption Spectroscopy (AAS), and solid samples by Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDX) and X-ray Diffraction (XRD). Results showed an increasing trend of the iron concentration as a function of the acid concentration. However, copper is not affected by the change in acid concentration, but by time and temperature. Aluminum decreases with acid concentration, keeps constant with time, and yields at 50 °C. In the range of the studied parameters, calcium and magnesium showed a variation without a clear trend. The elements in the acid solution prepared with a tailing from northern Chile can be recovered for subsequent applications.

In this study, weak acid in the curing and leaching stages of copper ore was incorporated, and we analyzed its effect on the dissolution of copper and final impurities. The weak acid corresponds to a wastewater effluent from sulfuric acid plants produced in the gas treatment of copper smelting processes. This effluent is basically water with high acidity (pH-value low at 1), which contains several toxic elements and some valuable metals. The results indicated that there is no positive or negative effect on the incorporation of the weak acid in the curing stage, while the case of the leaching stage is favored. Toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP) toxicity tests were performed on the solid leaching residues, determining that they accomplish the stability ranges of the impurities (Pb, Cd, Hg, Cr, Ba, Se, As, and Ag).

TRIP-assisted CMnSiAl steels with a fully martensitic initial microstructure have been studied in order to investigate the effect of partial substitution of Si by Al. The steel was fabricated by casting in a sand mold, hot forged, homogenizing, hot rolling, cold rolling, intercritical annealing, and finally, an isothermal bainitic treatment. During the intercritical annealing at 1023 K (750 °C) for 420 s, a matrix with a microstructure consisting of 50% proeutectoid ferrite was induced and after isothermal treatment at 663 K (390 °C) for 300 s, a microstructure of ferrite, bainite, and retained austenite was obtained. This austenite was carbon enriched and therefore stabilized, with an M_s lower than original austenite, before bainitic treatment. Microstructure and tensile properties have been analyzed, comparing these results with those corresponding to a commercial TRIP 780 steel. During tensile tests, retained austenite changes from 8.1 to 1.9%vol, with a total elongation of 23.2%, which demonstrates the TRIP effect. Texture analysis showed a weak γ-fiber in the steel, which deteriorates the drawing properties of the steel. The maximum elongation during the tensile test of this steel was obtained at 323 K (50 °C), correlating with the TRIP effect present in steel, which is favored when working within the critical zone of temperatures $M_s^{\sigma }$ and $M_d$. The results show that partial substitution of Si by Al decreases yield stress, ultimate tensile strength, increases the total elongation, and decreases the temperature for maximum elongation, related to TRIP 780.

Ag-based electrical contact materials are essential in low-voltage devices such as relays, switches, circuit breakers, and contactors. Historically, Ag-CdO composites have been preferred due to their superior electrical and thermal conductivities, resistance to arcing, and mechanical strength. However, the toxicity of Cd has led to increased restrictions on its use. With the aim of contributing to the development of a new environment-friendly, Ag-Zn₂SnO₄-based electrical contact material, the kinetics of the hot mechanochemical oxidation of a Ag-Sn-Zn solid solution obtained by mechanical alloying were investigated. The results indicated that the proposed synthesis route produces Ag-based composites with a homogeneous distribution of nanoscale Zn₂SnO₄ precipitates, which is unattainable through conventional material processing methods. This kinetic study established that the mechanochemical oxidation of the Ag-Sn-Zn solid solution follows the Johnson–Mehl–Avrami–Kolmogorov model. An analysis of the microstructure and the relationship between the activation energy “Ea” and the Avrami exponent “n” from experimental data fitting suggests that the primary mechanism for the oxidation of the Ag-Sn-Zn solid solution during the hot mechanochemical process is related to the three-dimensional oxide growth being limited by oxygen diffusion after its immediate initial nucleation.

Although the importance of black copper ores is well established, many topics remain to be studied. This manuscript describes the efforts to improve copper recovery from refractory ores on a pilot scale. Preliminary tests provided the water dose to form a stable and compact agglomerate of 89 L per ton of ore and an acid dosage of 40 kg per ton of ore. The column leaching method resulted in an effluent with 1.63 g/L Cu, a pH of 1.04, and a redox potential of 675 mV (average). Despite the similarities observed in the results, reductant agents were essential to dissolve the MnO₄ present in the black copper ore. Thus, the best Mn extraction results were 67.7% using the MnO₂:FeSO₄ ratio of 1:3. Additionally, the kinetics of leaching are slower than in an industrial operation. The copper ore under study required more than 65 days of leaching to reach the maximum copper recovery. Finally, the total recovery of copper (including washing and resting time) indicates that the maximum value was reached for ore pretreated with NaCl, H₂SO₄, and FeSO₄, concluding that the use of agents favored leaching.