The aim of the present work is to evaluate the activation energy (Ea) at different cathodic overpotentials (η) by potentiodynamic tests which were carried out at different temperatures of Ni-based, NiCr-m, and NiCr-p porous electrodes, during the alkaline electrolysis processes. On the other hand, the electrochemical stability of the electrodes was evaluated by cyclic voltammetry after 1000 cycles of operation and by potentiostatic tests after 10 h at −1.5 V vs. SCE. The electrodes were sintered with a heating rate of 25 °C/min up to a temperature of 1000 °C (Ni-based and NiCr-m) and 1200 °C (NiCr-p) for 60 min. The results showed that the Ea value was lower for the Ni-based system at equilibrium; however, the NiCr-p electrode had a better performance due to higher negative apparent Ea values as a function of η (dEa/dη). The cyclic voltammetry tests suggest that the NiCr-p electrode improves its activity by about 71% in its long-term operation in comparison with Ni-based and NiCr-m. A similar behavior was observed in the potentiostatic test which showed a higher cathodic current density associated with a charge transfer process after 10 h. The higher stability of the NiCr-p is attributed to a homogeneous Cr distribution in the nickel matrix.

The present study shows the effect of Nb on a Ti matrix to fabricate composites via the conventional powder metallurgy for medical applications. Ti powder mixture compacts with different Nb contents were obtained from the conventional pressing and sintering technique. The sintering behavior was evaluated using the dilatometry technique, and the microstructure was studied using scanning electron microscopy (SEM) and X-ray diffraction (XDR). The mechanical properties were obtained from simple compression tests, and the corrosion resistance was determined from a standard three-electrode arrangement in Hank’s solution. The results showed that the Nb in the Ti matrix limits the evolution of sintering depending on the Nb content. Nb slightly accelerates the phase transition temperature. The microstructure and X-rays revealed that biphasic α + β-Ti structures can be obtained, in addition to retaining the β-Ti phase and forming the martensitic phases α′ and α″ of Ti. Likewise, the mechanical behavior showed a Young’s modulus of 10–45 GPa, which is close to that reported for human bones. Furthermore, the circuit analysis revealed that the Ti-Nb sintered systems were conditioned by the surface oxide layer and that the oxide layer formed within the residual pores of the sintering process. Finally, it was demonstrated that adding Nb to the Ti matrix increases the corrosion resistance and that contents close to 15 wt.% of this element have the best results.

This work aims to analyze the effect of pore size on the catalytic reaction of 316L stainless steel electrodes. Porous compacts were fabricated using the space holder technique and sintering at low temperatures. The fabricated porous compacts were characterized using computed tomography and the hydrogen evolution reaction was evaluated under 0.5 M and 1.5 M NaOH. Results indicate that porosity is well controlled by the pore formers, which allows different pore size distributions of pores with similar relative density values to be obtained. The pores are fully interconnected, allowing the passing of fluid throughout the compacts. Permeability is sensitive to the pore size, increasing as the pore size does. The catalytic activity of hydrogen evolution reaction HER is improved as the pore volume and pore size increase concerning the compact fabricated without pore formers. The compact that showed higher C_dl and R_f values was fabricated with S100 pore formers, which means a higher active area that favors the HER. It can be concluded that porosity enhances HER reactivity. However, larger pores are not beneficial due to a more significant permeability value.

This study investigates the hydrogen embrittlement (HE) susceptibility of two martensitic ultra-high-strength steel (M-UHSS) grades, focusing on their impact toughness and microhardness behavior following different durations of hydrogen cathodic charging (1, 2, and 4 h). While some mechanisms, such as the interaction between microstructural defects and hydrogen, are well established, the effects of hydrogen on the absorbed energy during impact tests or at high strain rates have been less studied. This study correlates the microstructural characteristics, Charpy-V absorbed energy, and microhardness with fractographic analysis to assess the HE susceptibility. The results show a decrease in both microhardness and toughness after one hour of charging, with the reductions ranging from 32% to 40%. However, as the charging time increased, both properties exhibited an increase, attributed to the interaction of hydrogen and its saturation on the steel’s surface. Fractographic analysis reveals a morphological change from brittle fracture to brittle fracture with localized plastic zones, driven by the interaction of hydrogen with the trapping sites within the steel. Permeability tests are conducted to quantify the hydrogen concentration, diffusion coefficients, and trapping sites. The results indicate significant hydrogen embrittlement in both steels, driven by hydrogen diffusion and accumulation in the entrapment zones, leading to increased brittleness over time. This study provides insights into the micromechanisms influencing mechanical properties and fracture behavior under hydrogen exposure.

This study aims to develop CoCrMo/xCu composites through liquid phase sintering. The primary focus is on investigating how the addition of copper influences sintering kinetics, microstructure, and mechanical properties. The copper volume fraction ranged from 10 to 25 wt.% relative to CoCrMo. Sintering was conducted at 1150 °C under an argon atmosphere. Characterization methods included scanning electron microscopy, computed microtomography, and X-ray diffraction analysis. It was observed that molten copper, which forms upon reaching its melting temperature, can fill the interparticle spaces left by CoCrMo particles in the green compacts. During sintering, densification is further enhanced by the dissolution of CoCrMo, resulting in the formation of intermetallic phases enriched in Cr and Mo, as well as a ternary Co-Cr-Cu compound. Both densification and intermetallic formation contribute to increased microhardness as Cu content rises. It is concluded that the CoCrMo/25Cu composite exhibits the best mechanical and corrosion properties because its densification was improved by the Cu liquid.