The increase in longevity worldwide has intensified the use of different types of prostheses for the human body, such as those used in dental work as well as in hip and knee replacements. Currently, Ti-6Al-4V is widely used as a joint implant due to its good mechanical properties and durability. However, studies have revealed that this alloy can release metal ions or particles harmful to human health. The mechanisms are not well understood yet and may involve wear and/or corrosion. Therefore, in this work, commercial pure titanium and a Ti-6Al-4V alloy were investigated before and after being exposed to a simulated biological fluid through tribological tests, surface analysis, and ionic dissolution characterization by ICP-AES. Before exposure, X-ray diffraction and optical microscopy revealed equiaxed α-Ti in both materials and β-Ti in Ti-6Al-4V. Scratch tests exhibited a lower coefficient of friction for Ti-6Al-4V alloy than commercially pure titanium. After exposure, X-ray photoelectron spectroscopy and surface-enhanced Raman spectroscopy results showed an oxide film formed by TiO₂, both in commercially pure titanium and in Ti-6Al-4V, and by TiO and Al₂O₃ associated with the presence of the alloys. Furthermore, inductively coupled plasma atomic emission spectroscopy revealed that aluminum was the main ion released for Ti-6Al-4V, giving negligible values for the other metal ions.

Fuel cell technology has developed due to diminishing dependence on fossil fuels and carbon footprint production. This work focuses on a nickel–aluminum bronze alloy as an anode produced by additive manufacturing as bulk and porous samples, studying the effect of designed porosity and thermal treatment on mechanical and chemical stability in molten carbonate (Li₂CO₃-K₂CO₃). Micrographs showed a typical morphology of the martensite phase for all samples in as-built conditions and a spheroid structure on the surface after the heat treatment, possibly revealing the formation of molten salt deposits and corrosion products. FE-SEM analysis of the bulk samples showed some pores with a diameter near 2–5 μm in the as-built condition, which varied between 100 and −1000 μm for the porous samples. After exposure, the cross-section images of porous samples revealed a film composed principally of Cu and Fe, Al, followed by a Ni-rich zone, whose thickness was approximately 1.5 µm, which depended on the porous design but was not influenced significantly by the heat treatment. Additionally, by incorporating porosity, the corrosion rate of NAB samples increased slightly.

In this study, the effect of the recycling process and copper particle incorporation on virgin and recycled pellet HDPE were investigated by thermo-chemical analysis, mechanical characterization, and antibacterial analysis. Copper particles were added to pellet HDPE, virgin and recycled, using a tabletop single screw extruder. Some copper particles, called copper nano-particles (Cu-NPs), had a spherical morphology and an average particle size near 20 nm. The others had a cubic morphology and an average particle size close to 300 nm, labeled copper nano-cubes (Cu-NCs). The thermo-chemical analysis revealed that the degree of crystallization was not influenced by the recycling process: 55.38 % for virgin HDPE and 56.01% for recycled HDPE. The degree of crystallization decreased with the addition of the copper particles. Possibly due to a modification in the structure, packaging organization, and crystalline ordering, the recycled HDPE reached a degree of crystallization close to 44.78% with 0.5 wt.% copper nano-particles and close to 36.57% for the recycled HDPE modified with 0.7 wt.% Cu-NCs. Tensile tests revealed a slight reduction in the tensile strength related to the recycling process, being close to 26 MPa for the virgin HDPE and 15.99 MPa for the recycled HDPE, which was improved by adding copper particles, which were near 25.39 MPa for 0.7 wt.% copper nano-cubes. Antibacterial analysis showed a reduction in the viability of E. coli in virgin HDPE samples, which was close to 8% for HDPE containing copper nano-particles and lower than 2% for HDPE having copper nano-cubes. In contrast, the recycled HDPE revealed viability close to 95% for HDPE with copper nano-particles and nearly 50% for HDPE with copper nano-cubes. The viability of S. aureus for HDPE was lower than containing copper nano-particles and copper nano-cubes, which increased dramatically close to 80% for recycled HDPE with copper nano-particles 80% and 75% with copper nano-cubes.

This work presents the effect of CeO₂ nanoparticles (CeO₂–NPs) on Cu–50Ni–5Al alloys on morphological, microstructural, degradation, and electrochemical behavior at high temperatures. The samples obtained by mechanical alloying and spark plasma sintering were exposed to a molten eutectic mixture of Li₂CO₃–K₂CO₃ for 504 h. The degradation of the materials was analyzed using gravimetry measurements and electrochemical impedance spectroscopy. Different characterization techniques, such as X-ray diffraction and scanning electron microscopy, were used to investigate the phase composition, parameter lattice, and microstructure of Cu–Ni–Al alloys reinforced with CeO₂–NPs. The hardness of the composite was also examined using the Vickers hardness test. Gravimetry measurements revealed that the sample with 1 wt.% CeO₂–NPs presented the best response to degradation with a less drastic mass variation. Impedance analysis also revealed that by adding 1 wt.% CeO₂–NPs, the impedance modulus increased, which is related to a lower porosity of the oxide film or a thicker oxide layer. The microhardness also significantly increased, incorporating 1 wt.% CeO₂–NPs, which reduced with higher CeO₂–NPs content, which is possibly associated with a more uniform distribution using 1 wt.% CeO₂–NPs in the Cu–Ni–Al matrix that avoided the aggregation phenomenon.