The use of nanotechnology in the piezoelectric industry conveys new concerns about the environmental toxicity related to lead based nanomaterials. Perovskite structured materials are extensively used as piezoelectrics, lead zirconate titanate (PZT) being the primary choice for sensors, actuators, etc., because of its powerful electromechanical conversion. However, during the life cycle of PZT piezoelectrics lead generally leaches into the environment over time, leading to human exposure and potential environmental hazard. Lead-free bismuth based-ferroelectric materials (BNT-BT) are promising substitutes due to their ability to provide all the piezoelectric attributes without leaching toxic material. Yet, little is known about the potential toxicity and interactions of these nanomaterials with biomolecules and their subsequent intracellular localization at the nanoscale. The aim of this study was to compare the biological impact and uptake of lead and bismuth-based piezoelectric nanoparticles in order to present a suitable substitute for the piezoelectric industry. Our results show that BNT-BT and PZT nanoparticles were internalized through the endolysosomal pathway following first order kinetics, nanoparticles were localized in the lamellar bodies without inducing cell toxicity measured by mitochondrial activity and cell membrane integrity. Furthermore, BNT-BT nanoparticles were more stable as lead-based PZT released 20% more lead ions into cell culture media. Finally, we propose bismuth-based BNT-BT as a suitable candidate for commercial use as they avoid environmental leaching, imposing less risk during manufacturing and in occupational health, beside having high biocompatibility and similar physico-chemical properties.

In this research work, a preliminary potentiodynamic polarization performance testing was carried out on a new environmentally friendly proposed composite coating. The proposed composite coating was developed by: (a) hot sulfuric anodizing to produce an Al₂O₃ conversion film followed by an (b) organic electrodeposited chitosan–sodium alginate blended film. Posteriorly, the conversion and organic films were microstructurally characterized by scanning electron microscopy. Finally, the polarization resistance technique was used to measure the corrosion resistance of the uncoated and coated AA6063 alloy in a simulated marine environment and the polarization tests were compared to samples immersed during 30 days in same electrolyte solution. The obtained inhibition corrosion efficiency of the proposed coating system was measured comparing the Rp of the uncoated alloy to the coated samples, showing an efficiency about 99% for a 3% NaCl electrolyte for some of the samples. Therefore, the experimental results obtained during this research demonstrates the feasibility of using the developed anticorrosive composite coating to protect aluminum alloys against chloride corrosive ions species and to further continue with the corresponding research.

The present research deals with the comparative wear behavior of a mechanically milled Al-6061 alloy and the same alloy reinforced with 5 wt.% of Al₂O₃ nanoparticles (Al-6061-Al₂O₃) under different dry sliding conditions. For this purpose, an aluminum-silicon-based material was synthesized by high-energy mechanical alloying, cold consolidated, and sintered under pressureless and vacuum conditions. The mechanical behavior was evaluated by sliding wear and microhardness tests. The structural characterization was carried out by X-ray diffraction and scanning electron microscopy. Results showed a clear wear resistance improvement in the aluminum matrix composite (Al-6061-Al₂O₃) in comparison with the Al-6061 alloy since nanoparticles act as a third hard body against wear. This behavior is attributed to the significant increment in hardness on the reinforced material, whose strengthening mechanisms mainly lie in a nanometric size and homogeneous dispersion of particles offering an effective load transfer from the matrix to the reinforcement. Discussion of the wear performance was in terms of a protective thin film oxide formation, where protective behavior decreases as a function of the sliding speed.