Titanium alloys are used in medical devices due to their mechanical properties, but also for their corrosion resistance. The natural passivation of titanium-based biomaterials, on the surface of which a dense and coherent film of nanometric thickness is formed, composed mainly of TiO₂, determines an apparent bioactivity of them. In this paper, the method of obtaining new Ti20MoxSi alloys (x = 0.0, 0.5, 0.75, and 1.0) is presented, their microstructure is analyzed, and their electrochemical responses in Ringer´s solution were systematically investigated by linear polarization, cyclic potential dynamic polarization, and electrochemical impedance spectroscopy (EIS). The alloys corrosion resistance is high, and no evidence of localized breakdown of the passive layer was observed. There is no regularity determined by the composition of the alloys, in terms of corrosion resistance, but it seems that the most resistant is Ti20Mo1.0Si.

The increased popularity of Ti and its alloys as important biomaterials is driven by their low modulus, greater biocompatibility, and better corrosion resistance in comparison to traditional biomaterials, such as stainless steel and Co–Cr alloys. Ti alloys are successfully used in severe stress situations, such as Ti–6Al–4V, but this alloy is related to long-term health problems and, in response, different Ti alloys composed of non-toxic and non-allergic elements such as Nb, Zr, Mo, and Ta have been developed for biomedical applications. In this context, binary alloys of titanium and tantalum have been developed and are predicted to be potential products for medical purposes. More than this, today, novel biocompatible alloys such as high entropy alloys with Ti and Ta are considered for biomedical applications and therefore it is necessary to clarify the influence of tantalum on the behavior of the alloy. In this study, various Ti–xTa alloys (with x = 5, 15, 25, and 30) were characterized using different techniques. High-resolution maps of the materials’ surfaces were generated by scanning tunneling microscopy (STM), and atom distribution maps were obtained by energy dispersive X-ray spectroscopy (EDS). A thorough output of chemical composition, and hence the crystallographic structure of the alloys, was identified by X-ray diffraction (XRD). Additionally, the electrochemical behavior of these Ti–Ta alloys was investigated by EIS in simulated body fluid at different potentials. The passive layer resistance increases with the potential due to the formation of the passive layer of TiO₂ and Ta₂O₅ and then decreases due to the dissolution processes through the passive film. Within the Ti–xTa alloys, Ti–25Ta demonstrates excellent passive layer and corrosion resistance properties, so it seems to be a promising product for metallic medical devices.

The analysis of energy consumption in reverse osmosis desalination plants is the most important and relevant factor to study, because this parameter indicates the level of efficiency and competitiveness of the plant. The direct consequence of the high specific energy consumption (SEC) of a desalination plant in the production of water is one of the main obstacles to the exponential expansion of this technology worldwide. The methodological procedure used to carry out the work is based on the analysis of energy consumption, maintenance costs, staff, membranes, and reagents of three desalination plants with a production of more than 23,000 m³/day located in the Canary Islands (Spain); all data are obtained from real analyses collected “in situ” from 2015 to 2018. One of the main objectives of the current research on desalination plants is to reduce the SEC of seawater desalination plants (SWRO), incorporating energy recovery systems (ERS) and high efficiency pumps (HEP), and to implement different operational configurations with the aim of minimizing the energy requirements necessary to obtain a good product quality at minimum production cost.

Depending on the properties required for the medical instruments, compared with the classical materials, the high-entropy alloys (HEAs) are a versatile option. Electrochemical Impedance Spectroscopy (EIS) measurements have been performed on AlxCoCrFeNi-type high-entropy alloys with various concentrations of Al content (x = 0.6, 0.8, and 1.0) in order to characterize their passive film and corrosion resistance at 37 °C under infectious simulated physiological conditions (Ringer´s solution acidulated with HCl) at pH = 3. The impedance spectra were obtained at different potential values between −0.7 and +0.7 V vs. SCE. Analysis of the impedance spectra was carried out by fitting different equivalent circuits to the experimental data. Two equivalent circuits, with one time constant and two time constants respectively, can be satisfactorily used for fitting the spectra: one time constant represents the characteristics of the compact passive film, and the second one is for the porous passive film. With the decreasing of Al content, the obtained EIS results are correlated with the evolution of the microhardness and microstructure, which is characterized by Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Energy-Dispersive X-Ray Spectroscopy (EDAX). It can be observed for all alloys that the resistance of the passive film is very high and decreases with the potential: the very high resistance of the passive film implies a high corrosion resistance, which can be assigned to the formation of the protective oxide layer and demonstrates that the analyzed alloys fulfill the prerequisites for their use as new materials for the manufacturing of medical instruments.

Ti and its alloys have the most satisfactory properties for biomedical applications due to their specific strength, high corrosion resistance, and high biocompatibility. Ti-6Al-7Nb has been approved for clinical use, proving to be a viable replacement for the Ti-6Al-4V alloy that has been used for many decades in medical applications. In our study, the Ti-6Al-7Nb alloy underwent heat treatment, was cooled in various cooling media such as mineral oil and water, and was then quenched in the oven. The microstructure was investigated, and the mechanical characterization was carried out by Vickers microhardness test. Young’s modulus measurements and tensile tests were performed in order to study the effect of cooling media on the material. To study the corrosion behavior, in vitro studies were performed on the Ti-6Al-7Nb samples in simulated body conditions by using artificial saliva. It was observed that the martensitic phase changed as a function of cooling media, and a less intensive cooling medium decreases strength properties’ indicators as well as hardness values. The results emphasize that the use of heat treatment improves the passive layer’s resistance in the presence of artificial saliva.