Biodegradable alloys and especially magnesium-based alloys are considered by many researchers as materials to be used in medicine due to their biocompatibility and excellent mechanical properties. Biodegradable magnesium-based materials have applications in the medical field and in particular in obtaining implants for small bones of the feet and hands, ankles, or small joints. Studies have shown that Mg, Zn, and Ca are found in significant amounts in the human body and contribute effectively and efficiently to the healing process of bone tissue. Due to its biodegradability, magnesium alloys, including Mg–Ca–Zn alloys used in the manufacture of implants, do not require a second surgery, thus minimizing the trauma caused to the patient. Other studies have performed Mg–Ca–Zn system alloys with zinc variation between 0 and 8 wt.% and calcium variation up to 5 wt.%, showing high biocompatibility, adequate mechanical properties, and Mg₂Ca and Mg₆Ca₂Zn compounds in microstructure. Biocompatibility is an essential factor in the use of these materials, so that some investigations have shown a cell viability with values between 95% and 99% compared with the control in the case of Mg–0.2Ca–3Zn alloy. In vivo analyses also showed no adverse reactions, with minimal H${}_2$ release. The aim of this review includes aspects regarding microstructure analysis and the degradation mechanisms in a specific environment and highlights the biocompatibility between the rate of bone healing and alloy degradation due to rapid corrosion of the alloys.

The present article focuses on a recently developed new system of alloys (Ti15MoSi) coated with ZrO₂. The thin coatings deposition of ZrO₂ on titanium alloys can be a solution to improve their corrosion resistance, biocompatibility, and to extend their long life with the human tissue. In order to improve the corrosion resistance, atmospheric plasma spraying coatings with zirconia have been performed. These coatings present a homogenous aspect with very few cracks. The novelty of the research is that zirconia is much stable in the simulated body fluids and presents no harm effects to the healing process of the bone. To analyze the thin coatings deposition, mechanical properties, chemical structure, and corrosion resistance were examined by a modulus of elasticity, X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), and linear polarization. The results reveal that Young’s modulus shows a low value (51 GPa for Ti15Mo0.5Si-ZrO₂ and 48 GPa for Ti15Mo-ZrO₂) and the XRD patterns show the presence of β-Ti and ZrO₂ phases having a tetragonal crystalline structure. The research highlighted the morphological aspect of zirconia coatings on the new alloy titanium substrate, being an adherent compact coating with significantly improved corrosion resistance. Moreover, the mechanical properties are similar to the biological bone, which will avoid the stress shielding of the implant with bone tissue.

Water treatment plants include a set of pumping stations, and their mechanical components experience various wear modes. In order to combat wear, the mechanical components of the pumps are coated with various types of wear resistant coatings. In this research, AMDRY 1371 (Mo–NiCrFeBSiC) coatings were deposited with the atmospheric plasma spray (APS) method on parallelepipedal steel samples manufactured from a worn sleeve of a multistage vertical irrigation pump. In order to find an optimum thickness of AMDRY 1371 coatings, the samples were coated with five, seven and nine passes (counted as return passes of the APS gun). Mechanical properties of the coating (microhardness and Young’s modulus) were determined by micro-indentation tests. An AMSLER tribometer was used to investigate the wear resistance and wear modes of the coated samples in dry conditions. A mean coefficient of friction (CoF) of around 0.3 was found for all the samples, but its evolution during the one hour of the test and also the final wear volumes and wear rates depended on the thickness of the coating. To estimate the roughness of the surfaces and the wear volumes, measurements were carried out on a Taylor Hobson profilometer. In order to understand the nature and evolution of wear of coatings of various thicknesses, the unworn and worn surfaces of the coated samples were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The wear modes of the coatings were studied, emphasizing the coating removal process for each sample. According to our results, for each dry friction application, there is an optimum value of the thickness of the coating, depending on the running conditions.

Pharmaceuticals and dyes are a very important part of the nonbiodegradable or hard biodegradable substances present in wastewater. Microorganisms are already known to be effective biosorbents, but the use of free microbial cells involves difficulties in their separation from effluents and limits their application in wastewater treatment. Thus, this study aimed to develop biosorbents by immobilizing Saccharomyces cerevisiae, Saccharomyces pastorianus and Saccharomyces pastorianus residual biomass on natural polymers (alginate and chitosan) and to evaluate the biosorptive potential for removal of pharmaceuticals and dyes from water. Six types of biosorbents were synthesized and characterized by Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy techniques and their biosorptive capacities for three drugs (cephalexin, rifampicin, ethacridine lactate) and two dyes (orange II and indigo carmine) were evaluated. The obtained results show that the removal efficiency depends on the polymer type used for the immobilization. In case of alginate the removal efficiency is between 40.05% and 96.41% for drugs and between 27.83% and 58.29% for dyes, while in the case of chitosan it is between 40.83% and 77.92% for drugs and between 17.17% and 44.77% for dyes. In general, the synthesized biosorbents proved to be promising for the removal of drugs and dyes from aqueous solutions.

In recent years, biodegradable materials have included magnesium alloys with homogenous disintegration and a controllable degradation rate. Utilized in medical applications, biodegradable materials based on magnesium have been widely explored throughout the years. It is well-known that alloying Mg with biocompatible and non-toxic elements increases the biodegradability of surgical alloys. The purpose of this study was to examine the microstructure and the electrochemical response (corrosion resistance) of a new experimental Mg-based biodegradable alloy—Mg–0.5%Ca with additions of Zn as follows: 0.5, 1.5, and 3.0 wt.% in order to control the corrosion rate. Immersion tests were performed for different periods in a simulated body fluid electrolyte solution at 37 °C, and the mass loss was appreciated in order to calculate the corrosion rate (CR). The investigation led to the discovery of a dendritic Mg solid solution, a lamellar Mg₂Ca compound, and a MgZn₂ intermetallic phase. Scanning electron microscopy, optical microscopy, and energy dispersive spectroscopy were used for surface analysis after the immersion and electro-corrosion resistance tests. The metallic and ceramic compounds that detached themselves from the sample and passed into the solution were evaluated using the SEM-EDS system. All samples presented a generalized electro-corrosion with anodic and cathodic reactions of similar intensity. The corrosion rate was similar regardless of the percentage of zinc, with a smaller value for a higher than 3 wt.% Zn percentage based on the more protective zinc oxide that appeared on the surface.

Stefan Lupescu, Bogdan Istrate, Corneliu Munteanu, Mirabela Georgiana Minciuna, Sergiu Focsaneanu, Kamel Earar - Characterization of Some Master Mg-X System (Ca, Mn, Zr, Y) Alloys Used in Medical Applications