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The bactericidal properties of copper oxide nanoparticles have growing interest due to potential application in the medical area. The present research investigates the influence of sodium dodecyl sulfate (SDS) and poly(vinylpyrrolidone) (PVP) on the production of copper oxide nanoparticles prepared from copper sulfate (CuSO4) and sodium borohydride (NaBH4) solutions. Different analytical techniques were used to determine the crystal nature, mean size diameter, and surface morphology of the copper oxide nanoparticles. The X-ray diffraction (XRD) patterns showed formation of nanoparticles of cuprite (Cu2O) and tenorite (CuO) when PVP and SDS were added at the beginning of the reaction. In fact, when the Cu/PVP ratio was 1.62, Cu2O nanoparticles were obtained. In addition, nanoparticles of CuO were synthesized when the Cu/PVP ratios were 0.54 and 0.81. On the other hand, a mixture of copper oxides (CuO and Cu2O) and cuprite (Cu2O) was obtained when PVP (Cu/PVP = 0.81 and 1.62) and SDS (Cu/SDS = 0.90) were added 30 min after the beginning of the reaction. Transmission electron microscopy (TEM) images show agglomerated nanoparticles with a size distribution ranging from 2 to 60 nm, while individual particles have sizes between 4.1 ± 1.9 and 41.6 ± 12.8 nm. The Kirby-Bauer method for the determination of antibacterial activity shows that small CuO (4.1 ± 1.9 nm) and Cu2O (8.5 ± 5.3 nm) nanoparticles inhibit the growth of Escherichia coli, Staphylococcus aureus MRSA, S. aureus and Pseudomonas aeruginosa bacteria. The antibacterial test of cotton fabric impregnated with nanoparticles shows positive results. The determination of the optimal ratio of copper oxide nanoparticles per cm2 of fabric that are able to exhibit a good antibacterial activity is ongoing., SCOPUS: ar.j, info:eu-repo/semantics/published

Nanoparticles of fluorapatite (FAp Nps) were prepared by one step chemical reaction in aqueous solutions. The pH of the system was kept constant at 6 and 8. The FAp Nps were characterized with Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDAX), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The Ca/P calculated from EDAX analysis was 1.69. The results of XRD analysis and FTIR showed the presence of FAp phases. The DRX results confirm the formation of FAp with a hexagonal structure. TEM images show semispherical and elongated nanoparticles with mean diameter of 3.78 nm, 8.63 nm and 10.46 nm, when the pH and ammonia concentrations is varied. Ammonia concentration and pH influence the morphology and size of the FAp Nps., SCOPUS: ar.j, info:eu-repo/semantics/published

This work investigates the microstructure and mechanical characteristics of the Inconel 625 weld cladding deposited by the ESW process with a single layer on ASTM A516 Gr. 70 steel plate with a heat input of 11.7 kJ/mm. Microhardness testing and metallographic examination were performed on samples removed transversally from the weld deposit. Metallographic characterization was performed by optical, scanning, and transmission electron microscopy and by electron backscattering diffraction. Energy-dispersive spectrometry was also used to evaluate the composition of the secondary phases. Metallographic examination of the austenitic weld metal was carried out at locations 1 mm and 3 mm from the fusion line. The results revealed that in addition to the absence of partially diluted zones, the austenitic microstructure of the weld metal contains low volume fractions of secondary phases for all conditions. So, it can be inferred that the ESW process can be an important alternative for overlaid Inconel 625 weld layers, because adequate results were achieved even only 1.0 mm from the fusion line. This may offer a useful cost reduction because the welding layer is thinner., SCOPUS: ar.j, DecretOANoAutActif, info:eu-repo/semantics/published

Duplex stainless steels (DSSs) are corrosion-resistant alloys extensively used in aggressive environments. Cast DSSs may be selected for pipes, valves and pumps in chemical, petrochemical and nuclear industries. The grade steel ASTM A890 1B is an example of cast DSS with 2.7-3.3%Cu addition. Copper increases the resistance to many types of corrosion, especially in non-oxidizing environments. When the copper content is higher than 2%, the steel can be precipitation-hardened. In this work, the precipitation hardening of a DSS ASTM A890 1B steel with 3.0%Cu was studied and modeled for aging temperatures in the 450-600 °C range. Copper precipitates in the ferrite phase, but remains in solid solution in the austenite. The age hardening curves were modeled by ΔH = K(t) n model, where ΔH is the increase in hardness, t is the aging time, and K and n are constants to be determined. The microstructure and substructure were investigated by scanning electron and transmission electron microscopes., SCOPUS: ar.j, info:eu-repo/semantics/published

A low Young's modulus is required for titanium alloys used in orthopedic implants, such as hip prosthetic stems, in order to avoid stress shielding due to a large difference in Young's modulus between the prosthetic stem and the cortical bone. The low Young's modulus has been observed to occur in metastable β-Ti alloys by precipitation of a stress-induced α″ martensite during cold deformation. Under this context, the Influence of thermo-mechanical processing on the microstructure and mechanical properties of the metastable β Ti–29Nb–2Mo–6Zr alloy was studied as well as the influence of the degree of deformation by cold rolling with subsequent annealing after homogenization heat treatment. The alloy presents a β microstructure after solution heat treatment at 1000 °C for 24h, followed by water quenching, while posterior cold rolling induces the precipitation of α” martensite. Young's modulus decreases and hardness increases with the degree of deformation. The annealed samples showed higher hardness and Young's modulus than the cold rolled samples. A thickness reduction of 90% maximizes the hardness/Young's modulus ratio and optimizes the required mechanical properties for orthopedic implants. The results indicate that the alloy is a promising alternative for the widely used Ti–6Al–4V., SCOPUS: ar.j, info:eu-repo/semantics/published

The nickel-based superalloy 718 after processing through three thermomechanical routes, i.e. forged, hot rolled, and cold rolled, was investigated considering its δ-phase (Ni3Nb-DOa) intergranular precipitation. The samples were subjected to different combinations of annealing and aging heat treatments to obtain different grain boundary character distribution (GBCD) as well as different δ-phase volume fractions and morphologies. While δ-phase precipitation can be beneficial to avoid grain growth during recrystallization, an increase in volume fraction can be detrimental in several aspects. Deliberate manipulation of GBCD through thermomechanical processing was found to be a key to improving Ni-based superalloy properties. The present study quantified δ-phase occurrences along the GBs based on electron backscattering diffraction analysis to identify preferential precipitation sites in consonance with GB misorientation angles. The results show that random high-angle boundaries with ε > 29 are more populated with δ-phase than low coincidence site lattices (CSL), ε < 29, special boundaries, focusing specifically on ε3n class of boundaries. Nonspecial triple junctions (0- and 1-CSL) are also preferential nucleation sites when compared to 2- or 3-CSL triple junctions., SCOPUS: ar.j, info:eu-repo/semantics/published

The corrosion resistance of the nickel-based alloy 718 in chloride environment depends on its microstructure and the influence of the different phases is still uncertain in the literature. In this study, the effect of heat treatments on the corrosion behaviour of alloy 718 in aerated 25% NaCl solution at room temperature was investigated, using chronoamperometric method applying 1.3 V anodic potential. The alloy was solubilized and aged in different conditions in order to obtain different grain sizes and δ phase volume fractions. The microstructure and the surface of the samples were characterized using scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy. The microstructure was also observed by transmission electron microscopy. This work showed that the presence of a passive Al-rich oxide film at the surface increases the pitting corrosion resistance of alloy 718 after aging heat treatment. This Al-rich oxide layer results from the dissolution of γ’ precipitates formed during aging., SCOPUS: ar.j, DecretOANoAutActif, info:eu-repo/semantics/published

The manifestation of dynamic strain aging (DSA) in Inconel 718 is reported in this work. Analysis were performed in the material with different microstructures resulting from solution anneal and aging treatment. Tensile tests were made under secondary vacuum with temperature ranging between 200 and 950°C and strain rates of 3.2 x 10-3 to 3.2 x 10-5 s-1. Results showed the range of DSA occurrence. Analysis indicates that at lower temperatures, from approximately 200 to 450°C, serrations are controlled by the diffusion of carbon. At higher temperatures, until 800°C, DSA coincided with the occurrence of other thermally activated phenomena: dynamic precipitation, especially γ’’, and Oxidation Assisted Intergranular Cracking (OAIC). It was observed that competitive phenomena affect DSA manifestation directly due to the availability of niobium in solid solution., SCOPUS: cp.k, info:eu-repo/semantics/published

Dilution is an event that has a great influence on the microstructure and, consequently, in the properties of weld claddings. The present study evaluated the effect of dilution level on the microstructure of the fusion zone of alloy Inconel 686 weld claddings. The claddings were welded by the TIG cold wire feed process. The dilution was calculated from the geometric characteristics and based on chemical composition of the materials obtained by energy dispersive X-ray spectroscopy and optical emission spectroscopy. The microstructures of all claddings were composed by a γ-FCC matrix with some minor precipitates. These particles are called in the literature topologically close-packed phases (TCP). These precipitates assumed several morphological aspects, being the shapeless morphology observed in more frequency in all claddings evaluated, independent of dilution level. A phase with lamellar morphology, with growth establishing an orientation relationship with the γ-FCC matrix solidification direction, was observed only in claddings with a low dilution level. In addition, a shapeless phase with a fine precipitation aggregated was observed in claddings with a high dilution level., SCOPUS: ar.j, info:eu-repo/semantics/published

The antibacterial activity of various nanoparticles is gaining increasing interest due to its potential medical applications. In this work, we presented the synthesis of copper oxide nanoparticles prepared by chemical reduction from aqueous solutions of copper sulfate (CuSO4) with sodium borohydride (NaBH4) and hydrazine hydrate (N2H4) as reductant and polyvinylpyrrolidone (PVP) as stabilizer. The X-ray diffraction spectra showed the formation of tenorite (CuO) and cuprite (Cu2O) nanoparticles when different ratios of CuSO4/NaBH4 and CuSO4/N2H4 were used. Photographs obtained by transmission electron microscopy (TEM) showed agglomerates of grains with a narrow size distribution (from 20 to 70 nm), whereas the radii of the individual particles were between 2 and 20 nm. Smaller nanoparticles and narrower particle size distributions were obtained when NaBH4 was used. The results of antibacterial activity using the Kirby-Bauer method showed that nanoparticles obtained with NaBH4 presented a reasonable bactericidal activity. Pseudomonas aureginosa and Staphylococcus aureus were more susceptible to the particle size than Escherichia coli. In addition, with small amounts of Cu2O in samples of CuO nanoparticles, the antibacterial susceptibility against Pseudomonas aureginosa was improved. Finally, nanoparticles of CuO incorporated into cotton by applying ultrasound waves remained impregnated after five washes., SCOPUS: ar.j, info:eu-repo/semantics/published

Metastable β-type Ti alloys with non-toxic addition elements such as Mo, Zr, Sn, Ta and Nb were developed as an alternative to the widely used Ti-6Al-4V alloy for biomedical applications. These alloys possess enhanced biocompatibility and reduced elastic modulus in comparison with Ti-6Al4V. Moreover, for orthopedic implants, low Young's modulus is required in order to avoid the stress shielding phenomenon. This study analyzes the microstructure and mechanical properties of a new Ti-12Mo-8Nb alloy after hot swaging, annealing at 950 ºC for 1h and water quenching. The alloy was characterized by X-ray diffraction, optical microscopy and transmission electron microscopy. Tensile tests were performed at room temperature. Young's modulus and hardness values were also measured. The structural characterization reveals a metastable β structure containing only a small amount of α and ω phases. Exhibiting a lower Young's modulus than Ti-6Al-4V and other previously studied Ti-Mo-Nb alloys, the Ti-12Mo-8Nb alloy can be a promising alternative for orthopedic application., SCOPUS: cp.j, info:eu-repo/semantics/published

A comparative study of the reduction of aqueous silver (Ag) and gold (Au) salts to colloidal Ag and Au nanoparticles, respectively, by a gaseous, cathodic, atmospheric-pressure microplasma electrode is presented. The resulting nanoparticles (NPs) were characterized by ultraviolet-visible (UV-vis) absorption spectroscopy and transmission electron microscopy (TEM), and the aqueous solution composition before and after experiments was determined by ionic conductivity, electrochemical potential, and/or UV-vis absorption measurements. TEM showed that Ag and Au NPs were spherical and non-agglomerated when synthesized in the presence of a stabilizer, polyvinyl alcohol. The charge injected by the plasma was correlated to the maximum intensity in the absorbance spectra which in turn depends on the nanoparticle concentration. Separately, the charge injected was correlated to the metal cation concentration. Ag and Au reduction rates were found to be directly proportional to the charge injected, independent of plasma current and process time. Differences in the mechanism for Ag and Au reduction were also observed, and solution species generated by the plasma and their role in the reduction process (e.g. H2O2, electrons) is discussed., SCOPUS: ar.j, info:eu-repo/semantics/published

The dilution is an event that have a high influence on the microstructure and, consequently, in the properties of weld claddings. The present study evaluated the effect of dilution level on the microstructure of the fusion zone of alloy Inconel 686 weld claddings. The claddings were welded by the TIG cold wire feed process. The dilution was calculated from the geometric characteristics and based on chemical composition of the materials obtained by energy dispersive X-ray spectroscopy and optical emission spectroscopy. The microstructure of all claddings were composed by a γ-FCC matrix with some minor precipitates. These particles are called in literature as topologically closed-packed phases (TCP). These precipitates assumed several morphological aspects, being the shapeless morphology observed in more frequency in all claddings evaluated, independent of dilution level. A phase with lamellar morphology, which growth establishing an orientation relationship with the γ-FCC matrix solidification direction, was observed only in claddings with a low dilution level. In addition, a shapeless phase with a fine precipitation aggregated was observed in claddings with a high dilution level., SCOPUS: ar.j, info:eu-repo/semantics/published