The aerospace industry is constantly looking for innovative materials that exhibit good mechanical and corrosion properties. The 2198-T851 (Al-Cu-Li) alloy was developed to replace the conventional Al-Cu-Mg in aircraft structures. Despite the usefulness of the 2198-T851 alloy, its performance may be affected when subjected to an aggressive medium containing chloride ions. The deposition of Nb2O5 coatings by using the reactive sputtering technique on the 2198-T851 alloy surface appears as a powerful tool to improve the corrosion resistance of this material. Recently, groundbreaking research findings have demonstrated the positive effect of Nb2O5 coatings on corrosion protection of alloy 2198-T851. However, the corrosion products originated from the 2198-T851 aluminium alloy are poorly understood. The use of Raman spectroscopy and XPS techniques may help to shed some light on the corrosion products of 2198-T851 alloy. Results demonstrated the corrosion products are mainly composed by CuCl2 x H2O, CuCl, Cu2Cl(OH)3, Al(OH)3, and AlO(OH).

Biomedical engineering has been constantly looking for the development of new materials that have bioactive surfaces and that are responsible for new bone formation, induce osteoblast differentiation and present antibacterial properties. Here, we present innovative and applied research to evaluate the influence of niobium pentoxide thin films (Nb2O5) deposited on the surface of a Ti-6Al-4V alloy via the reactive sputtering technique on antibacterial activity, on the cellular proliferation of MC3T3 cells and on biomineralization capacity. Results demonstrated the reactive sputtering technique improved the cell viability, the osteogenic performance of cells involved in the osseointegration process, the ability to delay bacterial proliferation within the first six hours of contact with S. aureus as well as the capacity to promote rapid amorphous apatite formation in vitro. These findings confirm the great potential of the Ti-6Al-4V alloy functionalized with Nb2O5 for future applications in implantable devices. properties Here NbO Nb O (Nb2O5 Ti6Al4V TiAlV Ti 6Al 4V Al V activity MCT MC T MC3T viability process S vitro Nb2O devices (Nb2O

Fatigue and corrosion-fatigue tests were performed to quantify the fatigue properties of AA2524-T3 and AA2198-T851 Al alloys. High cycle axial fatigue tests were carried out under air and salt-water fog conditions. In air, the specimens were fatigue tested at a frequency of 50 Hz, using specimens with and without preconditioning in a salt spray chamber, and for the corrosion fatigue condition, the tests took place at a frequency of 30 Hz in a salt-water fog condition. In all cases it was used a sinusoidal waveform and a stress ratio (R) of 0.1. The results indicate that the saline environment had a deleterious effect on the fatigue life of the two aluminum alloys. AA2524-T3 exhibited a better fatigue strength than AA2198-T851 when fatigue tested in air. However, considering the corrosion fatigue test in a saline fog environment an inverse behavior was observed with the AA2198-T851 exhibiting higher fatigue strength.

A indústria aeronáutica está constantemente à procura de materiais que oferecem benefícios em termos de desempenho, peso e custo. As vantagens destas ligas são a leveza, resistência à corrosão, boa condutividade térmica e eléctrica. Neste trabalho, foi investigada a resistência à corrosão de duas ligas de alumínio através de potencial de circuito aberto, polarização potenciodinâmica e ensaios de nevoeiro salino. Os resultados sugerem que a liga AA2198-T851 apresenta melhor resistência à corrosão quando comparada com a liga AA2524-T3. Consequentemente, em casos onde a corrosão é o principal parâmetro a ser considerado, a liga AA2198-T851 pode ser substituída pela liga AA2524-T3.

The aircraft industry is constantly looking for improved materials that offer benefits in terms of performance, weight and cost savings. The advantages of these alloys are lightweight, corrosion resistance, and very good thermal and electrical conductivity. In this paper, the corrosion resistance of two aluminum alloys was investigated by open circuit potential, potentiodynamic polarization and salt spray tests. The results suggest that the AA2198-T851 alloy tend to present a higher corrosion resistance when compared with the AA2524-T3 alloy. Consequently, in cases where corrosion is the main parameter to be considered, the AA2198-T851 may be a substitute for the AA2524-T3 alloy.

Os multiferróicos são materiais em que duas ou três propriedades tais como ferroeletricidade, ferromagnetismo e ferroelasticidade são observadas em uma mesma fase. Em particular, os multiferróicos magnetoelétricos representam os materiais que são simultaneamente (anti)ferromagnéticos e ferroelétricos, com ou sem ferroelasticidade. Especificamente, o sistema hematita (alfa-Fe2O3)-alumina (alfa-Al2O3) tem sido estudado, principalmente devido às suas potencialidades para aplicações em metalurgia e como catalisador na síntese de amônia. Contudo, compostos deste sistema também podem apresentar efeitos magnetoelétricos. Neste trabalho um estudo estrutural do composto (alfa-Fe2O3)0,25(alfa-Al2O 3)0,75 submetido à moagem em altas energias e tratamento térmico pós-moagem é apresentado. As amostras foram caracterizadas por difração de raios X, refinamento estrutural Rietveld e espectroscopia Mössbauer. A determinação e identificação das fases cristalográficas, parâmetros de rede e volume de celas unitárias nas amostras moída e tratada termicamente permitiu verificar as mudanças dos parâmetros, a formação de espinélios e possíveis deformações relativas advindas do processo de moagem em altas energias.

Multiferroics are materials in which two or all three of the properties, ferroelectricity, ferromagnetism, and ferroelasticity occur in the same phase. In particular, multiferroic magnetoelectrics represent the materials that are simultaneously ferromagnetic and ferroelectric, with or without ferroelasticity. Specifically, the hematite (alpha-Fe2O3)-alumina (alpha-Al2O3) system has been studied, mainly due to its potential applications in metallurgy and as catalyst of ammonia synthesis. However, compounds of this system also may present magnetoelectric effects. In this work, a structural study of the high-energy ball milled and annealed (alpha-Fe2O3 )0.25(alpha-Al2O3)0.75 compound was carefully conducted. The samples were characterized through X-ray diffraction, Rietveld structural refinement and Mössbauer spectroscopy. The determination and identification of crystallographic phases, lattice parameters and unit cell volume in as-milled and annealed samples allowed verifying structural parameters change, the spinel phase formation and possible relative deformations due to the high-energy ball milling process.