Thin solid films of Nb2O5 and Nb2O5:Li+ were prepared by the sol-gel process using the sonocatalytic method. The films reported here were prepared from a NbCl5 as precursor and butanol as solvent. Through the addition of lithium salt LiCF3SO3 to the precursor solution, films with different electrochemical performance were obtained. The electrochemical and optical responses of the films were determined from the cyclic voltammetry and chronoamperometry measurements using a 0.1 M LiClO4/PC as electrolyte. The electrochromic properties of the films were investigated using in situ spectroelectrochemical method. They exhibit a gray coloration under Li+ insertion with a reversible variation of the transmittance in the visible and near infrared range between 20% and 80%.

Pure titanium shows very interesting characteristics such as high strength-to-weight ratio, very good corrosion resistance and excellent biocompatibility, which make this material appropriate for use in orthopedic and dental implants. Due to the mechanical properties of pure titanium, its use in implants is restricted to applications which involve moderate mechanical stress, such as dental implants. In applications where high mechanical strength is necessary, like orthopedic implants, it is appropriate to employ titanium-based alloys, which have better properties than pure titanium. The present work is related to the microstructure and corrosion resistance characterization of the Ti-6Al-7Nb alloy, designed to be used in orthopedic prostheses.

The Sn-Se eutectic solidification allows one to obtain a lamellar structure, formed by SnSe and SnSe2 compounds, which are p and n semiconducting types, respectively. The SnSe-SnSe2 eutectic composite is a promising material to be used in photovoltaic device manufacturing. In a lamellar eutectic microstructure, the main parameter, which governs many of its characteristics, is the lamellar spacing. Such a parameter is primarily a result of the undercooling at the solid/liquid interface, which depends on the growth rate and the eutectic system properties. In this work, the Sn-Se alloy corresponding to eutectic composition was studied by using DSC thermal analysis and directional solidification at several growth rates in a vertical Bridgman-Stockbarger unit. The objective of the experiments was to investigate the influence of the growth rate on the growth undercooling, as well as on the eutectic microstructure. The microstructure analysis showed that a very regular and aligned structure formed by the SnSe and SnSe2 solid phases can be produced. By using the classic eutectic growth theory developed by Jackson and Hunt, the experimental results obtained led to the evaluation of a relationship among growth rates, eutectic growth temperature and lamellar spacing.

In the growth of a binary eutectic alloy, the formation of two new solid phases results in an unusual solute segregation process. In order for growth to happen, one of the solid phases must experience a decrease in the initial melt concentration of one of the alloy constituents and an increase in the amount of the other element. An analogous phenomenon occurs with respect to the other phase. The lateral composition gradient gives rise to mass transport parallel to the growth direction and across the solid/liquid interface, which controls the liquid interfacial composition field. The presence of an electric field during solidification can change the interfacial liquid composition distribution and thereby the growth condition. In this work, the Pb-Sn eutectic alloy was directionally solidified under the influence of an electric field normal to the growth direction. The results obtained show that electrodiffusion due to the electric field can change the eutectic lamellar spacing, the lamellar growth orientation and the eutectic microstructure regularity.