Cintia L.G. Amorim

Antimony desinsertion reaction from SbxCoSb3−x

The compound Sbx CoSb3-x was produced at 7.7 GPa and 550 ∘C in a self-insertion reaction from the binary skutterudite CoSb3. This self-insertion reaction is characterized by the collapse of some framework Sb atoms into the cages formed by the Co and Sb atoms in the skutterudite structure, as was further confirmed by Bader’s analysis of maximum-entropy charge density maps obtained from synchrotron radiation x-ray powder diffraction data. The opposite reaction (i.e., Sb desinsertion, Sbx CoSb3-x→CoSb3) occurs when Sbx CoSb3-x is heated above 180 ∘C at ambient pressure. This desinsertion reaction was followed by means of differential scanning calorimetry, x-ray diffraction, and electrical resistivity measurements. Differential scanning calorimetry measurements revealed the presence of two thermal events in samples rich in the Sbx CoSb3-x phase. An endothermic peak around 150 ∘C was assigned to a small change in the position of the guest Sb atoms inside the cages of Sbx CoSb3-x. This assignment was based on t...

SÍNTESE E CARACTERIZAÇÃO DE FILMES FINOS DE ZrN DEPOSITADOS EM DIFERENTES TEMPERATURAS

Zirconium nitride (ZrN) nanometric films were deposited onto different substrates, in order to study the surface crystalline microstructure and also to investigate the electrochemical behavior to obtain a better composition that minimizes corrosion reactions. The coatings were produced by physical vapor deposition (PVD). The influence of the nitrogen partial pressure, deposition time and temperature over the surface properties is studied. Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) techniques and corrosion experiments were performed to characterize the ZrN hard coatings. As expected, the ZrN films properties and microstructure changes according to the deposition parameters. The corrosion resistance increases with the temperature used in the films deposition. Corrosion tests show that ZrN coatings deposited by PVD onto titanium substrate can improve the corrosion resistance.