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Characterization and electrochemical behaviour of nanostructured calcium samarium manganite electrodes fabricated by RF-Magnetron Sputtering

Barrocas, B.; Sério, S.; Rovisco, A.; Nunes, Y.; Sá, A. I. Correia de; Pereira, M. I. da Silva; Jorge, M. E. Melo
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
Relevância na Pesquisa
76.1%
Ca1-xSmxMnO3(0 . x . 0.4) films were successfully fabricated on Indium Tin Oxide (ITO) coated quartzglass substrates by radio frequency magnetron sputtering technique (RF- magnetron sputtering) fromcompacted nanosized powder targets, and subsequent annealing at 800.C in air, for 6 h. X-ray diffrac-tion shows a pure typical perovskite phase for x . 0.1. Scanning electron microscopy and atomic forcemicroscopy revealed that the films surface is dense, with low roughness, depending on the Sm content, even though a few cracks were observed. Crystallite size was found to decrease with the Sm content. Theelectrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The oxide electrode fs capacitance was estimated using both techniques and the corresponding roughness factors evaluated. The values obtained from the two methods show a good agreement. A com-parison between the voltammetric data and those referred in the literature allowed finding out that theredox reaction occurring at the electrode surface involves the pair Mn4+/Mn3+. EIS measurements con-firm the voltammetric data and they also give additional information about the film porosity and the charge transfer resistance. This last parameter is associated with the oxidation and reduction of the pairMn3+/Mn4+and after normalized by the roughness factor shows an increase with samarium content.

Degradation characteristics of hydroxyapatite coatings on orthopedic TiAlV in simulated physiological media investigated by electrochemical impedance spectroscopy

Souto, R. M.; Laz, Maria M.; Reis, R. L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /10/2003 ENG
Relevância na Pesquisa
106.31%
This paper concentrates on the degradation characteristics of hydroxyapatite (HA) coatings on orthopaedic Ti-6Al-4V alloy while immersed in Ringer's salt solution, which were investigated by electrochemical impedance spectroscopy. Electrochemical impedance spectroscopy measurements were used to in situ characterize the electrochemical behavior of the passivated alloy covered with HA during aging in Ringer's solution. Comparison of the electrochemical data for the coated material with that for the uncoated metal substrate was also performed. The characteristic feature that describes the electrochemical behavior of the coated material is the coexistence of large areas of the coating itself with pores where the substrate is exposed to the aggressive media. The interpretation of results was thus performed in terms of a two-layer model of the film, in which the precipitation of hydrated oxide or phosphate compounds seals the pores left by the ceramic coating. The blocking effect due to salt precipitation inside the pores produces an enhancement of the resistance values, thus effectively diminishing the metal ion release in the system.; Collaborative Research Programme (Acción Integrada No. HP1995-0092 and HP1996-0109) between Spain and Portugal.