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Corrosion resistance of ZrNxOy thin films obtained by rf reactive magnetron sputtering

Ariza, E.; Rocha, L. A.; Vaz, F.; Cunha, L.; Ferreira, S. C.; Carvalho, P.; Rebouta, L.; Alves, E.; Goudeau, Ph.; Rivière, J. P.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2004 ENG
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66.94%
The main aim of this work is the investigation of the corrosion resistance of single layered zirconium oxynitride, ZrNxOy, thin films in artificial sweat solution at ambient emperature. The films were produced by rf reactive magnetron sputtering, using a pure Zr target at a constant temperature of 300 8C. Two different sets of samples were produced. In the first set of films, the substrate bias voltage was the main variable, whereas in the second set, the flow rate of reactive gases (oxygen/nitrogen ratio) was varied. The control of the amount of oxygen allowed the film properties to be tailored from those of covalent zirconium nitride to those of the correspondent ionic oxide. The corrosion behaviour was evaluated by potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) tests. The analysis of EIS data provided detailed information of the corrosion processes occurring at the surface of the system throughout the immersion time. The modifications of the coating microstructure and/or chemical composition induced by the variation of the deposition parameters were also evaluated and correlated with the corrosion mechanisms occurring in each system.

Corrosion of TiN, (TiAl)N and CrN hard coatings produced by magnetron sputtering

Cunha, L.; Andritschky, M.; Rebouta, L.; Silva, R. A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 01/04/1998 ENG
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66.94%
Metallic components like moulds, dies and machinery can be subjected to intensive degradation during plastic transformation processes, namely when working with fibre filler materials and plastics which release F, S or Cl during transformation. The degradation is attributed to the combined erosive and abrasive wear by the filler material and corrosive attack of agents. This degradation reduces the lifetime of the components considerably and has a direct impact on process productivity and surface finish of the final products. Nitride-based hard coatings like TiN, (TiAl)N, BN, etc. have proved their capability to increase tool lifetime when exposed to abrasive and corrosive environments found in plastic transformation processes halogenated polymers, acrylics, polyesters, fibre reinforced plastics, etc.. Within the frame of this work we produced TiN, (TiAl)N, CrN hard coatings, with and without a metallic interlayer, by dc and rf reactive magnetron sputtering, with a thickness of about 2 μm. The aqueous corrosion behaviour of the coatings was studied in saline and acidic environments by potentiodynamic and open circuit potential (OCP) measurements. The oxidation resistance during annealing in air was also studied. In saline NaCl 9% and acid HCl 3.4%environments we found that a metallic interlayer of Ti or Cr in the case of TiN– TiAl N-coated samples and CrN-coated samples...

Electrical properties of AlNxOy thin films prepared by reactive magnetron sputtering

Borges, Joel; Martin, N.; Barradas, Nuno P.; Alves, E.; Eyidi, D.; Beaufort, Marie France; Riviere, J. P.; Vaz, F.; Marques, L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /06/2012 ENG
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66.94%
Direct current magnetron sputtering was used to produce AlNxOy thin films, using an aluminum target, argon and a mixture of N2+O2 (17:3) as reactive gases. The partial pressure of the reactive gas mixture was increased, maintaining the discharge current constant. Within the two identified regimes of the target (metallic and compound), four different tendencies for the deposition rate were found and a morphological evolution from columnar towards cauliflower-type, ending up as dense and featureless-type films. The structure was found to be Al-type (face centered cubic) and the structural characterization carried out by X-ray 2 diffraction and transmission electron microscopy suggested the formation of an aluminumbased polycrystalline phase dispersed in an amorphous aluminum oxide/nitride (or oxynitride) matrix. This type of structure, composition, morphology and grain size, were found to be strongly correlated with the electrical response of the films, which showed a gradual transition between metallic-like responses towards semiconducting and even insulating-type behaviors. A group of films with high aluminum content revealed a sharp decrease of the temperature coefficient of resistance (TCR) as the concentration ratio of non-metallic/aluminum atomic ratio increased. Another group of samples...

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
67.09%
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.