OLANDIR VERCINO CORREA
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Artigo IPEN-doc 26485 Photocatalytic activity of undoped and sulfur-doped TiO2 films grown by MOCVD for water treatment under visible light2019 - BENTO, RODRIGO T.; CORREA, OLANDIR V.; PILLIS, MARINA F.Titanium dioxide ceramic coatings have been used as catalysts in green technologies for water treatment. However, without the presence of a dopant, its photocatalytic activity is limited to the ultraviolet radiation region. The photocatalytic activity and the structural characteristics of undoped and sulfur-doped TiO2 films grown at 400 °C by metallorganic chemical vapor deposition (MOCVD) were studied. The photocatalytic behavior of the films was evaluated by methyl orange dye degradation under visible light. The results suggested the substitution of Ti4+ cations by S6+ ions into TiO2 structure of the doped samples. SO4 2− groups were observed on the surface. S-TiO2 film exhibited good photocatalytic activity under visible light irradiation, and the luminous intensity strongly influences the photocatalytic behavior of the S-TiO2 films. The results supported the idea that the sulfur-doped TiO2 films grown by MOCVD may be promising catalysts for water treatment under sunlight or visible light bulbs.Artigo IPEN-doc 26435 Effect of oxygen partial pressure on oxidation behavior of ferritic stainless steel AISI 441 at high temperatures2019 - SALGADO, MARIA de F.; CARVALHO, IURE S.; SANTOS, RAFAEL S.; PORTO, JOÃO A.S.; CORREA, OLANDIR V.; RAMANATHAN, LALGUDI V.; BRANDIM, AYRTON de S.; LINS, VANESSA F.C.In this investigation the oxidation behavior of AISI 441 stainless steel (SS) in the range from 850 °C to 950 °C was determined during 50 h in two different atmospheres: (a) synthetic air in a tubular oven; (b) argon with 1 ppm of O2 in a thermal balance. The oxidation kinetics was determined from the measured mass change as a function of oxidation time. Examination of the microstructure of the oxides and determination of their chemical composition were performed by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and glancing angle X-ray diffraction (GAXRD). Chemical analyses showed that films formed on the AISI 441 steel surface consisted mostly of chromium oxide but manganese, iron, titanium and silicon oxides were found in the oxidized layer. In synthetic air, the steel oxidation rate increased gradually as the temperature increased, but in the argon atmosphere with 1 ppm of oxygen, the highest oxidation rate was observed at 900 °C and the lowest at 950 °C.Artigo IPEN-doc 24766 Effect of silicate-based films on the corrosion behavior of the API 5L X80 pipeline steel2018 - OLIVEIRA, LEANDRO A. de; CORREA, OLANDIR V.; SANTOS, DEMETRIO J. dos; PAEZ, ALEJANDRO A.Z.; OLIVEIRA, MARA C.L. de; ANTUNES, RENATO A.The aim of this work was to investigate the effect of silicate-based films on the corrosion resistance of the API 5L X80 steel in carbonate-bicarbonate solution at room temperature. The films were electrochemically obtained by anodic and cathodic treatments and by immersion in 1.0 M sodium metasilicate solution. The corrosion behavior was evaluated using electrochemical impedance spectroscopy and potentiodynamic polarization. Film morphology was examined by scanning electron microscopy. Adhesion strength was measured by pull-off tests. The chemical composition was evaluated by X-ray photoelectron spectroscopy. The anodic film yielded the best corrosion resistance (protection efficiency 83%). The protection mechanism is discussed.