Documento de conferencia (Gema)

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https://hdl.handle.net/10784/2868

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Examinando Documento de conferencia (Gema) por Autor "Jaramillo Raquejo D."

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    Characterization of the corrosion products of one of the pedestrian paths of the bridge "punto Cero" in the city of Medellin, Colombia
    (IOP PUBLISHING LTD, 2019-01-01) Velásquez A.A.; Jaramillo Raquejo D.; Velásquez A.A.; Jaramillo Raquejo D.; Universidad EAFIT. Departamento de Ciencias; Electromagnetismo Aplicado (Gema)
    In this work, we present the structural and magnetic characterization of the rust products formed on one of the pedestrian paths of the bridge "Punto Cero" of the city of Medellin, Colombia. The rust products were obtained by scraping three zones of the surface of the pedestrian path, namely: a surface that faces the sky, a surface that faces the floor of the path and a surface with a crack, where a high corrosion state was observed. The rusts were characterized by X-ray Diffraction, Fourier Transform Infrared Spectroscopy, room temperature Mössbauer Spectroscopy and Vibrating Sample Magnetometry. The analyses made by these techniques show that the rust products formed on the surfaces facing the sky and floor are composed mainly by goethite, lepidocrocite and maghemite, in percentages of 74%, 24% and 2% respectively, while the rust taken from the more corroded substrate presented 55% of goethite, 28% of lepidocrocite and 17% maghemite. Mössbauer and X-ray measurements were highly consistent with the percentages of each phase found in all rusts. The results suggest that in addition to the type of steel and the atmospheric conditions which the structure is exposed, the specific location of some surfaces plays an important role in the type and percentage of phase formed on them, being higher the presence of spinel phase in the zones more prone to moisture accumulation. On the other hand, the formation of maghemite could be an indication of an important state of corrosion of some surfaces, which could serve as a guide to start preventive maintenance actions on the structure. © Published under licence by IOP Publishing Ltd.
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    Comparison of TiO2 targets manufactured by APS and sintering processes for PAPVD coatings suitable in technological and medical applications
    (ASM International, 2018-01-01) Jaramillo Raquejo D.; Palacio C.C.; Ageorges H.; Jaramillo Raquejo D.; Palacio C.C.; Ageorges H.; Universidad EAFIT. Departamento de Ciencias; Electromagnetismo Aplicado (Gema)
    In surface science of functional oxides, Titanium dioxide (TiO2) is one of the most investigated crystalline systems either in rutile or anatase phases. Rutile phase is widely used in microelectronic, tribological applications and in the conversion of solar energy. Anatase phase is used in self-cleaning, antifogging, photo-catalytic and biomedical technologies. This work focuses on studying the required process conditions to obtain TiO2 targets by APS onto metallic substrates using commercial TiO2 powders (Oerlikon Metco in Switzerland) with suitable physical and chemical properties for technological and medical applications as PAPVD coatings. APS targets were compared to sintered ones. The raw powders were characterized by laser diffraction, SEM, XRF and XRD while the characteristics of the APS-deposited targets as well as the sintered ones were determined by SEM and XRD to identify the constituent phases. This work allowed confirming the advantages and limitations of both processes in terms of grain size, chemical composition, microstructural homogeneity and density in order to choose the best option to manufacture targets for PAPVD coatings for technological and medical applications. © 2018 ASM International® All rights reserved.
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    Study of APS and conventional sintering parameters for the manufacture of TiO2 targets for PAPVD
    (IOP PUBLISHING LTD, 2019-01-01) Jaramillo Raquejo D.; Palacio C.C.; Ageorges H.; Jaramillo Raquejo D.; Palacio C.C.; Ageorges H.; Universidad EAFIT. Departamento de Ciencias; Electromagnetismo Aplicado (Gema)
    In surface science of functional oxides, titanium dioxide (TiO2) is one of the most investigated crystalline systems either in rutile or anatase phases. In this work commercial TiO2 powders are used to study the required process conditions to obtain TiO2 targets by Atmospheric Plasma Spray (APS) and conventional sintering, with suitable physical and chemical properties to be source material for Plasma Assisted Physical Vapor Deposition (PAPVD) for technological and medical applications. Two three factor Box Behnken experimental designs combined with surface modeling were employed to estimate the influence of spraying parameters (gun current, Ar/H2 ratio and standoff distance) and sintering parameters (heating rate, sintering temperature and holding time) within the targets microstructure (cracks and pores in cross section) and phases composition. The microstructure and composition of APS-deposited targets and sintered ones were characterized by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The lowest defects percentages of the targets manufactured in this work were 0.41 ± 0.30 % for APS-deposited targets and 0.05 ± 0.04 % for the sintered ones using the optimal parameters suggested by the statistical model, which allowed confirming the advantages of sintering process and limitations of APS in terms of microstructural homogeneity, but also of the use of design of experiments in the modeling of systems of many variables when there is not diagnostic equipment of the processes available. © Published under licence by IOP Publishing Ltd.