Examinando por Materia "Titanium dioxide"

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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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    Effect of CeO2 content in morphology and optoelectronic properties of TiO2-CeO2 nanoparticles in visible light organic degradation
    (ELSEVIER SCI LTD, 2019-02-01) Cano-Franco, JC; Alvarez-Lainez, M; Universidad EAFIT. Departamento de Ingeniería de Diseño; Ingeniería de Diseño (GRID)
    TiO2 is a semiconductor widely used in photocatalytic degradation of organic pollutants due to its band gap energy. However, its absorption range is restricted only to UV radiation that is less than 10% of solar light. With the aim of increasing the adsorption area on TiO2 nanoparticles a modified sol-gel method was used to produce a smaller particle size, and to extend the absorption range to the visible spectrum, TiO2 nanoparticles were synthesized with different CeO2 contents to generate semiconductor heterojunction between them. The crystallographic, morphological, and optoelectronic characteristics of these TiO2-CeO2 nanoparticles were studied, and two crystalline phases were differentiated: anatase for TiO2 and fluorite for CeO2. An increase in the CeO2 content produced crystallite sizes between 6.5 nm and 12.0 nm. TiO2-CeO2 nanoparticles showed morphological properties such as small particle size, heterogeneous surface and high BET surface area compared to bare commercial TiO2. These features involve a positive effect of CeO2 in TiO2 nanoparticles surface, thus TiO2-CeO2 nanoparticles exhibit enhanced optoelectronic properties caused by a decrease in the effective band gap and red-shift in the electromagnetic spectrum. In addition, methylene blue degradation showed that TiO2-CeO2 nanoparticles are suitable for high photocatalytic activity application under visible light. © 2018 Elsevier Ltd
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    Effect of the mechanical properties on drilling resistance of Al2O3-TiO2 coatings manufactured by atmospheric plasma spraying
    (ELSEVIER SCIENCE SA, 2013-04-15) Palacio, C. C.; Ageorges, H.; Vargas, F.; Diaz, A. F.; Universidad EAFIT. Departamento de Ciencias Básicas; Electromagnetismo Aplicado (Gema)
    Al2O3 with 13 and 45wt.% TiO2 microsized powders (6-22 and 13-41µm for each chemical composition) were used as raw materials to coat AISI 1040 steel by atmospheric plasma spraying. The mechanical properties of the coatings were measured by micro-indentation tests, and drilling experiments were carried out using high speed steel (HSS) rotary drill bits of various diameters and varying the load on the drill bits. In order to reduce the effect of the wear on the bit, a new bit was used for each test. According to the results, the drilling test is proposed as a method of determining the mechanical properties of these coatings from the correlation found between coating hardness and drilling resistance. © 2012 Elsevier B.V.
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    Foto-degradación de fenol sobre catalizadores de TiO2 y Mo/TiO2. La metodología de superficie de respuesta como herramienta de optimización
    (Centro de Informacion Tecnologica, 2014-01-01) López-Zamora, S.M.; GilPavas, E.; Gómez-García, M.Á.; Dobrosz-Gómez, I.; López-Zamora, S.M.; GilPavas, E.; Gómez-García, M.Á.; Dobrosz-Gómez, I.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)
    In this work, the response surface methodology was applied as a tool for the optimization of the operational conditions of phenol photo-degradation over TiO2 and 2% wt Mo/TiO2 catalysts. A multifactorial experimental design was proposed, including the following variables: phenol initial concentration (Ci), catalyst loading (Cat) and pH. The apparent reaction rate constant and the percentage of phenol degradation were chosen as the response variables. When TiO2 was used as catalyst, the following optimal operational conditions were found: Ci=10ppm, Cat=0.7g/L and pH=8 for both UV and visible light. For 2% wt Mo/TiO2 catalyst, the optimal operating conditions strongly depended on the applied radiation source. Thus, under UV radiation: Ci=10 ppm, Cat=0.7 g/L and pH=8 were found as the optimum conditions. Using visible light, and the following optimized conditions, Ci=10 ppm, Cat=0.1 g/L, pH =3.6, the Mo containing catalyst showed to be the most efficient. Under these conditions, the amount of 2% wt. Mo/TiO2 was 7 times lower than that of unsupported TiO2.
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    Pelletisation by tumbling as an alternative method of agglomerating nanometric particles for use as feedstock in bi-modal structured flame-sprayed ceramic coatings
    (Elsevier Ltd., 2019-01-01) Árias J.A.; Hurtado F.M.; Estrada G.; Cadavid E.; Rincón Ortiz M.; Palacio C.C.; Vargas F.; Universidad EAFIT. Departamento de Ciencias Básicas; Electromagnetismo Aplicado (Gema)
    This paper is focused on the physical evaluation of ceramic granules of Al2O3, Al2O3-13 wt% TiO2 (AT-13) and TiO2 obtained from alumina and titania nanoparticles by pelletisation in a rotating drum. The results were compared with those of both sintered and non-sintered granules of similar chemical compositions and particle size distributions which were spray dried, as well as with those of TiO2 pelletised granules blended with atomised alumina particles. The results obtained indicated that the physical characteristics of the pelletised granules conferred them a free-flowing behavior which was similar to that of the spray-dried granules. However, the TiO2 pelletised granules blended with harder atomised alumina particles disintegrated and, therefore, exhibited a poor flowability. Additionally, it was evident that the ceramic coatings fabricated from pelletised granules displayed a structure which was as or more compact than those of the granules obtained from agglomerated powders by spray drying with or without sintering, apart from being more compact than that of the coatings deposited from TiO2 pelletised granules blended with atomised alumina particles. The above findings indicate that the alternative pelletising method is potentially useful for the use of agglomerated nanoparticles as feedstock in the fabrication of bi-modal structured flame-sprayed ceramic coatings. © 2019 Elsevier Ltd and Techna Group S.r.l.
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    Solar and artificial UV inactivation of bacterial microbes by Ca-alginate immobilized TiO2 assisted by H2O2 using fluidized bed photoreactors
    (SCIENCE & TECHNOLOGY NETWORK INC, 2014-07-01) GilPavas, Edison; Acevedo, Jose; Lopez, Luis F.; Dobrosz-Gomez, Izabela; Angel Gomez-Garcia, Miguel; GilPavas, Edison; Acevedo, Jose; Lopez, Luis F.; Dobrosz-Gomez, Izabela; Angel Gomez-Garcia, Miguel; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)
    In this work, TiO2 (Degussa, P-25) supported on calcium alginate pearls was evaluated as catalyst for the photocatalytic inhibition of pathogenic microorganisms. Considering that water samples were taken directly from a natural source, a primary treatment (coagulation, sedimentation and filtration) was executed to remove solids and impurities. Photocatalytic experiments were carried out in two types of laboratory scale equipments, one using an annular UV irradiated reactor and the other a solar UV parabolic collector, both operated in the fluidized bed mode. H2O2 was included to the reactive mixture in order to enhance the photodegradation rate. The Response Surface Methodology and the Box-Behnken experimental design techniques were applied as tools for the optimization of the operational conditions of the UV water purification system. Thus, the influence of UV radiation, TiO2 dose and H2O2 concentration on the faecal and total coliform percentage degradation were statistically analysed. The following optimal operational conditions were found: UV radiation = 310 nm, TiO2 dose = 0.2 g/L and H2O2 concentration = 30 mg/L. After water treatment at optimized conditions, total microorganism growing inhibition was observed. Additional experiments allowed proving the reusability of the immobilized catalyst. © 2014 Science & Technology Network, Inc.
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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.