Examinando por Materia "Atomic force microscopy"
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Ítem Comparative studies of the feed gas composition effects on the characteristics of DLC films deposited by magnetron sputtering(ELSEVIER SCIENCE SA, 2004-07-01) Libardi, J.; Grigorov, K.; Massi, M.; Otani, C.; Ravagnani, S.P.; Maciel, H.S.; Guerino, M.; Ocampo, J.M.J.; Libardi, J.; Grigorov, K.; Massi, M.; Otani, C.; Ravagnani, S.P.; Maciel, H.S.; Guerino, M.; Ocampo, J.M.J.; Universidad EAFIT. Departamento de Ciencias; Electromagnetismo Aplicado (Gema)Mixtures of acetylene/argon and methane/argon with different volume percents of hydrocarbon were used as the precursor gas to grow DLC films, keeping constant the other process parameters. The substrates used were p-type (100) silicon wafers. The films were characterized by Raman spectroscopy, nanoindentation, atomic force microscopy (AFM) and by a profilometer. In order to grow DLC films with special properties that could make this material an alternative candidate for applications in micro-electromechanical systems (MEMS) production, a comparative analysis focused on the influence of the hydrocarbon precursor gas mixture on the mechanical and chemical properties of the DLC films is reported. © 2004 Elsevier B.V. All rights reserved.Ítem Envejecimiento termo-oxidativo de asfaltos(Universidad EAFIT, 2014) Gamarra Escamilla, AdrianaÍtem Growth of magnetite films by a hydrogel method(Elsevier B.V., 2017-06-15) Velásquez, A.A.; Marín, C.C.; Urquijo, J.P.; Universidad EAFIT. Departamento de Ciencias Básicas; Electromagnetismo Aplicado (Gema)Magnetite (Fe3O4) films were grown on glass substrates by formation and condensation of complex of iron oxides in an agarose hydrogel. The obtained films were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Room Temperature Mössbauer Spectroscopy (TMS), Vibrating Sample Magnetometry (VSM), Atomic Force Microscopy (AFM) and Voltage vs. Current measurements by the four-point method. FTIR and TGA measurements showed that some polymer chains of agarose remain linked to the surface of the magnetic particles of the films after heat treatment. SEM measurements showed that the films are composed by quasi spherical particles with sizes around 55 nm. Mössbauer spectroscopy measurements showed two sextets with broaden lines, which were assigned to magnetite with a distributed particle size, and two doublets, which were assigned to superparamagnetic phases of magnetite. For the specific dimensions of the films prepared, measurements of Voltage vs. Current showed an ohmic behavior for currents between 0 and 200 nA, with a resistance of 355 kO. © 2017 Elsevier B.V.Ítem Obtención de estructuras de relieve en materiales de registro de haluros de plata(Sedoptica, 2013-09-19) Velásquez Prieto, Daniel; Giraldo Castaño, Lady Marcela; Velásquez Prieto, Daniel; Giraldo Castaño, Lady Marcela; Universidad EAFIT. Departamento de Ciencias Básicas; lmgc15@gmail.com; Óptica AplicadaDiffraction transmission gratings were recorded in AGFA-8E75 film, chemically treated under processes with D-19 + potassium ferrocyanide and a chemical processing technique proposed for PE-2 film to obtain embossed stripes. Holographic structures were measured topographically by the technique of atomic force microscopy in noncontact mode (NC-AFM) and we observe changes in the depths under variations in exposures and used photochemistry. We find that the best performance in terms of relief depth obtained is given by the conventional process which reached depths between 0.15 m and 0.3 m for spatial frequencies of the order of 400Ítem Síntesis de películas delgadas por la técnica de magnetrón Sputtering a partir de blancos de Renio y Boro(Universidad EAFIT, 2017) Angarita Gutiérrez, Luis Guillermo; Palacio Espinosa, Claudia ConstanzaEn esta investigación se propuso la síntesis de recubrimientos de Renio y Boro por la técnica de co-deposición en magnetrón sputtering, para lo cual se utilizó un blanco de Renio de 99.99 % de pureza pulverizado con una fuente DC y dos blancos de Boro al 99.99 % de pureza pulverizados con una fuente RF -- Se produjeron 10 muestras que fueron elaboradas siguiendo un diseño de experimentos tipo factorial completo 23, con 2 experimentos adicionales donde se modificaron las potencias de trabajo, la temperatura de los sustratos y se realizó un tratamiento térmico a 600 ºC, dejando constantes los demás parámetros -- Las propiedades morfológicas de los recubrimientos fueron caracterizadas mediante Microscopía de Fuerza Atómica (MFA) y Microscopía Electrónica de Barrido (MEB), con el fin de identificar las características microestructurales de cada recubrimiento -- La composición química se determinó utilizando Espectroscopía de Energía Dispersiva (EDS) encontrándose una gran cantidad de Renio y Oxígeno en los recubrimientos -- Las propiedades estructurales se evaluaron mediante Difracción de Rayos X (DRX), Microscopía Electrónica de Transmisión (MET) y microRaman -- Los análisis realizados a partir de estos resultados evidenciaron que el Renio y el Boro no reaccionaron para formar fases cristalinas del sistema Re-B, pero por su parte se logró la formación preferencial de la fase cristalina denominada ácido rénico monohidratado (ReH3O5) para la cual, reporta la literatura, existe un marcado interés en procesos de catálisis, especialmente en la hidrogenación de aldehídos, ácidos carboxílicos y de carboxamidasÍtem Synthesis of Alumina Thin Films Using Reactive Magnetron Sputtering Method(IOP PUBLISHING LTD, 2017-06-13) Angarita G.; Palacio C.; Trujillo M.; Arroyave M.; Angarita G.; Palacio C.; Trujillo M.; Arroyave M.; Universidad EAFIT. Departamento de Ciencias; Electromagnetismo Aplicado (Gema)Alumina (Al2O3) thin films were deposited on Si (100) by Magnetron Sputtering in reactive conditions between an aluminium target and oxygen 99.99% pure. The plasma was formed employing Argon with an R.F power of 100 W, the dwelling time was 3 hours. 4 samples were produced with temperatures between 350 and 400 °C in the substrate by using an oxygen flow of 2 and 8 sccm, the remaining parameters of the process were fixed. The coatings and substrates were characterized using Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Energy Dispersive Spectroscopy (EDS) in order to compare their properties before and after deposition. The films thicknesses were between 47 and 70 nm. The results show that at high oxygen flow the alumina structure prevails in the coatings while at lower oxygen flow only aluminum is deposited in the coatings. It was shown that the temperature increases grain size and roughness while decreasing the thicknesses of the coatings. © Published under licence by IOP Publishing Ltd.Ítem Thermo-oxidative aging of bitumen(Taylor and Francis Ltd., 2018-07-03) Gamarra, A.; Ossa, E.A.; Gamarra, A.; Ossa, E.A.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaThermo-oxidative bitumen ageing has been commonly recognised as the main cause of asphalt cracking. The effect of thermo-oxidative ageing level on bitumen has been studied in this work by means of a simple and effective mechanical stirring process. Physical characteristics of the material as Softening Point, Penetration and Viscosity were measured to samples with different ageing conditions. Chemical changes in the material were evaluated by means of SARA fractioning to measure the effect of ageing on the fundamental components of bitumen, and Infrared Spectroscopy in order to study the changes found on the oxidation-related compounds of the material. Microstructural changes on the material were evaluated using atomic force microscopy (AFM) finding that the ageing process on bitumen increases the number and size of the phases related to asphaltenes and resins, and decreases the amount of phases related to aromatics. The changes in chemical and physical characteristics of bitumen were found to be strongly dependent on the carbonyl formation. An extension to a previously proposed oxidation kinetics model was used to predict the fast rate (transient) and constant rate (steady-state) oxidation behaviour of bitumen and its relation to physical properties. The thermo-oxidative changes suffered by bitumen are associated with increasing hardening of the material, making it susceptible to cracking when in contact with aggregate as thin films in flexible pavements. © 2016 Informa UK Limited, trading as Taylor & Francis Group.