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Item Crystalline structure, morphology, and adherence of thick TiO2 films grown on 304 and 316L stainless steels by atomic layer deposition(MDPI) Marques, Vagner Eduardo Caetano; Manfroi, Lucas Augusto; Vieira, Angela Aparecida; Pereira, André Luis de Jesús; Marques, Francisco das Chagas; Vieira, LúciaTitanium dioxide (TiO2) thin films are widely used in transparent optoelectronic devices due to their excellent properties, as well as in photocatalysis, cosmetics, and many other biomedical applications. In this work, TiO2 thin films were deposited onto AISI 304 and AISI 316L stainless steel substrates by atomic layer deposition, followed by comparative evaluation of the mixture of anatase and rutile phase by X-ray diffraction, Raman maps, morphology by SEM-FEG-AFM, and adhesion of the films on the two substrates, aiming to evaluate the scratch resistance. Raman spectroscopy mapping and X-ray diffraction with Rietveld refinement showed that the films were composed of anatase and rutile phases, in different percentages. Scratch testing using a diamond tip on the TiO2 film was employed to evaluate the film adherence and to determine the friction coefficient, with the results showing satisfactory adherence of the films on both substrates.Item Sputtering of micro-carbon-silver film (μC-Ag) for endotracheal tubes to mitigate respiratory infections(IOP science) Silva, Michely Glenda Pereira da; Manfroi, Lucas Augusto; Lobo, Larissa Zamboni; Vieira, Angela Aparecida; Macário, Paulo Fabrício; Fukumasu, Newton Kiyoshi; Silva, Newton Soares da; Tschiptschin, André Paulo; Marques, Francisco das Chagas; Vieira, LuciaPolyurethane (PU) substrates are biocompatible materials widely used to manufacture endotracheal tubes. However, in common with other biomedical materials, they are liable to the formation of microbial films. The occurrence of pneumonia in intubated patients treated at intensive care units often takes the form of ventilator-associated pneumonia (VAP). The issue relates to the translocation of pathogenic microorganisms that colonize the oropharyngeal mucosa, dental plaque, stomach, and sinuses. New protective materials can provide a more effective therapeutic approach to mitigating bacterial films. This work concerns microcrystalline carbon film containing dispersed silver nanoparticles (μC-Ag) deposited on PU substrates using a physical vapor deposition sputtering process. For the first time, carbon paper was used to produce a carbon target with holes exposing a silver disk positioned under the carbon paper, forming a single target for use in the sputtering system. The silver nanoparticles were well distributed in the carbon film. The adherence characteristics of the μC-Ag film were evaluated using a tape test technique, and electron dispersive x-ray mapping was performed to analyze the residual particles after the tape test. The microbicidal effect of the thin film was also investigated using species S. aureus, a pathogenic microorganism responsible for most infections of the lower respiratory tract involving VAP and ventilator-associated tracheobronchitis (VAT). The results demonstrated that μC-Ag films on PU substrates are promising materials for mitigating pathogenic microorganisms on endotracheal tubes.Item Enhancing UV Radiation Resilience of DLC-Coated Stainless Steel with TiO2: A Dual-Layer Approach(MDPI) Macário, Paulo Fabrício; Silveira, Carolina Hahn da; Vieira, Angela Aparecida Moraes; Marcondes, André Ricardo; Marques, Francisco das Chagas; Fechine, Guilhermino José Macêdo; Vieira, LuciaThis study presents an innovative dual-layer coating approach integrating titanium dioxide (TiO2) onto diamond-like carbon (DLC)-coated 316L stainless steel. The combination of PECVD- deposited DLC and ALD-deposited TiO2 aims to preserve the inherent tribological properties of DLC while mitigating UV-induced degradation. By leveraging the ability of TiO2 to absorb, reflect, and scatter UV light, this dual-layer strategy significantly enhances the durability of DLC coatings in radiation-prone environments. The effects of accelerated aging through UV exposure on DLC and DLC/TiO2 films were evaluated using an Accelerated Weathering Tester. Comprehensive analyses were conducted to assess the structural and mechanical properties before and after UV exposure, including Raman spectroscopy, profilometry, SEM, EDS, nanoindentation, and tribometry. The results demonstrate that the TiO2 layer effectively mitigates UV-induced damage, preserving the DLC film’s integrity and tribological performance even after 408 h of UV aging. Specifically, the DLC/TiO2 coatings maintained lower roughness, higher hardness, and better adhesion than DLC- only coatings under identical conditions. This research significantly advances protective coating technology by enhancing the durability and performance of DLC films, particularly in aerospace and other demanding industries where exposure to UV radiation is a critical concern.Item In-situ transmission electron microscopy (TEM) investigation of the reduction process in graphene oxide(Springer Nature Link) Silva, Douglas Soares da; Viana, Gustavo Alexandre; Silva Filho, José Maria Clemente da; Kretly, Luiz Carlos; Chaves Neto, Antônio Maia de Jesus; Vieira, Lúcia; Barros, Tárcio André dos Santos; Marques, Francisco das ChagasThe reduction processes of graphene oxide (GO) aim to remove functional groups such as H2O, CO, and CO2 to promote the properties of GO towards those of pure graphene. We adopted the thermal reduction process from room temperature to 320 °C. The transmission electron microscopy (TEM) technique was used to probe the effect of reduction mechanisms. It was observed that the plasmon peaks, referring to sp2 carbon bonds in crystalline structures, are more evident in the reduced graphene oxide (rGO) than GO. The fine structure at the K edge of carbon shows differences in shape linked to the density of states above the Fermi level. Electron energy loss spectroscopy (EELS) analyses revealed an increase in the fraction of sp3 bonds in the reduced sample, consistent with the reduction of functional radicals in the GO structure.