Navegando por Autor "Vieira, Angela Aparecida"
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Item Anatase film on orotracheal tubes to mitigate Staphylococcus aureus(American Scientific Publishers) Manfroi, Lucas Augusto; Silva, Michely Glenda Pereira da; Vieira, Angela Aparecida; Macário, Paulo Fabrício; Silva, Newton Soares da; Marques, Francisco Chagas; Vieira, LuciaBacterial contamination in hospital environments is a significant concern for patient admissions. Aiming to reduce contamination, titanium dioxide film (TiO2) in the anatase phase has been prepared on the surface of polyvinyl chloride (PVC) tubes. The PVC tube material was used to study the film’s effectiveness in inhibit- ing bacterial growth and cell viability. The morphology and composition of deposited films were investigated using a Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) map. In addition, Fourier-Transform Infrared Spectroscopy (FTIR) and XRD diffractogram were used to analyze film composition and phase, respectively. The adhesion of TiO2 film on PVC substrate was determined using ScotchTM tape-test according to ASTM: D3359-09, 2010, and the film surface morphology was analyzed by the MEV-FEG tech- nique and EDS map. The bacterial viability was performed with Staphylococcus aureus, and cell viability was performed using L929 strain mouse fibroblasts. The results of TiO2 in the anatase phase deposited by ALD on the PVC surface demonstrate good adherence and the film’s effectiveness in inhibiting bacterial growth and cell viability.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 High-Tribological-Performance Polymer Nanocomposites: An Approach Based on the Superlubricity State of the Graphene Oxide Agglomerates(MDPI) Ferreira, Eder Henrique Coelho; Vieira, Angela Aparecida; Vieira, Lucia; Fechine, Guilhermino José MacêdoHere, nanocomposites of high-molecular-weight polyethylene (HMWPE) and HMWPE- UHMWPE (80/20 wt.%) containing a low amount of multilayer graphene oxide (mGO) (≤0.1 wt.%) were produced via twin-screw extrusion to produce materials with a higher tribological performance than UHMWPE. Due to the high viscosity of both polymers, the nanocomposites presented a signifi- cant concentration of agglomerates. However, the mechanical (tensile) and tribological (volumetric loss) performances of the nanocomposites were superior to those of UHMWPE. The morphology of the nanocomposites was investigated using differential scanning calorimetry (DSC), microtomogra- phy, and transmission electron microscopy (TEM). The explanation for these results is based on the superlubricity phenomenon of mGO agglomerates. It was also shown that the well-exfoliated mGO also contained in the nanocomposite was of fundamental importance as a mechanical reinforcement for the polymer. Even with a high concentration of agglomerates, the nanocomposites displayed tribological properties superior to UHMWPE’s (wear resistance up to 27% higher and friction co- efficient up to 57% lower). Therefore, this manuscript brings a new exception to the rule, showing that agglomerates can act in a beneficial way to the mechanical properties of polymers, as long as the superlubricity phenomenon is present in the agglomerates contained in the polymer.Item Molhabilidade de Não Tecido Eletrofiado Contendo Nanopartículas de Prata para Uso em Filtros(2023) Shimada, Yoshio Manoel Nunes; Silva, Daniele Cristina da; Bustamante, Gabriel Costa; Vieira, Angela Aparecida; Vieira, LúciaItem Molhabilidade de não tecido eletrofiado contendo nanopartículas de prata para uso em filtro(Faculdade Senai Roberto Mange) Shimada, Yoshio Manoel Nunes; Silva, Daniele Cristina; Bustamante, Gabriel Costa; Vieira, Angela Aparecida; Gonçalves, Érika Peterson; Vieira, LuciaSabe-se que hospitais podem ser ambientes endêmicos onde a coinfecção por vírus e bactérias pode ocorrer. O uso de novos materiais e métodos de processamento para fabricar filtros ou máscaras ocorrem devido à sua ampla aplicação. Para este estudo, um sistema de eletrofiação foi usado para fabricar não tecidos baseados em fibras de poliacrilonitrila (PAN), com e sem a adição de nanopartículas de prata (Ag). Após a produção, as amostras receberam um tratamento térmico em atmosfera de nitrogênio, a fim de reduzir o efeito eletrostático. Os materiais foram avaliados em termos de molhabilidade pela medição de ângulo de contato. Para a análise da morfologia das fibras, foram usadas microscopia eletrônica de varredura e transmissão. Os testes de molhabilidade mostraram que o PAN+Ag possuí características hidrofóbicas, de acordo com as recomendações para filtros de proteção pessoal sendo capaz de reter gotículas e aerossóis.Item Produção e caracterização de revestimentos à base de carbono em cerâmica e aço visando aplicações biomédicas(2021-08-06) Vieira, Lúcia; Silva, Newton Soares da; Ramirez Ramos, Marco Antonio; Radi, Polyana Alves; Martins, Gislene Valdete; Vieira, Angela Aparecida; São José dos CamposA expectativa de vida vem aumentando ao longo dos anos devido ao avanço da medicina, assim o número de idosos vem crescendo, e consequentemente vem aumentando as preocupações com as doenças relacionadas com a idade, como osteoporose, artrose, bradicardia, problemas bucais e entre outros. Dessa forma, a procura por implantes ósseos e dentários vem aumentando bem como o desenvolvimento de novos materiais para serem usados como matéria prima para novos implantes tais como: cerâmica, metais e polímeros. Porém alguns desses materiais tem um custo elevado e outros podem causar problemas a longo prazo como por exemplo, a metalose. A metalose consiste em uma degradação do material quando exposto ao fluído corpóreo e é uma das causas responsáveis por quase todas as cirurgias de substituição de prótese. Esta degradação consiste no desprendimento de íons metálicos da prótese e no acúmulo desses íons sobre os tecidos moles do corpo, levando a uma necrose do tecido ou a um crescimento tumoral. Portanto, são apresentados neste trabalho algumas considerações importantes para obtenção e caracterização de filmes e revestimentos de alótropos de carbono. Estes materiais podem ser utilizados como filme ou revestimento para a proteção de materiais implantáveis, bem como para aumentar a vida útil dos implantes. Para este estudo foram produzidos e caracterizados alótropos de carbono na forma de filmes e revestimentos de carbono. Foram produzidos filmes de DLC depositados à plasma utilizando reator “Plasma Enhanced Chemical Vapor Deposition” (PECVD) e magnetron sputtering em cerâmica MgAl2O4. Foram depositados também, revestimentos de carbono contendo fases de grafite microcristalino via laser cladding em SS316L. Foram realizadas teste biológicos, caracterização mecânica e microestrutural dos filmes obtidos. Os resultados demonstraram a formação de filme de DLC via PECVD em cerâmica com e sem prata sendo melhor probabilidade estatística do filme de DLC+Ag para aplicação biomédica. No revestimento obtido por laser cladding em amostra SS316L foi observada a formação fases de grafite microcristalino e aumento da resistência mecânica do material com o revestimento e melhor probabilidade estatística de osseointegração com a incorporação de TiO2. Com as caracterizações e teste biológico foi possível selecionar o filme e revestimento com melhor probabilidade estatística para aplicação biomédica.Item Scratch and wear behaviour of Co-Cr-Mo alloy in ringer’s lactate solution(MDPI) Silva, Raimundo; Santos, Marcos Dantas dos; Madureira, Rui; Soares, Rui; Neto, Rui; Vieira, Angela Aparecida; Gonçalves, Polyana Alves Radi; Leite, Priscila Maria Sarmeiro Corrêa Marciano; Vieira, Lúcia; Viana, FilomenaCobalt–chromium–molybdenum (Co-Cr-Mo) alloy is a material recommended for biomedical implants; however, to be suitable for this application, it should have good tribological properties, which are related to grain size. This paper investigates the tribological behaviour of a Co-Cr-Mo alloy produced using investment casting, together with electromagnetic stirring, to reduce its grain size. The samples were subjected to wear and scratch tests in simulated body fluid (Ringer’s lactate solution). Since a reduction in grain size can influence the behaviour of the material, in terms of resistance and tribological response, four samples with different grain sizes were produced for use in our investigation of the behaviour of the alloy, in which we considered the friction coefficient, wear, and scratch resistance. The experiments were performed using a tribometer, with mean values for the friction coefficient, normal load, and tangential force acquired and recorded by the software. Spheres of Ti-6Al-4V and 316L steel were used as counterface materials. In addition, to elucidate the influence of grain size on the mechanical properties of the alloy, observations were conducted via scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD). The results showed changes in the structure, with a reduction in grain size from 5.51 to 0.79 mm. Using both spheres, the best results for the friction coefficient and wear volume corresponded to the sample with the smallest grain size of 0.79 mm. The friction coefficients obtained were 0.37 and 0.45, using the Ti-6Al-4V and 316L spheres, respectively. These results confirm that the best surface finish for Co-Cr-Mo alloy used as a biomedical implant is one with a smaller grain size, since this results in a lower friction coefficient and low wear.Item Wear Rate, Tribo-Corrosion, and Plastic Deformation Values of Co-Cr-Mo Alloy in Ringer Lactate Solution(MDPI) Silva, Raimundo Nonato Alves; Neto, Rui; Vieira, Angela Aparecida; Leite, Priscila Maria Sarmeiro Corrêa Marciano; Radi, Polyana Alves; Silveira, Carolina Hahn da; Santos, Marcos Dantas dos; Viana, Filomena; Vieira, LúciaThis study investigates the tribocorrosion performance of a cast Co-Cr-Mo alloy prepared using casting and electromagnetic stirring (EMS) at specific frequencies. The tribocorrosion behaviour of the alloy was evaluated when exposed to Ringer’s lactate solution to optimize the EMS parameters and improve its properties. The research focuses on biomedical implant applications and explores how EMS affects alloy wear and corrosion resistance. As did the friction coefficient and wear volume, the wear rate of samples produced with EMS frequencies of 75 Hz and 150 Hz decreased. These improvements are attributed to the ability of EMS to refine grain size and homogenize the microstructure, thereby increasing the resistance to tribocorrosion. Techniques such as scanning electron microscopy (SEM) and profilometry were used for surface and wear analysis, while mechanical properties were evaluated through instrumented indentation tests. The findings confirm that EMS improves the alloy’s durability and tribocorrosion resistance, making it highly suitable for demanding biomedical applications such as joint replacements. This highlights the importance of advanced manufacturing techniques in optimizing biomedical alloys for simulated body conditions.