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  • Resumo IPEN-doc 30291
    Corrosion analyses of anodized aluminum for biomedical purposes
    2023 - PIERETTI, EURICO F.; NEVES, MAURICIO D.M.; CORREA, OLANDIR V.; ANTUNES, RENATO A.; OLIVEIRA, MARA C.L.; PILLIS, MARA C.L.
    Introduction and objective: Anodic aluminum oxide has attracted a lot of interest due to the regular arrangement of nanopores, ease of control of the nanopores diameter, large specific surface area, low cost, good thermal stability, absence of toxicity and biocompatibility. The geometric arrangement of nanopores makes it possible to use alumina as a mold for the synthesis of various nanostructures, such as nanopores, nanotubes, nanorods and nanowires that have many advantages in advanced application areas due to their unique chemical, physical, mechanical, and optical properties [1,2]. The objective of this work was to study the corrosion susceptibility of anodized aluminum samples for biomedical applications. Methodology: In the present work, the localized corrosion resistance of AA6061aluminum alloy anodized in oxalic acid solution (C2H2O4) and sulfuric acid (H2SO4) was evaluated by electrochemical techniques. Prior to the anodization stage, the samples were electrolytically polished in a solution of perchloric acid and ethanol. Results and discussion: All samples showed a protective behavior on their surfaces, higher corrosion potentials in relation to the standard reference sample and a shift towards lower values of corrosion current densities in relation to the sample without passivation treatment. These results indicate that the anodizing treatments of AA6061 aluminum surfaces in oxalic or sulfuric acid are effective in producing surfaces resistant to localized corrosion and can therefore be used to coat this type of surface, ensuring an increase in the useful life of the devices. Conclusions: The results indicated superior corrosion resistance in the anodized samples in both conditions. Therefore, it is necessary to constantly advance research on the use of nanoporous anodic alumina coatings on biomaterials surfaces.
  • Resumo IPEN-doc 30290
    Surface investigation of a laser etched metallic biomaterial
    2023 - PIERETTI, EURICO F.; NEVES, MAURICIO D.M.; CORREA, OLANDIR V.; ANTUNES, RENATO A.; OLIVEIRA, MARA C.L.; PILLIS, MARINA F.
    Introduction and objective: Surface treatments are used to improve characteristics, such as: markings, texturing and polishing. The texturizations are produced to provide roughness and, consequently, adherence in specific locations of implantable medical devices of permanent character, that is, implants of prolonged use. Sometimes this process can generate stress concentrators and regions with probability for the occurrence of failures that can lead to fracture; in addition to damaging the passive layer, favouring the initiation of various forms of corrosion [1]. This work aims to evaluate the effect of the laser beam texturing technique in metallic implants on the corrosion resistance of ASTM 316L stainless steel. Methodology: Samples were prepared from the stainless steel textured by fiber optic laser doped with ytterbium (Yb) by changing the values of the frequency of the laser pulse cadence and keeping the other parameters constant. As a comparison, samples of the biomaterial without any type of laser treatment were also evaluated. The electrochemical tests performed consisted of open circuit corrosion potential (OCP) monitoring and cyclic potentiodynamic polarization measurements, determined after hours of immersion at 37°C body temperature. The scanning vibrating electrode electrochemical technique (SVET) was used as a tool to determine the corrosion current density in 0.1M NaCl solution. Results and discussion: The results obtained revealed the highest anodic current densities in the regions engraved by the laser beam and cathodic current densities in the regions farthest from the engravings, which indicates that laser engraving, in addition to increasing the roughness of the surfaces, makes them essentially anodic, changes the passive layer, affects the distribution of corrosion current densities and decreases the resistance to localized corrosion of this biomaterial. Conclusions: The change in the laser pulse frequency values is directly related to the behaviour observed on the analysed surfaces, indicating that the laser texturing treatment affects the passive layer of the material decreasing the resistance to localized corrosion.
  • Resumo IPEN-doc 30245
    Tribological characterization of nanoporous anodized anodic alumina coatings for biomedical applications
    2023 - PIERETTI, E.F.; CORREA, O.V.; NEVES, M.D.M.; OLIVEIRA, M.C.L.; ANTUNES, R.A.; PILLIS, M.F.
  • Artigo IPEN-doc 30044
    Avaliação eletroquímica da liga Ti6Al4V produzida por manufatura aditiva
    2023 - PIERETTI, E.F.; CORREA, O.V.; SILVA, L.C.E. da; PILLIS, M.F.; RIBEIRO, M.S.; ROSSI, W. de; NEVES, M.D.M.
    O aprimoramento de propriedades de superfície é uma exigência para osbiomateriais. O objetivo deste trabalho foi investigar a resistência à corrosãode amostras da liga Ti6Al4V produzidas por manufatura aditiva, em solução deRinger, que simula os fluidos corpóreos. As amostras foram produzidas alterando-se alguns parâmetros do processo. A resistência à corrosão foi avaliadautilizando-se métodos eletroquímicos como: monitoramento de potencial decircuito aberto, medições de espectroscopia de impedância eletroquímica epolarização cíclica e análises de superfície por MEV. Algumas amostras forammais susceptíveis à corrosão, pois a alternância de parâmetros do processo defabricação produz superfícies distintas com acabamento superficialdiversificado, resultando em comportamentos diversos.
  • Artigo IPEN-doc 29950
    Tribology analysis on anodized aluminum surfaces for biomedical purposes
    2023 - PIERETTI, EURICO F.; CORREA, OLANDIR V.; NEVES, MAURICIO D.M. das; ANTUNES, RENATO A.; PILLIS, MARINA F.
  • Resumo IPEN-doc 29396
    Caracterização superficial de alumina anódica nanoporosa aplicada a revestimentos biomédicos
    2022 - PIERETTI, E.F.; CORREA, O.V.; NEVES, M.D.; ANTUNES, R.A.; PILLIS, M.F.; OLIVEIRA, M.C.
    As superfícies dos biomateriais utilizados como dispositivos médicos implantáveis e no ferramental cirúrgico devem ser adequadas à função que exercem; por este motivo a importância do estudo do acabamento superficial aumenta à medida que crescem as exigências do projeto, no que se refere ao regime de aderência entre o implante e o tecido humano adjacente e, requisitos de geometria e precisão nos implantes e nos utensílios cirúrgicos. Estes biomateriais, quando em contato com o tecido humano, estão sujeitos a falhas como desgaste, fadiga, micro movimentos, desprendimento de partículas e degradação, podendo causar hipersensibilidade, ou a necessidade de uma nova cirurgia para remoção e substituição. Consequentemente aumentam as despesas para os pacientes, convênios médicos e as instituições públicas de saúde. Óxido de alumínio anódico (OAA) tem atraído muito interesse devido ao arranjo regular de nanoporos, facilidade de controle do diâmetro dos nanoporos, grande área de superfície específica, baixo custo, boa estabilidade térmica, ausência de toxicidade e biocompatibilidade. Devido a essas características, as estruturas OAA têm sido utilizadas em aplicações como processos de filtração, biossenssores, sensores de oxigênio, catálise e fotocatálise. Além disso, o arranjo geométrico dos nanoporos torna possível utilizar a alumina como molde para a síntese de várias nanoestruturas, como nanoporos, nanotubos, nanobastões e nanofios que apresentam muitas vantagens em áreas de aplicação avançadas devido a suas propriedades químicas, físicas, mecânicas e ópticas únicas. Por isso, tornase necessário o constante avanço nas pesquisas sobre a utilização de revestimentos de alumina anódica nanoporosa sobre as superfícies dos biomateriais.
  • Resumo IPEN-doc 29395
    Avaliação da resistência à degradação do aço inoxidável AISI 316L revestido por filmes finos de TiO2
    2022 - PIERETTI, E.F.; CORREA, O.V.; PILLIS, M.F.; ANTUNES, R.A.; NEVES, M.D. das
    Os materiais metálicos utilizados na área de engenharia de biomateriais são geralmente materiais passivos e, dessa forma, estão sujeitos à corrosão localizada principalmente pela ação dos íons cloreto. Um dos tipos mais comuns de corrosão observados nestes materiais é a geração de pites. Os processos de produção envolvidos na fabricação de equipamentos para uso biomédico também afetam sua resistência à corrosão, especificamente aqueles que influenciam no acabamento de superfície. O aprimoramento de propriedades de superfície é uma exigência para os componentes metálicos utilizados em implantes e próteses. O objetivo deste trabalho foi investigar a influência películas finas de TiO2, de tamanho nanométrico, na resistência à corrosão do aço inoxidável austenítico AISI 316L, em uma solução de Ringer, que simula os fluidos corpóreos, a 25 °C . Os filmes foram depositados por CVD (deposição química em fase vapor). A resistência à corrosão foi avaliada utilizando-se métodos eletroquímicos como: monitoramento de potencial de circuito aberto (PCA), medições de espectroscopia de impedância eletroquímica (EIE) e polarização potenciodinâmica cíclica. A porosidade dos diferentes filmes também foi determinada utilizando-se um método eletroquímico. Análises de superfície e secções transversais foram realizadas por microscopia eletrônica de varredura (MEV). Os ensaios de corrosão mostraram que as amostras revestidas eram menos susceptíveis à corrosão do que as amostras sem recobrimento. Os revestimentos de TiO2 são finos, aderentes e conduzem a um comportamento mais capacitivo do filme passivo. Estes resultados sugerem que os filmes finos obtidos por este método podem ser empregados para a proteção contra a degradação deste aço inoxidável em ambientes agressivos.
  • Resumo IPEN-doc 29191
    Tribological evaluation of anodized aluminum applied to biomaterials
    2022 - PIERETTI, EURICO F.; CORREA, OLANDIR V.; BENTO, RODRIGO T.; NEVES, MAURICIO M. das; ANTUNES, RENATO A.; PILLIS, MARINA F.
    Biomaterials surfaces need to be adequate to the function they perform; for this reason, the importance of studying surface finish increases as design requirements grow, regarding geometry and precision requirements in biomedical devices. These biomaterials are subject to several types of premature failure, such as wear, fatigue, micro movements, particle detachment and degradation, which may generate the need for new interventions. Anodizing is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts. Due to good biocompatibility, regular arrangement of nanopores, ease of control of nanopore diameter, large specific surface area, low cost, good thermal stability and, absence of toxicity, anodic aluminum oxide has been studied. The geometric arrangement of nanopores makes it possible to use alumina as a mold for the synthesis of several nanostructures that have many advantages in advanced application areas due to their unique chemical, physical, mechanical and optical properties. In the present work, the tribological behavior of samples of aluminum alloy AA6061 anodized in oxalic acid solution (C2H2O4) and sulfuric acid (H2SO4) was evaluated. Prior to the anodization stage, the samples were electrolytically polished in a solution of perchloric acid and ethanol. For comparison reasons, pristine surfaces were also evaluated. The sample's surfaces finishing was analyzed by laser confocal microscopy. Atomic force microscopy was also used to evaluate samples roughness and topography. The wear tests were carried out during 10 min, solid spheres of 52-100 chrome steel, with 2 mm in diameter, were used as counter-bodies. The results indicated that the tribological behavior is influenced by the anodized layer process parameters, and the wear rate is dependent of the normal force and the roughness of each sample.
  • Resumo IPEN-doc 29190
    Electrochemical evaluation of anodized aluminum applied to biomaterials
    2022 - PIERETTI, EURICO F.; CORREA, OLANDIR V.; NEVES, MAURICIO M. das; ANTUNES, RENATO A.; PILLIS, MARINA F.
    Anodic aluminum oxide has attracted a lot of interest due to the regular arrangement of nanopores, ease of control of the nanopores diameter, large specific surface area, low cost, good thermal stability, absence of toxicity and biocompatibility. Due to these characteristics, anodic aluminum oxide structures have been used in applications such as filtration processes, biosensors, oxygen sensors, catalysis and photocatalysis. In addition, the geometric arrangement of nanopores makes it possible to use alumina as a mold for the synthesis of various nanostructures, such as nanopores, nanotubes, nanorods and nanowires that have many advantages in advanced application areas due to their unique chemical, physical, mechanical and optical properties. In the present work, the localized corrosion resistance of samples of aluminum alloy AA6061 anodized in oxalic acid solution (C2H2O4) and sulfuric acid (H2SO4) was evaluated by electrochemical techniques. Prior to the anodization stage, the samples were electrolytically polished in a solution of perchloric acid and ethanol. The results indicated superior corrosion resistance in the anodized samples in both conditions. Therefore, it is necessary to constantly advance research on the use of nanoporous anodic alumina coatings on biomaterials surfaces.
  • Resumo IPEN-doc 26124
    Corrosion evaluation of an optical fiber laser treated stainless steel for biomedical applications
    2018 - PIERETTI, EURICO; CORREA, OLANDIR V.; PILLIS, MARINA F.; NEVES, MAURICIO M. das
    The implant manufacturing process includes marking the final devices for their identification, long-term quality control and traceability. Marking is carried out after cleaning and prior to sterilization. These marks eventually can concentrate stress leading to premature failure. The marked areas are defective regions that affect the oxide layer formed on the biomaterials used for implants favoring the onset of various corrosion forms, such as pitting, crevice or fatigue [1, 2]. This study aims to evaluate the effect of an Yb optical fiber laser marking process on the localized corrosion resistance of the austenitic stainless steel ISO 5832-1 samples. This is one of the most used materials for implants manufacturing. The electrochemical behavior of the marked areas obtained by this method was evaluated in a phosphate buffered solution (PBS) with pH of 7.4 and the results were compared with non treated samples. All tested surfaces were prepared according to the recommendations for clinical use. For localized corrosion resistance evaluation, electrochemical tests as monitoring the open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and cyclic potentiodynamic polarization measurements were performed. The results showed that the laser marks affects the protector characteristics of the biomaterial’s passive film. Lower pitting resistance was associated to the laser marked areas, because of its roughness changes.