OLANDIR VERCINO CORREA

OLANDIR VERCINO CORREA

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Lecithin/graphite modified kapok fibers for functional xerogel composites
2024 - SANDRINI, DAIANA M.F.; PILLIS, MARINA F.; CORREA, OLANDIR V.; MADESH, PRIYANKA; KRISHNASAMY, BALAJI; PETRI, DENISE F.S.
Kapok fibers (KFs) exhibit a distinctive hollow tubular structure and hydrophobic surface, positioning them as intriguing materials with a leading role in developing new materials for various applications. In this study, KFs from Ceiba speciosa trees underwent modification with soy lecithin (SL) and graphite (G) particles. The wax on KFs primarily comprised hydrophobic compounds, including bis(2-ethylhexyl) phthalate, N–N-dimethyldodecanamide and 1-chloro-dodecane. These compounds interacted favorably with the alkyl chains of SL, exposing the SL charge groups to the medium, as confirmed by X-ray photoelectron spectroscopy (XPS) and wettability increase. Incorporating SL and G particles to the KFs improved their thermal stability and charring capability. KFs modified with SL and G (at 13 wt% or 16 wt%) were added to aqueous solutions of hydroxypropyl methylcellulose (HPMC) at 30 g L−1, forming homogeneous dispersions that were molded and oven-dried to create xerogel composites. Regardless of the G content, all xerogels exhibited compressive elastic modulus of 23 ± 1 kPa, maximum strain of 60% strain at 5.6 ± kPa stress, and after unloading, the xerogels recovered 77% of their original height. Their porosity amounted to 68 ± 3%. The xerogels showed a maximum sound absorption coefficient (SAC) of approximately 0.6 at 2 kHz, making them interesting sustainable materials for building and architecture. Surface resistivity and volume resistivity values amounted to 3.8 × 108 Ω/square and 8.84 × 108 Ω cm, respectively, indicating that the xerogel composites displayed antistatic properties and potential application as packing material.
VIS-active TiO2 films decorated by expanded graphite
2024 - BENTO, RODRIGO T.; CORREA, OLANDIR V.; GASTELOIS, PEDRO L.; PILLIS, MARINA F.
TiO2/C nanocomposite films were applied on water treatment. Expanded graphite nanosheets (EG) were obtained by UVC-assisted liquid-phase exfoliation technique, without the addition of acids, surfactants, or aggressive oxidizing agents, which characterizes the process as an eco-friendly method. The carbon nanosheets were synthesized directly from graphite bulk at different times and deposited on TiO2 films surface by airbrush spray coating method, forming a TiO2/C heterojunction. The increase in the exfoliation time promoted a more efficient photocatalytic dye removal under visible light. Morphological modifications, changes in the electronic structure, and wide range of light absorption were observed from the TiO2/C heterojunction formation. The results showed that hybrid TiO2/C supported photocatalyst is a promise alternative for practical photocatalytic applications under sunlight.
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.
Enhancement of the RE-boronizing process through the use of La, Nd, Sm, and Gd compounds
2022 - SANTAELLA, CESAR R.K.; COTINHO, SAMUEL P.; CORREA, OLANDIR V.; PILLIS, MARINA F.
Rare-earth elements have been used in the thermochemical treatment of boronizing to enhance boron diffusion. In order to further investigate the effect of these elements on the process, neodymium-, samarium-, and gadolinium were utilized for the treatment of AISI 1045 samples carried out at the temperature of 1173 K for 4 h. The resulting boride layers formed were characterized through optical microscopy, microhardness test, and X-ray diffraction (XRD). The comparison of the layers showed that the addition of neodymium increased the depth by 48%, with samarium by 54%, and with gadolinium by 76%.
Surface properties enhancement by sulfur-doping TiO2 films
2021 - BENTO, RODRIGO T.; CORREA, OLANDIR V.; ANTUNES, RENATO A.; PILLIS, MARINA F.
TiO2 films were sulfur-doped through an alternative route based on the decomposition of H2S at low temperatures. MOCVD technique was used to grown the films on borosilicate glass substrates at 400 °C. The doping was carried out at 50, 100 and 150 °C under a mixture of H2-2%v.H2S. SO42− groups were observed in the surface revealing the substitution of Ti4+ by S6+. Superficial roughness and wettability were also modified by the formation of these sulfate groups on the surface. Photocatalytic experiments of methyl-orange dye decolorization under visible light indicated that the 8 at.% S-TiO2 film exhibited the highest photocatalytic activity, with 72.1% of dye decolorization. The results suggest that the exposition of TiO2 films to the mixture H2-H2S at low temperatures is an efficient method of doping. These films allow the decolorization of the dye under visible light irradiation, which enable its practical use under sunlight or even indoor.
On the surface chemistry and the reuse of sulfur-doped TiO2 films as photocatalysts
2021 - BENTO, RODRIGO T.; CORREA, OLANDIR V.; PILLIS, MARINA F.
The surface chemistry and recyclability of sulfur-doped titanium dioxide (TiO2) films was evaluated. The photocatalysts were grown by metalorganic chemical vapor deposition (MOCVD) at 400 ◦C. The films were sulfur-doped at 50 ◦C by using hydrogen sulfide (H2S) as sulfur source. The photocatalytic behavior of the films was measure by monitoring the methyl orange dye decolorization under visible light for several cycles. The films are formed only for the anatase crystalline phase. The results demonstrated that no structural modifications or significant differences in the morphology of the films occurred after their use. The sulfur-doped TiO2 films presented good photocatalytic activity, with an efficiency of 72.1% under visible light in its first use. The durability experiments suggest that even with the dye impregnation on the catalyst surface, the photocatalytic activity of the S-doped TiO2 films remained around 70% in the first 3 cycles, which allows their practical application for water treatment and purification under sunlight.
Visible-light photocatalytic activity and recyclability of N-doped TiO2 films grown by MOCVD
2020 - OLIVEIRA, E.C. de; BENTO, R.T.; CORREA, O.V.; PILLIS, M.F.
Nitrogen-doped TiO2 films were grown on borosilicate glass substrates at 400 °C by the metallorganic chemical vapor deposition (MOCVD) for removing dye from water under visible light. The effect of N-doping on the structural, surface, and photocatalytic properties of films was evaluated. X-ray photoelectron spectroscopy (XPS) analyses revealed that 1.56 and 2.44 at% of nitrogen were incorporated into the films by varying the NH3 flux during the growth. Methyl orange dye degradation experiments showed that the N-doped films presented photoactivity under visible light. The film containing 2.44 at% of nitrogen exhibited the best photocatalytic behavior, with 55% of efficiency. Recyclability tests under visible light showed that the film efficiency dropped gradually after each test. N-TiO2 films grown by MOCVD have the potential to be used in environmental applications by removing pollutants using a green method under sunlight or even under internal illumination, although its reuse is limited.
Effect of growth parameters on the photocatalytic performance of TiO2 films prepared by MOCVD
2020 - MARCELLO, BIANCA A.; CORREA, OLANDIR V.; BENTO, RODRIGO T.; PILLIS, MARINA F.
The present study evaluated the main factors that influence the photocatalytic activity of titanium dioxide (TiO2) films grown by metalorganic chemical vapor deposition (MOCVD) at 400 and 500 °C, in different growth times. The photocatalytic behavior was analyzed by measuring the methyl orange dye degradation at different pH values. Structural and morphological characteristics, and the recyclability of the catalysts for several cycles were also investigated. Anatase phase was identified in all films. The higher photodegradation performances were obtained at acidic pH. The results demonstrated that the photocatalyst thickness is an important parameter in heterogenous photocatalysis. The best photocatalytic result occurred for the 395 nm-thick TiO2 film grown at 400 °C, which presented 65.3% of the dye degradation under UV light. The recyclability experiments demonstrated that the TiO2 films grown by MOCVD present a great stability after several photocatalytic cycles, which allows their practical application for water treatment with high efficiency.
Photocatalytic activity of undoped and sulfur-doped TiO2 films grown by MOCVD for water treatment under visible light
2019 - BENTO, RODRIGO T.; CORREA, OLANDIR V.; PILLIS, MARINA F.
Titanium dioxide ceramic coatings have been used as catalysts in green technologies for water treatment. However, without the presence of a dopant, its photocatalytic activity is limited to the ultraviolet radiation region. The photocatalytic activity and the structural characteristics of undoped and sulfur-doped TiO2 films grown at 400 °C by metallorganic chemical vapor deposition (MOCVD) were studied. The photocatalytic behavior of the films was evaluated by methyl orange dye degradation under visible light. The results suggested the substitution of Ti4+ cations by S6+ ions into TiO2 structure of the doped samples. SO4 2− groups were observed on the surface. S-TiO2 film exhibited good photocatalytic activity under visible light irradiation, and the luminous intensity strongly influences the photocatalytic behavior of the S-TiO2 films. The results supported the idea that the sulfur-doped TiO2 films grown by MOCVD may be promising catalysts for water treatment under sunlight or visible light bulbs.
High temperature oxidation behavior of yttrium dioxide coated Fe-20Cr alloy
2016 - PILLIS, MARINA F.; CORREA, OLANDIR V.; RAMANATHAN, LALGUDI V.