JOAO COUTINHO FERREIRA
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Artigo IPEN-doc 30849 Development of hydrophobic graphenoid layer on Portland cement for non-thermal plasma method2024 - PEREIRA FILHO, N.G.; SOARES, E.P.; FERREIRA, J.C.; SOUZA, R.F.B. de; ANDRADE, D.A.; NETO, A.O.This study focuses on the development of hydrophobic layer on Portland cement using graphenoid materials to enhance impermeability and hydrophobicity. X-ray diffraction analysis indicated that characteristic peaks associated with concrete, such as ettringite, calcium hydroxide, and calcite, remained intact. The application of graphenoid material produced by non-thermal plasma resulted in the formation of carbonaceous structures, minimally affecting the overall cement structure. Raman spectroscopy provided detailed insights into the composition, highlighting the presence of specific and indicating boundary defects. Moreover, contact angle measurements confirmed a substantial increase in hydrophobicity for the graphene-coated cement, with an average angle of 117° ± 4.72° demonstrated graphenoid material layers deposited over structural defects, effectively waterproofing and enhancing local hydrophobicity.Artigo IPEN-doc 28845 Preparation and characterization of high-performance Ni-based core-shell catalyst for ethanol steam reforming2022 - MORAES, TAMARA S.; BERGAMASCHI, VANDERLEI S.; FERREIRA, JOAO C.; SPINACE, ESTEVAM V.A core–shell catalyst, based on nickel nanoparticles supported on silica nanospheres and surrounded by ceria, was tested for ethanol steam reforming (ESR) reaction (H2O/ethanol: 3/1) under low-temperature conditions (400, 500 and 600 °C) in order to test its stability during the reaction. Two other catalysts of Ni supported in SiO2 and CeO2 were also synthesized to be compared with the core–shell catalyst in the ESR. All catalysts showed excellent activity at 500 and 600 °C with 100% ethanol conversion. Increasing the reaction temperature, carbon deposition on the surface of the catalysts decreases throughout the reaction. The core–shell catalyst showed high coke inhibition capacity in the ESR at 600 °C, without coke formation for at least 100 h of reaction. On the other hand, after 20 h of ESR at 600 °C, Ni–SiO2 and Ni/CeO2 catalysts showed formation of 6.3 and 5.2 mgC/(gcat.h) of coke, respectively. The strong redox capacity of ceria together with the change in catalyst structure due to the deposition of cerium oxide on top of Ni particles led to an excellent ESR activity of this catalyst.