Browsing by Author "Orlandi, Marcelo Ornaghi"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Carbon-coated SnO2 nanobelts and nanoparticles by single catalytic step.
    (2009) Carreño, Neftalí Lenin Villarreal; Nunes, Michael Ramos; Garcia, Irene Teresinha Santos; Orlandi, Marcelo Ornaghi; Fajardo, Humberto Vieira; Longo, Elson
    Several types of carbon nanostructures (amorphous and graphitic), for the coating of SnO2 nanobelts and nanoparticles were obtained by a single catalytic process, during methane, natural gas, and methanol decomposition using the reactivity of surface-modified SnO2 nanostructure as a nanotemplate. The nanostructured catalyst templates were based on transition metal nanoparticles supported on SnO2 nanobelts previously prepared by a carbothermal reduction process. Carbon-coated SnO2 nanopowders were also successfully synthesized for the fabrication of carbon spheres. The carbon coating process and yield, along with the nature of the nanostructured carbon, are strongly influenced by the chemically modified surface of the SnO2 nanostructure template and the chemical reaction gas composition. The preliminary catalytic activity and gas-sensing properties of these novel materials based on metal nanoparticles and carbon-coated SnO2 were determined.
  • No Thumbnail Available
    Item
    Feasible and clean solid-phase synthesis of LiNbO3 by microwave- induced combustion and its application as catalyst for low- temperature aniline oxidation.
    (2018) Carreño, Neftalí Lenin Villarreal; Deon, Vinícius Gonçalves; Silva, Ricardo M.; Santana, Luiza R.; Pereira, Rodrigo M.; Orlandi, Marcelo Ornaghi; Ventura, Wellington Martins; Dias, Anderson; Taylor, Jason Guy; Fajardo, Humberto Vieira; Mesko, Márcia Foster
    In this work, a feasible, fast, clean and efficient microwave-induced combustion method for direct synthesis of LiNbO3 in solid phase was developed. X-ray powder diffraction studies showed that quasi-pure Li−Nb−O phases, such as LiNbO3 and Li3NbO4, or mixtures of LiNbO3, Li3 NbO4 and LiNb3O8, could be successfully synthesized. The resulting powders were efficiently applied as catalysts under ambient conditions in the oxidation process of aniline using hydrogen peroxide as oxidant. The proposed method was performed in a commercial system using high-pressure quartz vessels, which allowed safe control of the reactions−that usually occurs in less than 1 min. The results showed that the reaction conditions as well as the structural and morphological characteristics of the catalyst influenced the aniline oxidation process. Therefore, the present method for the preparation of LiNbO3 described herein, displayed many advantages when compared to conventional combustion methods, such as the physical characteristics of the obtained compound. Moreover, this new approach is considerably faster, safer and cleaner than other traditional procedures described in literature for LiNbO3 synthesis. This new microwave-induced combustion method is less time-consuming, saves energy, as well as affording the stoichiometric formation of inorganic particles.
  • No Thumbnail Available
    Item
    SnO2 nanoparticles functionalized in amorphous silica and glass.
    (2009) Carreño, Neftalí Lenin Villarreal; Nunes, Michael Ramos; Ratmann, Cristiane Wienke Raubach; Granada, Rosana L.; Krolow, Matheus Zorzoli; Orlandi, Marcelo Ornaghi; Fajardo, Humberto Vieira; Probst, Luiz Fernando Dias
    Two different routes to obtain SnO2 nanoparticles, undoped and doped with rare earth metals (Eu or Pr), are described herein. The first route was based on the polymeric precursor method that led to the obtainment of SnO2 nanoparticles dispersed in amorphous silica. The second route was simply the impregnation with SnCl4 aqueous solution of SiO2–CaO glass microparticles functionalized with hydroxyl (−OH) groups. The materials were characterized by N2 physisorption, XRD, EDS and TEM analyses. We also present the results of catalytic experiments involving the nanocrystalline composites in ethanol steam reforming. The catalytic properties of the undoped composites with SnO2 supported on SiO2–CaO glass differ from their doped analogues, however, they were both selective towards ethylene formation, in contrast to the doped composite obtained by the polymeric precursor method.