Marco A.S. de Abreu
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Featured researches published by Marco A.S. de Abreu.
Nanotechnology | 2007
Edisson Morgado; Paula M. Jardim; Bojan A. Marinkovic; Fernando Rizzo; Marco A.S. de Abreu; José Luiz Zotin; Antonio S. Araujo
H-trititanate nanotubes obtained by alkali hydrothermal treatment of TiO(2) followed by proton exchange were compared to their bulk H(2)Ti(3)O(7) counterpart with respect to their thermally induced structural transformation paths. As-synthesized and heat-treated samples were characterized by XRD, TEM/SAED, DSC and spectroscopy techniques, indicating that H(2)Ti(3)O(7) nanotubes showed the same sequence of structural transformations as their bulk counterpart obtained by conventional solid state reaction. Nanostructured H(2)Ti(3)O(7) converts into TiO(2)(B) via multistep transformation without losing its nanotubular morphology. The transformation occurs between 120 and 400 degrees C through topotactic mechanisms with the intermediate formation of nanostructured H(2)Ti(6)O(13) and H(2)Ti(12)O(25), which are more condensed layered titanates eventually rearranging to TiO(2)(B). Our results suggest that the intermediate tunnel structure H(2)Ti(12)O(25) is the final layered intermediate phase, on which TiO(2)(B) nucleates and grows. The conversion of nanostructured TiO(2)(B) into anatase is completed at a much lower temperature than its bulk counterpart and is accompanied by loss of the nanotubular morphology.
Central European Journal of Chemistry | 2012
Marco A.S. de Abreu; Edisson Morgado; P.M. Jardim; Bojan A. Marinkovic
AbstractHydrogen titanate nanotubes (H-TTNT) were synthesized by the alkali hydrothermal method followed by proton exchange and then submitted either to thermal treatment or to acid hydrothermal reaction to generate TiO2-anatase nanocrystals of different morphologies. The samples were characterized by XRPD, TGA, sulfur analysis, N2 physisorption, UV-Vis spectroscopy and TEM. Their photocatalytic activities were determined by measuring the NO conversion in inert gas stream passed through the powder catalyst bed under UV radiation. Incomplete transformation into anatase resulted in nanomaterials with low activity due to coexistence with H-TTNT or TiO2-B precursors. Anatase specimens derived from H-TTNT aged in strong sulfuric acid media contained equidimensional nanoparticles, but retention of sulfate negatively affected their photocatalytic activity. Combining milder acidic pH with higher aging temperature, allowed synthesis of a sulfate free anatase with the same optical properties and specific surface area as the counterpart produced by calcination of H-TTNT at 550°C; however, the former exhibited truncated bi-pyramid nanocrystals and the other adopted the form of nanorods. This latter showed the highest photocatalytic activity for NO abatement, outperforming the benchmark photocatatyst TiO2-P25; this improved activity was tentatively ascribed to the maximization of high energy {001} facets in anatase nanorods formed during calcination of H-TTNT.
Solid State Sciences | 2006
Edisson Morgado; Marco A.S. de Abreu; Oscar Rene Chamberlain Pravia; Bojan A. Marinkovic; Paula M. Jardim; Fernando Rizzo; Antonio S. Araujo
Chemistry of Materials | 2007
Edisson Morgado, Jr., ,†,‡; Marco A.S. de Abreu; Gustavo Torres Moure; Bojan A. Marinkovic; and Paula M. Jardim; Antonio S. Araujo
Materials Research Bulletin | 2007
Edisson Morgado; Marco A.S. de Abreu; Gustavo Torres Moure; Bojan A. Marinkovic; Paula M. Jardim; Antonio S. Araujo
Journal of Solid State Chemistry | 2009
Edisson Morgado; Bojan A. Marinkovic; Paula M. Jardim; Marco A.S. de Abreu; Fernando Rizzo
Applied Catalysis A-general | 2009
Edisson Morgado; José Luiz Zotin; Marco A.S. de Abreu; Danielle de Oliveira Rosas; Paula M. Jardim; Bojan A. Marinkovic
Fuel Processing Technology | 2011
William Richard Gilbert; Edisson Morgado; Marco A.S. de Abreu; Gabriela de la Puente; Francisco J. Passamonti; Ulises Sedran
Materials Chemistry and Physics | 2011
Edisson Morgado; Bojan A. Marinkovic; Paula M. Jardim; Marco A.S. de Abreu; Maria da Graça Carneiro da Rocha; Pascal Bargiela
Archive | 2008
Edisson Morgado Junior; Marco A.S. de Abreu; Gustavo Torres Moure