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Featured researches published by Marco A.S. de Abreu.


Nanotechnology | 2007

Multistep structural transition of hydrogen trititanate nanotubes into TiO2-B nanotubes : a comparison study between nanostructured and bulk materials

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

The effect of anatase crystal morphology on the photocatalytic conversion of NO by TiO2-based nanomaterials

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

A study on the structure and thermal stability of titanate nanotubes as a function of sodium content

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

Characterization of Nanostructured Titanates Obtained by Alkali Treatment of TiO2-Anatases with Distinct Crystal Sizes

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

Effects of thermal treatment of nanostructured trititanates on their crystallographic and textural properties

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

Characterization and thermal stability of cobalt-modified 1-D nanostructured trititanates

Edisson Morgado; Bojan A. Marinkovic; Paula M. Jardim; Marco A.S. de Abreu; Fernando Rizzo


Applied Catalysis A-general | 2009

Characterization and hydrotreating performance of NiMo catalysts supported on nanostructured titanate

Edisson Morgado; José Luiz Zotin; Marco A.S. de Abreu; Danielle de Oliveira Rosas; Paula M. Jardim; Bojan A. Marinkovic


Fuel Processing Technology | 2011

A novel fluid catalytic cracking approach for producing low aromatic LCO

William Richard Gilbert; Edisson Morgado; Marco A.S. de Abreu; Gabriela de la Puente; Francisco J. Passamonti; Ulises Sedran


Materials Chemistry and Physics | 2011

Studies on Fe-modified nanostructured trititanates

Edisson Morgado; Bojan A. Marinkovic; Paula M. Jardim; Marco A.S. de Abreu; Maria da Graça Carneiro da Rocha; Pascal Bargiela


Archive | 2008

Continuous process for the preparation of sodium titanate nanotubes

Edisson Morgado Junior; Marco A.S. de Abreu; Gustavo Torres Moure

Collaboration


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Bojan A. Marinkovic

The Catholic University of America

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Paula M. Jardim

The Catholic University of America

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Antonio S. Araujo

Federal University of Rio Grande do Norte

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Fernando Rizzo

Pontifical Catholic University of Rio de Janeiro

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Anja Dosen

Pontifical Catholic University of Rio de Janeiro

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Bojan A. Marinkovic

The Catholic University of America

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