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Orozco-Gonzalez P.,CINVESTAV | Castro-Roman M.,CINVESTAV | Martinez A.I.,CINVESTAV | Herrera-Trejo M.,CINVESTAV | And 3 more authors.

To contribute to the understanding of the Al-Fe-Mn-Si system, an exhaustive analysis of the intermetallic phases formed during thermal analysis experiments and specific isothermal treatments was carried out. In this work, three different phases were identified: the extensively reported β and α phases and the τh phase. The τh phase has been reported for the ternary Al-Fe-Si system, but not for the quaternary Al-Fe-Mn-Si system. Nonetheless, the present results suggest that the formation of the τh phase upon solidification of the alloy can be stabilized in the quaternary Al-Fe-Mn-Si system, with respect to the monoclinic θ-Al3Fe phase in the ternary Al-Fe-Si system, due to the Mn addition. The τh phase was unambiguously identified with the help of complementary techniques such as SEM/EDS, X-ray diffraction and Mössbauer spectroscopy. © 2010 Elsevier Ltd. All rights reserved. Source

Gonzalez-Hernandez R.,CINVESTAV | Martinez A.I.,CINVESTAV | Falcony C.,CINVESTAV | Lopez A.A.,Instituto Peruano Of Energia Nuclear | And 3 more authors.
Materials Letters

ZnO and ZnO:F nanoparticles were successfully prepared by precipitation in the presence of oxalic acid. This procedure yields ZnO and ZnO:F nano-arrangements of different lengths consisting of chains of quasi-spherical nanoparticles of ∼ 30 nm in size. Only the wurtzite ZnO structure was detected for both undoped and fluorine doped ZnO nanoparticles. By absorption and photoluminescence measurements, a diminishing of singly ionized oxygen vacancies was detected when fluorine is present in the nanoparticles; while a blue shift of the exciton absorption was observed. Additionally, by NIR reflectance measurements, the creation of free carriers by the fluorine doping of ZnO nanoparticles was observed. © 2010 Elsevier B.V. All rights reserved. Source

Lopez A.,National Autonomous University of Mexico | Lopez A.,Instituto Peruano Of Energia Nuclear | Lopez A.,University of Lima | Acosta D.,National Autonomous University of Mexico | And 3 more authors.
Powder Technology

Transparent TiO2 thin films were deposited on soda lime glass at different substrate temperatures by a simple and reproducible spray pyrolysis technique from aqueous peroxo-polytitanic acid. Both the as-prepared and annealed films (3h thermal treatment in air at 500°C) were characterized by AFM, SEM, TEM, XRD, FT-IR and UV-visible spectroscopy. The as-prepared films present predominant low crystallized structure, low porosity, high surface roughness and grain agglomerates while the annealed films exhibit slightly better polycrystalline structure of brookite phase. The as-deposited TiO2 films prepared at low substrate temperatures (280°C) show the best photocatalytic activity, against methylene-blue, due principally to their small grain size and high surface area. © 2010 Elsevier B.V. Source

Rodriguez J.,University of Lima | Rodriguez J.,University of Tarapaca | Jorge C.,University of Lima | Zuniga P.,University of Lima | And 4 more authors.
Journal of Solar Energy Engineering, Transactions of the ASME

Solar water disinfection was performed using TiO2and a Ru(II) complex as fixed catalysts located in a compound parabolic collector photoreactor. Studies were performed in the laboratory as well as at a greenfield site. Under laboratory conditions, natural water contaminated with cultured bacteria was photocatalytically treated and the influence of the photolysis as well as of both catalysts was studied. Experiments were performed with contaminated water flowing at 12 l/min; under these conditions, photocatalytic experiments performed with a supported heterogeneous photocatalyst (Ahlstrom paper impregnated with TiO2) showed it to be effective in degrading bacteria in water. The Ru complex catalyst, however, showed no clear evidence for disinfecting water, and its efficiency was comparable to the simple photolysis. Under on-site experiments, bacteria contaminated water from the Yaurisque river at Cusco, Peru was treated. As a general trend, after photocatalytic treatment a reduction in the E-coli population present in water was observed. Whenever disinfection was achieved in the experiments, no regrowth of bacteria was observed after 24 h. However, a reduction in the prototype efficiency was observed both in laboratory and on-site experiments. This was ascribed to aging of the photocatalyst as well as due to the deposition of particles onto its surface. In cases in which incomplete disinfection resulted, a low rate of E-coli growth was observed 24 h after ending the experiment. However, pseudomones seem to be resistant to the treatment. © 2010 by ASME. Source

Vasilopoulou T.,Greek National Center For Scientific Research | Stamatelatos I.E.,Greek National Center For Scientific Research | Montoya E.H.,Instituto Peruano Of Energia Nuclear | Bedregal P.S.,Instituto Peruano Of Energia Nuclear | And 2 more authors.
Journal of Radioanalytical and Nuclear Chemistry

The large sample neutron activation analysis (LSNAA) method developed at NCSR “Demokritos” for large and irregular-shaped objects was applied for the analysis of a Peruvian pottery artifact with the shape of an animal. The correction factors required for neutron self-shielding and gamma-ray self-attenuation within the sample material were derived through Monte Carlo simulations using the MCNP code, based on an accurate model obtained by computerized tomography X-ray scanning. The LSNAA results were compared with those from conventional instrumental neutron activation analysis (INAA) and a very good agreement was observed. © 2014, Akadémiai Kiadó, Budapest, Hungary. Source

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