Synthesis and TL Characterization of Li2B4O7 Doped with Cooper and Manganese

Copper (Cu) and manganese (Mn) doped tissue equivalent Li2B4O7 were prepared by solid state sintering. The glow curves shows a high temperature peak at 222 °C for Li2B4O7:Cu and for Li2B4O7:Mn at 218 °C. Linear dose response is observed up to 140 Gy. With a thermal treatment at 125 °C, the first peak of the phosphors doped with copper (95 °C) and manganese (90 °C) disappears and the main TL peaks remain isolated. The dose rate dependence was studied by exposing the samples at doses of 25 Gy and 250 Gy. At low dose it was observed that the Li2B4O7:Cu TL response has non-dependence on dose rate, and at higher dose was observed that there is a dependence of the TL response with the different dose rateFil: Guarneros Aguilar, C.. Benemérita Universidad Autónoma de Puebla. Facultad de Ciencias Físico-Matemáticas. Posgrado en Física Aplicada; MéxicoFil: Cruz Zaragoza, E.. Universidad Nacional Autónoma de México. Instituto de Ciencias Nucleares. Unidad de Irradiación y Seguridad Radiológica; MicronesiaFil: Marcazzo, Salvador Julian. Universidad Nacional del Centro de la Provincia de Bs.as.. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil; ArgentinaFil: Palomino Merino, R.. Benemérita Universidad Autónoma de Puebla. Facultad de Ciencias Físico-Matemáticas. Posgrado en Física Aplicada; MéxicoFil: Espinosa, J.. Benemérita Universidad Autónoma de Puebla. Facultad de Ciencias Físico-Matemáticas. Posgrado en Física Aplicada; Méxic

Influence of laser pulse regime on the structure and optical properties of TiO2 nanolayers

TiO2 films were deposited onto glass substrates by pulsed laser deposition (PLD) in high vacuum under monopulse and multipulse excitation. After deposition, a thermal treatment on air atmosphere was done to promote crystallization. Films were studied by x-ray diffraction, energy dispersive spectroscopy, scanning electron, atomic force microscopy, UV-vis spectroscopy, and ellipsometry. After air annealing, films gain a different amount of oxygen: TiO1.9 in multipulse regime versus TiO1.7 in the monopulse one. Splashing is observed in both regimes although in the multipulse mode greater particles are found, that derived in a less compact film after annealing which could be the cause of the better oxygen diffusion. The optical band gap of the film prepared with monopulse excitation is 3.09 eV. This value increased to 3.34 eV with annealing, corresponding to that of anatase. The film made with multipulses has an Eg = 3.12 eV which was invariant upon annealing. The difference in the properties of the films grown in the different regimes was attributed to the re-excitation of the plasma during the ablation process in the multipulse ablation that leads to an increased splashing density and thereafter a less compact film and the presence of off-stoichiometry inclusions within the film bulk.Fil: Peñaloza Mendoza, Y.. Instituto Politécnico Nacional; MéxicoFil: Alvira, Fernando Carlos. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Biomembranas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Caballero Briones, F.. Instituto Politécnico Nacional; MéxicoFil: Guarneros Aguilar, C.. Instituto Politécnico Nacional; MéxicoFil: Ponce, L.. Instituto Politécnico Nacional; Méxic

One-step, low temperature synthesis of reduced graphene oxide decorated with ZnO nanocrystals using galvanized iron steel scrap

Production of a ZnO-rGO composite, using a novel one-pot method consisting in continuously flowing argon into a GO aqueous suspension heated at 80 C, in the presence of galvanized iron steel scrap is presented. FTIR shows the complete disappearance of GO functional groups and only the C=C band remained, indicating extensive GO reduction. Raman spectra indicated sp2 character increase after reaction and the presence of the E2h mode of ZnO. SEM showed submicron crystals identified by XRD as ZnO in the hexagonal phase, while TEM images indicate ZnO nanoparticles decorate mainly the rGO borders. Optical band gap of 3.5 eV corresponding to ZnO, and optical transitions at 4.1 and 5.5 eV related with n → π and π → π∗ were observed. Electrochemical characterization by cyclic voltammetry shows an specific capacitance of 4.7 F g-1 at a scan rate of 5 mVs-1, which drops to ca. 0.8 F g-1 at 200 mVs-1. By electrochemical impedance spectroscopy, the relaxation time was ca. 5 ms. The proposed mechanism for the materials' synthesis includes Zn dissolution from scrap, galvanic displacement of oxygen moieties at the GO sheet, Zn deposition onto the carbon surface, and further oxidation and growth of ZnO nanocrystals.</p

One-step, low temperature synthesis of reduced graphene oxide decorated with ZnO nanocrystals using galvanized iron steel scrap

Production of a ZnO–rGO composite, using a novel one-pot method consisting in continuously flowing argon into a GO aqueous suspension heated at 80 °C, in the presence of galvanized iron steel scrap is presented. FTIR shows the complete disappearance of GO functional groups and only the C=C band remained, indicating extensive GO reduction. Raman spectra indicated sp ^2 character increase after reaction and the presence of the E _2h mode of ZnO. SEM showed submicron crystals identified by XRD as ZnO in the hexagonal phase, while TEM images indicate ZnO nanoparticles decorate mainly the rGO borders. Optical band gap of 3.5 eV corresponding to ZnO, and optical transitions at 4.1 and 5.5 eV related with n →  π and π  →  π * were observed. Electrochemical characterization by cyclic voltammetry shows an specific capacitance of 4.7 F g ^−1 at a scan rate of 5 mVs ^−1 , which drops to ca. 0.8 F g ^−1 at 200 mVs ^−1 . By electrochemical impedance spectroscopy, the relaxation time was ca. 5 ms. The proposed mechanism for the materials‘ synthesis includes Zn dissolution from scrap, galvanic displacement of oxygen moieties at the GO sheet, Zn deposition onto the carbon surface, and further oxidation and growth of ZnO nanocrystals

Transmission Electron Microscopy study of a GaN thin film grown on Al2O3 by MOCVD

For this work a structural study of the GaN/Al2O3 heteroepitaxy was carried out by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). A GaN thin film grown on the c-plane of an Al2O3 substrate by MOCVD was characterized. The sample was observed by AFM and SEM, the analysis showed the GaN formed hexagonal-like features on the surface of the sample. An abrupt interface was observed in the TEM cross section images. Results showed GaN with excellent structural properties was grown