Navegando por Autor "Sambrano, Julio Ricardo"
Agora exibindo 1 - 4 de 4
- Resultados por página
- Opções de Ordenação
Artigo Experimental and theoretical correlation of very intense visible green photoluminescence in BaZrO3 powders(American Institute of Physics, 2008) Cavalcante, L. S.; Zampieri, M.; Espinosa, J. W. M.; Pizani, Paulo Sérgio; Paskocimas, Carlos Alberto; Sambrano, Julio Ricardo; Silva, Elson Longo da; Varela, José A.; Simões, M. L.; Longo, V. M.Very intense visible green photoluminescence PL was observed at room temperature in structurally ordered-disordered BaZrO3 powders. Ab initio calculations, ultraviolet-visible absorption spectroscopy, electron paramagnetic resonance, and PL were performed. Theoretical and experimental results showed that local defects in the cubic structure caused by ZrO5 ·VO z complex clusters, where VO z =VO x , VO • , and VO ••, play an important role in the formation of hole-electron pairs, giving rise to a charge gradient in the structure which is responsible for PL emissionArtigo Highly intense violet-blue light emission at room temperature in structurally disordered SrZrO3 powders(American Institute of Physics, 2007-02-27) Longo, V. M.; Cavalcante, L. S.; Figueiredo, A. T. de; Santos, L. P. S.; Silva, Elson Longo da; Varela, José A.; Sambrano, Julio Ricardo; Paskocimas, Carlos Alberto; Vicente, F. S. de; Hernandes, C.Violet-blue photoluminescence was produced at room temperature in a structurally disordered SrZrO3 perovskite structure with a 350.7 nm excitation line. The intensity of this emission was higher than that of any other perovskites previously studied. The authors discuss the role of structural order-disorder that favors the self-trapping of electrons and charge transference, as well as a model to elucidate the mechanism that triggers photoluminescence. In this model the wide band model, the most important events occur before excitationArtigo New 2D nanosheets based on the octa-graphene(Elsevier, 2020-10) Paskocimas, Carlos Alberto; Fabris, Guilherme S.L.; Sambrano, Julio Ricardo; Paupitz, RicardoA class of 2D structures based on the architecture of the so called octa-graphene is proposed and theoretically investigated for the first time. The building blocks used to construct these structures are butadienes and linear carbon chains, with alternate single and triple bonds. The density functional theory (DFT) with periodic condi- tions is applied to study the electronic, structural, elastic and vibrational properties. These structures are stable and have interesting mechanical properties, as a large stiffness described by a 2D Young modulus varying within the range 116:00ðN =mÞ Y2D 308:36ðN =mÞ, values in the same order of magnitude of that found for graphene (Y2D 340:0N=m). Another mechanical feature is the 2D Poisson ratio, found to be within the range 0:077 ν2D 0:628, a range of values impossible to cover with 3D materials. For their electronic structures, it was found that these materials are capable of going from metallic (C-based) to large band-gap semiconductors (BN-based) with indirect gap opening Eg 5:49eV. The Raman spectrum for each one of these materials was calculated, revealing their vibration specific signatures that could be used to identify the existence of such materials in experimental studies. Another feature investigated was the interaction of the octagonal nanopores with Li atoms which could be useful for energy storage or gas separation membranesArtigo A promising nanoporous AlxGað1xÞN nanosheet based on octagraphene(Elsevier, 2021-02-01) Paskocimas, Carlos Alberto; Fabris, Guilherme S.L.; Sambrano, Julio Ricardo; Paupitz, RicardoA new class of 2D inorganic materials named octa-AlxGað1xÞN (x 1⁄4 0; 0:25; 0:5; 0:75 and 1) with the octa- graphene architecture is theoretically investigated by Density Functional Theory simulations. It was found that the energy band gap increased with the introduction of Al atoms. The calculated Young modulus is within the range (46.02 N/m 6 Y2D 653.66 N/m) and Poisson’s ratio within (0:733 6 m 6 0:783), while frequency calculations reveal that these structures are dynamically stable. Energetic barriers for Li, Na and K diffusion were also studied and were found values lower than those calculated for octagraphene in a previous work