Navegando por Assunto "Carbon"

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Acesso aberto (Open Access)
Transporte eletrônico em um alótropo de grafeno nanofitas de bifenileno com bordas hidrogenadas
(Universidade Federal do Pará, 2024-11-06) SOUZA, Lucas Pessoa de; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
Carbon-based nanostructured materials have aroused considerable interest in the scientific community due to their remarkable technological properties. Among the various carbon structures, graphene stands out as an allotropic form with a two-dimensional (2D) hexagonal structure, resulting from the sp² hybridization of carbon. In this work, we investigated the electronic properties of structures based on a 2D allotropic form of carbon, composed of rings of 4, 6 and 8, called Biphenylene. The research used the hydrogenation of the top of Biphenylene nanosheets, with the aim of exploring applications in molecular electronics. To achieve this, we employ Density Functional Theory (DFT) to optimize the structures and combine DFT with the Non-Equilibrium Green Functions method to obtain electronic transport properties. The band structure results indicate that, among the unit cells analyzed, the Biphenylene cell behaves as a conductive material when analyzed in the zigzag direction, while in the archmair direction they present characteristics of semiconductors. Regarding electronic transport properties, the Biphenylene nanodevice demonstrates behaviors like those of a field effect transistor in the studied range. Specifically, the zzBFNRH-O device, which exhibits field-effect transistor characteristics in the range of 0.00 V to 0.07 V, the same behavior we can observe for the zzBFNRH-H device, which exhibits the behavior of a field effect transistor for ranges from 0.00V to 0.50V. We can observe the behavior of the archBFNRH-O device where it indicates the behavior of a metal, presenting current conduction values after 0.10V. The archBFNRH-H device presents the behavior of a semiconductor, which indicates a gap of 1.8eV. We can observe that when the device width increases, this gap decreases. These results demonstrate that structures based on Biphenylene present themselves as a promising alternative for the development of nanodevices and applications in molecular electronics.
Acesso aberto (Open Access)
Transporte pneumático fluidizado: estudos de casos aplicados à indústria do alumínio primário
(Universidade Federal do Pará, 2011-08) VASCONCELOS, Paulo Douglas Santos; MESQUITA, André Luiz Amarante; http://lattes.cnpq.br/1331279630816662
This work is a contribution to science and applied technology developed to fluidized bed and fluidized motion conveying used in the powder handling of the industrial processes. In the case of fluidized bed it is proposed an empirical equation to predict the minimum fluidization velocity for the fluoride alumina, crust powder and others powders used in the industrial processes with good results compared with the experiments and the equations available in the literature. It was also studied the constitutive equations to predict the behavior of the angle of repose and interparticles friction as a function of the superficial velocity of fluidization. In a second step it is proposed an equation to predict the capacity of the Air Pneumatic Fluidized Conveyor with good results compared with the experiments for fluoride alumina. The Air Fluidized Conveyor is a contribution to applied technology reducing the consumption of energy, it operates even in upward direction, and so, decreasing the rate kWh/ton in the powder handling of the industrial processes.