Teses em Engenharia Elétrica (Doutorado) - PPGEE/ITEC

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2317

O Doutorado Acadêmico inicio-se em 1998 e pertence ao Programa de Pós-Graduação em Engenharia Elétrica (PPGEE) do Instituto de Tecnologia (ITEC) da Universidade Federal do Pará (UFPA).

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Agora exibindo 1 - 9 de 9

Acesso aberto (Open Access)
Análise do enxofre corrosivo em óleo mineral isolante e remoção do dibenzil dissulfeto com nanotubos de carbono baseados em matriz metálica
(Universidade Federal do Pará, 2012-05-07) SARAIVA, Augusto Cesar Fonseca; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
Unexpected failures in transformers led to the identification of copper sulphide formation, deposited on the conductors. The qualitative presence evaluation of corrosive sulfur in insulating mineral oil, led to a change in the Brazilian standards ABNT NBR 10505, which assesses the presence of corrosive sulfur in mineral oil, change in the time and test temperature to 150 °C / 48 hours. Performing the chemical speciation of organosulfur compounds (by gas chromatography coupled to mass spectrometry), were found 13 compounds in the Nynas oil and 9 compounds in the Petrobras oil. DBDS, which was found only in the Nynas oil, and it was the compound with the highest concentration. To perform the determination of the presence of DBDS in insulating mineral oil, a method by gas chromatography coupled to mass spectrometry was developed, and it was possible to quantify the amount of DBDS in insulating mineral oil samples derived from the power transformer. The passivation process by tolutriazol and benzotriazol, used as anticorrosive additives in the core of electrical equipament, was evaluated; after a while the effect of the addition of passivating agent becomes ineffective with time. The solution for the remotionl of DBDS from mineral oil was realized by using carbon nanotube reinforced by metallic matrix as agent to remove the DBDS. It was found that the adsorption agent was able to realize the complete DBDS remotion from insulating mineral oil up to a volume of 4000 mL (oil contaminated with DBD).
Acesso aberto (Open Access)
Desevolvimento de dispositivos eletrônicos orgânicos nano e micro-estruturados: memória volátil, sesores e fotocélulas
(Universidade Federal do Pará, 2011-02-14) REIS, Marcos Allan Leite dos; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this work, several nano and microstructured organic devices were developed based on molecules of 4-dimethyl amino azobenzene-2-carboxylic acid (Methyl Red – VM), C60 Fullerene, nanocomposite of Aluminum/Carbon Nanotubes (Al/NC) and polymers: Poly(3, 4- dioxithiophene ethylene)-poly(sulfonate stireno) – PEDOT-PSS and poly(3-hexiltiofeno) – P3HT. These devices are volatile memory, fuel sensors, thermal-piezoresisitive sensor and photocells, which were manufactured by spin-coating, drop casting and chemical vapor deposition, resulting in devices with planar or layer by layer geometry. Morphological, optical, electrical and thermal characterizations were performed on devices, resulting: (a) volatile memory with a bit retention time of 4.5 s, the characteristic curves of current vs. voltage with peak-valley ratios of 8: under a 10:1 voltage positive and negative electrical energized with electrical conductivity of 10-4 S / m (OFF state) to 3.10 S / m (ON) at room temperature, (b) fuel sensors like chemiresistor sensors characteristics with sensitivity to ethanol and gasohol in concentrations of 26.25 ppm, (c) thermal-piezoresistive sensor with polynomial relationship between temperature and electrical resistance, linear relationship between pressure and electrical resistance, more accurate than a K type thermocouple when compared to a mercury thermometer at room temperature, (d) photocells with better performance when doped by Methyl Red showed quantum efficiencies up to 0.04%, real power at 0.27 and power conversion efficiency of 2.0%. These results indicate that electronic devices developed showed a better performance in comparison to similar organics.
Acesso aberto (Open Access)
Efeito de interferência quântica no transporte eletrônico de dispositivos "quasi"-unidimensionais
(Universidade Federal do Pará, 2018-05-03) OLIVEIRA, Alexandre de Souza; SILVA, Shirsley Joany dos Santos da; http://lattes.cnpq.br/6060351208361634; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
The study of electronic transport in nano devices has been of great relevance in the last years, since the work of Aviran and Ratner, based on the properties of electrical conductivity in individual rectifying molecules under the action of an external electric field. The organic conjugated polymers in the pure state have low conductivity, but when doped, treated with reducing agents or connected to gold electrodes (Au) and subjected to an external electric field, they have a metallic behavior, that is, with high conductivity in line with experimental work. In this research we used devices composed of organic polymers conjugated in the pure state and also doped with chains containing simple (σ) and double (σ-π) type bonds, alternating between the carbons and these bound only to hydrogen atoms with gold electrodes (Au) connected at the ends of the individual molecules. This study was proposed for two types of electrodes: pyramid and plane. The model devices were optimized through the Extended Hückel Theory (EHT) and the computation of the electronic transport was performed using EHT combined with the Non-Equilibrium Green Function (NEGF). These devices are either quasi-1D or approximately linear structures and have been divided into two groups: the first, with odd numbers of carbon atoms from five (5) to nineteen (19) carbon atoms in their individual molecule (Group 1) and the second, with even numbers starting at six (6) going up to twenty (20) carbon atoms in its individual molecule (Group 2). The devices were subjected to two conditions: at low voltage, ranging from 0 to 0.1 Volt and then to high voltage, from 0 to 1.0 Volt. In order to compare the current and voltage (I - V) curves and the differential - voltage conductance (G - V) between low and high voltage results, the same voltage range was used, that is, from 0 to 0.1 Volt. For this work, the effects of destructive quantum interference (DQI) as well as constructive quantum interference (CQI) were analyzed. The effects of DQI are produced due to anti-resonance in the transmittance evidenced by unaccessed states observed in the transmission peaks, not allowing the transport to occur without presenting oscillations in the conductivity curve.
Acesso aberto (Open Access)
Eletrônica molecular via método híbrido DFT/FGNE em anéis fenilas acoplados a eletrodos metálicos de nanotubos de carbono: a regra de conformação e quiralidade molecular
(Universidade Federal do Pará, 2011-11-11) SILVA JÚNIOR, Carlos Alberto Brito da; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this thesis, we investigate in detail the electronic transport properties, conformation and symmetry of zz9 SWCN structures attached to phenyl rings (2, 3, 4 and 5) under the influence of external electric field (voltage) via hybrid method DFT type B3LYP 6-311G (d, p) combined with NEGF and Group Theory. We found a good relationship between: 1 - the chiral index () by Group Theory and the law of cos2 (, dihedral angle) for the geometry under the influence of external electric field because  only depends on the atomic positions () of conformations, and is also strongly correlated with current passing through the system; 2 - normalized conductance (G / Go) is proportional to cos2 in the region of the gap (EHOMO-ELUMO), ie, in regions where the resonance occurs negative differential resistance (NDR) and 3 - the Fowler-Northeim (FN) plot Vmin displays that occurs when the tail of a resonant transmission peak voltage enters the window, that is, when these structures is an NDR, NDR as the number of the IV plot is associated with the number Vmin of the FN plot and can be explained by the model of molecular transport line 4 - the barrier height (EF - EHOMO and ELUMO - EF) as a function of molecular length, 5 - Vmin as a function of barrier height (EF - EHOMO ) and the molecular length. Thus, one implies that the molecular conformation plays a major role in determining the transport properties of the junction, suggests that the second law of cos2 is a more general applicability regardless of the nature of the electrodes; 3 serves as a spectroscopic tool and also to identify the molecule at the junction, 4 and 5 as the molecular length reaches a certain value (1.3 nm) the Vmin remains virtually unchanged. The results showed that the structural properties (geometric) undergo significant changes with increasing external electric field that are in good agreement with the values found in literature. The behavior of I-V curves and G/Go-V lose their linear dependence to give rise to a nonlinear behavior with the appearance of NDR. This point reveals the structural modifications suffered by the system. The I-V plot confirmed the statements that were made through the structural analysis for the system considered and showed how it gives the load flow analysis systems.
Acesso aberto (Open Access)
Estados ligados de Majorana em nanodispositivo com ponto quântico acoplado à cadeia de átomos em zigue zague sobre supercondutor topológico.
(Universidade Federal do Pará, 2018-10-11) BEIRÃO, Antonio Thiago Madeira; SILVA, Shirsley Joany dos Santos da; http://lattes.cnpq.br/6060351208361634; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
The research in condensed matter physics with insulators and superconductors topological has contributed greatly to the characterization of the surface properties and modes zero in nanowires. We investigate theoretically, through the recursive Green’s function approach, the electron transport through the T-shaped quantum dot (PQ) with a single level and spinless, connected to a zigue zague chain and coupled to a p-wave superconductor. This model is an extension of the Kitaev chain for a network triangular of finite-size with for three, four, and five sites. We find that the Majorana zero modes can be tuned through the coupling parameters of the device and the linear conductance show both the Majorana Bound States (MBS) in topological phase and in the general topological phase maximally robust. This more realistic model allows the detection of MBS through of the control of the parameters governing the electronic tunneling and can be helpful for relevant experiments. Keywords: Majorana Fermions, recursive Green’s function approach, Kitaev chain, class of electronic nanodevices, Quantum Dot, T-shaped, Qubit, Majorana Bound States (MBS).
Acesso aberto (Open Access)
Estudo do transporte eletrônico em nanoestruturas baseadas em carotenoides e tétrades com fulereno C60
(Universidade Federal do Pará, 2013-04-09) ALEIXO, Vicente Ferrer Pureza; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this work it is presented a theoretical study on the electronic structure of a fullerene molecule (C60) with junctions in four terminals based on groups electron donors. tetrathiafulvalene (TTF) – and groups acceptors of electrons – fenilpropanodinilla (FPP) and molecular devices based on Carotenoid derivatives. The transport mechanism investigated for the carotenoids derivatives were utilized for better understanding of Fowler-Nordheim (FN) and Millikan-Lauritsen (ML) plots for the systems based in fullerene C60. In all cases it was possible to confirm that the Millikan- Lauritsen (ML) analysis empirical is also sufficient to describe all aspects the transition voltage spectroscopy (TVS). To study this class of systems, optimize the geometry systematically and observe the electronic transfer calculated by Hartree-Fock and Density Functional Theory (DFT). The results show through a detailed analysis of the molecular charge rearrangement due to an external electric field shows that the charge transport is directly on to the type of junction that this system is submitted of form that the applied voltage suffices to create a saturation potential in the systems in study: fullerene C60 with three terminals of tetrathiafulvalene and one terminal of fenilpropanodinilla (C60-(TTF)3-FPP); fullerene C60 with four terminals of fenilpropanodinilla (C60-(FPP)4). The particularity observed in C60-(FPP)4 is the disposal of the structure to operate with rectifying character for the electronic transport in the presence of orthogonal electric field to terminal data. The results show that we have a Molecular rectifier that works as a macroscopic rectifier.
Acesso aberto (Open Access)
Modelamento do transporte eletrônico em dispositivos moleculares
(Universidade Federal do Pará, 2013-08-29) GRANHEN, Ewerton Ramos; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In the present work we simulate the transport properties and absorption spectra of the organic compound ethyl red. This is the first theoretical study of a specific pH indicator utilized as nano-device, based on quantum theory and a non-diffusive transport model. The charge distribution along the molecule is calculated via Ab initio technique as a function of an external electric field. Based on a resonant multilevel model we also calculate the current against bias voltage. Both the charge accumulation and the current present similar behavior, like resonant type conduction and asymmetric charge–voltage and current–voltage curves. Our main results suggest that the present system could operate as a bidirectional molecular transistor. We spread this methodology to another molecular device however, with three-terminal. For this system, our main finding is a negative differential resistance (NDR) in the charge Q as a function of an external electric field. To explain this NDR effect we apply a phenomenological capacitive model based on a quite general system composed of many localized levels (that can be LUMOs of a molecule). The capacitance accounts for charging effects that can result in Coulomb blockade (CB) in the transport. We show that this CB effect gives rise to a NDR for a suitable set of phenomenological parameters, like tunneling rates and charging energies. The NDR profile obtained in both Ab initio and phenomenological methodologies are in close agreement.
Acesso aberto (Open Access)
Nanofabricação, caracterização e modelagem de dispositivos optoeletrônicos nanoestruturados de corantes orgânicos
(Universidade Federal do Pará, 2008-07-28) COSTA, Sheila Cristina dos Santos; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
To better understand the process of miniaturization and the behavior of molecular structures under this effect we appeal to the calculations based in Quantum Mechanics (QM) with the purpose to corroborate theoretical and experimental data as electronic structure as well as electric properties. Another method sufficiently known consists simulate solute-solvent effect through the probabilistic Monte Carlo (MC) method. Of ownership of these computational tools we develop simulations QM/MC that translate the behavior of organic composites Methyl Red (MR) and 1,4-bis (5-phenyl-2-oxazolyl) benzene (POPOP), when suffer structural changes, modification in the optic answers, etc., due miniaturization processes, environment variations, external actions. The Methyl Red composite is known as a sensible dye of pH variation and meets in the basic and acid (isoeletrônico, zwitteriônico) forms is classified as azo-composite for the presence of (– N = N –) bonding in its structure. The POPOP is a luminescent dye of intense fluorescence in the blue region of the UV-Visible spectrum; we stand out that to investigate the functional and mannering principles of this structure we consider two conformational structures protonated derivatives of POPOP: C1 (N+) and C2 (N+). Initially all organic composites structures of MR and POPOP had been optimized through of the quantum methods: semiempirical PM3 (Parametric Method 3) and ab initio HF (Hartree-Fock) and DFT (Density Functional Theory), getting the geometric parameters and the conformations of lowest energy of each system, for the study of the electronic structure. Sequentially, two distinct stages of simulation had been used for the study of composites: 1st) The MR and POPOP structures had been optimized through the method PM3 + External Electric Field (the EEC), getting the geometric parameters and charge parameters. We use this method with the purpose to simulate the electronic transport properties of organic composites as the electric reply characterized by the charge transport (e) curve in function of the variation of the tension (V) in the structures. By means of the electric reply [(e) × V] we characterize this function to use them in nanostructured devices, as photodiodes, photodetector, solar cells, etc. The 2nd stage consists of simulate organic composites through the Monte Carlo method, to investigate its behaviors in liquid. The systems distinct consist of the addition of VM (basic, acid: isoelectronic and zwitterionic) and POPOP [C1 (N+) and C2 (N+)] in 1000 water molecules to analyze the solute-solvent interactions for development of interchange systems optoelectronic systems as sensory. In MC simulation had been carried 1×1010 steps MC for both thermalization and equilibrium stages in NVT ensemble. Generate a set of 105 configurations, from these we select a set reduced of 103 descorrelantion configurations of which we obtain the convergence average of the electronic transitions π→π*. The convergence average of the electronic transitions π→π* for MR: basic s of 434.33 ± 1,0 [436,34 ± 2,0 nm], isoelectronic 485,80 nm ± 2,0 nm [480,66 nm ± 3,0 nm], and zwitterionic [502.13 nm ± 3.0 nm]; for POPOP C1 [361,25 nm ± 2,0 nm], C1(NP+P) [485.0 ± 26.0 nm], C2 [355,39 nm ± 3,0 nm] and C2(NP+P) [472.0 ± 24.0 nm]. The averages of the electronic transitions π→π* had been obtained through semiempirical ZINDO/S-CIS (Zerner Intermediate Neglect of Orbital Diffential Spectroscopic - Configurations Interaction, Single excitation) method that better translates the spectroscopic parameters of the organic molecules in the UV-visible region. Experimentally we develop two distinct types of systems through of the techniques: Sol-Gel that consists in the incorporation of composites in host matrix of APP (Aluminum Polyphosphate), and Blendes that consist in the manufacture of volume devices within active monolayer. The MR and POPOP composites had been diluted in hybrid solution (10% etanol + 90% water), aliquots of these solutions had been incorporated in the synthesis of APP/Gel. The samples obtain for the Sol-Gel process had been submitted to the variation pH and characterized by spectroscopy of absorption in the UV-Visible region, whose bands of maximum absorption are of [431 nm, 513 nm, 511 nm] for MR and [358 nm, 511 nm and 472 nm] for POPOP and values of [355 nm, 361 nm] for POPOP in solution, that corroborate the theoretical results from the averages of the electronic transitions π→π*. The monolayer devices of MR and POPOP had been manufactured by overlapped of thin films in vitreous substrate/FTO (1st electrode)/PEDOT/P3HT/ active monolayer -Aluminum (2nd electrode) and characterized electrically for charge density (J) in function of applied voltage (V), under dark current and under 550 nm monochromatic light. The MR devices present curve (J×V) characteristic of a rectifier junction p-n of higher electric current signal under reverse polarization for dark current, being this signal intensified under light 550 nm; under forward bias the device presents the same behavior how much to the current signal, this is intensified when measured on monochromatic light (550 nm) in comparison with dark current, however under reverse polarization and forward bias the device presents curve characteristic (J×V) analogous of the conventional photodetector and diode tunnel. For POPOP intensification of the electric chain signal is observed under forward bias and reverses when the devices are under monochromatic light in comparison with measures made under dark current, in way that the characteristic curve (J×V) has similar behavior of the conventional photodiodes. The theoretical-experimental results of the electric (J×V) properties of composites had presented similar behaviors in the voltage range [- 2.0 V – 2.97 V] for MR and [- 2.86 V - 2.86V] for POPOP. We development a complete study with polymers of low bandgap (gap 1 eV) based in monomers bridges composition for carbon forming polymeric chains had been investigated by the methods AM1 (Austin Model 1), PM3 and DFT [B3LYP/6-31G] to corroborated the results of the oligomers of CDM (4-dicyano methyllene-4H-cyclopente [2.1 - 3: 4-b'] dithiophene) and BDT (1,3-benzodithiole-4H-cyclopenta [2,1-b: 3,4-b'] dithiophene), derived from the ditiophene. The results show that the growth of the polymeric chain formed by monomers of CDM and BDT provokes the reduction bandgap of the oligomers, analogous behavior to the polymers based on (3-alkylthiophenes) whose electronic transition π→π* energy is of 1.67 eV, the maximum absorption of the CDM and BDT are of 1.28 eV and 1,73 eV, respectively The theoretical methods used in this study to describe satisfactorily this behavior, whose maximum absorption is of approximately 1,28 eV for CDM and 1,74 eV for BDT, these results had been obtain from the polymeric chains formed by 5 monomers units, demonstrating that the geometric conformations of the polymeric chains simulated are equiprobability, proving the trustworthiness of the methods used in our investigation. In general lines, the results presents to demonstrate that the organic composites investigated are good candidates for employ in nanostructured organic devices applied in the molecular electronics and new technology of materials.
Acesso aberto (Open Access)
Transporte de portadores minoritários que justificam o regime de ressonância eletrônica em sistemas de carbynes
(Universidade Federal do Pará, 2016-02-24) OLIVEIRA, Antonio Wanderley; CAVALCANTE, Gervásio Protásio dos Santos; http://lattes.cnpq.br/2265948982068382; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
One of the goals for the expansion of knowledge in molecular electronics may be found in the Project related to the creation of nanoscale circuits based on nonlinear current–voltage characteristics composed by molecules connected to metallic electrodes under the action of an external electric field. The development of molecular electronic devices using systems exhibiting similar feature as intrinsic semiconductor materials is one of the goals to be achieved by an extensive research in nanotechnology. Thus, this work aims at expanding of knowledge not only of the electronic transport, but also the physical features that justify the resonant regime for electronic transport, such as conductance and Transition Voltage Spectroscopy. We theoretically investigate the electronic charge transport in a molecular system composed by carbyne structures taking into account the variations in the bonds −𝐶≡𝐶− type (simple and triple bonds for each carbon). Ab initio calculations approximations are performed to investigate the distribution of electron states over the molecule in the presence of an external electric field. This new nanoelectronic device raise up advantage for the design of large 1D hybrid organic/metallic circuits with an increased electronic flow that is importante for the needs of nanotechnology.

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