Usinagem do alumínio da classe 6005 com uso de ferramenta cerâmica

The machining process is so much important in the economic world. Many machining parameters have been studied to maximize results, in terms of cost and lifetime. (decrease of cutting tool wear, improved surface finish, among others). The objective of this study is to evaluate the wear of a ceramic tool in the machining of the aluminum alloy 6005 A. The analysis of the wear of the cutting tools is very important due to its big impact on the final finishing of the piece as a whole. The evaluation took place in two stages, first it was done a detailed study of the literature of the whole machining process, where the study of the formation and swarf classification were among the most important steps in this phase. The second step consisted in the machining of the piece of aluminum 6005 A with a ceramic cutting tool constituded of aluminum oxide and magnesium oxide with silicon carbide impregnation. The swarf generated in this process was then photographed with a Zeiss optical microscope and analyzed for its size and shape. Through this comparison it was concluded that the swarf are generated shear swarfs, shaped like a tangled, fragmented and arcs connected, thus classifying the material as medium difficulty machining. Through the image analysis tool it was concluded that the parameter of lower wear was the: Vc = 500m / min, f = 0.10mm / rev and ap = 0.5mm

Desenvolvimento de células solares de perovskita baseadas em filmes de óxidos nanoestruturados

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nanopartículas de CeO2 modificadas com Er obtidas pelo método hidrotermal microondas: estudo fotoluminescente

The development of nanostructured materials have aroused great interest of the industries all over the country, since they enable the development of devices that can be used as gate insulators on silicon transistors, electrochromic devices, solid electrolyte oxygen sensors and as a photoluminescent materials . In this project, it is proposed to investigate the optical properties of CeO2 modified with rare earth Er processed in hydrothermal-microwave. The synthesis of one-dimensional nanostructures (1D) was measured from dilute aqueous solutions of acids and salts of starting reagents in the presence of chemical basis, after these aqueous solutions were processed on hydrothermal-microwave to particle growth. The particles obtained after processing were characterized by X-ray Diffraction, Rietveld Analysis and Raman Spectroscopy. The particle morphology was observed by scanning electron microscopy with field emission gun. The synthesis of 1D nanostructures are evaluated for different surfactants and starting precursors (ceria different salts), pH, temperature and pressure which can modify the morphology of the nanostructures. Combining laboratory experiments and theoretical calculations it was desired to understand the organization of the nanoparticles and their resulting structure. Strict control of chemical homogeneity, crystal structure, microstructure and interaction of the CeO2 cluster with different surfactants using the Hartree-Fock method, was intended to obtain properties compatible with their use in catalysts and optical devices. The use of mineralizer agent KOH and 8 minutes of processing time synthesis conditions were chosen to evaluate the effect of Er dopant. It has been proved that this doping with rare earth increases the photoluminescent properties of the compound obtained without change the structural and morphological propreties of ceria

Usinagem do alumínio da classe 6005 com uso de ferramenta cerâmica

The machining process is so much important in the economic world. Many machining parameters have been studied to maximize results, in terms of cost and lifetime. (decrease of cutting tool wear, improved surface finish, among others). The objective of this study is to evaluate the wear of a ceramic tool in the machining of the aluminum alloy 6005 A. The analysis of the wear of the cutting tools is very important due to its big impact on the final finishing of the piece as a whole. The evaluation took place in two stages, first it was done a detailed study of the literature of the whole machining process, where the study of the formation and swarf classification were among the most important steps in this phase. The second step consisted in the machining of the piece of aluminum 6005 A with a ceramic cutting tool constituded of aluminum oxide and magnesium oxide with silicon carbide impregnation. The swarf generated in this process was then photographed with a Zeiss optical microscope and analyzed for its size and shape. Through this comparison it was concluded that the swarf are generated shear swarfs, shaped like a tangled, fragmented and arcs connected, thus classifying the material as medium difficulty machining. Through the image analysis tool it was concluded that the parameter of lower wear was the: Vc = 500m / min, f = 0.10mm / rev and ap = 0.5mm

Sulfur Radicals as Tethers for the Adsorption of Aromatic Molecules on Silicon Surface

In this work we employ the state of the art pseudopotential method, within a generalized gradient approximation to the density functional theory, to investigate the adsorption process of benzenethiol and diphenyl disulfide with the silicon (001) surface. A direct comparison of different adsorption structures with Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) allow us to identify that benzenethiol and diphenyl disulfide dissociatively adsorb on the silicon surface. In addition, theoretically obtained data suggests that the C6H5SH:Si(001) presents a higher Schottky barrier height contact when compared to other similar aromatic molecules.

Spectroscopic investigation and heat generation of Yb3+/Ho3+ codoped aluminosilicate glasses looking for the emission at 2 μm

Energy transfer (ET) and heat generation processes in Yb3+/Ho3+-codoped low-silica calcium aluminosilicate glasses were investigated using thermal lens (TL) and photoluminescence measurements looking for the emission around 2.0 μm. Stepwise ET processes from Yb3+ to Ho3+, upon excitation at 0.976 μm, produced highly efficient emission in the mid-infrared range at around 2.0 μm, with high fluorescence quantum efficiency (η1 ∼ 0.85 and independent of Ho3+ concentration) and relatively very low thermal loading (<0.4) for concentration up to 1.5% of Ho2O3. An equation was deduced for the description of the TL results that provided the absolute value of η1 and the number of emitted photons at 2.0 μm per absorbed pump photon by the Yb3+ ions, the latter reaching 60% for the highest Ho3+ concentration. These results suggest that the studied codoped system would be a promising candidate for the construction of photonic devices, especially for medical applications.

A simple-versatile approach to achieve all-Si-based optical micro-cavities

At present, solid thin films are recognized by their well established and mature processing technology that is able to produce components which, depending on their main characteristics, can perform either passive or active functions. Additionally, Si-based materials in the form of thin films perfectly match the concept of miniaturized and low-consumption devices-as required in various modern technological applications. Part of these aspects was considered in the present work that was concerned with the study of optical micro-cavities entirely based on silicon and silicon nitride thin films. The structures were prepared by the sputtering deposition method which, due to the adopted conditions (atmosphere and deposition rate) and arrangement of layers, provided cavities operating either in the visible (at ~ 670 nm) or in the near-infrared (at ~ 1560 nm) wavelength ranges. The main differential of the work relies on the construction of optical microcavities with a reduced number of periods whose main properties can be changed by thermal annealing treatments. The work also discusses the angle-dependent behavior of the optical transmission profiles as well as the use of the COMSOL software package to simulate the microcavities.

Estudo da cinética da tirosinase imobilizada em nanopartícula de sílica com obtenção de revestimento de eumelanina

Melanina é um polímero constituído por uma grande heterogeneidade de monômeros tendo como característica comum a presença de grupos indóis. Por outro lado, a eumelanina produzida pela oxidação enzimática da tirosina é um polímero mais simples constituído principalmente de monômeros 5,6-dihidroxindol (DHI) e de indol-5,6-quinona (IQ). Tirosinase é a enzima chave na produção de melanina, sendo que a sua atividade cinética é medida em função da formação do intermediário dopacroma. Nanopartículas (NPs) de sílica são partículas nanométricas compostas de oxido de silício e são obtidas pelo processo sol-gel desenvolvido por Stöber de hidrólise e condensação de tetraetilortosilicato (TEOS), usando etanol como solvente em meio alcalino. As NPs foram funcionalizadas com 3-Aminopropiltrietoxissilano (ATPES) e depois com glutaraldeído. Este último permitiu a imobilização da tirosinase na superfície da sílica. Caracterizamos as NPs antes e após a reação da enzima, a atividade catalítica da enzima ligada à NP e o mecanismos de formação de melanina na superfície da sílica. As NPs foram caracterizadas por espectrofotometria de absorção e de reflectância, termogravimetria e microscopia eletrônica. A síntese da NP de sílica retornou partículas esféricas com 55nm de diâmetro e a funcionalização da partícula mostrou modificar eficientemente a sua superfície. A imobilização da tirosinase por ligação covalente foi de 99,5% contra 0,5% da adsorção física. A atividade da tirosinase foi caracterizada pela formação de dopacroma. O Km da enzima imobilizada não sofreu alteração em comparação com a tirosinase livre, mas a eficiência catalítica - que considera a eficiência recuperada - foi de apenas 1/3 para a enzima ligada covalentemente, significando que 2/3 das enzimas ligadas não estão ativas. Obtivemos NPs revestidas com melanina a partir de oxidação de tirosina solubilizada em duas preparações: NP com tirosinase ligada covalentemente na superfície e NP funcionalizada com glutaraldeido dispersa em solução de DHI e IQ. O revestimento de melanina foi na forma de um filme fino com espessura ~1,9nm, conferindo perfil de absorção luminosa equivalente ao da própria melanina. Mostramos que o mecanismo de polimerização passa pela oxidação da tirosina pela tirosinase, que gera intermediários oxidados (principalmente DHI e IQ) que vão para solução (mesmo quando a tirosinase está ligada covalentemente na sílica). Estes intermediários ligam-se ao glutaraldeido e a superfície da sílica passa a funcionar como ambiente de polimerização da melanina.

Produção e caracterização de guias de onda dopados com terras-raras contendo nanopartículas semicondutoras.

O presente trabalho tem como objetivo estudar a produção e caracterização de filmes finos do tipo GeO2-Bi2O3 (BGO) produzidos por sputtering-RF com e sem nanopartículas (NPs) semicondutoras, dopados e codopados com íons de Er3+ ou Er3+/Yb3+ para a produção de amplificadores ópticos. A produção de guias de onda do tipo pedestal baseados nos filmes BGO foi realizada a partir de litografia óptica seguida por processo de corrosão por plasma e deposição física a vapor. A incorporação dos íons de terras-raras (TRs) foi verificada a partir dos espectros de emissão. Análises de espectroscopia e microscopia foram indispensáveis para otimizar os parâmetros dos processos para a construção dos guias de onda. Foi observado aumento significativo da luminescência do Er3+ (região do visível e do infravermelho), em filmes finos codopados com Er3+/Yb3+ na presença de nanopartículas de Si. As perdas por propagação mínimas observadas foram de ~1,75 dB/cm para os guias pedestal em 1068 nm. Para os guias dopados com Er3+ foi observado aumento significativo do ganho na presença de NPs de silício (1,8 dB/cm). O ganho óptico nos guias de onda amplificadores codopados com Er3+/Yb3+ e dopados com Er3+ com e sem NPs de silício também foi medido. Ganho de ~8dB/cm em 1542 nm, sob excitação em 980 nm, foi observado para os guias pedestal codopados com Er3+/Yb3+ (Er = 4,64.1019 átomos/cm3, Yb = 3,60.1020 átomos/cm3) com largura de 80 µm; para os guias codopados com concentração superior de Er3+/Yb3+ (Er = 1,34.1021 átomos/cm3, Yb = 3,90.1021 átomos/cm3) e com NPs de Si, foi observado aumento do ganho óptico de 50% para guia com largura de 100 µm. Os resultados apresentados demonstram que guias de onda baseados em germanatos, com ou sem NPs semicondutoras, são promissores para aplicações em dispositivos fotônicos.

Estudo de transistores de tunelamento induzido por efeito de campo (TFET) construídos em nanofio.

Esse trabalho de mestrado teve como estudo o transistor Túnel-FET (TFET) fabricado em estrutura de nanofio de silício. Este estudo foi feito de forma teórica (simulação numérica) e experimental. Foram estudadas as principais características digitais e analógicas do dispositivo e seu potencial para uso em circuitos integrados avançados para a próxima década. A análise foi feita através da extração experimental e estudo dos principais parâmetros do dispositivo, tais como inclinação de sublimiar, transcondutância (gm), condutância de saída (gd), ganho intrínseco de tensão (AV) e eficiência do transistor. As medidas experimentais foram comparadas com os resultados obtidos pela simulação. Através do uso de diferentes parâmetros de ajuste e modelos de simulação, justificou-se o comportamento do dispositivo observado experimentalmente. Durante a execução deste trabalho estudou-se a influência da escolha do material de fonte no desempenho do dispositivo, bem como o impacto do diâmetro do nanofio nos principais parâmetros analógicos do transistor. Os dispositivos compostos por fonte de SiGe apresentaram valores maiores de gm e gd do que aqueles compostos por fonte de silício. A diferença percentual entre os valores de transcondutância para os diferentes materiais de fonte variou de 43% a 96%, sendo dependente do método utilizado para comparação, e a diferença percentual entre os valores de condutância de saída variou de 38% a 91%. Observou-se também uma degradação no valor de AV com a redução do diâmetro do nanofio. O ganho calculado a partir das medidas experimentais para o dispositivo com diâmetro de 50 nm é aproximadamente 45% menor do que o correspondente ao diâmetro de 110 nm. Adicionalmente estudou-se o impacto do diâmetro considerando diferentes polarizações de porta (VG) e concluiu-se que os TFETs apresentam melhor desempenho para baixos valores de VG (houve uma redução de aproximadamente 88% no valor de AV com o aumento da tensão de porta de 1,25 V para 1,9 V). A sobreposição entre porta e fonte e o perfil de dopantes na junção de tunelamento também foram analisados a fim de compreender qual combinação dessas características resultariam em um melhor desempenho do dispositivo. Observou-se que os melhores resultados estavam associados a um alinhamento entre o eletrodo de porta e a junção entre fonte e canal e a um perfil abrupto de dopantes na junção. Por fim comparou-se a tecnologia MOS com o TFET, obtendo-se como resultado um maior valor de AV (maior do que 40 dB) para o TFET.

Estudo de camadas anti-reflectoras para células solares

Trabalho de projecto de mestrado, Engenharia da Energia e Ambiente, Universidade de Lisboa, Faculdade de Ciências, 2016

Mecanismo de tolerância a falhas através de escalonamento para uma arquitetura reconfigurável de grão grosso

The continuous evolution of integrated circuit technology has allowed integrating thousands of transistors on a single chip. This is due to the miniaturization process, which reduces the diameter of wires and transistors. One drawback of this process is that the circuit becomes more fragile and susceptible to break, making the circuit more susceptible to permanent faults during the manufacturing process as well as during their lifetime. Coarse Grained Reconfigurable Architectures (CGRAs) have been used as an alternative to traditional architectures in an attempt to tolerate such faults due to its intrinsic hardware redundancy and high performance. This work proposes a fault tolerance mechanism in a CGRA in order to increase the architecture fault tolerance even considering a high fault rate. The proposed mechanism was added to the scheduler, which is the mechanism responsible for mapping instructions onto the architecture. The instruction mapping occurs at runtime, translating binary code without the need for recompilation. Furthermore, to allow faster implementation, instruction mapping is performed using a greedy module scheduling algorithm, which consists of a software pipeline technique for loop acceleration. The results show that, even with the proposed mechanism, the time for mapping instructions is still in order of microseconds. This result allows that instruction mapping process remains at runtime. In addition, a study was also carried out mapping scheduler rate. The results demonstrate that even at fault rates over 50% in functional units and interconnection components, the scheduler was able to map instructions onto the architecture in most of the tested applications.

Análise experimental de danos em pistões de motor à gasolina operando com adição de gás hidróxi

The addition of hydrogen gas as an alternative fuel source has been widely used, as well reported in scientific literature. Today, several experiments are underway for the use of hydrogen generators (electrolysers) demand for motor vehicles. In all these products their ads manufacturers claim that this provides a reduction of fuel consumption, reduces the emission levels of toxic gas by the discharge and improves engine life. This research analyzes the physical structure of engine components using electrolysis on demand. To this end, a stationary system was fitted with a power generator of electricity, drum roller and adapted two electrolyzers: a dry cell and wet cell other. In steps observation were consumption analyzes in four work load ranges and observing the piston engine, which has been cut and analyzed by Optical Microscopy (OM), Scanning Electron Microscopy and Dispersive Energy (SEM-EDS), X – Ray Diffraction (XRD) and Confocal Microscopy, the stationary system in each step. The results showed a considerable reduction in fuel consumption and a high corrosion in the original factory piston constituted of aluminum-silicon alloy. As corrosion barrier was made a plasma nitriding in the piston head, which proved resistant to attack by hydrogen, although it has presented evidence also, of having been attacked. It is concluded that the automotive electrolysers can be a good choice in terms of consumption and reducing toxic gas emissions, but the material of the combustion chambers of vehicles must be prepared for this purpose.

Prospecção tecnológica de células fotovoltaicas para energia solar

Solar energy presents itself as an excellent alternative for the generation of clean, renewable energy. This work aims to identify technological trends of photovoltaic cells for solar energy. The research is characterized, in relation to nature, to be applied; regarding the approach is qualitative and quantitative; with respect to the objectives, it is exploratory and descriptive; concerning the methodological procedure is considered a bibliographic research with a case study in the case of solar photovoltaic sector. The development of this research began with a literature review on photovoltaic solar energy and technology foresight. Then it led to the technology mapping of photovoltaic solar cells through the analysis of articles and patents. It was later performed the technological prospecting of photovoltaic cells for solar energy through the Delphi method, as well as the construction of the current plan and future technology of photovoltaic cells for the current scenario, 2020 and 2025. The results of this research show that the considered mature technologies (silicon mono and multicrystalline) will continue to be commercially viable within the prospected period (2020-2025). Other technologies that are currently viable (amorphous silicon, cadmium telluride and copper indium selenide / Copper indium gallium diselenide-), may not submit the same condition in 2025. Since the cells of silicon nanowires, dye-sensitized and based on carbon nanostructure, which nowadays are not commercially viable, may be part of the future map of photovoltaic technologies for solar energy.

Novos protocolos teóricos utilizados nos estudos das ligações hidrogênio-hidrogênio, na estabilidade do tetraedrano, seus derivados e das reações de diels-alder e na quantificação da afinidade de fármacos

This thesis was performed in four chapters, at the theoretical level, focused mainly on electronic density. In the first chapter, we have applied an undergraduate minicourse of Diels-Alder reaction in Federal University of Rio Grande do Norte. By using computational chemistry tools students could build the knowledge by themselves and they could associate important aspects of physical-chemistry with Organic Chemistry. In the second chapter, we studied a new type of chemical bond between a pair of identical or similar hydrogen atoms that are close to electrical neutrality, known as hydrogen-hydrogen (H-H) bond. In this study performed with complexed alkanes, provides new and important information about their stability involving this type of interaction. We show that the H-H bond playing a secondary role in the stability of branched alkanes in comparison with linear or less branched isomers. In the third chapter, we study the electronic structure and the stability of tetrahedrane, substituted tetrahedranes and silicon and germanium parents, it was evaluated the substituent effect on the carbon cage in the tetrahedrane derivatives and the results indicate that stronger electron withdrawing groups (EWG) makes the tetrahedrane cage slightly unstable while slight EWG causes a greater instability in the tetrahedrane cage. We showed that the sigma aromaticity EWG and electron donating groups (EDG) results in decrease and increase, respectively, of NICS and D3BIA aromaticity indices. In addition, another factor can be utilized to explain the stability of tetra-tert-butyltetrahedrane as well as HH bond. GVB and ADMP were also used to explain the stability effect of the substituents bonded to the carbon of the tetrahedrane cage. In the fourth chapter, we performed a theoretical investigation of the inhibitory effect of the drug abiraterone (ABE), used in the prostate cancer treatment as CYP17 inhibitor, comparing the interaction energies and electron density of the ABE with the natural substrate, pregnenolone (PREG). Molecular dynamics and docking were used to obtain the CYP1ABE and CYP17-PREG complexes. From molecular dynamics was obtained that the ABE has higher diffusion trend water CYP17 binding site compared to the PREG. With the ONIOM (B3LYP:AMBER) method, we find that the interaction electronic energy of ABE is 21.38 kcal mol-1 more stable than PREG. The results obtained by QTAIM indicate that such stability is due a higher electronic density of interactions between ABE and CYP17