O presente trabalho utiliza o método Design Construtal para desenvolver o estudo numérico de uma configuração de caminhos de alta condutividade de geometria trifurcada que minimiza a resistência ao fluxo de calor, quando a área do caminho trifurcado é mantida constante. O objetivo deste trabalho é o estudo da influência da geometria sobre o desempenho térmico do sistema bem como a otimização do mesmo, assim obtendo uma configuração que minimiza a resistência térmica para cada condição imposta. São apresentadas as considerações e hipóteses utilizadas para a análise, obtendo a equação do calor regente e as condições de contorno do problema, bem como a função objetivo. Para a solução numérica da equação da condução do calor, é utilizado o software MATLAB ®, especificamente as ferramentas PDETOOL, Partial Differential Equations Tool, e GA, Algoritmo Genético. A resistência térmica é minimizada para cada grau de liberdade. A cada nível de otimização, a influência do grau de liberdade em questão é estudada, obtendo um mapeamento da importância de cada grau de liberdade sobre o sistema trifurcado. Também são obtidas as configurações ótimas para diferentes frações de área. Posteriormente, é estudado o comportamento da configuração ótima do sistema para diferentes temperaturas do final das bifurcações do sistema, mostrando que, para as temperaturas estudadas neste trabalho, a configuração ótima não se altera, apenas a resistência térmica, com a alteração na temperatura do sumidouro direito sendo mais influente sobre essa, seguida do sumidouro central e, por fim, do sumidouro esquerdo. Finalmente, este trabalho mostra, com esses resultados, que a geometria ótima é aquela que melhor distribui as imperfeições do sistema, de acordo com o princípio da ótima distribuição das imperfeições e, também, possui robustez quanto às pequenas imperfeições inseridas no sistema. / The present work employs Constructal Design method to develop a numerical study of a triforked high conductivity pathway that minimizes the heat flow resistance when the triforked pathway area is kept constant. The objective of this work is the study of the influence of the geometry over the thermal performance of the system as well as the optimization of the latter, thus obtaining a configuration that minimizes the thermal resistance for each imposed condition. The considerations and hypothesis for the analysis are shown, obtaining a reigning heat equation and boundary conditions for the system, as well as the objetctive function (minimization of the maximum temperature). For the numerical solution of the heat conduction equation, it is utilized MATLAB ® software, specifically the PDETOOL, Partial Differential Equations Tool, and GA, Genetic Algorithm, toolboxes. The thermal resistance is minimized for every degree of freedom. In each level of optimization, the influence of the degree of freedom in question is studied, obtaining a mapping of the importance of each degree of freedom over the performance of the triforked pathway. Optimal configurations are also obtained for different area fractions. Posteriorly, the behavior of the optimal geometry is studied for different temperatures of the branches of the system. Results show that, for the temperatures studied in this work, the optimal configuration does not change, only the thermal resistance, with the increase of temperature of the right sink being more influential over it, followed by the temperature of the middle sink and, at last, the temperature of the left sink. Finally, this work shows, with these results, that the optimal geometry is the one that better distributes the imperfections of the systems, which is in accordance to the principle of the optimal distribution of imperfections, while possessing a certain robustness over small imperfections inserted in the system.

Made available in DSpace on 2014-06-11T19:31:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-10Bitstream added on 2014-06-13T18:41:26Z : No. of bitstreams: 1 fuzarijunior_gc_dr_ilha.pdf: 2491694 bytes, checksum: c09e7e7eb16e8b1d4eed262b46a092d8 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / No presente trabalho foram preparados filmes compósitos de PZT/PVDF com PAni por mistura mecânica e posterior prensagem a quente. A PAni foi inserida de duas maneiras distintas no compósito: recobrindo parcialmente os grãos cerâmicos; e disposta separadamente aos grãos. Foram controladas as razões volumétricas dos constituintes dos compósitos e a condutividade da PAni que pode ser controlada pelo seu grau de protonação. A grande vantagem de sistemas com grãos recobertos é garantir a proximidade de canais de condução (ou polarização) com o grão, além de impossibilitar a percolação da fase condutora se o compósito exibir conectividade 0-3. Para o caso das amostras preparadas com PAni (dopada) disposta separadamente do grão, quando o limiar de percolação é alcançado, torna-se impossível o processo de polarização. Para compósitos com grãos recobertos, os melhores resultados em relação às propriedades de eletroatividade (e polarização) são encontrados acima da concentração crítica, onde o padrão de conectividade 0-3 já não é válido. As grandes vantagens obtidas usando compósitos com condutividade controlada são principalmente o tempo mais curto e o campo elétrico inferior usado para a polarização. Os resultados mostraram que é possível obter filmes compósitos com baixo conteúdo de cerâmica recoberta, que apresentem boas propriedades de eletroatividade e flexibilidade. Como uma de suas possíveis aplicações, o compósito mostrou boas propriedades como sensor fototérmico. / In the present work composite films of PZT-PAni/PVDF were prepared hot pressing the mixture of components mechanically mixed. The PAni was inserted into the composite by two different ways: partially recovering the ceramic grains; and dispersed separately from the ceramic grains. Volumetric ratio of the single phases of the composite and the electrical conductivity of the PAni were controlled. The advantage of systems with ceramic grains partially recovered is that it allow the neighborhood of conduction channels (or poling) with the ceramic grain, besides to prevent the percolation of the conducting phase if the composite exhibit 0-3 connectivity. For the case of samples prepared with doped PAni dispersed separately from the ceramic grain, the poling process is not able when the limiar of percolation is reached. For composites with partially recovered grains the best results concerned to the electroactive properties (and polarization) are obtained over the critical concentration where the 0-3 connectivity pattern is not valid. The advantages obtained using composite with controlled conductivity are mainly the poling short time of polarization and the lower electric field. The results showed the possibility to obtain composite films with low content of recovered ceramic grain, which shows good electroactive property with flexibility. The composite also showed good properties as photothermal sensor

Neste trabalho, foi realizado o crescimento de nanotubos de carbono pela técnica de deposição química a vapor (CVD) térmica catalítica, utilizando-se filmes finos de níquel como material catalisador, gás metano (CH4) como fonte de hidrocarboneto e nitrogênio (N2) como gás de arraste. Amostras processadas sobre filmes de Ni de 15 nm de espessura, depositados sobre substrato de óxido de silício (SiO2), com temperatura de processo de 900 ºC e tempo de 15 minutos promoveram uma maior densidade de síntese de nanotubos de carbono, utilizando-se um fluxo na proporção de 2 partes de N2 para 1 parte de CH4. Comprovou-se sua síntese através da visualização de sua morfologia por microscopia eletrônica de varredura (SEM) e microscopia eletrônica de transmissão (TEM), além da extração de seu espectro característico por espectroscopia Raman e espectroscopia de dispersão de raio-X (EDS). Em um segundo estudo, depositaram-se sobre substratos de vidro filmes transparentes e condutores (TCF) à base de nanotubos de carbono de paredes múltiplas (MWCNT) comerciais, pela técnica de dip coating. Para isso, realizou-se a dispersão dos nanotubos sob diversas concentrações em água deionizada (DI) com o auxílio do surfactante dodecil sulfato de sódio (SDS), com posterior funcionalização através do ataque químico por ácido nítrico (HNO3), visando sua aplicação na fabricação de células solares. Foram utilizados os equipamento de quatro pontas e curva corrente x tensão (IV) para caracterização elétrica, transmitância por espectrofotometria para caracterização óptica, SEM para a visualização de sua morfologia e espectroscopia Raman para a análise química de suas estruturas. Valores de resistência de folha de 2x105 W/ e transmitância de 65% foram obtidos nas amostras mais concentradas, com 0,2 mg de nanotubos por ml de água DI. Uma etapa de limpeza em água DI pós deposição foi feita para remoção do excesso de surfactante presente no filme, o que prejudica tanto as características elétricas e ópticas, por ser um dielétrico e não ser transparente. Essa limpeza melhorou o valor de transmitância, porém aumentou a resistência de folha, devido à remoção parcial dos nanotubos presentes no filme, interrompendo em certos pontos a malha que promovia a passagem de corrente elétrica. O ataque químico por HNO3 promoveu a criação de algumas quebras na estrutura do carbono, o que é verificado pelo aumento da banda D, característico da presença de defeitos. / In this work, the growth of CNTs was investigated, using chemical vapor deposition (CVD) thermal catalytic technique, carried out by utilizing thin films of nickel as catalyst material, methane (CH4) as hydrocarbon source and nitrogen (N2) as carrier gas. Samples processed onto 15 nm thick Ni films, deposited on silicon oxide (SiO2) substrates, at a temperature of 900 °C for 15 minutes, promoted a higher density of carbon nanotubes, using a gas mixture at the ratio of 2 parts of N2 and 1 part of CH4. This was verified by analysing the nanotubes morphology by scanning electron microscopy (SEM) and transmission electronic microscopy (TEM) and by the extraction of its characteristic spectrum by Raman spectroscopy and energy dispersive spectroscopy (EDS). In a second study, transparent conductive films (TCF) based on commercial multi-walled carbon nanotubes (MWCNT) were deposited on glass substrates by the dip coating technique. To do so, carbon nanotubes (CNTs) with different concentrations were dispersed in deionized water (DI) with the addition of the surfactant sodium dodecyl sulfate (SDS), and subsequent functionalization through chemical attack by nitric acid (HNO3), aiming their application in solar cell fabrication. The four point probe equipment and current x voltage curve (IV) was used for electrical characterization, transmittance for optical characterization, SEM to visualize their morphology and Raman spectroscopy for chemical analysis of their structures. Sheet resistance values of 2x105 W/ and transmittance of 65% were obtained in the most concentrated samples, with 0.2 mg per ml of nanotubes in deionized water (DI). A cleaning stage in DI water after deposition was taken for removal of surfactant excess in the film, which harms both the electrical and optical characteristics, as it is a dielectric and not transparent. This cleaning improved the transmittance value, but increased the sheet resistance due to partial removal of the nanotubes in the film, interrupting at certain points the mesh of CNTs that promoted the passage of electric current. The chemical attack by HNO3 promoted the functionalization by creating some breaks in the carbon structure, which is checked by the observation of the increasing in D band, which is characteristic of defects.

No description available.

abstract: Reactive inkjet printing (RIJP) is a direct-write deposition technique that synthesizes and patterns functional materials simultaneously. It is a route to cheap fabrication of highly conductive features on a versatile range of substrates. Silver reactive inks have become a staple of conductive inkjet printing for application in printed and flexible electronics, photovoltaic metallization, and more. However, the high cost of silver makes these less effective for disposable and low-cost applications. This work aimed to develop a particle-free formulation for a nickel reactive ink capable of metallizing highly pure nickel at temperatures under 100 °C to facilitate printing on substrates like paper or plastic. Nickel offers a significantly cheaper alternative to silver at slightly reduced bulk conductivity. To meet these aims, three archetypes of inks were formulated. First were a set of glycerol-based inks temperature ink containing nickel acetate, hydrazine, and ammonia in a mixture of water and glycerol. This ink reduced between 115 – 200 °C to produce slightly oxidized deposits of nickel with carbon content around 10 wt %. The high temperature was addressed in a second series, which replaced glycerol with lower boiling glycols and added sodium hydroxide as a strong base to enhance thermodynamics and kinetics of reduction. These inks reduced between 60 and 100 °C but sodium salts contaminated the final deposits. In a third set of inks, sodium hydroxide was replaced with tetramethylammonium hydroxide (TMAH), a strong organic base, to address contamination. These inks also reduced between 60 and 100 °C. Pipetting or printing onto gold coated substrates produce metallic flakes coated in a clear, thick residue. EDS measured carbon and oxygen content up to 70 wt % of deposits. The residue was hypothesized to be a non-volatile byproduct of TMAH and acetate. Recommendations are provided to address the residue. Ultimately the formulated reactive inks did not meet design targets. However, this thesis sets the framework to design an optimal nickel reactive ink in future work. / Dissertation/Thesis / Masters Thesis Chemical Engineering 2019

A substantial body of scientific and medical research has examined the relationship between conductive energy devices and their physical risk to humans. This phenomenological study focused on the psychological impact of Taser utilization in police officers. This research explored how the experience of using a Taser in the line of duty affected officers from the conceptual framework of stress inoculation training and its applicability to Taser certification; the typical mental processes associated with using less-lethal weapons, perceptions of Taser training; and, the preparation provided in training for citizen injuries and deaths. Fifteen officers who had deployed a Taser were included as participants. The sample consisted of 2 randomized groups of 5, and 1 convenience group of 5 officers involved in Taser-related deaths. Data were collected through digitally recorded interviews of the officers' lived experiences. Data were analyzed using a 5-step method of constant comparison to develop and code themed clusters using the officers' own words. Findings showed officers believed the Taser was the best non-lethal device available but they preferred not using a Taser on citizens. In addition, Taser training may not be legally sufficient as defined in relevant court cases. A recommendation is that stress inoculation segments should be included in Taser training courses. Findings indicate Taser-related deaths have the potential to cause extreme stress and trauma in the officers, changing their lives and that of their families forever.

Recent advances in manufacturing of multifunctional materials have provided opportunities to develop structures that possess superior mechanical properties with other concurrent capabilities such as sensing, self-healing, electromagnetic and heat functionality. The idea is to fabricate components that can integrate multiple capabilities in order to develop lighter and more efficient structures. In this regard, due to their combined structural and electrical functionalities, electrically conductive carbon fiber reinforced polymer (CFRP) matrix composites have been used in a wide variety of applications in most of which they are exposed to unwanted impact-like mechanical loads. Experimental data have suggested that the application of an electromagnetic field at the moment of the impact can significantly reduce the damage in CFRP composites. However, the observations still need to be investigated carefully for practical applications. Furthermore, as the nature of the interactions between the electro-magneto-thermo-mechanical fields is very complicated, no analytical solutions can be found in the literature for the problem. In the present thesis, the effects of coupling between the electromagnetic and mechanical fields in electrically conductive anisotropic composite plates are studied. In particular, carbon fiber polymer matrix (CFRP) composites subjected to an impact-like mechanical load, pulsed electric current, and immersed in the magnetic field of constant magnitude are considered. The analysis is based on simultaneous solving of the system of nonlinear partial differential equations, including equations of motion and Maxwell's equations. Physics-based hypotheses for electro-magneto-mechanical coupling in transversely isotropic composite plates and dimension reduction solution procedures for the nonlinear system of the governing equations have been used to reduce the three-dimensional system to a two-dimensional (2D) form. A numerical solution procedure for the resulting 2D nonlinear mixed system of hyperbolic and parabolic partial differential equations has been developed, which consists of a sequential application of time and spatial integrations and quasilinearization. Extensive computational analysis of the response of the CFRP composite plates subjected to concurrent applications of different electromagnetic and mechanical loads has been conducted. The results of this work verify the results of the previous experimental studies on the subject and yield some suggestions for the characteristics of the electromagnetic load to create an optimum impact response of the composite.

Today’s state of the art additive manufacturing (AM) systems have the ability to fabricate multi-material devices with novel capabilities that were previously constrained by traditional manufacturing. AM machines fuse or deposit material in an additive fashion only where necessary, thus unlocking advantages of mass customization, no part-specific tooling, near arbitrary geometric complexity, and reduced lead times and cost. The combination of conductive ink micro-dispensing AM process with hybrid manufacturing processes including: laser machining, CNC machining, and pick & place enables the fabrication of printed electronics. Printed electronics exploit the integration of AM with hybrid processes and allow embedded and/or conformal electronics systems to be fabricated, which overcomes previously limited multi-functionality, decreases the form factor, and enhances performance. However, AM processes are still emerging technologies and lack qualification and standardization, which limits widespread application, especially in harsh environments (i.e. defense and industrial sectors). This dissertation explores three topics of electronics integration into AM that address the path toward qualification and standardization to evaluate the performance and repeatable fabrication of printed electronics for resilience when subjected to harsh environments. These topics include: (1) the effect of smoothing processes to improve the as-printed surface finish of AM components with mechanical and electrical characterization—which highlights the lack of qualification and standardization within AM printed electronics and paves the way for the remaining topics of the dissertation, (2) harsh environmental testing (i.e. mechanical shock, thermal cycling, die shear strength) and initiation of a foundation for qualification of printed electronic components to demonstrate survivability in harsh environments, and (3) the development of standardized methods to evaluate the adhesion of conductive inks while also analyzing the effect of surface treatments on the adhesive failure mode of conductive inks. The first topic of this dissertation addresses the as-printed surface roughness from individually fusing lines in AM extrusion processes that create semi-continuous components. In this work, the impact of surface smoothing on mechanical properties and electrical performance was measured. For the mechanical study, surface roughness was decreased with vapor smoothing by 70% while maintaining dimensional accuracy and increasing the hermetic seal to overcome the inherent porosity. However, there was little impact on the mechanical properties. For the electrical study, a vapor smoothing and a thermal smoothing process reduced the surface roughness of the surfaces of extruded substrates by 90% and 80% while also reducing measured dissipative losses up to 24% and 40% at 7 GHz, respectively. The second topic of this dissertation addresses the survivability of printed electronic components under harsh environmental conditions by adapting test methods and conducting preliminary evaluation of multi-material AM components for initializing qualification procedures. A few of the material sets show resilience to high G impacts up to 20,000 G’s and thermal cycling in extreme temperatures (-55 to 125ºC). It was also found that coefficient of thermal expansion matching is an important consideration for multi-material printed electronics and adhesion of the conductive ink is a prerequisite for antenna survivability in harsh environments. The final topic of this dissertation addresses the development of semi-quantitative and quantitative measurements for standardizing adhesion testing of conductive inks while also evaluating the effect of surface treatments. Without standard adhesion measurements of conductive inks, comparisons between materials or references to application requirements cannot be determined and limit the adoption of printed electronics. The semi-quantitative method evolved from manual cross-hatch scratch testing by designing, printing, and testing a semi-automated tool, which was coined scratch adhesion tester (SAT). By cross-hatch scratch testing with a semi-automated device, the SAT bypasses the operator-to-operator variance and allows more repeatable and finer analysis/comparison across labs. Alternatively, single lap shear testing permits quantitative adhesion measurements by providing a numerical value of the nominal interfacial shear strength of a coating upon testing while also showing surface treatments can improve adhesion and alter the adhesive (i.e. the delamination) failure mode of conductive inks.

An experimental investigation of the high pressure synthesis of water soluble, self doping conducting polymers is presented. 2- And 3-aminobenzenesulfonic acid and the respective sodium sulfonates have been polymerised. Optimal polymerisation conditions have been determined with respect to yield, conductivity and molecular weight. Reaction parameters such as oxidant, pressure, catalysts, reaction time and temperature and the use of additives were investigated. The minimum pressure required for polymerisation was 7 kbar. An increase in pressure had a negligible effect on polymer characteristics. The polymers were generated in aqueous, non-acidic media, to ensure they were selfdoping when characterised. Conductivities of between 10-6 Scm-1 and 10-3 Scm-1 were measured. The sulfonate salts reacted faster than the sulfonic acids and for both a longer reaction time resulted in higher yields and conductivities. These polymers were completely water soluble, of high molecular weight and able to be cast as thin films. The arylamines 5- and 8-aminonaphthalene-2-sulfonic acid and their respective sodium sulfonates were polymerised at elevated pressure. The naphthalene sulfonate salts polymerised at atmospheric pressure, but displayed a higher molecular weight when reacted under pressure. Generally the naphthalene monomers reacted similarly to the benzene monomers, although there were some differences. Conductivity and yield decreased with increased reaction times and the use of 0.1M equivalents of ferrous sulfate had an negligible effect on the polymers. The polynaphthalenes were highly water soluble, self doping and had conductivities in the order 10-5 to 10-3 Scm-1. A measurement of the activation volume for the polymerisation of 2-methoxyaniline and sodium 8-aminonaphthalene-2-sulfonate was performed. These were determined to be -44 ± 3 cm3mol-1 and -62 ± 10 cm3mol-1 respectively. These large negative values are consistent with rate limiting monomer oxidation.

Ce travail est consacré à l'étude du dopage de la polyaniline et de ses dérivés substitutés (polyanisidine, poly(2-ethylaniline)) avec d'une part le chlorure d'aluminium AlCl3 ou le chlorure ferrique FeCl3, d'autre part avec leurs dérivés contenant les ligands mixtes chlorure-acétylacétonate (AlCl2(acac) ou (FeCl(acac)2). Les polymères dopés avec AlCl3 ou FeCl3 sont conducteurs, et leur conductivité électronique est de l'ordre de 10-3 S/cm. Des études spectroscopiques complémentaires (UV-VIS-Proche IR, IRTF, RPE, RMN du noyau 27Al (dans le cas du dopage avec AlCl3) et spectroscopie Mössbauer sur le noyau 57Fe (dans le cas du dopage avec FeCl3)), combinées avec l'analyse élémentaire, permettent de comprendre et d'identifier un même mécanisme de dopage. Celui-ci correspond en un premier temps à une dissociation de la molécule du dopant. La partie cationique résultant de cette dissociation est complexée sur les sites azote de type imine de la chaîne du polymère, tandis que la partie anionique s'incorpore à la matrice polymère afin de neutraliser la charge positive imposée à la chaîne du polymère. La sphère de coordination du complexe cationique est complétée par solvatation avec une molécule de nitrométhane. Le réarrangement des charges accompagnant le processus de dopage entraîne la création de radicaux cationiques mobiles sur la chaîne du polymère, donnant ainsi au polymère dopé des propriétés de conduction électronique. Ce mécanisme rend parfaitement compte de la présence de porteurs de charge et de la structure cationique des radicaux de la chaîne polymérique dopée mises en évidence par les expériences de spectroscopie RPE et d'absorption UV-VIS-Proche IR. La polyaniline dopée avec FeCl3 présente de faibles propriétés mécaniques, qui peuvent cependant être améliorées par un traitement ultérieur avec l'hexafluoroacetylacetone (HFAA). Ce traitement conduit à la transformation de la polyaniline dopée avec FeCl3 (acide de Lewis) en un polymère dopé avec HFeCl4 (acide de Brönsted), simultanément plastifié par HFAA. Le dopage avec les ligands mixtes (AlCl2(acac) ou (FeCl(acac)2), bien qu'inopérant en ce qui concerne la polyaniline, conduit clairement au dopage de la polyanisidine et de la poly(2-éthylaniline). Les chaînes de ces polymères dopés présentent une structure radicalaire cationique mise en évidence par les expériences d'absorption UV-VIS-Proche IR ; mais le mécanisme de dopage reste plus complexe à définir que dans le cas du dopage avec AlCl3 ou FeCl3. Le dopage avec AlCl2(acac) conduit à un polymère dopé avec AlCl3 avec Al(acac)3 incorporé à la matrice du polymère comme sous-produit. Le dopage avec FeCl(acac)2 donne un composé présentant davantage de sites de fer non équivalents qu'il en est attendu ; leur nature reste difficile à identifier par spectrométrie Mössbauer.