Dissertation/Thèse

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2022
Thèses
1
  • GUILHERME MAGALHÃES PETINARDI
  • Characterization of CaCu3Ti4O12-based ceramics produced in different atmospheres

  • Leader : MARIA VIRGINIA GELFUSO
  • MEMBRES DE LA BANQUE :
  • DANIEL THOMAZINI
  • MANUEL HENRIQUE LENTE
  • MARIA VIRGINIA GELFUSO
  • ROSSANO GIMENES
  • Data: 4 févr. 2022


  • Afficher le Résumé
  • CaCu3Ti4O12 (CCTO)-based ceramics present dielectric constant values much higher than those observed for conventional materials (κ > 104), which are result of the microstructure formed by semiconductor grains and insulating grain boundaries, which are based on phase rich in CuO. The model known as Internal Barrier Layer Capacitor (IBLC) is currently a well-established proposal to explain the extraordinary values of the dielectric constant of this material, but it is insufficient to fully explain its behavior. For this reason, many studies are carried out on the effect of various structural and processing parameters, such as synthesis technique, sample thickness, sintering temperature, etc. on the microstructure and dielectric properties of CCTO. In this context, in this work, the characterization of ceramics based on CaCu3Ti4O12 produced in different atmospheres was proposed. For this purpose, ceramic powders with stoichiometric variations CazCuxTiyO12 (1,00 ≤ z ≤ 1,10; 2,90 ≤ x ≤ 3,00; 3,75 ≤ y ≤ 4,00) were produced by the chemical method of coprecipitation starting from of the precursors Ti(OC4H9)4, CaCO3 and Cu(NO3)2.3H2O and with subsequent calcination at 850 °C for 5 h, in atmospheres of air, He or H2. From the calcined powders, samples in the form of pellets were pressed uniaxially, under a pressure of 180 MPa, and then sintered at two different temperatures, 1050 and 1150 °C, both for 2 h, in the different atmospheres, air, He or H2, aiming to evaluate the influence of these atmospheres on the formation of secondary phases, on the structural, microstructural and dielectric properties of ceramics. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) allowed to identify the thermal processes of decomposition and formation of the CCTO crystalline phase. Structural analyzes were performed by X-ray diffractometry on the calcined powders and sintered ceramics, allowing to evaluate the evolution of the CCTO, CuO, TiO2 and CaTiO3 phases. Micrographs of powders and ceramic surfaces were obtained by scanning electron microscopy, allowing to determine the particle size distribution of powders and grains for the samples. Densities and dielectric properties were characterized for the sintered ceramics. The highest densification values, 97 %, was found to CCTO 3,00 H2 sample, while CCTO 2,90 air sample showed a lower densification, only 75 %, both sintered at 1050 °C. The dielectric constant (κ) and loss factor (tanδ) values were determined using the impedance spectroscopy technique, through measurements performed in a frequency range that varied between 20,0 Hz and 5,0 MHz, and κ values of 183×10³ and 171×10³ were obtained for the samples CCTO 2,90 He and CCTO 1,10 ar, sintered at 1150 °C, respectively, and these were also the samples that presented the highest tanδ values, that is, 0,559 and 0,598, respectively.

2
  • ERIC LUIZ PEREIRA
  • Graphene oxide and polyaniline composites obtained “in situ” by electrochemical method

  • Leader : MARIA ELENA LEYVA GONZALEZ
  • MEMBRES DE LA BANQUE :
  • ADHIMAR FLAVIO OLIVEIRA
  • ALVARO ANTONIO ALENCAR QUEIROZ
  • EDSON GIULIANI RAMOS FERNANDES
  • MARIA ELENA LEYVA GONZALEZ
  • MARIA FERNANDA XAVIER PINTO MEDEIROS
  • Data: 14 févr. 2022


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  • Due to the increased use of electric vehicles and the explosive growth of portable electronic devices, there has been an increase in the development of high-performance supercapacitors. In this context, the present research produced graphene oxide with PANI by the graphite exfoliation technique in an electrochemical cell. In this technique, graphite was used as an anode, H2SO4 1 M was used as an electrolyte, and the potential varied from 5 V to 13 V. The obtained material was characterized by Infrared Absorption Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), UV-vis Spectroscopy, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Cyclic Voltammetry (VC). The X-ray diffraction patterns indicate that the graphene oxide (GO) multilayers were exfoliated and adhered to the PANI chain. The presence and incorporation of PANI were confirmed from the SEM images, which show the OG well distributed in PANI with a nanowire format. The electrochemical performance of OG/PANI films and OG were investigated by cyclic voltammetry in 1 MH2SO4, presenting specific capacitance of 117.440 𝐹 𝑔−1 and 1.243 𝐹 𝑔−1 , respectively, at the rate of 1 𝑚𝑉 𝑠−1 scan. This increase can be attributed to the good distribution of electrical conductivity of PANI and graphene oxide. Thus, the results demonstrate the potential of the composite OG/PANI for application in high performance supercapacitors or other energy source system.

3
  • Tamara Aparecida Carvalho Ribeiro
  • Comparative Analysis of Mechanical Strength between Structural Elements Consisting of Concrete/Steel and Concrete/PRFC

  • Leader : ANTONIO CARLOS ANCELOTTI JUNIOR
  • MEMBRES DE LA BANQUE :
  • ANTONIO CARLOS ANCELOTTI JUNIOR
  • DANIELE ORNAGHI SANT'ANNA
  • FRANCISCO MOURA FILHO
  • GUILHERME FERREIRA GOMES
  • MIRIAN DE LOURDES NORONHA MOTTA MELO
  • PAULO SHIGUEME IDE
  • Data: 3 mars 2022


  • Afficher le Résumé
  • Seeking improvements in several areas, society advances in search of technological innovations in the discovery of new materials, and composite materials are products of this technological advance, characterized by presenting better performances in their applicability due to the combination of polymer, metal and ceramic materials in a single material. The present study aimed to analyze the mechanical strength demonstrated by composite materials made of reinforced concrete with CFRP and compare its results with the steel reinforced concrete, traditionally used in constructions. Therefore, different geometries of CDPs were made, both conventional and self-compacting concrete were used and the reinforcements were manufactured in bars and also in meshes. Additionally, it was studied which type of stirrup best adapts to CFRP bars and which characteristics of the concrete/CFRP interface provide the best adhesion resistance. The analyzes of this study were carried out due to the manufacture of CDPs in 4 distinct groups. The results showed that despite the use of different materials to manufacture the stirrup and the changes made in the connection interface of the CFRP bars and the concrete, such as the alternation of surface coatings used in the CFRP bars and the variation of concrete with different strengths, it was observed a parity in the values of mechanical resistance of the materials reinforced concrete with CFRP bars and concrete reinforced with steel. However, the use of CFRP in meshes molded externally to the concrete presented values of mechanical strength with an order of magnitude significantly higher when compared to the use of steel in meshes molded externally to the concrete, making this reinforcement configuration the most suitable for increasing mechanical strength. from the composite material reinforced concrete with steel to the composite material reinforced concrete with CFRP.

4
  • RAPHAEL ULISSES COSTA DE RESENDE
  • OBTAINING COATS WITH HIGH RESISTANCE TO OXIDATION IN THE MAR-M246 NICKEL SUPERALLOY FROM ALUMINUM AND SILICON CO-DEPOSITION USING THE “HALIDE ACTIVATED PACK CEMENTATION” PROCESS

  • Leader : GEOVANI RODRIGUES
  • MEMBRES DE LA BANQUE :
  • GEOVANI RODRIGUES
  • ANTONIO AUGUSTO ARAUJO PINTO DA SILVA
  • NABIL CHAIA
  • Data: 23 mars 2022


  • Afficher le Résumé
  • Nickel-based superalloys are the ones that stand out the most in applications involving high temperatures. They contain a combination of desired properties for such applications: high mechanical strength, high creep resistance, high fatigue resistance, high thermal conductivity, low anisotropy of thermal expansion and high resistance to oxidation. Among them there is the MAR-M246 alloy that has Al and Cr in its composition, elements responsible for the formation of layers of Al2O3 and Cr2O3, oxides that are capable of increasing the resistance to oxidation and corrosion at high temperatures. However, if the material were used for a long period of time, these layers may defragment (or in the case of chromium oxide, evaporate) which would interfere with the material's properties. One of the ways to prevent this degradation is to coat these alloys with oxidation-resistant layers and, among the coating methods, the process known as Halide Activated Pack Cementation (HAPC) is a very versatile method, low cost, used to cover different materials regardless of their geometry. Thus, this work proposed to coat the MAR-M246 alloy by co-deposition of Aluminum and Silicon using HAPC. For this purpose, three different powder coating mixtures (MPR) were created, with 75% Al2O3 powder, 25% of a mixture of Si and Al powders, in the ratios 90:10 (MPR I), 50:50 (MPR II) and 27.5:72.5 (MPR III) and 0.015mg NH4Cl. The coating process on the 3 samples was carried out at 1000°C for 9 hours in a vacuum sealed quartz reactor. The coated samples were characterized by Scanning Electron Microscopy (SEM), energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD) before and after oxidation tests. The results showed that there was a layer creation in the 3 MPR's, with thickness varying from 130 to 180 μm. Then, the coated substrates were placed in an oxidation test at 1000°C for 240 hours, revealing an optimization in the oxidation resistance by the formation of the Al2O3 oxide layer with a mass gain reduction of up to 2x for the layer formed by MPR III.

5
  • MARCOS CIRILO DOS SANTOS
  • MECHANICAL PROPERTIES OF MICROWAVE SINTERIZED ALUMINUM WITH REINFORCEMENT OF CARBON SPHERES OR GLASS PARTICLES

  • Leader : MARIA VIRGINIA GELFUSO
  • MEMBRES DE LA BANQUE :
  • ANDRÉ SILVA CHAVES
  • DANIEL THOMAZINI
  • EDMILSON OTONI CORREA
  • MARIA VIRGINIA GELFUSO
  • Data: 27 mai 2022


  • Afficher le Résumé
  • Aluminum is a material widely studied and used in the most varied projects and sectors of the economy due to a set of interesting properties that attribute to this material, ease in machinability, casting and even recycling processes. Powder metallurgy is a very efficient methodology used both in the production of aluminum composites, aiming to obtain significant mechanical properties that can meet the various applications required by the industry, such as high values of hardness, modulus of elasticity and resistance limit. Researchers have been studying both the insertion of reinforcement materials and alternative methodologies for the sintering of aluminum powder-based products, in order to control their mechanical properties. The great challenge is to achieve this objective using methodologies that are sustainable and friendly to the environment. In this context, focusing on the reuse of tailings and residues from discarded materials, reinforcement materials obtained from glass particles, produced by grinding discarded glassware in laboratories and/or carbon microspheres, produced from coconut fiber waste. The use of these reinforcements in the production of aluminum-based composites, using powder metallurgy and microwave sintering, becomes a highly promising alternative. Thus, in this work, the microwave sintering method was used to produce aluminum matrix-based composites containing borosilicate glass particle reinforcements and carbon microspheres, produced from coconut fiber by the microwave-assisted hydrothermal method. . The reinforcement materials, in proportions that varied between 0.1 and 10.0% by mass, were mixed with pure commercial aluminum powder, using a conventional pitcher mill. The carbon spheres used had an average diameter of 4.0 µm and the average diameter of the glass powder particles was 8.9 µm. The study on the optimization of the time used for the mixtures of aluminum powders to carbon sphere powders (AL-EC) and, aluminum powders to glass particle powders (AL-PV) were carried out, revealing that the mixture made in a horizontal ball mill, dry, for 9 hours leads to obtaining the most homogeneous mixtures. The powders obtained from the mixtures, AL-EC and AL-PV, were compacted, by uniaxial pressing, in the shape of discs using a metallic matrix. Subsequently, the discs were sintered at 600ºC for 60 minutes in a microwave oven. For comparative studies, samples of pure aluminum were sintered in microwave under the same conditions as the samples containing the reinforcements, and were sintered in a conventional oven. Densification measurements, as well as X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) analyzes were performed on the studied samples. The characterization of the mechanical properties was carried out by means of microhardness measurements and tests of flexural strength, or transverse rupture (TRS). The pure AL samples showed a microhardness of 65.50 HV and TRS of 103.4 Mpa. The AL-PV and AL-EC samples showed improvements in their mechanical properties compared to pure aluminum. The samples containing 1% of glass powder reinforcement had a microhardness of 99.29 HV and a flexural strength of 105.0 MPa, while the samples containing 1% of carbon spheres had a microhardness of 75.52 HV and flexural strength. of 82.3 MPa, obtaining important changes in the mechanical properties of the composites produced.

Thèses
1
  • MAYARA LIMA PERES DE OLIVEIRA
  • THERMOCHROMIC MICROSPHERES POTENTIALLY APPLICABLE TO PREDICTIVE MAINTENANCE OF POWER TRANSFORMERS

  • Leader : ALVARO ANTONIO ALENCAR QUEIROZ
  • MEMBRES DE LA BANQUE :
  • RUBENS GEDRAITE
  • ADHIMAR FLAVIO OLIVEIRA
  • ALVARO ANTONIO ALENCAR QUEIROZ
  • EDSON GIULIANI RAMOS FERNANDES
  • FABIO DA SILVA LISBOA
  • Data: 21 févr. 2022


  • Afficher le Résumé
  • Power transformers (TP) connect the entire electrical energy network, which goes from the generation and production of energy to the final consumer. Therefore, it is necessary to monitor their operating conditions. The operating condition of the TP is related to its insulation system, which includes the refrigerant oil and insulating paper, which must not operate at temperatures above technical specifications, as these conditions cause failures in the TP that can lead to interruption of the power supply. In this research, poly(glycerol dendrimer) microspheres encapsulating cobalt-doped hopeita (CoHoM) was synthesized for its potential use as optical thermometer with reversible thermochromic property coupled to a multilayer feed-forward artificial neural network as a proposal for temperature monitoring in power transformers. The purpose of this sensor is to show color change when the power transformer temperature reaches alert levels. The structures of the microspheres were studied using scanning electron microscopy (SEM), infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Through TGA it was possible to obtain information about the thermal tolerance of the material, which supports temperatures above 300°C. From the micrographs obtained from the powder material, it is possible to observe microspheres with smooth surfaces and with an average diameter of approximately 0.82μm. Through the analysis of X-ray diffractometry (XRD) it was observed the formation of crystalline phase in the planes (110) and (200) in the structure of Hopeite. After these analyzes an ink was produced as a thermochromic coating, which had its optical properties analyzed by UV-Vis techniques and automated color recognition in CIEL*a*b* space coordinates. Finally, it was shown that the CoHoM reversible thermochromic sensors allow detecting temperatures around 60°C, changing the color from dark blue to light pink. CoHoM sensors have potential for monitoring power transformers and show promise for use in real-time analysis.

2
  • DANIEL BRIGHENTI BORTOLUZZI
  • DEVELOPMENT OF TRIDIMENSIONAL CARBON FIBER/EPOXY COMPOSITES REINFORCED THROUGH THE THICKNESS AND THE MECHANICAL CHARACTERIZATION OF INTERLAMINAR FRACTURE TOUGHNESS AND VIBRATION PROPERTIES

  • Leader : ANTONIO CARLOS ANCELOTTI JUNIOR
  • MEMBRES DE LA BANQUE :
  • ANDREZA DE SOUSA ANDRADA
  • ANTONIO CARLOS ANCELOTTI JUNIOR
  • GUILHERME FERREIRA GOMES
  • LUIZ CLAUDIO PARDINI
  • RICARDO MELLO DI BENEDETTO
  • SEBASTIAO SIMOES DA CUNHA JUNIOR
  • Data: 24 févr. 2022


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  • This study is focused on the assessment of the interlaminar fracture toughness in mode II and vibration mechanical properties of composites reinforced through the thickness with rectangular z-pinned manufactured by VARTM (Vacuum-assisted resin transfer molding) process. The influence of z-pinning in the mechanical properties of laminated structures is carried out and for the specimens with different z-pins sizes and pin areal densities are manufactured after Design of Experiment (DOE) matrix determination. For the composites fabricated without a polymeric mold, vibration properties z-pins reinforced composites demonstrated that the size and density of insertion of z-pins has a direct influence on the natural frequency of vibration, on the damping, or loss, and the amplitude of vibration. With the optimization made by the method of response surface (MSR), in a mono-objective analysis, it was demonstrated that it is possible to obtaining reductions in the maximum amplitude of forced vibration of 115%, and in an analysis multi objective has been shown that with a given insertion density and size of z-pins 81% reductions in maximum forced vibration amplitude and increases of 25% and 11% can be achieved damping factor and natural frequency of vibration, respectively. For the composites manufactured with polymeric mold, the fracture toughness in mode II was investigated and the results showed that pinning in composites improved the fracture resistance for all pinning proposals built. For the NPC (Non-precracked) step, the highest (GIIc)value achieved was for a 0.50 mm with a 2% pin density insertion, being 106% higher than the unpinned specimen. For the PC (Precracked) step, the thicker pins 1.00 mm and 1.10 mm acted again as a positive influence to mitigate the delamination and achieved elevated values of (GIIc), 77.5% and 78.3% higher than the unpinned specimen, respectively. The statistical results pointed that for the NPC case, the increase in density of pins always generates an increase in the fracture toughness and the contribution of the pin size to increase the fracture toughness. From there, increasing the size of the pin has little influence in NPC. For PC case, was shown that the pin size increasing decreases the fracture resistance, except for low pin density. Furthermore, the Artificial Neural Networks (ANN) trained with part of these experimental data showed excellent predictive capacity of fracture toughness. The modal responses of the laminates fabricated with a polymeric mold the experimental results indicated that, in most cases, there was an increase in the natural frequency and highlights the reduction, from approx. 60% to 70%, in the amplitude of vibration for all specimens with z-pin reinforcement in comparison to the unpinned. Furthermore, the experimental data compared the statistical results pointed that z-pins had a positive influence increasing and decreasing natural frequency and forced vibration amplitude, respectively, of z-pinned composites compared to the non-reinforced and the trained ANN with the experimental data presented a very good agreement with experimental tests carried out in this investigation for predicting modal response.

3
  • JUAN OSWALDO MONTOYA URIBE
  • Dielectric properties of CaCu3Ti4O12 ceramics with CuO and TiO2 deficiency as a function of different synthesis and sintering routes

  • Leader : MARIA VIRGINIA GELFUSO
  • MEMBRES DE LA BANQUE :
  • ADHIMAR FLAVIO OLIVEIRA
  • ADILSON LUIZ CHINELATTO
  • DANIEL THOMAZINI
  • ELIRIA MARIA DE JESUS AGNOLON PALLONE
  • MARIA ELENA LEYVA GONZALEZ
  • MARIA VIRGINIA GELFUSO
  • Data: 9 mars 2022


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  • CaCu3Ti4O12 (CCTO) ceramics have attracted increasing interest because of their extraordinary dielectric constant values (κ > 104 at 1 kHz). The structural, microstructural and dielectric characteristics of the CCTO are dependent on the synthesis and processing methods, being the subject of constant investigation. In this work the influence of some synthesis and sintering parameters on the dielectric properties of these CCTO ceramics was investigated. According to the coprecipitated synthesis method, ceramic powders of CaCuXTiYO12 (CCXTYO) were produced with stoichiometric variations associated with low CuO and TiO2 contents, where X|Y = 2.70|3.25; 2.80|3.50; 2.90|3.75; 2.95|3.87 e 3.0|4.0. The samples were exposed to different processing variables, being investigated the influence of these on the physical-chemical characteristics of CCXTYO ceramics. A two-stage calcination route was carried out at 350 °C and 850 °C, at different heating rates, and with grinding inclusion in each. The sintering process included a first firing step, performed at 1100 °C, at a rate of 10 °C/min and in air; different landing times were included. A second, and subsequent step, was carried out at 1150 °C for 5 h. The variables and parameters of sintering and processing allowed to consolidate the maximization of the amount of CCTO phase in the microstructure and to promote grain growth to obtain CCXTYO ceramics with excellent dielectric properties. XRD patterns confirmed the majority presence of the CCTO phase in each compound, as well as discrete traces of secondary phases such as CuO, TiO2 and CaTiO3. Scanning Electron Microscopy (SEM) allowed evaluating the presence of the CuO and TiO2 crystalline phase in the grain boundaries, as well as the morphology, growth and evolution of the CCTO grains. In the frequency range 20 Hz to 5 MHz, at room temperature, measurements of impedance spectroscopy (IS) showed that the highest average grain size and composition (X|Y[2.95|3.87]PS1/PS2) exhibited the highest values of κ (3.5x104, at 1 kHz). The ceramics with the narrower grain size distributions showed the lowest tanδ values (0.030, at 1 kHz). The dielectric measurements showed the existence of relaxation mechanisms, which were fitted by the Nyquist diagram, and modeled by equivalent circuits in parallel, in order to know the contributions of grain, grain boundary and electrode-sample interface. Different polarization mechanisms, especially Maxwell-Wagner, justify the dielectric behavior of this material, one of them originating in domain boundaries or any other type of internal barrier in semiconductor grains, and another generated in grain boundaries (explained by the IBLC model).

4
  • JOÃO IDER SILVA JÚNIOR
  • Preparation and characterization of thermoelectric materials

  • Leader : RERO MARQUES RUBINGER
  • MEMBRES DE LA BANQUE :
  • ADHIMAR FLAVIO OLIVEIRA
  • ALAN BENDASOLI PAVAN
  • ANTONIO CARLOS ANCELOTTI JUNIOR
  • RERO MARQUES RUBINGER
  • VANDER ALKMIN DOS SANTOS RIBEIRO
  • WAGNER SOUZA MACHADO
  • Data: 22 juil. 2022


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  • This work presents a complete study of thermoelectric materials. It starts with a study of a Solar Concentrator and the development of a Genetic Algorithm and Cross-Entropy for analyzing experimental data. Contains a study on thermoelectric devices, from a new experimental setup. It also counts on the development and manufacture of an entire equipment for measuring thermoelectric materials, both bulks and thin films. It ends with the preparation of a specific thermoelectric material, the MoS2, and the use of all the apparatus previously developed for its study.

5
  • JOSÉ NILSON DA CONCEIÇÃO
  • Study of the Effects of Solubilization and Aging Treatments in Mechanical Properties and Corrosion Resistance of Tubes Stainless Steel Superduplex UNS S39274

  • Leader : EDMILSON OTONI CORREA
  • MEMBRES DE LA BANQUE :
  • CARLOS ALBERTO CARVALHO CASTRO
  • EDMILSON OTONI CORREA
  • JEAN CARLO CESCON PEREIRA
  • MIRIAN DE LOURDES NORONHA MOTTA MELO
  • SERGIO SOUTO MAIOR TAVARES
  • WANDERLEY XAVIER PEREIRA
  • Data: 4 août 2022


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  • Superduplex stainless steels (SDSSs) are austenitic-ferritic corrosion resistant altos (CRA) with pitting equivalent number (PREN) higher than 40. This class of steel combines excellent mechanical properties and corrosion resistance, for this reason these alloys have found widespread use in aggressive and hostile environments such as in the chemical and petrochemical industry and especially in the oil and gas production and refining. These characteristics are mainly attributed to the presence of two phases: ferrite (α) and austenite (γ) distributed nearly in equal proportion. However, SDSS are subject to suffer deleterious precipitation of alpha prime (α') phase, more pronounced at 475ºC. This precipitation causes embrittlement of material, promoting an increase in hardness, in yield strength, in the ultimate tensile and decrease in total elongation. This work aimed to to study the effects of solubilization and aging treatments on the mechanical properties and corrosion resistance in the SDSS UNS S39274 under the conditions As-Received, As-Received solution-treated at 1150ºC for 40 minutes and aged at 400ºC for 8 and 12 hours and at 475ºC for 4, 8, 12 and 200 hours. The microstructure was observed by Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) showing two phases, ferrite (α) and austenite (γ). The effects of isothermal treatments on the mechanical properties of the material were studied using Vickers hardness and microhardness, uniaxial tensile and Charpy impact tests. The results show an increase in hardness, yield strength and ultimate tensile as a function of aging time of the samples at 400ºC and 475ºC. On the other hand, they point to a decrease in elongation and, above all, in Charpy impact energy. These changes in mechanical properties are more evident in SDSS UNS S39274 samples aged at 475ºC. Corrosion tests by Electrochemical Polarization Cyclic Reactivation (PERC or DL-EPR) indicate that there was not sensitization of the analyzed specimens. Which suggests that the material had high corrosion resistance.

6
  • SAMANTA DE OLIVEIRA ALVES TORRES
  • THERMOELECTRIC PROPERTIES OF DOPED CAMnO3-BASED CERAMICS PRODUCED BY CHEMICAL ROUTE

  • Leader : MARIA VIRGINIA GELFUSO
  • MEMBRES DE LA BANQUE :
  • VÂNIA CALDAS DE SOUSA
  • ADRIANA SCOTON ANTONIO CHINELATTO
  • MARCELO GONÇALVES VIVAS
  • MARIA VIRGINIA GELFUSO
  • TANIA REGINA GIRALDI
  • Data: 7 oct. 2022


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  • The thermoelectric materials have been very investigated due to its capacity to direct conversion of thermal energy into electrical energy, focusing on the search for materials that have high values of Figure of Merit (ZT), used in calculations of energy conversion efficiency. Among these oxides, the CaMnO3(CMO) is a strong candidate for thermoelectric applications because in addition to the mentioned stability, these ceramics can acquire conductive properties under suitable conditions of synthesis and processing, as well as by the addition of dopants, which consequently gives them superior thermoelectric properties. Thus, in this work, the influence of dopants and different sintering times on the thermoelectric properties was studied for the CMO ceramics obtained by a simplified chemical route, developed in this work. The powders of the pure (CMO) and doped compositions with 10mol% La3+ (CMO-La) and 4mol% V5+ were produced by modified Pechini method. The amounts of the adopted dopants were based on the literature for V5+ and on work developed in the master’s degree for doping with La3+. From these powders, the samples in the form of disks were uniaxially pressed, and after, the samples were sintered in air resistive electric furnace for the 1, 3, 6, 12 and 24 h. The sintering process were realized at 1270°C to CMO composition, at 1100°C for the CMO-La and 1400 °C to CMO-V, these temperatures being defined from the dilatometric analysis. The apparent densities, determined by Archimedes’ Principle reached values greater than 80% for the CMO, CMO-La and CMO-V compositions. The X-ray diffraction, scanning electron microscopy assisted by energy dispersive spectroscopy were conducted to realization of structural, microstructural, and semi-quantitative chemical analysis, respectively. From these characterizations, it was verified the formation of the CMO phase for all the sintered compositions and the presence of a small amount of the secondary phase (CaMn2O4) was found in the CMO and CMO-V composition. Results of Seebeck coefficient, 4-probe DC electrical conductivity and the thermal conductivity recorded for samples between 25ºC and 600ºC, were used in the calculation of Figure of Merit (ZT) and Power Factor, characterizing the thermoelectric properties of the samples. The CMO, sintered for 12h (CMO (12h)) presented the highest Seebeck coefficient, which is -350μV/K. The CMO-La sample (3h) presented the highest electrical conductivity, reaching values of 14000S/m, at 400°C, while the CMO-La (1,3 e 6h) registered the lowest thermal conductivity reaching a maximum value of 4.7 W/mK. The best values of thermoelectric properties were achieved for CMO-La (3h), presenting a result of a power factor of 4.1x10-4 W/mK² and CMO-V (1h) 3.25x10-4 W/mK²). From these results, the
    highlighted composition for thermoelectric application, CMO-La (3h) was subjected to sintering in oxidizing and reducing atmospheres. The sintered sample in a reducing atmosphere showed promising results, presenting the highest value of Figure of Merit. Thus, the CMO-La sample sintered for 3h in an H2 atmosphere at 600 °C reached ZT values of 0.12.

2021
Thèses
1
  • JAQUELINE DO CARMO LIMA CARVALHO
  • PRODUCTION OF MODIFIED CeO2 WITH COBALT OBTAINED BY MICROWAVE ASSISTED HYDROTHERMAL METHOD

  • Leader : FRANCISCO MOURA FILHO
  • MEMBRES DE LA BANQUE :
  • MIGUEL ADOLFO PONCE
  • FRANCISCO MOURA FILHO
  • MARCIO MARTINS LAGE JUNIOR
  • Data: 17 févr. 2021


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  • In the last few years, the study of ceramic materials has been evolving rapidly, especially those related to so-called functional ceramics. The diverse applications involving these materials, mainly as nanoparticles, make these materials interesting in electronic components, biomedical applications and gas sensors. In the specific case of sensors based on semiconductor ceramics, efforts have been aimed at increasing stability, sensitivity and selectivity, capable of detecting low concentrations of polluting gases, flammable harmful to health and safety and that can operate in conditions optimized, in addition to reducing energy costs and response and recovery times for systems based on transition metal oxides. In this perspective, Cerium Oxide (CeO2) has been widely researched for having unique properties, such as a strong capacity to absorb and release oxygen, easy oxidation and high ion mobility. Thus, cerium oxide nanoparticles doped with cobalt (CeO2: Co) in different concentrations (0, 4, 8 and 12 mol%) were synthesized by the microwave assisted hydrothermal method. The synthesized samples were characterized using different techniques to understand their structural and sensor properties. The X-ray diffraction patterns, the Raman spectra and the Fourier transform infrared spectroscopy confirm the formation of solid crystalline solutions with cubic structure of the fluorite type, belonging to the space group Fm-3m. The synthesis method employed was effective in the production of nanoparticles, with diameters less than 2.57 nm, as presented by the Rietveld refinement, and exhibiting high crystallinity. The optical properties were investigated using visible ultraviolet spectroscopy (UV-vis). The nature of the optical absorption band was observed in the nanoparticles of pure CeO2 and doped with cobalt with band gap energy decreasing as the concentration of the dopant increased. The chemical composition of the surface of the samples was analyzed using the X-ray photoelectron spectroscopy (XPS) technique while the microstructural properties were assessed by scanning electron microscopy (FEG-SEM). Measurements of electrical resistance of the samples were used to evaluate the sensing properties of the samples, such as sensitivity, response and recovery time when exposed to carbon monoxide (CO) gas. The electrical resistance measurements when the films were exposed to gas revealed that the synthesis method was efficient in obtaining samples that have a great potential to be applied as gas sensors.

2
  • FELIPE SILVA FARIA
  • INFLUENCE OF THE CONTENT AND GRANULOMETRY OF POLYURETHANE WASTE ON MORTAR PRODUCTION

  • Leader : MIRIAN DE LOURDES NORONHA MOTTA MELO
  • MEMBRES DE LA BANQUE :
  • MIRIAN DE LOURDES NORONHA MOTTA MELO
  • PAULO CESAR GONCALVES
  • VALQUIRIA CLARET DOS SANTOS
  • VANDER ALKMIN DOS SANTOS RIBEIRO
  • Data: 19 févr. 2021


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  • Developing at a fast pace, the world has suffered from accumulations of waste. These residues come from all areas, which means that measures have been obtained for years. Laws, standards, studies and research are connected to reduce the environmental impact. therefore, alternatives that can seek to solve not only problems in one area, but also other areas at the same time. Mortar and concrete use a lot of natural resources and generate a lot of waste as well. Another environmental problem is the waste from refrigerators that are increasing over the years. This work seeks to analyze the use of mortars with the use of refrigerator residues and their properties. A reference trace was made and the fine aggregate was subsequently replaced by polymer residues from the refrigerators, in the proportions of 2.5%, 5% and 10% and changing its granulometry in two groups. Tests were performed as: resistance to axial compression, water absorption, voids index, specific mass, dynamic elastic modulus. Through the literature it was already possible to expect a decrease in resistance, but with an incorporation of 2.5% results close to the reference trace were found. Even with a different result of 2.5%, the 5% strokes are also satisfactory complementary measures, since the main focus of the work is an alternative for the reuse of waste. It is concluded that it is possible to use 2.5% and 5% for use purposes.

3
  • JOSÉ HENRIQUE RODRIGUES DA ROCHA
  • Evaluation of organoclays and dispersants in the preparation of magnetorheological suspensions

  • Leader : ANTONIO JOSE FARIA BOMBARD
  • MEMBRES DE LA BANQUE :
  • ANTONIO CARLOS ANCELOTTI JUNIOR
  • ANTONIO JOSE FARIA BOMBARD
  • DANIELA SACHS
  • MARCOS AKIRA D AVILA
  • Data: 3 mai 2021


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  • Magnetorheological Fluids (FMR) are smart materials that, when subjected to the influence of a magnetic field, present a response in their rheological properties. This work presents the process of preparing and characterizing a MRF containing carbonyl iron particles dispersed in a matrix of polyalphaolefin (PAO) oil, and different types of organoclays (OC) as a suspension stabilization element. The selection of the thixotropic pre-gel was made in a group of 15 options prepared using different organoclays. It was observed that phyllosilicate OC resulted in a gel with a weak viscoelastic behavior (G '~ 100 to 300 Pa and G ”~ 30 to 50 Pa) in the linear viscoelastic region, while the smectite or bentonites formed consistent viscoelastic gels (G '~ 1 to 5 kPa and G ”~ 70 to 250 Pa). The formulation 6 (23.067 g of PAO, 1.234 g of clay, 0.436 g of polar activator) was selected, it showed yield stress τy = (42.3 ± 2.6) Pa, storage module G '= (2690 ± 201) Pa, cohesive energy density = 97.86 mJ / m³. Seven (A-G) stable and functional MRF were prepared using HS / PAO iron carbonyl particles. The result of the thixotropy tests demonstrated the values for A (147.6%), B (181.2%), C (118.3%), D (152.0%), E (145.8%), F (140.9%) and G (114.5%) regarding thixotropic recover. The formulations A, B and C, showed similar redispersibility results after 1 year of preparation, the normal strength measured was up to 0.6 N. However, the fluid C showed better MR effect = 2000x , G'off = 10000 Pa, and redispersibility after one year - FN = 0.39 N and W = 9.4 mJ. The test results performed allow to the conclusion the MR fluid manufactured with dispersant C showed a better compromise between the measured properties: G’off, τy, MR effect, and most importantly, the redispersibility after 1 year of preparation.

4
  • FILIPE BUENO VILELA
  • Development of a printed polymeric mesh with a coupled non-invasive electro-stimulation device for the treatment of bone fractures

  • Leader : DANIELA SACHS
  • MEMBRES DE LA BANQUE :
  • SAMIRA ESTEVES AFONSO CAMARGO
  • ANTONIO CARLOS ANCELOTTI JUNIOR
  • DANIELA SACHS
  • PATRÍCIA CAPELLATO
  • Data: 29 juil. 2021


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  • The occurrence of bone fractures has progressed globally proportionally to the increase in life expectancy of people. Advances in bone immobilization and regeneration techniques used in medical practice, however, progressed more slowly. The use of orthopedic plaster and fiberglass are still widely used materials, although they imply clinical complications. The additive manufacturing of 3D orthoses appears as a potential innovation, but it still has restrictions for its dissemination, mainly related to the difficulty of immobilization and modeling on the fracture. Furthermore, the use of electrostimulators to accelerate the osteogenic effect in the fracture region is an important practice to reduce treatment time. However, the majority of these devices has properties and dimensions that make it difficult to be used concomitantly with orthopedic immobilizers and for adherence within the daily life of patients. Thus, it was proposed in this work the development of an orthosis printed using thermoplastic biopolymers coupled with an electrostimulator of combined magnetic field (CMC). The objective was to create a system that has advantageous characteristics compared to those observed in technologies currently used for orthopedic immobilization and bone fracture regeneration. Thus, the printed orthosis was composed of two meshes, immobilization and fixation. The developed electrostimulator consisted of an electronic circuit and a mobile application. The project concept, including orthosis and electrical stimulator, were evaluated by health professionals specialized in orthopedics after the approval by the Research Ethics Committee. Based on the results presented, it can be concluded that the design of the printed orthosis (PLA/TPU) with the coupled CMC electrostimulator has advantageous characteristics compared to those observed in currently used immobilization and bone regeneration systems.

5
  • PEDRO HENRIQUE GONÇALVES
  • Study of the Reuse of Vanadis®8 Superclean Steel through the Powder Metallurgy Route using the High Energy Milling technique (Mechanical Milling).

  • Leader : GILBERT SILVA
  • MEMBRES DE LA BANQUE :
  • ANTONIO AUGUSTO ARAUJO PINTO DA SILVA
  • EDMILSON OTONI CORREA
  • GILBERT SILVA
  • KATIA REGINA CARDOSO
  • Data: 3 août 2021


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  • Uddeholm Vanadis®8 Superclean steel corresponds to the grade of cold work tool steels containing high contents of carbon, vanadium, chromium and molybdenum, high wear resistance, high mechanical strength and hardness, dimensional stability and good toughness, being used in various applications as in the manufacture of dies for mechanical forming, extruders, cutlery. They are supplied to demand in the form of ingots and billets which need to be machined to form the final product. The chips generated in the machining process are often remelted and/or maybe even discarded, which harms the environment, in addition to the loss of the material's added value. In order to reuse metallic waste, the Powder Metallurgy (PM) route has proven to be an efficient alternative for having high use of raw material, low energy consumption, production of parts / components with structural and mechanical homogeneity and good superficial finish. Thus, this work had as objective the production of metallic powders by the process of high energy ball milling (HEBM) from the reuse of Vanadis®8 steel chips with and without addition of carbides. As a comparative effect on the efficiency of the HEM, three series were determined: with addition of vanadium carbides (V8VC), a mixture of vanadium, chromium and molybdenum carbides - V8(VMoCr)C and without addition of carbides (V8SC). The morphology and granulometry analyzes of the powders at different milling times were performed by scanning electron microscopy and particle size analysis by laser diffraction. The structural and mechanical characterization of the sintered, quenched and tempered were performed by scanning electron microscopy, optical microscopy, X-ray diffraction, bulk density via Archimedes and by MO, Vickers microhardness and compression testing. The results reveal that all the usual conditions in the HEBM were efficient, with an emphasis on the V8(VMoCr)C series, with an average particle size of 11.48 µm. The sintering parameters improve, increasing the average density by 86.31% in relation to the CR material, with an emphasis on a V8SC series (87.46%), evidenced by the lower apparent porosity. The quenching and tempering heat treatments promoted an increase in the microhardness and compressive strength of the new materials developed, mainly after the tempering, where the microhardness was close to the CR material, also treated. Regarding the results of maximum compressive strength and modulus of elasticity, as three series presented approximately equal values, considering the standard deviation, with emphasis on the additions of V8VC, which presented high compressive strength of 1710.29 MPa, and for the samples V8(VMoCr )C wich presented an elastic modulus of 17945.28 MPa. The microstructural transformations for the materials developed in this work were similar to Vanadis®8 steel as received. Therefore, the PM process using the HEBM technique proves to be an efficient alternative route in the reuse of Vanadis®8 tool steel chips.



6
  • LUCAS VICTOR BENJAMIM VASCONCELOS FRÉ
  • TiO2 NANOTUBES LOADED WITH PYRAZOLE-TETRAZOLIC HYBRIDS: A POTENTIAL SYSTEM AGAINST BACTERIAL INFECTION

  • Leader : DANIELA SACHS
  • MEMBRES DE LA BANQUE :
  • GILBERT SILVA
  • PATRÍCIA CAPELLATO
  • SAMIRA ESTEVES AFONSO CAMARGO
  • Data: 7 déc. 2021


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  • The implant failures present rate of 10% worldwide, causing losses of 20 billion dollars per year. The impact of this reality is socioeconomic, as it also harms patients with physical pain, psychological trauma and restricted mobility. Studies of surface modifications in titanium implants have been investigated to reduce the incidence of bacteria on the surface of biomaterials. Surface treatments coated with TiO2 nanotubes associated with antimicrobial compounds are a possible solution to reduce the rate of failures caused by bacteria. The objective of this work is to associate TiO2 nanotubes to two novel hybrid pyrazol-tetrazol compounds, the compound 5-[1-(3-chlorophenyl)-3-methyl-1H-pyrazol-4-yl)]-1H-tetrazol (JVS02 ) and 5-[1-(3,4-dichlorophenyl)-3-methyl-1H-pyrazol-4-yl)]-1H-tetrazol (JVS05), to reduce bacteria on the surface of pure titanium biomaterials for implants. The material was evaluated by scanning electron microscope (SEM), X-ray diffraction (XRD) and contact angle. The compounds associated with TiO2 nanotubes were characterized by drug release test and the biofilm test with Staphylococcus aureus bacteria of the HU25 strain. The results showed that the anodization resulted in TiO2 nanotubes on the surface of the anodized material with diameters of 50 nm, present in the rutile phase and the material became hydrophilic with an average contact angle of 7.81°. The release test showed that compound JVS02 has an immediate release and compound JVS05 has a gradual release with clear delimitation between phases. The biofilm test showed that the JVS05 compound has greater action against the formation of biofilm on the material's surface. With the results presented, we can conclude that there was loading of both compounds studied in TiO2 nanotubes on titanium substrates and among these, the compound 5-[1-(3,4-dichlorophenyl)-3-methyl-1H-pyrazol-4 -il)]-1H-tetrazol has more adequate characteristics for a drug delivery system due to its release time and antimicrobial action.

7
  • RENATO SERGIO MELLO DA SILVA
  • Effect of Iron Content on the Microstructure and Mechanical Properties of Al-Si-Cu-Mg Alloys Varying the Cooling Rate

  • Leader : MIRIAN DE LOURDES NORONHA MOTTA MELO
  • MEMBRES DE LA BANQUE :
  • DANIELA SACHS
  • MIRIAN DE LOURDES NORONHA MOTTA MELO
  • NEIDE APARECIDA MARIANO
  • PAULO JUNHO DE OLIVEIRA
  • Data: 17 déc. 2021


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  • Aluminum is the metal of modern life. Heat-treatable aluminum alloys currently occupy a prominent place in the industrial sector and with even greater prospects for use in the future. The A356 alloy is extended to automotive, aerospace and other industrial areas due to its excellent properties, including high strength, low density and excellent castability. Aiming at production cost benefits, less energy consumption and elimination of environmental damage associated with the mining and refining sectors, the recycling of aluminum alloys has been widely explored. In recycled foundry alloys, iron is the main impurity found and, due to its low solubility in aluminum, its presence leads to the formation of second phases, such as β - Al5FeSi intermetallic compounds which are presented in the form of thin and long platelets (needles ) which have a fragile character, degrading the strength and ductility of the alloy, as they act as stress concentrators. The size of the β - Al5FeSi phase needles increases the higher the iron content in the alloy and the lower the cooling rate. Thus, optimal control of iron concentration in foundry alloys is essential. In order to evaluate the effect of iron content on the microstructure and mechanical properties of the A356 alloy, the alloy was cast, containing 1% and 3% iron in its composition and then heat treated. The microstructure after remelting and solidification presents intermetallic phases with acicular morphology of the AlSiMgFe and AlFeSi composition. On the other hand, the microstructure after heat treatment presents intermetallic phases in needle shapes with β -Al5FeSi composition. The additions of iron resulted in a decrease in the cooling rate. It was found that as the iron content increases, there is a reduction in the distribution of the volume fraction of precipitates and an increase in grain size. It is also verified that with different cooling rates, the volume fraction changes, concluding that the higher the cooling rate, the greater the volume fraction. After performing the microhardness test for post-remelting, it was possible to notice an increase in the values of alloys with iron contents. The microhardness values in relation to the cooling rates used in quenching were unexpected. The recycling simulation of this work and consequent iron contamination in the A356 alloy generated changes in the solidification sequence, enabling the appearance of primary phases formed of iron before the crystallization of aluminum grains.

Thèses
1
  • RAPHAEL FELCA GLORIA
  • STUDY OF COATING PROCESS OF THE SUPERALLOY Mar-M246 USING THE HALIDE ACTIVATED PACK CEMENTATION (HAPC) METHOD

  • Leader : GEOVANI RODRIGUES
  • MEMBRES DE LA BANQUE :
  • ANTONIO AUGUSTO ARAUJO PINTO DA SILVA
  • CARLOS ANGELO NUNES
  • GEOVANI RODRIGUES
  • GILBERTO CARVALHO COELHO
  • NABIL CHAIA
  • RENATA NEVES PENHA
  • Data: 25 févr. 2021


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  • The advancement of technology has been the main reason for the production of new structural materials combining excellent mechanical properties, low manufacturing cost and applications in diverse environments. Among the most advanced materials, nickel-based superalloys are the most prominent in applications involving high temperatures. For these applications, an appropriate balance of properties is required, such as high mechanical strength, high creep resistance, high fatigue resistance, high thermal conductivity, low thermal expansion anisotropy and high oxidation resistance. Among these alloys are Mar-M246 and Mar-M247, which have Al and Cr in their composition, responsible for the formation of Al2O3 and Cr2O3 oxide scale, useful of increasing resistance to oxidation and corrosion at high temperatures. However, the use of these superalloys for a long period of time can cause the fragmentation of these oxide scales or the evaporation of the Cr2O3, interfering with the integrality of the material. One way to increase the useful life of these alloys is to coating them with scales that are highly resistant to oxidation without interfering with the properties of the substrate. The Halide Activated Pack Cementation (HAPC) process is a very versatile, low-cost method used to coating many materials, regardless of their geometry. In view of this scenario, the objective of this work was to study the deposition of aluminum, one of the most used in the protection against oxidation and corrosion, for the formation of coatings by the HAPC process on the Mar-M246 nickel superalloy, which until now has not been reported in the open literature. The aluminization process was carried out at four different temperatures, using NH4Cl as an activator and a powders mixture containing pure Al and alumina. A thermodynamic study, with the aid of the HSC Chemistry 6.0 software, contributed to the choice of temperatures and activator, in addition to obtaining an aluminum deposition mechanism in the formation of the coating phase for the process at 1000°C. The results showed, for all temperatures, coating without cracks, pores or adhesion failures to the substrate and a layers with Ni2Al3 and/or NiAl3 in chemical composition. The growth of the coating was evaluated by the growth kinetics in processes from 1 to 16 h, obtaining the information of a parabolic growth and activation energy of 96.55 kJ.mol-1, for the process of aluminization via HAPC, where these coatings were characterized by scanning electron microscopy (SEM). All coatings formed in a period of 9 h, at all temperatures studied, were characterized by optical microscopy (MO), SEM, dispersive energy spectroscopy (EDS) and X-ray diffractometry (XRD), showing a layer thickness between 90 to 300 μm. These coated substrates were introduced in an oxidation test at 1000°C for 240 hours, revealing an optimization in the oxidation resistance by the formation of the Al2O3 oxide layer, revealing a reduction in mass gain around 3.4 times for the layers formed in the HAPC 900 and 1000°C processes.

2
  • DEMARCUS WERDINE
  • Statistical analysis of the properties of self-compacting concrete mixed with tire rubber waste.

  • Leader : MIRIAN DE LOURDES NORONHA MOTTA MELO
  • MEMBRES DE LA BANQUE :
  • GUILHERME FERREIRA GOMES
  • MIRIAN DE LOURDES NORONHA MOTTA MELO
  • PAULO CESAR GONCALVES
  • ROSA CRISTINA CECCHE LINTZ
  • VALQUIRIA CLARET DOS SANTOS
  • VANDER ALKMIN DOS SANTOS RIBEIRO
  • Data: 27 juil. 2021


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  • The present work aims to analyze the influence of the incorporation of rubber waste from scrap tires (RWT) in different contents and granulometries, in partial replacement for sand, in the physical and mechanical properties of self-compacting concrete. The civil construction market and the numerous technological innovations in the area have increasingly demanded materials that have special characteristics, thus seeking, among other benefits, the improvement in the durability and performance of the structures. Thus, concrete, the main construction material used today and the second most used in the world, has been the target of many researches and experiments. It is notable that the use of self-compacting concrete (SCC) has been described by many researchers as a major revolution in concrete technology due to its fluidity and viscosity characteristics, besides providing energy savings during its construction. The different ways of using waste rubber from scrap tires in the composition of the SCC has been a subject that has been extensively explored in several researches in the area, always looking for the sustainable use of waste and the benefits that it can provide to the final product. To obtain the SCC trace, this research was based on the Gomes Method, and for the best packaging of concrete aggregates, the EMMA software (Elkem Materials Mixture Analyzer) was used. Several mixtures were prepared with 10%, 30% and 50% of RWT and with particle sizes smaller than 0.6 mm and particle sizes between 0.6 mm and 4.8 mm. In the fresh state, all mixtures were subjected to tests that met the parameters required for an SCC. In order to evaluate the mechanical behavior of concretes, the tests in the hardened state (resistance to axial compression, sclerometry, static elasticity module, immersion absorption, frequency and damping factor) were also performed at 7 and 28 days, as well as, voids index and specific mass of concretes. Finally, using the DOE methodology (Design of Experiments), an analysis was carried out and the various effects that the content and granulometry of the RWT and the curing time caused on the results of the experiments were statistically observed. Curing time was the main statistically significant factor for the results of natural frequency and damping factor. Regarding the resistance to axial compression and the static elasticity module, the factor with the greatest statistical influence was the rubber content used in the mixtures.


3
  • LUIZ HENRIQUE RIBEIRO
  • Electronic transport of InAs/GaAs samples

  • Leader : RERO MARQUES RUBINGER
  • MEMBRES DE LA BANQUE :
  • ADHIMAR FLAVIO OLIVEIRA
  • ALAN BENDASOLI PAVAN
  • MARCIA REGINA BALDISSERA RODRIGUES
  • RERO MARQUES RUBINGER
  • VANDER ALKMIN DOS SANTOS RIBEIRO
  • YVO MARCELO CHIARADIA MASSELLI
  • Data: 3 sept. 2021


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  • This work presents the study of electronic transport on a set of five multilayer molecular beam epitaxy-grown InAs/GaAs semiconductor samples. We developed an automated switch system to carry out electronic transport measurements of mobility and carrier concentration using the van der Pauw technique. The system was evaluated using an ITO sample, which is well known in the literature. In its evaluation, the system presented results consistent with the expected ones. Measurements were carried out as a function of temperature within the range of 260~K to 310~K. To identify which scattering mechanisms most contributed to mobility limitation, It was necessary to use the Self-adaptive Differential Evolution meta-heuristic method. This method allowed the determination of the main scattering mechanisms limiting the electronic mobility and identified as scattering by dislocations and phonons. Dislocations consist of the dominant defects in this lattice mismatch structure. Therefore, to increase carrier mobility, we propose some strategies: a change in the sample growth parameters such as substrate temperature and InAs/GaAs layer thickness. Alternatively, annealing of the samples could also be considered to improve sample mobility.

4
  • MARIA AUXILIADORA DE BARROS MARTINS
  • Rheological properties and durability of high-strength self-compacting concrete with marble and granite cutting waste and foundry exhaust sand

  • Leader : MIRIAN DE LOURDES NORONHA MOTTA MELO
  • MEMBRES DE LA BANQUE :
  • LUISA ANDREIA GACHET BARBOSA
  • MIRIAN DE LOURDES NORONHA MOTTA MELO
  • PAULO CESAR GONCALVES
  • REGINA MAMBELI BARROS
  • ROSA CRISTINA CECCHE LINTZ
  • VALQUIRIA CLARET DOS SANTOS
  • Data: 21 oct. 2021


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  • Self-compacting concrete, SCC, is practically a new concrete that has peculiar characteristics of fluidity and viscosity. To acquire such properties, it uses in its composition, mineral additions, fine materials, which, in large part, are industrial waste and, therefore, a sustainable material. Although the use of waste foundry sand (WFS) in concrete is already widespread, there is a gap regarding the waste foundry exhaust sand (WFES) and its influence on the reinforcement and, thus, producing a concrete that meets the prerogatives of compressive strength, durability, longer useful life and sustainability. In this research, the marble and granite processing waste residue, MGPW, was used as a mineral addition to improve the mixture viscosity, and waste foundry exhaust sand (WFES) as a partial substitute (10%, 20%, 30%, 40 % and 50%) of natural sand. Foundry Exhaust Sand makes up the WFSs, which correspond, on average, to 80% of the waste generated in the foundry industry. The influence of materials on concrete rheology, strength and durability was evaluated. Rheological parameters were tested by empirical methods. Mechanical properties were evaluated by compressive strength and splitting tensile strength. As indicators of durability, the tests of water absorption by immersion and capillarity, resistance to sulfates and acids attacks, bulk electrical resistivity, chloride permeability and corrosion potential were used. In fresh state, all mixtures presented fluidity and viscosity characteristics required by brazilian standard for SCC. As for compressive strength, all mixtures were classified as high strength. Mixtures showed good resistance to acid and sulphate attacks, low absorption by immersion in water and by capillarity. Very low permeability to chloride ions and high electrical resistivity, indicates the mixtures showed a negligible probability of corrosion and in the corrosion potential test the probability varied between uncertain and low. These results indicated that SCC with MGPW and FES has lower permeability to harmful agents and, consequently, greater durability when compared to reference concrete. All properties were improved with 30% of FES waste, although good results were obtained with up to 40%. In this sense, the use of these waste brings environmental benefits that translate into both the reduction of waste deposited in landfills and the reduction in the extraction of natural sand. the results show that the wastes, WFES and MGPW, can be used without affecting the concrete durability.

5
  • ALEXANDRE FLAUZINO JUNIOR
  • Chitosan lactate and NPsAg nanocomposites with antimicrobial activity

  • Leader : MARIA ELENA LEYVA GONZALEZ
  • MEMBRES DE LA BANQUE :
  • GUILHERME MARIZ DE OLIVEIRA BARRA
  • ALVARO ANTONIO ALENCAR QUEIROZ
  • BLUMA GUENTHER SOARES
  • FABIO DA SILVA LISBOA
  • MARIA ELENA LEYVA GONZALEZ
  • MARIA FERNANDA XAVIER PINTO MEDEIROS
  • Data: 25 oct. 2021


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  • The chemically modified of chitosan lactate are among the chitosan derivatives that have much superior non-cytotoxic properties when compared to other chitosan derivatives. Chitosan lactate, has a solubility close to physiological pH (pH=7.0) which significantly improves its applications in controlled drug release systems. Chitosan lactate has been proposed for various biomedical applications as wound dressings and dental membranes. In the present work, the synthesis of chitosan lactate from methyl and ethyl lactate with chitosan was performed, the modification was proven by the techniques of infrared spectroscopy with Fourier transform (FTIR), thermogravimetric analysis (TGA), calorimetric differential scanning (DSC), proton nuclear magnetic resonance (1H NMR). The characterization techniques of DSC and 1H NMR showed that in the chemical modification of chitosan in addition to chitosan lactate grafts of poly(lactic acid) oligomers were obtained in the chitosan chain (QUI-g-PLA). Electrospinning of chemically modified chitosan QUI-g-PLA containing the complex of chondroitin sulfate (SC) and silver nanoparticles (NPsAg) was performed and then the controlled release of silver nanoparticles and chondroitin sulfate was studied, since the nanoparticles silver have antimicrobial activity and chondroitin sulfate has cell proliferation properties. The study of antimicrobial activity was carried out, which showed inhibition for both Gram positive and Gram negative bacteria and a cytotoxicity study was also carried out, showing that the produced nanofibers do not have a negative effect on cell viability, actually showing an increase in cell proliferation. So far, the author of this doctoral proposal has not observed any work that mentions the use of QUI-g-PLA/SC:NPsAg nanofibers as dressings, on this aspect it seems to be important to develop dressings for the treatment of wounds in its various modalities: burns, contact wounds, among others, which have antimicrobial properties combined with increased healing of cell tissue.

6
  • NÁDIA ALVES NERY BALBINO
  • Comparative Study of the Corrosion Resistance of WC-NiMo, WC-NiCr and WC-Co Cemented Carbides

  • Leader : EDMILSON OTONI CORREA
  • MEMBRES DE LA BANQUE :
  • CARLOS ALBERTO CARVALHO CASTRO
  • EDMILSON OTONI CORREA
  • GEOVANI RODRIGUES
  • GLAUCO JOSE RODRIGUES DE AZEVEDO
  • JEAN CARLO CESCON PEREIRA
  • SERGIO SOUTO MAIOR TAVARES
  • Data: 5 nov. 2021


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  • Cemented carbide is a composite material consisting of hard ceramic particles embedded in a ductile metal matrix, called the binder phase. These materials exhibit a unique combination of mechanical properties, having several engineering applications. Currently, cobalt is the binder that dominates the cemented carbide market due to better mechanical properties. However, due to the high cost, scarcity and the search for cemented carbides with greater corrosion resistance, an alternative binder phase has been researched. Nickel is an exciting and promising candidate but, the mechanical properties of WC-Ni cemented carbides are relatively inferior to those of WC-Co cemented carbides. Thus the addition of alloying elements, such as molybdenum and chromium, has been studied in order to promote the strengthening of the WC-Ni alloys by using solid solution techniques. The aim of this work is to evaluate the corrosion resistance of WC-NiMo, WC NiCr and WC-Co cemented carbides, obtained by conventional powder metallurgy. The sintered sample was characterized, , before and after corrosive tests, by the analysis in optical microscopy (OM), scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD. Microhardness was measured by the Vickers microhardness method. The corrosion resistance of the cemented carbides was investigated by open circuit potential, potentiodynamic polarization, electrochemical impedance spectroscopy and static immersing corrosion test, in a 3.5 wt.% NaCl solution. The WC-Ni cemented carbides showed microstructures similar to those of conventional cemented carbides, WC-Co. However, pores and binder islands were observed in the microstructures, which leads to inferior mechanical properties, such as Vickers microhardness. The corrosion tests had promising results, the WC-NiMo e WC-NiCr cemented carbide showed superior corrosion resistance and higher passivation capacity than the WC-Co cemented carbide. The WC-NiMo cemented carbide was the material with the best performance, as it maintained good mechanical properties and presented the noblest corrosive behavior among the studied materials.

7
  • MATHEUS JOSE DA SILVA
  • Study of Electrical Transport Properties in ZnO/CdO-based heterostructures

  • Leader : DEMETRIO ARTUR WERNER SOARES
  • MEMBRES DE LA BANQUE :
  • ADHIMAR FLAVIO OLIVEIRA
  • DEMETRIO ARTUR WERNER SOARES
  • MARCELOS LIMA PERES
  • MÁRCIO PERON FRANCO DE GODOY
  • SANDRA NAKAMATSU
  • WAGNER SOUZA MACHADO
  • Data: 26 nov. 2021


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  • This work presents a study on the electrical transport properties of ZnO/CdO semiconductor heterostructures grown by the Spray Pyrolysis (SP) technique, as well as a morphological characterization of the samples. Magnetotransport measurements performed with the ZnO/CdO sample grown on silicon (Si) showed Shubnikov de-Haas (SdH) quantum oscillations associated with the depletion region formed at the interface between zinc and cadmium oxides, which may be related to a confinement of a two-dimensional electron gas. Such nonphenomenon was observed in the sample grown in glass. From the analysis of oscillations, it was possible to compare magnetoresistance (MR) measurements between those grown on silicon and glass, leading to the understanding that the formation of two-dimensional gas is related to the crystallinity of the silicon substrate. The structural and morphological properties were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), allowing to verify differences between oxide deposits on the surfaces of glass substrates and silicon, indicating that the oxide deposited on silicon substrate has better crystallinity. Hall Effect characterization results between temperatures of 300 K and 77 K for three CdO samples grown on Si substrate by the SP technique are also presented. Of these samples, two underwent a heat treatment process in an atmosphere at 500ºC, one submitted to an atmosphere of O2 and the other one in N2. The morphological characterization of these samples was also performed by the techniques of XRD, SEM and EDS. It was verified by the XRD technique that for samples submitted to heat treatment, there was an increase in crystallite size, and this leads to a change in the surface of the films, confirmed by SEM and EDS. These morphological changes lead to a variation in electrical properties confirmed by the Hall Effect and photoconductivity.

8
  • GILZA CARLA RIBEIRO
  • Development of PVDF/BaTiO3 and P(VDF-TrFE)/BaTiO3 Composite Membranes with Piezoelectric and Antimicrobial Properties for Biomedical Applications

  • Leader : DANIELA SACHS
  • MEMBRES DE LA BANQUE :
  • RAQUEL MARIA LIMA LEMES
  • AMANDA DE CARVALHO PEREIRA MORAES
  • DANIELA SACHS
  • MARIA ELENA LEYVA GONZALEZ
  • PATRÍCIA CAPELLATO
  • ROSSANO GIMENES
  • Data: 14 déc. 2021


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  • Wounds are consequences of any disruption of the structure and normal functions of the integument as a result of trauma. The treatment of chronic wounds requires high costs for dressings, healthcare professionals and hospital stays. Chronic wounds can be infected by microorganisms, making the healing and healing process difficult. In order to promote the healing of infected wounds, dressings containing silver are developed. Silver is a metal with antimicrobial properties, widely used in the treatment of chronic wounds. The PVDF polymer and its composites are promising biomaterials due to their biocompatibility and their piezoelectric, pyroelectric and ferroelectric responses. The mixture of polymers and ceramics generates materials with potential capacity for tissue regeneration, combining characteristics of resistance, flexibility and easy processability of polymers and strong piezoelectric responses of ceramics. The present work aims to develop PVDF/BaTiO3 and P(VDF-TrFE)/BaTiO3 membranes with piezoelectric and antimicrobial properties for applications in wound treatment. Therefore, after making the membranes, silver impregnation was carried out in some samples. For the characterization of the material, physical chemical and microstructural techniques of isolated composites and impregnated with silver were used. The contact angle measurement was used to assess the hydrophilicity of the material, the hemocompatibility was assessed with the hemolysis test and the antimicrobial activity of the membranes was assessed by the diffusion method on Kirby Bauer agar and biofilm formation using ATCC strains of Staphylococcus aureus and Pseudomonas aeruginosa. Characterization tests demonstrated that the membranes were synthesized with piezoelectric properties and that the silver was successfully impregnated. Contact angle measurements confirmed the hydrophilicity of the material and hemocompatibility tests showed that the membranes can be used in contact with blood. The microbiological tests showed that PVDF/BaTiO3 and P(VDF-TrFE)/BaTiO3 membranes showed antimicrobial activity after silver impregnation, which makes the material promising in the treatment of chronic infected wounds.

9
  • ISABELA CRISTINA FERNANDES VAZ
  • CERIA-BASED GAS SENSOR MODIFIED WITH Nd PREPARED BY HYDROTHERMAL ASSISTED BY MICROWAVE FOR DETECTION OF CARBON MONOXIDE

  • Leader : FRANCISCO MOURA FILHO
  • MEMBRES DE LA BANQUE :
  • EDUARDO ANTONELLI
  • FRANCISCO MOURA FILHO
  • MARCIO MARTINS LAGE JUNIOR
  • RERO MARQUES RUBINGER
  • RODOLFO FOSTER KLEIN GUNNEWIEK
  • Data: 17 déc. 2021


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  • Carbon monoxide gas (CO) is one of the main air pollutants emitted directly from human activities. This gas is particularly dangerous because it is imperceptible and has no specific symptoms: victims fall ill or even die before they realize they have been exposed to it. It can only be detected using a sensing device. Cerium oxide has several applications due to its high conductivity of oxygen ions and one of them is as CO sensors that use cerium oxide films and catalysts. In this work, ceramic powders were synthesized by the microwave-assisted hydrothermal method, obtaining pure cerium oxide nanoparticles doped with different molar percentages of neodymium (0; 4; 8 and 12 mol %). XRD patterns, Raman and FT-IR spectra indicate the formation of crystalline solid solutions with a fluorite-like cubic structure, belonging to the Fm3m space group. The microscopy images indicated that the dopant decreases the size of the particles being highly agglomerated and with primary particulate in the nanometric scale. The UV-Vis spectra indicated the existence of Ce3+ and Nd4+ ions, generating oxygen vacancies that reduce the bandgap. Positron annihilation spectroscopy studies were also conducted, which showed that as the Nd content increases, there is a structural disturbance caused by an increase in the oxygen vacancies surrounded by Nd (defective clusters). Finally, sensing measurements were carried out for the cerium oxide nanoparticles, where it is observed that the analyzed samples have a fast response and recovery time at 400 °C and a good selectivity to CO, revealing that the synthesis method was efficient in the obtaining samples that have great potential to be applied as carbon monoxide sensors.

2020
Thèses
1
  • LUCAS RAMON ROQUE DA SILVA
  • Analysis of properties of self-compacting concrete with addition of polymeric residue

  • Leader : MIRIAN DE LOURDES NORONHA MOTTA MELO
  • MEMBRES DE LA BANQUE :
  • CARLOS BARREIRA MARTINEZ
  • MIRIAN DE LOURDES NORONHA MOTTA MELO
  • ROSA CRISTINA CECCHE LINTZ
  • VANDER ALKMIN DOS SANTOS RIBEIRO
  • Data: 20 févr. 2020


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  • Concrete after water is the most used material in the world, and to obtain it there is a need to use natural inputs that are increasingly scarce. Electro-electronic waste, from equipment such as refrigerators and freezers, is the fastest-growing category of waste in the world). An alternative for the correct disposal of household appliance waste is its use in concrete as an aggregate, which generates concrete with special characteristics. This work aims to produce self-compacting concrete (CAA) modified with polymeric residues from the recycling of refrigerators and characterizes them in terms of their main properties. The physical, mechanical and microstructural characteristics were evaluated. One reference line was produced, without substitution of polymeric residue (RP) and four with substitution of (RP) with 5%, 10%, 15% and 20% by the coarse aggregate. In the fresh state, the tests were visual stability index (IEV), slump flow test (Abrams cone), flow time (t500), passing ability (box L), viscosity (funnel V) and fresh density. In the hardened state, the tests were resistance to axial and diametrical compression, water absorption, voids index, specific mass, dynamic elastic modulus, scanning electron microscopy (SEM) and electrical resistivity. In the fresh state, the CAA maintains its characteristics of homogeneity and fluidity until the replacement of 20%. In the hardened state, the addition of RP acted to gradually decrease the strength of the concrete in the tests of resistance to axial compression and resistance to diametrical compression. However, even with the decrease, all mix are classified for medium and high strength structural purposes ABNT NBR 8953: 2015. With the replacement of RP the modulus of elasticity decreases, thus the stiffness of the CAA decreases. The reverse occurs for the electrical resistivity that increases with RP replacement, making it CAA insulating and less prone to deterioration by the action of ions, less susceptible to the corrosion process that can occur in reinforced concrete. In the MEV test, it can be seen that as the percentage of PR increases, the transition zone in the interphase (ZTI) becomes porous and without cohesion at several points, and there are spaces of significant vacancies. These facts added up that justify the decrease in the mechanical properties of the CAA. From the results obtained, it is concluded that the production of CAA with substitution of RP by the coarse aggregate is possible.

2
  • Josimara Aparecida da Silva
  • Rheology of cement pastes with rice husk ash

  • Leader : ANTONIO JOSE FARIA BOMBARD
  • MEMBRES DE LA BANQUE :
  • ALESSANDRA LORENZETTI DE CASTRO
  • ANDERSON PAULO DE PAIVA
  • ANTONIO CARLOS ANCELOTTI JUNIOR
  • ANTONIO JOSE FARIA BOMBARD
  • Data: 1 juil. 2020


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  • With urban expansion and population growth, currently the consumption of Portland cement has increased, as well as environmental concerns and the search for solutions to mitigate its use. Rice husk ash is an agro-industrial residue, which is often discarded inappropriately in the environment, and presents itself as an alternative material for use in cementitious matrices. In order to reduce this environmental liability and bearing in mind that the production of Portland cement is highly polluting, the use of rice husk ash (RHA) in partial replacement for cement was analyzed in this research. This study dealt with the rheological analysis of thirteen cement pastes, maintaining the residue substitution content equal to 10% and a constant water-to-cement ratio w/c = 0.45 with different contents of two chemical additives. A Silicon® NS viscosity modifier type admixture was used - an aqueous solution of nanosilica, in the range of 1.2% to 2.8% w/w (on the weight of the cement), and a type III superplasticizer, MasterGlenium® ACE 409 composed of modified polycarboxylate ethers, in the range of 0.2 to 0.6% w/w in cement pastes. These different formulations were evaluated by response surface methodology in order to find a feasible composition, which presents good workability, low plastic viscosity, with reasonable yield stress, for future applications in self-compacting mortars and concretes. For that, both the oscillatory and rotational rheometry tests were performed, as well as the results of the mini-slump test, the flow time in the Marsh Funnel and the compressive strength of the thirteen formulations. A feasible composition was obtained with 0.497% w/w of superplasticizer (additive 1) and 2.444% w/w of the viscosity modifying admixture. This formulation was prepared and tested, and elastic modulus values = 1630 Pa, yield stress = 16 Pa, plastic viscosity = 0.19 Pa.s, thixotropic recovery after 1 minute = 65%, spreading diameter = 126.5 mm and flow time through the Marsh Funnel = 8.06 s. It was found that the chemical admixtures used did not affect the compressive strength, while replacing the cement with 10% CCA increased the compressive strength by ≈ 29.4% at 07 days of curing and by ≈ 16.06% at 28 days of curing in relation to the control group.

3
  • SAMUEL REZENDE BUSTAMANTE
  • Optical Sensor for Milk Quality Analysis

  • Leader : ALVARO ANTONIO ALENCAR QUEIROZ
  • MEMBRES DE LA BANQUE :
  • ALVARO ANTONIO ALENCAR QUEIROZ
  • CREDSON DE SALLES
  • EDSON GIULIANI RAMOS FERNANDES
  • Data: 6 juil. 2020


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  • With the increase in milk sanitary control measures, the obligation of the milk producer to control the quality of its production grows. Along with quality control, rural producers find it difficult to obtain practical and reliable information on the quality of their herd's milk and thus adapt it to the animals' diet. With the personalized diet, it is possible to increase the productive life of your cows, the efficiency of feeding and the valorization of your milk through the increase of quality. In this context, the present work aims to develop a practical and fast sensor for monitoring the fat rate of raw milk. Through studies of the physical and chemical properties of the main analytical characteristics of milk of interest to the market, it was noted that in milk sample the fat globules showed significant absorption of the infrared spectrum. With this, a device was developed that operates on the wavelength sensitive to milk fat, irradiating the sample to be analyzed and simultaneously measuring the absorption of irradiation by the sample. The validation of the created device was done through the analytical method, presenting the linearity of the measurement of the fat content similar to the measurement method in the Gerber butyrometer. The device validation process proved satisfactory, with the possibility of being used in the field.

4
  • THIAGO DONATO JOAQUIM
  • Study of the Influence of Simple and Duplex Aging on Corrosion Behavior of Alloy Ti-6Al-4V

  • Leader : EDMILSON OTONI CORREA
  • MEMBRES DE LA BANQUE :
  • ELIVELTON ALVES FERREIRA
  • EDMILSON OTONI CORREA
  • FELIPE DE SOUZA ELOY
  • Data: 4 sept. 2020


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  • Currently the Ti-6Al-4V alloy, which represents 90% of the titanium used in the aeronautical industry thanks to combinations of attractive properties such as workability, machining and resistance at high temperatures. Mainly used for applications that require resistance to high temperatures, as these conditions have high susceptibility of phase precipitation directly impacting on its mechanical properties and resistance to corrosion of the alloy due to considerable microstructural changes. The α + β alloys have a very sensitive property/microstructure relationship, their properties are greatly influenced by the morphology proportions and distribution of the α and β phases. The samples of this alloy were solubilized and subjected to simple and duplex aging, and these conditions were analyzed for electrochemical behavior by means of corrosion testing in a 2M HCl solution, resulting in a drop in corrosion resistance of the alloy with current densities of 2.8x10-4 A.cm2 (simple aging) and 3.08x10-4 A.cm2 (duplex aging). Optical microscopy techniques were also used where it was possible to observe the formation of the αp (primary alpha), βt (transformed beta), β metastable phases in the solubilization of the samples and, in the aged samples, the presence of allotiomorphs α phase, Widmanstätten structure, precipitation and growth of α phase in the center of the grains. The samples submitted to aging showed less resistance to corrosion, suffering corrosion throughout the test and without formation of passive layer.

5
  • LUCAS EDUARDO RIBEIRO FARIA
  • Analysis of the Dynamic Behavior of Sandwich Beams with Honeycomb Core Filled with Magneto Rheological Gel

  • Leader : ANTONIO CARLOS ANCELOTTI JUNIOR
  • MEMBRES DE LA BANQUE :
  • ANTONIO CARLOS ANCELOTTI JUNIOR
  • ANTONIO JOSE FARIA BOMBARD
  • GUILHERME FERREIRA GOMES
  • LUIZ CLAUDIO PARDINI
  • Data: 2 oct. 2020


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  • With the rapid advancement of technology comes the need for lighter weight and higher strength materials, so studies on new materials and manufacturing techniques are needed. The aeronautics industry is always at the forefront of researching new materials, where the weight factor is crucial. In contrast, aircraft suffer from intense mechanical vibration and the ability to control these vibrations is of paramount importance for stability. of the aircraft and its structural integrity. To control these intense vibrations, intelligent materials have been pointed as a possible resource for vibration control, since it is possible to vary the modal frequencies of the structure through electrical or magnetic excitations. The objective of this dissertation is to analyze the dynamic behavior under the influence of vibrations in sandwich beams, which have honeycomb cores filled with rheological magnet gels and composite material skins. The development of the work has an experimental analysis through free and forced vibration tests to determine the modal parameters of the beams built according to the applied magnetic field intensity, and a statistical analysis to determine the factors that most impacted this process. With the results obtained, the use of these materials is promising in structures, due to the fact that they achieve reductions in the value of natural frequencies in the order of 54%, increase in damping factors of up to 390% and decrease in forced vibration amplitude of 40%. % in relation to the use of a magnetic field. Resulting from the statistical analysis showed that the factor that most influenced the response of free and forced vibration assays was the gel. In the conclusion of this dissertation, it is proposed new models of beams, since there are few studies in the honeycomb core filled with rheological magnet gel.

Thèses
1
  • FELIPE MORETON CHOHFI
  • Development of an internal container for Liquefied Petroleum Gas

  • Leader : FILIBERTO GONZALEZ GARCIA
  • MEMBRES DE LA BANQUE :
  • ALEXANDRE ZIRPOLI SIMOES
  • ANTONIO CARLOS ANCELOTTI JUNIOR
  • DANILO ROQUE HUANCA
  • FILIBERTO GONZALEZ GARCIA
  • RICARDO MELLO DI BENEDETTO
  • Data: 30 janv. 2020


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  • A container for the storage of LPG of type IV was developed with polymeric materials reinforced with composite materials using different technological processes such as injection molding, hot plate welding, filament winding and vacuum co-injection molding. In addition to being light, the container is ecological and has better resistance to corrosion. A problem of this container is that it permits high levels of gas permeation and accumulation of electrostatic charge, problems that prevent the substitution of the metallic container. This is the main objective of this work. Initially different materials were studied: high density poly(ethylene), HDPE, poly(propylene), PP, poly(ethylene terephthalate), PET and poly(amide), PA to assess their mechanical properties in stress versus strain, thermal transitions, resistance to n-pentane and permeability to oxygen. The mechanical results showed that HDPEs deform at low stress, however PET is more rigid. In addition, the HDPEs maintained their thermal properties after being submitted to technological processes. In particular PP presented an increase in mass (13%) after immersion in n-pentane to a level above that permitted. The permeability calculations show that the HDPE that was selected to produce the container is permeable to gas, in a value above that allowed. In this way the idea of using an internal barrier film that is impermeable was proposed. Functional tests were performed with the container to assess the pressure in rupture and cycles pressure test, impact, fire and electrostatic discharge. The container with barrier film has taken the pressure cycles, impact and fire tests considering the criteria found in the norms. However, after the electrostatic discharge tests, a reduced charge transfer was found in the internal part of the container where the barrier film was placed. This behavior has been eliminated by inserting a pressure valve that fills the container differently from the traditional way.

2019
Thèses
1
  • THAÍS MARCIAL LUIZ
  • Synthesis of Nb2O5 nanoparticles for application in oxide dispersion
    strengthened materials.

  • Leader : RENY ANGELA RENZETTI
  • MEMBRES DE LA BANQUE :
  • FABRÍCIO VIEIRA DE ANDRADE
  • GUILHERME OLIVEIRA SIQUEIRA
  • RENY ANGELA RENZETTI
  • RONEY EDUARDO LINO
  • Data: 6 juin 2019


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  • Oxide dispersion strengthened metals (ODS) were developed to improve the hardness and creep
    resistance of alloys at elevated temperatures through the uniform distribution of oxide
    nanoparticles in the metal matrix. The present work aims at the production of ODS metal with
    addition of niobium pentoxide nanoparticles, and it was developed in two parts. The first part
    consisted in an innovative way of synthesizing the niobium pentoxide by microwave assisted
    combustion reaction using ammonia oxalate of niobium (precursor), urea (fuel) and ammonium
    nitrate (oxidizer). Four syntheses were made with variable amount of fuel and oxidizer. In all
    syntheses, it was obtained mainly particles of niobium pentoxide in the orthorhombic phase
    with nanometric size, as demonstrated by X-rays diffraction and transmission electron
    microscopy. However, it was noted that the high amount of oxidizer influenced the size of the
    particles, producing smaller particles. This result was confirmed by the band energy values
    obtained by diffuse reflectance spectroscopy in the UV-Vis region and the full width half
    maximum of the peak (001) values obtained by Rietveld refinement. The synthesis with the
    best results was reproduced for incorporation of the niobium oxide in the iron, starting then the
    second part of the work corresponding to the production of the ODS metal by powder
    metallurgy. Samples with different concentrations of niobium pentoxide (0,25, 0,5, 1,0, 5,0 and
    10,0 wt%) were produced and then cold rolled. The results showed that the addition of
    nanoparticles of niobium pentoxide did not influence the formation of inclusions and pores in
    the microstructure as well as the nucleation of cracks during rolling. However, the synthesis
    conditions and the concentration of niobium pentoxide led to the formation of niobium and iron
    oxides. Despite this reaction, representative samples were analyzed by transmission electron
    microscopy and the results confirmed that both oxides coexist in the matrix and the nanometric
    size is maintained after sintering. Finally, the Vickers hardness tests showed positive results for
    the incorporation of niobium pentoxide in concentrations between 0.25 and 1.0 wt% in the iron
    matrix, promoting effective hardening in these samples.

2
  • EVERSON JUNIO DA CRUZ FERREIRA
  • CARACTERIZAÇÃO MORFOLÓGICA E ESTRUTURAL DO COBALATO DE CÁLCIO DOPADO COM MOLIBDÊNIO.

  • Leader : FRANCISCO MOURA FILHO
  • MEMBRES DE LA BANQUE :
  • FRANCISCO MOURA FILHO
  • RERO MARQUES RUBINGER
  • HAROLDO LHOU HASEGAWA
  • RODOLFO FOSTER KLEIN GUNNEWIEK
  • Data: 21 juin 2019


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  • ince the 1990s, ceramic materials have demonstrated their potential in the generation of
    electric energy through the application of a temperature gradient due to its good chemical and
    dimensional stability. These materials have aroused the interest of the literature as a candidate
    for the substitution of classical thermoelectric materials based on metallic alloys as they exhibit
    thermoelectric behavior in upper temperature ranges (500ºC or more). This characteristic is not
    well established in the classic thermoelectric. In the present work, we propose to investigate the
    influence of the structure and morphology of the thermoelectric ceramics of calcium cobalate,
    in addition to the addition of dopant (molybdenum), in the properties of thermal and electrical
    conductivity of the material, at room temperature. For these reasons, in this project, Ca3Co4(1-
    x)MoxO9 ceramic powders were obtained by the traditional oxide mixture method, and
    concentrations of 0.5, 1, 2 and 2.5% molybdenum were added to the material to replace cobalt.
    The thermogravimetry revealed a slight thermostability between the temperatures of 800ºC and
    900ºC which were then defined as the temperatures of the calcination of the material. The Xray diffraction analysis showed a long-range structural ordering of Ca3Co4(1-x)MoxO9,
    identifying the desired phase (Ca3Co4O9) and the presence of secondary phases (CaO and
    Co3O4) at temperatures of 800 and 900ºC. The presence of the incorporated molybdenum in the
    material structure can be observed in a slight left angular displacement of the diffraction peaks.
    Infrared spectroscopy revealed a short-range structural organization in which the vibrational
    modes of stretching belonging to Ca3Co4O9 and the second phases vibrational modes were
    identified. The results of the dilatometry suggested the sintering of the Ca3Co4(1-x)MoxO9 pellets
    at temperatures of 1050ºC and 1250ºC. They were also submitted to density and green density
    analysis by the Archimedes principle, showing high densification in samples treated at 1250ºC
    (97%), while the samples treated at 1050°C reached intermediate densities (70%). The images
    obtained by scanning electron microscopy evidenced the presence of more defined and
    homogeneous grains and larger average grain sizes compared to the samples treated at 1250ºC.
    This samples in turn presented grains with heterogeneous appearance. The values of electrical
    conductivity were higher in the sintered samples at 1050ºC and, generally, lower with the
    molybdenum concentration increase. Finally, the values obtained in the thermal conductivities
    were higher in pellets treated at 1250ºC than in samples treated at 1050ºC.

3
  • NELSON GUSTAVO ALVES PEREIRA
  • SYNTHESIS, CHEMICAL MODIFICATION AND CHARACTERIZATION OF ELECTROCHEMICAL PREPARED GRAPHEN OXIDE
  • Leader : MARIA ELENA LEYVA GONZALEZ
  • MEMBRES DE LA BANQUE :
  • ADHIMAR FLAVIO OLIVEIRA
  • ALVARO ANTONIO ALENCAR QUEIROZ
  • CHARLENE APARECIDA RIBEIRO
  • MARIA ELENA LEYVA GONZALEZ
  • Data: 5 juil. 2019


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  • The graphene is a material of 21st century with excellent mechanical, optical and electrical properties, with wide variety of technological applications and whose raw material is an abundant material in nature. However its large-scale production is still a challenge for science. Therefore, the aims of this Master's thesis was to study a simple methodology capable of preparing graphene oxide (GO) from electrochemical graphite exfoliation, as well as its functionalization with phthalic anhydride (f-GO) and subsequent doping with Cu2+ and Ag+ ions. The electrochemical graphite (as anode) exfoliation was performed in electrochemical cell using H2SO4 1M as electrolyte and positive potential of 2.3V, this potential was gradually increased up to 10V. The graphene oxide obtained was characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), infrared absorption spectroscopy (FTIR), UV-vis spectroscopy, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM). All characterization techniques confirmed the incorporation of functional groups containing oxygen (hydroxyl, carboxyl and epoxy), confirmed therefore the oxidation of graphite. The confirmation of graphite exfoliation to graphene oxide was obtained by XRD. XRD spectrum shows the diffraction peak of the graphene in 2θ = 9.1°. The MEV shows morphology of overlapping layer of graphene. The study of the electrical conductivity (σ, S/m) with temperature (T, K) confirmed the obtention of graphene oxide too,showing the curve σ versus T a semimetal behavior of graphene.The functionalization of GO with phthalic anhydride was confirmed by FTIR. The FTIR spectrum showed a decresed of OH groups concentration on f-GO. The doping of f-GO was confirmed by MEV-EDS. The MEV showed a morphology of corrugated graphene sheets, the EDS confirmed a presence of Cu2+ and Ag+ ions on the surface of f-GO. The dependence of conductivity with temperature of doped f-GO samples showed a semimetal and semiconductor behavior. The values of the conductivity in f-GO/Ag+ increased ½ order of magnitude in relation to the GO.

4
  • LEONARDO GOMES DE OLIVEIRA
  • SYNTHESIS, STRUCTURAL AND MORPHOLOGICAL CHARACTERIZATION OF LEAD-FREE FERROELECTRIC CERAMICS KNaNbO3 - SODIUM AND POTASSIUM NIOBATE, MODIFIED WITH MOLIBDENIUM [K0,5Na0,5][Nb(1-x)Mo(x)]O3

  • Leader : FRANCISCO MOURA FILHO
  • MEMBRES DE LA BANQUE :
  • CARLA PATRICIA LACERDA RUBINGER
  • EDUARDO ANTONELLI
  • FRANCISCO MOURA FILHO
  • MARCIO ROBERTO DE FREITAS
  • Data: 5 juil. 2019


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  • This work seeks a solution or substitution for lead-free ceramics, which have characteristics
    close to the structure of perovskite PZT (Lead Zirconate Titanate). The ceramic was produced
    from Potassium and Sodium Niobate; KNN - Na0.5K0.5NbO3; with changes in site B by
    molybdenum (Mo). In this work, solid solutions of Na0.5K0.5Nb(1-x)MoxO3 were sintered with
    x = 5%; 10%; 15% and 20%mol Mo by solid state reactions. With the milling, calcination,
    isostatic pressing and synthesis at high temperatures, samples of the ceramic bodies were
    obtained and the influence of the calcination temperature at 800°C, 850°C and 950°C and
    after sintering at 1100°C. The thermal analysis measurements were performed using the TG,
    DTG, DTA and Dilatometry techniques to indicate the temperature at which the samples
    suffered mass loss and maximum densification temperature, in order to better define the
    sintering temperature. Afterwards the samples were analyzed and the phases obtained for the
    perovskite structure were identified. With the X ray diffraction technique, they indicate that
    the samples contain the desired phases for Na0.5K0.5NbO3, as well as Na0.5K0.5Nb(1-x)MoxO3
    and coexisting the precursors. However, “Morphotropic Phase Boundary” (MPB) phases were
    observed between structures with monoclinic and tetragonal symmetry. Microscopy analyzes,
    obtained by Scanning Electron Microscopy (SEM), showed a microstructure with spherical
    grains, typical of the reaction of the solids close to ≈ 4,2 μm. The ceramics obtained by the
    traditional method of oxidation mixture presents morphological and structural characteristics
    with phases related to the solid solution of KNb(1-x)Mo(x)O3 according to type PDF#81-2374
    and composition for Na0,5K0,5Nb(1-x)Mo(x)O3 as identified in PDF#77-0038.

5
  • ANA CAROLINA DIAS SILVA
  • Study of the influence of surface alteration on non-molecularly ordered cellulose nanocrystals of P3HT

  • Leader : FRANCISCO MOURA FILHO
  • MEMBRES DE LA BANQUE :
  • APARECIDO JUNIOR DE MENEZES
  • EVANDRO AUGUSTO DE MORAIS
  • FRANCISCO MOURA FILHO
  • MERCES COELHO DA SILVA
  • Data: 6 août 2019


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  • The nanocrystalline cellulose (CNC) are rigid particles that have morphology similar to canes. From a certain critical concentration value CNC in water suspension act as liquid crystals with chiral nematic ordering, which can be preserved in the material during slow drying. Because of these properties, CNC have been used as substrates for obtaining conductive polymer films with greater alignment of their polymer chains, since the increase of regions ordered in the macromolecular structure of these polymers has an influence on the optical and electrical efficiency of these polymers. However, the hydrophilic character of cellulose, its insolubility (even in polar solvents) and tendency to agglomeration resulting from intermolecular hydrogen bonds, promote phase separation when these are added to non-water-soluble polymers, promoting loss of ownership of the final material. In order to address this disadvantage, the chemical modification of the cellulose surface can be a strategy to chemically align it with hydrophobic conjugated polymers. Thus, this work aims to study the influence of CNC whose surfaces were esterified with 3-thiophenoacetic acid (3TAA), on the chemical, structural, electrochemical, optical and electrical properties of poly (3-hexyl thiophene) (P3HT) The CNC used in this study were extracted from a bleached pulp of Eucalyptus via acid hydrolysis whose extraction yield was 55% m/m. CNC presented a crystallinity degree of 85% and aspect ratio (L/D) of 10 (±1). The esterification of CNC with 3TAA could be proven by the absorption band in the infrared region at 1737 cm-1, characteristic of axial deformation of C=O of ester, in addition to chemical displacements of 157 ppm and between 173 and 174 ppm, attributed respectively to the ester group carbons observed in the 13C NMR spectrum. Composites of CNC3TAA and P3HT were prepared aiming at the formation of a noncovalent interface from the physical mixture of a polymeric solution and dispersion with 10, 20, 30 or 40% m of CNC3TAA (type 1 composites) and covalent interface (type 2 composite) grafting P3HT chains from the thiophene ring of the esterified CNC added to the reactional medium in a ratio of 10 or 20% m/m. UV-Vis analysis showed that all noncovalent interface composites were displaced from maximum absorption to greater wavelengths (electrochromic displacement) and consequently lower band gap energy values relative to P3HT. For composites of type 2 only the material prepared with 10% m/m of CNC3TAA presented improvement for these results, indicating an increase in the planarity of the macromolecules of the conjugated polymer and an increase in the conjugation length of the P3HT chains as a function of the presence of the biopolymer and fibrillar morphology. As for electrical conductivity, only composites of type 1 presented higher values than the P3HT polymer. Among these, the P3HT-CNC3TAA30 composite presented the best performance, with a conductivity of 40 mS/cm to 200V 130 times greater than that obtained for the conjugated polymer (0,31 mS/cm).

6
  • ANA CAROLINA MOREIRA SILVA
  • Development of self-repair coatings with anti-corrosion function without encapsulation of pure catalyzed vegetable oils
  • Leader : RENY ANGELA RENZETTI
  • MEMBRES DE LA BANQUE :
  • DANIEL ANDRADA MARIA
  • MERCES COELHO DA SILVA
  • RENY ANGELA RENZETTI
  • RODRIGO LASSAROTE LAVALL
  • Data: 9 août 2019


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  • Corrosion process is a deteriorative and progressive phenomenon which affects especially metallic materials. It has been constantly an existing issue since the beginning of humankind, causing huge economic losses from preventive, maintenance and resources transformation actions. Currently, surfaces treatment through the application of organic coatings, such as paint and varnishes, has been the most common method avoid or minimize the corrosion effects. These coatings act as physical barrier between the surface and the environment preserving the physical integrity of the base metal. However, even in their lifespan, traditional coatings are prone to the occurrence of tridimensional defects like microcracks and fissures, which corrosion species can break through and interact with the metallic surface. Recent studies, from the 2000s, have reported the emergence of the new so-called “smart” coatings, which performance has attracted researchers’ attention. Self-healing coatings are the most known of the family and its approach is based on the encapsulation of healing agents and their incorporation into polymeric matrixes. Those capsules are responsible for healing agents’ storage and deliver it upon damage. When the defect occurs, the dispersed capsules rupture and release their content, which flows into the crack cavity due to capillary forces, filling it up. Linseed oil is currently the most used healing agents for self-healing coatings because of its high polyunsaturated fatty acids content. It is the oxidative polymerization of these oils in charge of creating a thin film which recover the damaged area, restoring the matrix physical integrity. Although never has it been used as healing agent reported in the literature, the chia seed oil possesses higher polyunsaturated fatty acids content compared to the linseed oil. In this work, linseed and chia oils have been used as healing agents in their pure form and in conjunction to a catalyst agent in order to compare both performances in self-healing coatings. Therefore, poly(urea-formaldehyde) (PUF) capsules containing both pure oils and mixed with 1% vol. of cobalt II octoate 6%, as a catalyst agent for the oils’ polymerization process, were synthesized through in situ polymerization in oil-in-water emulsion. Capsules were then incorporated and dispersed into epoxy resin and the system applied over AISI 1020 steel samples. Capsules characterization included techniques for chemical structure, thermal behavior, morphological analyses besides particle size distribution and capsules’ oil content through the oil extraction. The healing performance was evaluated simulating a crack in the coating surface using a razor. Results were obtained through microscopic images, electrochemical techniques and a visual analysis after a salt spray exposition in a salt spray chamber. Self-healing coatings with those microcapsules dispersed in an epoxy matrix showed satisfactory results indicating that healing process occurred and was efficient on protecting the substrate against corrosive mean.

7
  • THAISA SOARES CATA PRETA
  • Effect of linear magnetorresistance on extreme gap semiconductors

  • Leader : MARCELOS LIMA PERES
  • MEMBRES DE LA BANQUE :
  • ADHIMAR FLAVIO OLIVEIRA
  • MARCELOS LIMA PERES
  • SANDRA NAKAMATSU
  • SUELEN DE CASTRO
  • Data: 21 oct. 2019


  • Afficher le Résumé
  • Topological insulators are a class of materials that has been highlighted in condensed-matter physics due to its potential application in spintronics and quantum computation. Some of these materials present application in magnetic sensor devices, because of the linear response to applied magnetic field. This research analyzed the presence of linear magnetic effect doing a comparison between two quantum walls made of Pb0,54Sn0,46Te/PbTe that differ from it other by the presence of a buffer made of Pb0,89Eu0,11Te for reduce the action of strain between the substrate and PbTe layer. The aim of this work is doing a complete electric quantum wall of PbSnTe/PbTe description, hence; describe the cause of linear effect observed in magnetoresistance measurements in the range of 1,8 K to 6 K, up 9 T. Photoconductivity measurements with blue LED with a wavelength of 460 nm and 276 W/m2 of intensity were performed. It was observed transitions between positive and negative response in the photoconductivity of the two samples, the buffer sample signaled positive photoconductivity and a transition to negative one, and the sample without buffer a contrary response. To obtain the carrier concentration, resistivity and mobility, it was made Hall Effect measurements. All the results were analyzed and compared with Quantum Linear Magnetoresistance, Parish and Littlewood model that explain the results based on the classic model of mobility fluctuations, Shubnikov-de Haas oscillations that represents the presence of surface states. Lastly, theoretical interface states aspects of PbSnTe/PbTe quantum walls. Fitting the models, we conclude that linearity was not because of surface or interface states, describe the sample phenomena. Probably, the linearity was a consequence of the sample as a whole. The photoconductivity transitions can be consequence of excess defects and for a better conclusion, were proposed the calculation the rate of carrier generation and recombination, since was seen in previous work that with the recombination rate bigger than generation results in negative photoconductivity, leading to transitions. However, the behavior can be associated with weak anti-localization effect that was observed during magnetoresistance measurements or the complete set of layers.

8
  • JULIANA BARBOSA ALVES
  • Obtaining coatings with high oxide resistance in alloys Nb-Si-B by using the process “Halide Activated Pack Cementation”.

  • Leader : GEOVANI RODRIGUES
  • MEMBRES DE LA BANQUE :
  • ANTONIO AUGUSTO ARAUJO PINTO DA SILVA
  • GEOVANI RODRIGUES
  • NABIL CHAIA
  • Data: 13 nov. 2019


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  • Due to the need of obtain materials with increasingly oxide resistance at high temperatures, several studies were and are being made in refractory materials with coatings obtained by HAPC process. The refractory metals based on the elements Nb and Mo have been in evidence because these systems can create a ternary phase (T2) based on RM -Si-B (RM = Refractory Metal) that presents high melting point, relative low density, great oxidation resistance and low anisotropy of thermal expansion. Based on this fact, this work had as its objective the development of coatings for obtain high oxidation resistance in alloys from Nb-Si-B systems formed by the phases T2 and Nbss. The coating process containing Fe-Cr-Si was released on the base material with the composition 70Nb20Si10B in different conditions of time versus temperature by using Halide Pack Cementation process. The analyzed temperatures were 1100ºC e 1200ºC due to the thermodynamic simulations results that showed that these temperatures present the better deposition rate because of its halide partial pressure formed at these temperatures. The evaluated times were 12, 24 and 36 hours respectively. The samples microstructure before and after the coating process was evaluated by REM and the chemical composition from the coating was mapped by using the EDS technician. In all evaluated samples there was a homogeny protective coating formation in all sample surface with a high content of cracks. The coating thickness hanged according to time and temperature. The smaller thickness was obtained on the temperature of 1100ºC for 12 hours and the higher thickness was obtained at 1200ºC per 36 hours. The coated samples that used 1100ºC per 12 hours and 1200ºC per 36 hours were oxidized at 1200ºC per 62 hours. The samples disintegrated after the isothermal oxidation test showing that even though the coatings presented homogeny coatings, there was not a promotion of the high temperature oxidation resistance increase from the Nb-Si-B alloy because tee high concentration of cracks on the surface, that exposed the based material to the oxidizing atmosphere.

9
  • DEIVYSON AUGUSTO PEREIRA
  • DEPLOYMENT AND CONSTRUCTION OF AN INDUCTIVE HEATING SYSTEM FOR LOW CYCLE ISOTHERMAL FATIGUE TESTS

  • Leader : RENY ANGELA RENZETTI
  • MEMBRES DE LA BANQUE :
  • ANDRE LUIS RIQUEIRA BRANDAO
  • EDUARDO MIGUEL DA SILVA
  • RENY ANGELA RENZETTI
  • Data: 22 nov. 2019


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  • The mechanical tests are widely used to determine the strength of materials. In addition to static stresses, many components are cyclically stressed, leading the material likely to fail due to fatigue. Machine components, although required in the elastic regime, may present plastic stresses at stress concentrating points. The approach to fatigue that focuses on plastic deformations is low-cycle fatigue, also known as strain-controlled fatigue. In addition to cyclic stresses, components such as gear shafts, cylinder heads and engine blocks can be subjected to temperature. Combining fatigue with temperature can result in so-called isothermal fatigue.
    In the present work a low cost inductive heating system with temperature control was developed, assembled, and adapted to a universal testing machine, allowing the study of mechanical properties of traction and low cycle isothermal fatigue. For the study, mechanical alloy steel ABNT 1045 and ABNT 4140 and cast iron FC250 and FC300 were used, materials widely used in the fabrication of fatigue requested parts. Both alloys were tested at room temperature 25ºC and 250ºC, in tensile and fatigue tests, in the latter with deformation percentages ranging from 0.2% to 1%. The tensile tests showed a decrease of the tensile strength with the increase of the temperature for the steels and cast irons. The results of the fatigue tests showed the influence of the deformation percentage, temperature and surface finish on the resistance. Increasing the deformation percentage for all materials led to a decrease in the number of cycles to fail. ABNT 1045 steel showed cyclic hardening for all deformation percentages at 250ºC, while ABNT 4140 mild cyclic softening at room temperature and 250ºC. The cast irons showed cyclic stability. The results obtained by the equipment adapted for the tests are compatible with those found in the literature, demonstrating the reliability of the developed system.

Thèses
1
  • ALEXANDRE COSTA LANZA
  • SYNTHESIS, PROCESSING AND CHARACTERIZATION OF LEAD TITANATE-ZIRCONATE THERMANELEC CERAMICS

  • Leader : DANIEL THOMAZINI
  • MEMBRES DE LA BANQUE :
  • ADHIMAR FLAVIO OLIVEIRA
  • ADRIANA SCOTON ANTONIO CHINELATTO
  • MANUEL HENRIQUE LENTE
  • MARIA VIRGINIA GELFUSO
  • SÉRGIO FRANCISCO DOS SANTOS
  • Data: 9 mai 2019


  • Afficher le Résumé
  • The demand for renewable energy sources, such as thermoelectricity, has been intensifying lately due to global warming. PZT may, under certain conditions, have semiconductor characteristics, as well as a large difference between the masses of Pb2+ cation and O2- anion in their structure, which in turn influence the characteristics of thermoelectric materials. In this work, Solid State Reaction (SSR) was synthesized PZT (called “pure”) powder and PZT powders with Mn2+, La3+, Fe3+ and Nb5+ ions, each ion in concentrations of 1%, 4%. and 7% in mol, which were shaped into pellets, and then sintered in conventional oven (cS) and microwave oven (ìS), to evaluate the effect of doping, doping concentration and type of sintering in the thermoelectric efficiency of the produced PZT ceramics. Dilatometry measurements were made to determine the sintering temperatures for pure PZT and PZT at each doping and concentration. Differential Thermal Analysis (DTA) and Gravimetric Thermal Analysis (GTA) determined the temperature calcination. Structural characterizations were performed by X-Ray Diffraction (XRD) in the synthesized powders and microstructural characterizations were done by Scanning Electron Microscopy (SEM) aided by Energy Dispersion X-Ray Spectrometry (EDS) in ceramics. For all ceramics, electrical conductivity (s), thermal conductivity (K), and Seebeck coefficient (a) measurements were made, from room temperature to 600 oC, to calculate the Power Factor (PF) and, mainly, for the calculation of the Figure of Merit (ZT). The ZT value for PZT ceramics doped with La3+ and Nb5+ ions were lower at all temperatures and concentrations when compared to pure PZT ceramics. The ZT value for Fe3+ ion-doped PZT at all temperatures and concentrations was higher than the ZT for pure PZT. Mn2- doped PZT ceramics, their ZT values are close to pure PZT at all temperatures and concentrations. The highest ZT value was for 4% mol Fe3+ doped PZT ceramic, presenting a value of 0.018 at 600 oC. It was observed that the sintering methods did not influence the thermoelectric properties of ceramics, either in relation to PZT with the doping ions Mn2+, La3+, Fe3+ and Nb5+, or in relation to their molar concentrations.

2
  • ALEXANDRO DA SILVA NUNES
  • Polyglycerol dendrimer loaded with boron-curcumin complex combining anti-angiogenesis and BNCT with potential for cancer treatment.

  • Leader : ALVARO ANTONIO ALENCAR QUEIROZ
  • MEMBRES DE LA BANQUE :
  • ADHIMAR FLAVIO OLIVEIRA
  • ALVARO ANTONIO ALENCAR QUEIROZ
  • KARINA ARRUDA ALMEIDA
  • MARIA FERNANDA XAVIER PINTO MEDEIROS
  • NIRTON CRISTI SILVA VIEIRA
  • Data: 3 juil. 2019


  • Afficher le Résumé
  • In recent years, the use of therapeutic nanoparticles in cancer medicine has become important in order to obtain the specific distribution of chemotherapeutic agents, allowing the formulation of their own formulations. In this thesis the nanoparticles were prepared for application in boron neutron capture therapy (BNCT) and anti-angiogenesis therapy. Polyglycerol dendrimer (PGLD) was used as a nanoplatform in this work because of its numerous advantages such as low toxicity and ease of functionalization. In this thesis the synthesis and characterization of nanoparticles based on PGLD for the treatment of head and neck cancer were performed. The polyglycerol dendrimer was conjugated to the boro-curcumin complex (PGLDBC). Then it was characterized by NMR (1H, 13C), FTIR and thermogravimetric analysis (TGA). The nanoparticles obtained were incubated under in vitro conditions with tumor cells of the SCC25 and SCC9 lines and their anticancer properties were evaluated by the TUNEL technique with LC50 of 15,44 mg/mL and 4,74 mg/mL. Confirming the potential of PGLDBC for the treatment of head and neck cancer.

3
  • SARA RAQUEL GOMES DE SOUSA
  • Magneto reologia: caracterização de fluidos e géis.

  • Leader : ANTONIO JOSE FARIA BOMBARD
  • MEMBRES DE LA BANQUE :
  • ADHIMAR FLAVIO OLIVEIRA
  • ANTONIO CARLOS ANCELOTTI JUNIOR
  • ANTONIO JOSE FARIA BOMBARD
  • FRANCISCO JOSE PROFITO
  • MARIA FERNANDA XAVIER PINTO MEDEIROS
  • Data: 3 juil. 2019


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  • Magneto-rheological fluids (FMR) are composed of magnetic
    particles suspended in non-magnetic liquid media, controllable through an
    external magnetic field. To formulate a good and reliable FMR for different
    applications such as MR dampers, clutches, brakes, the FMR redispersibility is a
    challenge, it is a necessary property for off-the-lab and real-world applications.
    Analogous to magneto-rheological fluids MRGs are an alternative to FMRs, but
    they still need to be further studied for their preparation. The main objective of
    this thesis is to study the behavior of magneto-rheological fluids and gels in
    physico-chemical behavior, stability, relative rheological magnetic effect,
    redispersibility, and tribology

4
  • DEBORA FERREIRA LAURITO FRIEND
  • Development of antimicrobial membranes from potato peel cellulose extraction and purification.

  • Leader : MARIA ELENA LEYVA GONZALEZ
  • MEMBRES DE LA BANQUE :
  • ALVARO ANTONIO ALENCAR QUEIROZ
  • ANTONIO JOSE FARIA BOMBARD
  • CHARLENE APARECIDA RIBEIRO
  • DANIELA SACHS
  • MARIA ELENA LEYVA GONZALEZ
  • MARIA FERNANDA XAVIER PINTO MEDEIROS
  • Data: 4 juil. 2019


  • Afficher le Résumé
  • Agroindustrial waste stands out as an abundant and low cost material that can be transformed
    into value-added products in the medical sector. Researching materials that are even cheaper
    and more sustainable has become an important task, since wound treatment is a public health
    problem. Thus, this study aims to develop an innovative “green” technology by isolating
    cellulose from potato peels to prepare antimicrobial membranes through the use of silver
    nanoparticle (Np-Ag) biosynthesis, using the geranium leaves extract (Pelargonium zonale).
    The process for extracting and purifying the potato peel cellulose, with consequent film
    formation, was done using sodium hydroxide (NaOH) and hydrogen peroxide (H2O2), using
    factorial design 22
    in the alkaline pulping stage. Results showed that both concentration and
    temperature influenced in the yield; however, only temperature was significant enough to form
    films (membrane). Among the tests a film was obtained. The highest yield occurred under the
    conditions of 0.5 mol/L NaOH, at 80°C for 2.5h, followed by bleaching with H2O2 15% w/w.
    FTIR analysis of this material exhibited characteristic bands of cellulose, while bands related
    to hemicellulose and lignin were not observed. XRD spectra confirmed that the extracted
    cellulose had a crystalline pattern similar to type I and II cellulose and the crystallinity index
    was 73.42%. The membrane thermal behavior revealed that about 80% of the cellulose chain
    was degraded at temperatures of 340°C and 442°C, with activation energy of 163.82 kJ/mol.
    Swelling studies showed that membrane has a high swelling content (between 200% and 300%)
    at temperatures of 10, 25 and 40°C and the diffusion process did not follow the Fick model. In
    addition, a phase transition temperature of about 40°C was found. Characterization analyzes
    (UV-visible and FTIR spectra) of the geranium extract exhibited functional chemical groups
    that are capable of reducing and stabilizing silver ions (Ag+) to Np-Ag. This reduction in an
    aqueous medium with geranium extract was confirmed by the presence of absorption bands
    typical of the surface plasmon resonance region (RPS) for Np-Ag at 370 and 470 nm. XRD
    analyses of the cellulose fiber/silver nanoparticle (FC/Np-Ag) biocomposites showed that the
    crystalline profile of the cellulose matrix was not modified, although crystallinity has decreased
    to the samples that were swollen in Ag+ solution. The mean size of the Np-Ag varied between
    20-12 nm. Microbiological assays revealed that the antimicrobial activity of Np-Ag was
    effective for both Escherichia coli bacteria and Staphylococcus aureus, with inhibition halos in
    the range of 12-17 mm. Releasing studies showed that the Np-Ag were only released at 370
    nm. Release profiles for the temperatures of 23, 30 and 37 ° C exhibited satisfactory exponential
    adjustments, following a bimodal model. The equilibrium was faster reached at 23°C, releasing
    0.0095 mg/mL of Np-Ag. Thus, it could be inferred that temperature decreasing resulted in
    greater release. It was also observed that the Np-Ag release followed a zero-order kinetic profile
    for the three temperatures studied. The release activation energy (EL) between 30°C and 37°C
    was 67.50 kJ/mol. In the same temperature range, thermodynamic parameters for enthalpy,
    entropy and free energy of Gibbs of the activated complex revealed an endothermic process,
    tending to decrease the system disorder and naturally not spontaneous. Therefore, using a lowcost agroindustrial residue, this study contributed to the synthesis and characterization of the
    FC/Np-Ag biocomposite, which due to its physic-chemical and antimicrobial characteristics,
    has great potential in wound treatment.

5
  • FERNANDO SILVA PENA
  • Photoconductivity and electrical transport properties in PbTe single quantum well samples

  • Leader : MARCELOS LIMA PERES
  • MEMBRES DE LA BANQUE :
  • ADHIMAR FLAVIO OLIVEIRA
  • DEMETRIO ARTUR WERNER SOARES
  • EDUARDO ABRAMOF
  • GUSTAVO SOARES VIEIRA
  • MARCELOS LIMA PERES
  • PAULO HENRIQUE DE OLIVEIRA RAPPL
  • SANDRA NAKAMATSU
  • Data: 26 juil. 2019


  • Afficher le Résumé
  • We investigated the photoconductivity effect in 10 and 14 nm well thickness n-type PbTe/Pb1-xEuxTe quantum wells, with x values of 0.12 and 0.1, for a temperature range of 300–10K using infrared light. Also, magnetotransport properties measurements are performed in 8, 10, 15, 20 and 30 nm well width p-type PbTe/Pb0.9Eu0.1Te quantum wells, at magnetic fields up to 33 T and temperature varying from 0.35 to 300 K, under dark and illuminated condition. For the n-type PbTe quantum wells, the measurements revealed that at high temperatures, the photoresponse has small amplitude. As temperature decreases to T~75 K, the photoconductivity amplitude increases reaching a maximum value 10 times higher than the original value before illumination. From Hall measurements performed under dark and light conditions, we show that this effect is a result of carrier concentration increase under illumination. Unexpectedly, for further reduction of temperature, the amplitude starts to decrease again. The electrical resistance profiles indicate that the transport occurs through barriers and the well that behave as two parallel channels. For temperatures below 75K, transport is more effective in the quantum well, where the signal reduction can be associated with the electron-electron scattering due to the increase in the carrier concentration that occurs under illumination. We also used the random potential model to explain the origin of the persistent effect observed in the photoconductivity curves. We compare magnetotransport measurements in p-type PbTe/Pb0.9Eu0.1Te quantum wells with different widths: 10, 15 and 20 nm, revealing clearly QHE and SdH oscillations, which evidences the two-dimension electron gas formation and the high quality of the samples. The 10 nm well width presented odd non-integer filling factors sequence (2.3; 3.4; 5.6; 6.9 and 8.8). The non-integer values may be associated to edge states, since that parallel conduction in the interface, between the barrier and well, was not enhanced or destroyed by illumination, although the carrier concentration was enhanced. Further investigations are necessary to clarify this effect and we consider the approximated integers 2; 4; 6; 7 and 9 calculated from experimental B values. For the 15 and 20 nm QW thickness, the SdHO and QHE also appear, however, it reveals an even integer filling factors sequence. The 10 nm QW thickness odd sequence originated from the first sub-band Landau level spin splitting; according to the Fermi level compared to the longitudinal and transversal resistance together with the first longitudinal sub-band spin splitting simulation. This assumption VI agrees with the FFT analysis that reveals the main frequency peak and two other ones, which may be the second harmonic spin splitting, up and down. The same FFT profile appears for the other two samples. Nevertheless, the 8 and 30 nm well width sample presented an insulator profile behavior and neither SdHO nor QHE were present. It is probably because the indium contacts do not diffuse through the PbTe layer well.

6
  • OLIVIA DE ANDRADE RAPONI
  • Study of the effects of prepreg aging on its properties and cure cycle through traditional techniques and dielectric analysis

  • Leader : ANTONIO CARLOS ANCELOTTI JUNIOR
  • MEMBRES DE LA BANQUE :
  • ALESSANDRO GUIMARÃES
  • ANTONIO CARLOS ANCELOTTI JUNIOR
  • ANTONIO JOSE FARIA BOMBARD
  • EDSON COCCHIERI BOTELHO
  • MARIA ELENA LEYVA GONZALEZ
  • MIRABEL CERQUEIRA REZENDE
  • Data: 4 oct. 2019


  • Afficher le Résumé
  • Prepreg materials are usually preferred when manufacturing advanced composites due to some advantages, like integrity during handling and a good fiber/matrix ratio in the final part. Despite that, one of the main concerns associated with the use of prepregs is the cure advancement (prepreg aging) during some of the manufacturing stages. This phenomenon consists on the progression of the matrix cure reaction due to the exposition of the prepreg to the environmental conditions of temperature and humidity during its transportation, cutting and lay-up stages. Although the curing reaction is programmed to occur at high temperatures, the exposition of the material to such environmental conditions might lead to a certain cure advancement that can impair the material’s processability and affect the final part quality. Therefore, it is recommended by prepreg manufacturers that the material is stored at a cold chamber, where the curing reaction rate is drastically reduced. Every time the material is removed from these storage conditions, the irreversible curing reaction tends to advance, and the sum of the exposition time (out-time), must be monitored in order to assure that the effects of the prepreg aging are not likely to affect the quality of the final part. In this context, the present works aims to: (1) characterize the out-time effects on the prepreg properties; (2) explore innovative characterization techniques to both monitor and estimate the prepreg out-time; (3) associate the effect of the out-time with the final composite properties. To do so, prepreg materials were aged for pre-established times (between 0 and 60 days) and their properties measured by a group of analyses, including thermal and rheological techniques. Also, laminates were manufactured from aged prepregs using an autoclave curing process and their properties were measured, focusing on both thermal and mechanical behavior. The results point out to the possibility of using dynamic mechanical analyses (DMA) as a single technique for fully characterizing the prepreg and final composite, regarding prepreg out-time effects. Also, dielectric analysis (DEA) is presented as an alternative technique for both estimating the prepreg out-time and monitoring the curing process specificities of composites manufactured from aged raw materials. Finally, the characterization of the final composite indicates the possibility of extending the out-time limits of the prepreg, allowing the use of materials formerly considered as out of specification. The combination of all the findings of the present work might contribute to the reducing of waste on prepreg processing, which is one of the major challenges in advanced composite manufacturing.

7
  • ANA CRISTINA TOLENTINO CABRAL
  • DEVELOPMENT OF ARTIFICIAL HETEROSTRUCTURES FOR APPLICATION IN MEMORIES CORRELATED BY ELECTRONS

  • Leader : FRANCISCO MOURA FILHO
  • MEMBRES DE LA BANQUE :
  • ALEXANDRE ZIRPOLI SIMOES
  • CEZAR WELTER
  • FRANCISCO MOURA FILHO
  • MARCIO DIMAS RAMOS
  • URBANO MIGUEL TAFUR TANTA
  • Data: 4 déc. 2019


  • Afficher le Résumé
  • Nonvolatile RRAMs are extremely studied due to their high data storage density. Nowadays, studies are focused on memories that have resistive switching, such as CeRAM. In this type of memory electric or magnetic fields, light or pressure can cause an electronic phase transition such as changes in electrical resistance, equivalent to a metal-insulating transition. In addition, one of its main features is the initial conductive behavior exhibited by virgin devices eliminating the need for electroforming, reducing the voltage levels required for operation, enabling low power operation and reducing the spaces for peripheral circuits. Some problems are encountered in the development of CeRAM devices such as random lamination in thin films due to high conductive state current rates and electroforming voltages. This thesis seeks to develop heterostructured thin films, format still little studied, with alternating layers of La2Ti2O7 (LTO) and Y2Ti2O7 (YTO) aiming at its evaluation for possible application as CeRAM memory. For this, a systematic study of the LTO and YTO powders, heat treated at different temperatures and atmospheres, and thin films were deposited by spin coating of precursor solution prepared by the polymeric precursor method. Powder analysis indicated the formation of monophasic, polycrystalline material with perovskite layered monoclinic structure for LTO and pyrochlore cubic structure for YTO. The optical band gap energy values were estimated between 3.70eV and 3.99eV, demonstrating that the materials studied are semiconductor. We observed the surface morphology of the thin films through AFM and it indicates the formation of well densified films from the heat treatment at 850°C and that the increase of pre-calcination temperature in heating plates tends to increase the crystallization of the films and the densification. In addition, we observed the increase of roughness and the average grain size as temperature rises, while the YTO/LTO sample heat treated in oxygen flow presented less variation in the roughness values. Thin films have dense and uniform layers with a maximum thickness of approximately 60.98nm in the YTO/LTO model and 113.98nm in the LTO/YTO model. For LTO/YTO heterostructured thin films, weak ferromagnetic behavior was observed at the analysis temperatures, and also self-polarization with effective remaining d33 of 8.11pm/V and 7.57pm/V for the crystallized films in static air atmosphere and in oxygen flow, respectively. Thus, the results suggest that the process employed in this study proved to be an efficient method for the study of heterostructured thin films for possible application as CeRAM memory devices. It is noteworthy that the polymeric precursor method is only an exploration method for the preliminary study, since processing at 850°C is not suitable for the making of memories.

8
  • PRISCILA VELOSO DA SILVA
  • Polyglycerol Microspheres Containing Dimethyl Fumarate and Curcumin for Application in Multiple Sclerosis Therapy

  • Leader : ALVARO ANTONIO ALENCAR QUEIROZ
  • MEMBRES DE LA BANQUE :
  • ADHIMAR FLAVIO OLIVEIRA
  • ALVARO ANTONIO ALENCAR QUEIROZ
  • EDSON GIULIANI RAMOS FERNANDES
  • KARINA ARRUDA ALMEIDA
  • NIRTON CRISTI SILVA VIEIRA
  • Data: 5 déc. 2019


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  • Multiple sclerosis is autoimmune and chronic disease characterized for neurons demyelinating and formation of sclerotic lesions within central nervous system. It is a disabling disease over time and whose therapies can cause several side effects. This work proposes an alternative to the treatment of multiple sclerosis from the development of carrier system using microspheres of polyglycerol dendrimer with dimethyl fumarate and curcumin. Initially, the microspheres were characterized by SEM, FTIR, TGA and DSC. The swelling degree and the activation energy of the polyglycerol dendrimer microspheres (G10, G25, G50, G100 and G200) were determined. The results of these analyzes showed that the smaller and larger porous microspheres G100 and G200, respectively, were the most suitable for the formation of the compounds. It was evaluated porosimetry of these groups and biocompatibility by in vitro cytotoxicity and hemocompatibility assays. The theoretical study of molecular anchoring showed that the formation of the compounds was spontaneous, the compound with curcumin (-23.8 kJ/mol) had higher affinity compared to the compound with dimethyl fumararte (-11.3 kJ/mol). The compounds, DMF-PGLD and CUR-PGLD, were prepared and subsequently characterized by FTIR and evaluated the release profiles. FTIR spectra suggested the interaction of the compounds due to the appearance of absorption bands characteristic of the precursor molecules in the compounds. The release study determined the super case II transport mechanism. A higher retention was observed in the compounds with curcumin, because the curves were less pronounced or with later release. In conclusion, it is suggested that the formation of compounds between polyglycerol dendrimer (G100 and G200) porous microspheres and active (dimethyl fumarate and curcumin) are an alternative for controlled release in the treatment of multiple sclerosis. However the compounds with curcumin had more favorable results to their application, due to affinity and retention.

2016
Thèses
1
  • FRANCISCO FELIPE GOMES DE SOUSA
  • Análise dos espaços de parâmetros do circuito de Chua experimental

  • Leader : RERO MARQUES RUBINGER
  • MEMBRES DE LA BANQUE :
  • RERO MARQUES RUBINGER
  • MIRIAN DE LOURDES NORONHA MOTTA MELO
  • ALAN BENDASOLI PAVAN
  • EMILSON RIBEIRO VIANA JUNIOR
  • YVO MARCELO CHIARADIA MASSELLI
  • Data: 9 mai 2016


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  • Neste trabalho, foram obtidos experimentalmente os espacos de parametros bidimensionais
    da periodicidade e do maior expoente de Lyapunov para o circuito de Chua, usando
    as medidas de series temporais para diferentes valores das resistencias rL em serie com
    o indutor e R ligada aos dois capacitores. Este circuito apresenta o comportamento de
    um material semicondutor com condutividade diferencial negativa que lembra a forma da
    letra N (NNDC) acoplado a um circuito tanque. Quatro potenci^ometros digitais com 1024
    passos de 0; 100
    , 0; 200
     e 1; 000
     foram construdos para modi car os valores destes
    par^ametros. A aquisic~ao de dados e controle dos potenciometros digitais foram feitas
    atraves de um programa desenvolvido em Labview R
     e a analise de dados e apresentacao
    dos resultados com scripts em PYTHON. Os resultados obtidos foram comparados com
    simulac~oes feitas em FORTRAN que con rmaram a presenca de cascatas de adic~ao de
    perodo, janelas periodicas, rotas de adic~ao de perodos impares, coexistencia de atratores
    e um hub de periodicidade. Con rmando a e cacia dos usos dos potenciometros digitais
    como alternativa para variar os parametros resistivos de sistemas dinamicos eletricos.

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