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1
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JAQUELINE DO CARMO LIMA CARVALHO
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PRODUCTION OF MODIFIED CeO2 WITH COBALT OBTAINED BY MICROWAVE ASSISTED HYDROTHERMAL METHOD
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Leader : FRANCISCO MOURA FILHO
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MEMBRES DE LA BANQUE :
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MIGUEL ADOLFO PONCE
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FRANCISCO MOURA FILHO
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MARCIO MARTINS LAGE JUNIOR
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Data: 17 févr. 2021
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Afficher le Résumé
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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.
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2
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FELIPE SILVA FARIA
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INFLUENCE OF THE CONTENT AND GRANULOMETRY OF POLYURETHANE WASTE ON MORTAR PRODUCTION
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Leader : MIRIAN DE LOURDES NORONHA MOTTA MELO
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MEMBRES DE LA BANQUE :
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MIRIAN DE LOURDES NORONHA MOTTA MELO
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PAULO CESAR GONCALVES
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VALQUIRIA CLARET DOS SANTOS
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VANDER ALKMIN DOS SANTOS RIBEIRO
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Data: 19 févr. 2021
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Afficher le Résumé
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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.
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3
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JOSÉ HENRIQUE RODRIGUES DA ROCHA
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Evaluation of organoclays and dispersants in the preparation of magnetorheological suspensions
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Leader : ANTONIO JOSE FARIA BOMBARD
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MEMBRES DE LA BANQUE :
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ANTONIO CARLOS ANCELOTTI JUNIOR
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ANTONIO JOSE FARIA BOMBARD
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DANIELA SACHS
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MARCOS AKIRA D AVILA
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Data: 3 mai 2021
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Afficher le Résumé
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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.
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4
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FILIPE BUENO VILELA
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Development of a printed polymeric mesh with a coupled non-invasive electro-stimulation device for the treatment of bone fractures
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Leader : DANIELA SACHS
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MEMBRES DE LA BANQUE :
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SAMIRA ESTEVES AFONSO CAMARGO
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ANTONIO CARLOS ANCELOTTI JUNIOR
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DANIELA SACHS
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PATRÍCIA CAPELLATO
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Data: 29 juil. 2021
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Afficher le Résumé
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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.
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5
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PEDRO HENRIQUE GONÇALVES
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Study of the Reuse of Vanadis®8 Superclean Steel through the Powder Metallurgy Route using the High Energy Milling technique (Mechanical Milling).
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Leader : GILBERT SILVA
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MEMBRES DE LA BANQUE :
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ANTONIO AUGUSTO ARAUJO PINTO DA SILVA
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EDMILSON OTONI CORREA
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GILBERT SILVA
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KATIA REGINA CARDOSO
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Data: 3 août 2021
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Afficher le Résumé
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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.
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6
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LUCAS VICTOR BENJAMIM VASCONCELOS FRÉ
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TiO2 NANOTUBES LOADED WITH PYRAZOLE-TETRAZOLIC HYBRIDS: A POTENTIAL SYSTEM AGAINST BACTERIAL INFECTION
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Leader : DANIELA SACHS
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MEMBRES DE LA BANQUE :
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GILBERT SILVA
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PATRÍCIA CAPELLATO
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SAMIRA ESTEVES AFONSO CAMARGO
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Data: 7 déc. 2021
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Afficher le Résumé
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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.
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7
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RENATO SERGIO MELLO DA SILVA
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Effect of Iron Content on the Microstructure and Mechanical Properties of Al-Si-Cu-Mg Alloys Varying the Cooling Rate
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Leader : MIRIAN DE LOURDES NORONHA MOTTA MELO
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MEMBRES DE LA BANQUE :
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DANIELA SACHS
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MIRIAN DE LOURDES NORONHA MOTTA MELO
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NEIDE APARECIDA MARIANO
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PAULO JUNHO DE OLIVEIRA
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Data: 17 déc. 2021
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Afficher le Résumé
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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.
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RAPHAEL FELCA GLORIA
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STUDY OF COATING PROCESS OF THE SUPERALLOY Mar-M246 USING THE HALIDE ACTIVATED PACK CEMENTATION (HAPC) METHOD
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Leader : GEOVANI RODRIGUES
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MEMBRES DE LA BANQUE :
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ANTONIO AUGUSTO ARAUJO PINTO DA SILVA
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CARLOS ANGELO NUNES
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GEOVANI RODRIGUES
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GILBERTO CARVALHO COELHO
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NABIL CHAIA
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RENATA NEVES PENHA
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Data: 25 févr. 2021
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Afficher le Résumé
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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.
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2
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DEMARCUS WERDINE
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Statistical analysis of the properties of self-compacting concrete mixed with tire rubber waste.
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Leader : MIRIAN DE LOURDES NORONHA MOTTA MELO
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MEMBRES DE LA BANQUE :
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GUILHERME FERREIRA GOMES
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MIRIAN DE LOURDES NORONHA MOTTA MELO
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PAULO CESAR GONCALVES
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ROSA CRISTINA CECCHE LINTZ
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VALQUIRIA CLARET DOS SANTOS
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VANDER ALKMIN DOS SANTOS RIBEIRO
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Data: 27 juil. 2021
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Afficher le Résumé
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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.
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3
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LUIZ HENRIQUE RIBEIRO
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Electronic transport of InAs/GaAs samples
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Leader : RERO MARQUES RUBINGER
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MEMBRES DE LA BANQUE :
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ADHIMAR FLAVIO OLIVEIRA
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ALAN BENDASOLI PAVAN
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MARCIA REGINA BALDISSERA RODRIGUES
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RERO MARQUES RUBINGER
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VANDER ALKMIN DOS SANTOS RIBEIRO
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YVO MARCELO CHIARADIA MASSELLI
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Data: 3 sept. 2021
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Afficher le Résumé
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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.
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4
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MARIA AUXILIADORA DE BARROS MARTINS
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Rheological properties and durability of high-strength self-compacting concrete with marble and granite cutting waste and foundry exhaust sand
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Leader : MIRIAN DE LOURDES NORONHA MOTTA MELO
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MEMBRES DE LA BANQUE :
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LUISA ANDREIA GACHET BARBOSA
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MIRIAN DE LOURDES NORONHA MOTTA MELO
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PAULO CESAR GONCALVES
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REGINA MAMBELI BARROS
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ROSA CRISTINA CECCHE LINTZ
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VALQUIRIA CLARET DOS SANTOS
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Data: 21 oct. 2021
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Afficher le Résumé
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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.
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5
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ALEXANDRE FLAUZINO JUNIOR
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Chitosan lactate and NPsAg nanocomposites with antimicrobial activity
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Leader : MARIA ELENA LEYVA GONZALEZ
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MEMBRES DE LA BANQUE :
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GUILHERME MARIZ DE OLIVEIRA BARRA
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ALVARO ANTONIO ALENCAR QUEIROZ
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BLUMA GUENTHER SOARES
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FABIO DA SILVA LISBOA
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MARIA ELENA LEYVA GONZALEZ
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MARIA FERNANDA XAVIER PINTO MEDEIROS
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Data: 25 oct. 2021
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Afficher le Résumé
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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.
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6
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NÁDIA ALVES NERY BALBINO
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Comparative Study of the Corrosion Resistance of WC-NiMo, WC-NiCr and WC-Co Cemented Carbides
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Leader : EDMILSON OTONI CORREA
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MEMBRES DE LA BANQUE :
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CARLOS ALBERTO CARVALHO CASTRO
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EDMILSON OTONI CORREA
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GEOVANI RODRIGUES
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GLAUCO JOSE RODRIGUES DE AZEVEDO
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JEAN CARLO CESCON PEREIRA
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SERGIO SOUTO MAIOR TAVARES
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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.
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7
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MATHEUS JOSE DA SILVA
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Study of Electrical Transport Properties in ZnO/CdO-based heterostructures
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Leader : DEMETRIO ARTUR WERNER SOARES
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MEMBRES DE LA BANQUE :
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ADHIMAR FLAVIO OLIVEIRA
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DEMETRIO ARTUR WERNER SOARES
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MARCELOS LIMA PERES
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MÁRCIO PERON FRANCO DE GODOY
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SANDRA NAKAMATSU
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WAGNER SOUZA MACHADO
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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.
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8
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GILZA CARLA RIBEIRO
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Development of PVDF/BaTiO3 and P(VDF-TrFE)/BaTiO3 Composite Membranes with Piezoelectric and Antimicrobial Properties for Biomedical Applications
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Leader : DANIELA SACHS
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MEMBRES DE LA BANQUE :
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RAQUEL MARIA LIMA LEMES
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AMANDA DE CARVALHO PEREIRA MORAES
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DANIELA SACHS
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MARIA ELENA LEYVA GONZALEZ
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PATRÍCIA CAPELLATO
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ROSSANO GIMENES
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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.
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9
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ISABELA CRISTINA FERNANDES VAZ
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CERIA-BASED GAS SENSOR MODIFIED WITH Nd PREPARED BY HYDROTHERMAL ASSISTED BY MICROWAVE FOR DETECTION OF CARBON MONOXIDE
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Leader : FRANCISCO MOURA FILHO
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MEMBRES DE LA BANQUE :
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EDUARDO ANTONELLI
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FRANCISCO MOURA FILHO
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MARCIO MARTINS LAGE JUNIOR
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RERO MARQUES RUBINGER
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RODOLFO FOSTER KLEIN GUNNEWIEK
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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.
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