The automotive industry is in constant search for advanced environmentally friendly materials that can improve safety and reduce the risk of fire in vehicles, as well as low CO₂ emissions. In this context, this work aims to develop, apply and evaluate the flame retardant properties of a nanocomposite of reduced graphene oxide (RGO)/polyurethane (PUR)/cotton, using a factorial design 2³. The independent variables analyzed in the process were mass of reduced graphene oxide (RGO), temperature and infrared polymerization time. The samples were characterized in terms of contact angle measurements, adhesion work, air/water permeability, as well as tensile and abrasion resistance. Microstructural analyzes of both RGO and nanocomposites were also carried out via XRD, FTIR, Raman spectroscopy, HRTEM-SAED, SEM-FEG. The results showed that the synthesis of GO and its subsequent reduction obtained RGO with 2-4 sheets with a thickness below 5 nm each and a D/G band ratio greater than 1.05. Its application as a reinforcing agent in the PUR/cotton system was responsible for increasing the hydrophobicity of the nanocomposite, greater anti-fire power, greater thermal resistance, high durability in terms of abrasion in different wear cycles. Thus, this study proves that the polymerization temperature and mass of RGO are the most important variables in the production process of nanocomposites and that RGO is an emerging 2D material in obtaining flame retardant nanomaterials with potential application in the automotive industry.

One of the techniques to quantify the toughness of metallic samples is the Charpy method. However, the application of pendulum scratching test analyses to obtain properties such as toughness and dynamic hardness can be promising, due to its fast execution and low cost. Thus, the objective is to seek for a correlation between the two techniques in the characterization of the toughness of metallic materials. A comparison will be made between the Charpy method and the pendulum hammer method, including the characterization of metallic samples in both equipment and the analysis of the energy balance. By comparing the results, one can look for a strong correlation between both measured properties. So, the pendulum scratching test is expected to provide results that show a strong correlation with the results of Charpy tests performed on the chosen metallic materials. Such a correlation between significantly different properties encourages further studies that may not only explain the mechanisms involved, but also expand knowledge about the mechanical properties of materials.

Mo-Cu composite is used in electronic packaging devices, electrical contacts and heat skins. The union of the high electrical and termal conductivity properties of copper with the wear resistance of molbdenum, arouses strong interest in the electrical and electronics industry. The densification of these Mo-Cu composites via sintering is hampered due to the mutual insolubility of Mo and Cu and the low wettability of Cu to Mo. However, powder metallugy is a viable route to manufacture this composite. In this work, the influence of mechanical mixing (MM) and high energy milling (HEM) techniques, as well as the Chemical method of coprecipitation of heptamolybdate (AHM) and copper nitrate (CuN) powders on densification, microstructure and properties of Mo-20%wt.Cu and Mo-25%wt.Cu powder compacts were investigated. AHMA-CuN powders with 10.8 and 13.9 % by masso f CuN were prepared, respectively, by mechanical (MM and MAE) and chemical coprecipitation methods. The prepared powders were reduced in 750 °C in tubular furnace under H₂ atmosphere and a flow of 316 mL/min. The composite Mo-Cu powders with 20 and 25 % by mass of Cu obtained were compacted at 250 MPa and the green compacts produced were sintered at 1.150 °C for 1 h under na atmosphere of H_2. The sintered bodies of Mo-Cu powders prepared by coprecipitation and HEM reached a relative density of 96 ± 2.7%, while those prepared by MM reached Only 75 %. Said sintered compacts reached, respectively, a microhardness of 190.7 ± 15,4, 293.3 ± 13,4 and 183.2 ± 18,6 HV, as well as na electrical conductivity of respectively 34, 22 and 15 IACS. The greater homogenization and smaller size of the phases produced by the processes of preparation of Mo-Cu powders by coprecipitation and HEM are responsible for obtaining the highest values of the properties of density, microhardness and electrical conductivity of the sintered Mo-Cu compacts.

The use of solid lubricating films makes it a great option for controlling wear and friction under certain operating conditions, in addition to not attack the environment. Thus, this work aims to carry out a study on plasma deposition with cathodic cage of MoS2 thin films on AISI 1020 steel substrates. From an adaptation of the cathode cage named cathode cylinders, the samples were treated in cathodic and floating potential with temperatures of 300 °C, 350 °C and 400 °C, all with an atmosphere rich in argon, as a way of studying its deposition in the two potential configurations. After the treatments, they were subjected to chemical analysis by X-ray diffraction (XRD) and Raman spectroscopy, in addition to a calotest tribological test. It was possible to quantify the coating thickness using scanning electron microscopy (SEM). In general, the results indicated success in the deposition of molybdenum disulfide in all samples treated in floating potential, and in the formation of sulfide compounds in cathode potential, as it was possible to visualize in the XRD. It was also possible to qualify the film by observing the vibration bands after deconvolution of Raman spectroscopy, since it indicated the presence of peaks referring to MoS2 and its compounds. Finally, there was a significant reduction in wear through the calotest.

The search for new sources of renewable energy is a global concern for increasingly sustainable development. Among renewable energy sources, hydrogen (H2) is seen as an alternative to the use of fossil fuels due to its minimal environmental impact. This study aimed to obtain nickel (Ni) and tungsten carbide (WC) catalysts supported on alumina (Al2O3) and MCM-41 for hydrogen production via methane dry reforming (CH4). Various transition metals such as Co, Pd, Pt, Ru, Rh, Ir, and Ni can be used in the reforming reaction. Tungsten carbide behaves similarly to Pt in several catalytic reactions, owing to the modification of tungsten's electronic structure by the addition of carbon. In this context, we were able to synthesize catalysts of (Ni10%wt) and (WC10%wt) supported on Al2O3 via incipient wetness impregnation with distilled water, and catalysts of (Ni10%wt), (WC10%wt), (Ni2%wt-WC8%wt), (Ni5%wtWC5%wt), and (Ni8%wt-WC2%wt) supported on MCM-41 via incipient wetness impregnation with ethanol. The (WC) used in the study was produced by carbothermic reduction of ammonium paratungstate (APT). The obtained material was then characterized by X-ray diffraction (XRD), X-ray fluorescence, Raman spectroscopy, nitrogen adsorption and desorption using the BET method, and scanning electron microscopy (SEM). Based on the results, it was possible to conclude that the WC synthesis process was efficient, producing nanometric carbides (15.5 nm) with irregular particle shapes and sizes. Incipient wetness impregnation proved to be an effective method for all obtained catalysts, with the nickel phase showing better dispersion on the alumina and MCM-41 supports than the WC phase. However, when both active phases (WC-Ni) are present, the dispersion on the supports significantly improves for the WC active phase. The (Ni10%wt/Al2O3) catalyst presented a specific surface area of 3.60 m²/g, while the (WC10%wt/Al2O3) catalyst had a specific surface area of 2.2 m²/g. The Ni10%wt/MCM-41 catalyst had a specific surface area of 588.56 m²/g, whereas the WC10%wt/MCM-41 catalyst showed a surface area of 870.63 m²/g, significantly increasing compared to the nickel active phase (Ni10%wt/MCM-41).

The environmental problems caused by fossil fuels aren’t a new thing. In the search for alternatives to diesel, biodiesel from algae shows itself as a great alternative because of the capture of CO₂ practiced by the algae during their production, their rapid reproduction, among others. The present work aims to make an exergetic, exergoeconomic and exergoenvironmental analyses of the production of biodiesel from algae. For this, mass, energy, exergy, exergoeconomic and exergoenvironmental balances are made, in these last the specific costing methodology (SPECO) was used, specific costs, exergoeconomic factor, exergy destruction and exergetic efficiency were also calculated. With these parameters, it is possible to detect the equipment that has the worst performance and suggest changes in order to make the system as a whole more efficient. The equipment that had the worst exergetic performance was the photobioreactor, presenting lower exergetic efficiency (10.73%) and being responsible for (99.33%) of all exergy destroyed in the production of algae biodiesel. Algae biodiesel is shown to be a great alternative to diesel and more studies in order to optimize its production should be done with the objective of making it more economically viable and improving its exergetic performance.

Two phosphorus-based Ionic Liquids (IL) were deposited onto a <111> silicon substrate via dip coating. These ILs, trihexylttetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate and tetrabutylphosphonium methanesulfonate, are two possible candidates for the lubrication of micro/nanoelectromechanical devices (MEMS/NEMS). To evaluate this, their abilities to form a thin adsorbed film (1 to 100nm) on the silicon surface were studied. Variations were made in deposition parameters such as substrate cleanliness, different concentrations and deposition speed. The surface was followed by optical microscopy, with the aid of the atomic force microscope (AFM). As a result, it was possible to observe the topography, the variation of the friction force as a function of the applied normal load and the adhesion force between the tip and the film. In addition, a confocal Raman spectroscopy (532 nm laser and 7.2 mW power) was used to observe the presence of ionic liquid in specific regions of interest. Using these tools, it was possible to observe a different behavior in the friction coefficient and in the film formation mechanism on the surface between the two lubricants, which can be attributed to the fact of difference in the size of the cation chain and consequently in its adhesion force.

Advanced High Strength Steels (AHSS) have been used for vehicular structures aiming for mass reduction with a feasible balance between mechanical resistance and formability in manufacturing processes. Those steels are commonly supplied in thin sheets and must be manufactured typically by forming processes to define the product shape, and punching is one of the critical operations. The AHSS Ferrite-Bainite (FB) stands out for having high local formability, allowing structural reinforcements like flanges to be obtained. Furthermore, processing AHSS involves high strength and plastic elongation values, and the material’s behavior changes during the operation due to processing parameters such as die clearance, punch geometry, and temperature. Models to evaluate the effects of operations above room temperature are available in the literature, but there is a lack of studies at cryogenic temperatures. This research aims to simulate the behavior of the AHSS FB590 material at room and cryogenic temperatures to analyze the ductile-brittle transition effects at the cutting edge. A methodology to obtain values of triaxiality and plastic strain needed for calibration of the constitutive models was developed using digital image correlation (DIC) to determine the fracture moment. The hole expansion simulations showed that an increment of 4.7 mm on the final diameter can be obtained by changing the previous punching operation from room to cryogenic temperature.

WC-Cu composites are used as electrical contacts in high power circuit breakers and electrical resistance welding electrodes. This is due to the high thermal and electrical conductivity and excellent workability of copper associated with the high resistance to wear and erosion by electric arc of tungsten carbide. However, the low wettability of liquid copper on tungsten carbide particles and the mutual insolubility of the constituents make it difficult to densify this composite. This work investigates the effect of adding 5 and 10% by mass of Nb to the WC-20%Cu composite and the influence of the powder preparation technique on the microstructure, densification and properties of WC-Cu-Nb composites sintered in liquid phase. The powders were characterized by SEM, EDS, FRX and DRX, while the compact sintered WC-Cu-Nb powders were characterized by SEM, EDS and measurements of density, Brinell hardness and electrical conductivity. The crystallite size of the WC-20%Cu-5%Nb composite powders ground for 5 h in an attritor mill reached 11.0, 11.2 and 26.9 nm for the respective WC, Cu and Nb phases. In contrast, the crystallite size of the same composite powders milled for 10 h in a planetary mill reached only 15.0 and 16.3 nm for the respective WC and Cu phases, but the Nb phase amorphizes or goes into solid solution in Cu. Although the attrition mill produced a greater reduction of crystallites and greater dispersion of the hard WC phase in the soft Cu and Nb phases, contamination by Fe, from the grinding body and chromed steel container, promoted less densification of the powder compacts of the composite. WC-20%Cu-5%Nb, as the compacts of these composite powders ground for 5 h in an attritor mill reached a density of only 71.39 ± 3.38% of the theoretical density, while the compacts of the same composite powders ground for 10 h in a planetary mill, also with chrome steel grinding bodies, reached a density of 81.43 ± 2.7% of the theoretical density. On the contrary, when grinding was carried out in a planetary mill with carbide grinding media, no contamination was detected and the density reached 93.25 ± 3.16%. The addition of Nb contributes to the densification of the WC-Cu composites, as the powder compacts of the WC-20%Cu composite with zero, 5 and 10% by mass of Nb prepared in a planetary mill reached a density, respectively, 77.62 ± 1, 0.65%, 81.43 ±2.70%, 84.34 ± 1.37% of theoretical density when sintered at 1150 °C for 1 hour. Furthermore, the microstructure of the sintered compacts of WC-20%Cu powders with a higher amount of Nb exhibit smaller grain size, confirming their efficiency in inhibiting the grain growth of the sintered composites. Brinell hardness increases with milling time reaching values of 101 HB and decreases with decreasing WC mass. The electrical conductivity increases with the addition by mass of Nb, reaching 2.27% IACS when the amount of 10% by mass of Nb is added to the WC-20%Cu composite.

Many new techniques are being developed to obtain results similar to conventional and normative tests, with an increase in favor of the reduction of experiment time, cost reduction and ease of obtaining specimens. This work aims to design, develop and validate a pendular rebound hammer, capable of enabling the study of the behavior of scratch energy in metallic materials. Therefore, the necessary adaptations, the assembly of circuits and electronic components, the elaboration and dimensioning of the specimen, such as movements of components, and electronic components, are eliminated as steps related to the development of the equipment's fuselage. In the preliminary phase of the project, the existing fuselage, the pendulum, the main axle and a system were considered, for subsequent adaptations and internal construction. Then, the design and execution of a new system was carried out, which allows the movement of samples in three, the recovery of the sample to carry out the tests and the electronic control of the vertical displacement of the sample. Regarding the development of the pendulum measurement system, first a mechanism was developed to determine the depth of scratch of the penetrator in the sample, then the pendulum release mechanism through a magnetic triggler, then the pendulum angulation and height calculations in movement, and finally the scratch energy was calculated. To ensure that the sample was not scratched at an inappropriate time, a servo motor was placed to remove the sample holder from the risk region. This done, the electronic connections associated with each component were made, and a data processing center was also built, using an Arduino AtMega2560 and a LCD. The developed equipment was submitted to validation tests, where its perfect functioning is verified. The enhanced version allows for quick test execution, the use of easily fabricated specimens, the performance of multiple scratch tests with the same specimen, the vertical, lateral and horizontal displacement of the sample, the control of scratch depth, and the calculation of scratch energy, being displayed on the LCD screen.

316L stainless steel has been widely used as a metallic biomaterial for orthopedic and dental implants due to its excellent mechanical properties and low cost. However, one of the main limitations to its clinical use is the susceptibility to localized corrosion in physiological environments that can result in inflammation, pain and, in the worst case, implant failure. To increase its biocompatibility, the metal can be coated with hydroxyapatite which has a chemical composition similar to the inorganic matrix of bone. The objective of this study is to improve the corrosion behavior, biocompatibility of the metallic implant and osseointegration. Stainless steel 316L was used as a metallic substrate for the deposition of the hydroxyapatite coating performed by the electroplating technique called Plasma Electrolytic Oxidation (PEO), which has the advantages of simplicity, low cost and thermal and chemical stability. The samples were immersed in an electrolyte solution containing calcium acetate, beta glycerol phosphate and nitric acid. Then, a potential difference was applied using two configurations: cathodic reaction during times of 90 and 180 seconds and anodic reaction during times of 15 and 20 seconds. The crystalline phase composition of the coating was analyzed by X-ray diffraction (XRD). The topography of the deposited films and their layer thickness were analyzed by Scanning Electron Microscopy (SEM). Furthermore, the corrosion properties of the treated and untreated surfaces were evaluated by potentiodynamic polarization tests using an electrochemical corrosion cell with an electrolyte containing 3% sodium chloride (NaCl) by weight. The results obtained showed that the bioactive hydroxyapatite coatings were successfully deposited on the substrate surface and presented a relevant and uniform thickness, constituted by a stable chemical composition. The increase in polarization resistance indicates that the coatings are electrochemically stable and show better corrosion resistance. In this way, the methodology employed provides a practical and objective way to modify the surface of 316L stainless steel and obtain a better biocompatibility of the metal for medical applications.8 .

The reduction of vehicles mass, without a significant impact on their resistance or users’ safety, is a decisive factor for the viability of less-polluting vehicles and mitigation of environmental effects. The application of increasingly thinner steel sheets in the automotive structure has been one of the ways to achieve this objective. In this sense, Ultra Low Carbon (ULC) steels and Advanced High Strength Steels (AHSS) have been widely applied in manufacturing automotive bodies' structural parts. In particular, AHSS combines a ferritic matrix with high ductility; and a second high-hardness constituent (which can be martensite, bainite, or a combination of both) dispersed in the matrix. This microstructural characteristic allows the processing of AHSS by forming and stamping. However, defects such as cracks, nucleated from the cut edges, can occur due to the presence of this second constituent. An alternative to minimize crack nucleation is to carry out the stamping process at cryogenic temperatures. The hypothesis is that if the process is carried out at low temperatures, there will be a change in the plastic deformation mechanism from shear to deformation by mechanical twinning and cleavage. Therefore, this research aims to design, manufacture and test an experimental bench adapted to a shaper machine to evaluate cryogenic punching in two steel sheets applied for automotive structures. Tests were carried out with Ultra Low Carbon (IF) and AHSS (DP780) steels, with a thickness of 0.65 mm, and results showed the process feasibility at cryogenic temperatures. The most significant changes were the reduction of plastic deformation regions and the increase of the fracture zone in the samples processed at temperature below -150 °C when compared with those tested at room temperature.

Leaks through the cement sheath have been a persistent and chronic problem in the oil industry for decades. Thus, several additives are used to strengthen the cement matrix and cause better adaptation of the slurry to the well scenario. Drying shrinkage caused by water loss and gel consolidation is a serious disadvantage of Portland cement. This shrinkage is capable of creating microcracks when the stresses are greater than the tensile strength of the cement, which significantly increases the permeability of this material. Magnesium Oxide (MgO) is an additive capable of reducing drying shrinkage through an isomorphic substitution between calcium and magnesium in the cement structure. SBR Latex is a widely used additive to prevent gas migration as it reduces fluid loss, increases acid resistance and improves the microstructural bonds of cement. Based on this, this work evaluates the influence of MgO and SBR latex additives using experimental design. The results reaffirm the effects of MgO and SBR Latex in reducing scenarios favorable to leaks. They show the strong influence of MgO in reducing drying shrinkage and gel formation. They indicate that MgO has low influence on Compressive strength in the early stages of curing but has an important influence throughout curing and also has a strong influence on the Shear Strength of the slurry. They show that SBR Latex is an additive capable of reducing the Compressive Strength by increasing the elasticity of the slurry and that it has little practical influence on the shear stresses. From the results obtained, it is possible to determine better conditions for the formulation of slurries that use MgO and/or Latex SBR applicable in oil well cementing operations.

In this work it was proposed to produce plasma surface treated silicone surfaces that can promote the reduction of drag and improve the wear reduction of customized silicone devices that need drag reduction, in addition to analyzing the mechanical properties of the surfaces produced. Superhydrophobic surfaces (SSH) have high water repellency and have been studied as an alternative mechanism to reduce drag. The alterations promoted on the surface of Sylgard® due to the deposition of substances such as: acetylene, argon and oxygen, through the plasma treatment has presented the phenomenon of drag reduction on cylindrical surfaces proposed in predefined diameters and lengths. The drag reduction (RA) for the flexible tubes was evaluated on a rheometer bench, in the rotations per minute variations of 50 rpm, 100 rpm, 250 rpm before and after plasma deposition. The surface, morphological and chemical changes were confirmed by Scanning Electron Microscopy (SEM), Fourrier Transform Infrared (AFTIR), Atomic Force Microscopy (MFA) analyzes on flat plates, waiting for the impression of a rough structure at the nanometer scale with deposition of chemical elements from the polymerizing solution through the plasma. The treated samples showed less resistance to water flow, tested through the imposition of torque on the tubes. The argon samples showed the best drag reductions even under laminar flow.

The use of waste from industrial processes has been growing substantially motivated by the environmental concern arising from the storage of these products and their consequences for human health and the planet. The residue of cast iron, produced by machining processes, is among the types of materials potentially harmful to human health, and consequently among those that cause environmental concern. The composite of polyester resin matrix and cast iron residue powder was be obtained and studied. The four composite configurations were defined as a function of the maximum residue load experienced in the process of obtaining the proposed composite. The configurations 0RPF, 50RPF, 100RPF and 150RPF were tested. The amounts of RPF were relative to those of the polyester matrix resin. All the formulations tested presented viability of processing. Test specimens were fabricated for the characterization tests of the proposed composite.

Arteriovenous fistula (AVF) is a direct connection between an arterial and a venous vessel, used as the most common vascular access (AV) for patients undergoing hemodialysis (HD). The preparation of AVF causes non-physiological conditions of blood flow, inducing disturbances in the flow such as recirculation zones, stagnation points, high, low and oscillatory shear stress levels. These disorders are associated with the development of pathologies that promote stenosis in the vessel, which can compromise blood flow or even the loss of AVF. There are few studies on AVF in the literature that determine the flow field and its implications on the wall, for different anastomosis angles. An experimental bench was built to provide pulsatile flow in AVF models in vitro and in silico. The AVF was modeled three-dimensionally with angles of anastomosis varying between 30 ° and 150 °. Tests were carried out on the experimental bench to analyze the pressure profile. Other tests, with permanent flows, on AVF models with an anastomosis angle of 30 ° were also performed. The pressure profile for pulsatile flow demonstrates agreement with the blood pressure pulse in the literature, small time adjustments always necessary. The in vitro model of the FAV, printed by a 3D printer, was tested applying pressures from 0 to 45 kPa and no leaks were observed. The pressures in the anastomosis region of the in vitro model, for permanent flow, showed an increasing behavior due to the flow. The in silico model showed good agreement with the in vitro model, with a maximum difference of 4.8%, the others being less than 1.9%. The pressure distribution in the AVF wall showed maximum values in the external vein wall near the junction distal anastomotic, while low pressure levels were identified in the internal vein wall in the region of the proximal anastomotic junction. In correlation with the pressure distribution, the velocity field presented regions of stagnation and recirculation zones. To date, 52% of the project has been developed. In future works, it will be a working fluid implement with specific mass and adequate viscosity, installation of the temperature control system on the experimental bench and preparation of analysis of the AVF models with different anatomical angles.

With the modernization of the industry, the demand for more sustainable lubricants has grown exponentially worldwide, due to its renewable and biodegradable aspects. The properties of lubricants are conferred through their additives, however, most of these additives are compounds based on sulfur and other compounds that are toxic to the environment. In this context, the use of nanoparticles as an alternative additive has gained space and proved to be very efficient, however, wear reduction in nanoadditivated biolubricants occurs through mechanisms that need to be explained, which leads to the need for adequate characterization techniques for this. Raman spectroscopy is a technique that stands out in the characterization of tribomechanical systems, due to the ease of obtaining data without preliminary sample preparation. This work aims to instrument a pin-to-disk tribometer with a Raman spectrometer and a high-speed camera, in order to characterize the formation of lubricating film in lubricated systems that act under relative motion. The borderline lubrication regime was adopted, with low speed and with a variation of three loads, 100 N, 150N and 200 N. The Raman analysis was performed on top of the wear track, the tribopar used was SAE 1045 steel (Disc) and SAE 52100 steel (sphere), the lubricant used was pure epoxidized soybean oil and additive with DLC nanoparticles in concentrations of 0.05%, 0.1% and 0.2%. After tribological tests, the wear track on the disc was evaluated by scanning electron microscopy, Raman spectroscopy and profilometry. The results show that the developed Raman spectrometer is functional. For low additive concentrations, the surface rolling and surface mending mechanisms were identified, which improve lubrication and decrease wear; for higher concentrations, nanoparticles intensify the abrasive effect due to agglomeration with secondary nanoparticles and the formation of a third body

Accurate computations of radiative heat transfer in participating gases require detailed knowledge of the spectral data of radiative properties. This can be achieved either performing line-by-line calculations or using an accurate spectral model. In both cases, the absorption cross-section is computed from high resolution databases, which use to contain parameters for millions of spectral lines. The absorption cross-section depends on the local thermodynamic gas state, being a function of temperature, pressure and chemical species concentration, which vary with location in non-uniform gases. Therefore, the absorption cross-section must be computed and stored for diverse gas states, requiring considerable computational resources. In addition, the dependence of the absorptions cross-section with local gas properties poses complexity in radiation problems involving participating gases. This work proposes and evaluates an approximation in which the absorption crosssection is obtained by taking one or more thermodynamic properties as constant. Results of radiative transfer based on this approximation are obtained and analyzed. The local properties are temperature, molar fraction of each chemical species and pressure. The approximation reduces problems complexity and the size of the absorption cross-section database. It was evaluated for gases composed by CO2 and air, H2O and air, and mixtures of CO2, H2O and air. Uniform and nonuniform media were considered. Molar fractions of CO2 and H2O from 5 % to 100 % were considered, while temperatures varied from 500 K to 2500 K. Pressure was always 1 atm, except for those related to the approximation, where the pressure was given by a non-uniform profile. Results demonstrated that the approximation in which the absorption cross-section is obtained for a fixed molar fraction can be highly accurate when applied to non-isothermal and non-uniform gases.

Tribological tests are developed as a controlled way to evaluate the wear mechanism acting between metallic surfaces, as well as to observe the influence of the type of lubricant used. The lubricity assessment of a lubricant is standardized by the HFRR (High Frequency Reciprocating Rig) test, which is given by the sphere-disc tribological system in lubricated contact, and it produces as a result, images from the wear and the scar diameter is extracted, defining the Wear Scar Diameter - WSD. From a set of samples of different fuels applied as lubricants, images of the worn surfaces were obtained. Thus, it is proposed in this work to explore other characteristics of the images in addition to the WSD, thus
allowing a better description of wear and the type of lubricant used. With the images acquired in the HFRR test, image processing techniques were applied using the Matlab software and the OpenCV library to obtain quantitative
parameters. From this information, an Artificial Neural Network was able to classify new images according to the type of fluid applied in the lubrication, demonstrating the use of artificial intelligence to identify and classify wear patterns
from the analysis of their images.

The widespread use of gears in the industrial productive sector provides
engineering solutions for power transmission problems and leads scientific researches
in mechanical engineering o improve the efficiency of gearboxes by reducing the wear
and the friction between the gear. The improvement of the lubrication is one of the
ways to reduce friction and wear between the gears. Thus, this work aims to build and
test a tribometer capable of reproducing the contact between cylindrical spur gears in
order to promote wear on their teeth. The conceptual design was based on the
tribometer of the DIN ISO 14635-1: 2000 standard, which consists of the transmission
of power between two gearboxes interconnected by two parallel axes in the
back-to-back power recirculation format. The project has: (a) a loading system with
standard weights that aims to accelerate the wear on the gear teeth by applying torque
to the system by means of a caliper-disk brake system; (b) a rigid base of structural
aluminum profiles that has good rigidity and flexibility for expanding the tribometer in
the future; (c) a mechanical torque limiter with torque preload in order to ensure gear
engagement; and (d) an electrical system controlled by a programmable frequency
inverter. The projected components were manufactured at UFRN or purchased on the
market and, subsequently, were assembled at UFRN. After assembly, the tribometer
underwent a pilot test which aimed to: (i) verify the induction to wear on the teeth of
the gears with the aid of microscopic images; (ii) map the machine's working
conditions and variables; and (iii) optimize working conditions for the full functioning
of the tribometer. The rotation and loading parameters were varied at three different
levels each, configuring a 3² factorial study. Three response variables were measured:
electric motor current, motor torque and brake disc temperature. The results were
analyzed with the aid of the response surfaces method for the optimization of the work
parameters and obtained satisfactory results for the conduct of new studies.

This paper discusses the exergetic, exergoeconomic and exergoenvironmental analysis applied to a trigeneration system. An internal combustion engine powered by natural gas powers a mixed-effect absorption chiller and a heat exchanger to produce electricity, cooling and hot water. A solar field composed of vacuum tube collectors with two thermal tanks helps the system. The exergy model is based on the SPECO methodology and the life cycle assessment of the components used the Eco-indicator 99 method. The objectives of the study are the modeling of the trigeneration plant and the assessment of the economic and environmental feasibility of the system on an exergetic basis. . The results showed that the greater the global solar radiation, the higher the temperatures of the glass tube and the absorber plate and the thermal efficiency of the collector. The higher the proportion of exhaust gas, the higher the COP of the chiller. The solar field including the collectors and the tanks have the lowest exergetic efficiency. Reducing the reference temperature slightly increases the energy efficiency of the engine and the solar field. The efficiency of the absorption chiller reduces to a reference temperature of 15 ° C and increases at a temperature of 10 ° C due to the change in the product and fuel definition. The solar field and the evaporator showed the greatest exergoenvironmental factors, while the solution circulation pump and the HX1 heat exchanger obtained the greatest relative differences in environmental impact.

In this work we analyze the effect of the coupling of a Scramjet demonstrator in a Brazilian rocket engine, the VS-30 rocket, in terms of a numerical investigation of the flow along the fuselage geometry. We consider local aspects of the flow and the comparison of global flow parameters, namely the pressure distribution and the wall shear stress, for both geometries. The reference geometry of the rocket engine consists of a solid propulsion suborbital vehicle, while the Scramjet geometry was designed to be operated at flight conditions of Mach 5.79 and an altitude of 20 km. A set of 2D axisymmetric and planar numerical domains were generated for both geometries. We consider steady-state conditions in all cases, and for the modelling of turbulence, the transition k-kl-ω viscous model was used. The numerical simulations were able to capture the theoretically expected oblique shock and expansions waves that usually occur in the flow in these types of geometries. Local effects in the flow were observed such as the emergence of recirculation zones and hydrodynamic flow instabilities related to the interactions between the shock waves and the wall boundary layer. In addition, the aerodynamic drag forces, both drag and pressure, were quantified. We show that the Scramjet demonstrator coupled in the VS-30 can lead to an increase in 6,53% of the total drag on the vehicle, such increase can cause considerable deviations in the nominal trajectory of the VS-30 rocket.

Research on intelligent and autonomous mobile robots has grown significantly due to its military, civil and industrial applications, such as the monitoring of agricultural plantations, the use in actions to support environmental disasters, border patrol, mapping of submarine territories or even the study of animal behavior. This work rescues the multi and interdisciplinary motivation of artificial intelligence, starting from philosophical questions to reach the characterization of intelligent and autonomous systems. Thus, only after building the theoretical bases for the concept of these agents, a bioinspired approach
is presented for the trajectory tracking task by a mobile robot. For this purpose, the strategy consists of robust non-linear intelligent control using Sliding Modes, artificial neural networks and the Upper Confidence Bound algorithm. The characteristics of each technique give the robot robustness in the control task, learning and autonomy with decision-making, respectively. Thus, the algorithm developed for the trajectory tracking problem was designed based on the most recent arguments about autonomous agents and represents the growing trend of research in embodied cognitive science.

The Cu-SiC composite combines the high electrical conductivity and the good workability of copper with the good thermal conductivity, low density and abrasion resistance of SiC. Such characteristics allow it to be used as electrical contacts and heat sinks, however obtaining this composite is hampered by the mutual insolubility between its phases. Several studies use high energy milling (HEM) to prepare powders from immiscible systems with low wettability, as it produces greater refinement and homogenization of the phases, which increases the sinterability of the material. In this work, Cu-SiC composite powders with 2, 10 and 15% by weight of SiC were prepared by mechanical mixing and HEM in a planetary mill pulverissete 7 with container and hard metal milling bodies in liquid ethyl alcohol medium, 99,5 %, at 400 rpm for 2, 10, 20 and 30 hours. A mass ratio of powder to balls of 1:5 was used. Cu-2, 10 and 15% SiC powders were obtained at 200 MPa in a uniaxial cylindrical matrix. The green compacts were sintered in a tubular resistive oven with a dilatometric record at 1,000 ^oC for 1 h and under an argon atmosphere. The heating rate used was 10 oC / min. Analyzes of FRX, DRX, MEV and EDS were used to characterize both powders and sintered compacts. The size of crystallites and the deformation of the crystalline network of the Cu and SiC phases of the Cu-SiC powders were determined from the most intense diffraction peak using the Scherrer equation. Particle distribution analysis by laser spectroscopy was used to measure the particle size of elemental powders and Cu-SiC composites. The density of green and sintered compacts was obtained using the geometric method (mass / volume). The density of the sintered compacts decreases with the increase of the SiC content from 2 to 15% and the milling time from zero to 30 h. The Vickers microhardness of the sintered compacts increases with an increase in the SiC content and the values are higher for the ground powder compacts.

In recent years, there has been an increase in the search for techniques that allow the modification of surfaces without affecting the volumetric (bulk) physical properties of materials. Plasma-assisted surface modification is a surface modification technique that stands out from other surface modification techniques and processes due to its versatility, low impact on the environment and being economically viable, similar to conventional techniques in some respects, but with faster and non-polluting processes. Currently, titanium oxynitride obtained by plasma techniques stands out for presenting excellent mechanical, chemical, biomedical, optical and electronic properties. The search for devices which, in addition to mechanical resistance, offer an adequate relationship between bioactivity/biocompatibility when in contact with biological tissues emphasizes research on oxynitrides in the area of biomaterials. Thus, samples will be subjected to plasma treatment for surface modification, six study conditions were established for the work, where thermochemical treatments will be carried out in plasma atmospheres containing mixtures of H2 – N2 – O2. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) will be used for chemical composition analysis. The surface morphology will be evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). While the surface energy and contact angle will be obtained by the sessile drop method. To evaluate the bioactivity of the films, the samples will be immersed in simulated body solution, SBF (Simulated Body Fluid) and characterized).

The use of pumps installed in artesian wells for underground water extraction is a technique widely used in Brazil, especially in the Northeast, in places where drought is predominant during the year. In some regions, this extraction accounts for 70% of the population's water supply. Studies show that 50% of failures in electric motors start at the bearings and they represent only 30% of the total value of corrective maintenance. Given the above, the present work carried out a study on the radial bearings of the motors used in artesian wells. A low cost data acquisition system was developed through Arduino and MPU6050 sensor for capturing system vibration signals. The sensor was positioned close to the radial bearing. Five different bearing situations were analyzed. The first, with factory setting of 0.1 mm clearance between the shaft and bushing in the bearing, the second, third, fourth and fifth operating conditions were 0.2, 0.5, 1.0 and 3.0 mm of clearance, respectively. For each situation, the test was repeated six times for three minutes each. The data obtained in Arduino were studied through time and frequency domain analysis. For each operating condition it was possible to identify an operating pattern. Based on this, a diagnostic methodology for the study target engine was developed and put to the test in a case study.

In the context of multi-axis machining of mechanical components with freeform geometries, the conventional configurations of the dynamometers (stationary and rotary) are not suitable for operating conditions. This fact occurs due to the mounting of stationary devices limits the workpiece geometry and size, while the assembly of rotating devices is affected by interference in the signal under the conditions of high-speed spindle rotation. In order to propose a solution to this conflicting situation, this research has the objective of developing a hybrid dynamometer, based on strain gauges, mounted in the fourth axis of a vertical machining center and able to measure axial force and torque. Steps such as conceptual design, engineering analyses, instrumentation, static calibration and natural frequency evaluation were fundamental for manufacturing the device. In addition, the development of a wireless data transfer system have been developed. For this step, it was necessary to create a couple of printed circuits for signal conditioning and amplification, a wireless transmission module and a data processing code aiming the analysis of mechanical loading. The results showed that the conceptual design is appropriated to the dynamometer operating requirements to withstand loads of axial force up to 1 kN and torque up to 30 Nm, the dynamometer components were in accordance to the tolerances established in design, the performed instrumentation showed suitable to the application, the lower value of natural frequency of the device is 602,2 Hz.

The present work has the main purpose to investigate the cutting temperature when machining quenched and tempered AISI D6 tool-steel assisted by liquid nitrogen (LN2). Uncoated PCBN inserts were used as cutting tools during turning trials. Tool-work thermocouple was the method used in this investigation. In this technique, the contact between the workpiece and the cutting tool makes the hot junction of the thermocouple and the other extremities connected to the workpiece and the cutting tool makes the cold junction. By the Seebeck effect, as long as these junctions are submitted to different temperatures, an electromotive force will arise in the circuit which can be associated with the hot junction temperature. In order to obtain the relation between the hot junction temperature and the generated electromotive force, it was performed a calibration of the system using a conventional lathe. An oxyacetylene flame and an LN2 delivery system were used to obtain high temperatures (from the environment to 800oC, approximately) and low temperatures (including sub-zero temperatures), respectively. In order to minimize undesirable voltage, it was used the concept of physical compensation, where an element made of the same workpiece material was connected to the circuit. The results obtained through the calibration tests show a practically linear behavior between temperature and electromotive force along with the range of temperature used for calibration. Cylindrical turning trials were performed in which the cutting speed and the cooling condition (dry or LN2) were varied. A platform based on Arduino UNO was developed for data acquisition. It was observed a marginal reduction in the cutting temperature in the cryogenic condition compared to the dry condition.

The supersonic combustion ramjet, or scramjet, is a hypersonic airbreathing propulsion system that utilizes oblique or conical shockwaves to compress and decelerate air flow. Recent flight tests have demonstrated that there is viability in supersonic combustion concept, but such technology is not yet fully mastered. The objective of this Dissertation is to calculate and analyze the effects of vehicle speed variation on the supersonic combustion for a hydrogen/atmospheric air mixture on the scramjet demonstrator combustor. Three situations were evaluated: vehicle operation at design speed (Mach 6.8), lower speed (Mach 6.4) and higher than projected conditions (Mach 7.2) considering flight at a geometric altitude of 30 km for two methods of transverse fuel injection (single and double). Steady state flow was considered, calorically perfect gas and simplified chemical kinetic mechanism with 4 species and 1 chemical reaction (laminar finite-rate) and the turbulence modeled by the k-kl-ω transition model. Second order upwind schemes were used in the discretization. Variation curves of thermodynamic and species properties, visualization of the shock trains, flow contours and average properties at the isolator and combustor outputs are presented. The research revealed that there was an increase in thermodynamic properties and intensification of shock trains on the isolator with the increase of the flight speed and reduction of the amount of air admitted in the isolator due to different operational speeds, resulting from the repositioning of the inlet shock waves. Spontaneous fuel burning was contacted for all tested configurations. The burning was inefficient and kept between 10 and 22% where the double injection model was 51% more efficient than simple injection. There is then a speeds range that the vehicle can be operational. The geometry of the combustor can be extended to conserve heat energy and maintain combustion reactions within the channel longer.

Cutting fluids (based on mineral oil) are widely used in machining processes due to their lubricating and cooling properties. Their use, although quite advantageous to the process, has been questioned due to the presence of toxic substances in their composition that causes damage to the environment and problems of occupational health. This issue has been motivated the emergence of laws to restrict the use of certain products or components considered harmful. In this context, this work aided to evaluate and compare the machining performance of three vegetable-based nanolubricants (epoxidized soybean oil) with the addition of different nanoparticles (CuO, aC: H and CuO + aC: H), supplied in turning process of the tempered and tempered AISI D6 tool steel by MQL technique. For this, facing turning tests were performed with constant cutting parameters (vc = 100 m/min, ap = 0.3 mm and f = 0.1 mm/rot.) with PCBN cutting tools. For comparison, tests were performed with a mineral oil emulsion in flood technique and with pure vegetable oil (without the addition of nanoparticles) applied by MQL. The average roughness (Ra) of the machined surface, the wear and wear mechanisms of the cutting tools and the shape and appearance of the chips were investigated. The nanofluid of aC: H and the hybrid (CuO + aC: H), provided a longer useful life when compared to a dry condition, as well as chips with a higher thickness ratio, which may indicate, in an previous way, lower efforts for chip formation. For roughness, the wet condition was the one that presented the lower values, the MQL conditions presented lower values than those obtained with dry machining but without significant difference between them.

Calcium phosphate bioceramics are a group of highly attractive materials for biomedical applications. Some of these bioceramics have special attention, they are: hydroxyapatite-Hap [Ca10 (PO4) 6 (OH) 2], which has structure and composition similar to the mineral phase of human bone (apatite) and therefore has an excellent biocompatibility, high osteoinduction enabling bone regeneration; and calcium beta triphosphate (β-TCP), which has high bioadsorption in vivo. These materials are commonly used in the form of porous grains and synthesized or porous block in different areas of health sciences such as dentistry and orthopedics. It is known that the method used for the synthesis of ceramic material strongly influences the structure of the material obtained and in the case of Hap it must be formed by nanometric grains so that its structure is as similar as possible to the biological apatite.
It was possible to produce the nanometers by combustion reaction, after being sintered by plasma if dissipated from biphases, with the presence of Hap and calcium phosphate, with Mev in those without sintering they presented clusters of fibrous shape for glycine and acircular shape for urea , after sintered acetic separation of 127nm namometric size for glycine at 1000c and 172.26 nm for glycine at 1000C, Ftir In the analyzed we can see that all bands remained, regardless of temperature, as bands were preserved because no bond was broken in front temperature increase, remaining stable at the sintering temperature of 800 ° C and 1000 ° C.

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The search for materials that ofter greater strength and fracture toughness has provided improvements in the compositions of materials for use in cutting tools. The application of composite materials in this type of application offers several advantages due to characteristics improved by the combination of metals and ceramics. The ceramics are superior in their hardness, chemical stability and refractory character, however, the main negative point is the gragility. In order to minimize this factor, several percentages of nickel were evaluated in the alumina ceramic matrix. Microcrystalline Al2O3-Ni powders can be produced by hight energy ball mill, as well as dense structures with better mechanical properties can be obtained by sintering with liquid phase. This work investigates the effect of the percentages of nickel micrometric powders added on the alumina matrix using the SPS sintering method “Spark Plasma Sintering” of the composites. The proportions used were: 0%, 5%, 10% and 20% by mass of nickel (Ni) in a carbon matrix of 5 millimeters in diameter. The powders were ground in a hard metal container with carbide beads in C3HO (H3C-HCOH-CH3) isopropanol solution, using 5:1 mass/ball ratio, where all the composite preparation powders were milled by up to 50 hours. In the 5% nickel pilot assay sample oh the mixture were collected after 2, 10, 20, 30, 40 and 50 hours of milling. The sintering was performed at a temperature of 1350°C, 1500°C and 1650°C by the SPS method for 6 minutes at the respective worked temperatures. The characterization of the starting powders mixtures and the composite contained before and after sintering were analyzed by physical-chemical, microstructural and mechanical tests. In general, the characterization of composites and ceramics powders was obtained through mechanical, physical and tribological tests. 

Functional textile materials have been extensively researched and developed to be used in different areas of science, environment, and technological materials. With the help of natural polymers, we can develop products with various properties and endless applications. The increase in consumption and the variety of the use of textiles in the health area have been expanding. There is  a vast  need for new methodologies that provide specific properties to textile materials such as biocompatibility, high resistance to acids, alkalis and microorganisms, good dimensional stability, flexibility, absence of impurities, absorption/repellency to liquids, among others. Therefore, this research proposes to develop a functional textile material with antimicrobial properties, to obtain nanometric systems of type the O/A (OIL/WATER) to solubilize citronella oil (Cymbopogon nardus L.) and neem (Azadirachta indica A. Juss) as antimicrobial agents to be applied to the textile substrate. Chitosan is a bioactive natural polymer and has a wide variety of applications due to its properties, and also being an antimicrobial agent. In this work, it has been used as a surface modifying agent of a soy fabric. The essential oils were obtained commercially and reduced in microemulsions, using two types of emulsifiers, surface-active agents, tween 80 and a natural agent produced from neem oil. Two formulations of microemulsions with particle sizes on a nanoscale and good chemical stability with antimicrobial properties were developed. Analyses were performed to characterize the oils, the natural surface active agent, the microemulsions and the functionalized fabric. Antimicrobial activities against Staphylococcus aureus and Escherichia coli bacteria were evaluated, where bacterial growth was inhibited for each of the formulations of the nanometric systems.

The continental dimensions of Brazil and the distance from the power generating units (usually hydroelectric) of the consumer centers are factors that raise the importance of the distribution networks, since an unexpected failure due to fatigue in the conducting cables, can reach tens of millions of consumers involving therefore, very high costs. To estimate the remaining cable life of these lines, sophisticated laboratories and long tests are necessary to obtain S-N curves with the same level of average voltage applied in the field. Thus, it becomes desirable a model capable of predicting the resistance to fatigue of conductive cables effectively, simplifying the need for testing and the costs, in addition, of course, the risks of blackout. In this sense, this study seeks to create ANN architectures capable of estimating the fatigue strength of aluminum conducting cables, by varying the cable's structural parameters such as the specific weight (W), the flexural stiffness module (EI) and the Poffenberger-Swart constant K, taking into account the average tension (stretching load) and the number of cycles to which the cables are subjected. The training and testing of the ANNs was done through a set of data obtained from fatigue tests carried out in the cable laboratory of the Fatigue, Fracture and Materials Group (GFFM) of the Federal University of Brasília (UnB) for different types of cables of aluminum alloys. Through the ANNs, constant life diagrams will be constructed for this family of cables, making it possible to compare the results obtained experimentally and those obtained by the ANNs through the mean quadratic error. The results obtained by the ANNs proved to be very promising, managing to generalize the resistance to fatigue for the aluminum conductor cables analyzed.

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This work proposes a NURBS-based technique to design interfaces of adjacent disparate microstructural domains. The mentioned technique will be employed as a structural compatibility tool in multiscale optimization methods, providing physical consistency to designed structures, allowing them to be manufacturable, as well as preventing performance loss due to post-processing changes in optimum solutions. A computational code - based on trimmed NURBS surfaces – was implemented and used to perform numerical simulations of compatibility between adjacent microstructural domains. The results demonstrate the feasibility of the proposed technique.

The carnauba, the tree of life is a palm tree found in regions of Brazil and has many applications, from electronics to cosmetics, with a greater emphasis on wax. A polymer matrix composite of polyester resin and petiole powder, a fibrous part of the straw, was obtained and studied. The powder was obtained using forage grinding and subsequent sieving, generation residues with different grain sizes. All the obtained granulometries were tested and the smaller one was chosen, due to is greater viability to obtain the composite, due to is better processability. Three mass proportions of the mixture between matrix and residues were chosen, 5%, 7.5% e 10%, since above that percentage there was a compromise in the processability and obtaining the composite studied. Mechanical, thermal and environmental characterizations were performed, which demonstrated the feasibility of the proposed composite. The carnauba powder was shown to be present in the composite as filler. The best formulation, 10%, was chosen for the manufacture of a decorative panel to be used as TV stand and could also be used for the manufacture of furniture and parabolas for solar cookers.

The CO₂ capture and storage (CCS) and concentrated solar power (CSP) from power plants are potential emissions mitigation systems. A natural gas combined cycle in Brazil is taken as case study, and these two options are analyzed and compared using exergoeconomic and exergoenvironmental impact (EI) approach for electricity production. The CSP technology used is a parabolic trough collector (PTC) and the environmental impact indicator used is the eco-indicator 99. A detailed assessment of cost and EI for components, input and infrastructure were carried out. The outcomes indicate a decrease of the EI rate of CCS (2^nd case) by 70% and a decrease in specific EI of PTC (3^rd case) by 1.78%. On the other hand, the specific costs of electricity were increased for both options by 15.90 % for the CCS and by 9.78% for the PTC. Discussions about further improvements have been proposed.

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Drag is one of the main energy dissipation agents in engineering applications. Reducing dragging mechanisms have been studied in order to reduce this cost. The superhydrophobic surfaces have high water repellency and have been studied as an alternative mechanism to reduce drag. The high level of repellency is due to the hierarchical structures in the existing micro and nano scales, causing these surfaces to trap air layers and, consequently, impose a slipping condition. This type of surface has a high biomedical potential with several applications and that, acting as a drag reducer in internal flows, can solve the existing gap in the production of hydrophobic and flexible tubes. Based on this, the present work aims to investigate the phenomenon of drag reduction in flexible pipes manufactured in Sylgard® 184 elastomer and modified internally by low pressure plasma treatments. Treatments were performed in flat samples of the elastomer in use, aiming to find the best configuration of the plasma regime that would raise the hydrophobicity level of these. Atmospheres with 40% and 60%, and 20% and 80% of argon and acetylene respectively were used, varying in treatment times of 10, 15 and 20 minutes of acetylene exposure. The surface morphological and chemical modifications were analyzed and proved by XPS and AFM techniques, showing the impression of a rough structure on the nanometric scale with deposition of chemical elements by the polymerizing solution. The wettability of the treated surfaces was measured by the static contact angle with the water, proving the superhydrophobicity state.

Plasma assisted sintering is the procedure in which the compacted powder is subjected to a luminescent discharge cloud of ionized gas which, when interacting with the surface of the part, allows heating and densification of the particulates. Plasma sintering methods can produce materials with high degrees of performance under highly reductive atmospheres, fine temperature control and reduced processing time when compared to conventional sintering methods. It is proposed to analyze the effects of plasma sintering on austenitic stainless steel AISI 316L, evaluating the effects of changing treatment parameters, in order to determine the ones that best suit the production of sintering with good densification. The study of the treatment parameters was initiated with the sintering of compacted samples at 700MPa, sintered under argon atmosphere, with a 30 minute isotherm time at an apparent temperature of 730 ° C. In this step, sintering was performed using planar hollow cathode and cylindrical hollow cathode. The samples were evaluated for the relative percentage of porosity, pore geometry and rate of heating provided by the cathode. It was observed that sintered samples with cylindrical hollow cathode showed reduced porosity with a high degree of circularity. Then, using cylindrical hollow cathode, under the same sintering parameters, the effects of the compression pressure variation in the samples were evaluated, using pressures of 555MPa, 655MPa, 700MPa, 750MPa and 800MPa. The pore geometry and distribution, grain size, crystal structure, apparent hardness and microhardness of the samples were studied in the sintered samples. Sintered samples with compaction pressures of 750MPa and 800MPa showed the best results. Samples compacted at 800MPa were sintered at rates of 9.17 ° C

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Over the years, the contribution of photovoltaics energy to an eco-friendly world is continually increasing and its costs reducing. In PV technologies, the solar cell temperature and incident solar radiation are the main factors that affect their behaviors. The focus of this work will be the temperature, in view of the few numbers of investigations currently available in literature which covers simultaneously the equivalent electric models and all aspects of the temperature influence on performance parameters of solar cells. Therefore, to bridge this gap, a study on the impact of cell temperature on the performance parameters of silicon solar cell and a search for the most suitable model to emulate a solar cell when its operation temperature varies are undertaken in this work. The experiment will be carried out using a polycrystalline silicon solar cell with the temperature in the range 20–60 °C at constant light intensity 1,000 W/m2 employing a solar cell simulator (SOLSIM) developed by the INPE and adapted by the author. In this work, the main existing research works on PV cell model parameter estimation problem are classified according to number of parameters, parameters’ extraction, translation equations and PV material technology. The main existent models were discussed pointing out their different levels of approximation. A qualitative comparative ranking was made, and four models was found to be the best ones to emulate PV cells per the aspects considered, and a specific model with greater potential was highlighted. It was made a brief review of the various existing mathematical relationships involving the influence of temperature over solar cells. A possible solution to soften the efficiency reduction caused by the temperature is presented. Using this solution is expected the improvement of the performance of PV devices can be expected.

A combined cycle natural gas power plant is taken as a case study. Two types of CO2 mitigation are analyzed for this case, the carbon capture and storage system (CCS) and concentrator collector (CSP) type parabolic trough collector (PTC) with two thermal fluid storage tanks (Therminol VP-1). The method of analysis chosen was the exergoeconomic and exergoenvironmental analysis. The chosen method of environmental impact was the Eco-Indicator 99 (EI-99). A detailed analysis of cost and environmental impact for the components, inputs and infrastructure was carried out. The results indicate that the gas heater needs to have its destroyed exergy reduced to improve the efficiency of the system as a whole. The second case - with CCS system - had its electric power reduced, while the third case - with solar collector - increased. The environmental impact of electricity increased with the 2nd case and with the 3rd case had a slight increase. The environmental charge of the thermal fluid was taken into account. Therefore, the third case was the system with better environmental performance and discussions for future studies and improvements were carried out.

In aviation, the pursuit of more efficient aircraft has grown in the face of concerns
by governments and organizations about the environment, forcing new aircraft
projects to emit less and less CO2 into the atmosphere. Aircraft manufacturers then,
to remedy the various problems, focus primarily on wing design, empennage,
fuselage and engines, which are the most significant aerodynamic components. All
of them have in common a vital part in the projects, which is the profile. In the
present work we sought to find an optimal profile with a multiobjective approach. In
Matlab, a genetic algorithm will optimize the profiles through an iteration with XFOIL,
where the aerodynamic characteristics of the profiles, represented by their
coefficients (Cl, Cd, Cm and Cl / Cd), are obtained. In order to obtain a good
population diversification and thus finding the ideal profile, combining the most
diverse geometric characteristics, 300 different profiles were available as source for
the initial population generation, which were available in the Airfoil Data Site
database. For XFOIL simulation, the air density was adopted as 1.225 kg / m³, a
viscosity of 1.79e-5 Pa.s, reynolds no. 5.00e5, mach no. 0.05, ncrit 9, no. maximum
convergence iterations of 100 and an angle of attack range from 0º to 18º. For the
genetic algorithm, a 90% crossover probability, 5% for mutation, a search
exploration outside the 30% range and a maximum number of 100 generations were
adopted as stopping criteria for the population. The optimized profiles outperformed
other studies in relation to the aerodynamic coefficients such as efficiency and Cl,
but not so much in relation to Cm. The algorithm proved to be satisfactory in finding
profiles that aimed to improve Cl, Cd, and consequently efficiency, finding higher
profiles by 32% Cl for flying wings, 67% Cl for empennage and better efficiencies
by about 70% for wind turbines. The algorithm was able to achieve better and better
profiles compared to others commonly used in the mentioned applications, besides
obtaining characteristics such as softer stall and wind turbine noise reduction. For
future work, it is suggested to investigate a larger number range of Reynolds, and
other aerodynamic solvers, in addition to implementing the inverse method
optimization, aiming to obtain an optimal pressure distribution.

Mechanical failures of machine equipment and components cause loss of required function performance and unexpected stops, resulting in an increase in the need for corrective maintenance, which increases maintenance costs and reduces the reliability of mechanical systems. The effect of medium stress plays an important role in fatigue life prediction, its influence significantly changes the high-cycle fatigue behavior (HCF), decreasing the value of the fatigue limit with the increase of the mean stress. Geometric discontinuities - such as a change of cross-section, holes, notches, among others - cause a considerable increase in the value of the nominal stress acting in the adjacent vicinity of the stress concentrator. This potentiates the effects of the positive mean stress on the damage over the life cycle of the material, causing direct influence on the calculation of the fatigue resistance factor (Kf). Numerous empirical models, such as Gerber, Goodman, Soderberg and Morrow, have been developed to describe the mean stress effects, but despite the advances, a unified model that considers the stochastic behavior of fatigue failure that predicts the stresses maximum amplitude values supported in the high cycle region for the notched material. In this way, the purpose of this work is the developing of a new artificial constant life diagram (stress amplitude vs. mean stress) based on an artificial neural network applied to metallic materials and structural details, capable of estimating the fatigue resistance reduction factor for different mean stresses. The results showed that the trained neural network was able to determine regions of reliability of operation of the material under the aspects of the mean stress, stress amplitude, stress ratio and stochastic behavior of the number of cycles to failure. In addition, it was possible to estimate the values of the fatigue strength reduction factor corresponding to the resistance limit using a small amount of experimental data.

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Waste production in industries has been a recurring concern in recent years. With increasing environmental awareness, several recommendations on waste management have been developed to protect the environment and society, the main one being the minimization of their production. When impractical, the next suggested action is reuse or recycling. In the oil industry well drilling generates large volumes of wastes that are deposited in landfills and accumulated. The mineral extraction industry, in the same way, generates large amounts of waste in the preparation of the product for commercialization: about 70% of the extracted volume. Several authors have studied the incorporation of these residues in the development of new products, mainly ceramics, due to the heterogeneity of their composition. This work, therefore, has the objective of developing a glass ceramic from petroleum drilling residues from the potiguar area, and tailings from the processing of the Caulim of the city of Equador / RN. As an innovative proposal, the residue samples were characterized in order to obtain the best formulation based on SiO2-Al2O3-CaO-Na2O-K2O-MgO composition. The mixture of 10g of gravel, 5g of kaolin and 2.5g of Na2O was then melted at 1500ºC for 1h, obtaining a glass afterwards subjected to FRX, TG-DSC and DIL analysis to support the preparation of the glass ceramic. Vitreous powder pellets were produced and sintered at 800 ° C for 30 minutes to study the densification and crystallization of the material. The structure and properties of the glass ceramic were analyzed by XRD, FRX, TG and MEV, which proved the viability of the residues in their production.

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O compósito de matriz metálica de cobre reforçada por dispersão de partículas de carbeto de tungstênio (WC) exibe alta condutividade elétrica, boa trabalhabilidade e resistência ao desgaste. Tais características fazem desse material um forte candidato para aplicações em condutores e contatos elétricos de alta potência. A resistência do compósito Cu-WC pode ser aumentada por dispersão fase dura de WC na matriz de cobre através da moagem de alta energia. Com isso, estruturas com finos grãos sólidos, homogêneas, densas e, portanto, de melhores propriedades físicas e mecânicas são produzidas quando pós compósitos de Cu-WC são preparados por moagem de alta energia e sinterizados. Neste trabalho, o efeito da moagem de alta energia na densificação e estrutura do compósito Cu-20%WC bem como nas propriedades físicas e mecânicas foram investigadas. A influência da pressão de compactação dos pós preparados por moagem e mistura mecânica na densidade e nas propriedades de condutividade elétrica e magnética também foi averiguada Um moinho planetário Pulverisatte 7 de alta energia foi utilizado para efetuar os experimentos de moagem. Pós de Cu e WC na razão de 20% em massa de WC foram colocados para moer em um recipiente com bolas de metal duro e álcool etílico. Os pós foram moídos a 400 rpm, com uma razão massa/bola de 1:4 durante 50 horas. Amostras de pós foram coletadas após 2, 10, 20, 30 e 40 horas de moagem. Corpos verdes com forma cilíndrica foram prensados a 200, 400 e 600 MPa em matriz uniaxial. Tais corpos verdes foram sinterizados a 1050 ^oC por 60 min. em forno resistivo sob atmosfera de uma mistura de hidrogênio e argônio. A densidade dos compactados a verde, e dos sinterizados foi calculada pelo método geométrico (massa/volume). Para observar a microestrutura dos corpos sinterizados, análises de microscopia ótica e eletrônica de varredura foram efetuadas. Análises químicas de FRX e EDS foram usadas para detectar a presença de impurezas nos pós elementares e moídos. Análise de DRX foi usada para detectar as fases presentes e medir os cristalinos dos pós. Os cristalinos das fases Cu e WC sofreram uma intensa diminuição alcançando, respectivamente, 29,6 e 45,8 nm; assim como, a magnetização diminuiu de 1,04 emu/g para 0,5694 emu/g após 50 horas de moagem. Por outro lado, a coercividade do compósito aumentou de 64,86 G para 189,325 G e a remanência aumenta de 0,0485 emu/g para 0,14935 emu/g. As medidas de condutividade elétrica, magnetização, coercividade e remanência dos corpos sinterizados mostram que tais propriedades aumentam com a pressão de compactação dos pós compósitos.

A injeção de vapor é um método de recuperação de petróleo realizado injetando vapor diretamente no poço até o reservatório. O vapor provoca a dilatação do revestimento, que após a redução na temperatura tende a voltar às dimensões iniciais, provocando a formação de trincas no cimento e perda de isolamento hidráulico. Neste contexto, o Látex do tipo SBR é utilizado para melhorar a flexibilidade da matriz do cimento reduzindo as falhas por fadiga.  Para evitar estas falhas, os parâmetros de resistência mecânica devem ser rigorosamente ajustados às condições do poço. Para o estado fresco, as pastas de cimento devem permanecer fluidas e homogêneas, durante o bombeio, para que seu deslocamento não comprometa a janela operacional do poço. Este trabalho tem como objetivo estudar o comportamento mecânico de sistemas de pasta de cimento Portland, aditivadas com Látex SBR, para cimentação de poços de petróleo sujeitos à injeção de vapor. Através do planejamento fatorial composto central foi estudado o comportamento da resistência à compressão API variando a densidade da pasta entre 1,75g/cm³ (14,6 lb/Gal) e 1,89 g/cm³ (15,8lb/Gal), o tempo de cura entre 4 dias e 28 dias e concentração de Látex SBR entre 0 L/m³ e 534,722 L/m³ (0 gpc e 4 gpc). Os resultados apontam que o com o aumento da concentração do látex SBR, dentro os intervalos determinados, ocorreu uma diminuição significativa da resistência à compressão pelo aumento da capacidade de deformação elástica da pasta. A partir dos resultados obtidos é possível determinar melhores condições de formulação de pastas aplicáveis em operações de cimentação de poço de petróleo sujeito à injeção de vapor.

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O número de implantes e a preferência dos mesmos em relação às próteses vêm crescendo a cada ano no Brasil, assim como os profissionais habilitados para tal procedimento. Com isso, é necessário que haja estudos sistemáticos sobre a dinâmica que ocorre entre o par osso-metal no sistema. Utilizou-se osso suíno para a confecção dos corpos-de-prova devido ao fácil acesso ao material. Ensaiou-se e submeteu-se em laboratório o sistema a esforços de flexo-torção, quantificando-se o "backlash" (folga) após 10^5 ciclos. Investigou-se também danos na estrutura óssea devido às solicitações mecânicas cíclicas aplicadas. Também se avaliou microscopicamente o conjunto parafuso-porca. Este estudo possibilitou identificar que a temperatura registrada durante a maioria dos ensaios manteve-se numa faixa entre 20 e 30°C, a aceleração de vibração global e a pressão sonora demonstram que até 10^4 ciclos o contato entre porca calota e parafuso da haste é não conforme, com rugosidade elevada, confirmando a passagem pelo período de running in do par tribológico metal-metal, enquanto que após 10^4 ciclos há o aumento parâmetros, anteriormente citados, até o término do ensaio, passando a existir um contato conforme no período de regime permanente (steady steak). O Backlash mensurado identificou um valor máximo médio de 0,49mm. Debris, formação de proa, trincas e delaminação foram observadas no MEV do osso e da porca-calota. O par osso-metal ainda foi submetido a um ensaio de tração, obtendo-se um gráfico força versus deformação.

Filmes finos de TiO₂ podem ser a resposta para grandes questões atuais sobre as melhores maneiras de obter energia, economizar energia e reduzir a poluição. Tais filmes têm sido aplicados com sucesso para produção de células solares; como camada em janelas inteligentes, janelas fotocrômicas e eletrocrômicas; além de possuírem propriedades fotocatalítica interessantes. Este trabalho explora a importância tecnológica e científica desse material realizando investigações a respeito dos filmes de TiO₂, sua forma de deposição, técnicas de análise, detalhando formas atuais de análise óptica, buscando, de maneira inovadora, comparar tais técnicas, validar seu uso, e comparar seus resultados na busca de meios econômicos da realização de investigações a respeito de espessura, estrutura e avaliação de propriedades fotocatalíticas do material produzido. Nesse trabalho foram utilizadas, para criação de filmes finos, deposição física pelo método de magnetron sputterin. Para análise óptica e cálculo de espessura e Band Gap dos filmes será apresentado o Método do Envelope que foi originalmente proposto por Manifacier (Manifacier, Gasiot e Fillard, 1976) sendo que mais tarde Swanepoel (1983) conseguiu melhorar ainda mais a precisão desse método para encontrar propriedades ópticas dos filmes finos e sua espessura. Também será apresentado, a aplicação de equações propostas nos trabalhos de Lindgren (Lindgren et al., 2003) e a Lei de Beer-Lambert para cálculo do Coeficiente de Absorção dos filmes, outro dado importante para mais tarde determinar o gap dos mesmos, que será encontrado pelo Método Tauc. Para filmes muito finos, com poucas ou nenhuma franja de interferência se faz necessário o estudo de algum Método Computacional para determinação dos seus parâmetros ópticos e espessura. Para tanto utilizou-se o Método PUMA, um Método Computacional desenvolvido por pesquisadores da UNICAMP/USP. Os filmes depositados foram analisados por DRX, EDS, além de serem submetidos a análise óptica, MEV transversal buscando validar os métodos ópticos em termos das espessuras recuperadas, além de encontrado seus Band Gap e seus valores comparados com o esperado pela literatura confrontando tais resultados com a cristalinidade obtida para os filmes.

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Os materiais compósitos surgem da necessidade de materiais mais leves e com maiores resistências mecânica e térmica. As dificuldades de descarte, reciclagem ou reutilização são hoje preocupações ambientais e por isso objeto de estudo de muitas pesquisas. Nessa perspectiva estudou-se a viabilidade do uso da bucha vegetal (Luffa Cylindrica) para a obtenção de um compósito de matriz polimérica. Foram testadas seis configurações/formulações, com 4, 5 e 6 camadas tratadas e não tratadas. As buchas foram tratadas em água fervente para retirar ligninas, ceras e impurezas presentes nas fibras, posteriormente secadas em secador solar de exposição direta. Para a caracterização do compósito foram determinadas propriedades térmicas (condutividade, capacidade térmica, difusividade e resistividade), mecânicas (tração e flexão) e fisicoquímicas (MEV, DRX, densidade, absorção e degradação). Uma das vantagens do compósito proposto foi a baixa densidade das fibras, 066 g/cm³, quase metade da matriz de resina poliéster, produzindo uma densidade média do compósito em torno de 1,17g/cm³, inferior em 6,0% em relação a matriz. O tratamento realizado nas buchas trouxe aumento na resistência mecânica do compósito e diminuição da absorção de umidade. O compósito apresentou comportamento mecânico inferior ao da resina matriz para todas as formulações. O compósito também demonstrou-se viável para aplicações térmicas, com condutividade térmica inferior a 0,159 W/mk, classificando-se como um bom isolante térmico. Para todas as formulações/configurações ocorreu uma baixa aderência entre fibras e matriz, com fissuras presentes, mostrando fragilidade em função da baixa impregnação da fibra pela matriz. Tal compósito pode ser utilizado para a fabricação de estruturas que não requeiram significativa resistência mecânica, como por exemplo, protótipos solares, como fornos e fogões.

A constante e atual busca de alternativas sustentáveis tem levado a demanda de esforços dos pesquisadores na investigação e obtenção de novos materiais, motivando a escalada do desenvolvimento produtivo ecologicamente correto e apresentando soluções simples e prática com rentabilidade econômica viável. Neste sentido, a utilização de materiais procedentes de fontes renováveis naturais, vegetais, apresenta grande potencial de aplicabilidade e são vistos como material alternativo para um desenvolvimento sustentável. A sustentabilidade questionada, dentre outros quesitos, depende da renovável multiplicação da matéria-prima. Como material alternativo as fibras vegetais podem ser aplicadas para produção de uma gama de materiais compósitos amenizando o uso de materiais oriundos de fontes não renováveis Nesta tese foram utilizadas mantas de sisal para obtenção de um compósito tendo como matriz uma resina poliéster ortoftálica. As mantas foram submetidas a tratamento superficial, em água fervente, por 15 minutos. As mantas de fibras de sisal utilizadas tinham, respectivamente, 5%, 10% e 15% da massa do compósito. O compósito foi obtido e caracterizado mecânica e termicamente para as formulações escolhidas. Foram fabricadas várias placas do compósito para obtenção dos corpos de provas para os ensaios de caracterização obedecendo às normas pertinentes. Os compósitos obtidos apresentaram resistência mecânica de tração e flexão inferiores à da matriz, sendo viável sua utilização onde são requeridas baixas solicitações de carga. O resultado mais expressivo do compósito estudado deu-se para a absorção de energia de impacto, muito superior a da matriz utilizada. Outras propriedades de destaque foram a absorção em óleo e a densidade. Provou-se a viabilidade de obtenção do compósito para as três formulações estudadas C5, C10 e C15, cuja mais viável foi a C10. Para demonstrar a viabilidade de utilização do compósito foram fabricados um relógio de parede, um banco, uma cadeira e uma prateleira, estruturas de baixas solicitações mecânicas. Concluiu-se que as mantas de sisal exerceram a função de carga no compósito.

Esta pesquisa apresenta uma abordagem a cerca do processo de reciclagem do polipropileno reforçado com fibras de curauá reprocessado.  Sendo uma proposta alternativa de reforço aos compósitos poliméricos. Teores de fibras de 0%, 10%, 20% e 30% foram analisados para verificação de suas propriedades mecânicas comparando-as, inclusive com as propriedades do polipropileno (PP). Os biocompósitos granulados foram preparados em uma extrusora. Os corpos de prova foram moldados por processo de injeção e submetidos aos ensaios mecânicos de tração uniaxial, flexão em três pontos e impacto. Para verificação de danos aos corpos de prova utilizou-se da análise por microscopia eletrônica de varredura (MEV). Estes biocompósitos também foram submetidos a ensaios físico - químicos de índice de fluidez (IF). Observou-se que os biocompósitos de polipropileno com 30% de fibras de curauá apresentaram maior módulo de elasticidade e menor resistência ao impacto. Para todos os biocompósitos, os valores encontrados nos ensaios de tração para os limites de escoamento e tensão de ruptura não sofreram alterações à medida que se adicionavam as fibras. Outros pontos relevantes foram o aumento da resistência à flexão, a redução da degradação térmica das misturas polipropileno e fibras de curauá, e o não comprometimento de uma forma em geral, da fabricação dos biocompósitos, quando analisados por microscopia eletrônica de varredura.

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