984 resultados para Helder Júnior
Resumo:
This work had to verify the influence of massará, while mortar component, in the process of formation of saltpeter in cementitious plaster walls of buildings. The massará is a ceramic material, texture areno usually found in large volumes argillaceous sediments in Teresina, Piaui State capital, which is associated with the Portland cement mortar form for fixing and finishing in construction. Saltpeter or flowering is a pathology that happens in gypsum wallboard, which invariably reaction between soluble salts present in materials, water and oxygen. This pathology, supposedly credited to massará caused its use to suffer significant reduction in the market of the buildings. Verify this situation with particular scientific rigor is part of the proposal of this work. Grading tests Were performed, consistency limits (LL, LP and IP), determination of potential hydrogen, capacity Exchange (CTC), electrical conductivity (EC), x-ray fluorescence (FRX) and x-ray diffraction (DRX). Massará analysed samples in number six, including sample plastering salitrado presented potential hydrogen medium 5.7 in water and 5.2 on KCl n and electrical conductivity (EC), equal to zero. These results pointed to the affirmative that massará is a material that does not provide salinity content that can be taken into consideration. It is therefore concluded that the material analyzed not competing, at least with respect to the presence of soluble salts, for the formation of saltpeter
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The ionic plasma nitriding is one of the most important plasma assisted treatment technique for surface modification, but it presents some inherent problems mainly in nitriding pieces with complex geometries. In the last four years has appeared a plasma nitriding technique, named ASPN (Active Screen Plasma Nitriding) in which the samples and the workload are surrounded by a metal screen on which the cathodic potential is applied. This new technique makes possible to obtain a perfect uniform nitrided layer apart from the shape of the samples. The present work is based on the development of a new nitriding plasma technique named CCPN (Cathodic Cage Plasma Nitriding) Patent PI 0603213-3 derived from ASPN, but utilizes the hollow cathode effect to increase the nitriding process efficiency. That technique has shown great improvement on the treatment of several types of steels under different process conditions, producing thicker and harder layers when compared with both, ASPN and ionic plasma nitriding, besides eliminating problems associated with the later technique. The best obtained results are due to the hollow cathode effect on the cage holes. Moreover, characteristic problems of ionic plasma nitriding are eliminated due to the fact that the luminescent discharge acts on the cage wall instead of on the samples surface, which remains under a floating potential. In this work the enhancement of the cathodic cage nitriding layers proprieties, under several conditions for some types of steels was investigated, besides the mechanism for nitrides deposition on glass substrate, concluding that the CCPN is both a diffusion and a deposition process at the same time
Influência das espécies ativas na absorção de intersticiais durante a carbonitretação a plasma do TI
Resumo:
Physical-chemical properties of Ti are sensible to the presence of interstitial elements. In the case of thermochemical treatments plasma assisted, the influence of different active species is not still understood. In order to contribute for such knowledge, this work purposes a study of the role played by the active species atmosphere into the Ar N2 CH4 carbonitriding plasma. It was carried out a plasma diagnostic by OES (Optical Emission Spectroscopy) in the z Ar y N2 x CH4 plasma mixture, in which z, y and x indexes represent gas flow variable from 0 to 4 sccm (cm3/min). The diagnostic presents abrupt variations of emission intensities associated to the species in determined conditions. Therefore, they were selected in order to carry out the chemical treatment and then to investigate their influences. Commercial pure Ti disks were submitted to plasma carbonitriding process using pre-established conditions from the OES measurements while some parameters such as pressure and temperature were maintained constant. The concentration profiles of interstitial elements (C and N atoms) were determined by Resonant Nuclear Reaction Analysis (NRA) resulting in a depth profile plots. The reactions used were 15N(ρ,αγ)12C and 12C(α,α)12C. GIXRD (Grazing Incidence X-Ray Diffraction) analysis was used in order to identify the presence of phases on the surface. Micro-Raman spectroscopy was used in order to qualitatively study the carbon into the TiCxN1 structure. It has been verified which the density species effectively influences more the diffusion of particles into the Ti lattice and characteristics of the layer formed than the gas concentration. High intensity of N2 + (391,4 nm) and CH (387,1 nm) species promotes more diffusion of C and N. It was observed that Hα (656,3 nm) species acts like a catalyzer allowing a deeper diffusion of nitrogen and carbon into the titanium lattice.
Resumo:
It seeks to find an alternative to the current tantalum electrolytic capacitors in the market due to its high cost. Niobium is a potential substitute, since both belong to the same group of the periodic table and because of this have many similar physical and chemical properties. Niobium has several technologically important applications, and Brazil has the largest reserves, around 96%. There are including niobium in reserves of tantalite and columbite in Rio Grande do Norte. These electrolytic capacitors have high capacitance specifies, ie they can store high energy in small volumes compared to other types of capacitors. This is the main attraction of this type of capacitor because is growing demand in the production of capacitors with capacitance specifies increasingly high, this because of the miniaturization of various devices such as GPS devices, televisions, computers, phones and many others. The production route of the capacitor was made by powder metallurgy. The initial niobium powder supplied by EEL-USP was first characterized by XRD, SEM, XRF and laser particle size, to then be sieved into three particle size, 200, 400 e 635mesh. The powders were then compacted and sintered at 1350, 1450 and 1550°C using two sintering time 30 and 60min. Sintering is one of the most important parts of the process as it affects properties as porosity and surface cleaning of the samples, which greatly affected the quality of the capacitor. The sintered samples then underwent a process of anodic oxidation, which created a thin film of niobium pentóxido over the whole porous surface of the sample, this film is the dielectric capacitor. The oxidation process variables influence the performance of the film and therefore the capacitor. The samples were characterized by electrical measurements of capacitance, loss factor, ESR, relative density, porosity and surface area. After the characterizations was made an annealing in air ate 260ºC for 60min. After this treatment were made again the electrical measurements. The particle size of powders and sintering affected the porosity and in turn the specific area of the samples. The larger de area of the capacitor, greater is the capacitance. The powder showed the highest capacitance was with the smallest particle size. Higher temperatures and times of sintering caused samples with smaller surface area, but on the other hand the cleaning surface impurities was higher for this cases. So a balance must be made between the gain that is achieved with the cleaning of impurities and the loss with the decreased in specific area. The best results were obtained for the temperature of 1450ºC/60min. The influence of annealing on the loss factor and ESR did not follow a well-defined pattern, because their values increased in some cases and decreased in others. The most interesting results due to heat treatment were with respect to capacitance, which showed an increase for all samples after treatment
Resumo:
This research is about the use of the coconut´s endocarp (nucifera linn) and the waste of derivatives of wood and furniture as raw material to technological use. In that sense, the lignocellulosic waste is used for manufacture of homogeneous wood sheet agglomerate (LHWS) and lignocellulosic load which take part of a polymeric composite with fiber glass E (GFRP-WC). In the manufacturing of the homogeneous wood sheet agglomerate (LHWS), it was used mamona´s resin as waste s agglutinating element. The plates were taken up in a hydraulic press engine, heated, with temperature control, where they were manufactured for different percentage of waste wood and coconuts nucífera linn. Physical tests were conducted to determine the absorption of water, density, damp grade (in two hours and twenty-four hours), swelling thickness (in two hours and twenty-four hours), and mechanical tests to evaluate the parallel tensile strength (internal stick) and bending and the static (steady) flexural. The physical test´s results indicate that the LHWS can be classified as bonded wood plate of high-density and with highly water resistant. In the mechanical tests it was possible to establish that LHWS presents different characteristics when submitted to uniaxial tensile and to the static (steady) flexural, since brittle and elasticity module had a variation according to the amount of dry endocarp used to manufacture each trace of LHWS. The GFRP-WC was industrially manufactured by a hand-lay-up process where the fiber glass E was used as reinforcement the lignocellulósic´s waste as load. The matrix was made with ortofitalic unsaturated polyester resin. Physical and mechanical tests were performed in presence of saturated humidity and dry. The results indicated good performance of the GFRP-WC, as traction as in flexion in three points. The presence of water influenced the modules obtained in the flexural and tensile but there were no significant alteration in the properties analyzed. As for the fracture, the analysis showed that the effects are more harmful in the presence of damp, under the action of loading tested, but despite this, the fracture was well defined starting in the external parts and spreading to the internal regions when one when it reaches the hybrid load
Resumo:
Novel cementing materials formulations containing flexible polymeric admixtures have been studied aiming at improving the mechanical behavior of oil well cement slurries submitted to steam injection. However, research activities in this sector are still under development. The steam injected directly into the well causes casing dilation, which after a reduction in temperature, tends to return to its original dimensions, resulting in crack formation and hydraulic isolation loss of the well, which will result in shortening of well life. In this scenario, the objective of the present study was to evaluate the mechanical behavior of Portland-based slurries containing SBR latex, applied in oil well cementing of wells submitted to steam injection. Were formulated slurries with densities of 1.797 g/cm3 (15.0 lb/Gal) and 1.869 g/cm3 (15.6 lb/Gal), containing admixtures with a latex concentration of 0; 66.88; 133.76; 200.64 and 267.52 L/m3 (0, 0.5, 1.0, 1.5 and 2.0 gpc). Tests including rheology, fluid loss control, thickening time, API compressive strength and splitting tensile strength, beyond steam injection simulation. Microstrutural characteristics of the slurries were also performed (XRD, TG, FTIR and SEM). The results showed that increasing the polymer concentration increased in the rheological properties and fluid loss, and a decrease in the elasticity modulus of the cement slurries. The results obtained showed that the slurries can be applied in cementing operations of oil wells submitted to steam injection.
Resumo:
The system built to characterize electrodes and, consequently, deposited fine films are constituted by a hollow cathode that works to discharges and low pressures (approximately 10-3 to 5 mbar), a source DC (0 to 1200 V), a cylindrical camera of closed borossilicato for flanges of stainless steel with an association of vacuum bombs mechanical and spread. In the upper flange it is connected the system of hollow cathode, which possesses an entrance of gas and two entrances for its refrigeration, the same is electrically isolated of the rest of the equipment and it is polarized negatively. In front of the system of hollow cathode there is a movable sample in stainless steel with possibility of moving in the horizontal and vertical. In the vertical, the sample can vary its distance between 0 and 70 mm and, in the horizontal, can leave completely from the front of the hollow cathode. The sample and also the cathode hollow are equipped with cromel-alumel termopares with simultaneous reading of the temperatures during the time of treatment. In this work copper electrodes, bronze, titanium, iron, stainless steel, powder of titanium, powder of titanium and silício, glass and ceramic were used. The electrodes were investigated relating their geometry change and behavior of the plasma of the cavity of hollow cathode and channel of the gas. As the cavity of hollow cathode, the analyzed aspects were the diameter and depth. With the channel of the gas, we verified the diameter. In the two situations, we investigated parameters as flow of the gas, pressure, current and applied tension in the electrode, temperature, loss of mass of the electrode with relationship at the time of use. The flow of gas investigated in the electrodes it was fastened in a work strip from 15 to 6 sccm, the constant pressure of work was among 2.7 to 8 x 10-2 mbar. The applied current was among a strip of work from 0,8 to 0,4 A, and their respective tensions were in a strip from 400 to 220 V. Fixing the value of the current, it was possible to lift the curve of the behavior of the tension with the time of use. That curves esteem in that time of use of the electrode to its efficiency is maximum. The temperatures of the electrodes were in the dependence of that curves showing a maximum temperature when the tension was maximum, yet the measured temperatures in the samples showed to be sensitive the variation of the temperature in the electrodes. An accompaniment of the loss of mass of the electrode relating to its time of use showed that the electrodes that appeared the spherical cavities lost more mass in comparison with the electrodes in that didn't appear. That phenomenon is only seen for pressures of 10-2 mbar, in these conditions a plasma column is formed inside of the channel of the gas and in certain points it is concentrated in form of spheres. Those spherical cavities develop inside of the channel of the gas spreading during the whole extension of the channel of the gas. The used electrodes were cut after they could not be more used, however among those electrodes, films that were deposited in alternate times and the electrodes that were used to deposit films in same times, those films were deposited in the glass substrata, alumina, stainless steel 420, stainless steel 316, silício and steel M2. As the eletros used to deposit films in alternate time as the ones that they were used to deposit in same times, the behavior of the thickness of the film obeyed the curve of the tension with relationship the time of use of the electrode, that is, when the tension was maximum, the thickness of the film was also maximum and when the tension was minimum, the thickness was minimum and in the case where the value of the tension was constant, the thickness of the film tends to be constant. The fine films that were produced they had applications with nano stick, bio-compatibility, cellular growth, inhibition of bacterias, cut tool, metallic leagues, brasagem, pineapple fiber and ornamental. In those films it was investigated the thickness, the adherence and the uniformity characterized by sweeping electronic microscopy. Another technique developed to assist the production and characterization of the films produced in that work was the caloteste. It uses a sphere and abrasive to mark the sample with a cap impression, with that cap form it is possible to calculate the thickness of the film. Through the time of life of the cathode, it was possible to evaluate the rate of waste of its material for the different work conditions. Values of waste rate up to 3,2 x 10-6 g/s were verified. For a distance of the substratum of 11 mm, the deposited film was limited to a circular area of 22 mm diameter mm for high pressures and a circular area of 75 mm for pressure strip. The obtained films presented thickness around 2,1 µm, showing that the discharge of arch of hollow cathode in argon obeys a curve characteristic of the tension with the time of life of the eletrodo. The deposition rate obtained in this system it is of approximately 0,18 µm/min
Resumo:
In this paper we developed a prototype for dynamic and quantitative analysis of the hardness of metal surfaces by penetration tests. It consists of a micro-indenter which is driven by a gear system driven by three-rectified. The sample to be tested is placed on a table that contains a load cell that measures the deformation in the sample during the penetration of micro-indenter. With this prototype it is possible to measure the elastic deformation of the material obtained by calculating the depth of penetration in the sample from the difference of turns between the start of load application to the application of the load test and return the indenter until the complete termination of load application. To determine the hardness was used to measure the depth of plastic deformation. We used 7 types of steel trade to test the apparatus. There was a dispersion of less than 10% for five measurements made on each sample and a good agreement with the values of firmness provided by the manufacturers.
Resumo:
Microalloyed steels constitute a specific class of steel with low amount of carbon and microalloying elements such as Vanadium (V), Niobium (Nb) and Titanium (Ti). The development and application of microalloyed steels and steels in general are limited to the handling of powders with particles of submicron or nanometer dimensions. Therefore, this work presents an alternative in order to construction of microalloyed steels utilizing the deposition by magnetron sputtering technique as a microalloying element addiction in which Ti nanoparticles are dispersed in an iron matrix. The advantage of that technique in relation to the conventional metallurgical processes is the possibility of uniformly disperse the microalloying elements in the iron matrix. It was carried out deposition of Ti onto Fe powder in high CH4, H2, Ar plasma atmosphere, with two deposition times. After the deposition, the iron powder with nanoparticles of Ti dispersed distributed, were compacted and sintered at 1120 ° C in resistive furnace. Characterization techniques utilized in the samples of powder before and after deposition of Ti were Granulometry, Scanning Electron Microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (DRX). In the case of sintered samples, it was carried out characterization by SEM and Vickers Microhardness assays. The results show which the deposition technique by magnetron sputtering is practicable in the dispersion of particles in iron matrix. The EDX microanalysis detected higher percentages of Ti when the deposition were carried out with the inert gas and when the deposition process was carried out with reactive gas. The presence of titanium in iron matrix was also evidenced by the results of X-ray diffraction peaks that showed shifts in the network matrix. Given these results it can be said that the technique of magnetron sputtering deposition is feasible in the dispersion of nanoparticles of iron matrix in Ti.
Resumo:
This work addresses the production of lightweight concrete building elements, such as plates, prefabricated slabs for pre-molded and panels of fencing, presenting a singular concrete: the Lightweight Concrete, with special properties such low density and good strength, by means of the joint use of industrial waste of thermosetting unsaturated polyesters and biodegradable foaming agent, named Polymeric Lightweight Concrete. This study covered various features of the materials used in the composition of the Polymeric Lightweight Concrete, using a planning of factorial design 23, aiming at studying of the strength, production, dosage processes, characterization of mechanical properties and microstructural analysis of the transition zone between the light artificial aggregate and the matrix of cement. The results of the mechanical strength tests were analyzed using a computational statistics tool (Statistica software) to understand the behavior and obtain the ideal quantity of each material used in the formula of the Polymeric Lightweight Concrete. The definition of the ideal formula has the purpose of obtaining a material with the lowest possible dry density and resistance to compression in accordance with NBR 12.646/92 (≥ 2.5 MPa after 28 days). In the microstructural characterization by scanning electron microscopy it was observed an influence of the materials in the process of cement hydration, showing good interaction between the wrinkled face of the residue of unsaturated polyesters thermosetting and putty and, consequently, the final strength. The attaining of an ideal formula, given the Brazilian standards, the experimental results obtained in the characterization and comparison of these results with conventional materials, confirmed that the developed Polymeric Lightweight Concrete is suitable for the production of building elements that are advantageous for construction
Resumo:
Titanium nitride films were grown on glass using the Cathodic Cage Plasma Deposition technique in order to verify the influence of process parameters in optical and structural properties of the films. The plasma atmosphere used was a mixture of Ar, N2 and H2, setting the Ar and N2 gas flows at 4 and 3 sccm, respectively and H2 gas flow varied from 0, 1 to 2 sccm. The deposition process was monitored by Optical Emission Spectroscopy (OES) to investigate the influence of the active species in plasma. It was observed that increasing the H2 gas flow into the plasma the luminescent intensities associated to the species changed. In this case, the luminescence of N2 (391,4nm) species was not proportional to the increasing of the H2 gas into the reactor. Other parameters investigated were diameter and number of holes in the cage. The analysis by Grazing Incidence X-Ray Diffraction (GIXRD) confirmed that the obtained films are composed by TiN and they may have variations in the nitrogen amount into the crystal and in the crystallite size. The optical microscopy images provided information about the homogeneity of the films. The atomic force microscopy (AFM) results revealed some microstructural characteristics and surface roughness. The thickness was measured by ellipsometry. The optical properties such as transmittance and reflectance (they were measured by spectrophotometry) are very sensitive to changes in the crystal lattice of the material, chemical composition and film thicknesses. Therefore, such properties are appropriate tools for verification of this process control. In general, films obtained at 0 sccm of H2 gas flow present a higher transmittance. It can be attributed to the smaller crystalline size due to a higher amount of nitrogen in the TiN lattice. The films obtained at 1 and 2 sccm of H2 gas flow have a golden appearance and XRD pattern showed peaks characteristics of TiN with higher intensity and smaller FWHM (Full Width at Half Maximum) parameter. It suggests that the hydrogen presence in the plasma makes the films more stoichiometric and becomes it more crystalline. It was observed that with higher number of holes in the lid of the cage, close to the region between the lid and the sample and the smaller diameter of the hole, the deposited film is thicker, which is justified by the most probability of plasma species reach effectively the sample and it promotes the growth of the film
Resumo:
Biodiesel is a fuel obtained from vegetable oils, such as soy, castorbean, among others. The monoester of fatty acid of these oils have chains with mono, di and tri double connections. The presence of these insaturations are susceptible to oxidization. Antioxidants are substances able to prevent oxidization from oils, fats, fat foods, as well as esters of Alquila( biodiesel). The objective of this work is to summarize a new antioxidant from the Cashew Nut Shell Liquid (CNSL) using the electrolysis technique. A current of 2 amperes was used in a single cell of only one group and two eletrodos of stainless steel 304 in a solution of methanol, together with the eletrolits: acetic acid, sodium chloride and sodium hydroxide, for two hours of agitation. The electrolysis products are characterized by the techniques of cromatography in a thin layer, spectroscopy of infrared and gravimetric analysis. The material was submitted to tests of oxidative stability made by the techniques of spectropy of impendancy and Rancimat (EN 14112). The analyses of characterization suggest that the polimerization of the electrolytic material ocurred. The application results of these materials as antioxidants of soy biodiesel showed that the order of the oxidative stability was obtained by both techniques used
Resumo:
Interstitial compounds of titanium have been mainly studied due to the large range of properties acquired when C, N, O and H atoms are added. In this work, surfaces of TiCxNy were produced by thermochemical treatments assisted by plasma with different proportions of Ar + N2 + CH4 gas mixture. The Ar gas flow was fixed in 4 sccm, varying only N2 and CH4 gas flows. During the thermochemical treatment, the plasma was monitored by Optical Emission Spectroscopy (OES) for the investigation of the influence of active species. After treatments, C and N concentration profile, crystalline and amorphous phases were analyzed by Nuclear Reaction (NRA). Besides tribomechanical properties of the Ti surface were studied through the nanohardness measurements and friction coefficient determination. The worn areas were evaluated by profilometry and Scanning Electronic Microscope (SEM) in order to verify the wear mechanism present in each material. It has been seen which the properties like nanohardness and friction coefficient have strong relation with luminous intensity of species of the plasma, suggesting a using of this characteristic as a parameter of process
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This work reports the influence of the poly (ethylene terephthalate) textile and films surface modification by plasmas of O2 and mixtures (N2 + O2), on their physical and chemical properties. The plasma surface polymeric modification has been used for many researchs, because it does not affect the environment with toxic agents, the alterations remains only at nanometric layers and this technique shows expressive results. Then, due to its good acceptance, the treatment was carried out in a vacuum chamber. Some parameters remained constant during all treatment, such as: Voltage 470 V; Pressure 1,250 Mbar; Current: 0, 10 A and gas flow: 10 cm3/min, using oxygen plasma alternating the treatment time 10 to 60 min with an increase of 10 min to each subsequent treatment. Also, the samples were treated with a gas mixture (nitrogen + oxygen) which was varied only the gas composition from 0 to 100% leaving the treatment time remaining constant to all treatment (10 min). The plasma treatment was characterized in-situ with Optics Emission Spectroscopy (OES), and the samples was characterized by contact angle, surface tension, Through Capillary tests, Raman spectroscopy, Infrared attenuated total reflection (IR-ATR) and atomic force microscopy, scanning electronic Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The results showed that oxygen treated fabrics presented high wettability, due to the hydrophilic groups incorporation onto the surface formed through spputering of carbon atoms. For the nitrogen atmosphere, there is the a film deposition of amine groups. Treatment with small oxygen concentration in the mixture with nitrogen has a higher spputered species of the samples
Resumo:
Metal substrates were coated by thermal spraying plasma torch, they were positioned at a distance of 4 and 5 cm from the nozzle exit of the plasma jet. The starting materials were used for deposition of tantalum oxide powder and aluminium. These two materials were mixed and ground into high-energy mill, then immersed in the torch for the production of alumina coating infused with particles of tantalum with nano and micrometric size. The spraying equipment used is a plasma torch arc not transferred, which operating in the range of 250 A and 80 V, was able to produce enough heat to ignite aluminothermic between Ta2O5 and aluminum. Upon reaching the plasma jet, the mixing powders react with the heat of the blaze, which provides sufficient energy for melting aluminum particles. This energy is transferred through mechanisms of self-propagating to the oxide, beginning a reduction reaction, which then hits on the surface of the substrate and forms a coating on which a composite is formed by a junction metal - ceramic (Ta +Al2O3). The phases and quantification of each were obtained respectively by X-ray diffraction and the Rietveld method. Morphology by scanning electron microscopy and chemical analysis by energy dispersive spectroscopy EDS. It was also performed measurements of the substrate roughness, Vickers microhardness measurements in sprays and determination of the electron temperature of the plasma jet by optical emission spectroscopy EEO. The results confirmed the expectation generated around the end product of spraying the mixture Ta2O5 + Al, both in the formation of nano-sized particles and in their final form. The electron excitation temperature was consistent with the purpose of work, in addition, the thermodynamic temperature was efficient for the reduction process of Ta2O5. The electron excitation temperature showed values of 3000, 4500 and 8000 K for flows10, 20 and 30 l / min respectively, these values were taken at the nozzle exit of the plasma jet. The thermodynamic temperature around 1200 ° C, was effective in the reduction process of Ta2O5