Resumo em Inglês:

The aim of this work is to evaluate the welding residual stress profile in ASTM A106 Gr. B steel pipes with 4" diameter and to correlate this profile with the microstructure and hardness of the joint. The results showed that the residual stresses are more uniform for a lower welding heat input. Higher welding heat input causes not only a non-uniformity of the stress profile but also promotes the maximum stress as high as the yield strength. The microstructure was composed of ferrite, perlite and possibly bainite; the presence of martensite was not verified. The hardness results indicated that none of the welding parameters used produced levels of hardness greater than 249 HV. Such a result is of fundamental importance because it suggests that low hardness does not necessarily mean low residual stress levels.

Resumo em Inglês:

In the modern automotive industry, the maintenance of the vehicle during its life cycle is increasing in importance due to both economical and environmental considerations. A new frontier is the reparation of large parts, originally made by fusion, by the addition of material. The standard technique in the field is the use of TIG welding, but in the last few years Cold Dynamic Gas Spray (CDGS) has started to show many promises in supplanting TIG repairs. The main advantage of CDGS is the absence of thermal stresses in the repaired zone with the elimination of thermal distension treatment of the part. In this paper we study the use of CDGS to repair wear damage on a commercial aluminium engine block in comparison with the standard repair procedure with TIG. The result obtained shows that CDGS is an effective technology for industrial-level repair.

Resumo em Inglês:

Layered or fibrous clay minerals are used as adsorbents because they have good performance to remove inorganic and organic species. In this work, a Brazilian fibrous clay mineral was applied to remove Remazol Yellow GR industrial dye from simple and binary systems; this was performed in the presence of lead in the latter case. The adsorption efficiency was investigated under various conditions of pH, time, temperature and dye concentration. The experimental data were fitted to the kinetic pseudo-first- and pseudo-second-order models, and the isotherms were fitted to the Langmuir and Freundlich models. The maximum adsorption capacity was 20.08 mg g-1 at pH 2, 240 minutes and 298 K, and these data were better fit by the kinetic pseudo-second-order model. The equilibrium study was fitted to the Langmuir model at 298 K and Freundlich for other temperatures and binary systems. The dye sorption in the presence of lead was decreased to 15 mg g-1. Therefore, palygorskite behaved as a promising solid for treating effluents.

Resumo em Inglês:

Super duplex stainless steels (SDSS) have high corrosion resistance because of their high contents of chromium, nickel, molybdenum and nitrogen but low wear resistance. To improve the wear resistance of these steels without affecting their corrosion resistance, samples of SDSS were treated by plasma ion nitriding at temperatures ranging from 350 °C to 570 °C for two hours. This thermochemical treatment resulted in the formation of different types of nitrides that affected the microhardness, the microwear behaviour and the corrosion resistance of the metal surface. The microwear resistance decreased at 400 °C because different nitrides formed on the surface, thereby increasing the hardness and volume wear resistance of the steel. The test results showed that the alloys that were nitrided at 400 °C and 450 °C exhibited the highest corrosion resistance to a solution medium containing chloride ions.

Resumo em Inglês:

Hot compression tests of as-cast Ti-6Al-2Zr-1Mo-1V alloy in a wide temperature range of 1073-1323 K and strain rate range of 0.01-10 s-1 were conducted by a servo-hydraulic and computer-controlled Gleeble-1500 machine. The hot flow behaviors of Ti-6Al-2Zr-1Mo-1V alloy show highly non-linear relationships with strain, strain rate and temperature. In order to accurately and effectively characterize the complex flow behaviors, support vector regression (SVR) which is a machine learning method was combined with Genetic Algorithm (GA) to characterize the flow behaviors, namely, the GA-SVR. The study abilities, generation abilities, and modeling efficiencies of the improved Arrhenius-type constitutive model, ANN, and GA-SVR for flow behaviors of as-cast Ti-6Al-2Zr-1Mo-1V alloy were detailedly compared. Comparison results show that the study ability of the GA-SVR is as strong as the ANN. The generation abilities and modeling efficiencies of these models were shown as follows in ascending order: the improved Arrhenius-type constitutive model < ANN < GA-SVR. Based on the established GA-SVR, the continuously three-dimensional relationships among flow stress, temperature, strain, and strain rate were constructed, which improve the simulation accuracy and related research fields where stress-strain data play important roles.

Resumo em Inglês:

Created in the 1940s, the splice finger-joint type for wood has now been more used to compose structural materials wood base as Glued Laminated Timber (Glulam) and Cross Laminated Timber (CLT). The main advantage of this amendment is to provide a simple and economical way to join timber parts on segments. This study evaluated by means of tensile tests the capacity of this type of joint (structural dimension of 21mm) to bond together Lyptus® wood beams (a Eucalyptus grandis and Eucalyptus urophyla hybrid) using Jowat polyurethane glue (Model 680.20) as compared to similar seamless beams. The results indicate that the seamless beams are 47.72% more resistant to traction (in characteristic values) than those with finger joints. However, to form structural elements where there is redundancy overlapping parts, such as Glulam and CLT, the values obtained can be considered satisfactory. Also noted is that denser samples have better traction results due to better bonding of the densest parts. The use of finger-joint and polyurethane adhesive o bond hybrid eucalyptus, although more brittle than wood without seams, enable the use of shorter wood sections for the composition of major structural elements, optimizing better forest material.

Resumo em Inglês:

The behavior of roasted coffee extract and its isolated high molecular weight fraction have been investigated as carbon steel corrosion inhibitors in HCl solution by weight loss measurements, potentiodynamic polarization curves, electrochemical impedance and scanning electron microscopy analysis. All results showed that the high molecular weight fraction, rich in melanoidins, present an important role in the inhibitory action of the roasted coffee extract in the acid corrosion of carbon steel.

Resumo em Inglês:

This work has focused on the electrical and microstructural properties of Nb2O5-doped SnO2-MnO2 ceramics. The pellets were prepared by solid-state reaction method according to the system (99.5-x) SnO2 - 0.5 MnO2 - x Nb2O5, on the following molar ratio x = 0.05; 0.10; 0.15; 0.20 and 0.25. Scanning electron microscopy and electrical measurements (ac and dc) were used to study the materials properties. The results showed that the increase of Nb2O5 content in the SnO2-MnO2 matrix has led to an increase in the varistor properties. A detailed study of the electrical properties of materials was conducted using impedance spectroscopy and the results indicated that Nb2O5 has a tendency to form an electron trapping level near the conduction band. In order to explain these findings, a parallel equivalent circuit model was used to simulate the values of the grain boundary resistance. A close relationship was found between the value of the nonlinear coefficient and the grain boundary resistance for the studied varistors, where both values increased with increasing the amount of Nb2O5, which is important for practical applications.

Resumo em Inglês:

In this work, an attempt has been made to fabricate hybrid Cu-SiC-Zn composites by friction stir processing technique. Through this investigation the different number of passes was applied to assess the effect of pass adding on the mechanical, microstructural and dislocation density behavior of the specimens. Formation of the intermetallic phases between the copper matrix and Zn particles was discovered through the processed specimens. According to the obtained results, the higher passes led to obtain more uniform dispersion of the SiC particles and intermetallic phases. This higher level of particles and intermetallic phases' distribution causes remarkable reduction of grain sizes through the composites. Dislocation density for the processed specimens was determined by using the hardness measurement method. The calculated values for the dislocation densities showed that presence of SiC particles and intermetallic phases could rise up the dislocation values. Measured microhardness values for the composites exhibit that they enhanced rather than base metal and these results were confirmed by dislocation densities values of the specimens.

Resumo em Inglês:

The Fe-rich alloys of Fe90-xSi5B5Mx (M= Cr or Mo; x=1, 2) are synthesized in the present study. The as-spun structure mainly consists of bcc phase plus a minor amount of metastable phase (Fe3B and/or Fe23B6). Comparing with the base alloy Fe90Si5B5, the corrosion resistance is improved significantly due to the formation of the passive film. Saturation magnetic flux density reaches 1.9 T for the melt-spun alloys Fe89Mo1Si5B5. The alloys present a nearly constant high permeability in a rather high magnetic field up to coercive field which can be used as a new kind of sensor material with good fundamental properties and low cost.

Resumo em Inglês:

An investigation in the present research was made to fabricate and evaluate the microstructure and mechanical properties of metal matrix composites developed using cryogenically cooled copper chills, consisting of ASTM A 494 M grade nickel alloy matrix and garnet particles as the reinforcement. The particle's amount added ranges from 3 wt. % to 12 wt. % in steps of 3%. A stir casting process was used to fabricate the composite. The matrix alloy was melted in a casting furnace at around 1350˚C, the garnet particulates preheated to 600˚C, were introduced into the molten metal alloy. When pouring melt into mould, an arrangement was made at one end of the mould by placing copper chill blocks of varying thickness brazed with MS hallow block in which liquid nitrogen was circulated simultaneously for cryogenic effect. After solidification produced composite materials thus synthesized were examined for microstructural and mechanical properties as per ASTM standards.

Resumo em Inglês:

In this study, the relationship between structure and mechanical properties of aged PBT composite was investigated. Short glass fiber reinforced PBT composites were subjected to aging tests in environments typically found in hermetic compressors. Diffusion kinetics were addressed by a periodic control of samples weight, and samples aged in oil presented mass variation of 1.2-1.6%, depending on test temperature. Most diffusion curves followed Fickian behavior, and the diffusion coefficient for each condition was obtained. Aging effect was investigated by 3-point bending tests, where samples aged at 180°C presented a significant reduction in all evaluated properties. Control environment induced minor variations, supposedly related to physical aging and increase in crystallinity. Imaging analyses through scanning electronic microscopy (SEM) technique allowed observation of the predominant fracture mechanism. Aged samples presented few or no localized plastic deformation at all, which is in accordance with the lower strain observed in mechanical tests. Differential scanning calorimetry (DSC) analyses proved degree of crystallinity increase for all aged samples, depending mainly on temperature of exposure. Infrared (FTIR) analysis proved the presence of oil absorbed in PBT chemical structure, and it was proposed a method for comparing degree of crystallinity, based on the absorbance bands ratio A0(1458 cm-1)/A0(956 cm-1).

Resumo em Inglês:

TiO2 nanoparticleshave been synthesized by the sol-gel method using titanium alkoxide and isopropanolas a precursor. The structural properties and chemical composition of the TiO2 nanoparticles were studied usingX-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy.The X-ray powder diffraction pattern confirms that the particles are mainly composed of the anatase phase with the preferential orientation along [101] direction.The physical parameters such as strain, stress and energy density were investigated from the Williamson- Hall (W-H) plot assuming a uniform deformation model (UDM), and uniform deformation energy density model (UDEDM). The W-H analysis shows an anisotropic nature of the strain in nanopowders. The scanning electron microscopy image shows clear TiO2 nanoparticles with particle sizes varying from 60 to 80nm. The results of mean particle size of TiO2 nanoparticles show an inter correlation with the W-H analysis and SEM results. Our X-ray photoelectron spectroscopy spectra show that nearly a complete amount of titanium has reacted to TiO2.

Resumo em Inglês:

The aim of this study was to prepare and characterize a hybrid layered material (organoclay) with a Na-montmorillonite and the triethylene glycol mono-n-decyl ether (C10E3) nonionic surfactant which forms a lamellar phase at room temperature. The synthesized organoclay was characterized by complementary techniques (Fourier transform infrared spectroscopy and X-ray diffraction). Experiments in conjunction with electron density analysis showed that a bilayer or membrane of C10E3 was intercalated within the interlayer space of a naturally exchanged Na-montmorillonite. The intercalation of a bilayer of C10E3 in a clay mineral offers new perspectives for the manufacturing of nanomaterials. While showing a hydrophobic surface and a large interlayer space value, the resulting organoclay preserves the compensating cations within the interlayer space allowing one to perform ion exchanges, making easier the intercalation of further organic molecules of important size with functional properties or for environmental purposes.

Resumo em Inglês:

The thermal decomposition of silicon carbide (SiC), with the subsequent formation of graphene, can be achieved by heating treatment. Several heating processes have been applied for this purpose by using SiC, either in form of powder particles or monocrystalline substrate. In this work, instead of using an expensive commercially available SiC wafer, a polycrystalline SiC substrate was obtained, based on powder metallurgy process, in order to explore the synthesis of graphene layers on its surface by using a CO2 laser beam as heating source. Different levels of energy density (fluence) were applied and Raman spectroscopy analyses demonstrated that graphene layers were formed on the polycrystalline SiC surface. The ratio of the integrated intensity of the D and G bands, and the crystallite size were calculated. The FWHM of the 2D band peaks are in excellent agreement with the range of values found in the literature. The samples irradiated with energy density of 138.4 J/cm2 presented lower concentration of defects and higher crystallite size, while the lowest FWHM was obtained for energy density of 188 J/cm2. The process occurred at room conditions and no gas flow was used. The results reveal a simple and cost-effective alternative for synthesis of graphene-based structures on SiC.

Resumo em Inglês:

Cd1-xZnxS thin films have been studied extensively as window layers for solar cell applications. However, a mismatch between the Cd1-xZnxS and copper-indium-gallium-selenide absorber layers increases with Zn film concentration, which reduces the device efficiency. In this work, Cd1-xZnxS thin films with low Zn concentrations were analyzed. The effect of the addition of different molar Zn concentrations to the reaction mixture on the growth mechanism of Cd1-xZnxS thin films and the influence of these mechanisms on structural, optical and morphological properties of the films has been studied. Cd1-xZnxS thin films were synthesized by chemical bath deposition using an ammonia-free alkaline solution. Microstructural analysis by X-ray diffraction showed that all deposited films grew with hexagonal structure and crystallite sizes decreased as the Zn concentration in the film increased. Optical measurements indicated a high optical transmission between 75% and 90% for wavelengths above the absorption edge. Band gap value increased from 2.48 eV to 2.62 eV, and the refractive index values for Cd1-xZnxS thin films decreased as the Zn increased. These changes in films and properties are related to a modification in growth mechanism of the Cd1-xZnxS thin films, with the influence of Zn(OH)2 formation being more important as Zn in solution increases.

Resumo em Inglês:

The influence of binders on the mechanical properties of chromite, self-reducing pellets, after subjecting to high temperatures, is analyzed in this paper. Bentonite, sodium silicate, and a combination of bentonite with carboxymethyl cellulose (CMC) were tested with different contents. All of the raw materials were characterized by chemical analysis and particle size distribution. The materials were pelletized (P1 to P7). All of the bounded green and dried pellets (P2 to P7) achieved the desired mechanical strengths, and none presented decrepitation. The best performance was obtained by the pellet P7 (4% sodium silicate as binder), with the green strength of 34 N/pellet, the dried strength of 50 N/pellet, and the strength was higher than 110 N/pellet after heat treatment at critical temperatures between 1173 and 1373 K. The unitary reduction reaction fraction was achieved after 10 minutes, at 1773 K.

Resumo em Inglês:

Star-shaped PbS nanomaterials are synthesized by a hydrothermal method. Morphology and structure of the PbS nanomaterials are analyzed by SEM, HRTEM and XRD. Gas-sensing properties of the as-prepared PbS sensor are also systematically investigated. The results show star-shaped PbS nanostructure consists of four symmetric arms in the same plane and demonstrate good crystallinity. With the increase of ethanol concentration, the sensitivity of the PbS sensor significantly increases and demonstrates an almost linear relationship at the optimal operating temperature of 400 ºC. Moreover, the fast response-recovery towards ethanol is also observed, which indicates its great potential on ethanol detection.

Resumo em Inglês:

Nanoparticles comprised of the poly(ethylene oxide)-b-poly (lactic acid) diblock copolymer (PEO-b-PLA) with and without the incorporation of lavender oil were prepared by nanoprecipitation. Diblock copolymers based on a fixed PEO block (5KDa) and two different PLA segments (4.5 or 10KDa) were used. The morphology, encapsulation efficiency, essential oil-polymer interaction and the release kinetics of the active agent in the nanoparticles, were evaluated. The hydrodynamic radius of the nanoparticles determined by light scattering was affected by the size of the poly(lactic acid) (PLA) block. The lavender essential oil encapsulation efficiency (at a concentration of 0.4 µL mL-1) determined by UV-VIS spectroscopy was in the range of 70-75%. The in vitro release suggests that the polymeric barrier is able to control the oil release.

Resumo em Inglês:

This paper looks into the influences of martensitic transformations on the cavitation-erosion (CE) damage initiation mechanism and pitting corrosion resistance of a lean austenitic stainless steel. The ε and α' martensites are prime sites of CE damage initiation for this steel, whereas grain boundaries are more favourable damage initiation sites for other similar steels. The profusion of ε and α' results in fast surface roughening during the CE process, which may cause a compromise in performance when this steel (or similar steels that have the same CE damage mechanism) is used for such applications as hydro-machinery or piping. ε and α' also detrimentally affect the pitting resistance of this steel and so they are expected to affect CE resistance adversely due to the synergism between CE and corrosion.

Resumo em Inglês:

Water pollution by organic compounds is one of the major challenges faced by industries that use dyeing processes. Thus, some methods were developed for degrading dyes in wastewaters, including heterogeneous photocatalysis by semiconductor oxides. However, these oxides have limited photocatalytic activity due to the fast recombination of photogenerated electron-hole pairs. The aim of this study is the use of a carbon nanotube (CNT) and TiO2-ZnO oxide junction from modified sol-gel method to promote the degradation of organic dye through the photocatalytic activity of these nanocomposites. TiO2-ZnO/CNT nanocomposites were studied by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) and photocatalytic decomposition of organic dyes. The results of photocatalysis show up to 60% the efficiency of the samples in the removal of dye.

Resumo em Inglês:

BaZr0.1Ti0.9O3 ceramics of perovskite structure are prepared by solid state reaction method with addition of x Yb2O3 (x= 0.0, 0.1, 0.3, 0.5 and 0.7 mol%), respectively, and their dielectric properties are investigated. Room temperature X-ray diffraction study suggested that the compositions have a single phase with a perovskite structure. A small decrease in the grain size is observed with an increase in the Yb content. The bulk density increased with increasing the Yb content for the samples sintered at 1250 0C, and the bulk densities show the maximal value for the samples sintered at 1280 0C, 1300 0C and 1330 0C. The dielectric constant can reach to 4500 or more for the sample sintered at 1300 0C, and the variation of dielectric loss with temperature is more stable for Yb2O3-doped BZT10 ceramics, which proves that Yb2O3 doping has a great influence on the dielectric properties in BZT10 ceramics. With the increase of Yb2O3 content, Tc rises at first, and when x exceeds 0.1 mol%, Tc shifts towards to lower temperature with the Yb2O3 concentration increasing.

Resumo em Inglês:

Powders Nb2 O5 were prepared by two different synthesis method, Sol-Gel and polymeric precursors (Pechini). In the Pechini method before adding the citric acid in the process, four different solutions were used to get the samples. For Sol-gel method, two different processes were also used in obtaining powders. The precursor was completely solubilized in ethanol and then hydrolyzed with ammonia and water. The calcination of the samples was between 500 and 750°C. The resulting powders were characterized by Scanning Electron Microscopy (SEM), Brunauer, Emmett and Teller (BET) surface area measurements, UV-visible and Raman spectroscopy. The formation of T−Nb2 O5 orthorhombic took place upon calcination at 7500C. Crystallite sizes were determined using the Scherrer method which resulted in an uniformed size of about 25 − 65nm. Ultraviolet-Visible diffuse reflectance spectroscopy indicated a variation in the optical band gap values (3.32-3.40 eV) in crystal growth process. The Raman vibrational modes indicate the presence of the orthorhombic phase of the material.

Resumo em Inglês:

Spherical calcium phosphate cement carriers were synthesized by water/oil emulsion. A 23 factorial design was employed in order to optimize the size and form of the microspheres. Stirring speed, liquid-to-powder ratio and cement paste-to-oil ratio were varied in two different levels and the response variable was the microsphere's sphericity. The results showed that cement's setting reaction was responsible for stabilizing the microspheres within the oil phase resulting in a low crystalline hydroxyapatite. The sizes varied from 6.29 to 64.23 µm. From the factors studied, the stirring velocity and the interaction between the L/P ratio with the P/O ratio are the ones that are more effective in controlling microspheres' sphericity. The results suggest that the methodology studied may provide microspheres with appropriate properties to deliver cells and/or drugs without inducing inflammatory reactions.

Resumo em Inglês:

SnO-coated FeNi alloy nanocapsules have been synthesized by an arc-discharge method. High-resolution transmission electron microscopy and x-ray photoelectron spectroscopy analysis show that the nanocapsules have a shell/core structure with FeNi alloy nanoparticles as the core and amorphous SnO as the shell. Dielectric relaxation of SnO shell and the interfacial relaxation between SnO shell and FeNi core lead to the dual nonlinear dielectric resonance. The natural resonance in the SnO-coated FeNi nanocapsules shifts to 14.0 GHz. Reflection loss (RL) reaches -46.1 dB at 14.8 GHz for a matching thickness of 1.95 mm, while it exceeds-20 dB over the 13.6 -16.7 GHz range and it exceeds -10 dB in the whole Ku-band (12.4-18 GHz). In addition, the optimal RL values at 5.0-7.6 GHz with the absorbing thickness of 3.4-5.0 mm just exhibit a slight fluctuation.

Resumo em Inglês:

Mesoporous Fe2O3-supported ZSM-5 zeolites were prepared by carbon-templating and subsequently evaluated as photo-Fenton catalysts to degrade a dye used as a model heavy organic pollutant. The synthesis procedure of the mesoporous ZSM-5 zeolites was performed employing a nucleating gel and carbon particles as mesopores template. Thereafter, the precursor salt of the iron oxide (Fe2O3) was impregnated and then calcined to obtain the final catalyst. For comparison purposes, a conventional Fe2O3-supported ZSM-5 zeolite was also prepared. The results showed that the amount of intracrystalline mesopores formed in the ZSM-5 crystals was influenced by the amount of carbon added into the synthesis mixture. In comparison to the conventional prepared catalyst, the mesoporous Fe2O3/ZSM-5 ones showed an improved performance in the degradation of the target organic pollutant by the photo-Fenton reaction, which was attributed to the improvement of their textural properties as consequence of the mesopores generation.

Resumo em Inglês:

In this work a colloidal approach to synthesize water-soluble CdSe quantum dots (QDs) bearing a surface ligand, such as thioglycolic acid (TGA), 3-mercaptopropionic acid (MPA), glutathione (GSH), or thioglycerol (TGH) was applied. The synthesized material was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV-visible spectroscopy (UV-Vis), and fluorescence spectroscopy (PL). Additionally, a comparative study of the optical properties of different CdSe QDs was performed, demonstrating how the surface ligand affected crystal growth. The particles sizes were calculated from a polynomial function that correlates the particle size with the maximum fluorescence position. Curve resolution methods (EFA and MCR-ALS) were employed to decompose a series of fluorescence spectra to investigate the CdSe QDs size distribution and determine the number of fraction with different particle size. The results for the MPA-capped CdSe sample showed only two main fraction with different particle sizes with maximum emission at 642 and 686 nm. The calculated diameters from these maximum emission were, respectively, 2.74 and 3.05 nm.

Resumo em Inglês:

KNN thin films with diverse yttrium concentration (mol % = 0, 0.1, 0.3, 0.5, 0.7 and 0.9) were fabricated using sol-gel spin coating technique. Doped KNN revealed that Y3+ was successfully doped into the ABO3 perovskite lattice without changing the phase formation of KNN. The thickness of the deposited layer of KNN produced with increasing dopant concentration was determined to be 200 nm with dense and well-defined grains. Afterwards, the vibrational bonding and conductivity of KNN films with diverse yttrium concentration were identified according to the charge compensation mechanism. At high dopant concentration of > 0.5 mol %, O-Nb-O bonding was asymmetric and became distorted due to B-site occupancy by yttrium dopant. Further investigation revealed that charge compensation mechanism was shifted by increasing doping concentration. As a result, yttrium-doped KNN became semi-conductive at low yttrium concentration. Meanwhile, at high concentration, yttrium-doped KNN became an insulator and underwent ionic compensation.

Resumo em Inglês:

The crystal structure of the chalcogenide compounds CuCo2InTe4 and CuNi2InTe4, two new members of the I-II2-III-VI4 family, were characterized by Rietveld refinement using X-ray powder diffraction data. Both materials crystallize in the tetragonal space group I4 2m (No. 121), Z = 2, with a stannite-type structure, with the binaries CoTe and NiTe as secondary phases.

Resumo em Inglês:

The aim of this study was to evaluate the potential use of sisal and coir fibers in combination with Eucalyptus particles for the production of particleboard. The particleboards were produced in three layers. The first and third layers (face) were made with small Eucalyptus particles. The second layer (core) was made with big Eucalyptus particles in combination with coir or sisal fibers. The particleboards were prepared with the substitution on Eucalyptus wood for sisal and coir fibers in the particleboards core, in doses of 0, 10, and 20%, relative to the total mass of particles. The particleboards were characterized by mechanical, physical and thermal properties. The results were not satisfactory for particleboards with sisal. However, for coir particleboards the physical-mechanical properties were very similar to those particleboards produced only with Eucalyptus. This work demonstrates the potential use of the coir that is commonly disposed in landfills on the Brazilian beaches.

Resumo em Inglês:

This paper aims to study the influence of including wood sawdust and sodium silicate in the production process of calcined clay lightweight ceramics. In the production process first, a sample used by a company that produces ceramic products in Brazil was collected. The sample was analysed by techniques of liquidity (LL) and plasticity (LP) limits, particle size analysis, specific mass, X-ray diffraction (XRD) and X ray fluorescence spectrometry (XRF). From the clay, specimens of pure clay and mixtures with wood sawdust (10%, 20% and 30% by mass) and sodium silicate were produced and fired at a temperature of 900 ºC. These specimens were submitted to tests of water absorption, porosity, specific mass and compressive strength. Results of this research indicate that the incorporation of wood sawdust and sodium silicate in the ceramic paste specimens can be useful to make calcined clay lightweight ceramics with special characteristics (low values of water absorption and specific mass and high values of compressive strength), which could be used to produce calcined clay lightweight aggregates to be used in structural concrete.

Resumo em Inglês:

The mechanical properties and microstructure of aluminum matrix composites containing of zircon (10, 15 and 20 wt.%) as a reinforcement particles and cobalt additive (1, 1.5 and 2 wt.%) were investigated. The aluminum matrix composites were prepared by powder metallurgy technique and sintered in both conventional and microwave furnaces at temperatures higher than the melting point of aluminum. The results revealed that the density and mechanical strength of aluminum were increased by introducing zircon and cobalt particles. The maximum strength was obtained by adding 10 wt.% zircon sintered in microwave furnace at 950ºC. The phase analysis and scanning electron microscopy of sintered composites were examined and found some interesting data about intermetallic compounds.

Resumo em Inglês:

The hot deformation behaviours of Ti-6Al-4V-0.1Ru alloy were investigated by isothermal hot compression tests in the temperature range of 1023-1423 K and strain rate range of 0.01-10 s-1. The β transus was determined to be 1198 K by continuous heating method. The values of deformation activation energy Q at the strain of 0.3 were calculated to be 630.01 kJ/mol in dual-phase field and 331.75 kJ/mol in β-phase field. Moreover, the processing maps at the strain of 0.2, 0.4, 0.6 and 0.8 were developed based on dynamic materials model (DMM). To deeply understand the microstructure evolution mechanism during hot deformation processes and to verify the processing maps, the microstructures at different deformation conditions were observed. The stable microstructures (i.e. globularization, dynamic recovery (DRV) and β dynamic recrystallization (β-DRX)) and instable microstructures (i.e. lamellae kinking and flow localization) were obtained. To make it useful in the design of industrial hot working schedules for this material, a microstructural mechanism map was constructed on the basis of processing maps and microstructure observation. Deformation conditions in the vicinity of 1150 K & 0.01 s-1 where globularization occurs and in the vicinity of 1323 K & 0.01 s-1 where β-DRX occurs are recommended.

Resumo em Inglês:

In this work, the synthesis of zeolites using 1-butyl-3-methylimidazolium chloride [C4MI]Cl as a structure-directing agent was investigated. The organic cation shows effectiveness and selectivity for the syntheses of TON zeolites under different reaction conditions compared to the traditional structure-directing agent, 1,8-diaminooctane. The 1-butyl-3-methylimidazolium cation lead to highly crystalline materials and its role as OSDA in our synthesis conditions has been confirmed by characterization techniques. ICP-OES confirms the presence of Al in the samples and 27Al MAS NMR analysis indicated that aluminum atoms were incorporated in tetrahedral coordination. Scanning electron microscopy indicated that changing the crystallization condition (static or stirring), zeolites with different crystal size were obtained, which consequently affects the textural properties of the zeolites. Moreover, varying some synthesis parameters MFI zeolite can also be obtained.

Resumo em Inglês:

An investigation was carried out to determine the possibility of preparing coatings of synthetic zeolites on stainless steel from mixtures containing natural zeolite. Hydrothermal synthesis was applied and the coatings obtained were characterized by various techniques. It was observed that crystalline zeolite A coatings could be prepared from natural clinoptilolite, which provided the silica necessary for zeolite synthesis in the alkaline reaction mixture containing alumina. Zeolite coating formation was affected by synthesis conditions, such as temperature, time, alkalinity, and alumina content of the reaction mixture. The involvement of two simultaneous processes, namely, dissolution/transformation of clinoptilolite in the mixture and reaction on the substrate by the help of dissolved reagents, presents a new approach for zeolite coating preparation. This method may especially provide a means for more economical mass-scale production of zeolite coatings since the synthetic reagents may be replaced with much cheaper natural resources.