Resumo em Inglês:

Steelmaking slag (SS) is one of the largest generation waste in the integrated and semi-integrated plants, but it has application restrictions due to its high expansibility. To overcome these constraints, this research had as its main objective the reactions is kinetics parameters estimation that result in the expansion of SS using the Arrhenius global equation. It was obtained 12.5 kJ/mol for activation energy and 260.42% for the pre-exponential factor. It was also noted that the temperature significantly impacts the final expansion values, increasing them exponentially. Furthermore the time of expansion of the slag obey an asymptotic equation (Exp = a - b.ct) whose results presented initially having a large expansion velocity, which tends to zero at times very long when the material has stabilized.

Resumo em Inglês:

Ni-P-(Cu) composite coatings were applied on a St37 steel in an acidic bath of hypophosphite composite. The effect of the concentration of the Cu particles and pH of the solutionon the amount of Ni and P of the coatings, their morphology, and hardness of the coatings were explored. Some of the coated samples were also heat treated at 400ºC for 1 hour. The phases formed, the microstructure and the amount of the alloying elements of the coatings were analyzed by X-Ray powder diffraction (XRD), Scanning Electron Microscope (SEM) equiped with Energy Dispersive Spectroscopy (EDS). Results show that although adding Cu particles reduced the hardness of Ni-P coating (from 482.4 to 351.2 VH in 1 gr/lit Cu), within Ni-P-Cu composite coatings the hardness of Ni-P-Cu composite coating increased from 351.2 to 380.7 VH by increasing the Cu particles from 1 to 7 gr/lit. The structure of the coating was crystalline during the heat treatment making the coating harder. With increasing the pH of the solution from 4.5 to 7 and then to 9, the weight percent of P and the particle of Cu were reduced.

Resumo em Inglês:

Glycinium Phosphite (GlP) has been synthesized and characterized successfully. The fluorescence spectrum of the compound showed one broad peak at 282 nm. Linear absorption value was calculated by Optical Limiting method. Birefringence study was carried out and the birefringence of the crystal is found to be depending on the wavelength in the entire visible region. Third order nonlinear optical property of the crystal was carried out by Z-Scan technique and non linear refractive index and third order susceptibility was calculated. Thermal stability of the crystal was found using TG and DTA thermal analyzer and the results shows that the crystals have good thermal stability. The crystal was also analyzed by photo conductivity analyzer to determine the optical conductivity of the crystal.

Resumo em Inglês:

The purpose of this work is to determine the effective piezoelectric coefficient (d33) and the macro ferroelectric hysteresis behavior for the Ba0.9Ca0.1Ti0.9Zr0.1O3 (BCZT). The sample was prepared by the modified Pechini method and it was sintered at 1250 ºC for 5 h. The refinements of X-ray diffraction (XRD) patterns obtained by the Rietveld method suggest a slight degree of tetragonality (c/a = 1.0025) in the perovskite structure. High counting statistics was performed in the two-dimensional grazing incidence 2D-GIXRD characterization by using synchrotron radiation. These results and the Raman spectrum analysis support the XRD interpretation. The morphology reveals a non-homogeneous terrace-type shape with a grain size distribution centered at 13 microns. The switching spectroscopy piezo-response force microscopy was used to obtained the effective d33 = 142 pm/V. The soft ferroelectric hysteresis shows a coercive field Hc = 1.3 kV/cm with a saturation polarization Ps = 15.7 µC/cm2.

Resumo em Inglês:

In this study, CuO thin films were deposited on glass substrates at a wide range of temperatures from 450ºC to 550ºC with steps of 25ºC by chemical spray pyrolysis technique. Aiming to investigate the effect of annealing process, one of the resulting films was annealed at 450ºC for 3 hours under ambient air. Based on X-ray diffraction, all the resulting films are monoclinic with two prominent peaks at ~36º and ~39º. The crystallite size of the CuO film deposited at 450ºC was found to be the largest in comparison with the others. As the substrate temperature increased, a gradual change was observed for the CuO thin film surface morphology and in the case of annealed film, the grains and their boundaries became indistinguishable. The resistivity of the films was reduced by virtue of increasing the substrate temperature and also, both the mobility and carrier concentration of the annealed film were improved drastically after annealing. As expected, the CuO thin films absorption was considerable in the visible region and gradually declined after 800nm. The estimated band gap value of the CuO film deposited at 450ºC were fairly close to the optimum band gap for solar applications.

Resumo em Inglês:

The microstructure length-scales (dendritic and eutectic), morphologies and tensile properties of a ternary Sn-9wt.%Zn-2wt.%Cu alloy are compared with those of a binary eutectic Sn-9wt.%Zn alloy. The following experimental/analytical steps were performed: transient directional solidification experiments of the Sn-9wt.%Zn-2wt.%Cu alloy; measurements of secondary dendrite arm (λ2) and interphase spacing (λ); morphology of the eutectic α-Zn phase; determination of thermal parameters such as cooling rate (ṪL) and their evolutions during solidification; and, finally, interrelations of microstructure vs. tensile properties. The addition of 2wt.%Cu causes significant refinement of the eutectic structure. Hall-Petch type experimental expressions outlined the variations of strength and ductility with both λ2 and λ. Very fine Zn globules and needles forming the eutectic in the ternary alloy seems to cause a reversal on ductility behavior, as compared to the tendency observed for the binary Sn-9wt.%Zn alloy. Here, for the ternary Sn-9wt.%Zn-2wt.%Cu alloy ductility increases with decreasing interphase spacing.

Resumo em Inglês:

Humic acid was extracted and employed as a dispersant in an alumina suspension. The higher zeta potential for HA (-42 mV) was measured at pH 11 showing that an electrostatic repulsion might occur in the alumina/HA suspension. As a consequence of the long chain molecules of HA it was also expected a steric effect on deflocculation. The best dispersion conditions for the alumina suspension (28 vol%) were found with 0.016 wt% HA, close to the viscosity achieved with a commercial sodium polyacrylate. The rheological characterisation showed results beneficial for the slip casting process, such as slightly thixotropy and pseudoplastic behaviour. The excellent colloidal stability at pH 11 as evidenced through rheological and sedimentation tests was attributed to the polyelectrolyte nature of the HA. From deflocculated suspensions it was possible to obtain high density pieces by slip casting method.

Resumo em Inglês:

A first principles investigation at the pressure 7 GPa of the optical properties of RVO4 (R= Eu, Ho, Lu) orthovanadates in the framework of the density functional theory (DFT) using the linearized-augmented plane-wave method is reported in order to predict new optical materials for continuous-wave lasers. The electronic structure of all orthovanadates is studied in zircon-type structure. DFT+U (Hubbard parameter found to be 8eV) calculations predict an antiferromagnetic and nonmagnetic insulating ground states -at ambient conditions- for (EuVO4, HoVO4) and LuVO4, respectively. The results show that these vanadates can be good candidates for laser-host materials, and indicate the possibility of material design to optimize the laser-host materials. The rare-earth ion-doped crystals could enhance the laser performances and improve the isolation characteristic of the optical isolators.

Resumo em Inglês:

The radiopacity of CAC-based compositions containing additives (ZnO, Ag and Bi2O3) was evaluated by optical density measurements, cold crushing strength, apparent porosity, pore size distribution, in vitro apatite-formation ability (bioactivity) and cell viability. The bioactivity was assessed via pH and calcium concentration measurements in simulated body fluid (SBF) for samples previously treated or not with sodium silicate (SS) solution. The surface of the samples after treatment was analyzed by scanning electron microscopy, energy dispersive X-ray analysis and confocal Raman spectroscopy. Cell viability was evaluated by MTT and alkaline phosphatase (ALP) activity. Radiopacity results confirmed that compositions containing ZnO-Ag (25:1 wt%) and ZnO-Bi2O3 (15:10 wt%) presented suitable values of radiopacity (> 3 mmAl). The identification of calcium and mainly phosphorus by EDX, highlighted the generation of an apatite-like layer on the compositions' surface after immersion in SBF or SBF/SS. CAC-blend containing 25 wt% ZnO, ZnO-Ag and ZnO-Bi2O3 presented slightly lower cell viability compared to the positive control.

Resumo em Inglês:

This work proposes a three-dimensional methodology to characterize porosity in iron ore pellets by X-ray Microtomography (microCT). An image analysis routine was developed to discriminate and quantify open/closed porosity. The results were compared to the traditional techniques of mercury intrusion porosimetry (MIP) and optical microscopy (OM). As expected, the porosity values obtained from microCT were much lower than those from MIP and OM, due to the lower spatial resolution of the proposed technique. However, the resolution can be optimized to detect the main peak of the pore size distribution, close to 10 µm. MicroCT was also able to discriminate between open and closed porosities, and revealed the volumetric spatial distribution of the pores, parameters that cannot be obtained from the other techniques. Thus, microCT may become a new standard for this analysis, eliminating the need for specimen preparation (as for OM) or the use of toxic materials (as in MIP).

Resumo em Inglês:

Manganese selenide (MnSe) crystalline thin film was produced with chemical bath deposition on substrates (commercial glass). Transmittance, absorption, optical band gap and refractive index were investigated by UV/VIS spectrum. The hexagonal form was observed in the structural properties in XRD. The structural and optical properties of the MnSe thin films were analyzed at different pHs. SEM and EDX analysis were used for the surface analysis in the films. The films had the best crystalline at pH: 9. At pHs of 11 and 10 the MnSeO4 structure was observed. The films with the lowest film thickness were found in baths prepared with pH: 11. The highest refractive index was observed in films produced with a pH of 10 at a film density of 1.96. The grain size of MnSe thin films has a higher value at pH: 9.

Resumo em Inglês:

A systematic study about synthesis of In1-xSnxO2 (ITO) nanostructured crystals by microwave-assisted solvothermal method is reported. Different solutions using InCl3.4H2O and SnCl4.5H2O precursors in ethylene glycol solvent were prepared in distinct pHs (acid and basic ones). The syntheses were performed at 200 ºC using a heating rate of 50 ºC min-1 and soaking time of 30 minutes. All the synthesized powders were characterized by X-ray Diffraction (XRD) and Rietveld refinement to study the phase evolution as a function of pH. The materials synthesized in the pH ranging between 11.5 and 11.9 were further studied by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) techniques. As ITO materials have many practical applications due to their transparency in the visible spectrum, UV-Vis spectroscopy analysis was performed to obtain the optical band gap and the respective optical window.

Resumo em Inglês:

Nickel ferrite (NiFe2O4) nanoparticles were synthesized using co-precipitation method. The X-ray diffraction (XRD) pattern was used to determine the structure of NiFe2O4 nanoparticles. The presence of NiFe2O4 nanoparticles was confirmed by the FT-IR spectrum. The details of the surface morphology of NiFe2O4 nanoparticles were obtained by Scanning Electron Microscopic analysis. The particle size of the NiFe2O4 nanoparticles could be determined by means of Transmission Electron Microscopy. This work aimed at the investigation of the dielectric properties such as the dielectric loss and the dielectric constant of NiFe2O4 nanoparticles at varied frequencies and temperatures. In addition, the magnetic properties of the NiFe2O4 nanoparticles were studied.

Resumo em Inglês:

The electrochemical behavior of HVOF produced hydroxyapatite (HA) and 80HA-20TiO2 coatings were investigated using electrochemical techniques in natural aerated Hanks' solution in the presence and absence of bovine serum albumin (BSA) for 30 days. All samples presented open circuit potential oscillations, which were associated to the porous nature of the coating that allows the electrolyte reaches the substrate causing activation - passivation at the bottom of the pores. The polarization studies indicated that the 80HA-20TiO2 coating was the only one that showed a narrow potential passive region from around -0.4 V to 0 V in the presence and absence of BSA, indicating the beneficial influence of the addition of TiO2 to the HA coating stability. Our results indicated that BSA in Hanks' solution diminishes the stability of the metallic oxide layer present on the Ti-based alloy accelerating the degrading of hydroxyapatites coatings / substrate interface due to its chelating ability.

Resumo em Inglês:

The effect of alcaline and hot water surface treatments of piassava Attalea funifera fibers was investigated. The efficiency of each treatment was evaluated by Fourier transform infrared spectroscopy, X-ray diffractometry, optical microscopy, scanning electron microscopy and atomic force microscopy. The alkaline treatments were effective in removing the superficial lignin layer from the fiber, while the hot water treatment was not. Treatment with hot water and NaOH caused fiber defibrillation. NaOH was most effective in promoting both, a decrease in fiber diameter and an increase in fiber surface area. Treatment with Ca(OH)2 led to the formation of a CaCO3 layer deposited on the fiber, preventing defibrillation. The crystalline structure of the fiber was not altered by any of the treatments, maintaining type I cellulose.

Resumo em Inglês:

In this study, a multi-parameter design of experiments, using Taguchi method, has been conducted in order to investigate the optimum curing conditions for glass fabric/epoxy laminated composites, followed by a statistical analysis and genetic algorithm optimization. Heating rate a, temperature T1 and duration h1 were treated as independent variables in a L25 Taguchi orthogonal array addressing five levels each. Tensile load and flexural strength were examined as pre-selected quality objectives. The results of the analysis of variance performed showed that the significant parameters for both tensile and flexural strength were temperature and duration, at a 95% confidence level. The estimation of the curing parameters for optimum tensile and flexural performance was achieved with an error considerably lower than 1%. The Poisson regression analysis was introduced to achieve a highly accurate regression model, with R2 greater than 97% for both optimization criteria. Finally, these two regression models were converted into a two-fold function for maximizing both criteria, and used as fitness function for a multi-objective optimization genetic algorithm.

Resumo em Inglês:

The present study is dedicated to the experimental determination of strain parameters at rolling of aluminium matrix with inserted wire netting. Two types of stainless steel fabric netting with different orientation to the rolling axis were placed between two aluminium strips and hot rolled. The rolling temperature and reduction were varied to achieve the sound bonding between the matrix layers and steel net. During the study, the following main investigations were made: strain on areas of longitudinal and transverse cross sections of the composite was measured; stretching and ovalization of net wiring and changes in the net cell angles were determined; mechanical properties of composites along the rolling direction were tested. The experiments were summarized by following contradiction: the contact pressure, required for the bonding of aluminium layers, produces extreme tensile strain on the inserted wires, reducing the mechanical properties of the reinforcing net and, consequently, reducing the properties of the entire composite. Strips with diagonally oriented reinforcing net showed the best results in the longitudinal tension tests.

Resumo em Inglês:

Detailed analysis of the effects of multiple extrusions on physical, mechanical, micro-structural as well as dynamic mechanical thermal properties of natural fiber high-density polyethylene (HDPE) composites is reported. Composite materials containing HDPE, wood flour, and Maleic Anhydride polyethylene (MAPE) were manufactured and subjected to a recycling process consisting of up to four times grinding and reprocessing under industrial conditions. A wide range of analytical methods including bending tests, modulus of elasticity, impact strength, Scanning electron microscopy (SEM), fiber length measurement, water absorption tests, and dynamic mechanical thermal analysis (DMTA) were employed to understand the effects of recycling on natural fiber-HDPE composites. The results revealed that the recycled composites had lower bending strength and modulus of elasticity values, as compared to the reference counterparts. Also, the once recycled composites showed higher impact strength. Results, as well, indicated that generally the recycled composites had lower water absorption values as compared to the reference ones. The results obtained from DMTA exhibited a decrease in storage modulus and an increase in mechanical loss factor (tan δ) for all composites subjected to recycling. Alterations in phase transition temperatures and intensities were also monitored and the possible reasons were analyzed.

Resumo em Inglês:

NiO thin films were deposited on Si and Corning 1737 glass substrates using radio frequency (rf) magnetron sputtering system. The physical properties of NiO films under different sputtering power were thoroughly studied. The XRD results indicated that as-prepared NiO films with the sputtering power above 100 W developed only (200) preferred orientation. The AFM results showed that the NiO films were composed of different-size NiO nano-grains and the grain size increased with increasing the sputtering power. The samples marked A-E under the sputtering power of 80, 100, 120, 140 and 160 W have optical band gap values of 3.70, 3.65, 3.50, 3.45 and 3.44 eV, respectively. Comparatively, the controllable electrical properties of the films could be achieved by the variation of crystal quality arises from the sputtering power.

Resumo em Inglês:

This study aimed to assess the effect of casting speed and the addition of Al5%Ti1%B inoculant in the casted AA5052 aluminum alloy plate manufactured by the Direct Chill process. The focus of this work was to decrease the rejection index of rolled products due to the occurrence of superficial flaws on plates. These defects impact directly on the production costs and on the rolled product quality. The main cause of those flaws is associated with the billet porosity that is related with the excess of atomic hydrogen incorporated into the metallic bath and with the metal shrinkage during solidification. Four different cast conditions were industrially tested, combining two casting speeds and two inoculants amounts. The effect of those variables on the alloy mechanical properties and on their performance in rolling process was also assessed. It was observed that the higher the casting speed and the inoculant fraction, the more refined the microstructure and the lower the fraction and diameter of formed micropores. The increase of casting speed and the inoculant fraction improved the AA5052 alloy rolling performance. The application of these results in an industrial scale performed a decrease from 5.03% to 0.39% per month in the rejection index of rolled products.

Resumo em Inglês:

Rare earths (Europium, cerium)-doped CdS nanofilms are prepared using the growth technique chemical bath deposition (CBD) at the reservoir temperature of 70±2°C varying the synthesis time in a wide range. For the rare earths doped CdS nanofilms the synthesis time was ranged from 80 to 135 min. The rare earths molar concentration was in the range 0.0≤x≤3.47, which was determined by energy dispersive X-ray spectroscopy (EDS). The X-ray diffraction (XRD) analysis reveals that CdS nanofilms showed the zinc blende (ZB) crystalline phase. The nanocrystal size was ranged from 2.67 to 2.35 nm for the CdS and 1.84-2.33 nm for rare earth-doped CdS that were determined by the Debye-Scherrer equation from ZB (111) direction and it was confirmed by transmission electron microscopy (TEM). The doped CdS exhibits a direct band gap that diminishes with the increase of the synthesis time, from 2.50 to 2.42 eV, which was obtained by transmittance. The room-temperature photoluminescence of CdS presents the band-to-band transition at 431 nm, which is associated with quantum confinement because the grain size is less than its Bohr exciton radius and a dominant band at 523 nm, which is called the optical signature of interstitial oxygen. Eu3+-doped CdS photoluminescence shows the dominant radiative peak at 576 nm that is associated to the intra-4f radiative transition of Eu3+ ions, which corresponds to the magnetic dipole transition, (5D0→7F1). For the Ce3+-doped CdS the dominant radiative transitions are clearly redshifted. Additionally, other radiative peaks associated at structural defects are observed. The passivation of the CdS by rare earths was approximately of two orders of magnitude obtaining better results with cerium.

Resumo em Inglês:

In this work, microstructural characterization and mechanical properties of P91 and Incoloy 800HT dissimilar laser beam welded joint were analyzed. In addition to that, metallographical studies were conducted using Optical microscopy, Scanning electron microscopy (SEM) equipped with Energy-dispersive X-ray spectroscopy (EDX) and X-Ray diffraction analysis (XRD). Effect of specific point energy on weld microstructure was predicted and it was compared with fusion zone hardness. The δ-ferrite content of the welds was predicted and it was correlated with the results measured by ferritoscope. Increase in heat input led to a minimal increase in the weld bead width and also the depth of penetration as predicted by microstructural studies. The traces of δ-ferrite in the interface of P91 side led to higher strength and microhardness of the weld. Failure of tensile specimens in the HAZ of Incoloy 800HT side was because of lower ferrite content (0 to 0.36) in that region and also due to the presence of the brittle intermetallic phases. The tensile strength of higher specific point energy welds was greater compared to other welds because of precipitation hardening and presence of δ-ferrite. Fractography results of fracture surfaces contain uniform dimples which showed that the failure took place in a ductile mode.

Resumo em Inglês:

Chalcogenide alloys CuMnAlSe3, CuMnGaSe3 and CuMnInSe3, new members of the semiconductor system I-II-III-VI3, were synthetized and structurally characterized by the Rietveld method using X-ray powder diffraction data. All compounds crystallize in the tetragonal space group P4 2c (Nº 112) with a CuFeInSe3-type structure.

Resumo em Inglês:

This work reports the synthesization of nanoparticles cobalt oxide (Co3O4) with no secondary phase by a modified sol-gel method and its structural morphological and electrochemical characterizations. FTIR, XRD and Raman analysis showed the formation of spinel cobalt oxide with no secondary phase. TEM images revealed that an undefined morphology with average crystallite size estimated by Scherrer's equation was found to be 30 nm. Experiments of cyclic voltametric, galvanostatic charge-discharge and impedance spectroscopy were evaluated at 1 mol L-1 KOH and revealed an intrinsic pseudocapacitance. The studies of complex capacitance and complex power revealed the resistive and capacitive characteristics with a specific capacitance of 120 F g-1.

Resumo em Inglês:

Sn-36Bi-22Cu (wt.%) ternary eutectic alloy was prepared using vacuum melting furnace and casting furnace. The samples were directionally solidified upwards solidification rate varying from 8.3 to 166 µm/s and at a constant temperature gradient (4.2 K/mm) in a Bridgman-type directional solidification furnace. The composition analysis of the phases and the intermetallics (Cu3Sn and Cu6Sn5) were determined from EDX and XRD analysis respectively. The variation of the lamellar spacing (Bi-rich phase) and the Cu3Sn phase spacing with the solidification rate were investigated. The dependence of microhardness, ultimate compressive strength and compressive yield strength on solidification rate were determined. The spacing and microhardness were measured from both longitudinal and transverse sections of the samples. The dependence of microhardness on the lamellar spacing and the Cu3Sn phase spacing were also determined. The relationships between phase spacings, solidification rate and mechanical properties were determined from linear regression analysis.

Resumo em Inglês:

Magnetite nanosized particles synthesis was achieved by two different routes. Assessment of microstructure was carried out aiming at comparing the outcome of synthesis parameters on the crystallinity, distribution of particle dimension and magnetic activity of nanosized particles precipitated in aqueous solution. Increasing of the nanoparticles crystallite size by stirring could be evidenced by the results. Temperature does not significantly affect crystallite size and crystallinity. The type of precursor was the factor that most contributed to the definition of crystallinity and particle size distribution. The route which used FeSO4.7H2O as precursor favored large crystallite sizes and crystallinity, while the route which used Fe2SO4.7H2O and FeCl3.6H2O as precursors resulted in much smaller crystallite sizes and crystallinity.

Resumo em Inglês:

Menthol-loaded PLGA micro/nanospheres were synthesized using the multiple emulsion/solvent evaporation technique. Parameters such as stirring rate, external surfactant content, PLGA/menthol weight ratio, solvent evaporation and lyophilization time were evaluated as well as the degradation of micro/nanospheres in an artificial saliva medium. The menthol/PLGA micro/nanospheres thus obtained had a size distribution of between 217 nm and 13 µm and particles with spherical and dense morphology were evidenced by SEM micrographs. FTIR and TGA data showed an increase up to 60% of menthol incorporated in the micro/nanoparticles. The degradation of menthol-loaded PLGA micro/nanoparticles in artificial saliva significantly affected the particles morphology and appears to be an effective medium for releasing menthol.

Resumo em Inglês:

The aim of the present work was to explore the correlation between the physical metallurgy of titanium alloys and its main attributes to select optimized materials for structural aircraft applications in the landing gear beam. The Ashby's method was employed as the materials selection strategy to consolidate and evaluate the data collected from the current literature in a comprehensive and consistent analysis. Landing gear beam materials are mainly β and near-β alloys. Considering the need for high specific strength and fatigue resistance, the best candidate among them was Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe alloy. Finally, a brief discussion of additional aspects related to alloy design, microstructural features and their influence on the mechanical properties is presented.

Resumo em Inglês:

The microstructural alterations suffered during the process of drawing deformation and subsequent annealing of pearlitic steel wires, were evaluated by scanning electron microscopy and atomic force microscopy. The deformed material showed the curling structure in cross section while, in the longitudinal section, the lamellae was aligned with the drawing direction. The microstructural characterization of deformed samples also allowed observing an interlamellar spacing reduction and the intermediate lamellae alignment process. After the heat treatment at 1000ºC for 5 min the microstructure was restored, however, few recrystallized grains were observed. The recovery was the dominant phenomenon, due to factors associated with curling structure that inhibited recrystallization.

Resumo em Inglês:

The microstructure of ternary alloys in the Al rich corner of the Al-Cu-Si and Al-Ag-Cu systems were analyzed in order to determine the solidification path in the different structural regions expected from the equilibrium phase diagram. The analysis was based on theoretical models developed in the literature for solidification of ternary eutectic system alloys under simple lever rule assumptions. Optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDAX) were used to study the microstructure formed in each case. The observations were consistent with model predictions: Al-Cu-Si system showed two binary eutectics: non faceted-non faceted (nf-nf) AlCu and faceted-non faceted (f-nf) AlSi, Al-Ag-Cu system showed 2 binary regular eutectics (nf-nf) and a ternary semi-regular Brick type eutectic. The results provided an example of a methodology for use in ternary and multicomponent alloys.

Resumo em Inglês:

In the present work, the effect of Na doping on optical, structural and electrical properties of Na doped NiO thin films were studied. The spray pneumatic method was used to deposit the Na doped NiO thin films in the range 0 to 5 wt.%, it are investigated at a substrate temperature of 420 °C with NiO solution 0.1 M. Firstly in the XRD specra, as found that a only (111) peak was observed for Na doped NiO thin film indicate that the Na doped NiO thin films a monocrystalline in nature with cubic structure. The maximum crystallite size of Na doped NiO thin films was 18.90 nm at 3 wt.%. Secondary, the optical transmissions spectra Na doped NiO thin films having a high transparency with comparing to undoped film in visible region. The band gap energy was decreased after doping by Na and reaching a minimum value is 3.53 eV at 2 wt.%. The minimum value of Urbach energy was 0.312 eV, it is obtained at 3 wt.%. In the end, the minimum electrical resistance of the Na doped NiO films was located at 5 wt.%. The optimum Na doping amount is achieved at 3 at %.

Resumo em Inglês:

ZnO nanostructures were synthesized by a proteic sol-gel method, using zinc nitrate hexahydrate and gelatin as precursors. Size and shape evolution of ZnO nanostructures were achieved by annealing temperature in the range 250-1000 ºC. The crystalline structure, morphology and optical properties of the ZnO nanoparticles were characterized by X-Ray Diffraction (XRD), Raman Spectroscopy (RS), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and room temperature Photoluminescence (PL). The result of structural characterization shows the formation of platelets and nanorods in the micro-scale and ZnO nanostructures with high quality hexagonal wurtzite crystal. Sharp peaks in RS after annealing temperature, related to wurtzite structure, were observed corroborating with XRD and TEM measurements. Room temperature PL spectra showed two contribution bands which peaked at ~380 nm, originating from the recombination of free excitons, and ~520 nm corresponding to the impurities and structural defects, like oxygen vacancies and zinc interstitial. The effects of annealing temperature in the structural and optical properties are detailed and the results compared among the experimental techniques. The high quality of the samples obtained by an alternative organic precursor method opens a low-cost route to technological applications of zinc oxide.

Resumo em Inglês:

The growth of titanium dioxide nanotubes (TiO2) via anodization process depends on the controlling parameters such as applied potential, anodization time, and electrolyte composition. In the present work, the Taguchi method was applied to evaluate statistically the influence of the anodization parameters on the morphology of anodized TiO2 films. Mixture of ethylene-glycol and glycerol was used as an electrolyte and the settings of the experimental design were parameterized on the basis of four important anodization factors consisting of chemical pretreatment, amount of fluoride, water content and applied potential. Samples were characterized by XRD and FEG-SEM. Based on 4 variables at 3 different settings, full factorial plan requires 34 = 81 tests. In this work the experiment was designed on the basis of an L9 (34) orthogonal array (4 variables, 3 levels, 9 tests). The optimum conditions were found on the basis of smaller-is-better and larger-is-better analyses. The signal-to-noise ratio was employed to find optimal process parameters levels and to analyze the influence of these parameters on the tubular length, internal and external diameters and formation of nanograss on the film surface. Hence, it is clearly shown that the performance of TiO2 nanotubes can be evaluated by the Taguchi method.

Resumo em Inglês:

In the current investigation, corrosion behavior and microstructural variations of explosion-welded joint of bronze-carbon steel dual-layer plates were studied. The resultant curves of potentiodynamic's polarization tests demonstrated that the lowest corrosion rate was related to the sample with maximum explosive load thickness, and the highest corrosion speed was for the sample with minimum standoff distance. EIS test results of welded samples were indicative of creating a passive layer at the beginning of immersion process which showed that the polarization resistance has been reduced by increasing of explosive load thickness. So, the corrosion mechanism included two stages; at the beginning of immersion, for the samples with the lower thickness of explosive load, a passive layer would be created around the component due to higher concentration gradient and then, by removing of this layer, the galvanic couple determines the corrosion rate.

Resumo em Inglês:

Thermolysis behavior of the Li-Sr-Al-N-H hydrogen storage system prepared by ball milling of Sr2AlH7 + LiNH2 mixture was investigated in this paper. The results show that thermal decomposition of the Li-Sr-Al-N-H system proceeds mainly in two steps with only hydrogen desorption. The thermal stability of this system is lowered as compared to the individual starting material, resulting in the hydrogen desorption initiating from about 125 °C. In addition, about 0.91 and 1.53 wt.% of hydrogen can be isothermally desorbed within 180 min at 180 and 330 °C, respectively. The decreased thermal stability of the Li-Sr-Al-N-H system might be attributed to the chemical reactions between the starting materials during the heating process with the formation of LiSrH3 and N-containing amorphous phases.

Resumo em Inglês:

This in vitro and in vivo study compared different topographies of Ti samples (dense, porosity of 30% and 40%) with or not CaP coating, prepared by powder metallurgy. Osteogenic cells from newborn rat calvaria were plated onto the samples and cell adhesion (24 hours), alkaline phosphatase activity (7 and 10 days) and mineralization nodules (14 days) were assessed. Sixteen rabbits were used for in vivo study. Each animal received three non-treated and three treated implants in the right or left tibia, respectively. Histometric evaluation of bone-implant contact (BIC) were assessed at 1, 2, 4 and 8 weeks. Metallographic analysis revealed porosities of 30% and 40%, with pore size ranging from 250 to 350 µm. Cell adhesion test and ALP revealed similar cell behavior, independently of topography and CaP coating (P > 0.05%). However, CaP coating combined with porosity of 40% influenced positively the mineralized matrix formation (P < 0.05%). CaP-coated implants showed higher BIC than non-CaP implants and BIC was different between the short (1 and 2 weeks) and long (4 and 8 weeks) healing periods (P < 0.05%). The results suggest that CaP coating combined with 40% porosity implants allowed greater osteogenesis in vitro and increased BIC in vivo.

Resumo em Inglês:

In this work, the corrosion resistance of Inconel 625 coatings applied to AISI 4140 steel plates was evaluated. Coatings were produced by High Velocity Oxygen Fuel (HVOF) by use of two different equipment which use either kerosene (liquid) or propane (gas) as fuel. The resulting coatings were evaluated in two conditions: as-deposited and after a surface finishing process by grinding. Residual stress distributions in the coatings were characterized by X-ray diffraction and their morphology was verified through metallography and roughness measurements. Potentiodynamic polarization corrosion testing complemented their analysis. The results show a strong influence of the surface finishing process on the corrosion performance of the coatings.

Resumo em Inglês:

The objective of this work is the evaluation of hydrogen effects on the martensitic transformation and strain hardening in Duplex Stainless Steels (DSS) SAF 2205 (UNS S32205/S31803). DSS are two-phase alloys (austenite and ferrite), which are used for applications requiring high mechanical strength, in corrosive environments. Therefore, it is necessary a better understanding of the phenomena involved on the hydrogen embrittlement. For this, in situ measurements of X-ray diffraction were made during tensile test in H2 cathodically charging DSS 2205. The hydrogen charging reduces the stress relaxation, reducing the ductility and suppressing the hydrogen-induced austenitic to martensitic transformation. In addition, it also reduces the strain hardening (dislocation multiplication) in austenite. The strain hardening seems to have a higher influence than martensitic transformation on fracture process, even in absence of hydrogen.

Resumo em Inglês:

Au nanoparticles supported on TiO2 were prepared by a liquid-phase reduction method using HAuCl4.3H2O as the Au precursor, TiO2 as the support, a solution of ethylene glycol/water as solvent and reducing agent and sodium citrate as reducing agent and stabilizer. The Au/TiO2 catalysts were prepared using different routes and characterized by Energy-dispersive X-ray spectroscopy, X-ray diffraction and Transmission Electron Microscopy and tested for preferential oxidation of carbon monoxide in hydrogen-rich stream (CO-PROX reaction). The way that the Au precursor, the TiO2 support and the sodium citrate is added to the ethylene glycol/water solution strongly influences the Au nanoparticle sizes and the catalytic activity of the obtained materials.

Resumo em Inglês:

This paper presents the results of Molecular Dynamics (MD) simulations of Cu60.0Zr32.5Ti7.5 alloy through the open source code LAMMPS. Amorphous samples were produced by quenching the molten metal from 2300 to 300 K. The pair distribution functions of the liquid and solid were calculated. Moreover, the atomic short-range order at 800, 700 and 300 K was obtained by using the Voronoi tesselation method. Cu-centered icosahedral clusters were the prevailing configuration. The tensile stress-strain curve showed that the material present plastic deformation, however, shear bands were not observed in the MD simulation. The evolution of viscosity in temperatures higher than its glass transition temperature was also determined. Furthermore, the fragility of the alloy at glass temperature was evaluated.