Resumo em Inglês:

Plasma nitriding of a solution annealed and aged 300 grade maraging steel was studied aiming to increase the creep resistance. The surface microhardness reached 1,140 HV, producing 50 µm layer composed of ε-Fe3N and γ'-Fe4N nitrides at the uppermost sample layer. The inner core remained unaltered presenting typical plate-like martensite microstructure of maraging steels with average microhardness of 604 HV. Surface RMS roughness in the nanometric scale increase from 52 nm to 71 nm. The continuous layer of iron nitrides seems to behave as a barrier for oxidation and for inward oxygen diffusion improving the creep resistance by reducing the steady-state creep rate (εs) in 52-65% when compared with the literature results. Dominant creep mechanism is controlled by dislocations climb. Fracture surfaces of specimens presented ductile failure consisting of equiaxed and bi-modal dimples in the fibrous zone surrounded by 45º shear lip. Nitrided sample presented a reduced ductility, associated to the hard surface layer.

Resumo em Inglês:

Spark plasma sintering is used to consolidate a WC-Co powder produced from milled discharged hard metal cutting inserts. The powder was mixed to 10%wt Co powder and spark plasma sintered (SPS) under 80Mpa pressure, at 1200ºC with heating rate of 160ºC/min. A reference alloy was prepared with a commercial WC powder and 10%wt. Co under the same conditions. The structures of both alloys were investigated by means of scanning electron microscopy and Vickers hardness. The results show structures with densities and hardness at the same level. SPS can be used to produce hard metal pieces directly from scrap powder without any prior chemical and thermal treatment.

Resumo em Inglês:

This study investigated the potential of Brazilian kaolin as a low-cost adsorbent for the removal of Malachite Green (MG) from colored effluents. The morphology, chemical structure and surface properties of the adsorbent were investigated by characterization techniques such as X-ray diffraction, N2 adsorption-desorption isotherms, Fourier transform infrared spectroscopy, X-ray fluorescence spectrometry, scanning electron microscopy, thermogravimetric analysis and particle size distribution. A possible technological application of raw kaolin is the MG removal from aqueous media, which was investigated using batch adsorption experiments. The adsorption kinetics was studied using the pseudo-first order, pseudo-second order and Elovich models. The adsorption isotherms were studied using the Langmuir, Freundlich and Sips models. The Elovich model was the more adequate to represent the adsorption kinetic, while the equilibrium was well represented by the Langmuir model. The maximum adsorption capacity, at pH of 6.3 and temperature of 25ºC, was 128 mg g-1, and this satisfactory result may be associated with some adsorbent properties. Therefore, the results revealed that raw kaolin can be utilized as a promising low-cost adsorbent to remove MG from colored effluents.

Resumo em Inglês:

Multilayered armor systems (MAS) composed of relatively lighter materials with capacity to provide personal ballistic protection are being extensively investigated and used in armor vests. A typical MAS to stand high impact energy 7.62 mm bullet has a front ceramic followed by an aramid fabric laminate, such as Kevlar™. Since both the army and municipal police personnel might need to wear an armor vest, a large number of vests needs to be supplied. In the case of Kevlar™, one of the most expensive MAS material with an expiration time of 5 years, the possibility of its replacement by an equally ballistic efficient low cost material and more durable could be a relevant economical advantage. Natural fibers composites have recently been investigated as possible alternatives for Kevlar™. In particular, the fiber extracted from the coconut fruit, known as coir fiber, normally disposed as waste, could be a low cost material for this purpose. Therefore, the present work investigated the possibility of using coir fiber mantle, with different volume fraction, reinforcing epoxy composites as MAS second layer. It was found that 30 vol% of coir fiber composite displayed similar ballistic performance as compared to Kevlar™ with substantial economical advantage.

Resumo em Inglês:

In this work, zinc aluminate spinel was prepared by two methods of directly synthesis (without calcination): microwave assisted combustion and hydrothermal method. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2-adsorption/desorption isotherms. The XRD patterns confirmed the formation of cubic ZnAl2O4 spinel structure with no secondary phases for both synthesis routes, whereas the hydrothermal method yielded powders with crystallite size 3 times smaller (6.9 nm), as compared to the powders produced by microwave assisted combustion method (25.6 nm). The micrographs revealed agglomerated powders with plate-like morphologies for both routes. Nitrogen adsorption/desorption isotherms (BET) revealed higher surface area (183 m2.g-1) and greater pore volume (0.173 cm3.g-1) for ZnAl2O4 powders prepared by the hydrothermal method.

Resumo em Inglês:

The influence of alternating electric field (AC) in the structure and dynamics of giant unilamellar vesicles (GUVs) comprised of 1,2-dilauroyl-sn-glycero-3-phosphatidylcholine (DLPC) is reported. The investigations were conducted by using optical fluorescence microscopy as the method of analysis. The lipid membrane of the DLPC GUVs at the fluid phase can be deformed and they migrate towards the electrodes under AC electric field. Nevertheless, membrane disruption or vesicle fusion was never noticed. The addition of concentrated glucose solution influences the osmotic pressure of the system leading to the formation of filaments at the outer region of the GUVs. These long flexible cylinders do not retract spontaneously. However, the application of AC electric field (20 V/mm, 20 Hz) enables the filaments to be retracted back to the GUVs membrane at a calculated speed of 0.18 µm.s-1

Resumo em Inglês:

Maraging steels with 18wt%Ni and 10wt%Co are precipitation hardenable steels selected for special applications. These steels are quenched and aged in the 480 - 600ºC range. Ti and Mo are added to precipitate during aging as fine Ni3(Ti,Mo) and Fe2Mo particles. Aging at high temperatures causes overaging due to coarsening of particles and austenite formation. SAE 4340 is a typical low alloy medium carbon steel for quenching and tempering. The best combination of mechanical properties is attained by quenching and tempering in the 650 - 670ºC range. These two steels are selected for services where an optimum combination of mechanical strength, toughness and fatigue resistance is required. In this work, the austenitizing temperature in the quenching treatment was varied in order to evaluate the effects on microstructure and mechanical properties of both steels. The results showed that the effect of previous austenite grain size on the toughness was different in the two steels analyzed.

Resumo em Inglês:

This paper presents the results of a study that aimed to monitor and evaluate biodegradation in soil, by the mass loss and the mechanical properties of plastic tubes. For this work, there were extruded and injected plastic tubes made of biodegradable polymer poly(hydroxybutyrate) - (PHB) and composite PHB/Wood Flour and PHB/Sisal Fiber, both with 20% fiber. There were used three biodegradation test devices for 30, 60 and 90 days. At the end of each test, the biodegraded samples were taken from soil, washed thoroughly with water, dried and weighed to evaluate the mass loss. Mechanical properties were evaluated using flexural tests before and after biodegradation in soil. Based on the results, it was observed that all the studied tubes lost mass over the biodegradation test, and the tubes of biodegradable composites lost more weight than pure PHB.

Resumo em Inglês:

Ramie (Boehmeria nivea) fiber is one of several lignocellulosic fibers with superior strength, but the least investigated, particularly as reinforcement in strong, tough polymeric composites. This paper presents mechanical properties for polyester reinforced with aligned ramie fibers up to 30% by volume. It was found that adding 30 vol% of ramie fibers increases the flexural strength of polyester about three times (212 ± 12 MPa vs. 63 ± 7 MPa) and tensile strength by a factor of two (89 ± 9 MPa vs. 53 ± 3 MPa). Polyester-ramie fiber composites also displayed a significant improvement in toughness. The impact energy values, as measured by Charpy and Izod impact tests, increased nearly two orders of magnitude for 30 vol% ramie fiber composite as compared to neat polyester. Additionally, fractographic studies revealed reasonable wetting of fibers by the polyester resin, and FTIR analysis confirmed a hydrophilic nature of ramie fibers. In spite of weak adhesion between hydrophilic fibers and hydrophobic matrix, composites of improved strength and toughness were demonstrated in this study. Limited fiber-matrix adhesion was reflected in preferential longitudinal propagation of cracks along the fiber/polyester interfaces, indicating also that most of the fracture area is associated with the fiber surface.

Resumo em Inglês:

In this work, physical, chemical and morphological modifications of three different polyamide 6.6 (PA6.6) fabrics were investigated using double barrier dielectric (DBD) plasma treatment. Several techniques of characterization were used to study the effects caused by the interaction between plasma discharge and polyamide fabrics, such as: contact angle, water drop adsorption, Energy Dispersive Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), whiteness by Berger degree and tensile strength. All analyses performed in this study showed that DBD plasma discharge, when applied on PA6.6 fiber, produces significant modifications on the surface of this substrate, without altering its intrinsic properties, thus proving the effectiveness of this important technology to the textile industry.

Resumo em Inglês:

Biopolymer films have several industrial applications because they are environmentally sustainable. Cassava starch is a biopolymer that is easily available, but has limitations: it is hydrophilic, poorly resistant and degradable. The improvement of these properties was proposed in this research from the use of bentonite clay (BT) as a filling material. The compatibilization of this in the polymer matrix was obtained by ion exchange with an organic anionic surfactant. The formation of intercalated or exfoliated starch nanocomposites in the presence of natural or modified clay was characterized by XRD, FTIR, AFM and SEM. The improvement of water vapor, thermal and mechanical properties was investigated by WVP, solubility, TGA and tensile test. The starch nanocomposites in the presence of modified clay showed a better result than those of natural clay. There was no significant difference in the color of the starch film in the presence of the natural or modified clay.

Resumo em Inglês:

In this study, the effects of the devulcanization process realized by an intermeshing co-rotating twin-screw extruder (ICTSE) on three vulcanized Natural Rubber (NR) composites with different crosslink densities (CD) have been investigated. The extrusion parameters were fixed, as well as the initial material granulometry and auxiliary thermoplastic added to the process. After composites vulcanization, they were characterized accordingly their soluble fraction (SF), crosslink density (CD), mechanical properties and thermogravimetry (TGA). The extrusion was performed on the vulcanized elastomers pursuing selectively crosslink rupture and the same characterization previously cited was conducted on the devulcanized material, except the mechanical properties analysis. The extrusion demonstrate effective devulcanization, evidenced in the increasing of soluble fractions, reduction in crosslink density and thermal stability gain. These results are directly affected by preliminary differences on materials structure and presence of ethylene vinyl-acetate (EVA) on extrusion.

Resumo em Inglês:

In this work, nanometric Al2O3 (1-5 vol.%) particles (13 nm, 100 m2/g) were added to a 19.58Li2O•11.10ZrO2•69.32SiO2 (mol%) (3.5 µm, 2.5 m2/g) parent glass-ceramic matrix to prepare composites with the purpose of studying the influence of Al2O3 on their structure, microstructure, mechanical, thermal and electrical properties when sintered by fast firing. The parent glass-ceramic was prepared by melting and fast cooling (in water) to obtain a glass frit. The resulting glass frit was milled according to a two-step procedure consisting on a dry milling stage followed by a long wet milling step down. Each composition was wet homogenized and then dried at 110 ºC for 48 h for disaggregation. The obtained powders were uniaxially pressed (100 MPa) and compacts sintered by fast firing (175 ºC/min) between 800 and 900 ºC for 30 min. The composites, with relative densities ranging from 89% to 93%, showed zircon and β-spodumene as main crystalline phases. The hardness and Young's modulus varied from 4.5 to 6.5 GPa, and from 65 to 102 GPa, respectively. The formation of β-spodumene in the obtained composites leads to reduce the CTEs, whose values ranged from 13 to 7 x 10-6 ºC-1.

Resumo em Inglês:

This study carried out the microstructural characterization, by light microscopy, of sintered SiC in the presence of liquid phase at temperatures of 1800, 1850 and 1900 ºC, added with Al2O3 and Y2O3 as well with Al2O3-YAG composite in the proportions of 5, 10 and 15% by weight. It was possible to observe the formation of microstructural patterns resulting from the heterogeneous segregation of the additives, such observation is associated to the pulling of additives during the initial stage of ceramography. Two ceramographic paths were followed: method I - surface grinding followed by manual polishing and method II - automatic grinding and polishing. In order to compare the two techniques the analysis of 3D roughness by light interferometry and the Vickers microhardness test were used. It was concluded by the analysis of variance with 95% confidence that the degree of finishing obtained by both methods allowed the adequate microstructural characterization, as well as, to meet the requirements established by the ASTM C1327-15 standard for hardness test.

Resumo em Inglês:

The objective of this work is obtaining W-30 wt% Cu composite powder from ammonium paratungstate hydrated (APT) and hydrated copper nitrate and investigating the influence of some production process parameters of W- 30 wt% Cu in particles form which results in high sinterability and densification of W-30 wt% Cu composite. To achieve this objective, the powder was obtained by manually mixing the APT and copper nitrate and reducing under a hydrogen atmosphere at 800 °C and then compacting at 500 MPa and sintering in a tubular furnace at 1200 °C for 60 minutes. The obtained materials were characterized by XRD, SEM, EDS, particle size analysis, density and microhardness measurements. The composite powder showed a good homogenization of Cu in W with very fine and agglomerated particles and a mean crystallite size of 25.64 nm. SEM coupled with EDS with mapping analysis revealed a homogeneous distribution of Cu and W in the sintered sample. The composite had a relative density of 96.77% and a microhardness of 523.66 HV. Therefore the method of obtaining the composite powder is feasible to sinter W-30 wt% Cu powder due to a greater dispersion and homogenization of phases and the average particle size.

Resumo em Inglês:

This paper explored the effect of adding organic fibers from either bamboo or sugarcane on the mechanical properties of concrete. Cylindrical and prismatic specimens were made containing 2% and 5% v/w (volume to weight) of vegetable fibers to concrete. Following 28 days of curing period, the samples were evaluated for compressive strength, tensile strength using diametric compression, tensile strength during bending and static modulus. It was discovered that all concretes produced met the minimum strength of 20 MPa recommended by NBR 6118 for structural purposes, and it was observed an increase of the compressive strength on the specimens with addition of organic fibers. Moreover, an increase in the compressive strength was observed in the specimens with fiber addition, although no significant variation of water absorption was noticed when compared with the standard concrete. In conclusion, the concrete containing 2% v/w of bamboo fibers showed better mechanical strength and static modulus of elasticity when compared to both concrete with sugar cane fibers addition and the concrete without any additional fibers.

Resumo em Inglês:

The AISI 317L stainless steel is an austenitic grade with at least 3%Mo. Recently, this steel has replaced AISI 316L in many applications in chemical and petrochemical industries, due to its higher pitting corrosion resistance. The microstructure of the hot rolled and annealed material studied in this work consists of austenitic grains and 4.0% of delta ferrite (δ) with elongated islands morphology. This microstructure was modified by three processes: cold rolling with 87% of reduction, aging at 450ºC for 400 h, and welding by gas tungsten arc welding (GTAW) process. The corrosion resistance was evaluated by anodic polarization tests (ASTM G-61) and critical pitting temperature tests (ASTM G-150). Cold rolling produced a microstructure consisting of elongated grains of austenite and martensite α', high dislocation density and the elongated islands of delta ferrite present in the annealed material. Welding produced a dendritic microstructure with 7.0% of delta ferrite and some σ precipitated in the ferrite. Finally, the aging at 450ºC for 400 h provoked the decomposition of ferrite. The results show that these microstructural changes affected the pitting corrosion resistance, as detected by ASTM G-61 and ASTM G-150 tests.

Resumo em Inglês:

This study aimed to investigate the effects of difference in nickel content and the tempering temperatures on the corrosion resistance in 13Cr2Ni0.1C and 13Cr1Ni0.15C steels. Results showed that passive film in 13Cr2Ni0.1C steel is formed more quickly at the lowest and highest tempering temperature (650°C and 750°C) but the lowest tempering temperature (650°C) showed better resistance to corrosion pitting. There was passive film formation and pitting corrosion in all tempering temperatures of the 13Cr1Ni0.15C steel and changes in tempering temperature does not significantly alter polarization curves, showing similar behavior to steel 13Cr2Ni0.1C tempered at 650°C.

Resumo em Inglês:

Nanotechnology is seeing as having potential to raise benefits to several research and application areas. Recently materials with nanostructured surfaces of nanopores, nanotubes and nanowires have become an important investigation field, since their chemical and physical properties may be substantially different from those of the corresponding substrate. In face of the necessity of assuring that such modifications are not deleterious to the mechanical behavior, the purpose of this work was to evaluate the fatigue performance of CP-Ti grade 2 with the surface modified by the formation of nanotubes on their different crystalline structures. The nanotubes layers were produced by anodic oxidation using a potential of 20V during 1h and a solution of glycerol, H2O and NaF, and analyzed by scanning electron microscopy. In order to obtain the anatase and rutile structures, annealing treatments were respectively performed at 450°C and 650°C. The axial fatigue tests were conducted in physiological solution at 37°C following the stepwise load increase approach. When compared to the material without surface modification (polished surface), the results showed that the anatase phase did not affect the fatigue response, maintaining the fracture stress in 500 MPa, whereas the rutile phase caused a decrease to 450 MPa.

Resumo em Inglês:

The characterization of materials is an area of extreme importance for engineering, it uses a range of instrumental techniques to provide an information bank for material analysis and selection. In the treatment of iron ore the mineralogical characterization is done, almost exclusively, by optical microscopy. However, materials with very fine granulometry, below 4 µm, make their preparation and visualization restricted in this equipment. The present work aims to identify the minerals Hematite, Magnetite and Goethite in samples of tailings from the iron ore processing, employing a Bartington MS3 that evaluates the magnetic susceptibility as a function of the temperature. These measurements make it possible to identify Curie temperatures characteristic of Magnetite (580 °C) and Hematite (675 °C), as well as Goethite's Neel temperature (120 °C). The results showed that the application of the technique is of great value for the identification of the magnetic bearing minerals and the quantification of the magnetic potential of the sample.

Resumo em Inglês:

Connectors used in electrical power distribution systems should allow the passage of electricity continuously and without interruption. However, this does not always occur due to failure caused by improper assembly and/or corrosion of the materials employed, which reflects the quality of service. Notable among the new detection technologies that have been studied to facilitate the identification of defects is the use of thermochromic materials, which allow the easy identification of "hot spots", without the need for specialized equipment and personnel. In this context, in this study, the performance of a thermochromic liquid crystal was evaluated with the aim of developing a temperature sensor for connectors used in electrical power distribution networks. For the evaluation of the performance, thermal and ultraviolet radiation degradation tests were conducted, as well as analysis using spectroscopic (FTIR, FTIR-HATR, UV-Vis, 1H NMR) and thermal (DSC, PLM) techniques. The results indicated that the liquid crystal and the associated components showed no degradation under the test conditions, as well as a good color stability was observed, verifying the viability of the use of these materials for the construction of a temperature sensor. A field test was performed with the devices and was effective for the suggested application.

Resumo em Inglês:

The main aim of this paper was to evaluate ceramic products containing a percentage of ash from sheep wool waste through drying linear shrinkage from a small brickyard in Bagé - RS. The ash percentages used in the formulation were 0, 5, 10, 20 and 30%. Raw materials were analyzed by Energy Dispersive X - ray Fluorescence (XRF/EDX). The methods used to shape the ceramic products were vacuum extrusion and pressing. After shaping, the ceramic products were dried in laboratory conditions with an average temperature of 21°C for 3 weeks and later in an oven at 110°C for 48 h. The drying linear shrinkage test was performed according to the specifications of standard C-021/95, and its average results for all formulations were 8.2% and 0.7%, for the extruded and pressed products, respectively. The results of drying linear shrinkage were higher for the extruded products than for the pressed ones, showing that the addition of the ash from the sheep wool waste in the clay decreased the drying linear shrinkage in the extruded ceramic products.

Resumo em Inglês:

The strain hardening behavior of an AISI 304 stainless steel at different temperatures was investigated in this work. Specimens were tensile tested up to rupture at temperatures of 25, 50, 75, 100, 125 and 150 ºC by using a universal testing machine with an attached environmental test chamber. The induction of martensite by strain was assessed by X-ray diffraction and Rietveld refinement. The resultant fracture morphologies were analyzed by scanning electron microscopy. The changes in the mechanical properties as a function of temperature were evaluated through the variations in the stress-strain curve and the strain hardening behavior was described in terms of strain hardening rate, instantaneous strain hardening exponent and Crussard-Jaoul analysis. Six strain hardening stages were detected at lower temperatures, transitioning into three strain hardening stages at higher temperatures. Fracture surface was ductile at all studied temperatures, although differences in terms of dimple and void morphology were observed.

Resumo em Inglês:

One of the most studied deleterious phases in stainless steels is the sigma phase, due to its high potential to decrease the toughness and corrosion resistance of these steels. Eight samples of as-received cold rolled UNS S32205 duplex stainless steel were submitted to isothermal heat treatments at 850 oC during 10, 15, 30, 60, 120, 180, 240, and 300 minutes in order to study the precipitation kinetics of the sigma and chi deleterious phases. Several complementary microstructural analysis techniques were used to determine the volume fraction of the intermetallic phases, including optical microscopy and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). Evaluation was made of the kinetics of isothermal formation of sigma and chi phases in commercial duplex stainless steels (UNS S32205). The results indicated two different mechanisms for sigma phase precipitation: sigma phase formed from the chi phase for shorter isothermal heat treatment times, and sigma phase precipitated at the ferrite-austenite interface for longer isothermal heat treatment times, using a temperature of 850 oC. The phase transformation kinetics determined using the JMA equation indicated that chi phase precipitation caused faster sigma phase formation.

Resumo em Inglês:

Shear tests using a coaxial cylinders viscometer were performed in order to determine the rheological and thixotropic properties of xanthan gum dispersions with sodium bentonite in the presence of high salt concentrations of sodium and calcium chlorides. The dispersions rheology with different temperatures and concentrations of NaCl, CaCl2 and xanthan gum were prepared by fixing the bentonite concentration of 1%. The dispersions showed a good fit to power law model through linear regressions with the lowest coefficient of determination value of 0,98. A screening was made initially to decide which independent variables potentially affect the rheological and thixotropic parameters. The independent variables were temperature, the xanthan gum and sodium and calcium chlorides concentrations. Then a full factorial design in duplicate with the remaining variables on the same tracks was performed. The results eliminated calcium chloride as an independent variable and revealed a strong dependence of the rheological and thixotropic parameters with temperature and xanthan gum and NaCl concentrations.

Resumo em Inglês:

Several studies of biodegradable polymers and copolymers have been carried for different applications in the biomedical area. This current study aims to develop a biocomposite to be used as an orthopedic device, using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) P(HB-HV), a biodegradable copolymer, with 94%HB and 6%HV, as matrix; and nanodiamonds (ND) with primary grains of 4-6nm, as reinforcement. The nanodiamonds were previously encapsulated by P(HB-HV) and specimens were prepared using a hydraulic press and injection molding machine, in order to evaluate which method presents a better performance. Thermal and mechanical analyses were done to compare their behavior. The biocomposite and pure P(HB-HV) samples were analyzed by flexural testing, nanoidentation, DMA, XRD, TGA. The distribution of nanodiamonds on the specimen fracture surface were investigated by SEM. The SEM micrographs allowed us to concluded that the encapsulation of nanodiamonds by P(HB-HV) was successfully performed, promoting a better interface and distribution in the polymeric matrix. The presence of ND in the polymeric matrix decreased the P(HB-HV) crystallinity, inhibiting the crystallite growth. The mechanical properties obtained from flexural test, nanoidentation and DMA of the injection-molded specimens were superior to compression-molded, due to its homogeneous and continuous structure. In vitro analysis was performed to evaluate the samples cytoxicity.

Resumo em Inglês:

Phosphorylation of starch has resulted in appreciated material properties for applications in drug matrices. This study aimed to obtain and characterize samples of phosphorylated starch with sodium trimetaphosphate (STMP) and sodium tripolyphosphate (STPP). SEM micrographs allowed evidence that in relation to the starch in natura, the samples showed a loss of grain form in addition to formation of particle agglomerates. X-ray diffractograms of these samples indicated amorphization process, with modifications of the peaks in the region between 15 and 20 º 2θ. FTIR spectra of phosphorylated samples showed variations and new bands related to phosphorylation. Through of methylene blue adsorption isotherms it was observed better adjustment adsorptions on phosphorylated sample to Freundlich model. The new biomaterials showed adsorptive capacity of model cationic nature drug, demonstrate potentiality to application in controlled release systems.

Resumo em Inglês:

This paper describes the development of TiO2 and ZnO particles by a chemical route, using two different wet synthesis methods: polymeric precursor (PP) and sol-gel (SG). This study aimed to shed a light on how the synthesis method affects the photocatalytic activity of these oxides. Rhodamine B (RhB) degradation was used as a probe reaction to test the as-synthesized TiO2 and ZnO photoactivity. It was observed that surface availability, which is related to the presence of synthesis residue, is the key parameter to determine photoactivity. ZnO PP and ZnO SG presented degradation of 88% to RhB. Both samples presented synthesis residue on the surface. On the other hand, TiO2 PP presented a better performance than TiO2 SG, once 90% of RhB was degraded, while TiO2 SG degraded 80% of the dye. In this case, TiO2 PP was free of synthesis residue on the surface, while TiO2 SG presented residues.

Resumo em Inglês:

A biocompatible and biodegradable hybrid chitosan/glycerol phosphate hydrogel (CS-GP) was prepared and evaluated as support for enzyme immobilization. In this work a lipase sn-1,3 specific from Rhizopus oryzae was physically immobilized in CS-GP by adsorption (PA) and in CS-GP modified chemically with glutaraldehyde (CS-GP-GA) by covalent attachment (CA). The matrices (pure and chemically modified) and immobilized lipases were characterized by scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetric (TG) analysis. Moreover, a comparative study between free and immobilized lipase was provided in terms of pH, temperature, kinetic parameters and thermal stability. The catalytic properties of biocatalysts were assayed in olive oil hydrolysis. The maximum activities were found at 60◦C/pH 8.5 and 50◦C/pH 7.5 for lipase immobilized by PA and CA, respectively. Both immobilization process turned biocatalysts highly active, since they were stable for 120 days at low (-10◦C) temperatures and around 2-fold more stable than free lipase at 60◦C (high temperature). Thus, results revealed the potential application of chitosan/glycerol phosphate hydrogel (CS-GP) as matrix for lipase immobilization. Nevertheless, better performance was achieved when the lipase was immobilized by covalent attachment.

Resumo em Inglês:

More and more electronic devices are being produced and most of them are disposed of improperly. In addition, as they contain heavy metals and toxic substances in their composition, the environmental impact increases. This work aims to study the recycling of polymers present in e-waste through the mechanical characterization of polymer blends produced with the main polymers present in printers. To do so, printers were dismounted, the material of the components was classified, and the main polymers were processed. The sample consisted of 20 printers, from which HIPS-90%/PS-10%, HIPS-90%/ABS-10% and HIPS-100%, blends were processed by extrusion and injection of specimens with tensile test geometry. The tensile strength was 39.0 MPa for HIPS/ABS, and 37.5 MPa for HIPS/PS. Despite having slightly different mechanical properties, probably due to possible variations in their chemical composition, the formulations have good quality and potential for use in new products such as hangers, organizing boxes, soles and, watering cans.

Resumo em Inglês:

The paper industry primary waste is usually deposited in landfills or incinerated. This material has a high content of lignocellulosic components, which could be converted to cellulose nanostructures (CNS). This study aimed to compare compositional (Fourier transform infrared spectroscopy), thermal (thermogravimetric analysis), morphological (scanning electron microscopy) and dimensional (dynamic light scattering and atomic force microscopy) properties of CNS obtained through chemical and mechanical isolation processes. The FTIR results showed similar chemical bonding for both nanostructures, which indicated presence of cellulose and lignin. Their average size was 170 nm and 209 nm for chemical and mechanical processes, respectively. The morphology of SEM images showed a compact structure and the chemical isolation presents smaller CNS agglomeration than mechanical. TGA results showed higher thermal stability for CNS-chemical than CNS-mechanical samples and AFM images indicate the CNS morphologies, which showed nanoroads for CNS-chemical and nanoneedles for CNS-mechanical.

Resumo em Inglês:

Electrical discharges in liquids are currently used to synthesize nanoparticles. The plasma-liquid interaction is complex, where parameters such as electric field, ion charges and other species present are important. In order to understand the mechanism of crystallization, mother liquor (saturated solution of NaCl, MgCl2 and KCl) was used to study the effectiveness and selectivity of the crystallization caused by the application of plasma. Discharge was applied with the solution at room temperature or during cooling. X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and chemical analysis was used to evaluate the structure and composition effects on crystal structure and composition. It was observed that the discharge induces selectively crystallization, and when compared to crystals obtained conventionally by cooling, were smaller and more uniform. We therefore confirm that plasma in liquid can also be used to selectively crystallize materials in atmospheric pressure, where the sizes of the crystals must be dependent on the parameters used.

Resumo em Inglês:

Co-Ni/SiC nanocomposite coatings were obtained by codeposition of SiC nanoparticles in a bath with nickel and cobalt, using API 5L X80 as the substrate. The influence of cathodic current density on deposit properties was investigated. Measurements of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP) were performed in 3.5 wt% NaCl solution to investigate a corrosion performance. The morphology and chemical analysis of the surfaces were analyzed by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) and related with micro-hardness and X-ray diffraction (XRD). The results indicate which composite coatings have acicular morphology, with higher micro-hardness values than those found for the carbon steel substrate. The Co-Ni/SiC coating increased the corrosion potential and the resistance to polarization, which resulted in lower corrosion rates than those obtained without uncoated steel.

Resumo em Inglês:

Stainless steels are well known by their corrosion resistance. The austenitic types, in particular, are also applied as structural components in engineering systems operating at high temperatures such as nuclear reactors, petrochemical furnaces and turbines. For these applications operational temperatures may go up to 800ºC. Under constant load applications the main mechanism of failure, which would limit the material's life, is creep. In the present work creep parameters were evaluated in the high temperature interval of 600 to 800ºC for an AISI 316 austenitic stainless steel. Dislocation substructures were observed by transmission electron microscopy in creep ruptured specimens. Two distinct mechanisms of dynamic strain aging and dynamic recovery associated with different values for the power law exponent n and the Arrhenius activation energy Q for creep were verified below and above 700ºC, respectively.

Resumo em Inglês:

Geopolymeric materials have some unique properties such as early-high compressive strength, durability, resistance to acids and sulfates, ability to immobilize toxic and radioactive compounds, low porosity and high temperature resistance. These materials are strategic for sustainable development and are a suitable alternative to Portland cement. The use of phyllite as a geopolymer precursor is encouraged by its abundance, low cost, and the fact that it is already applied in ceramic industries as a kaolin substitute. The objective of this paper is the physicochemical characterization of geopolymeric resin using two pulverized phyllite rocks as precursors with STEM, XRD and XRF techniques. It was found that both phyllite rocks studied have a high quartz content of approximately 50% (weight), which have a "filler" function in the microstructure of the resin helping stabilize residual tensions after curing. Kaolinite and muscovite minerals are present in up to 40% (weight) and are responsible for the high compressive strength of the geopolymer resins.

Resumo em Inglês:

The Ni57Nb33Zr5Co5 metallic glass is a promising alloy for bipolar plates in proton exchange membrane fuel cells. It is important to know which phase forms in this alloy under different cooling rates in order to understand its influence on the thermal stability and mechanical properties. In this work, melt-spun ribbons and rod samples with 1, 2 and 3 mm diameters were prepared and their phase formation, microstructure and mechanical properties were investigated by X-ray diffraction, differential scanning calorimetry, optical microscopy, scanning electron microscopy and microhardness. It is found that a completely crystalline structure forms in the lower cooling rate samples (2 and 3 mm diameter rods) with the presence of the equilibrium phases Ni3(Nb,Zr) and Nb7Ni6 as primary phases or as a very fine eutectic structure, while a fully glassy structure is attained in the samples with the highest cooling rate (ribbons). For the sample with an intermediate cooling rate (1 mm diameter rod), polymorphically crystals of an unknown metastable phase with spherical morphology precipitate in the glassy matrix with virtually the same composition as the matrix. The 2 mm diameter sample exhibits higher hardness than the other samples, which is attributed to its very fine eutectic colonies.

Resumo em Português:

Laser cladding of vanadium carbide powder developed an interlayer on AISI D6 steel as a diffusional barrier and to relief thermal residual stress. Laser cladding experiments varied resolution (DPI) and scanning speed (mm/s). CVD diamond deposition on this interface went on by HFCVD technique. The coatings were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM-FEG) and Raman spectroscopy. Ordered state V8C7 phase prevailed in the interlayer. The thickness of heat-affected zone (HAZ) and Laser Cladding Vanadium Coating (LCVC) were 37 µm and 5 µm, respectively, in the best layer produced. The diamond film showed good quality and morphology. The Raman peak at 1342,13 cm-1 shows the residual stresses level undertaken at the film-substrate interface and the corresponding adhesion, demonstrating the suitability of the VC laser cladding process to CVD diamond films deposition.

Resumo em Inglês:

Magnesium aluminate can be obtained by the methods: ceramic method, sol-gel, co-precipitation, hydrothermal and combustion. However, this work presents a simple and low cost route to obtain MgAl2O4 through the gelatin method. The main objective was to use gelatin as an organic precursor and to verify the influence of temperature and time of calcination on the structural and morphological properties of obtained materials. Al and Mg nitrates were used as metal precursors with Al/Mg = 2 ratio. Samples were calcined as follows: 700 ºC, 900 ºC and 1100 ºC during 2 and 4 h. The powders were characterized by TGA, XRD and SEM. A single phase material with a crystallinity of 39.18 - 90.40% and crystallite size in the range of 12.4 to 55.5 nm was obtained. The materials exhibited morphology in the form of plates and small agglomerates. It was found that increasing temperature and time of calcination favored the growth of crystallites and increased crystallinity.

Resumo em Inglês:

Techniques for shock consolidation of powders have been developed for different purposes, including the synthesis of diamond from carbon powder. In this work, a new device configuration for dynamic consolidation is proposed. It consists of three coaxial tubes, with a conical cover made of explosive at the top of the device. The inner tube contains the powder to be compacted. The second is accelerated towards the first in order to promote its collapse. The third confines the explosive. A conical cap at the top of the device triggers the explosive. For a preliminary evaluation, two types of explosives, TNT and Composition B, were used. Preliminary analytical results by the impedance matching method indicate that maximum pressures of 35.44 GPa and 48.16 GPa could be achieved using TNT and Composition B, respectively. Maximum temperatures around 1,600 K and 2,500 K for TNT and Composition B, respectively, are expected. These pressure and temperature values are adequate for transforming graphite into diamond. Preliminary Rietveld refinement indicated that nanodiamond is a fraction of approximately 54% of the detonation resulting powder.

Resumo em Inglês:

Geopolymers may be described as solid and stable synthesized aluminosilicate materials, whose properties are generally believed to provide a superior durability behavior. The work in hand presents the results of an experimental investigation on the thermomechanical behavior of geopolymer matrices composed by metakaolin (MK), silica fume (SF) and blast furnace slag (BFS). The alkaline activator solution consisted of sodium silicate and sodium hydroxide. The use of different aggregates was also investigated, by replacing natural sand with chamotte. Samples were submitted to different temperatures at predetermined intervals to a maximum of 1000ºC. Compression tests were performed, before and after the exposure to elevated temperatures. X-ray diffraction, thermal analysis (TGA and DTA) and scanning electron microscopy (SEM) were used to investigate the microstructural characteristics of the studied materials. The results showed that the presence of BFS in the geopolymer mixture significantly increases its mechanical response. However, the incorporation of SF presents inferior behavior in regular conditions and when exposed to elevated temperatures. The replacement of sand with chamotte results in higher compatibility above 500ºC, when a better tolerance to extreme environmental temperature conditions was observed.

Resumo em Inglês:

Aluminium alloy Al-Si5Cu3 (319) is one of the most commonly used casting alloys for automobile components, due to its casting characteristics. Iron is the major impurity element that influences the detrimental β-phase formation in secondary aluminum alloys. In the present study, we investigated the influence of the cooling rate on the formation of iron compounds, α-Al15(Mn,Fe)3Si2 and β-Fe5AlSi phases, in Al-Si5Cu3 containing 1.0% Fe, 0.5% Mn and 0.2% Mg, by thermal analysis and metallography. The results show that the high cooling rates, between 10-103 K/s, are able to reduce and nullify the formation of needle-like β-Al5FeSi phase, and help the formation of the Chinese scripts α-Al15(Fe,Mn)3Si2 phase. The analysis of the curves reveals that the increase of the cooling rate increases the temperature of nucleation of the α-Al dendrite and decrease the eutectics Al-Si and Al-Cu phases.

Resumo em Inglês:

Duplex stainless steels (DSS) are Fe-Cr-Ni-Mo alloys, with low carbon content, which have a favorable combination of mechanical properties and corrosion resistance. These characteristics are mainly attributed to a dual phase and refined microstructure, typical of these alloys, consisting of similar amounts of ferrite and austenite. For this reason, DSS are widely used in various segments of industry, especially in offshore applications. However, DSS components may have a decrease of their properties when they are exposed high temperatures, often due to incorrect manufacturing processes. Intermetallic phases may precipitate causing embrittlement and corrosion resistance decrease. This work presents the effects of short time aging at 475 °C on the mechanical properties and localized corrosion resistance of a cast DSS. The results show that mechanical properties, such as toughness and hardness, are more susceptible to aging, having already been affected during the first 4 hours of heat treatment, while the corrosion was affected in 12 h of aging.

Resumo em Inglês:

It is well known that titanium alloys have mechanical strengths comparable to steels, as well as high corrosion resistance. Also, they have the advantage of promoting osseointegration, when used in medical and dental implants. This work aims to describe the adhesion properties of fibroblast and osteoblast cells on the surface of titanium aluminum vanadium alloy (Ti6Al4V). Three different conditions of the surface were investigated: smooth, rough and covered with diamond film. Conventional material characterizations were performed to the film which consisted in: Morphological visualization by scanning electron microscopy, confocal profilometry, X-ray diffraction pattern, Raman backscattering spectroscopy and atomic force microscopy. Biocompatibility tests of Ti6Al4V were performed using primary human fibroblasts and mouse pre-osteoblasts cell line MC3T3-E1. Overall, diamond films deposited on Ti6Al4V showed interesting results of uniformity and protection against cracks on to the surface, reasonable biocompatibility features if compared to uncovered ones, indicating that this film is an alternative for using in health care applications.

Resumo em Inglês:

The final properties of thermosets are strongly dependent on their curing process. Therefore, closely monitoring this process is necessary to assure the manufacturing quality and productivity. In this way, the aim of this study is to develop a simple dielectric module for monitoring and optimizing the industrial curing cycle of thermosets. The module is based on a data acquisition system and an interdigital sensor that remains in contact with the resin throughout the entire curing process. Dielectric analysis (DEA) was performed in a commercial epoxy resin formulation widely used as a matrix for thermoset composites, which was submitted to a pre-established and validated curing cycle. The properties derived from DEA measurements are in accordance with differential scanning calorimetry (DSC) results, allowing the identification of key stages of the curing process. The similarity between the results of both techniques is a strong indicative of the possibility of using the developed module as an alternative for industrial cure monitoring and optimization.

Resumo em Inglês:

This study seeks to evaluate the effect of intermediate annealing on the microstructure, texture, and formability of Nb-stabilized ferritic stainless steel. Two routes - direct cold rolling and cold rolling with an intermediate annealing were performed. The total reduction was 80%, 3-0.6 mm and 3-1.2-0.6 mm. The characterization of the samples was conducted using X-ray diffraction, electron backscatter diffraction, and tensile tests to evaluate the formability by the average normal anisotropy coefficient, r value. The results showed that intermediate annealing promoted the strongest γ-fiber with peak at {111}〈112〉 and weak α-fiber after cold rolling. After the final annealing, it was observed that intermediate annealing reduces the banded microstructure and θ-fiber, and improves the γ-fiber uniformity and the r value. It is worth noting that the γ-fiber fraction was the same for direct reduction. The increase in r value was related to the reduction in θ-fiber and the uniformity of texture recrystallization.

Resumo em Inglês:

Poisson's ratio and birefringence, both measured by ultrasound, are used to follow the evolution of the anisotropy in ASTM A-36 steel plates cold-rolled between 5 and 50% deformation, and then subjected to recrystallization at 900 and 1000 ºC. Times of flight of longitudinal and shear waves along the thickness of the plates were measured. As orthotropy increases, both birefringence and the difference between Poisson's ratios measured using a shear wave polarized along the length and another wave polarized along the width of the plate, are linearly related to the degree of deformation and cold-rolled hardness. In addition, the ultrasonic methods used clearly detected the complex changes in anisotropy produced by the austenization and recrystallization heat treatments. Thus, Birefringence or Poisson's ratio, measured by ultrasound, can be used to follow-up nondestructively changes in the anisotropy of rolled plates as a function of both, degree of deformation and recrystallization heat treatment.

Resumo em Inglês:

Nickel ferrite/multi-walled carbon nanotubes (NiFe2O4/MWCNTs) composite has been rapidly synthesized via microwave irradiation technique. The structural properties of the product was investigated by X-ray diffraction (XRD), N2 adsorption/desorption isotherms, thermogravimetric analysis (TGA), Raman spectroscopy and, scanning electron microscopy (SEM). Catalytic behavior of the composite material on the advanced photo-Fenton degradation of Amaranth dye was evaluated. The synthesis conditions employed on the microwave system were: temperature (235 °C), power (500 W), pressure (600 psi) and irradiation time (30 min). Characterization results showed the formation of hybrid material, containing a predominantly microporous structure, with surface area and total pore volume of 54 m2 g-1 and 0.2249 cm3 g-1, respectively. The composite exhibited higher catalytic activity compared to the pure NiFe2O4, reaching 100% of decolorization at 60 min of reaction, which can be attributed to a synergism between NiFe2O4 and MWCNTs. Therefore, NiFe2O4/MWCNTs composite can be used as a promising photo-Fenton catalyst to degrade Amaranth dye from aqueous solutions.

Resumo em Inglês:

In the last ten years, stannates with perovskite structure have been tested as photocatalysts. In spite of the ability of perovskite materials to accommodate different cations in its structure, evaluation of doped stannates is not a common task in the photocatalysis area. In this work, Fe3+ doped BaSnO3 was synthesized by the modified Pechini method, with calcination between 300 and 800ºC/4 h. The powder precursor was characterized by thermogravimetry after partial elimination of carbon. Characterization after the second calcination step was done by X-ray diffraction, Raman spectroscopy and UV-visible spectroscopy. Materials were tested in the photocatalytic discoloration of the Remazol Golden Yellow azo dye under UVC irradiation. Higher photocatalytic efficiency was observed under acid media. As no meaningful adsorption was observed at this condition we believe that an indirect mechanism prevails. Fe3+ doping decreased the band gap and favored the photocatalytic reaction, which may be assigned to the formation of intermediate levels inside the band gap.

Resumo em Inglês:

Styrene-ethylene/butylene-styrene (SEBS) copolymer- based thermoplastic elastomers (TPE) are applied in the production of household items used in places with conditions for microbial development. Metal oxides like zinc oxide (ZnO) and others can be added to the TPE composition to prevent microbial growth. The aim of this study is to evaluate the effect of thermal accelerated ageing on mechanical, chemical and antibacterial properties of SEBS-based TPE containing 0%, 1%, 3%, and 5% zinc oxide. Zinc oxide was characterized by laser diffraction, X-ray diffraction, superficial area, porosity and scanning electron microscopy. Both aged and unaged samples were analyzed by infrared spectroscopy, tensile at rupture, elongation at rupture, hardness and antimicrobial activity against Escherichia coli and Staphylococcus aureus. Following thermal exposure, a reduction of antimicrobial activity was observed. No significant difference was observed in the chemical and mechanical characteristics between aged and unaged samples.

Resumo em Inglês:

In copper-based shape memory alloys (SMAs), some exceptional phenomena, such as the shape memory effect (SME) or superelasticity (SE), are observable. However, commercial aluminum bronzes, Cu3Al-based alloys, do not present these functional properties (SME and/or SE) in their original state. Thus, since one of the main copper-based SMA systems is the Cu-Al-Ni alloy, this paper aims to analyze the modification of these commercial aluminum bronzes to SMA by the addition small amounts of Cu, Al and/or Ni. These modified bronzes were reprocessed by induction melting and injected by centrifugation into a ceramic coating mold. The modifications were made to determine the nominal composition for a Cu-13,0Al-4,0Ni (%wt) SMA. The effectiveness of the modifications was verified by differential scanning calorimetry (DSC) thermal analysis. All modified Cu-Al-Ni bronzes presented DSC peaks of the thermoelastic martensitic phase transformation, showing that SMA behavior was achieved, while the non-modified bronzes revealed no transformation. These results were supported by Vickers hardness (HV), X-ray diffraction (XRD), semi quantitative composition by EDS analysis and optical microscopy.

Resumo em Inglês:

Titanium oxides such as rutile and anatase, are materials that stand out for exhibiting properties that act in biomedical and photocatalytic applications, among others. It is extreme importance to idealize new techniques that produce such compounds, being indispensable the improvement of characterizations for these materials. For this purpose, titanium comercially pure (CP) grade II cylindrical samples were oxidized ionically using titanium cage electric shields, oxidized at 350 ° C in 3 and 8 hours. Through Grazing Incidence X-ray Diffraction (GIXRD) analysis, was observed on the surface of the treated samples the formation of a TiO2 film with the anatase, rutile and brookite phases, the latter phase cited being difficult to produce in conventional thermochemical treatments. All samples treated showed a significant increase in wettability using distilled water. The higer value was for the sample with a 8 hours treatment time, in which this condition presented phases with greater intensity in the analysis of GIXRD

Resumo em Inglês:

In order to determine if heat treatments can be discerned by nondestructive ultrasonic testing, samples of SAE 1045 and SAE 4140 steels were subjected to the classical heat treatments of annealing, normalizing, quenching, and quenching and tempering, and their elastics constants, Young's, shear and Poisson's moduli, were monitored by ultrasound. Results show that the microstructural differences associated to the various heat treatments generate differences on the elastic constants that can be effectively discerned by the use of longitudinal and shear ultrasonic waves. Special attention is given to Poisson's modulus, since for its determination only times of flight of longitudinal and shear ultrasonic waves, and not the distance the waves travel, are required, which is of quite practical importance, since measurements are simplified and a fundamental source of error is eliminated. It is thus shown that the microstructural evolution of a steel part subjected to heat treatments can be monitored by this simple ultrasonic method.

Resumo em Inglês:

Thermoplastic starch properties depends of plastification process. The aim of this study was to analyze the effect of concentration of glycerol and water on plastification, glass transition temperature (Tg) and tensile properties of thermoplastic waxy starch (TPWS). Formulations were extruded in the following concentrations of starch/glycerol/water: 70/30/0 (TPWS 0%); 70/25/5 (TPWS 5%); 70/20/10 (TPWS 10%) weight percentage. Crystalline peaks in WAXS diagrams and native grains present in SEM micrographs showed that the TPWS 0% and 5% were not sufficient to promote total plastification of the waxy starch, and TPWS 10% showed the higher starch plastification. Tg measurements by DMTA were 30 ºC to TPWS 0%, 23 ºC to TPWS 5% and 40 ºC to TPWS 10%. These results showed that glycerol and water had effect plasticizer in TPWS 5% and antiplasticizer in TPWS 10%. Mechanical tensile results showed that higher tensile strength was observed in the systems with more effective starch plastification.

Resumo em Inglês:

This paper presents an evaluation study of wastes from pulp and paper as well as construction and demolition industries for application in cement-based materials. The alternative raw materials were used as a source of calcium carbonate (CaCO3) and as pozzolanic material (water-reactive SiO2) in partial replacement of Portland cement. In addition to the hydraulic binder, coating mortars were composed by combining the pulp and paper fluidized bed sand residue with construction and demolition wastes, both added as small aggregates. Rheological and mechanical characterization showed that the waste additions changed the behavior of the cement materials, increasing both the viscosity of the pastes (at constant shear stress or rate). The formation of agglomerates in the cement hydration process made the mortars with additions of residues (lime and ash sludge) have an increase in the mechanical strength of the hardened bodies when compared to the mortar (M0W) prepared only with the residues (fluidized bed sand and C & D) as aggregates.

Resumo em Inglês:

Conventional stainless steels are used in cyclic oxidation, but the high amount of Cr and mainly Ni increase the price of these alloys. The objective of the present study was to assess the cyclic oxidation resistance of FeSiCrNi and FeMnSiCrNiCe alloys in comparison to AISI 304 and AISI 310 stainless steels by evaluating the oxidation kinetics and using characterization techniques to determine the oxides formed. The alloys were melted in induction furnaces and cast in sand molds. Cyclic oxidation tests were carried out in an automated oven in cycles of one hour for heating and maintenance at high temperature (850, 950 or 1050 °C) and 10 minutes for cooling. To characterize the oxidized layers, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) analysis were performed. The oxidation kinetics were determined. The results showed that the studied alloys presented better results than AISI 304 at 850 °C, but at 1050 °C, AISI 310 presented the best results. At 950 °C, the FeSiCrNi alloy presented layer detachment and FeMnSiCrNiCe presented a higher rate of mass variation than AISI 310, both without oxide detachment. For both alloys, formation of chromium and manganese oxides with parabolic rate of mass gain occurred.

Resumo em Inglês:

In this work, composite coatings of Cu/AlO(OH) were produced by electrodeposition on steel substrates using a pyrophosphate-based bath containing allyl alcohol as an additive. The electrodeposition of the composite coatings was carried out using a 23 central composite design (CCD), aiming to verify the effects of the deposition parameters (previous stirring time (t), the stirring speed (S) and the current density (j)), considered the entry variables, on the electrochemical behavior of Cu/AlO(OH) coating, the response variables of the CCD. The results indicated that a decrease of the parameters j and S directly influenced the values ​​of Rp and Rct, leading to the production of protective coatings. The best result (Rp = 211 Ω and Rct = 221 Ω) was obtained under conditions where t = 120 min, S = 1300 rpm and j = 7 A m-2. Dispersed bohemite particles could be noted on the surface of the composite coating.

Resumo em Inglês:

Individual carbon nanotubes (CNTs) exhibit excellent mechanical, electrical and thermal properties, leading to development of a new generation of advanced lightweight materials and spacecraft electronics substituting the electronics based on silicon. The direct assembly of CNTs into macroscopic fibers or sheets has been a way to overcome their dispersion and processing challenges. Because of a wide range of applications of this material, we investigate effectively the defects on CNT yarns structures created by electron beam and gamma sources and their impact on the morphology and mechanical properties. The irradiated samples with electron beam at doses of 400, 600 and 800 kGy had a decrease in the strength from 219.60 ± 18.90 MPa for pristine yarn to 108.86 ± 23.77, 153.15 ± 21.63, 170.50 ± 25.78 MPa, respectively. The sample irradiated with gamma in air at dose of 100 kGy had the strength increased slightly as compared with the pristine sample and an increase in the elasticity modulus from 8.79 ± 1.19 to 19.63 ± 2.02 GPa as compared to CNT pristine yarn. The quality of the CNT yarns that was gamma irradiated in air with absorbed dose of 100 kGy was not affected by the radiation process with improvement of 123% of the Young’s modulus.

Resumo em Inglês:

The aim of this work was to study the incorporation of lead containing TV tube glass waste as a method to provide alternative raw material for aluminous electrical porcelain. For this purpose, aluminous porcelain formulations containing up to 30 wt.% of TV tube glass waste as a replacement for traditional flux material (sodium feldspar) were pressed and fired in air at 1300 ºC using a fast-firing cycle (< 60 min). X-ray diffraction (XRD), scanning electron microscopy (SEM), linear shrinkage, apparent density, water absorption, and electrical resistivity have been carried out. The results indicated that the aluminous porcelain pieces containing up to 30 wt.% of TV tube glass waste rich in PbO with water absorption between 0.42 and 0.45% and volume electrical resistivity between 1.91 and 2.93 x 1011 Ω.cm have high potential to work as electrical insulator material. This use of lead containing TV tube glass waste can contribute greatly to reducing the environmental impacts related to it, and also save the sources of non-renewable raw materials used in the electrical porcelain sector.

Resumo em Inglês:

Natural fiber reinforced polymer composites have recently been investigated as a component of multilayered armor system (MAS). These composites were found to present advantages when replacing conventional high strength synthetic aramid fabric laminate composite (KevlarTM, with same thickness, as MAS second layer. Continuous and loose natural fibers were up to now mostly used to reinforce these ballistic composites. Only two natural fabrics reinforced polymer composite were so far used with same purpose. Therefore, this work investigated the possibility of substituting KevlarTM for three other natural fabrics, based on mallow and jute fibers, as reinforcement of epoxy composites. Fabrics made of either pure mallow, or 70%mallow/30% jute or 50%mallow/50% jute fibers were separately mixed with epoxy to produce laminate composite plates. These plates were set as second layer of Al2O3/Nb2O5 front ceramic MAS, that were ballistic tested against relatively high energy 7.62 mm ammunition. Indentation depth values caused by the bullet penetration in clay witness, simulating human body behind the MAS, were always found to be below the safety standard limit. These indentation values were similar to those obtained in MAS with KevlarTM as second layer. However, significant economical advantages favor the investigated natural fabric composites over the synthetic Kevlar.

Resumo em Inglês:

Biomedical devices currently in use (prostheses, implants) have satisfactory performance in many cases. However, sometimes the body reacts to the device insertion and may lead to its rapid replacement. Some of these disadvantages can be solved by the use of titanium and its alloys, due to their excellent combination of corrosion resistance, wear resistance and biocompatibility compared to other competing biomaterials. This paper presents the possibility of obtaining near beta titanium alloy with ultrafine grains produced by severe plastic deformation. For this, the Ti-13Nb-13Zr alloy was processed by high-pressure torsion processing method. Samples were processed with different loads and number of turns. After characterization, it was observed that after applying three turns, a load of 1GPa produces more Ti-beta phase than a load of 6 GPa. However, as expected, the larger the load, the higher the refinement.

Resumo em Inglês:

In the present study, poly (ethylene terephthalate)-based composites were produced and characterized. These composites were composed by poly (ethylene terephthalate) (PET) reinforced with geopolymer concrete waste (GCW). Both untreated (U-GCW) and treated with oleic acid (OA) geopolymer concrete waste (T-GCW) were used in the production of the composites. The PET/GCW ratios used for either treated or untreated GCW bodies were 80/20 (wt%), 60/40 (wt%) and 50/50 (wt%). Chemical compositions were assessed by X-ray fluorescence spectroscopy (XRF), crystallinity by differential scanning calorimetry (DSC), thermal stability by thermogravimetry (TGA), microstructure by field emission gun scanning electron microscopy (FEG-SEM) with energy dispersive X-ray spectroscopy (EDS), and mechanical properties were assessed by compression tests. Fourier transform infrared spectroscopy (FT-IR) was used to check the efficiency of the treatment with OA, as well as the interaction between PET and GCW. The T-GCW PET composites showed better thermal, physical, and mechanical properties, for non-structural applications, when compared to U-GCW.

Resumo em Inglês:

The interval of existence of dynamic strain aging (DSA) in AISI type 304 austenitic stainless steel subjected to quasi-static tension tests, under strain rates from 3.5 x 10-2 to 3.5 x 10-4 s-1, in the temperature range from 25 to 800ºC was investigated. It was found that DSA occurs in the range extending from around 200 to 700ºC. Plastic instabilities associated with serrations, Portevin-Chatelier effect, allowed activation energies to be calculated and a possible mechanism of dislocation interaction with interstitial carbon atoms to be proposed. Significant increase in the ultimate strength, uniform elongation and work hardening demonstrate that DSA is a relevant phenomenon, which improves the high temperature mechanical properties of 304 steel.

Resumo em Inglês:

This work presents a study of TiO2 thin films prepared by sputtering, for using as protection for biofouling action on marine structures. Titanium oxide thin films were prepared with different amount of oxygen on the surface of regular 1020 steel, a structural material for marine technology. The cristalline structure analysis evidenced the formation of anatase and rutile phases, as well as an amorphous phase of titanium oxide. Roughness measurements shown that the surface finish can contribute to the fixation of microorganisms. The crystalline TiO2 thin films was evaluated as a potential biofouling protective coating. Contact angle measurements revealed that under UV-C light, the material evidenced a changing in wettability from hydrophobic to hydrophilic behavior, what is associated to the activation of photocatalytic reactions that is nocive for living beings on its surface. The effect of marine ambient on sample corroborates this conclusion, where after 6 months of exposure it was not sufficient for growing of biofouling on surface.

Resumo em Inglês:

High-strength low-alloy steel is used in pipelines, which transport oil/gas and also produced water in the process of the secondary recovery of oil. This paper investigates the corrosion of X80 steel after immersion in static systems (biotic and abiotic). The corrosion rate, the corrosion morphology and the hardness of the coupons were investigated. The corrosion products were determined by SEM/EDS and XRD. The corrosion rates of the coupons in the biotic system were moderate and had an agressive pit morphology, while those of the coupons in the abiotic system were low with less aggressive pit. The hardness of the coupons after exposure to the systems of produced water was not changed compared with that of the control coupons. The corrosion products formed in the biotic system were Fe(OH)3, Fe(OH)2, FeOOH, Fe3O4, FeS2, FeCl3, and in the abiotic system, NaCl, CaCl2 and SrSO4. BaSO4 and CaCO3 were identified in both systems.

Resumo em Inglês:

Superduplex stainless steels (SDSS) are frequently employed in the petrochemical industries where is required high mechanical strength, toughness, and corrosion resistance. However, these properties can be affected by deleterious phases formation due thermomechanical processes applied in the field during pipes and vessels construction. This work propose the nondestructive microstructural characterization of deleterious phases precipitated in SDSS isothermally treated in 800 and 850ºC using portable double loop electrochemical polarization reactivation tests (DL-EPR). The results obtained in this nondestructive test are quite close to those obtained by conventional test, and can be correlated with the amount of deleterious phases precipitated. It can be concluded that the microstructural degradation of superduplex stainless steel can be evaluated by portable DL-EPR test with slow sweep rates, using a special cell and a proper electrolyte at room temperature.

Resumo em Inglês:

BaCeO3-based ceramics are ionic and electronic conductors that can be applied to oxygen sensors, solid oxide fuel cells and oxygen permeable membranes. However, the low chemical stability at high temperatures of these materials motivates studies involving doping of A and/or B sites of the perovskite structure. In this context, the present work aimed to synthesize a new BaCe0.8Pr0.05Cu0.15O3-δ material using the chemical route of complexation which combines EDTA-Citrate with pH variation. The powders obtained at pH 3 or 11 and calcined up to 900 ºC are thermally unstable. The cubic perovskite BaCe0.8Pr0.05Cu0.15O3-δ with crystallite size between 99.4 nm and 131.6 nm was obtained along with barium carbonate traces. In the powders calcined at 1000 ºC the pH increase decreases the amount of barium carbonate (17.3% to pH 3, 3.4% to pH 7 and 1.8% to pH 11), but increases the size of grains with irregular shapes.

Resumo em Inglês:

To understand the processing influence in an intermeshing corotating twin-screw extrusion (ICTSE) on the morphology and impact properties of the uncompatibilized PBT/ABS (70/30) blend, it was submitted to different processing parameters. In this way both morphology and impact properties (resistance and ductile brittle transition temperature (DBTT) would be a function of processing only, because there would be no influence of a compatibilizer. The rotation speed of the screws influenced both impact resistance and Ductile Brittle Transition Temperature (DBTT) of the PBT/ABS blends. Blends prepared with higher rotation speed (240 rpm) did not present toughness at room temperature, whereas the blends prepared at lower speed showed high impact strength at room temperature and DBTT near to 5 °C. The angle between the kneading blocks discs also influenced the impact properties, because blends processed with screw with 90º angle between kneading block disks, for two different feed rates, showed lower DBTT than the blends processed with 45º angle. The morphological analysis by TEM showed that blends processed at low rotation speed of the screws presented a higher dispersion degree than those processed at high rotation speed. Blends processed in screws where the angle between the disks was 90º showed a higher dispersion degree than the blends processed in disks with a 45º angle. These results are in agreement with the impact properties, confirming that high dispersion of the ABS particles improves the impact properties of the blend.

Resumo em Inglês:

The commingled technology is a promising technique for the manufacture of composites reinforced with natural fibers. This study presents the development, processing and basic characterization of a long fiber Jute/Polypropylene (Jute/PP) commingled composite. The Jute/PP fabric was produced in a handloom and the composite was consolidated by compression molding. The PP matrix was chemically and thermally characterized to certify its chemical composition and define its melting and crystallization temperatures. The degradation behavior of jute fibers was also studied by Friedman’s kinetic isoconversional model using thermogravimetric analyses (TGA). The mechanical properties of jute reinforcement and Jute/PP composite were characterized by tensile strength tests and by fractographic study of the fracture surfaces. Its tensile strength (44.62±6.02 MPa) and elasticity modulus (7.10±2.34 GPa) are approximate to the ones obtained by other processing techniques, suggesting that the developed commingled process can work as a low cost and practical alternative methodology for manufacturing of more sustainable composites in industries.

Resumo em Inglês:

There is growing interest in replacing the synthetic reinforcements used for natural rubber (NR) composites with natural fibers from renewable, environmentally sustainable sources. Jute fibers may be suitable reinforcements for NR because they have a high tensile strength, which is comparable to other fillers such as glass fibers. Thus, we studied the incorporation of bleached jute fibers into NR, characterizing the mechanical, dynamic mechanical, and morphological properties of the composites. The addition of fibers to the NR latex was achieved by chemical coagulation, followed by vulcanization in a laboratory two-roll mixing mill. The elastic modulus at 100 and 300% elongation of the NR doubled after the addition of 10 phr of fibers without significant loss in the tensile strength or the elongation at break. The hardness was increased by 47%, and the storage modulus also increased, indicating the excellent interactions between the surfaces of the fibers and the NR matrix.

Resumo em Inglês:

In this work, discarded soda-lime glasses (from glass bottles) and recycled polystyrene (PS) spheres (d50 < 300 µm) were successfully converted into vitrocrystalline foams for thermal insulation applications. Physical and chemical properties of the selected and prepared raw materials (wastes) were characterized. Batches containing well mixed glass powder (d50 < 5 µm), PS spheres (10 - 80 vol.%) and PVA (8 vol.% ) were obtained and uniaxially pressed at 20 MPa. The obtained powder compacts were dried in air for 24 h and then fired at different temperatures (850 to 900 °C, 10 °C/min) for 30 min. Vitrocrystalline foams with interconned cells sizes between 86 and 815 µm, homogeneously distributed in a crack free matrix, were characterized from the point of view of their typical physical, chemical, morphological and mechanical properties. The results showed that it is possible to obtain vitrocrystalline foams with porosities up to 89% and compressive strength varying from 4 to 25 MPa.

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Films and edible coatings of natural polymers have been proposed as an attractive alternative for conventional plastic packaging because of their excellent biodegradability and biocompatibility. However, natural polymers, like chitosan, are hydrophilic and present poor water barrier properties. The addition of wax or other hydrophobic substances decreases water permeability of natural polymers but can increases their opacity.The objective of this work was to produce biofilms based on chitosan and different concentrations of carnauba wax and analyze their optical and barrier properties. The films were obtained by dissolving chitosan in acetic acid. Carnauba wax was incorporated into film-forming solutions at0, 15, 30, 40 and 50% (w/w). The opacity increased with higher concentrations of wax, the film with 50% of wax showed the highest value with an increase of 10.5% compared to the control film. The water vapor permeability decreased from 2.73 g.mm/kPa.m2.h (0% of wax) to 0.77 g.mm/h.kPa.m2 (40% of wax). The solubility decreased to about 60% over the control films, and the contact angle increased from 53º to 83º, in film with 0 and 50% of wax, respectively.

Resumo em Inglês:

Cerium molybdate semiconductive nanoparticles were synthesized by the EDTA-citrate combined complexation method. Gel thermal degradation behavior, phase formation, morphology, composition and band gap of cerium molybdate powders were characterized by TG/DSC, XRD, SEM/EDS and DRS analysis, respectively. The nanoparticles were synthesized by fixing the pH of the reaction medium to 9, producing an organometallic gel which was heated to 230 ºC obtaining a precursor powder. The precursors were calcined in a temperature range of 450 - 800 ºC for 3 h. The cerium molybdate powders were characterized and the phase evolution, morphology and band gap changes with the increase of calcining temperature were investigated. It was observed that the calcining temperature directly influences the formation of the crystalline structure, appearance of other phases in the materials and the particle size.

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The inhibition effect of castor bark powder obtained from Ricinus communis on AISI 1020 carbon steel in acidic media (HCl 0.5 mol.L-1) has been studied by electrochemical impedance spectroscopy (EIS), polarization curves, scanning vibrating electrode technique (SVET) and weight loss measurements. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed as characterization techniques. The EIS and gravimetric results showed that the inhibitory efficiency increases with inhibitor concentration achieving 83%. Polarization curves indicated that the castor bark powder acts as mixed inhibitor. The adsorption of the powder components on the metal surface follows the Langmuir isotherm. The FTIR analyses indicate the presence of C, N and O heteroatoms, incorporated in functional groups mainly related to the presence of carboxylic acids as ricinoleic acid, which could be responsible for the inhibitory properties of the powder. SEM analyses showed that the corrosion process was retarded in the presence of inhibitor in the electrolyte, which was confirmed by SVET measurements. Therefore, the results indicate that castor bark powder has potential to be a corrosion inhibitor for carbon steel in acidic media.

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The plastic instability in the stress-strain curve and work hardening of a type AISI 316 austenitic stainless steel was investigated in the high temperature range of 150°C to 800°C for two strain rates. The results indicate the occurrence of plastic instability and serrations between 200°C and 650°C with peaks in both the tensile strength and work hardening rate. These plastic instability/serrations are associated with dynamic strain aging behavior. As a consequence, within the temperature interval of plastic instability, a negative value for the strain rate sensitivity was found. Based on the activation energy, it is proposed that a mechanism of substitutional solute atoms interaction with dislocations be responsible for the plastic instability.

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As a byproduct of the combustion of rice husk to generate energy, rice husk ash (RHA) is formed by silica and carbon, apart from small amounts of other constituents. Several treatments can be used to increase the purity of the silica obtained, or even produce pure silica. The present study tested the efficiency of different techniques to obtain silica, characterizing and comparing the silicas obtained from RHA. A literature review was conducted, and then selected techniques were used to produce silica, which was characterized by XRF, XRD, particle sizing, specific weight, specific surface area, total carbon, and SEM. The literature review showed that most techniques include a pretreatment like acid or alkaline leaching followed by thermal treatment to increase the amount of silica produced by reduction of carbonaceous materials. The results showed that it is possible to produce silica from RHA using simple methods, and that these produced silica with purity above 98%. The treatments that afforded the best results were acid leaching followed by thermal treatment at 800ºC, and alkaline extraction at low temperature, with silica purity of 99.3% and 99.6%, respectively.

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Carbon fiber composites are used in several industries such as, aerospace, automotive, civil engineering, sports goods and technical applications due to its low-weight, strength and stiffness. However, the technology of recycling of these thermosetting polymer composites remains an engineering challenge because of their cross-linked structures that impede their reprocessing by simple heating. The aim of this work was to study the influence of the amount and dimensions of carbon fibers arising from composite waste into a new composite of polypropylene matrix. In order to carry out the study, the carbon fiber composite waste has been mechanically processed for the production of chopped fibers with two different lengths (4.5 mm and 3.0 mm). Thermoplastic composites made of chopped carbon fiber/ polypropylene at proportions 1%, 5% and 7% in fiber weight content were obtained by extrusion and injection process. Then, a series of laboratory test (mechanical, thermal and morphological) were performed in order to characterize the composite material obtained. The results showed that the fibers were capable of causing a reinforcing, even though the new composite presents a complex phase system with low adhesion between the recycled carbon fibers and the polypropylene matrix.

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Metastable β-type Ti alloys with non-toxic addition elements such as Mo, Zr, Sn, Ta and Nb were developed as an alternative to the widely used Ti-6Al-4V alloy for biomedical applications. These alloys possess enhanced biocompatibility and reduced elastic modulus in comparison with Ti-6Al-4V. Moreover, for orthopedic implants, low Young's modulus is required in order to avoid the stress shielding phenomenon. This study analyzes the microstructure and mechanical properties of a new Ti-12Mo-8Nb alloy after hot swaging, annealing at 950 ºC for 1h and water quenching. The alloy was characterized by X-ray diffraction, optical microscopy and transmission electron microscopy. Tensile tests were performed at room temperature. Young's modulus and hardness values were also measured. The structural characterization reveals a metastable β structure containing only a small amount of α and ω phases. Exhibiting a lower Young's modulus than Ti-6Al-4V and other previously studied Ti-Mo-Nb alloys, the Ti-12Mo-8Nb alloy can be a promising alternative for orthopedic application.

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The present work aims at the preliminary evaluation of the Paspalun repens macrophyte dry biomass adsorbent material of zinc (Zn) and copper (Cu) metals from water. The diversity of Species is due to the extensive aquatic environment where it is inserted. The Paspalun repens species comes from the Buiuçu lake located in the region of Parintins-Amazonas- Brazil. The macrophyte was dried in a mill and then a digestion through biomass microwaves was done before and after its exposure to the solutions containing different concentrations of zinc and copper (1.00, 1.50, 2.00, 3.00 mg mL-1 of metals) for a period of 48 hours. As a source of the metals, zinc sulfate (ZnSO4 7H2O) for zinc, and copper sulfate (CuSO4 5H2O) for copper were used as the source. As a result, the efficiency of Paspalun repens was observed in the metals removal, the highest removal percentage, of 29.67 and 37.07% in the leaves, whereas in the root it was 25.25 and 32.84% (at the concentration 1.0 and 2.0 mg/mL consequently), was of zinc, therefore the dry biomass of this species can be considered as a low cost alternative material in the removal of these heavy metals, contributing to the improvement of water quality.

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The thermal treatments employed in alloys are essential to obtaining desired microstructures and corrosion resistance properties. In this paper the low carbon martensitic steel 13Cr4Ni0.2C with different tempering temperatures was studied using potentiodynamic polarization technique in synthetic marine environment, in order to evaluate the effect of the tempering temperature on the steel corrosion resistance in an environment that simulates the conditions of use in oil and gas production. Microscopy results showed differences in the microstructure of tempered steel at low (620°C) and high (770°C) temperatures, indicating the appearance and extending of martensite laths with increasing temperature. Polarization tests showed that tempering temperature located between 620°C and 710°C indicated passive film formation and tempering temperatures of around 620 °C showed better resistance values to pitting corrosion.

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The Brazilian red ceramic industry monthly consumes about 10.3 million tons of clay, its main raw material. In most potteries, characterization of the clay is made empirically, which can result in roof tiles and blocks not according to standards. In this sense, this paper aims to characterize clays used in the manufacturing of red ceramic products in a factory located in Colatina-ES, which appears as a ceramic pole with about twenty small and midsize industries. The clays were characterized by: X-ray fluorescence, X-ray diffraction, thermal analysis (DSC/TG), granulometry, Atterberg limits and content of organic matter. Specimens of clay and mixture containing four clays were shaped. Specimens were shaped, dried at 110°C, and burned at 850ºC in an industrial furnace-type tunnel for 24 hours. The ceramics and mechanical properties evaluated were: mechanic strength, water absorption, apparent porosity, apparent specific mass and shrinkage by drying and firing. The characterization showed that kaolinitic clay presents high plasticity, but high porosity. The mixture formed by the four clays does not meet the requirements of the Brazilian standard clays for red ceramic. It is possible to confirm the use of the methodology of the spheres in potteries for analysis of ceramics raw materials.

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In this work, ceramic shell (mullite source), an industrial solid waste from the lost-wax casting process, after crushing and milling steps, was used and evaluated as an alternative raw material source for the production of cellular ceramics for high temperature applications (> 1400 °C). The obtained ceramic shell powder, with particle size distribution (d50 < 2 µm) suitable for the production of ceramic foams, was characterized from the point of view of their physical, chemical, morphological and crystallographic properties. Samples were prepared and obtained by direct foaming and gelcasting routes, dried at room temperature and then fired in two steps (650 °C/2 h and 1550 °C/2 h), and cooled in the furnace to room temperature. The effects of solids loading (35 and 42 vol. %) and stirring velocity (500 and 2000 rpm) on the cellular structure (pore size distribution and porosity) and mechanical properties of the produced ceramic shell foam samples were evaluated. The results showed that it is possible to obtain ceramic foams based on mullite-zirconite, with pore sizes between 100 and 900 µm, porosities up to 77% and compressive strength varying from 3 to 20 MPa.

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We investigate the band structure of elastic waves propagating in carbon nanostructure phononic crystals with square, rectangular, triangular, honeycomb and Kagomé lattices. We also study the influence of carbon nanostructure cross section geometry - circular, hollow circular, square and rotated square with a 45° angle of rotation with respect to the x and y axes. Plane wave expansion method is used to solve the governing equations of motion of a isotropic solid based on classical elasticity theory, ignoring nanoscopic size effects, considering two-dimensional periodicity and wave propagation in the xy plane. Complete band gaps between XY and Z modes are observed for all types of carbon nanostructures. The best performance is for nanophononic crystal with circular carbon nanostructures in a triangular lattice with high band gap width in a broad range of filling fraction. We suggest that carbon nanostructure phononic crystals are feasible for elastic vibration management in GHz.

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For the biomedical application of NiTi alloys, an excellent surface finishing process is required to guarantee high corrosion resistance and biocompatibility, eliminating the allergenic and toxic effects associated with the release of nickel ions in the body. Electropolishing is a process that can reduce surface imperfections and form a thin protective layer of TiO2, even in complex-shaped devices. The main objective of our study was to find and report suitable parameters for electrolytic polishing of NiTi wires, in both the superelastic and shape memory states. The results indicate that electropolishing in a 3.5 mol•L-1 methanolic H2SO4 electrolyte at 20ºC can effectively reduce surface roughness, remove superficial nickel-rich layers and improve corrosion resistance for austenitic and martensitic NiTi alloys.

Resumo em Inglês:

Fe60Cr8Nb8B24 (at%) amorphous powder and ingot were submitted to LASER cladding and remelting process, respectively. Fe-based coatings were produced using different LASER processing parameters and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Vickers microhardness. All coatings obtained by LASER cladding (LC) and layers obtained by LASER surface remelting (LSR) with shorter and median interaction times (scanning speeds of 16.7 and 66.7mm/s), irrespective of overlap value, presented peaks of the crystalline phases α-Fe, Fe2B and the FeNbB intermetallic. In addition, layers obtained by LSR with shorter interaction time (150mm/s), in general, presented only peaks of the α-Fe and Fe2B phases, except that produced with overlap value of 20%, more amorphous. SEM results showed that, regardless of LASER process, the coatings presented cracks, some pores and FeNbB intermetallic phase. All coatings obtained by LC and that obtained with shorter interaction time, by LSR, showed a Vickers microhardness, 1086 to 1329HV and 2161 to 2294HV, respectively, significantly higher than the substrates, AISI steel: 170HV and Fe-Cr-Nb-B: 1921HV.

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The final destination of PET packaging is creating economic and environmental concerns. One of the alternatives to minimize this problem would be making use of chemical recycling of this material through glycolysis with the aim to produce bis(hydroxiethyl) terephthalate, BHET monomer. This reaction is well known, but it still presents problems as BHET purity since it makes necessary the development of new catalysts highly selective. In this context, the present work studied the catalytic activity of a nanostructured material, titanate nanotubes (TNT), and compared it to a commercial catalyst (zinc acetate), which is the most used for this glycolysis reaction according to literature researches, and analyzed the influence of PET type (virgin and post-consumer) in the depolymerization for reaction times of 2, 3 and 4 hours. Using TNT as catalyst, BHET production yield and values of turnover number for the evaluated reaction times were higher than the results using Zn(OAc)2 for virgin PET, proving itself as a promising catalyst.

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Martensitic transformation can be induced by plastic deformation in metastable iron-based alloys, such as stainless steels containing limited amounts of C, Ni and Cr. This transformation takes place at the temperature range from Ms and Md, usually at relatively lower temperature values. The transformed martensite has been associated with maximum ultimate strength and relatively high ductility. In the present work, the tensile fracture characteristics of a metastable AISI type 302 stainless steel was properties were compared to those of a stable AISI type 310 austenitic stainless steel. It was found that in 302 steel, its high degree of metastability and dilute dispersion of inclusions result in higher strength and complex modes of fracture, one of which consisting of martensite surrounding globular inclusions.

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The aim of this work was to produce deposits of AA6351-T6, reinforced with alumina (Al2O3) particles, over a substrate of AA5052-H32 through friction surfacing. AA6351-T6 consumable rods were drilled with one and two holes, which were filled with Al2O3 particles posteriorly. To perform the deposition, a conventional KONE KFE-3/BR milling machine was used. The results showed that Al2O3 particles increase the hardness values of the produced deposits when compared to those without particle addition. The coatings presented a fine equiaxed grain size distribution, once the grain refinement was nearly 48% lower than the as-received material. Moreover, deposit regions that showed finer grain boundaries also showed a higher volume fraction, which can be related to the particle stimulated phenomenon. Electron backscatter diffraction results showed the occurrence of low angle grain boundary substructures and lattice rotation, indicating that the material undergoes dynamic recrystallization during friction surfacing.

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Austenitic stainless steels are high corrosion resistant alloys widely used in many industrial fields. Among this family of steels, AISI 317L stands out due to its higher localized corrosion resistance when compared to the traditional grades AISI 304L and AISI 316L. In some applications in oil refineries, the AISI 317L is being specified for services at moderately high temperatures. At the same time as it is sought to use new stainless steels, is also desirable to apply and develop emerging welding processes, replacing conventional ones, in order to achieve better behavior in service. In this respect, this work studied the effects of thermal aging on the toughness and resistance to pitting corrosion of AISI 317L steel weld metals produced by the Gas Tungsten Arc Welding (GTAW) and Friction Stir Welding (FSW) joining processes. After prolonged exposures at 450°C, for 200h, 300h and 400h, the microstructural characterization by scanning electron microscopy (SEM), toughness evaluation and anodic polarization tests in 3.5% NaCl solution were performed. The results showed that the increase of the exposure time in both weld metals caused a toughness decrease. The pitting potentials measured in the polarization tests also decreased with the aging at 450ºC.

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Geopolymers are exclusively mineral nature and are considered an alternative to materials based on Portland clinker, whose production accounts for about 5% of anthropogenic CO2 emissions in the world. The geopolymer cement concrete (GCC) may be prepared from natural oxide-aluminosilicates such as metakaolin (MK), or synthetic, such as fly ash (FA) together with active silica contained in the rice husk ash (RHA). The fracture properties of the Portland cement concrete (PCC) with 25 MPa and 50 MPa, and of three different geopolymeric concretes with the same strength Classes were determined for comparative analysis. The aim of this study is to provide support to begin the use of geopolymers in the reinforced concrete precasting Industry. Three-point bending tests of notched beams with a/d (notch depth/beam depth) of 0.5 from RILEM TC80-FMT Recommendations were used to determine the critical values of K, G, R and J-integral for crack propagation under mode I. The results showed that the geopolymeric concretes exhibit similar mechanical behavior and fracture properties higher that those determined in PCC for the same strength class.

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This work evaluated the water absorption of glazed porcelain stoneware ceramic tiles using three different methods. Two methods were based on a procedure of boiling in water, specified by standards ISO 10545 and ASTM C373, and the third was the vacuum method proposed by the standard ISO 10545. The three products produced under the three different firing conditions were tested according to a 22 factorial design, with intervening factors of the boiling time and immersion time for the methods involving boiling, and of pressure and immersion time for the vacuum method. The maximum saturation of the plates was evaluated by helium gas pycnometry testing. The results showed that no sample saturation occurs in the boiling water absorption test performed according to the conditions established by standards ISO 10545 and ASTM C373. The values of open porosity, using the method of helium gas picnometry, showed absolute values of saturation higher than those presented by the water absorption measured according to the current standards. Thus, the results showed that the current methods for determining the water absorption of glazed porcelain stoneware ceramic tiles do not guarantee the complete saturation of the plates and, therefore, they are not able to correctly measure this property.

Resumo em Inglês:

The new generation of cutting fluids should have some characteristics, such as low toxicity and biodegradability. A bio-cutting fluid emulsion are an excellent option because they present those properties, as well as good mechanical performance. The present study aims to investigate the lubricity of O/W emulsions (cutting fluid emulsion), varying the concentration of anionic surfactant (1%, 2.5% and 5%) and epoxidized oil (5%, 10%, 15%, 20% e 25%). A sunflower oil was chemically modified by epoxidation reaction, then its viscosity, iodine and oxirane index, density, and acidity were characterized. The performances of the emulsions were evaluated using a tribometer HFRR (High Frequency Reciprocating Rig), under hydrodynamic lubrication conditions. The ball wear scars were analyzed using an optical microscopy. The results showed that a low concentration of surfactant promote friction and wear reduction. Based on the tribological performance, the emulsions with 5% and 10% of epoxidized oil are more suitable.

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Choosing welding parameters is an important step in welding process, directly influencing in the heat input provided to welded joints. This heat input value, along with temperature distribution in welded joints, provides, to the drafter, conditions of predicting the Heat Affected Zone (HAZ) extension, the kind of microstructure to be formed, and therefore, the effects of residual stress. Three welding parameters were switched, providing different welding conditions. Each condition was analyzed by SmartWeld 2011 software and macrography to find and compare the extension of HAZ. As for the residual stresses, calculated through Displacement of Coordinated Points (DCP) method. It is possible to choose the best parameters for the welded joint by GMAW process considering the parameters in study.

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Billets of an Al 7075-T651 alloy were processed by two passes of equal channel angular pressing, ECAP, by following route A. First pass was performed at 180°C and the second one in the temperatures 130 and 180°C. The resulting microstructures were characterized by optical microscopy, OM, and scanning electron microscopy, SEM. Also, material macroscopic mechanical properties were evaluated by performing uniaxial compression and Vickers microhardness tests. After the second pass, it was not verified a noticeable grain refinement. After second pass at 130ºC, the samples presented higher mechanical strength than observed after their processing at 180°C and the second pass resulted in a decrease in the mechanical properties compared to the deformation by one pass at 180°C.

Resumo em Inglês:

Aluminum alloys of the ANSI series 319 present Si and Cu as the main alloying elements and the mechanical strength of these alloys can be improved by the precipitation of the metastable Al2Cu phase during the ageing heat treatment. In this paper, the Al-5.5wt.%Si-3wt.%Cu alloy was elaborated and solidified in a water-cooled horizontal directional solidification device. The as-cast ingot was subjected to the precipitation hardening heat treatment (T6 heat treatment), which consisted of: solution for 5 h at 490°C±2°C, followed by quenching in water at 60°C±2°C and ageing for 3 h at 155°C±2°C, and cooling-air. Secondary dendrite arm spacing (λ2) measurements were carried out before and after T6 heat treatment. The mechanical strength of the alloy was investigated by the microhardness test. It has been found that the heat treatment did not influence the λ2 values, however, highest HV values have been observed for the heat-treated samples.

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This work proposes the production of Cu-Sn alloy coatings with anticorrosive properties, using an environmentally non-aggressive bath. The coatings were electrodeposited on carbon steel substrate AISI 1020 using an electrolyte containing CuCl2 and SnCl2, and sodium tartrate as the complexant agent. The produced coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICPOES) and electrochemical impedance spectroscopy (EIS). The film showing the highest corrosion resistance was obtained using j = 100 Am-2. This coating was composed by 95.18 % m/m Cu and 4.83 % m/m Sn, and presented a uniform surface, without defects and small grain sizes. These characteristics probably contributed to the formation of Cu-Sn protective film onto steel substrate from a tartrate bath.

Resumo em Inglês:

Due to increasing improvement of weaponry and ammunition, attention is being given to the development of new materials that could more effectively resist to ballistic impact. In order to stop high energy bullets, with speed above 800 m/s, a high strength material is necessary. However, if just one material is used, then a relatively thick piece is required, which might affect negatively the wearer mobility. The objective of this work is to investigate the effect of thickness on the ballistic behavior of aramid fabric laminates, Kevlar®, hit by high energy bullet. The purpose is to find the minimum thickness to avoid perforation. Ballistic tests using conventional 7.62 mm ammunition were performed according to standard procedures. The macro and microscopic aspects of the target specimens were evaluated. The results showed a change in the ballistic behavior of the laminates as their thickness increased. It was found that until the laminate was able to capture the bullet, 96 layers (~50 mm) were required. This is significantly higher than the necessary thickness for a multilayered armor to stop the same 7.62 mm bullet.

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The control of the size and morphology of Metal-Organic Frameworks is a challenge that must be overcome to ensure the use of these materials in advanced applications. Mixed Lanthanide-Organic Frameworks (MLOFs) were synthesized via solvo(hydro)thermal method and then characterized by PXRD, IR, TG/DTA, SEM and PL spectroscopy. The effect of the modulator (acetic acid) on the morphological characteristics of the obtained powders was investigated. Trivalent terbium ions were successfully incorporated into La-framework conferring green luminescence to the prepared samples. It was observed that a gradual increase in acetic acid concentration led to the morphology change from micro-rods to flower-like small particle agglomerates. Moreover, a higher concentration of the acetic acid prevented the crystallization of secondary phases.

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In this paper, the effect of substitutional Mo amounts in internal friction and interstitial diffusion mechanisms was analyzed in Ti-15Zr-based alloys. Mechanical spectroscopy was obtained from room temperature up to 730 K with frequencies between 1 Hz and 40 Hz. Internal friction spectra were composed by anelastic relaxation peaks in β-type alloys (metastable and stable), due to stress-induced ordering of oxygen and nitrogen interstitially in octahedral sites of the bcc crystalline structure. Peak decomposition analysis exhibited interactions between matrix-interstitial (Ti-O and Ti-N), substitutional-interstitial (Zr-O, Mo-O and Mo-N), and clusters (Ti-O-O and Zr-O-O). The diffusion results showed that the introduction of Mo facilitates the diffusion of interstitial elements in the metallic matrix.

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This study involved an evaluation of the influence of phase inversion in poly(methyl methacrylate) elastomer/poly(ethylene terephthalate) binary blends (PMMAelast/PET) and the effect of the addition of poly(methyl methacrylate-glycidyl methacrylate-ethyl acrylate) (MGE) interfacial compatibilizer on the microrheological properties of this polymer blend. Thermal, dynamic mechanical thermal, rheological and morphological analyses were performed using sensitive techniques such as differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), parallel plates rheometry in the linear viscoelastic region, and atomic force microscopy (AFM), respectively. In this study, it was found that variations in the percentage of the PET phase influenced the correlation between the rheological properties at low shear rates and the morphology of the PMMAelast/PET binary blend and of the PMMAelast/PET/MGE compatibilized blend.

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The mineral diesel oil sold in Brazil, due to environmental reasons; presents sulfur concentration of 10 ppm, which causes a deficiency of lubricity, since sulfur is one of the chemical species that gives a good lubricating characteristic. Poor lubricity affects performance and causes failure of engine parts. This study aimed to evaluate the use of glycerin as an antiwear additive by means of tribological tests of the mineral diesel S10 B7 and 10 formulations of diesel based fuels, microemulsified with 0% (distilled water), 7.5% and 15% of glycerin solution. The formulations were subjected to lubricity tests on HFRR (Hight Frequency Reciprocating Rig) under hydrodynamic lubrication conditions, according to the ASTM D-6079 standard. The results showed that the increased concentration of glycerin added to diesel S10 B7 contributes to improved lubricity and wear reduction.

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The poly (vinyl chloride), PVC, undergoes changes in its physicochemical properties when it is exposed to gamma radiation. Thus, the radiolytic stabilization of PVC is one way for obtain a material with radiation resistance. In this work, we studied the coffee grounds oil as PVC radiolytic protection in two systems forms: PVC film and PVC specimen. The systems were irradiated at sterilization dose of medical devices and viscosity measurements were performed. According to viscosity assays of PVC films, there was a 67% protection in polymer matrix promoted by the oil. On the other hand, the mean viscosity molar mass (Mv) of PVC specimens increased about 13%, indicating predominance of crosslinking effect, however samples containing the oil showed no Mv significant changes. Therefore, the oil can be considered a PVC radio stabilizing substance and open a way for use of sustainable additive in PVC industry.

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Aluminum, copper and silver samples, all of them face-centered cubic (FCC) metals, were rolled at room and cryogenic temperatures until equivalent strains (ε) were between 3.23 and 4.13. The cryogenic temperature (CT) and room temperature (RT) rolled samples were evaluated by hardness tests and X-ray diffraction (XRD), which indicate influence of stacking fault energy (SFE) on process. Lower SFE metals tend to exhibit dislocation densities significantly increased and as consequence, hardness too. It was also noted that after sometime exposed to RT, the materials rolled at CT present hardness decrease.

Resumo em Inglês:

The lamination process adds the anisotropy characteristic in the final product. This anisotropy influences the yield strength according to the direction in question, the difference between the value of the yield tension in one direction and the value of the yield tension in another direction referred to as the back stress. Naval plates were welded by the GMAW process in the longitudinal direction to the lamination and in the transverse direction, and with different thermal loads. The residual stresses were calculated by displacement coordinate points method (DCP) and the back stress was found by tensile tests in specimen subjected made with either the longitudinal lamination direction and transverse lamination direction. The material used was ASTM A131 naval steel grade AH-36. The welded plates with greater thermal load in the longitudinal direction presented smaller residual stress in this direction, in relation to the transverse lamination direction. In the welded plates with greater thermal load, in the transverse lamination direction, the displacements in different directions were close, showing that the back stress does not act reversing the displacement (flow). Finally, for the welded plates with lower thermal load, both welded in the longitudinal and transverse direction, the displacements were small. In addition, the back stress did not act reversing such displacements.

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We investigate theoretically and experimentally the forced response of flexural waves propagating in a 1D phononic crystal (PC) Euler-Bernoulli beam, composed by steel and polyethylene, and its band structure. The finite element, spectral element, wave finite element, wave spectral element, conventional and improved plane wave expansion methods are applied. We demonstrate that the vibration attenuation of the unit cell can be improved choosing correctly the polyethylene and steel quantities and we suggest the best percentages of these materials, considering different unit cell lengths. An experiment with a 1D PC beam is proposed and the numerical results can localize the band gap position and width close to the experimental results. A small Bragg-type band gap with low attenuation is observed between 405 Hz - 720 Hz. The 1D PC beam with unit cells of steel and polyethylene presents potential application for vibration control.

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The influence of NaCl salt in the hydration of the Portland cement paste class G was studied using a Non Conventional Differential Thermal Analysis (NCDTA) on the first 24 hours of cement hydration. The mass of salt used corresponds to 0, 5, 10, 15 and 20% of mass of water used in the preparation of the pastes. The water/cement ratio (w/c) remained constant, being 0.46, and the pastes final volume was 99.9mL. Applying a deconvolution method to separate overlapped NCDTA peaks it was possible to estimate the energy released during the different stages of hydration and the effect of salt in cement hydration process. The presence of up to 10% of salt accelerated the hydration process and increased the hydration of C3S and C3A, while the 20% of the salt causes a delayed hydration and decreased the hydration of C3S and C3A. Futhermore, cement pastes with the same percentages of NaCl and with different hydration times were evaluated by Thermogravimetry (TG), Derivative Thermogravimetry (DTG) and Differential Thermal Analysis (DTA). After 28 days the presence of salt caused a greater increase in the formation of hydrated products.

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In this work, Ni-Co oxides coatings were produced using electrochemical techniques (chronopotentiometry and/or linear voltammetry) and solutions containing Ni2+ and Co2+ ions in the molar ratio 1: 2, sodium citrate as the ligand, and different pH values ​​(7.5 and 10.5). Energy dispersive spectrometry (EDS), scanning electron microscopy (SEM), Raman spectroscopy (LRS) and electrochemical impedance spectroscopy (EIS) were used to characterize these coatings. The results showed that both pH values favored the production of Ni-Co oxide phases, independent of the electrochemical technique used. The EDS analysis indicated that it was possible to produce of oxides coating presenting different Ni:Co ratios using electrodeposition process. However, the morphology, the microstructure and the electrocatalytic ability of the coatings depended on both the pH and on the electrochemical technique used to produce them. The coatings produced using pH 10.5 were suitable to be used as electrocatalysts for the oxygen evolution reaction (OER).

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Coatings technologies with biopolymeric films are effective in maintaining the chemical and sensory characteristics of several fruits. Cassava starch is an attractive biopolymeric because of its renewable characteristics and low cost, but it has a high transfer rate of water vapor. Hydrophilic compounds of organically modified montmorillonite clay by ion exchange can be used to improve the limiting properties of starch in exchange for additives such as lipids. The solutions prepared with 5% m/v starch / 5% m/m cationic / anionic clay and uncoated were applied in caja fruit, harvested at physiological maturity, selected for absence of defects and color uniformity. The experimental design was performed with four storage times (0, 3, 6 and 9 days). For the maturation index, there was an isolated effect of the type of coating and storage time, showing the composite films of modified cationic clay with greater MI of the fruits in comparison to the control fruits.

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The urban violence and the different types of global armed conflicts demand efficient protective systems against high energy ammunition. Multilayered Armor Systems (MAS) provide efficient protection by making use of lighter and more efficient materials. A typical MAS may be composed of three layers: a front ceramic followed by a composite, backed by a ductile metal. Polymer composites reinforced with natural fibers have proven to be effective second layers, being also lighter, low-cost and environmentally friendly as compared to conventional composites like KevlarTM. The present work evaluates MAS using as second layer polyester composites reinforced with 10, 20, and 30 vol. % of sisal fibers. Ballistic tests were performed using class III 7.62x51 mm ammunition, based on the NIJ 0101.06 backface signature methodology. Both the 30 vol.% sisal fiber composite and the conventional aramid laminates were equally efficient in terms of MAS second layer. The explanation might be the similar capacity of the different composites to retain the fragments generated by the interaction of the projectile with the front ceramic, independently of the percentage of sisal fibers.

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Heat treatment can modify the corrosion resistance of stainless steels. Thus, the corrosion behavior of ASTM A890/A 890M GR 5A super duplex stainless steels (SDSS) has been investigated in aqueous 60,000 ppm NaCl solution by several electrochemical tests. The specimens were aged for 2, 10, 50 and 100 hours at 475 ºC. Potentiodynamic polarization studies showed that, when the corrosion potential comes to the passivation state, a peak current is detected at about 400 mV vs. Ag/AgCl, with a strong influence on the film stability. The peak current value increased with the aging time; the highest peak value was for the sample aged for 100 h. Three potentials were chosen from the polarization curves in order to evaluate the sample/film/solution behavior and their changes over the passivation range. The results indicate that the passive film was degraded with the increase of the aging time. In addition, the results of the corrosion tests were compared with the evolution of the mechanical properties of the steels by the Vickers microhardness test.

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The purpose of this study was to investigate the kinetics of hydrogen absorption and hydride formation and their effect on the mechanical properties in Zr-1Nb and Zr-1Nb-1Sn-0.1Fe alloys, which were thermomechanically processed and gaseously hydrided at 320ºC under 10 bar hydrogen pressure. X-ray diffraction (XRD) confirmed the formation of α-Zr matrix after final heat treatment. The alloys absorbed almost the same amount of hydrogen, although with different kinetics. Absorption began almost immediately in Zr-1Nb alloy whilst in Zr-1Nb-1Sn-0.1Fe hydrogen absorption started after 11 h besides a faster hydrogen kinetics. Results showed that tensile strengths for both alloys were nearly independent of absorbed hydrogen. Fractographic examinations indicated ductile fractures for unhydrided condition whereas quasi-cleavage features were observed for all hydrided specimens.

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The processing of the thermoplastic composites can cause matrix thermo-oxidative degradation. Understanding the level of thermo-oxidative degradation, as well as the thresholds of temperature and processing time, allows the manufacture of high performance composites with higher crashworthiness. This study evaluated the matrix thermo-oxidative degradation by Friedman's isoconversional kinetic model to a carbon fiber/polyamide (CF/PA) commingled fabric. In addition, the CF/PA commingled composite was manufactured by consolidation under pressure at 240°C, 250°C, 260°C, 270°C and 280°C to observe the influence of the matrix thermo-oxidative degradation on its energy absorption capacity. Impact test and compression after impact (CAI) determined the energy absorbed by the CF/PA commingled composite at different processing temperatures. The results demonstrated that the matrix thermo-oxidative degradation affected the energy absorption capacity of the CF/PA composite when the processing temperature exceeded 260°C, which is in accordance with the prediction of the degradation study. Therefore, the optimal processing cycle occurs at 260°C for 20min. When it processed in temperatures above 260°C, the CF/PA commingled composite reduces in 0.14J/°C the energy absorption ability due to the matrix degradation in high temperatures, leading to a considerable reduction on crashworthiness and its performance.

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The conditions of chemical synthesis can be crucial for polymerization of styrene in such a way that it can be produced latex beads at nanometric range (ϕ < 400nm). In this work, it will be analyzed how the absence of N2 and surfactant will result in colloidal particles with high affinity to agglomerate forming two kinds of nanostructured assemblies: colloidal crystals and nanowires. Four syntheses were realized and four parameters were changed: temperature, impeller speed, and initiator and styrene concentrations. The dispersion was filtered and coated on glass slides by evaporation induced self-assembly (EISA) process. Morphology and topography were observed at Scanning Electron Microscopy (SEM) and Atomic Force Microscope (AFM) respectively. They show how the synthesis conditions play a vital a role on the formation of self assembly nanostructures that can be applied as templates for sensors and biomaterials devices.

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This paper sets out to evaluate the corrosion and biocorrosion of carbon steel ASTM A283 exposed to a Diesel S10 oil/tap water system under static conditions for 90 days. The following analyzes were performed: physico-chemical in tap water, sulfur content in Diesel S10 and quantification of sessile microorganisms in the biofilm formed on the metal. To monitor the corrosion process, mass loss, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), confocal laser microscopy and X-ray diffraction (XRD) were performed. There were changes in the composition of the medium, correlated with the formation of corrosion and biofilm products. There was biodegradation of the fuel, which in contact with water influenced the development of microorganisms. Moreover, the corrosion rate was classified as moderate, the main form of corrosion being seen to be local alveolar corrosion. Therefore, the results revealed that water in diesel oil can be an aggravating factor in the process of corrosion and biocorrosion.

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This work presents comparative analyses of the effect of specimens' shape and size on the compressive strength and modulus of elasticity of mortars. Mortar mixtures with compressive strength between 5 and 20 MPa were produced. Experimental tests determined the compressive strength of cylinder specimens of (5 x 10) cm and (10 x 20) cm, and also cubic specimens resulted of mortar's flexural strength tests, which use (4 x 4 x 16) cm prisms. The modulus of elasticity of the cylinder specimens was also determined. Cubic specimens' compressive strength was higher than (10 x 20) cm cylinder's compressive strength and lower than (5 x 10) cm cylinder's compressive strength. The dimensions of the cylinder specimens influenced its compressive strength, which was higher for the (5 x 10) cm specimens. However, it did not affect the static modulus of elasticity of the material. Correlations between the results were established and comparisons with different authors' results were made, improving both technological control and characterization of cement-lime mortars.

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Amongst the many parts of a silicon cells photovoltaic module, silicon is the most important and expensive constituent. Thus, research on silicon recycling from damaged cells can lead to economic and environmental benefits. In this work, the broken silicon cells were tailored to function along with the fluorine-doped tin oxide as the transparent electric conductors. The broken silicon cells were analyzed by the current density versus voltage plots, together with the Mott-Schottky, X-rays diffraction and fluorescence analysis. Under light, the damaged cells sandwiched between the two transparent electric conductors presented photovoltaic effect. However, such effect was not obtained after the removal of the antireflection layer due to the destruction of the n-type layer as demonstrated by the Mott-Schottky analysis. The X-rays diffraction revealed samples rich on silicon atoms and the presence of aluminum atoms as impurity.

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Titanium Grade 1 was deposited on Ti-6Al-4V, 2 mm thickness, by Friction Surfacing. The process parameters were rotational speed, deposition speed and consumption rate. Only the rotational speed was varied in order to evaluate the influence of this parameter on the coatings generated. The applicability of the process has been described for a large number of materials, although the depositions of titanium alloys are still not widely studied. The objective is to investigate the effects of the rotational speed on the coatings' geometry and microstructural evolution. This investigation has shown that Titanium Grade 1 coatings can be deposited onto a Ti-6Al-4V by Friction Surfacing depending on the rotational speed. The coatings' surface homogeneity was influenced by the rotational speed, being inhomogeneous for the lowest speed. The coatings' thickness and width increased with enhancing this speed. The heat affected zone in the substrate corresponded to the complete thickness under the depositions.

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MoS2 powder has been used to form "self-lubricating" composite coatings, which are very useful to increase the lifetime of machines where liquid lubricants cannot be used. In this work, amorphous overspray powder of Fe60Cr8Nb8B24 (at%) alloy was mixed with 5wt.% MoS2 powder and it was used to produce single tracks on AISI 1020 steel substrates by laser cladding. The tracks were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Vickers microhardness. It was observed α-Fe, an Nb-rich intermetallic and MoS2 particles in the tracks, regardless of laser parameter used. DSC analyses proved the presence of amorphous phase for samples produced with parameters 200W/33.3mm/s, 600W/100mm/s, 800W/100mm/s and 800W/150mm/s. The tracks produced with larger power (800W) and higher scanning speeds (100 and 150mm/s) exhibited a better integrity and homogeneity, lower dilution and presence of amorphous phase, being these parameters considered the most appropriate to produce composite coatings of Fe60Cr8Nb8B24 (at%)/5wt% MoS2 containing amorphous phase. Hardness tests showed that the single tracks produced are harder than the substrate, for example, the track produced with 800W/150mm/s exhibits hardness six times higher than the steel substrate, 1200 HV0.3 and 200 HV0.3, respectively.

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Cellulose is a polymer widely available in nature, however its applications may be restrict due to its hydrophilic character. The creation of hierarchical structures on the surface is one of the required factors to obtain the hydrophobicity of this material. In order to compare the morphological and chemical effects caused by the action of different gases in the creation of nanostructures on the cellulose surface, samples were exposed to oxygen (O2) and sulfur hexafluoride (SF6) plasma treatments. The changes in morphology after treatment prove that both the gases were able to create similar nanostructures in the material. The analysis of elemental composition and identification of functional groups on the sample surface showed that chemical modifications occurred differently for each treatment. Contact angle measurements revealed that samples treated by O2 plasma remained hydrophilic, whereas low receptivity to polar (θ > 120º) and non-polar (θ > 100º) liquids was observed for samples exposed to SF6 plasma.

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Zinc sulfide (ZnS) was synthesized by sonochemical method and nanoparticles with crystallite size around 2 nm were obtained. PVC containing ZnS nanoparticles at concentrations of 0.10; 0.30; 0.50; 0.7 and 1.00 wt% were gamma irradiated (60Co) at room temperature in air. No appreciable decrease in PVC Viscosity-Average Molar Mass (Mv) was observed for samples containing 0.7 wt% of ZnS nanocrystals. It was demonstrated that the addition of ZnS nanocrystals imparted molecular protection to the polymer matrix while improving flexibility, by decreasing the Young Modulus of PVC films. These results suggest the use of sonochemically synthesized ZnS nanocrystals as a new additive for radiation-grade PVC materials.

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Integrated circuits have several applications, including medicine and the aerospace industry, where reliability is essential. Packaging is an important step in the manufacturing of integrated circuits, and ball soldering is one of the most critical process, especially in assembling and interconnecting integrated circuits. The solder joint formed during the ball soldering process is intrinsically associated with the performance and the reliability of the electronic system. This study analyzed the influence of parameters or factors affecting the ball soldering process from the perspective of intermetallic compound formation and shear stress of the solder joint. The results indicate there is an interaction coupling between these two factors that cannot be seen when they are investigated individually, meaning that the individual effect of each factor differs from that of the combinations of factors. The results showed that the factor that most influenced shear stress and thickness of the intermetallic compound was peak temperature during ball soldering.

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Biomaterials are effective alternatives for tissue substitution, including the bone tissue, since they do not pose risks of transmission of diseases or immune rejection. Nowadays, there is an interest in new materials capable of being associated with other substances which favor bone formation, especially natural biopolymers, in particular chitosan, which may present a potential for repairing bone defects and forms films that adhere to metal surfaces. Titanium, despite being a material greatly employed in implants because of its excellent physical properties, does not present bioactive characteristics, making it necessary to use methods of surface modification to enhance its biological response, favoring bone formation. This work aims at studying commercially pure titanium (cp-Ti) coating with chitosan using the biomimetic method and the evaluation of the effects of process variables as substrate surface conditions. Subsequently, the incorporation of AgNO3 was studied and its effects on corrosion resistance were evaluated. To evaluate the coating process, several tests were conducted, such as scanning electron microscopy, X-ray diffraction and infrared spectroscopy. From the results obtained, the efficacy of the chitosan film in inhibiting the corrosion of the metals is concluded, which was the target of this study, thus justifying its use for osseointegration and in several implants.

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The present study aimed to investigate the degradation of poly(ethylene oxide) (PEO) in the presence of cationic dye crystal violet irradiated under visible light. The preparation of the samples was done in the form of films obtained by casting. Degradation tests were carried out by 120 hours at room temperature. The degradation kinetics of the dye and polymer were accompanied by UV-Vis spectrophotometry and viscosimetry technique. The UV-Vis Spectra showed 81.2% degradation of the dye. In addition, it was observed a broadening of the absorption band of the polymer and the reduction of its viscosity, which features degradation. In this way, it is possible to affirm that the crystal violet dye, at the studied concentration, contributed to the degradation process of PEO.

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Aiming to reduce aircraft weight, aeronautic industry seeks alternative materials and processes used to join its different structural parts. An option to traditional methods are high performance adhesive joints, which reduce weight, number of parts and component final cost, also resulting in higher strength structures. Although, the lack of experimental data to provide a detailed structural characterization of these joining techniques had limited their commercial application. The proposal of this work is to investigate the Mode I interlaminar fracture toughness under quasi-static loading using DCB specimens of carbon composite joints made by co-bonding and secondary bonding techniques, the latter giving more reliable results. For a better understanding on the failure in the systems, DSC and microscopy techniques were applied, from which three stages of delamination process during testing were observed: 1st Stage) Cohesive failure represented by an unstable crack propagation from a high energy level; 2nd Stage) transition from cohesive to adhesive and final intralaminar failure mode with lower energy levels than Stage 1; and 3rd Stage) completely stable propagation at low energy levels (delamination migrates from intralaminar to interlaminar, entirely in the substrate).

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The additive manufacturing processes emerged at the end of the last century and became popular by low-cost 3D printers. The most used printers work on a cartesian configuration, but recently were launched delta machines. These 3D printers use a more complex control system due to their trajectories generation but may present some advantages over the cartesian configuration. To increase the knowledge about additive manufacturing, a comparative study with cartesian and delta printers was performed to evaluate the performance on printing a testing part. Three samples were produced in each printer and compared based on surface quality, manufacturing time, mass and dimensional measurement. The printed objects were 3D scanned for comparing the digitized geometry by aligning the point cloud generated to its virtual 3D model. The parts produced in delta printer obtained better surface quality, while cartesian printer provided better dimensional accuracy. The results also showed that the variation of the mass and time to produce the parts were not significant.

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Inorganic nanoparticles incorporation in polymer membranes for filtration processes has attracted the attention of researchers in order to improve in some ways their performance. In this work, AgNPs were synthesized "in situ" in cellulose acetate (CA) membrane by chemical reduction of a silver salt. The membranes were prepared by the nonsolvent induced phase inversion method. Asymmetric membranes without (CA-M) and with adsorbed AgNPs (CA-Ag-M) were obtained. Ultrafiltration properties were confirmed for both membranes (16 nm of average pore diameter) and average crystallite size of 21 nm for the adsorbed AgNPs was computed. Contact angle measured with Milli-Q water and dry CA-Ag-M is near zero while for the CA-M is around 80°. The CA-M showed water permeability of 214 Lh-1m-2, while the CA-Ag-M permeability was 1651 Lh-1m-2.

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Two distinct AISI type 316 stainless steels, of Brazilian and Swedish origins, were compared regarding their creep fracture mechanisms at 600, 700 and 800°C. The possible mechanisms associated with the creep fracture strength were identified by means of fracture maps proposed either by Ashby and collaborators or by Miller and Langdon. Experimental creep results were consistent with the general Ashby and collaborators map for face centered cubic alloys. By contrast, the two different 316 steel displayed significant differences in the model-based map of Miller and Langdon. In the present work, changes in the maps frontier are proposed as well as the introduction of a new field in the map related to grain boundary precipitation. These propositions allowed the Miller and Langdon map to be coherent with the experimental creep fracture results of both 316 stainless steels.

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Due to its ester bonds, poly(lactic acid) (PLA) undergoes biodegradation in humid environments, attracting market attention. The goal of this work was to observe the biodegradation in garden soil of PLA nanocomposites with neat (PLA/CNW) and surfactant modified cellulose nanowhiskers (PLA/CNW/S). Three types of surfactants were tested: poly(ethylene glycol) monooleate (PEGMONO) and poly(ethylene glycol) with molecular weight of 300 and 1000 Da. The films were obtained by solution casting, cut in strips of (2x2) cm and buried in garden soil, monitoring the temperature and humidity. After 90, 120 and 150 days changes were observed in the films by visual inspection, polarized light microscopy, thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The results showed that the addition of surfactant favored the biodegradation of nanocomposites and that PLA/CNW/PEG1000 showed the fastest biodegradation rate.

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High performance solar collectors are those with high selectivity surfaces, high solar radiation absorption and that do not thermally reemit to the external environment. Strategies to enhance this performance might involve surface porosity modification. In this work, a plasma treatment technique called plasma electrolytic oxidation (PEO) has been tested to produce porosity on aluminium surfaces in a controlled manner. The porosity control was made by varying the intensity, frequency and duty cycle of the applied voltage pulses. The aluminium sample was placed in a solution of 1 g/L Na2SiO3. Voltage of 500 V and current density of 0.17 A cm2 was applied between electrodes. Three duty cycles were used: 33.33%, 50.00% and 67.77%. After treatment, the size, number and distribution of pores were evaluated. These parameters were correlated with both surface reflectance and optical absorbance. It was possible to control the porosity by controlling the electrical parameters of the process. While the mean pore size was directly related to the duty cycle, the inverse occurred for the number of pores. Surface treated with duty cycle of 33.33% presented higher values of absorption for all wavelength range.

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Rotary jet spinning (RJS) and electrospinning are techniques to obtain fibrous scaffolds. RJS is a simple method, which fabricates three-dimensional fibers by exploiting a high-speed rotating nozzle, creating a polymer jet which stretches until solidification, and does not require high voltage. In opposite, electrospinning technique needs the presence of an external electric field to create fiber from the polymeric jet solution. This article investigates both processes using two different biocompatible polymers: Poly(L-lactic acid) (PLLA) and Poly(ε-caprolactone) (PCL). Samples were characterized by scanning electron microscopy, thermogravimetric analysis, differential scanning calorimeter, and Fourier-transform infrared spectroscopy. Morphological observations showed the efficiency of both techniques in obtaining nanofibers. Thermal analyses of data indicate immiscible property of different blends and the total solvent evaporation. In vitro cytocompatibility test showed that RJS and electrospinning samples exhibited good cytocompatibility. Based on these results, it may be concluded that the fibers obtained with both technologies are non-cytotoxicity and with good biocompatibility, and might be suitable for applications as scaffold for cell growth.