Scielo RSS <![CDATA[Materials Research]]> http://www.scielo.br/rss.php?pid=1516-143920190002&lang= vol. 22 num. 2 lang. <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[Influence of the Fraction of Comonomers and Diluents on the Preparation of Polymeric Microspheres Based on Poly (Methacrylic acid-<em>co</em>-divinylbenzene) Obtained by Precipitation Polymerization]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200201&lng=&nrm=iso&tlng= Abstract Preparation and characterization of polymeric microspheres based on poly(methacrylic acid-co-divinylbenzene) (P(MAA-co-DVB)) by precipitation polymerization are reported. The influence of the change in comonomer composition, crosslinking degree, ratio of total monomers/diluents by weight/volume (g/100 mL) and the volume ratio of diluents were studied. Spherical particles were obtained in the range from 1.42 to 8.41 µm. An increase in particle size and thermal resistance with decreasing molar fraction of methacrylic acid (MAA) were observed, associated with increases in critical chain length (CCL) and the number of crosslinks in this system, respectively. The analysis of particles with molar fraction of 50% MAA and acetonitrile/toluene volumetric ratio of 75/25 showed that larger particle size and yield were achieved with increasing ratio of total monomers/diluents (g / 100 mL). The particles prepared with 14% molar fraction of MAA obtained greater swelling ratios than the particles prepared with 50% MAA. <![CDATA[Microarchitecture and Radiological Flow Pattern of Cocoon-like Nanocellulose Hydrogels]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200202&lng=&nrm=iso&tlng= Abstract This work investigates fluid mechanics and structural properties inside bacterial cellulose hydrogels in from of macroscopic anisotropic ellipsoid body cocoon-like 3D scaffolds. The hydrogels were evaluated by injections of iopamidol, a radiopaque medium used in medical radiological procedures. Results showed that hydromechanical behavior of BC hydrogels may be used to characterize its internal structure. It is suggested that internal barriers and flow distribution anisotropy may be used to develop novel therapeutic applications based on the tissue engineered multifunctional possibilities of the biomaterial. <![CDATA[Thermomechanical Properties of Corn Starch Based Film Reinforced with Coffee Ground Waste as Renewable Resource]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200203&lng=&nrm=iso&tlng= Abstract Starches polymeric films offer several advantages for the replacement of synthetic polymers due to their biodegradability, non-toxicity, availability and low cost. However, the high biodegradation potential can cause fragility, considering some fundamental mechanical properties. Therefore, starch based polymeric films were reinforced incorporating lignocellulosic waste from coffee grounds post-consume. The effect of incorporation of coffee ground in cornstarch matrix and polymer interaction on morphology, thermal and mechanical properties were investigated. The characterization analyzes were based on Dynamic Mechanical Thermal Analysis (DMTA), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Scanning Eletronic Microscopy (SEM). The coffee ground behaved as reinforcement agent according tensile values. Thermochemical conversion showed that polymeric films molding did not change his thermal stability. In temperature range was possible to observe the devolatilization, organic and inorganic compounds decomposition. SEM images showed the coffee ground adhesion in the polymer matrix promoting a better mechanical tensile strength. <![CDATA[Investigating the Effect of Delamination Size, Stacking Sequences and Boundary Conditions on The Vibration Properties of Carbon Fiber Reinforced Polymer Composite]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200204&lng=&nrm=iso&tlng= Abstract Composite structures are extensively used in various fields ranging from, but not limited to marine, aerospace, automotive, agricultural and industrial equipment due to their unique and excellent properties like weight associated with density. On an increase in their applications, it also requires special attention to manufacture and process the composites to acquire the high level of stability. Most critical defect in composite structures that have attracted many researchers is delamination. Delamination in composite structures are inevitable during service period. Present work is focused on investigating the effect of presence of delamination in the carbon fiber reinforced composite plate using finite element solver software, ANSYS. Present analysis will focus to find the effect of delamination size, boundary constraints and layups on the natural frequency of carbon fiber composite plate. Analytical results were also analyzed using MATLAB environment. Governing equations were derived using Rayleigh-Ritz method. The natural frequency reduced on an increase in delamination size and it is high in clamped-clamped boundary conditions rather than simply supported constraints. The finite element results are then compared with analytical results for clamped-clamped boundary conditions and found in close agreement. <![CDATA[Preparation and Characterization of Clay-polymer Nanocomposite Having Covalently-bound poly(norbornenes) with Pendant Cholesterols]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200205&lng=&nrm=iso&tlng= We have successfully prepared a clay-based polymer nanocomposite having grown cholesterol bearing poly(norbornene) brushes end-tethered from a naturally-occurring montmorillonite clay template. The synthesis of this hybrid material involved the treatment of the clay with first generation Grubbs catalyst, a ruthenium alkylidene, which induced a ring-opening metathesis and subsequent surface initiated polymerization of the cholesterol bearing monomer. This results in an inorganic/organic hybrid functional nanomaterial where the inclusion of the clay particles in a liquid crystalline domain modifies the thermal transitions. <![CDATA[Structural and Optical Properties of GaN Thin Films Grown on Si (111) by Pulsed Laser Deposition]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200206&lng=&nrm=iso&tlng= In this work we present results and analysis concerning the processing and characterization of Gallium Nitride (GaN) thin films (TF) grown on Si (111) substrates by pulsed laser deposition technique (PLD), which were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) and Raman spectroscopy (RS). The GaN films showed the hexagonal phase with a preferential orientation in the (100) direction, SEM pictures showed a cauliflower-like morphology. Room temperature PL studies showed the so called GaN-yellow band, at 2.29 eV, as well as the donor-acceptor (DA) pair luminescent transition around 3.0 eV. At 10 K, phonon replicas, separated by 69 meV, were observed. By RS, the optical mode on 710 cm-1 was observed, corresponding to the longitudinal optical phonon, A1(LO), as reported for this material. <![CDATA[On the Global and Localised Corrosion Behaviour of the AA2524-T3 Aluminium Alloy Used as Aircraft Fuselage Skin]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200207&lng=&nrm=iso&tlng= The aim of this work was to study the corrosion process of new aluminium alloy AA2524-T3 (Solution Heat Treated and Cold Worked), which is a promising substitute of the base line AA2024-T3 for aircrafts fabrication, by global and localised techniques in sodium chloride medium (0.05 mol L-1 NaCl). The open circuit potential results revealed a stochastic evolution of pitting events and to the resulting variations in the ratio of passive/active areas and/or cathode/anode, which may be related to the presence of different types of intermetallics. The cyclicvoltammetry showed that the corrosion potential (Ecorr) and the pit nucleation potential (E pit) values are quite similar (approximately -0.525 V). The results of EIS show that the corrosion rate is quite stable, with no tendency to increase or decrease for longer immersion periods. The results of SVET were in agreement with the results obtained by EIS technique, showing strong anodic activity on the surface with no repassivation along the whole immersion time. Besides, corrosion process led to significant surface degradation after 24h. <![CDATA[Mechanical Properties and Abrasive Wear of Different Weight Percentage of TiC Filled Basalt Fabric Reinforced Epoxy Composites]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200208&lng=&nrm=iso&tlng= Fiber reinforced polymers are very rarely applied as wear-resistant materials because of the lack of good mechanical strength, which adversely affects the properties of the composites. To improve the mechanical and abrasive wear resistant of the composites, fillers are incorporated into the polymers. Hence in this work composites are produced by adding functional inorganic fillers such as Titanium Carbide (TiC) and basalt fabric as reinforcement. The composites have been fabricated by using vacuum assisted resin transfer moulding (VARTM). Abrasive tests were conducted using pin-on-disc instrument by varying abrasive distances at different loads of 5, 10 and 15N.After the incorporation of TiC filler in basalt fabric reinforced epoxy composite a significant reduction in weight loss were observed. Composites containing 2wt% TiC exhibit the lowest weight loss among other 4 wt % and 6 wt % TiC filled epoxy composites. The surface topography the composites were analyzed by using scanning electron micrographs (SEM). <![CDATA[Doped Silicon Nanowires for Lithium Ion Battery Anodes]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200209&lng=&nrm=iso&tlng= Nanostructured silicon (Si) has showed outstanding results as Li-ion battery anode material. Fabrication of nanostructured silicon anode materials is usually very complex, time consuming and expensive. In this work, silicon nanowires (SiNW`s) were produced by using rapid and uncostly metal catalyzed electroless etching (MCEE) method from various silicon wafers with different dopant atoms and concentrations. We have investigated the effect of doping level on capacities and cycle stability. Highly doped silicon nanowires produced better results than lightly doped silicon nanowires due to their highly conductive and highly porous nature. Arsenic doped silicon nanowire anode electrodes have reached a capacity of 3635 mAh/g for the first lithiation and maximum 25% charge capacity loss after the 15th cycle. Owing to their small size and porosity this highly doped silicon nanowires showed very high performance and cycle retention as a lithium ion battery anode material. <![CDATA[Integrated Experimental Approach for Alloying of Surface Layer Ti6Al4V+B<sub>4</sub>C Metal Matrix Composites using Laser Treatment]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200210&lng=&nrm=iso&tlng= Surface engineering applications have brought the titanium and its alloys into the limelight in the manufacturing industries such as the aerospace, automobile, marine, chemical processing industry, nuclear power and biomedical. Despite the growths experienced in the use of this material, it is plagued with poor wear behaviour, especially when in contact with other materials during application. In this research work, the reinforcement of titanium alloy (Ti6Al4V) and boron carbide (B4C) ceramic powders was employed to form the Ti6Al4V+B4C composites. The effect of laser power on the micrograph, microhardness, surface roughness and wear has been investigated. The micrographic evaluation, the geometrical analyses and the effect of laser power on the width and height of deposit, aspect ratio and dilution rate were also evaluated. The highest aspect ratio of 5.31 and dilution rate of 63.81 % was observed in sample MB5 deposited with a laser power of 2400 W. The dry sliding friction and wear conducted using a 10 mm diameter tungsten carbide ball and a normal load of 25 N revealed that sample MB2 produced at a laser power of 1800 W has the lowest wear depth and wear width of 74.6 µm and 1080.77 µm. From the lowest COF attributed by sample MB5, it can be inferred that coefficient of friction does not determine the wear loss due to the sticking of some wear debris to the wear track during sliding action. Thus, other wearing factors are also considered for the wear loss evaluation. However, this composite can be used for the repair of the worm part of a rotating shaft and turbine blades. <![CDATA[Development of Poly (butylene adipate-co-terephthalate) Filled with Montmorillonite-Polypyrrole for Pressure Sensor Applications]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200211&lng=&nrm=iso&tlng= A novel pressure sensing material composed of poly (butylene adipate-co-terephthalate) (PBAT) and montmorillonite-polypyrrole (Mt-PPy) was prepared using melt mixing and injection molding. The structure and properties of the PBAT/Mt-PPy composites were evaluated and compared with those of the PBAT/PPy blends. The PBAT/Mt-PPy displays a very sharp insulator-conductor transition and its percolation threshold was reached at 6.5 wt% of Mt-PPy, which was lower than that for PBAT/PPy (11.0 wt% of PPy). The transmission electron microscopy analysis shows that Mt-PPy displays a high aspect ratio and was better distributed and dispersed into PBAT compared to PPy. PBAT/Mt-PPy exhibits a decrease in the electrical resistivity with an applied compressive stress due to the formation of new conducting pathways. The electromechanical response was dependent on Mt-PPy and the maximum sensitivity was observed for the composite containing 10 wt% of Mt-PPy. In this system, the electrical resistivity drops from 9 x 106 to 2 x 106 Ω cm when a compressive stress of 0.25 MPa was applied. The electrical resistivity changes with applied compressive stress, the reproducibility and the reversibility makes PBAT/Mt-PPy a suitable material for the development of pressure sensors. <![CDATA[Simulation of an Injection Process Using a CAE Tool: Assessment of Operational Conditions and Mold Design on the Process Efficiency]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200212&lng=&nrm=iso&tlng= The present work developed an experimental and simulation study to evaluate the influence of some operational conditions and mold design on the efficiency of an injection process used to produce polystyrene parts. The software SolidWorks Plastic was used to simulate the injection process and assess the performance of the mold considering the absence and the presence of venting. Experimental results obtained by varying the injection pressure, injection temperature as well as the mold temperature were used to validate the simulation data generated considering both mold designs. The findings revealed air entrapment at the end of the mold cavity and low process efficiency when the mold was operated with no venting, regardless the processing conditions. Simulation results indicated a remarkable increase of the process efficiency when vents were included on the parting line of the mold. In addition, the range of processing conditions which led to the highest process efficiency was virtually identified and tested in the real modified mold (with venting system). The findings revealed that the injection cycle time reduced in approximately 35% and the waste generation diminished from 65% to less than 1% when venting was included in the mold design and the optimal operational conditions were used. <![CDATA[Consolidation of Fe-Based Metallic Glass Powders by Hot Pressing]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200213&lng=&nrm=iso&tlng= An alternative route to obtain bulk metallic glasses is by consolidation of metallic glass powders by deforming these materials in the temperature interval between the crystallization temperature and the glass transition temperature, where the material flows with a reduced viscosity. In the present work, bulk parts of the Fe43.2Co28.8B19.2Si4.8Nb4 alloy were produced by hot-pressing gas-atomized powders (GAP) under different uniaxial pressures. Different microstructural analysis revealed that the initial powder as well as the consolidated parts were mostly amorphous, with similar transformation temperatures, showing that bulk samples of this alloy can be produced by conformation in the supercooled liquid region. The sample conformed under the highest pressure (1GPa) exhibited the highest relative density of 96.1±0.5%. These results show that hot pressing of Fe-based gas-atomized powders is a promising route for producing Fe-based bulk metallic glasses. <![CDATA[Investigation on Structural, Morphological and Relaxometric Properties of Lamellar Zrp Modified with Long Chain Amine]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200214&lng=&nrm=iso&tlng= In order to search nanofiller for controlling release of drugs lamellar α-zirconium phosphate (α-ZrP) was modified with ether-amine oligomer (E-A). Synthesis and chemical modification followed specific reaction conditions and different EA:ZrP ratios. Infrared spectra showed strong interaction between P-OH and NH2 groups. Thermogravimetric curves showed that ether-amine oligomer was incorporated by ZrP. Interlamellar space of α-ZrP increased at least four times indicating intercalation. The relaxometry analysis indicated that α-ZrP molecular mobility changed according to the ether-amine amount. The scanning electron microscopy/energy dispersive analysis revealed the presence of octadecylamine inside the α-ZrP galleries. The results showed that P-OH group (Brønsted acid) and amine group (Brønsted base) reacted to each other, resulting in an ionic bond PO- + 3HN-[-(CH2-CH2-O)m-(CH2-C-H(CH3)-O)n-]. Partially intercalated nanofiller were achieved. <![CDATA[Investigation of Austenitic Stainless Steel Coatings on Mild Steel Produced by Friction Surfacing Using a Conventional CNC Machining Center]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200215&lng=&nrm=iso&tlng= The friction surfacing process allows deposition of similar and dissimilar coatings in the solid state, avoiding some of the problems associated with conventional coating methods in which fusion is involved. In the present work, a viability assessment of producing AISI 304 austenitic stainless steel coatings on AISI 1020 low-carbon steel substrates using a machining center with Computerized Numerical Control (CNC) instead of dedicated friction surfacing equipment was pursued. The influence of consumable rod rotation and translation speed, as well as substrate surface roughness on the geometry and adhesion of the coatings was evaluated. The microstructure of the stainless steel coatings was investigated by optical and scanning electron microscopy, while microhardness analysis was performed in order to evaluate properties near the coating-substrate interface. Finally, the electrochemical corrosion behavior of the coatings and the as-received AISI 304 steel consumables in 0.5M H2SO4 solution containing naturally dissolved O2 was compared. The results revealed that the friction surfacing process can be applied in non-specialized machinery, since the manufactured coatings exhibited good adhesion and corrosion resistance. The formation of hard bands in the coatings was identified near the interface region and the adhesion of the coatings was found to be influenced by initial substrate roughness. <![CDATA[Wear behavior of Diamond-like Carbon Deposited on Ti6Al4V Prepared with Surface Mechanical Attrition Treatment]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200216&lng=&nrm=iso&tlng= Surface modification by deposition of hard coatings is a way to overpass the poor wear resistance of some metallic materials and one potential material is the Diamond-Like Carbon (DLC). We investigated the wear behavior, and the adhesion of the DLC deposited on a Ti6Al4V (Ti64) alloy after Surface Mechanical Attrition Treatment (SMAT). The SMAT was applied using 100Cr6 steel balls, and the DLC was deposited through the sputtering method. The nano-hardness was evaluated using a MTS Nano Indenter XP. The adhesion of the DLC was evaluated using a CSM Revetest, and the wear tests was performed in a reciprocating linear tribometer from CSM Instruments. The mean wear rate for the Ti64 was 437x10-6 mm3/N/m against 5x10-6 mm3/N/m for the Ti64+SMAT+DLC. The SMAT reduced the wear rate of the DLC coating, showing that the SMAT might be a viable treatment with promising results regarding the DLC wear resistance. <![CDATA[Synthetic Aluminosilicates for Geopolymer Production]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200217&lng=&nrm=iso&tlng= Abstract The use of geopolymer has been studied as a potential substitute for Portland cement due to lower CO2 emission and improvements on structural properties. Some of the major raw materials used in the manufacture of the geopolymer are: steel slag, fly ash and metakaolinite. Due to the impurities contained in these raw materials, the present study uses high purity synthetic aluminosilicates made from the sol gel process for production of geopolymers. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR). The results showed that the synthetic aluminosilicates have similar behavior to metakaolinite (reference). It was found that the coordination of Al in the synthetic aluminosilicate changed from VI to IV and V from 300 °C, with the highest intensity at 900 °C. Temperature at which the highest mechanical strength of the geopolymer was also observed. <![CDATA[Nb-doped Ti<sub>2</sub>O<sub>3</sub> Films Deposited Through Grid-Assisted Magnetron Sputtering on Glass Substrate: Electrical and Optical Analysis]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200218&lng=&nrm=iso&tlng= Abstract Niobium doped dititanium trioxide (Ti2O3:Nb) films were deposited on glass substrates, through grid-assisted magnetron sputtering. The Ti2O3:Nb films were characterized by X-ray diffraction (XRD), electrical conductivity and optical properties. Film deposition was carried out in two different substrate bias modes: DC and unipolar pulsed. Results show that the negative-pulsed mode improves conductivity and crystallinity. The XRD results show peaks corresponding crystallographic planes of Ti2O3. No niobium oxide NbxOy peaks were observed, which indicates that niobium oxide if formed, is amorphous, and/or substituted Nb atoms remain in a solid solution within the Ti2O3 structure. It was observed that "as-deposited" Ti2O3:Nb films (without post annealing) are transparent and electrical conductive, with transmittance that reaches 60% in the visible light wavelength despite the considerable thickness of the film and a miminum resistivity of 2x10-2 Ω.cm which indicates that there is potential for application as Transparent Conductive Oxide (TCO). <![CDATA[Process Evaluation of Sugar-Based Polymeric Colloidal Nanocarrier Formation]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200219&lng=&nrm=iso&tlng= Abstract Several studies have demonstrated that sugar-based nanocarriers are recommended to develop drug delivery systems since they are biocompatible and biodegradable and might improve the therapeutic index of currently used drugs by reducing their toxicity and enhancing their bioavailability. Therewith, this work studied the processing conditions to formation of a sugar-based nanocarrier denominated polymeric colloidal nanocarriers (PCN). It reports the impact of emulsifiers types and concentration, salt concentration and copolymers addition on physical stability and particle size distribution of a maltodextin-based PCN. In order to define the most stable formulation to produce the maltodextrin nanocarriers, 13 PCN formulations were evaluated in respect to kinetic stability, particle size distribution and morphology. The results demonstrated that to have a stable sugar-based PCN in silicone for at least 3 days, it is necessary to work with Poloxamer 188 as a copolymer, SF 1540 surfactant in a concentration proportional to the solid content and a salt concentration of 0.4 %. <![CDATA[Investigation of Stress Corrosion Cracking of Austenitic, Duplex and Super Duplex Stainless Steels under Drop Evaporation Test using Synthetic Seawater]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200220&lng=&nrm=iso&tlng= Abstract Stress corrosion cracking (SCC) of UNS S31603 austenitic stainless steel (ASS), UNS S32205 duplex stainless steel (DSS) and UNS S32750 super duplex stainless steel (SDSS) was investigated. SCC tests were carried out at 110 ºC for 500 h under drops of synthetic seawater (DET, drop evaporation test). Two loading conditions were investigated: 50 % and 100 % of the experimental yield strength of each steel. DSS and SDSS specimens showed no susceptibility to SCC under loading of 50 % of their yield strength, contrary to ASS, but all steels fractured at the highest load. SCC nucleated under the salt deposit formed on the surface of all specimens. SCC propagation was mainly transgranular, but SCC propagation of DSS also featured crack ramification in the austenite phase. In addition, SDSS also presented crack propagation along the ferrite/austenite interfaces. Transgranular cleavage fracture was also observed in all fractured specimens, but DSS also presented ferrite/austenite interfacial brittle fracture, while SDSS also featured intergranular brittle fracture. <![CDATA[Failure Theories and Notch Type Effects on the Mechanical Properties of Jute-Glass Hybrid Composite Laminates]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200221&lng=&nrm=iso&tlng= This study aimed to analyze the mechanical properties and damage characteristics in uniaxial tensile loading of two hybrid composite laminates consisting of an ortho-therephthalic polyester matrix reinforced by bidirectional jute fabrics and E-glass fibers, with different configurations and types of geometric discontinuities in the longitudinal section, characterized by the presence of a circular hole and semicircular notches. A semi-empirical study was conducted using the residual properties obtained in mechanical tests, as well as the Point Stress Criterion (PSC) and Average Stress Criterion (ASC) failure theories. This study is based on the calculation of distances (d0 and a0) in the neighborhood of both the hole and the notches, the area of failure stress. The results show the direct influence of geometric discontinuity and residual and modulus strengths in all the parameters studied. With respect to failure theories, only the PSC showed good agreement when the K equal to 2.36 or 2.58 values was used. <![CDATA[Semi-solid Sintering of Ti6Al4V/CoCrMo Composites for Biomedical Applications]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200222&lng=&nrm=iso&tlng= A composite of Ti6Al4V reinforced with CoCrMo particles is fabricated by conventional powder metallurgy and semi-solid sintering. Composites are fabricated by mixing 20% wt. of CoCrMo reinforcing particles into the Ti6Al4V matrix. Sintering is studied by dilatometry tests between 1050 and 1130 °C and compact characterization is performed by SEM and XRD. Microhardness is evaluated on the polished surface in order to obtain the mechanical properties. It is found that densification is achieved by the formation of a liquid phase due to a eutectic point formed by the Ti and Co at around 1130 °C. Composites with 93% of relative density are obtained. Their microstructure is composed by the Ti6Al4V matrix surrounded by a Ti2Co phase. Average microhardness of composites is higher than that obtained for monolithic samples of both alloys. It is assessed that the control of the liquid phase is the key to obtain highly dense composites that could be used as dental or orthopedic implants. <![CDATA[Dependence of Wear and Mechanical Behavior of Nitrocarburized/CrN/DLC Layer on Film Thickness]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200223&lng=&nrm=iso&tlng= Diamond-like carbon (DLC) films are amorphous metastable carbon form that provide interesting mechanical and tribological properties. The role of film thickness influence upon wear and mechanical properties is of interest and not yet fully reported. In this study, two samples of previously plasma nitrocarburized, quenched and tempered H13 steel were duplex treated. First, a physical vapor deposition (PVD) chromium nitride (CrN) layer was applied, followed by a top final diamond-like carbon layer applied by plasma-enhanced chemical vapor deposition (PECVD). To evaluate thicknesses influence on mechanical and wear properties of coatings, samples were treated using two different thicknesses of both layers. In this study, the thickest CrN and DLC case presented higher hardness and better tribological properties, however, its failure occurs in brittle fashion. <![CDATA[Mechanical Behavior of Multiwalled Carbon Nanotube Reinforced 7075 Aluminum Alloy Composites Prepared by Mechanical Milling and Hot Extrusion]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200224&lng=&nrm=iso&tlng= In this paper, multiwalled carbon nanotubes (MWCNTs) were synthesized by spray pyrolysis to be used later as material reinforcement in the production of MWCNTs/Al7075 aluminum composites. Both, MWCNTs and MWCNTs/Al7075 composites were microstructurally and mechanically characterized. Scanning electron microscopy (SEM) analysis shows MWCNTs formed by multiple layers rolled on themselves forming a tube shape with lengths up to 1300 µm and diameters ranging from 55 to 120 nm. MWCNTs were added to the aluminum matrix in different concentrations up to 3.0 wt%. Their dispersion in the aluminum matrix was carried out by ultrasonic/methanol method followed by high-energy mechanical milling process. The effect of MWCNTs on the morphology and mechanical behavior of composites were evaluated. Results indicate that a homogeneous dispersion of CNTs was obtained as a consequence of the dispersion routes used in the production of composites, observing no damage on their morphology. The mechanical behavior of the composites shows a noticeable improvement for MWCNTs concentrations above 2.0 wt%, with ductility similar to that found in the literature for the Al7075 commercial alloy. <![CDATA[Polyhedral Oligomeric Silsesquioxane (POSS) as Reinforcing Agent for Waterborne Polyurethane Coatings on Wood]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200225&lng=&nrm=iso&tlng= Polyhedral oligomeric silsesquioxane (POSS) was added as a reinforcing agent in waterborne polyurethane (WPU)-based coatings to improve their properties. The morphology, structure, thermal stability as well as mechanical properties of the resulting WPU and WPU/POSS hybrid films were investigated. The good compatibility of POSS in the WPU matrices was demonstrated by transmission electron microscopy. Furthermore, Fourier-transform infrared spectroscopy analysis (FTIR) suggested the successful bonding of POSS and WPU matrices. The thermal stability of WPU/POSS hybrids was improved than that of pure WPU according to thermal gravimetric analysis (TGA). The results also revealed the enhancement of the pencil hardness and abrasion resistance of the hybrid films compared with WPU. However, the pull-off adhesion slightly decreased from Grade 0 to Grade 2. <![CDATA[Intumescent Coatings Based on Tannins for Fire Protection]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200226&lng=&nrm=iso&tlng= Accidents involving fire occur every day around the world, affecting thousands of people and causing economic losses. Some accidents are caused by steel structure failures, which experience a significant reduction in mechanical properties at temperatures of 400-550˚C. Therefore, fire protective coatings are required for steel structures and interest in the development of intumescent coatings has increased considerably. In this study, black wattle tannin was used as a carbon source in the formulation of intumescent coatings. Concentrations of 5% and 10% of tannin were incorporated into a novolac resin. The coating was applied on a steel plate and the thermal protection was evaluated by sample exposure to a flame for 30 min. The results showed that the tannin compound could be used as a carbon source for intumescent coatings. The temperature of the samples containing 10% of this compound was almost 300 ˚C lower compared to the uncoated steel plate. <![CDATA[Use of Copper Microparticles in SEBS/PP Compounds. Part 1: Effects on Morphology, Thermal, Physical, Mechanical and Antibacterial Properties]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200227&lng=&nrm=iso&tlng= An alternative for producing thermoplastic elastomers (TPEs) with antibacterial properties is to add copper to the polymeric matrices. This study investigates the effects of the addition of copper microparticles on the morphological, thermal, physical and mechanical behavior and antibacterial properties of a blend composed by styrene-(ethylene-butylene)-styrene triblock copolymer (SEBS) and polypropylene (PP) homopolymer. The cooper microparticles used (commercial grade, produced by electrolytical process) were dispersed in a TPE matrix composed by SEBS/PP. Two bacterial species associated with infections (Escherichia coli and Staphylococcus aureus) were used in the antibacterial assays. The incorporation of copper microparticles in TPE matrix did not promote expressive changes in the thermal, physical and mechanical properties of the compounds. The findings from antibacterial assays showed a reduction of 99.99% in bacterial counts. <![CDATA[Production and Characterization of a Silica-Alumina Membrane Using Novel Tubular Freeze-Cast Substrates]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200228&lng=&nrm=iso&tlng= Development of new ceramic membranes has recently grown due to its superior thermal and mechanical stability. An interesting approach to manufacture asymmetric membranes is the production of aligned pore structure by the freeze-casting method. The lack of studies involving membrane production with tubular freeze-cast substrates warrants more research. In this study, a novel tubular freeze-cast alumina substrate was used for deposition of a silica top layer. The substrate showed radially aligned pores, indicating precise structure control. The obtained pore structure shows high potential for membrane manufacture. The silica layer was produced by the sol-gel method and dip-coated on the substrates with two different withdrawal speeds. The microporous silica showed pores smaller than 2 nm. The highest withdrawal speed resulted in broader substrate coverage. However, a uniform silica layer was only obtained after a second deposition. These results confirm the viability to use tubular freeze-cast substrates for production of nanofiltration membranes. <![CDATA[Desilication of ZSM-5 and ZSM-12 Zeolites with Different Crystal Sizes: Effect on Acidity and Mesoporous Initiation]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200229&lng=&nrm=iso&tlng= In the present work, the desilication of the H-ZSM-5 and H-ZSM-12 zeolites with Si/AL ratios of 28 and 56 and crystal sizes of around 200 and 600 nm, respectively, was performed. Through electron transmission microscopy analysis, it was possible to verify the influence of aluminium gradients on smaller crystals in addition to the exact moment at which the formation of mesoporous is initiated inside the zeolitic framework. Moreover, the crystal size exerts a significant influence on the total amount of acid sites remaining after alkaline treatment, as verified by means of temperature-programmed desorption of ammonia. This is because the presence of larger crystals during desilication may increase the likelihood of reinsertion of aluminium atoms in the zeolite framework and, consequently, maintain the same total amount of acid sites in the zeolite as before alkaline treatment. Meanwhile, aluminium atoms tend to be removed from smaller crystals, thereby decreasing the total amount of acid sites. <![CDATA[PEEK Physical Surface Modification: Evaluation Of Particles Leaching Process]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200230&lng=&nrm=iso&tlng= Polyetheretherketone (PEEK) has been prominent in orthopedic implants; however, it is inert, preventing interaction between the implant and adjacent bone tissues. One way to overcome this characteristic is physical modification its on surface by particle leaching promoting greater osseointegration. The objective of this research was to develop and characterize the PEEK using a surface modification technique via particle leaching. For of the samples, a layer deposition of NaCl was used on PEEK. This was subjected to the pressure of 850 kg/cm2 by 390ºC for 20 minutes. After cooling, were subjected to leaching process particles. The results indicated a porous surface exhibiting uniform and homogeneous morphology with defined pores interconected, to in the range of 140-373 µm, with an average diameter of 273 µm. These evidenced the considerable NaCl removal after the leaching process, with cavities from ideal sizes which promotes adequate cellular accommodation and distinct roughness, giving an overall possibility of being able to obtain a material more able to receive the cells while also possibly presenting cell viability. Although the compressive strength presented low values, it can still be suitable for applications in areas with a reduced modulus of elasticity. <![CDATA[Temperature Dependence of Electrical Resistance in Ge-Sb-Te Thin Films]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200231&lng=&nrm=iso&tlng= Nowadays, the Ge-Sb-Te system is studied extensively for use in the field of both electrical and optical non-volatile memories. The key of this application is based on the changes in the physical properties (electrical conductivity or refractive index) of these films as a result of structural transformation between amorphous and crystalline states. Both states are highly stable and it is relatively easy to change between them when they are prepared as thin films. In this work, structural and electrical behaviours with the temperature of thin films with compositions Ge13Sb5Te82, Ge1Sb2Te4, Ge2Sb2Te5, Ge1Sb4Te7 and Sb70Te30 (atomic fraction) were studied. Films were obtained by pulsed laser deposition (PLD) using a pulsed Nd:YAG laser (λ = 355 nm) and they were structurally characterized by X-ray diffraction. Temperature dependence of electrical resistance was studied for these films from room temperature to 520 K at a heating rate about 3 K/min. During crystallization, their electrical resistance falls several orders of magnitude in a narrow temperature range. The electrical conduction activation energies of the amorphous and crystalline states and the crystallization temperature were determined. The crystallization products were characterized by X-ray diffraction. The results were compared with those obtained by other authors. <![CDATA[Stability, Mechanical Properties and Anisotropic Elastic Properties of Ga<sub>x</sub>Mg<sub>y</sub> Compounds]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200232&lng=&nrm=iso&tlng= The stability, mechanical properties and anisotropic properties of sound velocities of Ga2Mg5, GaMg2, GaMg, O-Ga2Mg, H-Ga2Mg and Ga5Mg2 are investigated systematically by the first-principles calculation. The cohesive energy and formation enthalpy are obtained and used to estimate the stability of the Ga-Mg binary compounds. GaMg compound is the most stable and has the lowest formation enthalpy as -0.162eV/atom of those GaxMgy compounds. The elastic constants of single crystal, hardness, bulk, shear, Young's modulus and Poisson's ratio of the polycrystalline crystal are obtained and used to estimate the mechanical properties. Ga5Mg2 and H-Ga2Mg have the lager bulk, shear and Young’s modulus and corresponding B/G is low. H-Ga2Mg is harder than the other compounds from the results of Poisson’s ratio. The anisotropic mechanical properties are discussed using the anisotropic index, two-dimensional planar projections on different planes of the bulk and Young's modulus. The Young's modulus of H-Ga2Mg shows the strongly anisotropy of mechanical properties and GaMg2 has the weakest anisotropy among all the compounds. <![CDATA[Improvement of Polypropylene Adhesion by Kraft Lignin Incorporation]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200233&lng=&nrm=iso&tlng= Low surface energy and poor adhesion are well-known characteristics of polypropylene (PP). Surface treatments such as plasma, corona, and laser are usually applied to overcome these limitations. However, current studies highlight the incorporation of hydrophilic or amphiphilic polymers into hydrophobic low-surface-energy polymers as an alternative for increasing surface energy and thus improving adhesion. Lignin could be a promising amphiphilic polymer for use in increasing surface energy. In this work, PP/kraft lignin composites were obtained by incorporating up to 5 wt% of kraft lignin (KL) into a PP matrix. Corona treatment was applied to pristine PP and composites surfaces. Contact angle measurements and peeling tests were carried out to investigate the effects of KL incorporation and corona treatment on the surface energy and the mechanical strength of adhesion. Differential scanning calorimetry (DSC) was used to evaluate the PP’s crystallinity index and recrystallization temperature and to dismiss their effects on the surface energy changes. Scanning electron microscopy (SEM) was applied to investigate the lignin dispersion. The results show that KL incorporation has potential as a method to improve the surface energy of PP, improve its poor adhesion, and enhance the effects of corona treatment. <![CDATA[Selective Solar Surface Solar Based on Black Chromium: Influence of Electrodeposition Parameters in the Absorption of Surfaces]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200234&lng=&nrm=iso&tlng= The search for the reduction of costs for the implementation of renewable energies implies in the optimization of the parameters of the manufacturing processes of consolidated technologies. Among these technologies are the solar collectors composed of absorber films characterized by high absorption in the spectrum range corresponding to solar radiation and low emittance in the infrared range, allowing an increase in the collector's operating temperature (300 to 700°C). The present work produced selective surfaces based on black chrome absorber films on stainless steel substrate by electrodeposition. The substrates were immersed in a chromium trioxide bath with hexafluorosilicic acid using a Pb-Sn electrode. In the project some parameters of deposition were evaluated (time, distance and voltage) and their influence on the surface roughness of the coatings obtained by correlating them with the absorptions of the produced surfaces. For this, the surfaces produced were characterized by UV-Vis-NIR, profilometry and SEM. The results indicate that the working distance directly influenced the increase of the films absorption and that the influence of the surface roughness on the film absorption is related to the electrodeposition time as the voltage is raised. <![CDATA[The Modification of (Nd<sub>0.5</sub>Ta<sub>0.5</sub>)<sup>4+</sup> Complex-Ions on Structure and Electrical Properties of Bi<sub>0.5</sub>Na<sub>0.5</sub>TiO<sub>3</sub>-BaTiO<sub>3</sub> Ceramics]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200235&lng=&nrm=iso&tlng= The (Bi0.5Na0.5)0.94Ba0.06Ti1-x (Nd0.5Ta0.5) xO3 (0.01≤x≤0.05) lead-free ceramics (BNBT-xNT) used (Nd0.5Ta0.5)4+ complex-ions to modify its structure and electrical properties. The BNBT-xNT ceramics exhibit the coexistence of tetragonal and rhombohedral phase. The (Nd0.5Ta0.5)4+ complex-ions prohibit grain growth, and its average grain size decreases from 2.53 µm to 0.84 µm with increasing complex-ion content. The NT doping not only induces the transformation from ferroelectric phase to relaxor ferroelectric phase but also decreases the coercive field and remnant polarization. The permittivity curves are broadened at heavily doping content. The energy storage and strain properties are improved by complex-ions. The maximum energy storage density of 0.475 J/cm3 is obtained at x = 0.035 and 60 kV/cm, the energy storage efficiency achieves the maximum efficiency of 61.5% at x=0.05. As increasing complex-ion content, the typical butterfly-shaped strain curve develops into a sprout-shaped one, and the maximum strain of 0.199% is obtained at x=0.02. <![CDATA[Barley Agro-industrial Residues as Corrosion Inhibitor for Mild Steel in 1mol L<sup>-1</sup>HCl Solution]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200236&lng=&nrm=iso&tlng= The corrosion inhibition of mild steel in 1 mol L−1HCl by barley grains and malting process residue extracts was investigated by weight loss measurements, polarization curves, electrochemical impedance measurements and scanning electron microscopy. The inhibition efficiency exceeded 92% in the presence of 100 mg L−1 extracts after 24 h immersion time for both extracts. The Ea decreased with the addition of the extracts, characterizing the chemical adsorption by the molecules present in the extracts on the surface.The high molecular weight fraction isolated from the barley grain extract also showed high inhibition efficiency, suggesting that macromolecules are probably responsible for the inhibitory action. <![CDATA[Effect of Sn Addition in the Microstructure Refinement and Corrosion Resistance of Cu-Zr-Al-Ag Alloy]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200237&lng=&nrm=iso&tlng= In this paper, a composition of known high glass-forming ability, Cu42Zr42Al8Ag8 and a novel Cu42Zr42Al8Ag4Sn4, were produced by suction-casting. After rapid solidification of both alloys, X-ray diffraction patterns along with crystallite size estimation by Scherrer equation and scanning electron microscopy images revealed a refined microstructure, composed mainly by AlCu2Zr, CuZr2 and Cu10Zr7 phases. Transmission electron microscopy indicated the presence of small crystalline precipitates in the Cu42Zr42Al8Ag4Sn4 suction-casted sample. Polarization curves showed a higher passivation current in the Sn containing sample, suggesting a decrease in corrosion resistance. <![CDATA[Investigation on the Wear Properties of Ti/TiC/TiN Composite Coatings Prepared by Powder Cored Wires Through TIG Method at Nitrogen Atmosphere on Titanium Substrate]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392019000200238&lng=&nrm=iso&tlng= In this present study, Tungsten Inert Gas (TIG) welding and powder filled cored wires with nitrogen shielding gas were utilized to produce TiC and TiN surface composite coatings on the titanium (Ti) sheet substrate. The TIG procedure was done at same welding parameters for all of prepared samples. Phase analysis and microstructures were done by X-ray Diffraction (XRD), Energy-Dispersive X-ray Spectroscopy (EDS), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). The obtained results from XRD and EDS demonstrated that the presence of crystalline phases of TiC, TiN and Ti. SEM and OM exhibited formation of the spherical and dendritic TiC particles in a martensitic matrix and also, TiN pinhole areas with rough and collapsed arms. Maximum microhardness value obtained was 571 HV in the case of sample treated with TiC cored wire at 95%argon+5% nitrogen atmosphere. The Pin-on-disk wear tests showed that the coating with maximum hardness had a higher wear resistance due to the presence of fine and hard TiC particles in the high-impact toughness titanium alloy with uniform distribution.