Scielo RSS <![CDATA[Materials Research]]> vol. 18 num. 4 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Synthesis of Poly (2,5-dimethoxyaniline) and Electrochromic Properties]]> Poly(2,5-dimethoxyaniline) (PDMA) was synthesized using electrochemical polymerization of DMA in oxalic acid. The PDMA film coated onto ITO glass was studied for its chemical structure, morphology, electro-deposition, and electro-activity by FT-IR, TGA, SEM, cyclic voltammetry, and UV-Vis spectrophotometry. The PDMA film showed reversible color changes from yellow to blue representing the transition between the fully reduced state to the fully oxidized state upon switching the potentials. The response time of the PDMA film in term of color change was investigated under various applied potentials and different types of acid electrolyte (HCl and H2SO4). The fast response time of less than 2 sec was observed at the applied potential of 1.6 V. In comparison with HCl, the use of H2SO4 as an electrolyte resulted in the fastest response time. Thus, the PDMA is a potential candidate in electrochromic devices due to its reversible color change and fast response time. <![CDATA[Microcosm Biofilm Formation on Titanium Surfaces]]> Risk factors associated with peri-implantitis are related to the biofilm composition around the implant and the ability of bacterial adhesion. This study evaluated the biofilm formation on different surfaces of commercially pure titanium (CP Ti) grade 4 after 12, 24, 48 and 168 hours using the microcosm technique and scanning electron microscopy (SEM). The following surface conditions were examined: S (control)- smooth and plain; B- sand-blasted with aluminum oxide; E- etched using nitric acid; and BE- the combination of J and A treatments. Statistical differences on biofilm formation (CFU/ mg) were found between the control (S) and B surfaces at the first 12 hours, which are related to the lowest (Ra = 0.21 µm) and highest (Ra = 0.62 µm) mean roughness values. At 168-hour all surfaces showed similar biofilm formation. Yet, microbial growth occurred on all surfaces, regardless of the surface treatment. <![CDATA[Thermal Damage in Diamonds: the Protective Effect of Titanium Coating]]> Many of the applications of diamonds expose them to high temperatures and atmospheres containing oxygen. Under these circumstances two important phenomena responsible for the thermal damage of diamonds are: oxidation and graphitization. It is well known that coatings on diamonds provide a better performance, but the amount of information in literature about the protective mechanism of these coatings is very scarce. The present work proposes a study about the thermal damage effect on diamonds with titanium (Ti) coating comparing with diamonds without it. Samples of uncoated diamonds and Ti- coated diamonds were heat treated at 1200 °C during different periods of time and characterized prior to and after the treatments. Differential thermal analysis (DTA) was performed to observe the temperatures that transformations in diamonds occur. The analysis of phases present in the samples and the observation of new phases formed were carried out by means of X-ray diffraction (XRD). In order to observe the diamond surface and how the chemical elements are distributed in it, the samples were analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results prove the protective capability of the Ti coatings, clarifying the protective mechanism against the thermal damage. <![CDATA[The Recycling of Sugarcane Fiber/Polypropylene Composites]]> Mechanical recycling is utilized to reuse waste and obtain other plastic products via the reprocessing of a material in industrial equipment. Natural fiber composites have become more popular in recent years; however, these composites' mechanical behavior remains less well-understood than single polymers’ behavior after recycling. Therefore, the objective of this work was to study the degradation of different sugarcane fibers/polypropylene composites using new grinding and injection processes and to evaluate the mechanical properties of these materials using analysis of variance (ANOVA). This work reveals the mechanical behaviors of recycled natural fiber composites that contain thermal stabilizer additives. Polypropylene composites reinforced with differently treated bagasse and straw fibers (10 and 20 wt%/PP) were obtained through melt mixing using a high-intensity thermokinetic mixer and were subsequently injected. The recycled composites exhibited decreased tensile strength relative to the original composites. However, when thermal stabilizers were added, the mechanical properties were maintained or increased, depending on the fiber and additive types. <![CDATA[Geopolymer/PEG Hybrid Materials Synthesis and Investigation of the Polymer Influence on Microstructure and Mechanical Behavior]]> Geopolymers are aluminosilicate inorganic polymers, obtained from the alkali activation of powders containing SiO2+Al2O3&gt;80wt%, mainly proposed as environmentally friendly building materials. In this work, metakaolin-based geopolymers have been prepared and a water-soluble polymer, polyethylene glycol (PEG), has been added in different percentages to obtain organic-inorganic hybrid geopolymers. The influence of both the polymer amount and aging time on the structure and the mechanical behavior of the materials were investigated. FTIR spectroscopy allowed us to follow the evolution of the aluminosilicate framework during the geopolymerization process. This analysis revealed that PEG leads to a network which is rich in Al-O-Si bonds and forms H-bonds with the inorganic phase. SEM microscope showed that the two phases are interpenetrated on micrometric scales. Traction and bending tests have been carried out on appropriate samples to investigate the mechanical behavior of the obtained hybrids, showing that both PEG content and aging time affect the material behavior. <![CDATA[The Effect of Immersion Time and Immersion Temperature on the Corrosion Behavior of Zinc Phosphate Conversion Coatings on Carbon Steel]]> The formation and corrosion performance of zinc phosphate coating on carbon steel at different temperatures and immersion times was studied. The corrosion performance of coatings was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. The characterization and composition of coatings were studied by SEM and EDS analysis. The corrosion resistance in 3.5%wt. NaCl solution was increased in the presence of zinc phospoate conversion coatings. The effect of immersion time and coating temperature were studied on anti-corrosion behavior of coatings. Coating temperature showed a significant effect in phosphate conversion coating and higher corrosion resistance was obtained with 45 ºC operating temperature. Also the experimental results indicated that the corrosion resistance increased with increasing the immersion time. This behavior can be related to the increase of the phosphate coating continuity which formed on the surface. Surface analysis results indicated that the coating obtained from 20 min immersion time was more uniform and continuous. <![CDATA[Synthesis Optimization of MCM-41 for CO<sub>2</sub> Adsorption Using Simplex-centroid Design]]> There is a growing concern on the relationship between anthropogenic carbon dioxide and climate changes. A promising approach is the adsorption technology using mesoporous MCM-41 materials that can be easily synthesized to depict structures adequate to the flow of gas. The aim of this study was to improve the synthesis of MCM-41 using cationic surfactant mixtures and apply the resulting materials to CO2 adsorption. To that end, the simplex-centroid design was applied to optimize CO2 adsorption from seven mesoporous MCM-41 materials synthesized by the hydrothermal method using surfactants from hydrophobic chains of different sizes. The cationic surfactants used were tetradecyltrimetylammonium bromide, cetyltrimethylammonium bromide, trimethyloctadecylammonium bromide and their mixture at ratios of 1:1 and 1:1:1. The CO2 adsorption was investigated using thegravimetric method at 298 K and pressures up to 40 bar. The resulting materials, labelled C17, C19, C21, C17C19, C19C21, C17C21 and C17C19C21, were characterized by XRD, FTIR, TG and SEM and showed significant differences in structure as well as in the mass of CO2 adsorption. The response models showed that the best combination of the surfactants resulted from C17C19 sample, which presented synergistic interactions reaching the highest value of CO2 adsorption (0.62 g CO2/g adsorbent), compared to other samples. <![CDATA[Mechanical and Corrosion Properties of a Duplex Steel Welded using Micro-Arc or Laser]]> Duplex stainless steels have been extensively used in parts that are subject to corrosive environments and that have high mechanical strength requirements. Welding usually distorts the well-balanced austenite-ferrite ratio, and can produce brittle intermetallic phases; therefore, post-welding heat treatments are usually required. For applications where post-welding treatments are not possible, low heat input methods, such as micro-tungsten inert gas welding (TIG) and laser beam welding (LBW), can be used. The present investigation analyzed the microstructure, mechanical, and corrosion properties of 2507-classduplex steel tubes after welding. The microstructures of the heat-affected zones and the fusion zones contained variable amounts of ferrite and austenite. In the heat-affected and fusion zones in the TIG samples, the microstructures were primarily composed of ferrite grains with allotriomorphic austenite at the grain boundaries, intragranular Widmanstätten needles and plate-like precipitates. The LBW samples showed much finer microstructures, which contained austenite in the grain boundaries and fine austenite precipitates in the ferrite grains. Deleterious intermetallic phases, such as σ-phases, were not observed using X-ray diffraction. The tensile strength properties were very similar for the TIG and LBWsamples, reaching tensile strengths of approximately 840 MPa and total elongations between 61 and 87%. The heat-affected zone of the TIG welds were particularly susceptible to corrosion (0.05 mm/year) compared to the base metal (0.007 mm/year) and the laser welds (0.01 mm/year). Therefore, laser welding is a promising technique for the welding of 2507-class duplex tubes. <![CDATA[Nickel-based Catalyst Precursor Prepared Via Microwave-induced Combustion Method: Thermodynamics of Synthesis and Performance in Dry Reforming of CH<sub>4</sub>]]> Nickel-based catalyst precursor for dry reforming of methane was successfully prepared by a self-combustion method. Three different amino acids: urea, glycine and citric acid were tested as fuels in the redox reaction with metal nitrates. For each fuel, a thermodynamic modeling of the combustion reaction was performed. The samples were characterized by X-ray diffraction (XRD), Thermogravimetric analysis (TG), Scanning electron microscopy (SEM), Attenuated total reflectance – Fourier transform infrared (ATR-FTIR) spectroscopy and Temperature-programmed reduction (TPR). XRD data confirmed the presence of several crystalline phases in the as-prepared powders. The sample prepared with citric acid showed very low crystallinity when compared to the other samples. It was found that the heat release rate of the self-combustion is the determinant factor of the crystallization, and it is fuel dependent. SEM results suggest that the distribution and average particle size of as-prepared powders can be controlled by the appropriate selection of the fuel. Further calcination of these samples at 800 °C/4h led to the crystallization of perovskite-type structure LaNiO3. Nanostructured Ni0/La2O3 obtained after reduction of LaNiO3precursor showed high catalytic activity in dry reforming of methane. <![CDATA[Influence of Deleterious Phases Precipitation in the Corrosion Resistance Measured by Double Loop Electrochemical Polarization Reactivation Test in Superduplex Stainless Steel]]> This work investigates the influence of deleterious phases precipitation on the corrosion resistance of two wrought superduplex stainless steels UNS S32750 with similar composition, but different grain sizes. Isothermal treatments were carried out to introduce different amounts of deleterious phases, such as chi (χ), sigma (σ) and secondary austenite (γ2). The specimens were tested by double loop electrochemical potentiodynamic reactivation test (DL-EPR). The kinetics of precipitation in the two steels was different due to the difference of the grain sizes. The results show a correlation between the sensitization degrees, measured by DL-EPR, with the amount of deleterious phases precipitated. <![CDATA[Preparation and Characterization of PA66/Alumina Composite Membrane]]> In this study, polymer/ceramic composite membranes were prepared and characterized. The polymer used was polyamide 66 (PA66) deposited by dip coating on the inner surface of α-alumina-based (Al2O3) microporous tube. A coating on the ceramic support surface and the formation of the selective layer was analyzed by scanning electron microscopy (SEM) in membranes with one (PA-1) and two layers (PA-2). The results of mercury porosimetry showed that the deposition of the polyamide layers decreases the average pore size. The PA-1 presented an average pore size of 0.35 μm, while the PA-2 presented two peaks of 0.18 and 0.56 μm. Both showed a superior performance than the ceramic support (pore diameter of 0.65 μm). Although, the permeate flux was higher with an impregnation membrane, the number of layers (one or two) just introduced a slight difference in pore statistical analysis. The order of rejection coefficient values for protein molecules is BSA &gt; egg albumin &gt; trypsin. The permeation tests showed that the composite membrane can be applied in ultrafiltration processes with MWCO of 69 kDa. <![CDATA[Large Scale Synthesis of Superparamagnetic Face-centered Cubic Co/C Nanocapsules by a Facile Hydrothermal Method and their Microwave Absorbing Properties]]> A large scale direct hydrothermal method has been used to prepare face-centered cubic (FCC) Co/C nanocapsules with a core of FCC-Co nanoparticles and a shell of amorphous C. The size distribution is 5-20 nm. The TB of FCC-Co/C nanocapsules is determined as 85 K, indicating that FCC-Co/C nanocapsules are superparamagnetic at 300 K. For FCC-Co/C nanocapsules-paraffin composite, an optimal reflection losbs (RL) of -33.4 dB is observed at 9.6 GHz for the 2.6 mm thick layer. RL values exceeding –20 dB in the 7.4 –15 GHz range are obtained by choosing an appropriate absorption-layer thickness between 1.7 and 3.3 mm. The good microwave absorbing properties of FCC-Co/C nanocapsules is considered to result from the excellent synergetic effect of the multi-dielectric relaxation loss and the multi-magnetic resonance loss. Quantitative calculation demonstrated that not only RL peak position but also the number of the peaks are determined by the quarter-wavelength cancellation model. <![CDATA[Effect of Weathering and Accelerated Photoaging on PET/PC (80/20 wt/wt%) Melt Extruded Blend]]> In this study we investigated the natural weathering of a catalyzed blend of poly(ethylene terephthalate)/polycarbonate PET/PC (80/20wt/wt%). The results were compared to the accelerated photoaging tests. The specimens were characterized by wide angle X-ray diffraction (WAXD), optical microscopy (OM), thermogravimetry (TG/DTG), medium infrared spectroscopy (FT-IR) and stress-strain analysis. The OM analysis revealed the coexistence of at least three phases – one rich in PET (matrix), the other rich in PC (dispersed droplet) and an interfacial region between them, made of PET/PC copolymer (compatibilizing agent) produced in situ. The TG/DTG curves showed that UV radiation acted mainly on the PET-rich phase and the PET/PC copolymer. The OM and TG/DTG results indicated that the degradation of the compatibilizing agent has had a critical effect on the mechanical properties. For both types of aging (natural and accelerated), the PET’s carbonyl index decreased with the exposure time. The FT-IR results corroborated what was seen in the OM images, showing that the PET phase acts as a shield against the PC degradation. Under accelerated aging, the mechanical properties decreased abruptly - mainly the stress-strain at yield and break - due to the degradation of the in situ compatibilizing agent. <![CDATA[Experience on a Low Cost Way to Obtainal-Ti Ceramic Foams]]> An experience on a simple process for producing alumina-rutile-mullite ceramic foams by using aqueous particulate slurries is proposed. The sintering process is achieved in one unique thermal process at 1200 ºC in air. The description of the process, physical properties and morphological studies are reported. Microstructure is studied by using confocal optical microscopic technique. The highly active porous foam structure of this ceramic material produced according to the low-cost process presented here could extend its use in a broad range of applications, such as catalytic, biomedical scaffolds, filtering, etc. <![CDATA[Multilayer Graphene Films Obtained by Dip Coating Technique]]> A dip coating system was projected and constructed to deposit a large range of thin films onto solid substrates. A microcontroller was used to control the deposition system. As an example of application multilayer graphene (MLG) films were deposited onto glass slices in order to obtain conductive films with relatively good light transmittance. The MLG flakes were obtained using natural graphite and isopropyl alcohol resulting in three dispersions treated in ultrasound for 30, 60 and 90 minutes, respectively. Using atomic force microscopy, UV-Vis spectrometry and an electrometer the film characterizations were performed. MLG flakes about 13 nm thick, 10 mµ2 of area were observed using AFM. In films obtained with 35 immersions the electrical resistance and the resistance sheet reached 1.8 kΩ and 1.9kΩ/square respectively. The light transmittance reached 10-20% while films obtained with dispersions treated for 60 and 90 minutes were electrically continuous. Thus, conductive films can be used in chemiresistor sensors, electrochemical and supercapacitors electrodes. <![CDATA[Sorbitol-Plasticized and Neutralized Chitosan Membranes as Skin Substitutes]]> Chitosan is soluble in diluted acid solutions and can easily form films by casting. However, residual acid neutralization should be performed for biomedical applications what may compromise physical and mechanical properties of the films. Thus, plasticizers can be added to improve these properties. The aim of this study was to characterize morphological, barrier and mechanical properties, besides evaluate the in vitro cytotoxicity of sorbitol-plasticized and NaOH-Na2CO3 neutralized chitosan membranes for skin substitute application. Scanning electron microscopy, X-ray diffraction, water vapor permeability and mechanical tests were carried out to characterize the obtained membranes. Moreover, Vero cells were used for in vitro cytotoxicity evaluation. In this paper, we report a non-cytotoxic sorbitol-plasticized chitosan membrane with desirable properties for skin substitution, such as flexibility, water vapor permeability and high percentage of elongation. <![CDATA[The Role of Carbon Black on Devulcanization of Natural Rubber by Microwaves]]> One of the greatest problems of the modern society is the recycling of vulcanized elastomers, like tires and industrial rejects. This work studies one of the techniques of devulcanization of natural rubber (NR), the devulcanization by microwaves, as well as the influence of the amount of carbon black on this process through devulcanization of the NR with controlled composition on it. The samples were analyzed by Soxhlet extraction and some important correlations could be made based on its results and also by the final temperature of the samples just after the time of exposure to microwaves. The results highlighted that the increase of the temperature is responsible for the occurrence of devulcanization, which is dependent on both the amount of carbon black present in the rubber and the time of exposure to microwaves. These factors can influence its degree of devulcanization, since they are important for the absorption of energy by the material. <![CDATA[A ‘Universal’ Bottom-up Sol-gel Based Synthesis of Pzt (1-x)/x Submicrometric Structures: 1. Dynamic Light Scattering Characterization of Precursor Stability and Aggregation Kinetics]]> This work proposes an extension of a sol-gel based synthesis route for obtaining highly hydrophobic, uniformly nanosized and stable precursor solutions of lead zirconate titanate [Pb(Zr1-xTix)O3 or PZT (1-x)/x] for any given (1-x)/x Zr:Ti ratio. Several representative PZT compositions were chosen and their precursors were studied by taking into account the time dependence of the mean particles size andthe predominant aggregation kinetics. Size distributions were recorded by the Dynamic Light Scattering technique and the aggregation kinetics was explored by considering a Diffusion-Limited Colloidal Aggregation model. Transmission electron microscopy was also used to characterize some morphological features of our resultant precursor nanoparticles. Our final results supports the universalization of this approach to any PZT composition and its extension to other material systems. This work is intended to be the first on a series dealing with the sol-gel based synthesis of any PZT material at any scale using a bottom-up approach. <![CDATA[Formation of Mo−Si−Ti Alloys by Self−propagating Combustion Synthesis]]> Test specimens with nominal compositions MoSi2, (Mo0.9Ti0.1)Si2, (Mo0.8Ti0.2)Si2, (Mo0.7Ti0.3)Si2, (Mo0.6Ti0.4)Si2, (Mo0.5Ti0.5)Si2 and (Mo0.4Ti0.6)Si2 were prepared by combustion synthesis. The combustion mode, propagation velocity of combustion wave, combustion temperature and product structure were investigated. Specimens MoSi2, (Mo0.9Ti0.1)Si2, (Mo0.8Ti0.2)Si2, (Mo0.7Ti0.3)Si2, underwent spontaneously self−propagating combustion synthesis. However, the (Mo0.6Ti0.4)Si2 and (Mo0.5Ti0.5)Si2 specimens required a sustainable energy supply to complete the combustion synthesis reaction. There was no combustion synthesis reaction in specimen (Mo0.4Ti0.6)Si2. The combustion wave propagated along a spiral trajectory from top to the bottom of the specimen compacts in a layer by layer mode. The propagation velocity of the combustion wave reduced with the addition of titanium. The X-ray diffraction analysis showed that the Cllb-MoSi2 and C40-(Mo,Ti)Si2type phases were formed during combustion synthesis. The intensity of diffraction peaks of C40-(Mo,Ti)Si2 phase increased with Ti content. <![CDATA[Synthesis, Characterization and Dry Sliding Wear Behavior of In-situ Formed TiAl<sub>3</sub> Precipitate Reinforced A356 Alloy Produced by Mechanical Alloying Method]]> In this present study, the effect of in-situ formed TiAl3 and AlTiSi intermetallic phases within A356 aluminum alloy on the dry sliding wear behaviors was investigated. The TiAl3 and AlTiSi intermetallic phases were obtained by synthesizing A356 aluminum alloy containing 6% titanium for different times (1, 4, 8 and 16h). The cold pressed samples were sintered in an argon atmosphere at 530 °C for one hour (10 °C/min.) and then cooled in the furnace. The sintered samples were synthesized at 550 °C for different times (1, 4, 8 and 16h), and the in-situ aluminum matrix composites (AMCs) were produced. Wear tests of the AMCs were performed under 30 N load and at 1 ms-1sliding speed for five different sliding distances. As the result of the studies performed, formation of in-situ TiAl3 and AlTiSi intermetallic phases were detected. With the increase in synthesizing time, the porosity in the structure was found to be reduced. In addition, it was observed that the densities and hardness of the composites increased depending on the synthesizing time. The wear test results revealed that increasing hardness values of A356 + 6% Ti AMCs decreased the weight loss. <![CDATA[Acoustic Characterization of Sugarcane Bagasse Particleboard Panels <em>(Saccharum officinarum L)</em>]]> The use of sugarcane bagasse minimizes the environmental impact and contributes to the creation of a new product with low density, good sound absorption capacity and can improve the acoustic conditions of buildings. The goal of this study aims to determine the intensity response of sugarcane bagasse particleboard panels’ sound absorption and compare them with particleboard panels of the species Pinus sp. and Eucalyptussp. To accomplish this, the sound pressure levels in different frequency bands were analyzed. The results showed higher sound absorption between the low and high frequency bands for the three types of panels, with an absorption peak in 315 Hz identifying the characteristic frequency of resonance from these materials. However, the sugarcane bagasse panel presented differently than the others, with a greater retention of sound energy in the medium frequency band between 630 Hz and 1,000 Hz with a maximum absorption at 55 dB at the frequency of 800 Hz. Keywords: sugarcane bagasse, particleboard, sound absorption, acoustics <![CDATA[Analysis on the Growth and Characterization of a Non-linear Optical Single Crystal: L-Cystine Dihydrobromide]]> Nonlinear optical single crystals of L-cystine dihydrobromide (LCHB) have been grown by slow evaporation method. Single crystal X-ray diffraction analysis revealed the crystal system and lattice parameter values. Powder X-ray diffraction analyses have been carried out and the diffraction patterns have been indexed. Fourier transform infrared (FTIR) analysis confirms the various functional groups present in the grown crystal. The thermal behavior of the grown crystal was investigated by DTA and TGA analysis. The optical properties of the crystals were determined using UV-Visible transmittance spectrum. The dielectric constant and dielectric loss of the crystal are studied as a function of frequency for various temperatures. The SHG efficiency of the crystal is studied using the Kurtz and Perry technique. <![CDATA[Mechanical Properties Analysis of Polypropylene Biocomposites Reinforced with Curaua Fiber]]> Over the last few years, great interest has been shown by researchers in presenting alternative proposals for the design and fabrication of materials with good mechanical properties and low cost for a variety of applications. With this in mind, a study was carried out on the addition of curaua fibers in a polypropylene (PP) matrix. These were extruded in the pellets form with curaua fiber content of 5, 10 and 20% (mass percentage). An injector was used to make the test specimens from these pellets, which were then subjected to mechanical tests (tensile and three point bending), physical and thermal tests (fluidity index and HDT). As a consequence, it was noted that the incorporation of fibers in composites of PP with curaua resulted in an increase in the elastic modulus and tensile strength improving therefore the mechanical properties of these materials. Another important point was to check if there was an increase in heat deflection temperature as the fibers were added. As a result, it has been found that it is feasible to use these materials in industry, facilitating its recycling and improving its final mechanical properties. <![CDATA[Surface Finishes for Ti-6Al-4V Alloy Produced by Direct Metal Laser Sintering]]> The implant’s surface is responsible for direct interaction with the human body. For cases where osseointegration must be favored and the risk of bacteria proliferation is lower, rough surfaces are more suitable, while for implants where the risks are higher, a reduced surface roughness is required. This study aimed to analyze and produce different surface finishes on samples of Ti-6Al-4V alloy produced by additive manufacturing technique of Direct Metal Laser Sintering (DMLS). Surfaces of the samples were analyzed in the as-built condition, after blasting, after chemical etching, after electropolishing and two different combinations of these methods. The surfaces were studied using the technique of scanning electron microscopy, and surface roughness and mass measurements. The lower roughness value was obtained after a combination of blasting and chemical etching. Blasting results in a surface with uniform roughness while chemical etching cleans the surface and reduces its roughness. <![CDATA[Microstructural and Micromechanical Effects of Cold Roll-forming on High Strength Dual Phase Steels]]> In this work correlation between the 1000 MPa dual phase (DP) steel microstructure and the strain gained after roll-forming process have been studied by both microstructural and micromechanical analysis. The scanning electron microscope (SEM) inspection in the bent area reveals changes in the ferrite-martensitic microstructure. The plastic deformation of DP steels originates defects at the edges of bent sheet make them partly responsible for the damage caused. In addition, electron backscatter diffraction (EBSD) measurements have been carried out for an in-depth characterization after roll-forming. A high density of misorientation of the crystal lattice within the ferrite strained grains is observed, mainly concentrated in the ferrite/martensite grain boundaries. Furthermore, the ultramicrohardness tests exhibit little dependence between mechanical parameters and the material properties. <![CDATA[Nanostructured Titanium Film Deposited by Pulsed Plasma Magnetron Sputtering (Pdms) on a High Voltage Ceramic Insulator for Outdoor Use]]> In this study, the cold plasma technique was used to produce nanometric titanium films with hydrophobic and anti-fouling properties. The films where deposited on porcelain electrical insulators surfaces to minimize the effects of leakage current. The magnetron sputtering technique was used with a target of pure titanium sheet, and argon as the ionization gas. The deposited films present an average thickness of 58 to 350 nm. After coating the insulators, the assays performed indicated a greater degree of hydrophobicity and maintenance of leakage current after exposure to salt spray. Lower leakage current values were observed in both natural and saline environments compared with the uncoated device. <![CDATA[Syntesis of Carbon Nanostructures Near Room Temperature Using Microwave PECVD]]> Carbon nanostructures (nanotubes, nanofibers and nanosponges) were synthesized onto Si (001) substrates using a microwave assisted plasma enhanced chemical vapor deposition (PECVD) from C2H2-Ar mixtures at low substrate temperatures (120 °C). Catalytic films (Ni and Cu) 3 nm thick were used. Different structures were formed, depending on the C2H2 partial pressure. Atomic force microscopy (AFM) and scanning electron spectroscopy (SEM) were employed for the morphological characterization of the catalytic films and the carbon nanostructures, respectively. Raman spectroscopy was used to identify carbon hybridization states. AFM was used to observe the morphology of the catalytic films. At low C2H2 partial pressures, nanotubes with nanospheres in their tips, growing from nanoholes were seen. With increasing C2H2 pressures, longer nanotubes were observed, reaching lengths from 300 to 500 nm. In their growth, the nanotubes laterally touch each other, forming nanotube bundles, or nanofibers. For the higher C2H2 partial pressures, dense sponge-like (nanosponge) structures, consisting of a large number of bundles, are formed. From the Raman spectra, a mixture of sp2 and sp3 hybridizations were identified. Furthermore, the low substrate temperature at which depositions can be carried out, makes possible growth of carbon nanostructures on materials to which high temperatures would be deleterious. <![CDATA[Fabrication and Characterization of Antibacterial Polyurethane Acrylate-based Materials]]> In this paper, the fabrication of the photocured materials which contained silver nanoparticles (Ag-NPs) was studied on the properties of materials such as physical, mechanical and thermal properties, especially antibacterial activity. Therefore, silver nanoparticles were prepared and added into the polyurethane based matrix. Chemical and morphological structures of the photocured materials were characterized by FTIR and SEM analysis. SEM images proved the size of the silver nanoparticles and their dispersion into polymer matrix. Thermal, mechanical and optical properties of photocured materials results showed that the prepared polymer compositions containing Ag-NPs exhibited high modulus and better thermal property. Moreover, the antibacterial properties of the polyurethane based materials and polymer material containing AgNPs were determined and these AgNPs containing photocured materials pointed out good antibacterial activity against Escherichia coli and Staphylococcus aureus. <![CDATA[Crack Propagation Analysis of Magnesium Rod Processed by Extrusion-shear: Numerical Modeling and Experimental Verification]]> During extrusion-shear (ES) process, the surface cracks would be formed in the processed rod for AZ31 magnesium caused by nonhomogeneous metal flow and stress. To reduce the cracks defects, three-dimensional (3D) finite element method (FEM) of ES on a wrought AZ31 magnesium alloy have been performed. ES process experiments have been also conducted to verify the simulation results under the identical conditions. It can be found that the tendency to generate the dead zone is decreased by employing the ES die with the extrusion ratio of 28 comparing to the one with the extrusion ratio of 11.6. With the extrusion ratio 28, the surface stresses of the rod at the die exit are decreased greatly so that the surface cracks are avoided. The ES die with the extrusion ratio of 28 would increase temperature on the rod surface and subsequently result in the sacrifice of the tensile strength of the AZ31 rod. Damage model has been chosen and Cockcroft–Latham damage factor has been set and incorporated into DEFORM software. The simulation results show that the larger extrusion ratio would have the smaller crack propagation. Experimental validation shows that the results of experiments are in accordance with those from computer simulation. The study indicates that FEM can be used confidently for designing ES dies and process parameters in CAE environment for DEFORM software to improve the product quality and productivity by avoiding trail runs. <![CDATA[Crystallographic Aspects Regarding the Insertion of Ag<sup>+</sup>Ions into a Hydroxyapatite Structure]]> The objective of this study was to evaluate how silver can be inserted into hydroxyapatite (HA) via two distinct processes: co-doping with CO32- via precipitation in an aqueous medium and immersion of preformed HA crystals into Ag+ solutions. It was concluded that although Ag+ and Ca2+ have different radii, the accommodation of Ag+ ions in the Ca2+ sites of the hydroxyapatite lattice can be explained by the models proposed for inserting monovalent ions such as Na+. In this case, because Ag+ions are larger than Ca2+ ions and have a different charge, the Ag+ ions are stabilized in the HA structure by co-substitution with CO32- ions in both the A- and B-type sites. This simultaneous insertion of Ag+ and CO32- appears to thermally stabilize the HA phase because no phase transformation is observed after calcination. In addition, the doping of HA with Ag+ ions can clearly occur via two routes: co-precipitation in the presence of these ions or diffusion in preformed hydroxyapatite crystals. This result appears to indicate the possibility of doping HA with Ag+ using less complex routes at ambient temperature and with prefabricated implants or biomaterials, which reduces the costs of producing devices with antibacterial effects.