Scielo RSS <![CDATA[Materials Research]]> vol. 18 num. 5 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Evaluation of Aging in Air of Poly (Ethylene Terephthalat) in Oxygen Plasma]]> AbstractPolyester fabric samples – PET (poly (ethylene terephtalate)), were treated with oxygen plasma, in order to alter the hydrophilicity of such material. The process parameters: working pressure, current, tension and temperature were kept constant, varying only the treatment time. In order to evaluate the change caused on samples hydrophilicity, as well as the influence of the treatment time, the vertical wicking test was used. The samples were stored at standard temperature and pressure conditions, and their wettability were measured one day after the treatment and repeated after 30, 60 and 360 days, in order to check the stability of the effects produced. Scanning electron microscopy (SEM), Raman and ATR (Attenuated total reflection) spectroscopies were used to evaluate physical and chemical alterations on the samples surface. The results have shown a substantial improvement on the hydrophilicity of the treated samples compared to the non-treated sample. <![CDATA[Influence of the Addition of Montmorillonite in an Epoxy Powder Coating Applied on Carbon Steel]]> AbstractPolymer coatings have been used for the corrosion protection of metal surfaces acting as a physical barrier against several corroding media. In spite of the good efficiency of these coatings their resistance is limited due to the presence of localized defects which give place to localized corrosion. Aiming to improve the barrier properties of these coatings this work has proposed the use of nanocomposites as powder coatings based on a standard formulation of a commercial powder varnish. Nanocomposites with 2 and 4 wt% contents of organophilic montmorillonite (OMMT) were obtained in the molten state through of a co-rotating twin-screw extruder. The application of the nanocomposite coatings was performed by electrostatic pulverization on mild steel panels. The coatings were characterized to determine their structure using X-ray diffraction (XRD). The morphologies of the coatings were assessed using transmission electron microscopy (TEM). Gloss and adhesion measurements and the flexibility and impact resistance of the coatings were included in the physical assessment of the coatings. The corrosion performance was evaluated by the salt spray test and by electrochemical impedance spectroscopy (EIS). The coatings with clays presented predominantly exfoliated structures, with good dispersion of OMMT in the epoxy matrix. The addition of OMMT reduced the impact resistance, flexibility and gloss but increased the barrier properties of the coatings. The best corrosion performance in NaCl solution was achieved for 4 wt% OMMT. <![CDATA[Use of Cr Interlayer to Promote the Adhesion of SiC Films Deposited on Ti-6Al-4V by HiPIMS]]> AbstractIn this paper, chrome (Cr) thin films were deposited and used as interlayer between SiC films and Ti-6Al-4V substrates. Films and interlayers were obtained by using HiPIMS (High Power Impulse Magnetron Sputtering) technique. Interlayers were growth for 5, 30, and 60 minutes. The films were analyzed with respect to morphology, stoichiometry, thickness, roughness, and adhesion. The results showed that the HiPIMS technique was efficient to produce dense thin films and that the adhesion increased with Cr thickness. <![CDATA[Formation of Microphases and Constituents from Remaining Austenite Decomposition in API X80 Steel Under Different Processing Conditions]]> AbstractThe main goal this work is to evaluate the occurrence of the constituents and microphases observed in as-received API X80 pipe through the microstructures transformed from rich-carbon remaining austenite obtained via heat treatments. These heat treatments comprised austenitization at 1000 °C for 30 minutes, followed by annealing at 700 °C, 623 °C, 542 °C and 462 °C for 15, 60 and 300 minutes and then cooling in water or still air. The effects of the increase in annealing parameters were: 1) the increase of microhardness values of the MA constituents and martensite islands, 2) the grain size of both ferritic phase and the martensite islands were increased, 3) the rise in the mean free path of ferrite and 4) the microstrains of samples were decreased. The cooling rates influenced significantly the transformation of carbon-rich remaining austenite to hard constituents and several microphases. After annealing at 700 °C during 60 min followed by quenching, the morphology of the MA constituents and its microhardness values were compatible for both heat-treated and as-received conditions. <![CDATA[Mechanical Characterization and FE Modelling of a Hyperelastic Material]]> AbstractThe aim of research work is to characterize hyperelastic material and to determine a suitable strain energy function (SEF) for an indigenously developed rubber to be used in flexible joint use for thrust vectoring of solid rocket motor. In order to evaluate appropriate SEF uniaxial and volumetric tests along with equi-biaxial and planar shear tests were conducted. Digital image correlation (DIC) technique was utilized to have strain measurements for biaxial and planar specimens to input stress-strain data in Abaqus®. Yeoh model seems to be right choice, among the available material models, because of its ability to match experimental stress-strain data at small and large strain values. Quadlap specimen test was performed to validate material model fitted from test data. FE simulations were carried out to verify the behavior as predicted by Yeoh model and results are found to be in good agreement with the experimental data. <![CDATA[Influence of Boriding Process in Adhesion of CVD Diamond Films on Tungsten Carbide Substrates]]> AbstractThis paper shows successful hindering of the negative effects of the cobalt binder in the process of coating WC-Co cutting tools with CVD diamond films. The strategy was creating a boron-rich layer on the surface of the WC-Co substrates as an interlayer to block Co migration. The traditional boriding technique was improved by preheating the salt powders and controlling the brittle region thickness in the substrate surface. These procedures produce a tougher surface for diamond growth. Adding CF4 to the gas mixture also enhanced diamond adhesion to the surface. The adhesion of diamond films to WC-Co substrates was evaluated by indentation tests. Samples were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), X-ray Diffraction (XRD) and Raman Scattering Spectroscopy (RSS). <![CDATA[Radiation Induced Synthesis of In<sub>2</sub>O<sub>3</sub>Nanoparticles - Part II: Synthesis of In<sub>2</sub>O<sub>3</sub> Nanoparticles by Thermal Decomposition of Un-irradiated and γ-irradiated Indium Acetylacetonate]]> AbstractPure cubic phase, In2O3 nanoparticles with porous structure were synthesized by solid state thermal oxidation of un-irradiated and γ-irradiated indium acetyl acetonate in presence and absence of sodium dodecyl sulphate as surfactant. The as- synthesized In2O3nanoparticles were characterized by X-ray diffraction (XRD), fourier transformation infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transition electron microscopy (TEM) and thermogravimetry (TG). The shapes and morphologies of as- synthesized In2O3nanoparticles were highly affected by γ-irradiation of indium acetyl acetonate precursor and by addition of sodium dodecyl sulphate as surfactant. Calcination of un-irradiated indium acetyl acetonate precursor to 4 hours of 600 °C leads to the formation of spherical- shaped accumulative and merged In2O3 nanoparticles with porous structure, whereas irregular porous architectures composed of pure In2O3nanoparticles were obtained by using γ-irradiated indium acetylacetonate precursor. The as- prepared In2O3 nanoproducts exhibit photoluminescence emission (PL) property and display thermal stability in a wide range of temperature (25-800 °C) which suggest possible applications in nanoscale optoelectronic devices. <![CDATA[One-step Synthesis of Ag<sub>3</sub>PO<sub>4</sub>/Ag Photocatalyst with Visible-light Photocatalytic Activity]]> AbstractA highly efficient photocatalyst Ag3PO4/Ag was prepared by a one-step low temperature chemical bath method. The reflectance spectra (DRS) indicated Ag3PO4/Ag had strong absorption in visible light region. The synthesized Ag3PO4/Ag photocatalyst was used as the efficient photocatalysts for the photocatalytic degradation of Rhodamine B (RhB) under visible-light illumination which showed almost complete degradation (~ 98%) of RhB dye in 90 min. The negative surface of Ag3PO4/Ag photocatalyst also promoted the degradation of a cationic dye like methylene bule (MB; 78% in 90min), while the performance against an anionic dye like methyl orange was poorer (MO; 40% in 90 min). Compared to the pure Ag3PO4 photocatalyst, the Ag3PO4/Ag photocatalyst showed the enhanced visible light photocatalytic informance. The excellent photocatalytic performance is mainly ascribed to the surface plasmon resonance of Ag nanoparticles and a large negative charge of PO43- ions. <![CDATA[Growth and Magnetic Properties of RF Sputtered Fe-Ga Thin Films]]> AbstractWe report the growth and characterization of Fe-Ga thin films. These films were RF sputtered onto Si, MgO and quartz substrates by controlling the parameters such as the deposition time, power and substrate temperature. The deposited films were characterized using X-Ray Diffraction, Atomic Force Microscopy and Vibration Sample Magnetometry measurements. The effect of substrates on the structure and magnetic properties were studied. XRD pattern of the deposited films showed the formation of DO3 phase with L12 ordered structure at higher sputtering power. The room temperature deposited films demonstrated higher magnetization (0.08 emu/g) as compared to higher substrate temperature (300 °C) deposited films. The Mr/Ms ratio was found to be 0.037 for films deposited at room temperature and 0.009 for the substrate temperature 300 °C. L12 order was observed in films deposited on MgO and Quartz substrates. Magnetization was also found to be high (Ms out of plane = 518 emu/cm3, Ms in plane = 707 emu/cm3) for films deposited on MgO substrate. <![CDATA[Synthesis of SnSb<sub>2</sub>Te<sub>4</sub> Microplatelets by High-energy Ball Milling]]> AbstractIn this work we demonstrate that high-energy ball milling process can be used to synthesize SnSb2Te4 without surfactant and further annealing. Milling parameters such as ball to raw material ratio (5:1) and milling time (2h) were determined to be suitable for synthesizing microplatelets of SnSb2Te4. The powders after milling for various durations were characterized by X-ray powder diffraction, scanning electron microscopy and electrical resistance measurements. <![CDATA[Melting Temperature and Wetting Angle of AlN/Dy<sub>2</sub>O<sub>3</sub> and AlN/Yb<sub>2</sub>O<sub>3</sub> Mixtures on SiC Substrates]]> AbstractThis work aims to evaluate the melting temperature and wetting behavior of AlN/Re2O3 (Re = Dy, Yb) mixtures when in contact with SiC substrates at high temperatures, in order to define whether these compounds can be further used to induce a more effective liquid phase sintering of SiC-based products. The prepared samples were placed on SiC plates and thermally treated up to 1900 °C under argon. The melting point and spreading evolution of different compositions of AlN/Re2O3 on SiC were determined by analyzing images captured as a function of the heating temperature. The contact angle and melting point were measured using the ImageJ software and according to DIN 51730, respectively. Based on the obtained wetting curves, all evaluated conditions resulted in the decrease of the contact angle values with temperature. The mixtures presenting improved wetting (θ ~ 1° and 3°) on SiC plates were the ones above the selected eutectic point. <![CDATA[Influence of Temperature and Acid Etching Time on the Superficial Characteristics of Ti]]> AbstractWe evaluated the influence of the etching time and temperature of an acid solution (HCl/H2SO4) on the chemical and topographical superficial characteristics of cpTi grade IV. Samples were analyzed by electron microscopy, interferometry, and grazing incidence XRD. The surfaces kept the irregularity aspect when submitted to the same etching temperature. On the other hand, the irregularities increased in size and depth with increasing etching time. The etching treatments that produced higher values for roughness parameters showed a combination of high temperature for a longer etching time. Some treatments produced very large irregularities, with a brittle surface in some regions. According to statistical correlation, the temperature made the strongest contribution in the variance of the mean values of the surface roughness parameters when compared to the etching time. Titanium and oxygen were the only elements on the surface in all groups. All test group samples showed the presence of titanium hydride. <![CDATA[On the Reduction of Stress Concentration Factor Around a Notch Using a Functionally Graded Layer]]> AbstractThe aim of this paper is to study the effect of functionally graded material (FGM) layer around a notch in a plate in three dimensions. Using exponential law of variation of Young's modulus and a coefficient of Poisson constant, the stress concentration factor (SCF) depends on the gradation direction of the constituent materials. The finite element method is used to study the performance of FGM layer around a notch in a ceramic plate under in tensile load. A parametric study is performed for several geometric and mechanical parameters such that width of the FGM layer and the ratio of FGM layer components. The effect of notch radius is also studied. <![CDATA[Stibnite Nanoparticles as a New Stabilizer for Poly (Methyl Methacrylate) Exposed to Gamma Irradiation]]> AbstractPoly (methyl methacrylate), PMMA, may be used in manufacturing of devices, which are exposed to gamma irradiation. However, the polymer undergoes significant changes in its properties during process and the use of additives is a common form to stabilize the PMMA matrix. In this way, stibnite was synthesized by sonochemical method and the amorphous powder constituted of nanospheres was obtained and investigated as additive. Commercial PMMA containing stibnite nanoparticles (ST-NP) was investigated and the samples were irradiated with gamma radiation (60Co). Our results showed that the addition of ST-NP at 0.3 wt% into the PMMA decreased the number of main chain scissions caused by the irradiation process, resulting in radiolytic stabilization of the polymer matrix. Analyses of mechanical properties showed influence of the ST-NP in the physical behavior of PMMA. Our findings suggest that stibnite nanoparticles are an effective additive for PMMA used in application of radiation resistance. <![CDATA[Synthesis and Characterization of Poly(Acrylamide-<em>Co</em>-Acrylic Acid) Flocculant Obtained by Electron Beam Irradiation]]> AbstractThe goal of the paper was to prepare a class of flocculants by free-radical copolymerization of acrylamide with acrylic acid in aqueous solutions in the presence/absence of potassium persulphate as initiator. Reaction medium was submitted to electron beam treatment of 0.6 to 1.5 kGy in atmospheric conditions and at room temperature. Because of the complexity of reaction mechanisms involved in radio-induced polymerization, was necessary to establish the connection between absorbed dose and initiator concentration, both of them very important in free radical production. Unlike the conversion coefficient and residual monomer concentration, intrinsic viscosity and Huggin’s constant are sensitive to the initiator concentration variation for all used irradiation doses. The copolymerization was confirmed by FTIR measurements. The flocculation characteristics were evaluated in 0.2 wt % kaolin suspension at room temperature using different polymer dosages between 0 to 10 ppm. High flocculation efficiency was obtained using the polymer having high values of intrinsic viscosity, molecular weight and radius of gyration. <![CDATA[Production and Properties of a New Wood Laminated Veneer/High-Density Polyethylene Composite Board]]> AbstractThe paper aimed at evaluating the feasibility and the properties of a new product which combines wood veneer and high-density polyethylene (HDPE) from post-consuming plastic bags. Three HDPE amounts were evaluated: 150g/m2, 250 g/m2 e 350 g/m2. The boards were manufactured using a single-opening hot-press under such conditions: 140ºC, for 20 minutes and pressure of 1 N/mm2. It was found that the production of this kind of composite board is technically possible and relatively simple and they did not present any veneer delamination. The properties of the composite boards were quite similar or even higher to those found in LVL made using thermosetting resin. The higher the HDPE amount the higher the density of the composite board, which imparted significantly in mechanical properties. However, when the composite boards were evaluated under same density the effect of the HDPE amount affected only Janka hardness. <![CDATA[Investigation of the Structural, Optical and Electrical Properties of Copper Selenide Thin Films]]> AbstractCopper selenide (CuSe) thin films were prepared by chemical bath deposition (CBD) method. X-ray diffraction (XRD) analysis was used to study the structure and crystallite size of CuSe thin film. The grain size and the surface morphology were studied using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The optical properties were studied using the UV-Visible transmission spectrum. The dielectric properties of the synthesized CuSe thin films were studied at different frequencies and different temperatures. Further, electronic properties, such as valence electron plasma energy, average energy gap or Penn gap, Fermi energy and electronic polarizability of the CuSe thin films were determined. The AC electrical conductivity study revealed that the conduction depended both on the frequency and the temperature. The temperature dependent conductivity study confirmed the semiconducting nature of the films. Photoconductivity measurements were carried out in order to ascertain the positive photoconductivity of the CuSe Thin films. This paper covers what all has been stated above besides discussing the results of I-V characteristics. <![CDATA[Synthesis and Characterization of New Copolymer Based Cinnamyl Methacrylate Monomer: Determination of Monomer Reactivity Ratio and Statistical Sequence]]> AbstractRadical-initiated copolymerization of Cinnamyl methacrylate (CMA) and Ethyl methacrylate (EMA) monomers were carried out at lower conversions (&lt;10%) using 2,2’-azobisisobutyronitrile (AIBN) as initiator, in 1,4-dioxane at 60 °C and nitrogen atmosphere. Structure and composition of copolymers for wide range of monomer feed were determined by Fourier Transform Infrared (FTIR) and Ultra-violet (UV) spectroscopy analysis through recorded of analytical absorption bands for monomers units. Monomer reactivity for CMA (1)–EMA (2) pair were determined by the Finneman-Ross (F-R) and Kelen- Tudos (K-T) methods. They are r1= 0.135 and r2= 0.868 as determined by K-T method. Parameters Q1, e1 of CMA monomer were calculated according to Alfrey-Price model. A relatively high activity of EMA was observed as compared to CMA growing radical. This result can be explained by sterical hindrance caused by chemical structure of cinnamyl pendant group in chain growth reactions. <![CDATA[Polymeric Materials for Membrane Contactor Devices Applied to Water Treatment by Ozonation]]> AbstractIn water treatment process ozone is applied to disinfection and to remove organic pollutants. Membrane contactor devices are used as a physical barrier to separate two fluids without phase dispersion and it can be used to improve the ozonation efficiency. Polymeric materials are used in membrane contactors and they can react with ozone, suffering degradation and losing its mechanical properties. In this work, commercial polymeric membranes were selected to investigate their interaction with ozone in gaseous phase. It was evaluated changes in polymer structures and in membrane morphology by FTIR, DSC, TGA and SEM. It was observed preferential ozone attack to double carbon-carbon bonds in the main polymer chain for polyimide and polysulphone membranes. Polypropylene has single carbon-carbon bonds and its reaction with ozone was less intensive. For polydimethylsiloxane membranes the ozone attack seems to occur in the carbon-silicon bond, leading to loss of mechanical and thermal properties. <![CDATA[The Influence of a Translucent Fiberglass Post on the Polymerization of Dual Cure Resin Cement Analyzed by Electron Paramagnetic Resonance]]> AbstractElectron Paramagnetic Resonance (EPR) was used as an alternative method to study the conversion degree of dual cure resin cement and verify the influence of prefabricated translucent fiberglass post on the dual cure resin cement polymerization at different restoration points. The post cementation of White Post DC (FGM, Joinville, SC, Brasil) was simulated using the dual cured resin cement Allcem (FGM, Joinville, SC, Brasil) in three different protocols: cement irradiated for 40 s; no light irradiation and cement irradiated with sealed cementation line. 2mm samples were obtained from three post sections and EPR spectra were obtained 10 minutes and 24 hours after mixing the base paste and catalyst of the cement. Results shows that the light curing protocol influenced the concentration of free radicals up to 8mm of the restoration, and the capacity of light transmission of the post was significant for the first 8mm of restoration and is non-existent in the deepest points of a simulated root canal. The cure in the apical part of restoration is exclusively chemical. <![CDATA[Mechanical Properties Evaluation of the Carbon Fibre Reinforced Aluminium Sandwich Composites]]> AbstractSandwich laminates play an important role in industries and they are used in varieties of engineering applications. In the present investigation, carbon fiber reinforced aluminium sandwich laminates are fabricated and their properties such as tensile, flexural and impact are studied for their use in structural applications. All the tests are carried out as per ASTM standard. Scanning Electron Microscope (SEM) analysis is carried out to investigate the structure of the sandwich laminates. The microstructures clearly indicate the fractured surface. The tested specimen clearly indicates the fracture surface of the sandwich composites. <![CDATA[Effect of the Fuels Glycine, Urea and Citric Acid on Synthesis of the Ceramic Pigment ZnCr<sub>2</sub>O<sub>4</sub> by Solution Combustion]]> AbstractIn this study, ceramic nanopigment ZnCr2O4was prepared by solution combustion using glycine, urea and citric acid as fuels. The objective is to study the influence of fuel on the morphology and the diffuse reflectance spectrum. The nanoparticles were characterized by field emission scanning electron microscopy (FESEM), the phase was investigated by X-ray diffraction (XRD), the thermal behavior was studied by thermogravimetry analysis (TGA) and differential scanning microscopy (DSC), the color was determined by diffuse reflectance spectroscopy and CIE L*a*b* colorimetric analysis. The average crystallite sizes obtained were 18.40 nm, 42.05 nm, and 18.69 nm when are used glycine, urea, and citric acid, respectively. Finally, the effect of fuel in the diffuse reflectance showed that the scattering of the light by the particles depend of the morphology. Also, the nanopigment was obtained by solution combustion at lower temperature than solid state reaction and it could be used in digital decoration. <![CDATA[Fabrication of Cathode Materials Based on Limn<sub>2</sub>o<sub>4</sub>/Cnt and Lini<sub>0.5</sub>mn<sub>1.5</sub>o<sub>4</sub>/Cnt Nanocomposites for Lithium – Ion Batteries Application]]> AbstractCarbon nanotubes (CNTs) are a promising candidate material for use in lithium batteries due to 1D tubular structure, high electrical, thermal conductivities, and extremely large surface area. In this work, the MWCNTs were purified by dispersion in a mixture of HNO3 and H2SO4acids. The oxidized-MWCNTs were used as conducting addition to prepare a nanocomposites as high performance cathode material for Li-ion batteries (LIBs). The spinel cathode materials of LiMn2O4 (LMO), doped spinel LiNi0.5Mn1.5O4 (LNMO) were synthesized and characterized via X-rays diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical properties of nanocomposites based on LMO/CNTs and LMNO/CNTs were investigated by cyclic voltammetry (CV) as well as electrochemical impedance spectroscopy (EIS). The EIS measurement indicated that the LMO (LNMO)/CNTs nanocomposites showed lower charge transfer resistance (Rct) than that of LMO(LNMO)/ Vulcan carbon materials. In addition, the studied nanocomposites cathodes gave a specific capacity of 145–1 and 120–1 for LMO/CNTs (10 wt%) and LNMO/CNTs (10 wt%), respectively, measured at a charge/discharge rate of 0.1C. <![CDATA[Oxide Formation on NiTi Surface: Influence of the Heat Treatment Time to Achieve the Shape Memory]]> AbstractSeveral studies regarding superficial treatments of Nitinol (NiTi) shape-memory have been developed aiming to the improve corrosion resistance and to block the Ni release to adjacent tissues. The necessary heat treatment to achieve the shape memory effect normally occurs at temperatures between 500 and 600 °C. However, titanium oxide (TiO2) is formed on the NiTi surface during the shape memory process heat treatment. In this work the effects of the heat treatment time on the surface characteristics of the formed NiTi oxide, at temperatures that promote the shape-memory (530 and 570 °C), were evaluated. The TiO2 layers which were obtained were evaluated by X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscope (SEM), thermogravimetric analysis (TGA), wettability and roughness. The results show that by increasing the exposure time at the temperature of 570 °C the formation of a thicker oxide is promoted, with less superficial roughness and of a hydrophobic nature. According to the literature, these characteristics indicate that the obtained oxide layer has properties that accelerat the osseointegration process. <![CDATA[Production of Copper and Cobalt Aluminate Spinels and Their Application As Supports for Inulinase Immobilization]]> AbstractCopper and cobalt aluminates were obtained through the use of chitosan as template. In this synthesis route, chitosan is eliminated by heating, and a porous material is produced. These oxides were used as supports for inulinase immobilization by adsorption process. Physical properties of produced particles were analyzed by X-ray diffraction (XRD) and nitrogen adsorption-desorption isotherms. Both oxides presented particles containing mesoporous characteristics and high surface area, which is desirable for applications in enzyme immobilization processes. The results revealed that the copper and cobalt aluminates exhibit high inulinase immobilization efficiencies, which makes them promising supports for enzyme immobilization. <![CDATA[Influence of Milling Time During the Mechanical Alloying Process on the Properties of Fe-3Si-0.75P Alloy]]> AbstractIn this study the soft magnetic alloy Fe-3Si-0.75P (wt%) was obtained by mechanical alloying through powder metallurgy. The processing included the formulation of metallic powder, wet milling for 1 h, 3 h, 6h and 9 h, in an attritor mill using alcohol P.A. as a lubricant. Cold compaction was then performed in a floating die under 600 MPa pressure and, finally the ring-shaped test specimens were sintered at 1150 °C for 1h. The electrical, physical and magnetic properties were then analyzed using the following assays: Laser granulometry, density, metallography, hysteresis curve and AC permeability, resistivity and XRD. The results showed a strong influence of milling time on magnetic properties of the alloy. There was a decrease in grain size with the milling time, which is likely the cause of increased in magnetic properties. <![CDATA[Microporous Nano-hydroxyapatite/collagen/phosphatidylserine Scaffolds Embedding Collagen Microparticles for Controlled Drug Delivery in Bone Tissue Engineering]]> AbstractScaffolds featuring spatiotemporal control of drug release is highly desirable for bone tissue regeneration. The objective of this study was to construct a scaffold with gradient porosity and drug distribution and evaluate the effect of scaffold structure on drug release kinetics and cell bioactivity. Nano-hydroxyapatite/collagen/phosphatidylserine scaffolds embedded with steroidal saponin loaded collagen microparticles were prepared using a porogen leaching protocol. Morphological characterization showed that the scaffolds consisted of dense layer and loose layer, and pores were interconnective. The microparticles were entrapped at the center of the scaffolds follow a gradient distribution. Release kinetics correlated with the structure. The loose layer showed greater drug release amount as compared to the dense layer. Such differences in release kinetics have distinct effects on cell bioactivity. Cell proliferated much more in loose layer than that in the dense layer. Such spatial and temporal control over drug deposition and delivery within the scaffolds could provide opportunities for tissue regeneration associated with optimum drug doses at wound site, and lessen undesirable drug release and side-effects at uninjured site. <![CDATA[Analysis of Stress and Fracture Strength of Zirconia Implants after Cyclic Loading]]> AbstractThe aim of this study was to manufacture a new zirconia implant (Y-TZP) and to evaluate the fracture strength and stresses generated after cyclic loading compared to titanium implants. Thirty-three zirconia and titanium implants were fabricated. The stress generated around the implants was observed by photoelastic analysis. The implants were then separated into groups (n = 10): Control (no treatment), mechanical fatigue and thermomechanical fatigue. All groups were submitted to a single cantilever flexure test to measure the material fracture strength. The results (2-way ANOVA, Bonferroni test, p &lt;.05) showed no statistically significant difference in the stresses generated between the zirconia and titanium implants. Titanium implants showed higher fracture strength than the zirconia implants, a property that was not altered by fatigue applied. It was concluded that stress distribution was similar for Zr and Ti and mechanical and thermomechanical fatigue had no influence on the fracture strength of the implants tested. <![CDATA[Electroless Plating of Ni-P-W Coatings Containing Scattered Nb<sub>2</sub>O<sub>5</sub> on Sintered NdFeB Substrate]]> AbstractThe ternary Ni-P-W coatings containing scattered Nb2O5particles were deposited on the sintered NdFeB substrates by electroless plating. The effect of experimental processing parameters on the deposition rate was investigated during electroless plating. The coatings performance, such as corrosion resistance, interfacial adhesion strength and micro-hardness, was evaluated by experimental testing. The experimental results indicated that the corrosion resistance of Ni-P-W/Nb2O5 composite and the interfacial adhesion strength between Ni-P-W/Nb2O5coatings and NdFeB substrate have been increased with increasing the Nb2O5 concentration up to 15gL-1. Increasing Nb2O5 concentration over 15gL-1decreases the corrosion resistance of Ni-P-W/Nb2O5composite and the interfacial adhesion strength. Testing of micro-hardness showed that the hardness of Ni-P-W coatings containing scattered Nb2O5 composite increases with increase in Nb2O5 concentration. <![CDATA[Fresh-state Properties of Self-compacting Mortar and Concrete with Combined Use of Limestone Filler and Fly Ash]]> AbstractThis paper presents the results of a study on the behaviour of self-compacting concrete (SCC) in the fresh and hardened states, produced with binary and ternary mixes of fly ash (FA) and limestone filler (LF), using the method proposed by Nepomuceno. His method determines the SCC composition parameters in the mortar phase (self-compacting mortar - SCM) easily and efficiently, whilst guaranteeing the SCC properties in both the fresh and hardened states.For this, 11 SCMs were studied: one with cement (C) only; three with FA at 30%, 60% and 70% C substitution; three with LF at 30%, 60% and 70% C substitution; four with FA + LF in combinations of 10-20%, 20-10%, 20-40% and 40-20% C substitution. Once the composition of these mortars was defined, 18 SCC mixes were produced: 14 binary SCC mixes were produced with the seven binary mortar mixes, and four ternary SCC mixes were produced with the four ternary mortar mixes. In addition to the methodology proposed by Nepomuceno, the combined use of FA and LF in ternary mixtures was tested. The results confirmed that the method could yield SCC with adequate properties in both the fresh and hardened states. It was also possible to determine the SCC composition parameters in the mortar phase (self-compacting mortar - SCM) that will guarantee the SCC properties in both the fresh and hardened states, as confirmed through the optimized behaviour of the SCC in the fresh state and the promising results in the hardened state (compressive strength). The potential demonstrated by the joint use of LF and FA through the synergetic interaction of both additions is emphasized. <![CDATA[Oxygen Permeability Coefficient of High Density Polyethylene/Cu Nanofibers Nanocomposites below Percolation]]> AbstractThe main objective of this study was to relate the elastic modulus of a polymer nanocomposite to its permeability coefficient. The materials studied included high density polyethylene (HDPE) filled with copper nanofibers (Cu-nanofibers). Both of the experimental values of the elastic modulus and the gas permeability coefficient of the HDPE/Cu-nanofibers films were obtained from Grigoriadou et al. and Bikiaris &amp; Triantafyllidis studies. In this study, the Halpin-Tsai model was modified and then used to fit the elastic modulus experimental data. It was found that the modified shape factor (ω′) of the Cu fibers as a function of the composite volume fraction is125exp(−41∅). Then, the model was used to predict the oxygen permeability coefficient of the HDPE/Cu-nanofibers films below the percolation point. It was found that the tensile modulus of the nanocomposites increased by 24% whereas the permeability to oxygen coefficients decreased by 65% compared to pristine HDPE. Also, the results from the models match the experimental data. <![CDATA[Hydrothermal Synthesis of Three-dimensional Butterfly-like Ni Architectures as Microwave Absorbers]]> AbstractThree-dimensional butterfly-like Ni architectures were fabricated by a surfactant-assisted hydrothermal method. The Ni architectures, with lengths of about 20 μm and widths of 4-6 μm, were assembled from tens of Ni nanorods with the averaged diameter of about 200 nm. The Ni nanorods were coated by oxide shells. The saturation magnetization of the Ni architectures was found to be 66.2 emu/g. The magnetic loss in the Ni architectures was mainly caused by the natural resonance, while the dielectric relaxation loss was originated from the interfacial relaxation between the oxide shells and the Ni nanorods in addition to the size distribution and morphology of the Ni architectures. Absorbers with a thickness of 2.1 mm exhibited an optimal reflection loss (RL) value of -38.9 dB at 12.8 GHz. RL values exceeding -20 dB in the 8.0-17.8 GHz range were obtained by choosing absorber thicknesses between 1.5 and 3.2 mm. A quarter-wavelength cancellation model was used to explain the observed thickness dependence of RL peak frequency. <![CDATA[Synthesis, Characterization and Study of Effect of Irradiation on Electronic Properties of Polyaniline Composite with Metal Complex of Co (III)]]> AbstractThe present work reports the synthesis of PANI composite with hexamminecobalt(III) chloride metal complex as dopant via in situ oxidative polymerization by ammonium persulphate in non-aqueous DMSO medium. The dopant metal complex has been synthesized by known method and characterized by using FTIR, XRD and SEM analysis. The synthesized PANI/[Co(NH3)6] Cl3 composite was characterized by FTIR, XRD, UV-Vis and SEM techniques. FTIR of PANI composite showed its successful synthesis with the presence of some dopant peaks in its FTIR spectrum. XRD spectra of composite revealed its crystalline nature having almost same spectra as that of dopant metal complex with slight shift in the position of peaks. Electrical measurement of the composite was made using four probe conductivity meter and the thermal studies have been done by thermal gravimetric (TG) technique. The results showed improvement in the thermal stability of PANI composite together with increase in its conductance, thereby making it a possible future material for high temperature application purposes. Electronic properties of the composite were investigated using UV-Vis spectroscopy which revealed decrease in the energy band gap of the composite on irradiation. This is attributed to the distortion of polymer chains on exposure to radiations, which results in decrease in conjugation and hence increases in band gap energy.