bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical and Thermal Characterization of Road Bitumen Ageing
Authors: Sá da Costa M. , Farcas Fabienne , Santos L.F. , Eusébio M.I. , Diogo António Correia
Published: January 2010

Bitumen ageing stands for a number of physico-chemical modifications that occur in bitumen as a response to environmental conditions. Several tests have been proposed to simulate bitumen ageing. Two of the most common ones are: a) the Rolling Thin Film Oven Test (RTFOT), which simulates short term ageing; b) the Pressure Ageing Vessel (PAV) test, which accounts for long-term ageing and it is usually performed on the RTFOT residue. A study of the physico-chemical modifications of a 50/70 pavement grade bitumen caused by ageing is presented. Both RTFOT and PAV tests were used. A follow-up of bitumen modifications due to ageing was done by several methods. In particular: 1) Fourier transform infrared spectroscopy (FTIR), to follow bitumen oxidation by the increase of oxygenated functional groups, which were quantified by taking appropriate structural indices; 2) Iatroscan thin layer chromatography (TLC), to follow bitumen composition expressed by the generic SARA fractions (saturates, aromatics, resins and asphaltenes); 3) Gel permeation chromatography (GPC), under “ultra-fast” conditions, to follow the colloidal structure of bitumen; and 4) Differential scanning calorimetry (DSC), to evaluate the changes of the crystallized fractions (%FC) and the glass relaxation temperature (Tg). The results show that the PAV test causes more severe changes in bitumen than the RTFOT test. In particular, the evolution of the oxidation processes could be quantified by taking carbonyl and sulfoxide structural indices. Ageing also modified the SARA profile, namely, the relative contribution of aromatics, resins and asphaltenes fractions. On the other hand, DSC data remained almost unaffected after ageing tests, which may be indicative of the survival of most of the phases of the bitumen after these tests. Finally, a comparative analysis of the sensitivity and performance of all these methods is presented.
Biomimetic and Smart Polymeric Surfaces for Biomedical and Biotechnological Applications
Authors: Mano João F.
Published: January 2010

Surfaces and biointerfaces are recurrent when materials are used in bio-related applications. Bio-inspired concepts have been implemented in this field and gained increasing interest. In this context, stimuli-responsive surfaces have found applicability in a variety of subjects, including switchable surfaces to control protein immobilization or cell adhesion, porous membranes for controlled drug delivery applications, substrates and scaffolds for tissue engineering applications, biosensors, or membranes for bioseparation. Moreover, self-assembly strategies and hierarchical structures often found in Nature could inspire scientist and engineers to propose new solutions in the design and fabrication of surfaces with special features, such as wettability within extreme ranges, improved adhesion, optical and mechanical properties and specific bioactivity. In this work some aspects related to the use of stimuli-responsive and biomimetic surfaces in the field of biomedicine and biotechnology are highlighted and some examples are presented.
Computational Study of the Influence of Polymer/Polymer Interface Formation on Bilayer-LED Functioning
Authors: Barbosa Hélder M.C. , Ramos Marta M. D. , Correia Helena M.G.
Published: January 2010

The actual interest on polymer light emitting diodes (PLEDs) is based on the fact that they are easy to process, which reduces the cost of fabrication and thus opening a new branch in the electronic market – the low-cost electronics. However, these devices present a limited efficiency compared to their inorganic counterparts mainly due to the unbalanced charge injection, which reduces the fluorescence emission. One of the first strategies to improve PLEDs efficiency was using a bilayer structure composed by two polymers to improve charge injection and transport, and at the same time tune charge recombination zone to reduce the effect of the electrodes on exciton quenching. Although this is a very ingenious device architecture some of these bilayer devices showed a lower efficiency than it was expected. The reason for that is attributed to the dissolution of the first polymer layer by the solvent used for the deposition of the second polymer layer, which do not allow to create a define polymer/polymer interface. Although cross-linking the first polymer layer can solve this problem, there is not a clear understanding why the presence of a graded interface between both polymer layers can lead to a change on PLED efficiency. In order to clarify the effect of a graded polymer/polymer interface as compared to a sharp one on the functioning of a PLED, we performed computer experiments using a mesoscopic model of a bilayer PLED developed by us that considers the morphology of both polymers at nanoscale and their properties at molecular scale. The results present in this work show clearly a significant change on the charge recombination profile within the polymer device depending on the type of interface formed between the two polymers, which can be a plausible explanation for the loss of efficiency in the bilayer 7-CN-PPV/PPV LED.
Synthesis and Optical Characterization of Pr3+ Doped UV Emitting Luminescent Ceramics
Authors: Plewa Julian , Juestel Thomas
Published: January 2010

UV emitting luminescent materials are of strong interest for UV emitting fluorescent lamps driven by a Hg low-pressure or a by Xe excimer discharge. Pr3+ doped host lattices exhibit efficient UV emission upon deep UV excitation, if the site of the host lattice, where Pr3+ is located, is suitable for this purpose. This work deals with Pr3+ activated VUV ceramic luminophores, i.e. materials, which show efficient luminescence upon 160 nm excitation. As host lattices for the potentially UV emitting Pr3+ ion aluminates and silicates have been studied. All samples were prepared by conventional mix and fire synthesis techniques with metal oxides as starting materials. Firstly, powder samples were annealed between 1000 and 1700 °C and secondly, ceramic samples were repeatedly thermally treated at similar temperatures after pressing. It is demonstrated that translucent ceramics show mainly UV luminescence upon deep UV excitation, while excitation by a blue 450 nm LED results in green to red luminescence with a similar decay time as observed for single crystals.
Properties of Co Substituted Bismuth Ferrite System by Rapid Liquid Phase Sintering
Authors: Zhu J.C. , Hu X. , Mao X.Y. , Wang W. , Chen Xiao Bing
Published: January 2010

The multiferroic ceramic samples of Co substituted Bi0.9Nd0.1Fe1-xCoxO3 ( x = 0.00, 0.03, 0.05, 0.07, 0.09, 0.10, 0.20 and 0.30) were prepared by a rapid liquid phase sintering technique. As Co content increases, the Bi0.9Nd0.1Fe1-xCoxO3 samples have a structural transformation from rhombohedral (space group R3c) to cubic structure (space group I23). A small amount of Co substitution maintains the ferroelectric properties while high doping content deteriorates the ferroelectric behavior due to the attendant high leakage current caused by the valence fluctuation of Co ions. It is found that the remnant magnetization (Mr) is enhanced greatly from a value of 4.87  10-6 emu/g at x = 0.00 to 0.054 emu/g at x = 0.30.
Highly Luminescent CdTe Nanocrystals Synthesized in Aqueous Solution and Self-Assembled on Polyelectrolyte Multilayers
Authors: Gutiérrez-Lazos C.D. , Ortega-López M. , Rosendo-Andrés E. , Matsumoto-Kuwabara Y. , Sánchez-Reséndiz V. , Morales-Corona J. , Olayo-González R. , Barrera-Calva E. , Díaz-Becerril T.
Published: January 2010

CdTe nanocrystals have been synthesized in aqueous solution at 92oC under open-air conditions. During the reaction, aliquots of the samples were taken at different growth times and used to obtain their UV-Vis absorbance and photoluminescence spectra in order to estimate the nanocrystal size. The absorption peaks are located around 459 nm for 1 h, 478 nm for 2 h, 491 nm for 4 h, 532 nm for 7 h and 610 nm for 94 h of growth time. The mean nanocrystal size for these samples is 2 nm, 2.2 nm, 2.3 nm, 2.6 nm and 3.4 nm, respectively, according to the theoretical calculations of 1s1/2 – 1s3/2 excitonic transition. Finally, CdTe nanocrystals were assembled using layer-by-layer technique on glass substrates, using PDDA as cationic polyelectrolyte and negatively charged CdTe nanocrystals. The Raman spectroscopy shows that CdTe nanocrystals preserve the nanoparticle properties after being assembled.
Synthesis and Characterization of New Push-Pull Anthraquinones Bearing an Arylthienyl-Imidazo Conjugation Pathway as Efficient Nonlinear Optical Chromophores
Authors: Batista Rosa M.F. , Costa Susana P.G. , Belsley Michael , Raposo M. Manuela M.
Published: January 2010

Compounds 1 were synthesized, in good to excellent yields (72-87%), through condensation of formyl-arylthiophene precursors 2 with 1,2-diaminoanthraquinone in ethanol at reflux, followed by cyclisation of the imine intermediate with Pb(OAc)4 in acetic acid at room temperature. Evaluation of the thermal, linear and NLO properties of these compounds was carried out. The  values of chromophores 1, measured by hyper-Rayleigh scattering (HRS) technique, are several times larger (49-67) than that of the standard reference molecule p-nitroaniline (pNA). Due to their excellent thermal stability, (Td = 341-446 oC), and good NLO properties, arylthienyl-imidazo-anthraquinones 1 could be used as new efficient and thermally stable NLO materials.
Structural and Magnetic Properties of Sm(CobalFe0.1Ni0.12Zr0.04B0.04)7.5 Melt Spun Ribbons
Authors: Makridis Sofoklis S.
Published: January 2010

We have investigated the structural and magnetic properties of Sm(Co0.70Fe0.1Ni0.12Zr0.04B0.04)7.5 melt spun ribbons. The arc-melted bulk samples have been used to obtain ribbons at 37 up to 55 m/sec while annealing has been performed in argon atmosphere for 30-75 min at 600-870 oC. In as-spun ribbons the hexagonal SmCo7 (TbCu7-type of structure) of crystal structure has been determined from x-ray diffraction patterns, while fcc-Co has been identified as a secondary phase. After annealing, the 1:7 phase of the as-spun ribbons transforms into 2:17 and 1:5 phases. TEM analysis shows a homogeneous nanocrystalline microstructure with average grain size of 30-80 nm. Coercivity values of 15-27 kOe are obtained from hysteresis loops traced at non-saturating fields. The coercivity decreases as temperature increases, but it is high enough to maintain values higher than 5 kOe at 380 oC. The maximum energy product at room temperature increases, as high as 7.2 MGOe, for melt-spun ribbons produced at higher wheel speed.
Improvement of the Mechanical Properties of Glasses Based on the 3CaO.P2O5-SiO2-MgO System after Heat-Treatment
Authors: Daguano J.K.M.F. , dos Santos Claudinei , Suzuki Paulo Atsushi , Bicalho Luiz A. , Fernandes Maria Helena F.V.
Published: January 2010

Glasses based on the 3CaO.P2O5-SiO2-MgO system present high bioactivity aiming the use as bone restorations. On the other hand, the low mechanical properties reduce the importance of this glass aiming the use as restoration bulk specimens. In this work, glass-ceramics were obtained by devitrification of this glass using different temperatures. CaCO3, SiO2, MgO and Ca(H2PO4).H2O were used as starting-powders. Powder mixture was milled/homogenized and melted at 1600°C, for 2h and annealed at 700°C for 4h with cooling rate of 3°C/min. Glass specimens of 151550mm3 were characterized by DTA and XRD analysis. Specimens were heat-treated in different temperatures between 7000C and 1050°C, for 4 hours, obtaining glass-ceramics with different crystallized phase content. Hardness and fracture toughness were determined and correlated with crystalline phase content. The results indicated that crystallization-degree increase with the temperature, and the mechanical properties are improved: Hardness values present increases lower than 20% as function of the crystallization. Fracture toughness may increase 100% as function of temperature (crystallization degree).
Synthesis of ZnO Particles by Electrolysis
Authors: García-Salgado G. , López R. , Nieto-Caballero F.G. , Díaz-Becerril T. , Juárez H. , Rosendo-Andrés E. , Coyopol A.
Published: January 2010

ZnO with a good crystallinity and visible photoluminescence at room temperature around 518 nm and 605 nm obtained by an electrolytic method using urea and zinc nitrate is presented. An electrolytic Teflon cell was used for the process using tungsten wire and aluminum foil as electrodes, the tungsten wire was introduced in a solution of water, zinc nitrate and urea. The electrical potential was modified, keeping constant the growth time. As substrate and cathode a 1-3 -cm, (100), n type, silicon wafer was used. The crystalline structure and photoluminescence showed interesting changes when the electrical potential was modified. XRD (X Ray Diffraction) performed on the films showed characteristic diffraction peaks of ZnO obtained in other works. The amplitude of these peaks changed with the electrical potential applied, with a predominance of the (100), (002) and (101) planes. The photoluminescence (PL) bands changed with the electrical conditions too. At low electrical currents a predominance of the green band (520 nm) was observed, and another band around 600 nm appeared from high current conditions, this behavior can be associated with different defects generated during the grow process. From these results we conclude that the change in the electrical current produces changes in the structural and optical characteristics of the material.
PL Properties of SiOx Obtained by HFCVD Technique
Authors: Díaz-Becerril T. , García-Salgado G. , Coyopol A. , Rosendo-Andrés E. , Juárez H.
Published: January 2010

In this work, SiOx films were deposited on crystalline silicon substrates and their microstructure and photoluminescent properties are reported. The films were deposited by the Hot Filament Chemical Vapor Deposition (HFCVD) technique using molecular hydrogen (H2) and silica glass (SiO2) as reactants. The H2 becomes atomic hydrogen when is flowed through a tungsten wire heated at 2000 °C. According to the chemical reaction, the atomic hydrogen reacts with the solid source (SiO2) and a SiOx film on a substrate is obtained. From FTIR and room temperature photoluminescence measurements can be concluded that, regions with different average size of silicon nano-clusters in the oxide are formed and they probably are the responsible for the light emission in the visible range.
SEM Characterization of Al3Ni Intermetallics and its Influence on Mechanical Properties of Directionally Solidified Hypoeutectic Al-Ni Alloys
Authors: Spinelli J.E. , Canté M.V. , Cheung Noé , Mangelinck-Noël Nathalie , Garcia Amauri
Published: January 2010

Rod-like Al3Ni intermetallic structures have been widely studied by Bridgman techniques of solidification. However, there is a lack of experiments conducted under unsteady-state solidification conditions. Such conditions are very close to the industrial reality since the thermal solidification variables (tip cooling rate, tip growth rate and thermal gradient) are freely changing as solidification progresses. In this research, Al3Ni structures found in hypoeutectic Al-Ni alloys were characterized under transient solidification conditions. Two Al-Ni alloys (1.0 and 5.0 wt%Ni) were directionally solidified. SEM (Scanning Electron Microscope) micrographs were obtained along the casting length (P). It was possible to observe with adequate magnifications the distribution of rod-like Al3Ni particles along the interdendritic regions. In order to emphasize the examination of morphology and distribution of such particles, the aluminum-rich matrix was dissolved by immersion of the sample in a fluoride acid solution (0.5%HF + 99.5% H2O). The effects of nickel content, dendritic arrangement and Al3Ni distribution on mechanical properties were investigated by tensile tests.
Mechanical Behaviour of ZrO2-Bioglass Dental Ceramics under Cyclic Fatigue Loading
Authors: Bicalho Luiz A. , dos Santos Claudinei , Souza R.C. , Barboza M.R.J. , Reis Pereira Baptista Carlos Antonio
Published: January 2010

The cyclic fatigue life of 3mol%Y2O3-stabilized ZrO2 (3Y-TZP) ceramics doped with bioactive glass has been investigated. Samples of 3Y-TZP containing 3 or 5wt% of bioglass were sintered at 1300oC for 120 minutes. Sintered samples were characterized by relative density, XRD and SEM analysis. Mechanical properties of hardness and fracture toughness were determined using Vickers indentation method and Modulus of Rupture was determined by four-point bending testing. Furthermore, the reliability of the samples was estimated using Weibull statistic analysis. The cyclic fatigue life was estimated using four-point bending testing under frequency of 25Hz and stress ratio, R, of 0.1. Highly dense tetragonal ZrO2 samples were obtained after sintering and presented hardness of 10.5 and 11GPa, KIC of 6 and 7MPam1/2, bending strength of 320 and 450MPa and Weibull’ modulus of 6 and 7 for samples containing 5 or 3% of bioglass respectively. The fatigue behavior indicates that the increasing of stress level leads to decreasing of the number of cycles and the number of run-out specimens. Fatigue behavior was similar for the two compositions tested. Samples containing 3% of bioglass are more resistant (near 10%) to fatigue presenting cyclic fatigue life near to 250MPa while samples with 5% presented fatigue limit near to 220MPa.
Intermetallic Phase Precipitation in Duplex Stainless Steels during High Temperature Exposition
Authors: Escriba D.M. , Materna-Morris Edeltraud , Plaut Ronald Lesley , Padilha Angelo Fernando
Published: January 2010

The intermetallic phase precipitation, mainly sigma () and chi () phases, was studied in a comparative manner in two stainless duplex steels: a duplex type UNS S31803 and a superduplex type UNS S32520. The -phase precipitated at ferrite/ferrite grain boundaries prior to the -phase precipitation, which occurred preferentially at ferrite/austenite interfaces and at ferrite/ferrite grain boundaries. The -phase precipitation is a eutectoid type reaction of ferrite, leading to -phase and austenite (γ). The -phase precipitated at lower temperatures and in smaller amounts than sigma. The -phase is metastable in the studied steels and was consumed during the -phase precipitation.
Redesign of Exhaust Systems for Naval Gas Turbines: Usage of a New Cr-Mn Austenitic Stainless Steel
Authors: Cruz H.J.T. , Martins Rui F. , Veigas J.C.G. , Aveiro J.L.G.
Published: January 2010

Studies performed earlier show that the thermal shock loading has influence, together with the normal service loadings, in the fatigue life of some critical welded joints present in the exhaust systems of naval gas turbines [1-2]. In order to prevent the fatigue crack propagation that was verified in service [3], a recently developed ultrahigh-strength austenitic stainless steel was selected (Cr-Mn steel - number 1.4376) and its mechanical properties and the fatigue resistance are under study. This new material could replace, locally, the current material used in the main structure of the exhaust system (AISI 316L). Experimental data are shown. The temperature measured at the critical locations was about 350°C and the pressure applied in the system was calculated through a Computational Fluid Dynamics simulation (CFD), whose results are presented in the paper. The stresses induced by the loadings will be important to estimate the lifetime from the fatigue resistance tests (S-N curves) that will be performed, at 350°C, in butt and T-welded joints of AISI 316L stainless steel with Cr-Mn austenitic stainless steel.
Ordered Mesoporous Silica Materials for Protein Adsorption
Authors: Sezões F. , Ribeiro Carrott Manuela M.L. , Mourão Paulo A.M. , Russo P.A. , Carrott Peter J.M.
Published: January 2010

Lysozyme and BSA were used, as model proteins of considerably different dimensions, in order to evaluate the influence of the distinct pore structural characteristics of three types of ordered mesoporous silica materials (MCF, SBA-15 and MCM-41) on protein adsorption. Characterisation by X ray diffraction and nitrogen adsorption at 77K revealed the typical pore structural features of each type of material. The maximum of the pore size distributions indicated that the width of the windows of MCF (2) (mesitylene/P123 of 2) was larger than the pore diameter of the unidirectional tubular pores of SBA-15. All the materials presented similar small external surface areas but high pore volumes, with that of MCF (2) being the highest. The adsorption of lysozyme at pH=8 increased in the order MCM-41<< SBA-15< MCF (2), and the uptakes were well above those of BSA at pH=5. Although BSA is not completely excluded from the mesopores of SBA-15 and MCF (2), as happens with MCM-41, the adsorption occurs to a very limited extent. The overall behaviour of these SBA-15 and MCF (2) samples was not significantly different and both revealed potential for the separation of these proteins.
A Study on CuO-Al2O3 Infiltration by Aluminium
Authors: Guedes Mafalda , Ferreira José Maria F. , Ferro Alberto C.
Published: January 2010

This paper reports preliminary studies regarding a new fabrication process for aluminium alloy matrix particulate reinforced composites, which uses ceramic preforms with alumina and tailored amounts of reactive copper oxide, CuO. An Al2O3-CuO mixture with 75 mol% CuO was selected, aiming at a 10-40vol% reinforcement phase fraction in the final composite, after aluminium infiltration. Molten aluminium infiltration progress was studied as a function of ceramic’s composition, doping, and infiltration time. The resulting microstructures were investigated by OM, SEM, FESEM and EDS in order to establish the liquid aluminium infiltration profile at the metal/ceramic interface. Infiltration experiments showed that the 3CuO (s) + 2Al (l) → 3Cu (l) + Al2O3 (s) redox reaction is triggered at the experimental conditions used, but the infiltration process is slow and does not go to completion. The use of NaOH as a doping agent promotes effective infiltration of molten aluminium upon the ceramic green mixture.
Oxide Inclusions in Steel Welds of Car Body
Authors: Wegrzyn T. , Miroslawski J. , Silva Abílio P. , Pinto D.G. , Miros M.
Published: January 2010

The goal of this research is to choose the proper method of car body welding. Properties of weld metal deposits depend on many conditions. First of all, this paper attempts to study the role of oxide inclusion sites on the transformation of austenite to acicular ferrite in steel weld metal deposits and their toughness. Safety and exploitation conditions of welded steel structure depend on many factors. The most significant of those factors are connected with materials, welding technology, state of stress and temperature. Because of that a good selection of steel and welding method is crucial to obtain proper steel structure. Car body elements of higher durability are made of low carbon and low alloy steel, very often with small amount of carbon and the amount of alloy elements such as Ni, Mn, Mo, Cr and V in low alloy steel and their welds. In the terms of the kind of steel it is used a proper welding method and adequate filler materials. In the present paper the influence of Mn, Ni, Mo, in WMD on the behaviour of steel structure for low temperature service was tested.
Welding with High Power Fiber Laser API5L-X100 Pipeline Steel
Authors: Miranda R.M. , Quintino L. , Williams S. , Yapp D.
Published: January 2010

The increasing length of oil and gas transportation pipelines, associated with their construction and operating costs, has lead to the development of new steel grades with higher performance. The API 5L- X100 is a new high strength steel for pipeline applications which enables the use of thinner walled pipes, lighter to transport and easier to handle on site, allowing greater operating pressures and reducing overall costs. However, this steel grade has limited ductility. Since advantages largely surpass disadvantages, these materials are being seen adequate for earthquake risk areas and low temperature environment as in the Arctic region. X100 grade is already used in northern Canada and is planed for Japan Sub Sea. Automatic metal arc welding on site is the most common method of welding onshore pipelines in steel grades X65, X70 and X80. The use of high strength steels requires the development of new welding procedures with narrow specifications and the X100 steel has limited weldability. Research is needed to develop appropriate welding procedures, avoiding typical metallurgical problems like cold cracking and toughness reduction in the weld area and to achieve high productivity and economical feasibility. This paper presents results on API X100 steel grade welded by high power fiber lasers. Since these lasers are quite new in the market, an analysis of the laser source, as well as the beam/material interaction is made. The welds produced were investigated for both macro- and microstructural analysis and mechanical properties, contributing to a better understanding of the transformations induced in this material by the thermal cycle associated with laser welding.
Secondary Carbide Precipitation in Low Silicon Hot Work Tool Steels
Authors: Mesquita Rafael Agnelli , Barbosa Celso Antonio , Morales E. Valencia , Kestenbach H.J.
Published: January 2010

A reduction from 1.0 to 0.3%Si has recently been shown to improve mechanical properties of H11-type hot work tool steels. The present paper shows that an important improvement in toughness can be explained by the effect of Si content on the precipitation sequence of secondary carbides during tempering after quenching. Carbide particle distributions were observed and identified by electron microscopy, allowing to relate the effect of Si on mechanical properties directly to its effect on cementite and subsequent alloy carbide formation during high temperature tempering.
Tailoring of the Magnetic Properties of Co, Fe and Ni Nanocrystallites
Authors: Leonowicz Marcin , Szmidt E. , Pomogailo Anatolii D. , Dzhardimalieva Gulzhian I.
Published: January 2010

Ferromagnetic or superparamagnetic nanocrystallites, stabilized in carbon matrix, were prepared by the procedure comprising formation of the appropriate metal acrylamide complex, followed by frontal polymerization and pyrolysis of the polymer. The pyrolysis products were in a form of beads, which contained in their volume randomly distributed nanocrystallites. The nanocrystallites had various composition, magnetic properties and sizes ranging from few to tens of nanometers, depending on the element type. Application of this procedure stabilizes the nanostructure and enables processing of nanoparticles within a narrow window of sizes. The magnetic parameters depend on the crystallite size, determined by their chemical composition. The nanocrystallites pyrolysed at 773 K exhibited ferromagnetic properties for Co and Fe, and superparamagnetic behaviour for the Ni. The nanocrystallites can potentially be applied as sensors for tagging the biological substances or for targeted drug delivery.
Effect of Surface Modification of Multiwall Carbon Nanotubes on their Electrical and Surface Properties
Authors: Omastová M. , Mičušík M. , Fedorko Pavol , Chehimi M.M. , Pionteck J.
Published: January 2010

The surface of multiwall carbon nanotubes (CNT) was modified by non-covalent approach. Various types of surfactants, an anionic surfactant - dodecylbenzenesulfonic acid, an cationic surfactant - cetyltrimethylammonium bromide and their combination with different molar ratios were used for modification. Different power of ultrasound, 64 or 400 W was used to evaluate its influence on the properties of prepared composites. The electrical conductivities of unmodified CNT, particles treated by ultrasound, and CNT modified with surfactants were measured. The surface properties of modified particles were determined by X-ray photoelectron spectroscopy and scanning electron microscopy. Thermogravimetric analysis was used to confirm the presence and to evaluate the quantity of surfactants in the modified CNT.
Preparation of YAG Nanoparticles and their Characteristics
Authors: Grabis J. , Jankoviča D. , Šteins Ints , Patmalnieks Aloizijs
Published: January 2010

The nanosized yttrium aluminium garnet powders doped with rare earth oxides are prepared by combustion synthesis using several organic fuel. Dense materials are manufactured by conventional sintering and spark plasma sintering (SPS). The combustion synthesis provides preparation of pure crystalline YAG nanopowders at ratio Y/Al = 3/5 after additional calcination at 1000 oC. The relative density of the SPS sintered samples at 1500 oC for 2 min is in the range of 95.4–98.5% depending on dispersity of powders.
Synthesis and Characterization of Nitrogen Doped Carbon Nanotubes
Authors: Kordatos K. , Ntziouni A. , Theodoratou A. , Perraki Maria , Terrones M. , Kasselouri-Rigopoulou V.
Published: January 2010

The present work describes the synthesis of nitrogen doped multi-walled carbon nanotubes (CNx CNT). The chosen production method was the catalytic pyrolysis of a solid mixture containing [Ni(DMG)2] and melamine (C3H6N6), under an Αr atmosphere. A series of various experiments were performed, using different proportions of the reaction mixture, in order to optimize the production conditions of nitrogen doped carbon nanotubes. Finally, the produced materials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), Raman spectroscopy as well as thermogravimetric analysis (TGA). The obtained data from all the above analyses, showed the formation of nitrogen doped carbon nanotubes of various diameters as well as nanofibers surrounded by byproducts such as aggregations of amorphous carbon and metallic catalyst, depending on the proportion of the reaction mixture.
Vanadium(V) Oxide – Metal Organic Nanocomposites as Electrochemical Sensing Materials
Authors: Toma H.E. , Timm R.A. , Gonzalez M.F. , Araki K.
Published: January 2010

This work deals with a new class of vanadium pentoxide nanocomposites containing supramolecular iron or manganese tetrapyridyl porphyrins coordinated to four [Ru(bipy)2Cl]+ complexes. Their characterization was carried out by means of X-ray diffraction, SEM, AFM, confocal Raman microscopy, electronic spectroscopy and electrochemistry. According to X-ray diffraction, the original VXG lamellar framework was maintained in the nanocomposite material, but the interlamellar distance increased from 11.6 Å to 18.5 Å, reflecting the intercalation of the porphyrin species into the inorganic matrix. The films generated by direct deposition of the nanocomposite aqueous suspensions onto interdigitated gold electrodes exhibited good electrical and electrochemical performance for application in amperometric sensors.
Biodegradable Agar Extracted from Gracilaria Vermiculophylla: Film Properties and Application to Edible Coating
Authors: Sousa Ana M.M. , Sereno Alberto M. , Hilliou Loic , Gonçalves Maria P.
Published: January 2010

Gracilaria is a red algal genus that biosynthesizes a polymer called agar that is extensively used in the food and pharmaceutical industries as gelling and stabilizing agent. In the last years, many studies have focused on gel properties of this biopolymer; but the agar films and coatings still have few studies reported. The edible film and coating have a protective function, preventing moisture, oxygen and flavour transfers between food and surroundings. The objectives of this work are the production of biodegradable agar films from Gracilaria vermiculophylla, collected in Ria de Aveiro, Portugal, and the study of the effect of glycerol, an hydrophilic plasticizer, on the properties of the films and on subsequent application in edible coating of fresh fruits and vegetables. The agar extraction was carried out at specific optimum parameters determined in previous work (3.5 h pre-treatment duration, 6% NaOH concentration and 2 h extraction time). Agar films were made using the knife coating technique and compared with commercial agar. The physical properties of films such as hygroscopicity, mechanical resistance (Young’s modulus, tensile strength and elongation), and permeability to water vapour and oxygen were characterized. As expected, the plasticizer addition revealed and increase on elongation and decrease on tensile strength. The films were transparent and optically clear, showing good properties similar to the commercial agar films. The potential application of the agar/glycerol solution to fresh vegetable preservation was tested. Model fruits and vegetables were coated with the biopolymer/plasticizer solution and compared with a control sample in terms of colour, firmness, weight loss and shelf life. Considering on one hand the abundance of the raw algal material which is actually an invasive species, and the properties of the agar films and coatings obtained on the other hand, commercial use of G.vermiculophylla from Ria de Aveiro is well justified.
Semi Crystalline Behaviour of Cassava Starch Films Plasticized with Glycerol
Authors: Bergo P. , Sobral P.J.A. , Guevara V.C.I. , Vadala A.C.S.
Published: January 2010

In this work, the method of Fourier transform infrared was used to study the recrystallization phenomenon in cassava starch films containing different plasticizers content and type. The films were obtained by conventional casting method and then, conditioned for several periods in desiccators containing saturated water-NaBr solution and also, in desiccators containing silica gel. From the results, the main changes occurred in the fingerprint region, and were attributed to new interactions arising between the polymeric chains and the plasticizer. The changes in the peak amplitude located near 1015 cm-1 were associated to the formation of semi crystalline junctions in the film matrix, as affected by the plasticizer and moisture content in the films. The slight changes in peak positions were attributed to the modifications in the intermolecular forces in the film matrix. The semi crystallinity nature of films was checked by X-ray diffraction. At macroscopic scale, the flexibility of the films increased, which could favor the reorientation of the macromolecules.
Physical Properties of Gelatin Films Plasticized with Glycerol, Studied by Spectroscopic Methods
Authors: Bergo P. , Carvalho R.A. , Vadala A.C.S. , Guevara V.C.I. , Sobral P.J.A.
Published: January 2010

The effect of glycerol content on the physical properties of gelatin-based edible films was studied in this work, on the basis of the interactions between the plasticizer and polymeric matrix. In this work, some non-usual techniques were used to characterize edible films. For dielectric measurements and infrared spectroscopy, these films were conditioned in silica gel in order to minimize the water effect. For other analysis, the films were conditioned in NaBr. Infrared spectroscopy showed no apparent changes in the position peaks, suggesting an absence of new interactions between the plasticizer and film matrix. It seems that the plasticizers only occupy some specific regions between the polymeric matrix, increasing their distance, and thus, affecting their mobility, which results in more flexible films. Dielectric constant of the films increased with plasticizer content, and decreased over silica gel conditioning. The polarizability was found to arise mainly from water molecules present in the film. Microwave response was found to be also sensitive to water content in the films, due to plasticizer hydrophilic nature. According to the diffractograms, gelatin films presented essentially an amorphous nature, independently of the glycerol content. The results suggest, therefore, that the glycerol induces no chemical modifications in the films.
Modified Polysaccharides as New Commodity Materials and for Light-Converting Systems: Syntheses, Characterization and Processing
Authors: Greco T. , Lehmann A. , Nejad M.H. , Volkert B.
Published: January 2010

Potato starch (PS), also one amylose-rich starch (high amylose maize starch, HAMS) and one amlyopectin-rich starch (waxymaize starch, WMS) were used for the syntheses as raw materials. Starch acetates were synthesized by reaction with acetic acid anhydride and potassium carbonate as activator. Tests of thermoplastic processability of the starch acetates were performed by extrusion followed by injection molding to specimens. Glycerine triacetate (triacetin, TAc) was attached as plasticizer to starch acetate. For this system a processing procedure was acquired under variation of different parameters. Starch- and cellulose-based films containing inorganic luminescent quantum dots, namely europium doped yttrium vanadate (YVO4:Eu) and cerium and terbium doped lanthanum phosphate (LaPO4:Ce,Tb) as well as an organic laser dye (naphthaldiimide, LV 570) were prepared by tape casting and air brush technique. Under UV-light exposure, they show a bright fluorescence radiation depending on the incorporate dye or quantum dot.
Shear Modulus and Strength of an Acrylic Adhesive by the Notched Plate Shear Method (Arcan) and the Thick Adherend Shear Test (TAST)
Authors: Pinto A.M.G. , Magalhães A.G. , Campilho Raul D.S.G. , Silva Lucas F.M. , Chousal J.A.G. , Baptista A.P.M.
Published: January 2010

In this work, the shear modulus and strength of the acrylic adhesive 3M® DP 8005 was evaluated by two different methods: the Thick Adherend Shear Test (TAST) and the Notched Plate Shear Method (Arcan). However, TAST standards advise the use of a special extensometer attached to the specimen, which requires a very experienced technician. In the present study, the adhesive shear displacement for the TAST was measured using an optical technique, and also with a conventional inductive extensometer of 25 mm used for tensile tests. This allowed for an assessment of suitability of using a conventional extensometer to measure this parameter. Since the results obtained by the two techniques are identical, it can be concluded that using a conventional extensometer is a valid option to obtain the shear modulus for the particular adhesive used. In the Arcan tests, the adhesive shear displacement was only measured using the optical technique. This work also aimed the comparison of shear modulus and strength obtained by the TAST and Arcan test methods.
Preparation and Characterization of Amorphous Silica Organofunctionalised with 2-Mercaptobenzimidazole
Authors: Cesarino Ivana , Marino Glimaldo , Cavalheiro Éder T.G. , Nogueira Regina F. , Ferreira Antonio G.
Published: January 2010

Organofunctionalised silica materials are of great interest once they combine a high surface area and a narrow pore size distribution with the advantage of owing organic ligand properties. This paper describes the organofunctionalisation of an amorphous silica with 2-mercaptobenzimidazole. The characterization of such material was performed by elemental analysis (EA), IR spectroscopy, thermogravimetry (TG), differential scanning calorimetry (DSC) and solid state 13C and 29Si NMR spectroscopy.
Modelling of the Thermal Behaviour of Free Form Extrusion
Authors: Costa S.F. , Duarte Fernando M. , Covas José A.
Published: January 2010

The performance of parts produced by Free Form Extrusion (FFE) may be limited by poor mechanical properties, due to poor bonding between the individual extruded filaments. In this work, an analytical solution is proposed for the transient heat transfer during filament deposition, taking into account contacts between filaments. The developed code using Matlab® allows to study the influence of the main process variables during filament deposition and may assist the process optimization.
Surface Modification on Polyamide 6.6 with Double Barrier Discharge (DBD) Plasma to Optimise Dyeing Process by Direct Dyes
Authors: Oliveira Fernando R. , Souto António Pedro , Carneiro Noemi , Nascimento J.H.O.
Published: January 2010

Dyeing of polyamide fibers is normally made with acid dyes, however, it is somewhat difficult to achieve uniformity and control of pH and temperature must be carefully made. The possibility to dye polyamide 6.6 in a larger gamut of colours with good properties may be achieved using other classes of dyes after plasmatic modifications in textile substrates. Polyamide 6.6 fabrics were treated with Double Barrier Discharge (DBD) plasma obtained at atmospheric conditions in a semi-industrial machine and very positive results were obtained when dyeing is made with direct dyes. Surface modifications were evaluated, namely, roughness in terms of Atomic Force Microscopy, changes in chemical composition by X-Ray Photoelectron Spectroscopy (XPS) and microstructural analysis by SEM. In order to optimize dyeing process, different dye concentrations, pH and temperatures were attempted on dyeing with DBD treated fabrics. Important parameters were studied such as exhaustion, colour strength (K/S) and washing fastness. Chemical and physical effects of plasmatic discharge contribute to excellent results obtained in yield, exhaustion and fastness of dyeing of polyamide with direct dyes demonstrating extensive improvement of dye exhaustion from baths, easily achieving 100% in shorter dyeing times. These results mean less dyes in effluents and less time for dyeing processes. The cleanness of the processes and lower cost of direct dyeing are additional advantages when compared to difficulties in acidic dyeing of polyamide.
Structural and Hydrogenation Properties of Zr0.9Ti0.1Cr1.2-xV0.8Nix (x=0, 0.4) Compounds
Authors: Ioannidou A. , Makridis S.S. , Zupanič Erik , Prodan Albert , Kikkinides E.S. , Stubos Athanasios K.
Published: January 2010

The goal of our studies is to find alloy compositions capable of high H capacity and reversible low temperature hydrogenation. In the present research work, specimens with nominal compositions Zr0.9Ti0.1Cr1.2V0.8 and Zr0.9Ti0.1Cr0.8V0.8Ni0.4 have been prepared by arc–melting under argon atmosphere. The microstructural properties of the samples were analyzed by XRD and SEM, while the corresponding microchemistry was determined by EDAX measurements. A two phase system was regularly obtained, with the main component being the hexagonal (C14) Laves phase. The presence of small amounts of Ni has been found to increase the alloy activity on hydrogen. Hydrogen activation was performed for both samples and charging-discharging properties were investigated in the temperature range between 20 oC and 100 oC by using a Sievert-type apparatus.
Chlorapatite Conversion to Hydroxyapatite under High Temperature Hydrothermal Conditions
Authors: García-Tuñón Esther , Franco Jaime , Dacuña Bruno , Zaragoza G. , Guitián Francisco
Published: January 2010

The need for biomaterials in dental and orthopedic applications has increased as the world population ages. Synthetic calcium phosphate bioceramics and calcium phosphate cements are proved potential substitutes for bone and teeth due to their structural and crystallographic similarities with the biological apatites, and their biocompatibility but they show poor mechanical properties. Chlorapatite and hydroxyapatite whiskers with high aspect ratio can be used to improve this drawback. This work describes a method to transform chlorapatite single crystals into hydroxyapatite whiskers, suitable for the reinforcement of calcium phosphate bioceramics and calcium phosphate cements. Hydroxyapatite whiskers were obtained by treating chlorapatite single crystals in high-temperature hydrothermal conditions. The variable studied was furnace temperature with and without moisture conditions. The characterization of the chlorapatite and hydroxyapatite whiskers was carried out by SEM, XRD, EDS and FTIR. SXRD data were analyzed for the description of the chlorapatite structure.
Powder Metallurgical Processes for NiTi Shape Memory Alloys
Authors: Neves Filipe , Braz Fernandes Francisco Manuel , Martins Isabel M. , Correia Jose Brito , Oliveira Manuela , Gaffet Eric , Boucharat Nancy , Lattemann M. , Suffner Jens , Hahn Horst
Published: January 2010

Two promising powder metallurgy (PM) processes were used for the fabrication of NiTi shape memory alloys (SMA): Mechanically Activated Reactive FOrging Synthesis (MARFOS) and Mechanically Activated Reactive Extrusion Synthesis (MARES). In these two processes, equimolar powder mixtures of elemental Ni and Ti are first mechanically activated and then forged/extruded at relatively low temperature. Afterwards, heat treatments are used to promote homogenization and to adjust the composition of the NiTi matrix. When MARFOS and MARES processes are compared some differences have been observed but only in relation to the extent of phase transformation and to the degree of densification. The crystallite size was less than 100 nm for all the phases which indicates nanostructured materials and multi-step martensitic transformations could be observed in heat treated materials.
Microwave Sintering – A Novel Approach to Powder Technology
Authors: Marcelo Teresa , Mascarenhas João M.G. , Oliveira Fernando A. Costa
Published: January 2010

The present paper focus on preliminary work carried out at INETI concerning the use of microwave radiation applied to sintering of both ceramic and metal powders. Due to the characteristics of materials-radiation interaction, microwaves can become an interesting power source in powder technology and other processing routes, since it is possible to lower the sintering temperature and shorten the sintering cycles, leading to time and energy savings.
Alumina, hydroxyapatite, titanium and stainless steel powder compacts were sintered in a modified commercial oven of 2.45GHz and 1000W nominal power. Microwave susceptors were used to enable temperature rise during the initial stage of the sintering cycles. Results on densification and microstructural evaluation of microwave sintered samples are reported and compared to conventionally sintered ones, when available. For similar porosity levels upon sintering, microwave radiation generally reduces sintering times from several hours to minutes. The results obtained so far are quite encouraging since in the case of alumina and stainless steel compacts, a decrease of about 200°C in the sintering temperature was achieved. It was also found that the green density plays a key role in the densification of both metallic and ceramic powders.
Growth Defects and Surface Roughness in TiN-Coated Tool Steel at Various N2 Gas Flow Rates Using Cathodic Arc PVD Technique
Authors: Ali Mubarak , Hamzah E. , Qazi I.A. , Toff M.R.M.
Published: January 2010

In the present study, titanium nitride coatings on tool steel were deposited using cathodic arc physical vapour deposition technique. We studied and discussed the effect of various nitrogen gas flow rate on the surface properties of TiN-coated steel. The coating properties investigated in this work include the surface morphology, surface roughness, line profile and fractal dimension analyses using atomic force microscope. Minimum values for surface roughness, line profile and fractal dimension analyses were recorded at nitrogen gas flow rate of 200 sccm. This is mainly because of the reduction in macro-droplets and minimization of the growth defects, usually produced during etching and deposition stages. Critical limit of nitrogen gas flow rate in TiN coatings were identified and considered an important aspect to understand the performance of TiN PVD-coated steel.
Surface Topography of Coated Papers: From the Evaluation Process to the Quality Improvement
Authors: Velho J. , Santos N.F.
Published: January 2010

This document analyses the importance of topography characterization of coated papers, using precipitated calcium carbonates as pigments, on print quality evaluation. For topographic characterization, a laser profilometry was used as well as scanning electron microscope and a mechanical profilometry. Print quality for inkjet printing was assessed using mottle, gain, optical density and Gamut Area. Surface energy of coated papers and printing inks was evaluated using OWRK method. The results obtained showed that good correlations between print quality characteristics and surface energy as well as topographic properties can be obtained.