bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine-Grained Si3N4-Containing Ceramics from Nanopowders
Authors: Zalite Ilmars , Zilinska Natalja , Krastins Janis , Šteins Ints
Published: January 2010

Different compositions of SiAlON materials have been prepared from separate nanopowders and their composites: Si3N4 – AlN, Si3N4, Al2O3 and Y2O3, produced by the method of plasma-chemical synthesis. Compositions have been pressure-less sintered in nitrogen medium up to 1750°C with a heating rate of 10°C/min and holding time for 2 hours or by spark plasma sintering (SPS) in vacuum at 1700°C with a heating rate of 100°C/min and holding time of 5 min. The densification behaviour of the materials at these sintering conditions depends insignificantly on the powder composition. It is possible to obtain dense ceramic materials with relatively fine-grained structure (200-300 nm) from nanosized powders at relatively low temperatures (1400 - 1600°C) with good mechanical properties.
“White” Crusts on Recent Buildings
Authors: Alves Carlos
Published: January 2010

Materials applied in buildings, sculptures and other civil engineering, architectural or artistic works can be affected by coatings of neoformation products, namely salts. Carbonate rich (typically calcite) coatings are common in recent constructions. They generally have a visual impact (frequently present a vertical streaking pattern and it could be argued that the aesthetic effect of white crusts on dark-coloured stones is similar to that of black crusts on light-coloured stones). The thickness and extension that can be achieved in some cases can be considered an important defacement process that develops in relatively small periods of time. There are evidences that in some situations the process might be recurrent with time. Its chromatic evolution with time could also contribute to increasing heterogeneity with aesthetic consequences. An interesting question regarding these crusts is the possible contribution of certain building materials to its formation, materials that will be, in this way, potential pollution sources that might affect other building materials.
Study of Aggregate Size Effect on Fracture Toughness of Petreous Macrocomposites (Concrete)
Authors: Marques Ana S. , Amaral Pedro M. , Rosa Luis Guerra , Fernandes Jorge Cruz
Published: January 2010

The present study investigates the effect of rock aggregate size on the fracture toughness of a petreous macrocomposite material (concrete). The effect of aggregate size on the fracture properties of concrete was studied by analysing the fracture toughness KIC results obtained using single edge notched beam (SENB) specimens submitted to 4-point bending test. The results were obtained according to the methodology proposed by Srawley and Gross for monolithic ceramic materials. Additionally, the effect of aggregate size has been analysed by performing fractographic examination of unnotched beam specimens also submitted to 4-point bending test. KIc values obtained via linear elastic fracture mechanics (LEFM) theory applied to the fractographic data were comparable to those obtained by SENB method. The obtained results show that the fracture toughness of concrete depends on the aggregate particle size, although KIC is not linearly related with the particle size. Fracture behaviour depends on the interaction between the used mortar (a mixture of portland cement with sand and water) and the different rock (aggregate) particle sizes. This kind of studies allows further extending the knowledge on the failure mechanisms of concrete, which permits to improve the characteristics of these macrocomposite materials by understanding the effects related to the modification of their structure.
Structural Characterisation and Mechanical Stability of Titanium Substituted Mesoporous Materials
Authors: Galacho Cristina , Ribeiro Carrott Manuela M.L. , Valerio Joana , Carrott Peter J.M. , Valente Nabais J.M.
Published: January 2010

Mesoporous silica and titanium SBA-15 samples with different Si/Ti molar ratio were prepared by direct one-step synthesis under strongly acidic hydrothermal conditions. The materials were characterised by X-ray diffraction, nitrogen adsorption at 77K. The Si/Ti values of the final calcined materials were determined by ICP analysis. It was found that all samples presented 2-D hexagonal structures with high degree of ordering. However, the metal content incorporated in all titanium mesoporous materials was very low, i.e., the Si/Ti molar ratio values of the final calcined samples are significantly different from the initial Si/Ti molar ratio in the synthesis gel. A study of mechanical stability in air was performed by exposing the calcined samples to a unidirectional external pressure in the range 74-814MPa. X-ray diffraction and nitrogen adsorption at 77K, on selected compacted samples, were used in order to evaluate the changes in mesoporous structure. It was found that, for all freshly calcined pure silica and titanium containing samples tested, the high quality SBA-15 structure is still observed after the application 148-370MPa of a unidirectional external pressure and the collapse of the pore structure occurs at around 814MPa.
Corrosion Resistance of Alumina-Sialon Refractories for Application in Aluminium Industry
Authors: Pawlik Tomasz , Sopicka-Lizer Malgorzata , Mikuśkiewicz Marta , Gwizdz Malgosia
Published: January 2010

This paper describes the manufacturing and corrosion resistance of sialon based ceramics for application in the modern aluminium industry. Sialon based ceramics are characterized by excellent mechanical properties at high temperatures, good corrosion and thermal shock resistance and low wettability, thus this material is suitable for the long term liquid aluminium contact. To obtain reaction bonded materials in this work, relatively cheap and commonly available components were used: fine Si and Al2O3 powders. The specimens were examined after heating in flowing nitrogen for the phase composition and dimension stability. Sintered materials were tested for corrosion resistance and wettability in liquid aluminium. The microstructure of the contact surface was examined by SEM/EDS methods.
Demonstration of the Robustness of Maximum Likelihood Estimation to Distinguish Mixtures of Two Weibull Populations in Failure Data of Brittle Materials
Authors: Rosa Luis Guerra , Figueiredo Ivone
Published: January 2010

In statistical analysis of failure data of brittle materials, the use of maximum likelihood estimators shows many advantages compared to other methods. The applicability and the robustness of the maximum likelihood method to analyze and to distinguish the data in several mixtures of two Weibull populations is demonstrated in this work. Estimations of percentage of data belonging to each of the populations, as well as Weibull parameters of the populations, are relatively simple to be conducted using adequate software.
Repair Welding Effects on the Bending Fatigue Strength of AISI 4130 Aeronautical Steel Used in a Critical to the Flight-Safety Structure
Authors: Nascimento Marcelino P. , Voorwald H.J.C. , Filho J.C.P. , Pereira Celso Pinto Morais
Published: January 2010

The aim of this study was to analyze the effect of successive TIG (tungsten inert gas) welding repairs on the reverse bending fatigue strength of AISI 4130 steel, which is widely used in components critical to the flight-safety. In order to simulate the abrupt maneuvers, wind bursts, motor vibration and helixes efforts, which generate cyclic bending loadings at the welded joints of a specific aircraft component called "motor cradle", experimental reverse bending fatigue tests were carried out on specimens made from hot-rolled steel plate, 1.10 mm (0.043 in) thick, by mean of a SCHENK PWS equipment, with load ratio R = -1, under constant amplitude, at 30 Hz frequency and room temperature. It was observed that the bending fatigue strength decreases after the TIG (Tungsten Inert Gas) welding process application on AISI 4130 steel, with subsequent decrease due to re-welding sequence as well. Microstructural analyses and microhardness measurements on the base material, heat-affected zone (HAZ) and weld metal, as well as the effects of the weld bead geometry on the obtained results, have complemented this study.
Interlaminar Fracture Characterization of a Carbon-Epoxy Composite in Pure Mode II
Authors: Campilho Raul D.S.G. , de Moura Marcelo F.S.F. , Pinto A.M.G. , Ramantani Dimitra A.
Published: January 2010

The interlaminar fracture toughness in pure mode II (GIIc) of a Carbon-Fibre Reinforced Plastic (CFRP) composite is characterized experimentally and numerically in this work, using the End-Notched Flexure (ENF) fracture characterization test. The value of GIIc was extracted by a new data reduction scheme avoiding the crack length measurement, named Compliance-Based Beam Method (CBBM). This method eliminates the crack measurement errors, which can be non-negligible, and reflect on the accuracy of the fracture energy calculations. Moreover, it accounts for the Fracture Process Zone (FPZ) effects. A numerical study using the Finite Element Method (FEM) and a triangular cohesive damage model, implemented within interface finite elements and based on the indirect use of Fracture Mechanics, was performed to evaluate the suitability of the CBBM to obtain GIIc. This was performed comparing the input values of GIIc in the numerical models with the ones resulting from the application of the CBBM to the numerical load-displacement (P-) curve. In this numerical study, the Compliance Calibration Method (CCM) was also used to extract GIIc, for comparison purposes.
Fiber Bragg Grating Sensors Integrated in Polymeric Foils
Authors: Silva A.F. , Gonçalves F. , Ferreira L.A.A. , Araújo F.M. , Mendes P.M. , Correia J. Higino
Published: January 2010

Optical sensors have hit their maturity and a new kind of systems is being developed. This paper deals with the development of a new sensing structure based on polymeric foils and optic fiber sensors, namely the Fiber Bragg Grating sensors. Sensor integration in polymeric foils, using industrial process is the proposed goal. To achieve this goal, Finite Element Analysis was used for prototype modeling and simulation. The model was subjected to loads and restraints in order to retrieve information about stress distribution and displacement of specific points. From the simulation was possible to predict the sections where the sensor should be positioned. A prototype was then fabricated using industrial processes. Tests indicate that the polymeric foil influence on the sensor performance may exist. However, the prototype was able of transferring the full deformation to the optical sensor. Moreover, the optical sensor, which is incorporated in the polymeric foil, is fully functional with high sensitivity, 0.6 picometer by microstrain, allowing deformation measurements, up to 1.2 millimeter.
The Effect of Ti Addition on the Properties of Al-B4C Interface: A Microstructural Study
Authors: Toptan F. , Kilicarslan Ayfer , Kerti Isil
Published: January 2010

In the present work, Al-B4C composites were produced by casting route at 850°C and titanium-containing flux was used to overcome the wetting problem between B4C and liquid aluminium metal. The microstructure of matrix/reinforcement interface was investigated using SEM studies with or without Ti added composites. The reaction layer was also characterized with EDS analysis and X-ray mapping. It was found from the microstructural observations by high resolution field emission gun SEM (FEG-SEM) that the wetting issue was effectively solved by the formation of very thin (80-180 nm in thickness) Ti-C and Ti-B reaction layers.
Drilling of Carbon Fibre Reinforced Laminates – A Comparative Analysis of Five Different Drills on Thrust Force, Roughness and Delamination
Authors: Durão Luís Miguel P. , Gonçalves Daniel J.S. , Tavares João Manuel R. S. , Albuquerque Victor Hugo Costa , Marques António Torres , Baptista A.P.M.
Published: January 2010

The distinguishing characteristics of carbon fibre reinforced laminates, like low weight, high strength or stiffness, had resulted in the increase of their use during the last decades. Although parts are normally produced to “near-net” shape, machining operations like drilling are still needed. In result of composites non-homogeneity, this operation can lead to delamination, considered the most serious kind of damage as it can reduce the load carrying capacity of the joint. A proper choice of tool and cutting parameters can reduce delamination substantially. In this work, the results obtained with five different tool geometries are compared. Conclusions show that the choice of adequate drill geometry can reduce the thrust forces and consequently, the delamination damage.
Preparation of Chitosan Scaffolds for Tissue Engineering Using Supercritical Fluid Technology
Authors: Duarte A.R.C. , Mano João F. , Reis R.L.
Published: January 2010

The aim of this study was to evaluate the possibility of preparing chitosan porous matrixes using supercritical fluid technology. Supercritical immersion precipitation technique was used to prepare scaffolds of a natural biocompatible polymer, chitosan, for tissue engineering purposes. The physicochemical and biological properties of chitosan make it an excellent material for the preparation of drug delivery systems and for the development of new biomedical applications in many fields from skin to bone or cartilage.
Immersion precipitation experiments were carried out at different operational conditions in order to optimize the processing method. The effect of different organic solvents on the morphology of the scaffolds was assessed. Additionally, different parameters that influence the process were tested and the effect of the processing variables such as polymer concentration, temperature and pressure in the chitosan scaffold morphology, porosity and interconnectivity was evaluated by micro computed tomography. The preparation of a highly porous and interconnected structure of a natural material, chitosan, using a clean and environmentally friendly technology constitutes a new processing technology for the preparation of scaffolds for tissue engineering using these materials.
Production of Thermoplastic Towpregs
Authors: Velosa J.C. , Nunes João Pedro , Silva João F. , Bernardo Carlos A. , Marques António Torres
Published: January 2010

This work establishes process windows for efficient towpreg production on a developed powder coating equipment. Three different thermoplastic towpregs were studied: one for highly demanding markets (carbon fibre/PrimospireTMPR-120) and other two for commercial applications (glass/polypropylene and glass/polyvinyl chloride). Mechanical properties of compression moulded composites obtained from the produced towpregs were also obtained and discussed.
Strength Prediction of Adhesively-Bonded Scarf Repairs in Composite Structures under Bending
Authors: Campilho Raul D.S.G. , de Moura Marcelo F.S.F. , Pinto A.M.G. , Ramantani Dimitra A. , Morais J.J.L. , Domingues J.J.M.S.
Published: January 2010

This work reports on the experimental and numerical study of the bending behaviour of two-dimensional adhesively-bonded scarf repairs of carbon-epoxy laminates, bonded with the ductile adhesive Araldite 2015®. Scarf angles varying from 2 to 45º were tested. The experimental work performed was used to validate a numerical Finite Element analysis using ABAQUS® and a methodology developed by the authors to predict the strength of bonded assemblies. This methodology consists on replacing the adhesive layer by cohesive elements, including mixed-mode criteria to deal with the mixed-mode behaviour usually observed in structures. Trapezoidal laws in pure modes I and II were used to account for the ductility of the adhesive used. The cohesive laws in pure modes I and II were determined with Double Cantilever Beam and End-Notched Flexure tests, respectively, using an inverse method. Since in the experiments interlaminar and transverse intralaminar failures of the carbon-epoxy components also occurred in some regions, cohesive laws to simulate these failure modes were also obtained experimentally with a similar procedure. A good correlation with the experiments was found on the elastic stiffness, maximum load and failure mode of the repairs, showing that this methodology simulates accurately the mechanical behaviour of bonded assemblies.
Combinatorial Study of New Materials Sensing High Temperature
Authors: Lu Ya Lin , Reinhardt Karen A.
Published: January 2010

Interests in finding new rare-earth doped oxide materials able to remotely sense high temperature have been intensifying in recent years. If applied, advanced combinatorial strategy for materials science should be efficient in finding a suitable host material, and in optimizing a rare earth ion’s doping concentration, luminescence intensity, emission lifetime, etc. This research demonstrates our preliminary effort to apply the advanced combinatorial material strategy to this new area of finding materials for sensing high temperatures.
Technology of PLZT Material Used for Photovoltaic Driven Piezoelectric Transformers
Authors: Plonska Malgorzata , Kozielski Lucjan , Podstawek L.
Published: January 2010

Ferroelectric transparent variant ceramics can be used as a base material for photovoltaic driven piezoelectric transformers. This work reports on the preparation conditions of x/65/35 PLZT ceramics for x = 0, 2, 4, 8, 10, 16, 32 at.% La, via conventional mixed oxide method. The study gives a detailed account of the relationships between technology conditions and basic physical properties of obtained PLZT samples as potential material for transformers application.
Simulating Human Physiological Response with a Thermal Manikin Testing Different Non Active Medical Devices
Authors: Braga Iara , Abreu M. José , Duarte F.M.
Published: January 2010

The thermal insulation of a clothing system represents a quantitative assessment of the way cloth provides thermal barrier to the user. One of this clothing systems, the surgical gown used in the operating theatre, is considered as a non-active medical device and obeys the Medical Device Directive 93/43/EEC. New materials and gowns are being developed, fitting the level of the barrier function with the comfort issues and therefore the selection of the most suitable gown is vital. During the last 60 years, thermal manikins have been used to measure clothing insulation and to assess the thermal environment regarding comfort issues. The main goal of the present study is the comparison of the thermal insulation values during the objective evaluation using the dry thermal manikin with the results obtained using an Infra-Red camera ThermaCAM, monitoring the temperature development of different surgical gowns at a constant skin temperature of 33 °C in neutral environmental conditions.
Effect of the Nanostructure Control on the Novel Optical Properties of Silica Photonic Glass Synthesized by VAD Method
Authors: Santos J.S. , Ono E. , Suzuki Carlos Kenichi
Published: January 2010

This research reports the development of high homogeneity silica glass for photonic components synthesized by the VAD (Vapor-phase Axial Deposition) method. Structural radial homogeneity of silica soot were characterized by scanning electron microscopy (SEM) and small angle X-ray scattering (SAXS). It was established a relationship with the refractive index homogeneity, n, and the birefringence of consolidated boules characterized through interferometry, optical spectrometry, and polarization spectrophotometry. By controlling the silica soot nanostructure during the deposition stage, a material with high radial homogeneity of refractive index of 1 ppm and birefringence of 2 nm/cm can be synthesized.
Piezoelectric PZT Thin Films on Flexible Copper-Coated Polymer Films
Authors: Suchaneck Gunnar , Volkonskiy O. , Gerlach Gerald , Hubička Zdenek , Dejneka A. , Jastrabik Lubomir , Kiselev D. , Bdikin I. , Kholkin Andréi L.
Published: January 2010

This work analyzes the processing of Pb(Zr,Ti)O3 (PZT) thin films directly on copper-coated polymer films. PZT thin film deposition was performed onto the metallized Kapton® films using a single RF plasma jet. In order to reduce the interaction of PZT and Cu during the initial growth stage, an ultrathin amorphous TiO2-x seeding layer was sputter-deposited prior to PZT deposition. The film texture was a mixture of (111)-oriented perovskite nanocrystals, rutile and pyrochlore. Topography and piezoelectric in-plane and out-of-plane response of the films were evaluated using a commercial AFM adapted for piezoforce measurements. The as-deposited films were self-polarized with polarization pointing at the surface of the sample. Polarization was switchable and a piezoelectric hysteresis was obtained.
Optical and Structural Characterization of ZnO Films Deposited by Chemical Bath and Activated by Means of Microwaves
Authors: Martínez-Juárez Javier , Díaz-Reyes J. , Juárez-Diaz Gabriel , Galeazzi R. , Galvan-Arellano Miguel
Published: January 2010

Zinc oxide (ZnO) is a direct, wide band gap semiconductor material having many promising properties for UV/blue optoelectronics, transparent electronics, spintronic devices and sensor applications. The ZnO is synthesized by the technique of Chemical Bath Deposition by microwaves heating (MW-CBD). The urea concentration in the solution is varied, maintaining constant the zinc nitrate in ratio 1:1 … 1:10. The physical properties of ZnO thin films were examined by X-ray diffraction (XRD), SEM-EDS, and Raman scattering, which are convenient tools that can provide us with plenty of information about crystal structure and elementary excitons. By X-rays one obtains that it has hexagonal polycrystalline wurtzite type structure. The IR absorption line at 3577 cm-1 detected at 300 K in bath chemical ZnO is assigned an O–H bond primarily aligned with the c-axis of the crystal and bonding between Zn-O (473cm-1, 532 cm-1). The Raman spectra show the first order experimental Raman spectra of ZnO excited by 514.5 nm laser line. The first order Raman modes A1T, E1T, E2(H), A1Land E1L are identified as the peaks sited at 385, 426, 437, 572 and 584 cm-1
Nitrogen Effects on Optical and Electrical Properties of Amorphous Carbon
Authors: Fathallah M. , Alassimi N. , Alzayed N. , Gharbi R.
Published: January 2010

Optical and electrical properties amorphous carbon nitride (a-CN) has been investigated on films deposited by reactive R.F. sputtering source with a graphite target. The amorphous carbon nitride samples were prepared under a gas mixture of nitrogen (N2) and /or Argon (Ar).The optical transitions are governed by the  and * electronic state distributions, related to sp2- and sp1-hybridized C and N atoms. Specific lonepair electronic states arise from groups (CN) with sp1-hybridized C atoms, which may form C≡N triple bonds or —N=C=N— longer chains. Photoluminescence spectra show a maximum around 650 nm. Two conduction regimes at high and low temperature are found in a-CN samples. The corresponding activation energies decrease with the increase of target voltage.
Effect of Annealing on the Optical and Structural Properties of TiO2 RF Sputtered Thin Films
Authors: Selmi Mabrouk , Chaabouni F. , Mbarek I. Ben , Abaab Mohamed , Rezig Bahri
Published: January 2010

Titanium dioxide (TiO2) thin films were prepared by RF magnetron sputtering technique at an argon flow rate of 4.9 sccm and room temperature during 4 h. These films were deposited on pyrex substrates with an RF power of 300 W and annealed at different temperatures (500, 600, 700 and 800 °C). The optical and structural properties were studied by spectrophotometry and X ray Diffractometry respectively. The obtained results show an amorphous structure for the unheated TiO2 films and an apparition of an anatase phase after the annealing process. The transmittance is increased with an annealing of 500°C from 45 to 80 % in the visible and near-infrared regions. The direct band gap, refractive index, extinction coefficient and grain size were investigated. The reflection in the visible range for a silicon (Si(p)) substrate covered by TiO2 thin films is decreased to be about 20%. The results of this work suggest that the variation of the annealing temperature allow the control of the physical properties of TiO2 thin films as antireflective coating for silicon solar cells.
Short Term Oxidation of a Ti-46Al-8Nb Alloy at 700°C in Air
Authors: Ngnekou Paul Erve T. , Lafont Marie Christine , Senocq François , Lacaze Jacques , Viguier Bernard
Published: January 2010

Thermogravimetry was used to study the oxidation behaviour of a lamellar Ti46Al8Nb alloy during holding at 700°C in synthetic air. A parabolic plot of the oxidation kinetics shows three different regimes over the total duration (50 h) of the tests corresponding to decreasing values of the parabolic rate constant. The oxide scale was characterized by glancing-angle X-Ray diffraction and transmission electron microscopy. The scale was found to be bi-layered with an outer part that consists of amorphous aluminium rich oxide whilst the inner layer is made of very small cristalites of titania distributed in the same amorphous oxide.
Effect of Ti on the Corrosion Behaviour of In Situ Mg2Si Particle Reinforced Al–12Si-20Mg-XTi Alloys
Authors: Ahlatci Hayrettin , Durmaz A. , Balta A. , Acarer M. , Candan E.
Published: January 2010

In this study, corrosion behaviour of Al–12Si-20Mg-XTi alloys (Ti content varied between 0 and 4 wt.%) was investigated. Characterizations of the alloys were carried out by microstructural examinations and corrosion tests. Microstructural results showed that precipitation of the Mg2Si phases was observed in Al-12Si-20Mg-XTi alloy matrix as two different morphologies; i.e. as a polyhedral primary particle and as a chinese script. Upon addition of Ti, Al3Ti intermetallic precipitated in the alloy. Corrosion tests were carried out by immersing the alloys in “30 g/l NaCl+10 ml/l HCl” solution. Evaluation of corrosion was determined by measuring weight loss for 24 hours and by potentiodynamic polarization tests. Corrosion resistance of the alloy was approximately constant with 1 wt % Ti addition whereas at higher additions, the corrosion rate increased.
Characterizing Precipitation Defects in Nickel Based 718 Alloy
Authors: Niang Aliou , Huez Julitte , Lacaze Jacques , Viguier Bernard
Published: January 2010

In the present study we examine the crystallographic structure of the , ’’ and  phases present in nickel base 718 alloy. The chemical ordering of Nb atoms and possible planar faults that may be observed in ’’ precipitates are detailed. High resolution transmission electron microscopy (HRTEM) observations of various faults are reported. The decomposition of a matrix dislocation to form a locked V shaped configuration is shown. The observation along [110] type direction allows to identify the type of defect, which is observed as a pure geometric stacking fault.
Effect of Carbon Equivalent on Graphite Formation in Heavy-Section Ductile Iron Parts
Authors: Lacaze Jacques , Armendariz S. , Larrañaga Peio , Asenjo Iker , Sertucha Jon , Suárez Ramón
Published: January 2010

The influence of post-inoculation and of cerium and antimony additions on the solidification process and on the formation of chunky graphite in ductile iron heavy-section parts have been studied previously in the case of near-eutectic alloys. It appeared of interest to complement these works by analysing the effect of carbon equivalent on graphite degeneracy. In the present work, hypo-, hyper- and near-eutectic melts have been cast in large blocks and standard cups. Analysis of the corresponding cooling curves recorded during solidification as well as microstructure observations on these casts have been carried out. A clear effect of carbon equivalent as promoter of chunky graphite formation is observed. The results have been added to the set of data already available and various correlations are discussed.
Texture and Microstructure of Invar® Deformed by Asymmetrical Rolling
Authors: Solas Denis , Chhann Sorphal , Baudin Thierry , Penelle Richard
Published: January 2010

Asymmetrical rolling, in which the circumferential velocities of the working rolls are different, is a method to impose shear deformation in addition to the thickness reduction. As a consequence, the deformation texture can be modified as compared to the classical rolling. In this work, the asymmetrical rolling of invar (Fe-36%Ni) and the influence of the deformation route are studied. The Invar® alloy has been deformed by asymmetrical rolling with a 83% thickness reduction. The texture of the deformed alloy was measured by X-ray diffraction at different levels through the thickness: upper side- middle- down side. With asymmetrical rolling, the deformed texture is a copper type texture but the components were rotated about 5-7° around the Transverse Direction (TD) axis as compared to the ideal position of these components in the pole figure representation. The rotation of the pole figure is an indicator of the amount of shear really introduced in the material during asymmetrical rolling. Finally, a simple model was developed in order to establish the condition to obtain either shear texture or grain refinement.
Effect of Mechanical Activation on Ti-50Ni Powder Blends Reactivity
Authors: Neves Filipe , Braz Fernandes Francisco Manuel , Correia Jose Brito
Published: January 2010

In the present study, equiatomic powder blends of Ni and Ti were mechanically activated for a short period of time in a planetary ball mill using different levels of energy input. The characterization of the mechanically activated materials was achieved by scanning electron microscopy, X-ray diffraction, differential thermal analysis and chemical analysis (oxygen and nitrogen measurements). During mechanical activation no phase transformation was induced and the high temperature reaction between Ni and Ti elemental powders was shifted to lower temperatures. Moreover, the temperature and the intensity of the exothermic reaction, i.e. the reactivity observed in the powder blends, decreased with the increase in the level of milling energy input. A maximum oxygen content of 0.39 wt% was measured after mechanical activation.
Characterization of the Diffusion Zone Developed in a Bimetallic Steel-Bronze at Interface
Authors: Ciocan A. , Potecasu F. , Drugescu E. , Constantinescu Simona
Published: January 2010

The paper presents the results of theoretical and experimental research regarding the establishing of some chemical positions of the bearing alloy and of cladding technology. The final properties of the materials depend on the kinetics and thermodynamics of the interface processes. In the paper the diffusion zone developed between the two bimetal materials is revealed and characterized under the aspect of chemical composition and structure. An application for this research that could lead to increasing the endurance of the steel products cladded through welding is the case of boring bits with three cones, which work under short oiling conditions and variations of the contact pressure.
The Relation between the Plunge Pressure and the Mechanical Properties of Friction Stir Welded 3mm Thick AA6082-T651 Sheets
Authors: Louro Rui , Almeida Leitão Carlos Miguel , Puehringer T. , Gouveia Helena , Loureiro Altino , Rodrigues Dulce Maria Esteves
Published: January 2010

Friction Stir Welding (FSW) is a relatively young technology in the field of welding. Its process parameters and their influence on weld quality are currently the topic of intense research. Present work focuses on the influence of the tool plunging force on the mechanical properties, microstructure and surface finish of friction stir welds. Three welds have been produced using the same tool rotation and traverse speed and different tool dimensions and plunging forces. Visual inspection, optical and scanning electron microscopy were undertaken to assess surface and dimensional features as well as to study microstructure. Bend, hardness and tensile tests were carried out to characterise the weld strength. Taken into account the plunging force values of the conducted welds, a relationship between weld properties and calculated welding pressures was created. Favourable welding pressure values are recommended.
Microstructural Signatures of Bronze Archaeological Artifacts from the Southwestern Iberian Peninsula
Authors: Valério P. , Silva Rui Jorge C. , Araújo M.F. , Soares A.M.M. , Braz Fernandes Francisco Manuel
Published: January 2010

This study concerns the elemental and microstructural characterization of proto-historic bronze rings from the southwestern Iberian Peninsula. Micro-EDXRF analyses demonstrate that the artifacts are binary bronze alloys (8–13% Sn) with arsenic and lead as the major impurities. Optical microscopy and SEM-EDS allowed the identification of common inclusions (e.g. copper sulphides) and alteration processes (redeposited copper, intergranular and intragranular corrosion). Microstructures consisting of fine dendrites, coarse and/or equiaxial grains were also identified, as well as the presence of (+) eutectoid, deformed inclusions, twinned grains and/or slip bands. The combination of these characteristics allowed establishing the metallurgical procedures (casting, forging and annealing) used in the production of the bronze rings. The identification of different thermomechanical operational sequences indicates that the metallurgical knowledge was well established in the southwestern Iberian Peninsula during those ancient times.
Analysis of Fibrous Composition for Hygienic Purpose – Recommendations for Application on Feminine Underwear
Authors: Malheiro Joana , Salvado Rita
Published: January 2010

The vulva-vaginal infections are common in women. The textile materials, used in underwear and absorbent hygiene products, are identified as risk factors, but their influence on the emergence of these infections is not yet clear. Bacterial adhesion is associated with persistence of microorganisms in the material that is related to the recurrence of infections. This paper is an initial attempt for the elucidation of these questions. Some of the main features involved in this phenomenon are identified and characterized.
Modifications of Alloying Elements in Martensitic 8-10%Cr-Steels and its Influence of Neutron Irradiation on Material Properties
Authors: Materna-Morris Edeltraud , Lindau R. , Moslang A.
Published: January 2010

9 – 12%Cr-MoVNb steels are successful materials for the use at higher temperatures. The universal application in turbines and power plants promises an expedient material for fission and future fusion reactors. Different developmental alloys were fabricated, irradiated and mechanically tested to optimize the material properties. Already, after the first irradiation tests could be shown that this type of steel has a reduced swelling and much faster decay of radioactivity than e.g. austenitic Cr-Ni-steels. This inherent property of reduced activation includes a high recycling potential. Further variations in the chemical compositions were carried out to increase the decay of radioactivity and to reduce the hardening and strengthening by neutron irradiation. The state of development today is a 9%Cr-WVTa-alloy, which is called EUROFER. The post-irradiation behavior and the development of material matrix are shown in comparison with further test alloys. The emphasis is to characterize the hardening mechanisms by irradiation at lower temperatures, which appear in helium bubbles, interstitial loops, and α`-precipitates.
Microstructure and Hardness of Friction Stir Welds in Pure Copper
Authors: Leal Rui M. , Almeida Leitão Carlos Miguel , Loureiro Altino , Rodrigues Dulce Maria Esteves , Vilaça Pedro
Published: January 2010

The aim of present research was to study the effect of the position of the tool relative to the support backing plate of the FSW machine on the formation of defects and on alterations of the microstructure and mechanical properties of friction stir welds in phosphorus-deoxidised copper (Cu-DHP) thin sheets of 1 mm thick. The welds were carried out using position control conditions; distances between the tool and the backing plate of 0.1 mm, 0.075 mm and 0.05 mm were used. The formation of defects like continuous voids along the weld is very influenced by the tool position, though the heat-input plays an important role in the process. Large grain refinement was observed in the nugget of the welds; the change of the relative tool position has little effect on this grain refinement. Substantial hardening was observed in the thermomechanically affected zone (TMAZ) of the welds. The welds exempt of defects, such as continuous voids, attained a little tensile strength overmatch condition.
Microstructural Development in a Ternary Al-Cu-Si Alloy during Transient Solidification
Authors: Ferreira Ileao L. , Moutinho D.J. , Gomes L.G. , Rocha O.L. , Goulart Pedro R. , Garcia Amauri
Published: January 2010

Macrosegregation and microporosity formation numerical models are dependent on microstructural parameters, such as primary and secondary arm spacings to provide the permeability coefficient in the mushy zone. As can be observed in the literature, growth models for ternary alloys for unsteady solidification are rarely found. In this paper, the primary (λ1) dendrite arm spacing was measured along the length of an Al-Cu-Si alloy casting and correlated with transient solidification thermal variables. A combined theoretical and experimental approach has been carried out to quantitatively determine such thermal variables, i.e., transient metal/mold heat transfer coefficient, liquidus isotherm velocity and cooling rate ahead the liquidus front.
Mechanics of Turbostratic Carbon Nanotubes Filled with Ga-Doped ZnS
Authors: Costa P.M.F.J. , Cachim Paulo B. , Gautam U.K. , Bando Yoshio , Golberg D.
Published: January 2010

The mechanics of a filled carbon nanotube has been evaluated inside a transmission electron microscope employing different procedures. It is found that using a force sensor mounted on a dedicated sample holder is the most reliable method of those explored. In addition to mechanical response visualisation, properties such as elastic modulus may be directly extracted using this commercially available holder.
Effect of Heat Treatments on Mechanical Properties and Fatigue Resistance of Ti-35Nb Alloy Used as Biomaterial
Authors: Cremasco Alessandra , Ferreira Itamar , Caram R.
Published: January 2010

Titanium alloys form the most versatile class of metallic materials used as biomaterials. Among them it is foreseen that the  type titanium alloy will be a prominent one for orthopedic applications. Aim of the present work was to prepare and characterize a  type titanium alloy containing 35 wt.% Nb. Samples were cooled from the  phase temperatures at different rates. This work includes the effects of heat treatment on the microstructure and hardness, tensile and fatigue properties in air at room temperature. The results showed that microstructure of slow cooled samples are formed by precipitates of  and  phases in a  matrix. After rapid cooling, the microstructure consists of  phase and ” martensite. Mechanical testing showed that the elastic modulus and Vickers hardness of slow cooled samples were significantly higher than that obtained by rapid cooling. On the other hand, it was observed that slow cooled samples showed higher tensile strength and lower ductility. The rapid cooled sample showed fatigue resistance higher than that of slow cooled samples.
Crystallization Behaviour of TiO2 Nanoparticle Reinforced Polypropylene
Authors: Noll Andreas , Knoer Nicole
Published: January 2010

Composites of isotactic polypropylene (iPP) with different TiO2 nanoparticle loads (0.5 vol.%, 2 vol.% and 4 vol.%) were compounded by optimized twin screw extrusion. The crystallization behaviour of these semicrystalline nanocomposites was examined by differential scanning calorimetry (DSC), scanning electron microscope (SEM) and polarized optical light microscope (POM) combined with a hot stage module to pursue in-situ the structure development. Wet chemical etching was applied to highlight morphological details like spherulites and lamellar structures for SEM observations. An obvious influence of TiO2-nanoparticles on the crystallization could be verified.
Carbon Nanotubes Grown with Non-Ferromagnetic Catalysts in Alcohol CVD
Authors: Borowiak-Palen E. , Steplewska A. , Bachmatiuk A. , Rümmeli M.H. , Kalenczuk R.K.
Published: January 2010

In this contribution we present high resolution transmission electron microscopy (HR-TEM) and Raman studies on the synthesis of carbon nanotubes using platinum supported on MgO in alcohol - chemical vapour deposition (A-CVD). For comparison copper and iron catalysts mixed with the same metal loading in MgO and the same process parameters in A-CVD have been tested. Our findings show that the choice of catalyst utilized under the same experimental conditions strongly influences the final morphology of the carbon nanostructures. Application of Pt/MgO in CVD results in doublewalled carbon nanotubes (DWCNT) and multiwalled carbon nanotubes (MWCNT). Cu/MgO mixtures lead to the synthesis of copper filled multiwalled carbon nanotubes (Cu-MWCNT) and iron capsules surrounded by multiwalled carbon shells (Fe-MWCS), respectively. Our findings indicate that the three discussed metals interact differently with the substrate leading to the formation of different sized catalyst particles. The analysis of the particles size in the catalyst precursors and in the final products is also described in this contribution.
Synthesis and Characterization of Nanoparticles and Nanocrystalline Functional Films
Authors: Thareja Raj K. , Mohanta A. , Yadav D. , Kushwaha A.
Published: January 2010

This work reports on spectroscopic investigations of interaction of an expanding laser ablated plume of aluminum, zinc, graphite with ambient atmosphere of oxygen and nitrogen gas and the formation of nitrides and oxides. The ambient pressure and fluence dependence on the reactive process occurring in the ablated plume responsible for formation of oxides and nitrides is discussed. Fast photography/imaging technique using intensified charge coupled device (ICCD) is gaining importance as a diagnostic tool for understanding the dynamics of the expanding plasma plume and the gas phase nanoparticle synthesis, thus providing a novel way to understand the transportation of nanoparticles and of control of particle size. Two dimensional images of the expanding plasma plume were captured using ICCD to understand the role of vapor and shock temperature. A comprehensive study done on oxide and nitrides films using pulsed laser deposition technique for possible laser oscillations in UV region of electromagnetic spectrum is presented.
Investigations of the Correlation between the Preparation Method and the Properties of Anilinic Derivative Functionalised Polymer Thin Films for Non-Linear Optical Applications
Authors: Stanculescu Anca , Socol Marcela , Albu Ana Maria , Rasoga O. , Stanculescu Florin , Ionita I. , Enculescu Ionut
Published: January 2010

This paper presents a study of two copolymers, maleic anhydride and methylmethacrilate/maleic anhydride and vinyl benzyl chloride, functionalised with polar chromophoric groups such as 2,4 dinitroaniline. Thin films have been prepared by vacuum evaporation and spin coating methods on silicon and glass substrates. UV-VIS, FTIR, XRD and Photoluminescence Spectroscopy have been used to comparatively investigate the effect of the preparation method on the properties of the thin films obtained with functionalized copolymer. SEM has evidenced differences in the morphologies of the layers suggesting a degradation of the polymeric chain during the evaporation process to fragments that conserve unchanged the chromophoric group. This explains the presence of two types of non-linear phenomena, the second harmonic emission and two-photon luminescence emissions for both vacuum evaporated and spin coated films.
The Morphology during Extrusion of PA6/PP Blends in the Presence of Nanoclays
Authors: Almeida Maria Ferreira , Machado Ana Vera , Covas José A.
Published: January 2010

The present study investigates the morphology of polyamide (PA6) and polypropylene (PP) blends in the presence of an organoclay during extrusion. Physical PA6 /PP blends and blends of PA6/PP and PP modified with maleic anhydride, both filled with a montmorillonite (MMT) modified alkyl ammonium organoclay, were prepared in a modular co-rotating twin screw extruder. Samples were collected along the extruder and analyzed by X-ray diffraction (XRD), oscillatory rheology, and scanning and transmission electron microscopy (SEM and TEM, respectively). Intercalation and some degree of clay exfoliation seem to have been achieved. Generally, the presence of the organoclay yields a finer dispersed phase along the extruder.
Plasmon-Enhanced Luminescence Useful for Wavelength Shifting in Solar Cells
Authors: Li Ling , Lu W.X. , Lu Ya Lin
Published: January 2010

Increasing spectral coverage of a solar cell over the entire solar spectrum is one of the most important energy harvesting ways. In this research, an alternative approach of using plasmon-enhanced luminescence to realize an efficient wavelength shifting potentially useful for solar cells was discussed. Plasmon-enhanced luminescence was experimentally shown in erbium-doped yttria films integrated with arrays of metallic nanostructures having different sizes, in which a strongly enhanced and nanoparticle size-dependent luminescent behavior was observed.
Synthesis, Characterization and Electrical Properties of Single Phase La0.9Sr0.1Ga0.8Mg0.2O3
Authors: Gaki Anna , Kakali G. , Wiglusz R.J. , Strek W. , Paściak Grzegorz
Published: January 2010

Single phase La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM9182) was synthesized by a polymeric precursor route. The XRD pattern after calcination at 1300 °C for 6h indicates the formation of the perovskite without the presence of secondary phases. XRD, FTIR and TG-DTG measurements were used to examine the powder precursor as well as the intermediate and final products. SEM images indicated the small grain size of the final product. The conductivity of the sintered sample was examined by means of a.c. impedance spectroscopy and was found to be 9.10-2 S/cm at 800 °C similar to the typical value of LSGM materials.
Effect of V Substitution on the Composite Zr-Ti-Cr-V-Ni Intermetallic Hydrides
Authors: Makridis Sofoklis S. , Ioannidou A. , Zupanič Erik , Prodan Albert , Kikkinides E.S. , Stubos Athanasios K.
Published: January 2010

Hydrogen storage in reversible metal hydrides is attractive because it can be stored at relatively low pressures with a high volumetric density. In the present research work have been investigated compounds with nominal compositions Zr0.8Ti0.2Cr1.2V0.4Ni0.4 and Zr0.8Ti0.2Cr0.8V0.8Ni0.4 that have been prepared by arc-melting under argon atmosphere. Structural characteristics have been studied by using X-ray powder diffraction while the patterns have been analyzed by using the Rietveld analysis. A main hexagonal Laves phase MgZn2 (C14) and a secondary MgCu2 (C15)-type of, have been found in the powdered compounds. The bulk samples have composite microstructures but the V-rich is characterized by a dendritic microstructure. The high resolution scanning electron microscopy (HR-SEM) and energy dispersive X-ray analysis (EDAX) have been used for the morphology and quantitative analysis, respectively. Hydrogenations and dehydrogenations have been obtained after crucial activation procedure. The alloys were found to be more active under hydrogen after activation while the desorbed amount of hydrogen has been measured by using a Sievert-type apparatus.