bluuebunny/crossref_metadata_2025 huggingface dataset:
Immobilization of Hydride Tungsten Complex in Microporous Structures
Authors: Costa Filomena , Fonseca António Maurício C. , Neves Isabel , Carvalho Ana P. , Pires João
Published: March 2009

A hydride tungsten complex, [WH2(η2-OOCCH3)(Ph2PCH2CH2PPh2)2][BPh4], was entrapped in the interlayer of a pillared layered clay (PILC) and in NaY zeolite. The adsorption of the complex in the liquid phase was the immobilization process used. The free complex and the new materials were characterized by several techniques: structural analysis by DRX, nitrogen adsorption
isotherms and spectroscopic methods (ICP-AES, FTIR and UV/Vis). Analysis of the data indicates that the tungsten(IV) complex is immobilized in the host microporous structures, and exhibit structural properties that are different from those of the free complex. These differences could arise either from distortions caused by steric effects imposed by the structures or from interactions with
the host matrix.
Adsorption of Surfactants on Polymer Surfaces Investigated with a Novel Zeta-Potential Measurement System
Authors: Reischl Martin , Stana-Kleinschek Karin , Ribitsch Volker
Published: March 2009

The determination of electrokinetic properties such as the zeta-potential of polymer
samples with classical methods is laborious and time-consuming. For this reasons, a reliable, fast,
and easy to use measurement system based on streaming potential measurement was developed. In
this novel measurement system, streaming potential is created by an oscillating flow of a small
amount of electrolyte solution through the sample media. In addition, this setup allows direct
titration and therefore time-resolved monitoring of changes in zeta-potential in a seconds timescale.
With this instrument, the concentration- as well as the time-dependent adsorption behaviour of
various non-ionic, anionic and cationic surfactants on a novel, regenerated cellulosic polymer was
investigated. This new cellulose-based, fibrous textile polymer is permanently cationised, not only
at the surface but throughout the whole fibre.
The results show that even very low concentrations of surfactant, due to its charge and chemical
composition, highly influence the surface charge of the polymer in a large range. Furthermore, the
results for this new textile material are compared with other textile fibres, e. g. wool.
Electrocatalytic Behavior of Perovskite-Related Cobaltites and Nickelates in Alkaline Media
Authors: Poznyak Sergey K. , Kharton Vladislav V. , Frade Jorge R. , Yaremchenko Alrksey A. , Tsipis Ekaterina V. , Marozau Ivan P. , Ferreira Mário G.S.
Published: March 2009

Dense ceramic anodes of perovskite-type La1-x-ySrxCo1-zAlzO3-δ ( x = 0.45-0.70; y = 0-
0.05; z = 0-0.20) and K2NiF4-type La2Ni1-xMexO4+δ (Me = Co, Cu; x = 0-0.20), synthesized by the
glycine-nitrate technique, were assessed for oxygen evolution in alkaline media. The lowest
overpotentials are observed for (La0.3Sr0.7)0.97CoO3-δ, which exhibits a significant oxygen deficiency
in combination with high conductivity associated with the A-site cation nonstoichiometry
compensation mechanism via Co4+ formation. Perovskite-type cobaltite anodes are essentially
stable in alkaline solutions, whilst La2NiO4-based electrodes exhibit degradation at the potentials
where the oxygen evolution occurs, probably due to the electrochemical oxygen intercalation in the
lattice.
A Comparison between X-Ray Diffraction and Petrography Techniques Used to Determine the Mineralogical Composition of Granite and Comparable Hard Rocks
Authors: Amaral Pedro M. , Fernandes Jorge Cruz , Rosa Luis Guerra
Published: March 2009

Petrography and X-ray diffraction techniques are used in this work to determine the
mineralogical composition of a granite, a gabbro and a quartzite. The experimental difficulties and
the results obtained by both methods are described and discussed. The semi-quantitative procedure
of XRD analysis used in this work allows an estimate of the relative mineral phase composition of
each type of rock. Petrography was found to be crucial in terms of textural analysis.
Performance and Friction Properties of Injection Hybrid Moulds with Stereolithography Moulding Zones
Authors: Westphal Mathias G. , Pouzada António Sergio , Salmoria Gean V. , Ahrens Carlos H.
Published: March 2009

Stereolithography is a rapid manufacturing process that builds objects layer-by-layer
based on the photo polymerization of a liquid resin. Due to the good geometric precision, this
process has been used in Rapid Tooling for injection moulding. These tools are suitable for the
production of short runs of parts and prototypes, where without resorting to the manufacture of a
conventional metallic mould. The mechanical and thermal properties of the stereolitography resins,
used in the manufacture of hybrid moulds, differ substantially from those of the conventional
metallic materials. Particularly they must be known for guaranteeing the structural integrity and the
thermal performance of the mould. Also the chemistry behaviour of the resin in contact with the
polymer is important when tribological aspects are involved, especially during the ejection of the
moulding.
In this work, the behaviour of hybrid moulds with SL Vantico 5260 resin moulding cores was
assessed. Several thermoplastics (iPP, ABS, PET and PA 6.6) were moulded, and their mechanical,
thermal and chemical properties considered and related to the performance of the moulding process.
Also, the friction properties of the SL resin in contact with the moulded thermoplastic in moulding
conditions were observed and considered in the context of the performance of hybrid moulds.
Experimental Phase Diagram of the Ternary Bi-Sn-Zn
Authors: Braga M. Helena , Malheiros Luis Filipe , Soares Delfim , Ferreira Jorge A. , Castro F.
Published: March 2009

Bi-Sn-Zn is one of the systems being used as substitute of the traditional lead solders.
Therefore a deeper knowledge of its phase diagram is a priority. Due to the lack of data about the
thermodynamic properties of terminal solid solutions as well as on their phase boundaries, only
binary contributions were utilized and the ternary terms were ignored on the published assessments
[1, 2]. Samples corresponding to several vertical sections were prepared and DTA, SEM/EDS and
XRD at room and high temperatures were performed. It was concluded that ternary terms should be
held in consideration in a future assessment of the system.
Separation of the Pyro- and Piezoelectric Response of Electroactive Polymers for Sensor Applications
Authors: Castro Hélder F. , Lanceros-Méndez Senentxu , Rocha José Gerardo
Published: March 2009

One of the main problems for the use of ferroelectric materials for sensor applications, especially for tactile sensors, is the separation of the pyro- and piezoelectric responseproduced by temperature and pressure changes, respectively. We present two different approaches to achieve this goal. The first approach is based on the study of the signal in the frequency domain and uses a
signal processing to separate the approach is based on a double layer configuration of electroactive polymers. In this case, the piezoelectric response is equal in each layer, whereas, the pyroelectric response dominates in the layer exposed to the temperature variations. The pyro- and piezoelectric responses are separated by
estimating the diference between the signals of two layers and the signal from one of the layers, correspondingly.
Processing-Microstructure-Properties Relationships in Extrusion of Thermoplastics
Authors: Carneiro Olga S. , Viana Julio , Nóbrega João M.
Published: March 2009

In this work, a rectangular polypropylene profile was produced with several different
extrusion conditions, in order to identify the most relevant processing variables determining its morphology and mechanical properties and to establish relationships between them. A Taguchi Design of Experiments (DOE) technique considering two levels for each variable (extrusion temperature, extrusion throughput, drawdown ratio and distance between the die and the cooling
bath) defined the set of extrusions runs carried out. The resulting plastic profiles were characterized in terms of their microstructure and mechanical properties. It was concluded that the most significant processing variable determining the mechanical properties of the profiles is the extrusion temperature and that the drawdown ratio controls the degree of molecular orientation of the profile
and, therefore, the extension of its shrinkage after heatiing.
Formation of Bone-Like Apatite on Polymeric Surfaces Modified with -SO3H Groups
Authors: Leonor Isabel B. , Kim Hyun Min , Balas Francisco , Masakazu Kawashita , Reis Rui L. , Kokubo Tadashi , Nakamura Takashi
Published: March 2009

Sulfonic groups (-SO3H) were covalently attached on different polymeric surfaces enabling them to induce apatite nucleation, for developing bioactive apatite-polymer composites with a bonelike 3-dimensional structure. High molecular weight polyethylene (HMWPE) and ethylene-co-vinyl alcohol co-polymer (EVOH) were used. The polymers were soaked in two types of sulphate-containing solutions with different concentrations, sulphuric acid (H2SO4) and chlorosulfonic acid (ClSO3H). To incorporate calcium ions into to the sulfonated polymers, the
samples were soaked in a saturated Ca(OH)2 solution for 24 hours. After soaking of the samples in a simulated body fluid (SBF), formation of an apatite layer on both surfaces was observed. The results obtained prove the validity of the proposed concept and show that the -SO3H groups are effective on inducing apatite nucleation on the surface of these polymers.
The Physical, Mechanical and Thermal Analysis on Methoxy Functional Silicone Intermediate Resin Blending with Acrylic Polyol Resin
Authors: Vengadaesvaran B. , Puteh R. , Arof A.K.
Published: March 2009

Silicone modified acrylic polymer dispersion was prepared by blending
methoxy functional silicone intermediate resin with acrylic polyol resin in different
ratios. The physical, mechanical and thermal properties were investigated. The
physical property of the blend has been carried out by using Kruss G40 contact angle
measuring system, mechanical property of the blend evaluated by using impact
resistance tester and adhesion tester (Cross Hatch- Cutter) and thermal analysis has
been carried out by using Metler Toledo thermal analysis system DSC821. It is found
that the incorporation of 50% silicone resin with 50% acrylic resin gives good
adhesion on metal substrate (mild steel substrate) and optimal cross-linking is
achieved.
Development of a Coating System for High Temperature Corrosion Protection
Authors: Ramesh K. , Abidin Z.H.Z , Osman Zurina , Basirun Wan Jeffrey , Arof A.K.
Published: March 2009

Corrosion protection is one of the important performance properties of organic coatings. In this study, an attempt has been made to develop a high temperature coating. Different compositions of silicone and polyester resins are taken and mixed well with the addition of a hardener. The binder system is applied on the pre-treated cold rolled steel panels. Physical and mechanical properties are evaluated. Thermal resistance of the coating system is done according to specification of ASTM D2485 standards. DSC and TGA analyses are carried out to study the glass transition temperature and temperature dependence of the sample prepared respectively. Corrosion protection ability of the system is evaluated by electrochemical impedance spectroscopy (EIS) and immersion studies. From the thermal studies, the coating containing 40% silicone and 60% polyester has withstood up to 498 K.
Structural and Optical Analysis of GaN Films Grown by Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Yam F.K. , Zainuriah Hassan , Haslan Abu Hassan , Kordesch M.E.
Published: March 2009

This paper presents an analysis of the characteristics of two gallium nitride (GaN) films
grown on (0001) plane sapphire substrates by low-pressure metalorganic chemical vapor deposition
(MOCVD) is presented. The GaN films were characterized by a variety of methods, including
scanning electron microscopy (SEM), x-ray diffraction (XRD), photoluminescence (PL), and
Raman scattering. SEM micrographs revealed that different growth conditions will lead to different
surface morphology of the films. XRD measurements indicated that both films were highly oriented
and mono crystalline. PL spectra for both samples exhibited an intense and sharp band edge peak at
3.42 eV with full width at half maximum (FWHM) of 15 and 35 meV respectively. Raman
scattering showed that the peaks of E2(high) phonon mode were observed at 568.1 and 570.1 cm-1
respectively. The different growth mode of these films were linked to the growth conditions, in
which the growth mechanism could be correlated with the shift of E2(high) phonon mode in Raman
scattering.
Molecular Orientation of Phospholipid Langmuir-Blodgett Films
Authors: Sulaiman Khaulah , Majid Wan Haliza Abd , Muhamad Muhamad Rasat
Published: March 2009

The molecular organization of the phospholipids Langmuir-Blodgett (LB) films on solid
substrates has been studied via Fourier Transform Infra Red (FTIR) spectroscopy. In this study, the
formation of well organized ultra thin LB films of phospholipid molecules has been performed by
depositing the monolayer onto the solid substrates of silicon wafer. The space filling molecular
models of two types of phospholipids have been proposed on the basis of the FTIR spectra.
Crystallinity Studies of GaN/Si Films Grown by MOCVD at Various Substrate Temperatures Using XRD
Authors: Ng Sha Shiong , Zainuriah Hassan , Haslan Abu Hassan , Kordesch M.E.
Published: March 2009

In this paper, we report on the characterization of a set of MOCVD grown GaN
samples with a variety of structural or crystalline quality. X-ray diffraction (XRD) was used to
observe the change of the crystalline structure with deposition temperature. All results show that
the structure type of the GaN deposited films is sensitive to the growth temperature. Our results
also revealed that a good crystalline structure of GaN films could be grown at temperatures higher
than 600°C. Finally, a general picture on the correlations between the growth temperature and the
GaN deposited films crystalline is reported.
Characteristics of Indium Oxide Rod-Like Structures Synthesized on Sapphire Substrates
Authors: Kim Hyoun Woo , Myung Ju Hyun , Shim S.H. , Hwang Woon Suk
Published: March 2009

In2O3 materials consisting of dense arrays of vertically aligned rod-like structures were deposited on sapphire substrates by thermal chemical vapor deposition (CVD) using triethylindium (TEI) and oxygen as precursors at a substrate temperature of 350 oC. The rod-like structure with a triangular cross section had a cubic structure, exhibiting preferred crystallographic orientation in the [111] direction. The photoluminescence spectra of In2O3 structures under excitation at 325 nm revealed a visible emission.
Nano-Second Surface Modification of Titanium Nitride Thin Film by Nd:YAG and TEA CO2 Lasers
Authors: Gaković B. , Pongrac I. , Petrović S. , Minić D. , Trtica M.
Published: March 2009

In this work we investigated the interaction of ns laser pulses (TEA CO2 and Nd:YAG)
with a titanium nitride (TiN) thin film. The TiN thin film of 1μm thickness was deposited by PVD
method on silicon substrate. Modification of TiN film was induced by laser pulses with power
densities of about 108 and 109 W/cm2. Part of the laser energy absorbed on the target surface was
converted into thermal energy and effects such as melting, vaporization and exfoliation were
observed. Nd:YAG laser produced craters with sharp periphery, while TEA CO2 laser created
damages with broad boundary zone. Hydrodynamic effects were especially pronounced during
irradiation with TEA CO2 laser.
Rare Earth Doped Crystals for Quantum Information: Quantum Computing and Quantum Storage
Authors: Goldner Philippe , Guillot-Noël Olivier
Published: March 2009

Quantum information uses special properties of quantum systems to manipulate or transmit data. This results in new processes, which are impossible to obtain with classical devices. For example, quantum computing and quantum storage, which are two important fields in quantum information research, aim respectively at performing very fast calculations and at storing quantum states of photons. These two applications could be obtained in solid-state systems using rare earth doped crystals. In this context, the most important property of these materials is the long coherence lifetimes of rare earth ion optical and hyperfine transitions. This allows one to create long-lived superposition states, which is a fundamental requirement for efficient quantum computing and storage. Promising results have already been demonstrated in rare earth doped crystals but it will be difficult to improve them with current materials. In this paper, we discuss the general and specific requirements for rare earth ions and crystals in order to perform quantum computing with a large number of quantum bits as well as all solid-state quantum storage. We also present the properties of a few recently studied crystals: Ho3+:YVO4, Ho3+:LuVO4 (quantum computing) and Tm3+:Y3Al5O12 (quantum storage).
Boron Nitride Supported Metal Catalysts: Influence of the Metal and Preparation Method
Authors: Postole G. , Gervasini A. , Auroux A. , Bonnetot B.
Published: March 2009

In this study we report on the preparation and characterization of boron nitride supported
noble metal catalysts with potential applications as catalysts for oxidation reactions. The deposition
and the dispersion of the active phase were strongly influenced by the preparation process and in
particular by the solvent used as the dispersing phase. Techniques such as BET, XRD and TEM
were used to study the role played by the phase used as solvent (benzene, glyme, water, THF,
diglyme, isopropanol, glycol) in particles size and dispersion of metals deposed on the BN support.
Different palladium depositions under various conditions and different noble metal coatings under
the same deposition condition are presented. The catalytic performances were tested in methane
traces oxidation in excess oxygen and in the presence of water. The light-off temperature (50 %
methane conversion) increased in the following order: Ag/BN < Pt/BN < Au/BN < Pd /BN.
Arc-Discharge Synthesis of Carbon Nanohorns and Multiwalled Carbon Nanotubes
Authors: Mirabile Gattia Daniele , Vittori Antisari Marco , Marazzi Renzo , Pilloni Luciano , Contini Vittoria , Montone Amelia
Published: March 2009

Carbon nanohorns and multiwalled carbon nanotubes have been synthesized by DC arcdischarge
carried out at room pressure in air and Ar-enriched environment, by a specially designed
experimental device. The resulting nanostructured material, characterized by electron microscopy
and X-ray diffraction, shows different structures according to the condensation channels through
which the sublimated carbon atoms are re-condensed in the solid state. Multi-Walled Carbon Nano-
Tubes are mainly found in the hard crust formed at the cathode, while nano-horned particles can be
recovered from a cylindrical collector surrounding the discharge. Further material, rag-like shaped
and with an amorphous structure, can be collected in the reaction area. When the discharge occurs
under Ar atmosphere, a larger quantity of this latter phase is synthesized. This suggests that the
atmospheric oxygen could play an active role by burning the most reactive among the synthesized
phases, like amorphous carbon contributing so to an “in situ” purification of the raw material.
Optimization of Semimagnetic Semiconductor-Based Nanostructures for Spintronic Applications
Authors: Radovanović J. , Milanović V. , Ikonić Z. , Indjin D.
Published: March 2009

We have analyzed the spin-filtering effects of the electron current in asymmetric
ZnSe/Zn1-xMnxSe multilayer structures, under the influence of both an external magnetic field and a
bias voltage. In this type of semiconductor systems, conduction band electrons interact with 3d
electrons of the magnetic Mn2+ ions. Because of this sp-d exchange interaction, an external
magnetic field modulates the effective potential profile seen by spin-up and spin-down electrons,
giving rise to a large Zeeman effect. It is found that the degree of spin polarization changes
significantly when the electrical bias is switched from forward to reverse, thus the proposed
structure displays obvious behavior of spin-filter diode. This originates from the effective “lifting”
of the potential for spin-up electrons, which tunnel through actual potential barriers. Structural
parameters optimization, with the goal of maximizing the spin-filtering coefficient, was performed
by using simulated annealing algorithm. The described effect may be important for designing new
tunable spin-based multifunctional semiconductor devices.
Compaction of Anisotropic Granular Materials: Symmetry Effects
Authors: Budinski-Petković Lj. , Petković M. , Jakšić Z.M. , Vrhovac S.B.
Published: March 2009

We perform numerical simulation of a lattice model for the compaction of a granular
material based on the idea of reversible random sequential adsorption. Reversible random
sequential adsorption of objects of various shapes on a two−dimensional triangular lattice is studied
numerically by means of Monte Carlo simulations. The growth of the coverage ρ(t) above the
jamming limit to its steady−state value ρ∞ is described by a pattern ρ (t) = ρ∞ − ρEβ[−(t/τ)β],
where Eβ denotes the Mittag−Leffler function of order β ∈ (0, 1). For the first time, the parameter τ
is found to decay with the desorption probability P− according to a power law τ = A P−
−γ. Exponent
γ is the same for all shapes, γ = 1.29 ± 0.01, but parameter A depends only on the order of symmetry
axis of the shape. Finally, we present the possible relevance of the model to the compaction of
granular objects of various shapes.
Polymer Structure Prediction by Computer Simulation of Ziegler-Natta Polymerization Based on Charge Percolation Mechanism
Authors: Pilić B. , Stoiljković D. , Bakočević I. , Jovanović S. , Panić D. , Korugić-Karasz Lj.
Published: March 2009

Recently, a new charge percolation mechanism (CPM) of the Ziegler-Natta (ZN) polymerization of olefins by supported transition metal (Mt) complexes has been presented: a macromolecular chain is formed by polymerization of the monomer cluster (nM) adsorbed on the support (S) between two immobilized Mt ions, some in the higher (Mtn+1, i.e. acceptors) and the other in the lower (Mtn-1, i.e. donors) oxidation state: (Mtn-1...nM...Mtn+1)/S → (Mtn Mtn)/S + polymer. A special computer program «Lattice» has been developed to simulate olefin polymerization based on CPM using a Monte Carlo procedure. The effects of reaction conditions (Mt concentration, Mt/S ratio, sequence of chemical components addition and time) of ethylene and propylene polymerization by various Mt precursors (TiCl4/MgCl2, CrOx) and supports (MgCl2, SiO2) on molecular mass and molecular mass distribution can be predicted by simulation and confirmed by published experimental results.
Quantum Decoherence and Quantum-Holographic Information Processes: From Biomolecules to Biosystems
Authors: Raković D. , Dugić M. , Plavšić M.B. , Keković G. , Ćosić Irena , Davidović David
Published: March 2009

Our recently proposed quantum approach to biomolecular recognition processes is hereby
additionally supported by biomolecular Resonant Recognition Model and by quantum-chemical
theory of biomolecular non-radiative resonant transitions. Previously developed general quantumdecoherence
framework for biopolymer conformational changes in very selective ligandproteins/
target-receptors key/lock biomolecular recognition processes (with electron-conformational
coupling, giving rise to dynamical modification of many-electron energy-state hypersurface of the
cellular quantum-ensemble ligand-proteins/target-receptors biomolecular macroscopic quantum
system, with revealed possibility to consider cellular biomolecular recognition as a Hopfield-like
quantum-holographic associative neural network) is further extended from nonlocal macroscopicquantum
level of biological cell to nonlocal macroscopic-quantum level of biological organism,
based on long-range coherent microwave excitations (as supported by macroscopic quantum-like
microwave resonance therapy of the acupuncture system) - which might be of fundamental
importance in understanding of underlying macroscopic quantum (quantum-holographic Hopfieldlike)
control mechanisms of embryogenesis/ontogenesis and morphogenesis, and their backward
influence on the expression of genes.
Classical and Quantum Information Channels in Protein Chain
Authors: Koruga Dj. , Tomić A. , Ratkaj Z. , Matija L.
Published: March 2009

Investigation of the properties of peptide plane in protein chain from both classical and quantum approach is presented. We calculated interatomic force constants for peptide plane and hydrogen bonds between peptide planes in protein chain. On the basis of force constants, displacements of each atom in peptide plane, and time of action we found that the value of the peptide plane action is close to the Planck constant. This indicates that peptide plane from the energy viewpoint possesses synergetic classical/quantum properties. Consideration of peptide planes in protein chain from information viewpoint also shows that protein chain possesses classical and quantum properties. So, it appears that protein chain behaves as a triple dual system: (1) structural - amino acids and peptide planes, (2) energy - classical and quantum state, and (3) information - classical and quantum coding. Based on experimental facts of protein chain, we proposed from the structure-energy-information viewpoint its synergetic code system.
Magnetoexcitons in Type-II Self-Assembled Quantum Dots and Quantum-Dot Superlattices
Authors: Veljković Dj. , Tadić M. , Peeters F.M.
Published: March 2009

Exciton states in type-II InP/InGaP and GaSb/GaAs self-assembled quantum dots and
quantum-dot superlattices subject to a normal magnetic field are calculated. Strain is explicitly
taken into account in single particle models of the electronic structure, while an exact
diagonalization approach is adopted to compute the exciton states. Strain reverts type II band
alignment in InP quantum dots to type I, therefore no transitions between the lowest energy states of
different angular momenta are observed. On the other hand, strain increases the barrier for the
electron in the conduction band of GaSb/GaAs quantum dots, therefore the exciton, being
composed of electron and hole states of various angular momenta, may have a finite angular
momentum in the ground state. Consequently, the oscillator strength in the InP single quantum dot
and quantum-dot superlattice increases with the magnetic field, while the angular momentum
transitions between the bright and the dark exciton states in the GaSb system bring about decay of
the oscillator strength when the magnetic field exceeds a certain value.
Nonlinear Dynamics of Brewing Yeast Cell Growth in Alginate Micro-Beads
Authors: Pajić-Lijaković Iva , Nedović V. , Bugarski B.
Published: March 2009

The nonlinear dynamics of brewing yeast cell growth in porous Ca-alginate matrices is
considered experimentally and theoretically. The applications of alginate matrices include the
reduction of internal mass transfer resistance, minimized cell leakage and growth restriction due to
interactions between matrices and cell membranes comparatively to free cell culture conditions. The
effects of micro-bead diameters in the range 0.3-2.0 mm on yeast cell growth were investigated.
The stochastic mathematical model from the Langevin class is proposed for the interpretation of cell
growth, affected by four micro-processes: micro-environmental quality changes due to nutrient
diffusion into the micro-beads, cell leakage, repulsive interactions between boundary layers around
the cells themselves, which contribute to the dynamics of cell growth as a negative, nonlinear feedback
restriction and random kinetics effects. Such a model is used for the prediction of the optimal
diameter of micro-beads, which ensures maximal final cell concentration. The results of cell growth
in alginate matrices study have indicated an optimal diameter of 0.5-0.6 mm for micro-beads.
Immobilized cells in these beads were not restricted significantly by mass transfer of nutrients and
by cell leakage. The highest final cell concentration value indicated the largest feed-back restriction
quantified by the constitutive parameter b.
Ductile Fracture Prediction of Steam Pipeline Steel
Authors: Zrilić Misa , Rakin Marko , Sedmak Aleksandar , Aleksić R. , Cvijović Z. , Arsić Miodrag
Published: March 2009

Considering the conditions to which steels used for the manufacture of steam pipelines
are exposed, the micromechanism of their destruction in exploitation is exclusively the ductile one.
In order to make an estimation of the level of the damage that occurs in exploitation, in this paper a
combined experimental and numerical procedure has been developed based on micromechanical or
local approach to the fracture mechanics of metallic materials. After the analysis of the results
obtained for micromechanical criterion of failure for virgin steel and that used in the steam pipeline,
a proposal for prolongation of the working life of tested steel for steam pipelines until the next
overhaul is given.
Sorption of Ferric and Ferrous Ions on Silica
Authors: Milonjić S.K. , Čupić Smiljka D. , Čerović Lj.S.
Published: March 2009

The sorption of ferric and ferrous ions from aqueous solutions on the silica powder,
obtained from colloidal dispersion of silica (silica sol), was studied as a function of their
concentrations and solution pH. The amount of sorbed ferric and ferrous ions increases with
increasing final pH of the solution. The sorption isotherms are of high-affinity type. A sorption
mechanism of ferric and ferrous ions from aqueous solutions on silica is proposed.
Application of the Three-Dimensional Damage Percolation Model and X-Ray Tomography for Damage Evolution Prediction in Aluminium Alloys
Authors: Orlov O. , Maire Éric , Adrien Jérôme , Worswick Michael J. , Lloyd David J.
Published: March 2009

A three-dimensional damage percolation model, which captures the effect of
microstructural heterogeneity on damage evolution, has been developed to model damage initiation
and propagation in materials containing second phase particles. It considers the three phenomena
preceding ductile rupture of the material: void nucleation, growth, and coalescence. Threedimensional
X-ray tomography is used to obtain measured three-dimensional second phase particle
distributions in aluminum alloy sheet. Material damage evolution is studied within a tensile test
simulation and compared to measured damage from an in situ tensile test utilizing X-ray
tomography. Experimental and simulation results for material damage initiation and evolution are in
good agreement.
On the Origin of the Enhanced Creep Resistance in Underaged Al-Cu Based Alloys
Authors: Hutchinson Christopher R. , Cornall P. , Gouné M.
Published: March 2009

It has recently been observed that the creep resistance of Al-Cu based precipitation hardened alloys may be enhanced through use of the underaged temper. We have treated this problem theoretically by considering the motion of a dislocation through a precipitation hardened structure and discuss the physical origin of the enhanced creep resistance in the underaged condition. The variation in expected creep resistance as a function of aging treatment is calculated and the possible generality of the experimental observations is considered.
Influence of Spatial Grain Orientation Distribution on Sheet Metal Necking
Authors: Wu Pei Dong , Lloyd David J.
Published: March 2009

Necking under in-plane plane strain tension along the transverse direction (TD) is
numerically simulated for two sheets: one with very high Cube (HC) and the other with low Cube
(LC). To do so, the EBSD measurement is performed in the TD-ND (normal direction) section for the
sheets. The EBSD map (grain orientations and their spatial distributions) is directly implemented into
the crystal plasticity based finite element code. More specifically, the measured orientations are
assigned to elements in the mesh according to their positions. The values of the material parameters in
the crystal plasticity model are determined by curve-fitting numerical simulations of uniaxial tension in
the rolling direction (RD) to corresponding experimental data. The effect of spatial grain orientation
distribution on necking is emphasized. It is found that both the global averaged texture and its spatial
distribution are important to the onset of necking. The predicted results are in good agreement with
experimental observations.
Prediction of Long Term Stress Rupture Data for 2124
Authors: Wilshire Brian , Burt H. , Lavery N.P.
Published: March 2009

The standard power law approaches widely used to describe creep and creep fracture behavior have not led to theories capable of predicting long-term data. Similarly, traditional parametric methods for property rationalization also have limited predictive capabilities. In contrast, quantifying the shapes of short-term creep curves using the q methodology introduces several physically-meaningful procedures for creep data rationalization and prediction, which allow straightforward estimation of the 100,000 hour stress rupture values for the aluminum alloy, 2124.
Role of Residual Stresses on Fatigue Crack Propagation of FSW 6056-T78 Aluminium Joints under Various Technologies
Authors: Lafly Anne Laure , Dalle Donne Claudio , Biallas Gerhard , Alléhaux Delphine , Marie François
Published: March 2009

Residual stress fields may be rather frequently observed in several mechanical and structural parts, usually as a result of the manufacturing and joining techniques adopted. Their effects on material performances can be quite different, going from highly detrimental to beneficial, according to their distribution and to the acting material damage mechanisms (fatigue fracture, brittle or ductile failure, corrosion,…). Residual stresses are produced in welded structures by thermal expansion, plastic deformation and shrinkage during cooling. The amount of constraints determines the level of residual stress. Friction Stir Welding (FSW) is a quite new joining technique particularly for aluminium alloys difficult to fusion weld. Since conventional FSW showed its limits, Bobbin Tool technology has been developed. These both types of welds produce low-distortion of high quality (even no postweld distortion) and relevant residual stresses. The residual stresses of the aerospace material 6056-T78 aluminium alloy Friction Stir Welded sheets have been analysed on various tempers in accordance with these two different technologies. The effects have been investigated parallel and orthogonal to the weld direction. By means of local or global heat treatments, the residual stress state can be generally reduced or changed from tensile to compressive stresses on surface; in that way, the different heat aging conditions T78 as-welded and post-welded are checked in this study. This paper presents the method used, the measurements of this fatigue damage and their consequences on the fatigue life performance of structural materials.
Investigation on Strength and Corrosion Behaviour of Friction Stir Welded Similar and Dissimilar Aluminium Alloys
Authors: Braun Reinhold , Alfaro Mercado Ulises , Biallas Gerhard
Published: March 2009

Sheet materials of the alloys 6056 and 2024A were joined using the friction stir welding
technique. Similar and dissimilar butt welds were produced. Strength and corrosion behaviour of
the joints were investigated in different heat treatment conditions. Hardness profiles across the weld
revealed minima in the heat affected zones, being very pronounced at the advancing side of the
joints. The hardness of the nugget zone increased after post-weld artificial aging. Strengths of postweld
heat treated similar 6056 and dissimilar 2024A/6056 joints approached 90 and 85 %,
respectively, of the ultimate tensile strength of 6056-T7X. As found by electrochemical
measurements, alloy 2024A-T3 exhibited the most noble corrosion potential and artificially aged
alloy 6056 the most active potential. Besides microstructural changes caused by the welding
process, galvanic coupling affected the corrosion behaviour of friction stir welds, in particular with
joints of dissimilar aluminium alloys, as indicated by accelerated corrosion of alloy 6056 in the
nugget region. Intensified corrosion attack was also observed in the heat affected zones.
Effect of Welding Parameters on Mechanical and Microstructural Properties of Dissimilar AA6082-AA2024 Joints Produced by Friction Stir Welding
Authors: Cavaliere Pasquale , Squillace Antonio
Published: March 2009

The effect of processing parameters on mechanical and microstructural properties of dissimilar
AA6082-AA2024 joints produced by Friction Stir Welding was analysed in the present study. Different
samples were produced by employing a fixed rotating speeds of 1600 RPM and by using the advancing
speeds of the tool of 80 and 115 mm/min. All the welds were produced in direction perpendicular to the
rolling one for both the alloys and by changing, for all the processing conditions, the alloy positioned on the
advancing side of the tool. The mechanical properties of the joints were evaluated by room temperature
tensile tests. Fatigue tests on the welds were carried out by using a resonant electro-mechanical testing
machine under constant loading control up to 250 Hz sine wave loading. The fatigue tests were conducted
in the axial total stress-amplitude control mode with R=smin/smax=0.1. The microstructural evolution of the
material was analysed by optical observations of the welds cross sections and SEM observations of the
fracture surfaces.
Microstructure Refinement of Al-Si Alloy Using Compressive Torsion Processing
Authors: Kume Yuji , Kobashi Makoto , Kanetake Naoyuki
Published: March 2009

A Compressive Torsion Processing (CTP) is a unique severe plastic deformation process which can easily apply very large strain without shape change to a work piece. Hypereutectic Al-Si alloys have good properties such as low thermal expansion and high wear resistance. It is important for the alloys to control the size of second phase particles (primary and eutectic silicon, intermetallic compounds) as well as grain size of aluminum matrix. In the present work, the CTP was applied to hypereutectic Al-Si alloy (AA390) to investigate the possibility of microstructure refinement of the alloy and the mechanical property of processed alloy was also investigated by tensile test.
Microstructural Characterization and Fatigue Properties of 2195 Al-Li Alloy
Authors: Chaturvedi Mahesh C. , Chen Dao Lun
Published: March 2009

The effect of welding, heat-affected zone (HAZ) simulation, and specimen orientation on
the microstructure and fatigue properties of 2195 Al-Li alloy was studied. HAZ simulation and
GTA welding with a 4043 filler alloy resulted in a significant change in the microstructure. In the
HAZ the primary strengthening phase, T1 (Al2CuLi), in the base alloy in T8 temper was replaced by
TB (Al7Cu4Li) phase and voids/microcracks, and the fusion zone (FZ) consisted of T (AlLiSi) phase
particles in the matrix, which consisted mainly of the filler alloy. The yield strength and fatigue
threshold of the 2195-T8 alloy were observed to be dependent upon the specimen orientation. The
HAZ simulation and welding led to a reduction in the tensile properties and fatigue strength. While
the post-weld heat treatment resulted in the re-precipitation of T1 phase in the HAZ, but no increase
in the fatigue strength was observed due to the presence of microcracks. Fatigue crack initiation
was observed to occur at the surface in the base alloy in T8 temper, and at the internal defects after
HAZ simulation and welding. Fatigue crack propagation exhibited characteristic striations in the
T8 alloy, and brittle cleavage-like feature after HAZ simulation and welding.
Excess Free Volume of High Angle Grain Boundaries in Aluminium
Authors: Ivanov V.A. , Molodov Dmitri A. , Shvindlerman Lasar S. , Gottstein Günter , Kolesnikov D. , Łojkowski Witold
Published: March 2009

A new method is introduced to determine the absolute value of the boundary excess free volume. Along with the boundary energy the excess free volume belongs to the major thermodynamic properties of grain boundaries. The method utilizes the dependence of the contact angle at triple junctions of grain boundaries in Al-tricrystals on hydrostatic pressure. We investigated <111> tilt boundaries in the pressure range up to 14 kbar. In particular, for a 40° <111> tilt boundary with 2° twist component the boundary free volume was found to be equal to 5.03×10-11 m3/m2.
Modelling of Microstructure and Texture and the Resulting Properties during the Thermo-Mechanical Processing of Aluminium Sheets
Authors: Engler Olaf
Published: March 2009

In order to predict the mechanical properties of Al sheet products, the evolution of microstructure and crystallographic texture along the process chain must be tracked. During the thermo-mechanical processing in commercial production lines the material experiences a complex history of temperature, time and strain paths, which results in alternating cycles of deformation and recrystallization with the associated changes in texture and microstructure. In the present paper the texture evolution of AA 3104 can body stock is modelled. In particular, the earing behaviour at final gauge is linked to the decisive steps of deformation and recrystallization along the thermomechanical process chain. For this purpose, the textures predicted by a comprehensive throughprocess model of the texture evolution during the thermo-mechanical production of Al sheet are input into a polycrystal-plasticity approach to simulate earing of the final gauge sheets.
The Influence of Fluid Flow on Intermetallic Phases in Al-Cast Alloys
Authors: Steinbach Sonja , Euskirchen Natasja , Witusiewicz Victor T. , Sturz Laszlo , Ratke Lorenz
Published: March 2009

Technical Al-Si alloys always contain sufficient amounts of Fe and Mn, especially alloys
made from scrap. During casting, Fe-containing intermetallics, such as Al-Fe, Al-Fe-Si and Al-Fe-
Mn-Si phases, are formed between the aluminum dendrites. Fe and Mn-rich intermetallic phases are
well known to be strongly influential on mechanical properties in Al-Si alloys. In the present work
the influence of controlled fluid flow conditions on the morphology and spatial arrangement on
intermetallic phases in cast Al-Si alloys is characterized. A binary Al-7wt.%Si and a ternary Al-
7wt.%Si-1wt.%Fe alloy was solidified under and without the influence of a rotating magnetic field
(3mT at 50Hz) over a range of solidification velocities (0.015- 0.18mm/s) at a constant temperature
gradient G of 3K/mm. The scientific results reached so far indicate a strong influence of the
electromagnetic stirring on the primary dendrite and secondary dendrite arm spacings.
Modeling the Role of Microstructure on Shear Instability with Reference to the Formability of Automotive Aluminium Alloys
Authors: Wilkinson David S. , Duan Xin Jian , Kang Ji Dong , Jain Mukesh K. , Embury J. David
Published: March 2009

This paper addresses the effect of microstructure on the formability of aluminium alloys
of interest for automotive sheet applications. The bulk of this work has been on the alloy AA5754 –
both conventional DC cast alloys and continuous cast alloys made by twin belt casting. It is known
that alloys such as these contain Fe as a tramp impurity which results in Fe-based intermetallic
particles distributed through microstructure as isolated particles and in stringers aligned along the
rolling direction. It is thought that these particles are the cause, both of the reduced ductility that is
observed as the Fe level rises, and the relatively poor formability of strip cast alloys, as compared
with those made by DC cast. Conventional wisdom suggests that the reduction of ductility is due to
the effect of particles as nucleating sites for damage. However, most studies show that these
materials are resistant to damage until just before fracture. We now believe that effect is actually
related to the development of shear bands in these materials. We present experimental data which
supports this conclusion. We then show how the FE models we have developed demonstrate the
role of shear instability on fracture and the role played by hard particles. We show how a unit cell
approach can be used to incorporate the effect of particle density and morphology on shear
localization in a way that includes statistical variability due to microstructural heterogeneity. This
leads to a set of constitutive equations in which the parameters are distributed from one region to
another. These are then fed into a macroscopic FE model at the level of the specimen or the
component in order to determine the effect of microstructural variability on shear instability and
ductility.
Semi-Solid Slurry Preparation without Additional Stirring, Cup-Cast Method
Authors: Pahlevani Farshid , Yaokawa J. , Anzai Koichi
Published: March 2009

The needs for high-strength and lightweight structural materials have increased in
automotive and aerospace structural applications. Semi-solid processed light alloys have satisfied
these requirements because of processing advantages and significant weight reduction.
Conventional semi-solid casting methods have got a wide variety of problems and difficulties. The
cup-cast method that has been just developed is a novel process that make semi-solid casting as
easy as pouring the water from a pitcher into a drinking glass, and avoid all the problem and
difficulties of other semi-solid casting processes. Cup cast method is based on the heat and mass
transfer and spherical equiaxed particles with controlling the nucleation and growth of solid
particles were produced. In this study the different factor of this method was optimized by
micro-structural investigation on the Al-A356 alloy. Pouring height and temperature, duration of
pouring, and cup coating had played important roles in this method.