bluuebunny/crossref_metadata_2025 huggingface dataset:
Combining Equal-Channel Angular Extrusion (ECAE) and Heat Treatment for Achieving High Strength and Moderate Ductility in an Al-Cu Alloy
Authors: Hockauf Matthias , Meyer Lothar W. , Krüger Lutz
Published: March 2009

The effect of equal-channel angular extrusion (ECAE) on mechanical properties of an
AA2017 produced by powder metallurgy is investigated. Special attention is given to the influence
of heat treatment, processing temperature and backpressure on the workability for achieving high
strength and moderate ductility. This is of special interest, since it is often reported that Al-Cu
alloys have low ductility and therefore are prone to cracking during severe plastic deformation. It is
shown that ECAE at high temperatures (>220°C) does not necessitate backpressure to ensure
homogeneous deformation but leads to a significant sacrifice in strength due to in-situ precipitation.
Thus, most of the extrusions are done at considerably low temperatures. Performing room
temperature-extrusion is most effective in achieving high strengths but also requires high
backpressures. Due to severe strain hardening during processing, the strength increase is combined
with a reduction in ductility. Recently it was reported that a post-ECAE aging of pre-ECAE solution
treated material is effective in enhancing the ductility of aluminium alloys. This approach was
successfully transferred to the current alloy. A high-temperature, short-time aging after only one
extrusion, for example, doubles the failure strain to a value of ~13%. Compared to the naturally
aged condition with coarse grains that serves as reference (T4), an increase of 15 % in yield stress
(YS) was obtained while retaining the ultimate tensile stress (UTS). Another effective approach is
the combination of a pre-ECAE solution treatment with subsequent under-aging prior to ECAE. It is
shown that performing ECAE at medium temperatures (160-180°C) enables a better workability and
additionally gives higher strengths and better ductility compared to the processing in the water
quenched condition. A remarkable YS of 530 MPa and an UTS of 580 MPa combined with a
moderate failure strain of 11.6 % were achieved.
The Effect of Strain on the Development of Ultra-Fine Grain Structure in 7055 Aluminium Alloy Processed by Equal Channel Angular Extrusion
Authors: Nikulin Ilya , Motohashi Yoshinobu , Kaibyshev Rustam
Published: March 2009

Grain refinement taking place in a commercial 7055 aluminum alloy under equal channel
angular extrusion at a temperature of 250°C, was examined. The material was deformed up to a
total strain, ε, of ~12. At ε≈1, the development of subgrain bands was found. Upon further straining
the average misorientation of deformation-induced boundaries increases; low-angle grain
boundaries (LAGBs) gradually convert into true high-angle grain boundaries (≥15°) (HAGBs). At
ε≈4, a structure consisting of boundaries with low and high angle misorientations was observed. At
ε≈12, a structure with an average grain size of ∼0.7 µm was formed. This size is roughly similar to
that for subgrains developed at preceding strains. It was shown that the formation of
submicrocrystalline grains occurs through continuous dynamic recrystallization both along initial
boundaries and within interiors of original grains as well.
Grain Refinement in a Commercial Al-Mg-Sc-Zr Alloy during Hot ECAP
Authors: Sukhopar Olga , Sitdikov Oleg , Gottstein Günter , Kaibyshev Rustam
Published: March 2009

The microstructure evolution of an as-cast commercial Al-Mg-Sc-Zr alloy during Equal-
Channel Angular Pressing (ECAP) at 325°C was investigated. In the early stages of deformation
strain induced boundaries were created within the initial coarse grains and constitute the
deformation bands. Repeated ECAP led to an increase of the number and misorientation of
deformation bands. Further straining up to e~8 resulted in the formation of a new fine-grained
structure with an average crystallite size of 1.2 /m. It is concluded that the progressive increase of
the misorientation of deformation induced boundaries is the main mechanism of structure formation
under high temperature ECAP.
Nanocrystalline Titanium Rods Processed by Hydrostatic Extrusion
Authors: Topolski Krzysztof , Garbacz Halina , Kurzydlowski Krzysztof Jan
Published: March 2009

The potential application range of coarse-grained commercial purity titanium is
limited by its low mechanical properties. A reduction of the grain size of titanium leads to
a significant increase in its strength and hardness. This paper is concerned with application
of hydrostatic extrusion (HE) for fabrication nano-grained titanium.
In the present study titanium rods were subjected to hydrostatic extrusion with the aim
to reduce the grain size to the nano-metric scale and thereby improve the mechanical
properties. The obtained material can be an equivalent and compete with the commonly used
Ti6Al4V alloy. The results were compared with those other SPD techniques reported in the
literature and refered to Hall-Petch relationship.
Structure and Mechanical Properties of Severely Deformed Cu-Cr-Zr Alloys Produced by Accumulative Roll-Bonding Process
Authors: Kitagawa Kazuo , Akita T. , Kita K. , Gotoh Masahide , Takata Naoki , Tsuji Nobuhiro
Published: March 2009

Aging behavior and mechanical properties of ultra fine grained Cu-Cr-Zr alloy sheet
produced by accumulative roll bonding (ARB) process were investigated. A Cu-0.85Cr-0.07Zr (in
mass%) alloy was solution treated and then cold-rolled at ambient temperature in the sheet of 1 mm
thick. The sheets were heavily deformed by ARB process at ambient temperature up to 5
cycles. The grain size was reduced down to 210 nm and the fraction of high angle grain boundaries
(HAGB’s) in the specimen after ARB process was 63%. The proof stress ( σ 0.2) and elongation
were 540 MPa and 10%, respectively. Due to the aging treatment, a little grain growth took place
(240 nm) and the fraction of HAGB’s was increased to 67%. The proof stress and elongation of
the aged one increased to 605 MPa and 15%, respectively. It was noteworthy that the electrical
conductivity remarkably increased from 35% to 79%IACS by the aging treatment. It was
concluded that the aging treatment after ARB process enhanced not only the mechanical properties
but also the electrical conductivity in the Cu-Cr-Zr alloys.
Long-Length Ultrafine-Grained Titanium Rods Produced by ECAP-Conform
Authors: Raab Georgy I. , Valiev Ruslan , Gunderov Dmitriy , Lowe Terry C. , Misra Amit , Zhu Yun Tian
Published: March 2009

A new technique of continuous severe plastic deformation (SPD)-processing, i.e. ECAP (equal
channel angular pressing)-Conform is applied for the first time to produce long-length rods of
commercial purity Ti with ultrafine-grained structure. The paper reports on the results of
investigation of the microstructure and mechanical properties of Ti rods processed by ECAPConform
and the following wire drawing.
Effect of Trace Impurities on High-Cycle Fatigue Damage of Ultrafine Grained Copper Processed by Equal Channel Angular Pressing
Authors: Goto Masahiro , Teshima N. , Han S.Z. , Yakushiji T. , Kim Sang Shik
Published: March 2009

In order to study the effect of trace impurities on high-cycle fatigue damage of ultrafine
grained (UFG) copper, fatigue tests were carried out for two samples: oxygen-free copper (OFC,
99.99 wt% Cu) and deoxidized low-phosphorous copper (DLP, 99.95 wt% Cu). After the processing
by equal channel angular pressing (ECAP) using eight passes, equiaxed grains with an average size
of 250 nm were formed for both the samples. Fatigue strength of UFG copper was enhanced by the
impurities. The formation behavior of surface damage and the change in surface hardness was
monitored. A close relationship was observed between the change in hardness and the formation
behavior of surface damage. The physical background of the effect of trace impurities on the fatigue
damage was discussed from the viewpoints of surface damage formation behavior.
Annealing Response of Al-0.22Sc-0.13Zr Alloy Processed by Accumulative Roll Bonding
Authors: Homola Petr , Slámová Margarita , Očenášek Vladivoj , Uhlíř J. , Cieslar Miroslav
Published: March 2009

Ultra-fine grained (UFG) materials can be produced by several techniques involving
severe plastic deformation (SPD). Accumulative Roll Bonding (ARB) is one of the SPD methods
that enable the production of large amounts of UFG sheets. UFG sheets were prepared by up to six
cycles of ARB at ambient temperature from an Al-0.22Sc-0.13Zr alloy in two states: a non-agehardened
and a peak-aged. The effect of Al3(Sc1-xZrx) precipitates on the thermal stability of the
UFG structures produced by ARB was investigated by isochronal annealing at temperatures between
200 and 550 °C. Additionally, the non-age-hardened ARB material was peak-aged prior to
annealing and annealed together with both as-ARB-processed materials. The changes of
microstructure and hardness due to annealing were studied. Annealing at 300 °C induces an
additional strengthening in both non-pre-aged ARB materials that may be ascribed to precipitation
and growth of coherent Al3(Sc1-xZrx) particles. This result suggests that the hardness decrease
introduced by ARB in the peak-aged specimen is due to dissolution of precipitates during
deformation. The annealing response of the materials above 300 °C does not depend on their
thermal pre-treatment. However, the finely dispersed Al3(Sc1-xZrx) precipitates stabilise the refined
deformed microstructure suitable for superplastic forming up to relatively high temperatures.
La Fe Victoriosa Casting Features
Authors: Gallardo José M. , Cuevas Francicso Gomez , Cintas Físico Jesus , Martos Juan Manuel Montes
Published: March 2009

As the first step in the restoration process of a Renaissance bronze statue, a
comprehensive study of the metallic product was carried out. This paper reports metallographic
features and their possible relation to the casting process. Tensile properties are also discussed as
they depend on porosity and lead content, what can be useful in the restoration process.
Phase Transitions in the BIMEVOX Solid Solutions with Me = Ga, Zr
Authors: Murasheva V.V. , Fortalnova Elena A. , Politova Ekaterina D. , Safronenko Marina G. , Stefanovich Sergei Yu. , Venskovskii Nikolay U.
Published: March 2009

The polymorph phase stability ranges have been studied for the Bi4V2-xMexO11-y solid
solutions with Me = Ga and Zr at room temperature. The formation of orthorhombic α- (x = 0.0 and
0.05) and β-phases (x = 0.1, 0.15) and tetragonal phase (0.2 ≤ x ≤ 0.3) has been revealed in
BIGAVOX solid solutions. In BIZRVOX solid solutions, α-phase exists at x ≤ 0.05, while β-phase
exists at 0.1 ≤ x ≤ 0.3. The second order phase transitions at ~ 308°C (BIGAVOX) and ~ 270°C
(BIZRVOX) have been revealed for solid solutions with x = 0.05 using the SHG and DSC methods.
In both systems, the β↔γ-phase transition temperatures have been found to decrease with
increasing x.
The Use of Sodium Silicate to Improve Wetting of Tungsten Carbide Powder with Ductile Iron
Authors: Lourenço Nuno , Santos Henrique , Sá Carlos
Published: March 2009

A tungsten carbide insert is produced during ductile iron foundry practice to increase the
surface hardness of the material. The insert is ensured with the help of a critical quantity of a binder,
around 3 weight percent of sodium silicate, previously mixed with the tungsten carbide powder. The
binder is verified to form a film around the tungsten carbide particles and bridges amongst these
enveloped particles; these films and bridges are replaced by the ductile iron melt during the molding
cavity filling. After solidification, a sound inserted layer is formed, composed of tungsten carbide
particles in a tungsten enriched cast iron matrix. In the absence of the binder addition to the
tungsten carbide powder no inserted layer is produced. The surface hardness of the inserted test
pieces is close to 500VHN/4.9N and the respective thickness is around 2.5 mm. The
characterization of the effect of the sodium silicate in the mixture has been the main purpose of this
work
Mixed Si/Ge Apatite-Type Phase Produced by Mechanical Alloying
Authors: Vieira Milena M. , de Oliveira Joao C. , Cavaleiro Albano , Trindade Bruno
Published: March 2009

The aim of the present work is to study the influence of the partial substitution of Si by
Ge on the formation of the apatite-type La9.33Si2Ge4O26 phase by mechanical alloying and
subsequent annealing. Powders of La2O3, GeO2 and SiO2 were dry milled in a planetary ball milling
at increasing rotation speeds of 150, 250 and 350 rpm and milling times up to 50 h. The resulting
mixtures were subsequently annealed at increasing temperatures up to 1100 °C. Single phase
apatite-like La9.33Si2Ge4O26 was obtained during mechanical alloying at high rotation speed. The
higher the rotation speed the lower was the time required for the lanthanum germanosilicate phase
formation. For the samples in which complete reaction between initial phases did not occur during
milling, La9.33Si2Ge4O26 was always obtained during the annealing process. The more severe was
the mechanical alloying process the lower was the annealing temperature required for the apatite
phase formation. The formation of apatite phase during mechanical alloying did not provoke
significant changes in densification behavior of the milled samples. The addition of GeO2 as raw
material promotes a faster formation of the apatite phase as compared to the results obtained using
only La2O3 and SiO2.
Studies on some Glasses and Glass-Ceramics for Various Applications Including Seals
Authors: Kothiyal Govind P. , Anathanarayanan Arvind , Tiwari Babita , Goswami Madhumita , Shrikhande V.K.
Published: March 2009

Glass and glass-ceramics (GCs) find wide applications in various disciplines of science
and technology including sealing, vacuum, energy devices because of their desired thermomechanical,
electrical, optical properties and chemical durability. We shall report here some recent
studies carried out on thermo-physical and structural properties of TiO2 doped sodium aluminophosphate
(NATP) glasses, interface studies on Li2O-ZnO-SiO2-P2O5-B2O3-Na2O (LZS) glassceramics
for matched type of seal with Cu metal and machinability of magnesium aluminium
silicate (MAS) glass-ceramics suitable for high voltage and ultra high vacuum applications.
Structural studies have been carried out using XRD, FTIR, Raman and scanning electron
microscopy(SEM). Thermo-physical measurements carried out on NATP glasses have been
discussed in the light of structural properties.
Preparation of Superconducting Powders and Thick Films
Authors: Altenburg Horst , Plewa Julian
Published: March 2009

In this review a small overview is given about methods of powder preparation and thick
films tested in the field of High-Temperature-SuperConductors (HTSC). The first and very important
step on the way to applications consists generally in the preparation of an adequate powder,
alternatively prepared by the common ceramic way or tailor made by wet chemistry. Following, the
preparation of thick films are discussed, mostly made by low cost processes in contrast to the expensive
manufacturing of thick films.
Evolution of Magnetism in CaO-SiO2-P2O5-Na2O-Fe2O3 Bioglass Ceramics
Authors: Singh Rajendra Kumar , Perumal A. , Kothiyal Govind P. , Srinivasan A.
Published: March 2009

We report the evolution of magnetism in bioglass ceramics 41CaO.(52-x)SiO2.4P2O5.
xFe2O3.3Na2O (2 ≤ x ≤ 10 mole % Fe2O3) prepared by melt quenching technique followed by heat
treatment at 1050 oC. The structural investigation revealed the presence of magnetite phase in the
heat treated samples with x ≥ 2 mole % Fe2O3. Room temperature magnetic measurements showed
a very weak ferrimagnetic behaviour for the sample with x = 2 mole % of Fe2O3. Samples with x >
2 mole % of Fe2O3 exhibited magnetic behavior similar to soft magnetic materials with low
coercivity. The evolution of magnetic properties in these samples as a function of Fe2O3 molar
concentration is correlated with the amount of magnetite phase present in them.
On the Dispersion of Carbon Nanofibre-Based Suspensions in Simple Shear: An Experimental Study
Authors: Leer Carla , van Hattum Ferrie W.J. , Carneiro Olga S. , Lanceros-Méndez Senentxu
Published: March 2009

The effect of different dispersion states on the rheological and AC conductivity properties
of carbon nanofibre/epoxy suspensions was investigated. Both rheological and electrical properties
revealed to be good indicators of the fillers’ dispersion state, as confirmed by optical microscopy. It
was shown that imposing a low shear deformation to poorly dispersed suspensions leads to
agglomerate rearrangement resulting in a worse dispersion quality and, consequently, lower
electrical conductivity. On the other hand, the imposition of a high shear deformation improves the
original dispersion, resulting in better electrical conductivity. Rheological observations confirm the
trends observed.
Actuator Capabilities of Piezoelectric Devices Embedded in Composite Laminate
Authors: Marques M.A. , Monteiro J. , Ramos Carlos A. , Vaz M.A. , Marques António Torres
Published: March 2009

In this work the actuator performance of a ceramic piezoelectric device is studied. Its
ability of deforming a Carbon Fiber Reinforced Plastic (CFRP) laminate is measured in the
absence/presence of mechanical constraints. Deformation and bending of the CFRP laminate is
obtained when a voltage is applied to the piezoelectric device. This deformation was assessed using
ESPI technique and a very good agreement with the expected values for the unconstrained case was
observed. When completely embedded a reduction of 86% in the piezoelectric response is expected.
Finite Element Analysis confirmed the obtained experimental data and a very good linearity in the
response was observed.
Histometric Analysis of Immediate Implantation and Immediate Loading of CMP and RBM Implants after Tooth Extraction in Dogs
Authors: Kim Yong Min , Kim Su Gwan , Lim Sung Chul
Published: March 2009

This study analyzed immediate implantation and immediate loading of chemical
mechanical polished (CMP) and resorbable blast media (RBM) SSIII OSSTEM dental implants
histometrically. The 1st, 2nd, 3rd, and 4th mandibular premolars were extracted from five adult
dogs. Immediate implantation was performed in the fresh extraction sockets. Each dog received two
types of implant: CMP and RBM. The first premolar was submerged, whereas the second, third, and
fourth were not submerged. The implants were splinted using acrylic resin and subjected to
immediate loading. After 4 months, X-rays were taken and analyzed. The animals were euthanized
and processed histologically to obtain non-decalcified sections. Longitudinal ground sections of
each implant were made, and histometry was analyzed under light microscopy. No significant
difference was found between the control and experimental groups based on immediate loading
(p > 0.05) and implant surface (p > 0.05). The implant survival rate and implant-to-bone contact rate
after immediate loading were similar to those of submerged implants. The CMP and RBM dental
implants did not differ in terms of implant survival rate and implant-to-bone contact rate.
Structural and Magnetic Properties of Nanogranular BaTiO3-CoFe2O4 Thin Films Deposited by Laser Ablation on Si/Pt Substrates
Authors: Barbosa J.G. , Almeida Bernardo G. , Araújo João P. , Sousa João Bessa , Mendes Jorge A.
Published: March 2009

Thin film nanocomposites of cobalt ferrite (CoFe2O4) dispersed in barium titanate
(BaTiO3) matrix, have been deposited with different cobalt ferrite concentrations (from 20% to 70%
CoFe2O4), as well as pure barium titanate and cobalt ferrite thin films (end members). The films
were prepared by pulsed laser ablation on platinum covered Si(001) substrates. The films structure
was studied by X-ray diffraction and their surface was examined by scanning electron microscopy
(SEM). The magnetic properties were measured in a SQUID magnetometer. The results show that
the deposited films are polycrystalline with a slight (111) barium titanate phase orientation and
(311) CoFe2O4 phase orientation. The grain sizes measured from the X-ray diffraction peak widths,
for both phases, are in the range 40nm to 100nm. However, as the concentration of the cobalt ferrite
increases, the grain size of the BaTiO3 phase decreases, from 100nm to 30nm, up to 40% CoFe2O4
concentration beyond which the BaTiO3 grain size has an approximately constant value near 30nm.
On the other hand the cobalt ferrite grain size does not show a clear trend with increasing cobalt
ferrite concentration, fluctuating in the range 20nm to 30nm. The magnetic measurements show an
increase of the magnetic moment from the low concentration region where the magnetic grains are
more isolated and their magnetic interaction is small, towards the bulk value at higher CoFe2O4
concentrations. Also, a strong reduction of the magnetization with increasing temperature was
observed, due to the corresponding decrease of the magnetocristalline anisotropy of the cobalt
ferrite.
Incorporation of Ga in CIGS Absorber Layers Formed by RF-Magnetron Sputtering in Se Vapours
Authors: Salomé Pedro M.P. , da Cunha António F.
Published: March 2009

Cu(In,Ga)Se2 (CIGS) thin film semiconductors are among the most attractive materials
for thin film solar cell applications. Conversion efficiency exceeding 19% has been achieved for
CIGS absorber layers deposited by three-stage co-evaporation technique. From a technological
point of view the sputtering deposition process is more attractive than thermal co-evaporation,
however, solar cell parameters obtained so far are worse. The highest efficiency value reported for
co-sputtered CIS thin films is less than 8% and there is no data found for CIGS layers produced by
a similar technique. We have developed a hybrid RF-magnetron sputtering/evaporation method for
the deposition of the CIGS absorber layer. In this method Cu and In are sequentially sputtered from
metallic targets in the presence of Se vapour. Ga depth profiling leads to a band gap grading which
is known to play an important role in cell performance. Here, we report the results of our work on
three different ways of Ga incorporation into the CIGS thin films. They consisted of sputtering from
In-GaSe, Cu-GaSe composite targets and Ga evaporation. The Ga content and distribution across
the layer thickness was investigated by AES measurements. The CIGS formation kinetics, structural
and compositional studies were performed by SEM, XRD and AES measurements.
Tribological Behaviour of an A355 Steel Pipe Welding
Authors: García Ana , Varela Angel , Montero J. , Mier José Luís , Zaragoza S. , Barbadillo Fernando
Published: March 2009

This work studies the behaviour of welding joints under abrasive wear in A355 Gr. P11
steel pipes carrying liquids at high temperatures. Various welding processes were tested on different
joints in an effort to choose the one that gave the best wear response. For this purpose, a pin-on-disk
tribometer was used at 200°C to simulate the service conditions of the pipes.
The tests were carried out by pressing a hard chromium-plated steel pin, with a diameter of 4 mm
and hardness of about 775 HV, on steel specimens in order to measure their mass loss and friction
coefficient in the three welding zones: base metal (BM), heat affected zone (HAZ) and weld bead
(WB). The tests conditions were 10 N of load, 200 rpm of rotation velocity and a radius of 3 mm. In
addition, metallographic studies and hardness measurements of the three welding zones were done
to complete this work.
Microstructure Interpretation of Copper and Bronze Archaeological Artefacts from Portugal
Authors: Silva Rui Jorge C. , Figueiredo E. , Araújo M.F. , Pereira Filipa , Braz Fernandes Francisco Manuel
Published: March 2009

In the present paper, a selection of micrographs showing some typical microstructures
and corrosion layers developed in copper and bronze alloys from different archaeological contexts
will be discussed. Metallurgic interpretation of the microstructures observed, based in the proper
binary equilibrium phase diagrams is presented. Micro-EDXRF and SEM-EDS analysis were
carried out to assess the alloy composition and to contribute to the understanding of the corrosion
processes occurred during the long periods of burial of the archaeological metals. Examples of
surface decuprification, strong intergranular corrosion, cuprite under green corrosion layers and
copper redeposition indicate particular corrosion processes. The presence of copper oxides,
sulphides inclusions, lead globules and porosities is also documented.
A-TIG Welding of a Stainless Steel
Authors: Loureiro Altino , Rodrigues A.
Published: March 2009

The aim of this research is the development of activating fluxes to improve weld bead
geometry and increase weld penetration depth in austenitic stainless steels. The effect on bead
geometry of two home-made fluxes, composed of titanium and aluminium oxides, was studied, in
combination with two shielding gases, respectively Argon and an Argon/Helium mixture. A
significant increase in penetration was obtained in welds done with the Ti based activating flux
across the whole range of welding currents for both shielding gases, which was not the case for
welds performed with the Al based flux. A decrease in δ-ferrite content in the weld metal with
increasing current was observed only in welds done with the Ti based flux.
Evaluation of Corrosion Protection of Sol-Gel Coatings on AZ31B Magnesium Alloy
Authors: Galio Alexandre Ferreira , Lamaka Sviatlana V. , Zheludkevich Mikhail L. , Dick L.F. , Müller Iduvirges Lourdes , Ferreira Mário G.S.
Published: March 2009

Magnesium is one of the lightest metals and magnesium alloys have good strength to
weight ratio making them very attractive for many particular applications [1]. The main drawback
of magnesium alloys is their high corrosion susceptibility. Improving the corrosion protection by
deposition of thin hybrid films can expand the areas of applications of relatively cheap magnesium
alloys. This work aims at investigation of new anticorrosion coating systems for magnesium alloy
AZ31B using hybrid sol-gel films. The sol-gels were prepared by copolymerization of 3-
glycidoxypropyltrimethoxysilane (GPTMS), titanium alcoxides and special additives which provide
corrosion protection of magnesium alloy. Different compositions of sol-gel systems show enhanced
long-term corrosion protection of magnesium alloy. The sol-gel coatings exhibit excellent adhesion
to the substrate and protect against the corrosion attack. Corrosion behavior of AZ31B substrates
pre-treated with sol–gel derived hybrid coatings was tested by Electrochemical Impedance
Spectroscopy (EIS). The morphology and the structure of sol-gel films under study were
characterized with SEM/EDS techniques.
Incremental Melting and Solidification Process/Mechanical Characterization of Functionally Graded Al-Si Alloys
Authors: Pinto P. , Mazare L. , Soares Delfim , Silva F.S.
Published: March 2009

The Incremental Melting and Solidification Process (IMSP) is a relatively new field for
material processing for the production of functionally graded materials. In this process a controlled
liquid bath is maintained at the top of the component where new materials are added changing the
components composition. Thus, a functionally graded material is obtained with a varying
composition along one direction of the component. This paper deals with the influence of one of the
process parameters, namely displacement rates between heating coil and mould, in order to evaluate
its influence on both metallurgical and mechanical properties of different Al-Si alloys. Hardness and
phase distribution, along the main castings axis, were measured. To better assess and characterize
the process, two different Al-Si alloys with and without variation of chemical composition along the
specimen were analysed. Results demonstrate that a gradual variation of metallurgical and
mechanical properties along the component is obtained. It is also shown that Al-Si functionally
graded materials can be produced by the incremental melting and solidification process. Results
show that the displacement rate is very important on metallurgical and mechanical properties of the
obtained alloy.
Selection of Nanofiller Dispersion Method and Properties Evaluation of Polyurethane/ZrO2:Eu Composites for Optoelectronic Applications
Authors: Ryszkowska Joanna , Zawadzak Ewelina
Published: March 2009

In the present study the distribution of nanofillers in the polyurethane matrix and the
composite properties were investigated. As a nanofiller, zirconium oxide doped with 10% Eu3+ was
used. The nanofiller was added at 0.1 wt%. Different ways of nanofiller incorporation were
investigated. The microstructure of the obtained materials was examined by atomic force
microscopy in force modulation. The size analysis of the nanofiller was investigated with HRSEM.
The thermal (DSC, TGA) properties of polyurethane nanocomposites were also investigated in
addition to the analysis of transmittance and luminescence of obtained materials. The results
obtained indicate a possibility of fabrication of polymeric nanocomposites for optoelectronic
applications via a relatively inexpensive processing route.
Physical Properties of an Artificial Extracellular Matrix Based on a Crosslinked Elastin-Like Polymer
Authors: Espírito Santo V. , Prieto S. , Testera A.M. , Alonso M. , Arias F.J. , Mano João F. , Rodríguez-Cabello José C.
Published: March 2009

An elastin-like polymer (ELP) was designed by genetic engineering techniques to mimic
the extracellular matrix (ECM). The precise control of the polymer sequence offered many
advantages that allowed the definition of distinct and specific domains. The cell attachment domain
present in the sequence enhances the cell adhesion. Hexamethylene diisocyanate, a lysine-targeted
crosslinker, was used to crosslink the purified polymer. The produced matrices presented an
adequate mechanical performance and the morphological analysis by scanning electron microscopy
show a homogeneous porous structure, ranging from nanometers to few micrometres. The biological
tests will be assessed in future work. These results show the big potential of the ELPs in biomedical
applications, especially in the development of systems for tissue engineering and drug release.
Ordered Mesoporous Titanosilicate Materials Prepared at Room Temperature: Synthesis Conditions vs Structural Properties
Authors: Galacho Cristina , Ribeiro Carrott Manuela M.L. , Carrott Peter J.M. , Valente Nabais J.M.
Published: March 2009

Mesoporous titanosilicates were directly synthesised at ambient temperature and pressure,
considering a wide range of metal content (0.01≤Ti/Si≤0.5) and using cationic surfactants of
different alkyl chain length. It is shown that the use of tetradecyl-, hexadecyl- and
octadecyltrimethylammonium bromide as structure-directing agents provide higher quality
Ti-MCM-41 materials, than those prepared with surfactants of shorter alkyl chain. The pore volume
and surface areas are gradually reduced by the increase of Ti content but up to Ti/Si=0.02 the
alterations in the pore structural properties are negligible as compared with pure silica grades,
becoming more noticeable for Ti/Si≥0.1. Nevertheless, for Ti/Si=0.1 the directly synthesised
materials still have high pore volumes as well as high regularity and uniformity of the hexagonal
pore array, with superior pore structural properties to those of materials prepared by post synthesis
deposition of titanium on silica MCM-41, which did not provide a valid alternative for minimising
the disruptive effect of high metal content on the hexagonal porous structure.
Preparation of Porous Glass Scaffolds by Salt Sintering Technique
Authors: Davim Erika , Fernandes Maria Helena F.V. , Senos Ana Maria R.
Published: March 2009

This paper reports a preliminary study on the development and characterization of a
porous calcium phosphate glass-ceramic for tissue engineering application. To obtain porous glass
scaffolds, a mixture of 3CaO.P2O5-SiO2-MgO glass (grain size below 20 'm) and NaCl with 200-
300 'm of particle size was taken in the volume proportion 1:1. The mixture was shaped into
cylindrical samples (10 mm diameter x 10 mm thick) by using unidirectional pressing. The sintering
thermal cycle was selected by means of thermal analyses (DTA/TG and dilatometry) in order to
attain a high enough cohesion among the glass particles. After thermal consolidation, the salt was
dissolved in water, resulting in highly porous materials. The effect of the sintering thermal cycle on
the structure and microstructure characteristics of the scaffolds was investigated in this paper.
Study of the Degradation of a Polyesther-Polyurethane by TGA and the Logistic Mixture Model
Authors: Barbadillo Fernando , Fuentes A. , Naya Salvador , Cao Ricardo , Mier José Luís , Artiaga Ramón
Published: March 2009

The logistic mixture model was successfully studied previously in the separation of
overlapping steps in some polymeric systems by the authors. In the present work, this method is
applied to a polyesther-polyurethane degradation under air and inert atmospheres at several heat
rates (5, 10, 15, 20 and 25 °C/min) in dynamic TGA. Every logistic component is fitted by reaction
order, Johnson-Mehl-Avrami and Sestak-Berggren kinetics equations in order to calculate its kinetic
parameters (activation energy, frequency factor and exponents). The reaction order model gives a
good fitting and reproduces accurtelly the experimental curves. Johnson-Mehl-Avrami and Sestak-
Berggren equations resulted to be not suitables because of the activation energy values obtained.
Uniaxial Stretching above the Glass Transition Temperature of Poly(Ethylene Terephthalate) and its Effects on the Structure Development
Authors: Todorov Lyudmil V. , Freire Olga M. , Viana Julio
Published: March 2009

This work deals with an experimental investigation of the strain-induced crystalline
microstructure that develops under uniaxial elongation of amorphous poly(ethylene terephthalate),
PET, above its glass transition temperature, as an approach for industrial stretch-blow moulding
processes. The present study aims at: a) defining the most relevant processing parameters which
govern and are of significance for the induced morphology, and b) establishing of relationships
between processing and morphology. Compression moulded amorphous PET was uniaxial stretched
with variations of following stretching parameters: stretching temperature, Tst, stretching velocity,
Vst, and stretching ratio, λst, that were varied in two levels according to a L8 Taguchi orthogonal
array. The developed morphologies were characterized by differential scanning calorimetry (DSC)
and birefringence measurements. Obtained results were analyzed by ANOVA statistical tool. The
glass transition temperature, Tg, is influenced mainly by the stretching ratio. The cold crystallization
temperature, Tcc, is determined by complex influence of all stretching variables and the interaction
Tstxλst. The degree of crystallinity, χc, mainly depends upon Vst and Tstxλst interaction. The
birefringence, n, is essentially determined by λst and the interaction Vstxλst. The distinct
morphological parameters are then related with the purpose of understand the structure development
upon polymer stretching.
Photodegradation Studies of Poly(Vinylidene Fluoride)
Authors: Gonçalves A.M. , Serrado-Nunes Jivago , Sencadas Vitor , Botelho Gabriela , Belsley Michael , Lanceros-Méndez Senentxu
Published: March 2009

In this work, commercial poly(vinylidene fluoride) PVDF, in its β phase was analysed
before and after the samples were exposed to UV radiation using a xenon lamp, for ten weeks.
Changes in chemical structures, crystallinity, dielectric and piezoelectric response were
investigated. From the present study it can be concluded that PVDF shows high stability towards
photodegradation and can be used for outdoor applications without interference in its performance.
Biodegradable Polymers Extracted from “Sargaço”: Film Properties and Application to Edible Coating
Authors: Sousa Ana M.M. , Martins Sandra , Larotonda Fabio D.S. , Hilliou Loic , Gonçalves Maria P. , Sereno Alberto M.
Published: March 2009

“Sargaço” is the name given to a mixture of dead seaweeds collected on Portuguese
beaches. “Sargaço” is composed of algae containing biopolymers such as carrageenan, alginate and
agar which are extensively used in food and pharmaceutical industries as gelling and stabilizing
agents. The objective of this work was the biopolymers extraction from “Sargaço”, collected at
Leça da Palmeira-Portugal, for production of biodegradable films and subsequent application in
edible coatings for food. A mixture of biopolymers was hot-extracted from alkali treated “Sargaço”.
Films were made from an optimized extract, using the knife coating technique. Films physical
properties were characterized and results show that biodegradable films from “Sargaço” are more
hygroscopic, less elastic, more deformable, and more permeable to water than films obtained from a
commercial alginate and a domestic κ/ ι-hybrid carrageenan developed during previous studies. As
such, this mixture of biopolymers is an interesting cheap alternative to produce biodegradable
materials and a potential application to fresh fruit preservation has been tested.
Preparation of Composites by In Situ Polimerisation of PET-Hydrotalcite Using Dodecylsulphate
Authors: Martínez-Gallegos S. , Herrero Maria , Rives Vicente
Published: March 2009

A polyethylenterephthalate-hydrotalcite (PET-HT) composite was prepared by in situ
polymerisation, using polyethylenterephthalate (PET) and different amounts of a hydrotalcite with
dodecylsulphate in the interlayer space (DS-HT). The resulting material has been characterised by
powder X-ray diffraction (PXRD) and thermogravimetric (TG) analysis. The thermal stability of
PET is not greatly enhanced upon incorporation of the inorganic component, despite PXRD shows
that the HT is exfoliated in the composite. Thus with 2-10% shows a complete dispersion of the
layered component in the polymeric matrix, while if the inorganic loading is between 20-50 %
(larger loadings were not tested) no complete dispersion is achieved and PXRD-detectable
agglomerates are formed.
Assessment of the Corrosion Behavior of Nd-Fe-B Magnets Used in Dentistry
Authors: Martins E.A. , Costa Isolda , Rossi J.L. , De Melo Hercílio G.
Published: March 2009

Permanent magnets based on intermetallic compounds are employed in dentistry to fix
dental prosthesis. However, these materials are very sensitive to corrosion. In this study the
corrosion behavior of a sintered commercial Nd-Fe-B magnet has been investigated at neutral pH in
a phosphate buffered solution (PBS). With this aim demagnetized specimens were immersed in the
test solution and their corrosion behavior were monitored at increasing test times by means of
electrochemical impedance spectroscopy ( EIS ), potentiodynamic polarization curves and surface
observation by scanning electron microscopy ( SEM ). Experimental results indicated that the
corrosion resistance is seriously affected in this solution. Moreover, no decrease in the intensity of
the corrosive attack was verified during test periods of up 4 hours. Impedance results have indicated
the occurrence of diffusion controlled phenomenon, likely linked to the presence of pores in the
magnet microstructure.
X-Ray Diffraction Study of NiTi Produced by Mechanically Activated Reactive Extrusion Synthesis (MARES)
Authors: Neves Filipe , Martins Isabel M. , Correia Jose Brito , Oliveira Manuela , Gaffet Eric
Published: March 2009

This study reports the use of X-ray diffraction quantitative phase analyses in NiTi alloys
produced by MARES (Mechanically Activated Reactive Extrusion Synthesis). These analyses were
performed with the PowderCell 2.4 software. The mechanically activated powders heated in a DTA
furnace at 500 °C had as main phases Ni (27 wt %) and Ti (30 wt %) and the major intermetallic
phase was Ni3Ti (20 wt %). Above 500 °C the intermetallic phases were predominant. At 600 °C the
major phase was Ni3Ti (29 wt %) and at 700 °C was NiTi2 (32 wt %). In this temperature range the
NiTi was a minor intermetallic phase (14-20 wt %). No changes in the constitution or in the amount
of the phases were detected between the degassed powder samples and the extruded materials. The
intermetallic phases were always predominant and the major was Ni3Ti (27-32 wt %). The NiTi
phase content was in a range of 15-22 wt %. The weighted residual error, Rwp, of the fittings
ranged between 17 and 27. Using the Williamson and Hall plot, crystallite sizes within the range of
26-53 nm and of 12-25 nm were evaluated for the metallic and intermetallic phases, respectively.
Vickers micro-hardness measurements were virtually unchanged with the extrusion parameters but
increased relatively to the mechanically activated powders.
Effect of the Processing Conditions on the Mechanical Properties of Urethane Magnetorheological Elastomers
Authors: Boczkowska Anna , Awietjan Stefan F.
Published: March 2009

The aim of the study was to develop an innovative processing method of
magnetorheological elastomers (MRE). This method comprises optimization of the MRE structure
in the context of their performance in the magnetic field. The influence of the amount of
ferromagnetic particles and their arrangement in relation to the external magnetic field was
investigated. Urethane magnetorheological elastomers were manufactured using polyurethane gels,
supplied by Dow Chemical Company. As the ferromagnetic carbonyl–iron powder with particles
size from 6-9)m produced by Fluka was used. The amount of the carbonyl iron particles was varied
from 1.5 to 33.0 vol. %. Magnetic field strengths used during the fabrication of MRE were 0.1 and
0.3 T. The samples with particle chains aligned or slopped at 45 degree to the long sample axis were
produced. To evaluate the external magnetic field effect on the magnetorheological properties a
deflection in the magnetic field was measured. Samples were placed parallel to the magnetic field
lines and deflected prior to the application of a magnetic field. After the application of the magnetic
field the sample tended to straighten which was measured by displacement sensor. Magnetic field in
a range of 0-0.9 T has been applied. Also the compression tests were carried out without and within
external magnetic field with the strength of 0.3 T. The experiment showed that application of the
magnetic field increases stiffness of the material. The amount of iron particles and their
arrangement have influence on the stress-strain curves course.
Implementation and Testing of Smart Composite Laminates with Embedded Piezoelectric Sensors/Actuators
Authors: Ramos Carlos A. , de Oliveira Rui , Marques António Torres
Published: March 2009

In this study the embedding of piezoelectric ceramics in carbon-fibre/epoxy laminates is
studied with the purpose to be used for structural health monitoring from vibration measurements.
Piezoelectric elements were embedded in two laminate types made of two weaved prepregs and
with four additional unidirectional prepregs, respectively. The efficiency of the embedding process
was analysed from the capability of the piezoelectric ceramic to transmit vibrations to the composite
plate. The sensing element was successfully used to monitor the composite plate when submitted to
three-point bending dynamic tests at different frequencies.
Embedded Sensors for Corrosion Monitoring of Existing Reinforced Concrete Structures
Authors: Pereira E.V. , Figueira R.B. , Salta Manuela M. , Fonseca I.T.E.
Published: March 2009

In this work the performance of two surface treatments and the efficiency of a corrosion
inhibitor were evaluated, in the control of steel corrosion in concrete induced by chlorides, through
measurements of galvanic current and polarization resistance applied to embedded sensors fixed in
existing concrete using different methodologies. From the results obtained the use of the different
embedded sensors in the measurement of corrosion rate is discussed aiming the development of new
systems for permanent evaluation of the on site performance of products for repairing reinforced
concrete structures affected by reinforcement corrosion.
Computer Simulation of Hole Distribution in Polymeric Materials
Authors: Barbosa Hélder M.C. , Ramos Marta M. D.
Published: March 2009

Polymers have been known for their flexibility and easy processing into coatings and
films, which made them suitable to be applied in a variety of areas and in particular the growing
area of organic electronics. The electronic properties of semiconducting polymers made them a
serious rival in areas where until now inorganic materials were the most used, such as light emitting
diodes or solar cells. Typical polymers can be seen as a network of molecular strands of varied
lengths and orientations, with a random distribution of physical and chemical defects which makes
them an anisotropic material. To further increase their performance, a better understanding of all
aspects related to charge transport and space charge distribution in polymeric materials is required.
The process associated with charge transport depends on the properties of the polymer molecules as
well as connectivity and texture, and so we adopt a mesoscopic approach to build polymer
structures. Changing the potential barrier for charge injection we can introduce holes in the polymer
network and, by using a generalised Monte-Carlo method, we can simulate the transport of the
injected charge through the polymer layer caused by imposing a voltage between two planar
electrodes. Our results show that the way that holes distribute within polymer layer and charge
localization in these materials is quite different from the inorganic ones.
Visualization of Injection Moulding Process
Authors: Yanev A.S. , Dias Gustavo R. , Cunha António M.
Published: March 2009

A special tool-transparent mould designed to visualize the melt flow inside the cavity is
used in this research. The aim of the work is to assess the polymer melt behavior under different
processing conditions-close to industrial, in conventional and two materials non-conventional
injection moulding techniques. The mould is designed with two injection locations and has
possibility to change the geometry of the cavity in order to investigate the melt behavior in
differently shaped cavities. Visual access in the mould is allowed by the sapphire windows,
surrounding the cavity. For image acquisition a high speed video camera NAC 1000 is used.
Materials used in the research are three polypropylenes with different flow index. Results are
obtained for conventional injection moulding, two material monosandwich and two material biinjection
moulding. Apart from visualization, instrumentation of the mould allows to be obtained
PT data for each processing condition. Results from conventional injection moulding are compared
with MPI5.0 simulations.
Numerical and Experimental Analysis of Laser Surface Remelting of Al 9wt% Si Alloy Samples
Authors: Cheung Noé , Cruz Kleber A.S. , Khan Noman H. , Garcia Amauri
Published: March 2009

Laser materials processing has been widely applied in industrial processes due to unique
precision and very localized thermal action furnished by the laser’s high energy density and power
controllability. With the inherent rapid heating and cooling rates to which this surface layer is
subjected, this process provides an opportunity to produce different microstructures from that of the
bulk metal leading to useful properties. The aim of this work is to develop a heat transfer
mathematical model based on the finite difference method in order to simulate temperature fields in
the laser surface remelting process. Convective heat transfer in the remelted pool is taken into
account by using the effective thermal conductivity approach. Theoretical predictions furnished by
previous models from the literature were used for validation of numerical simulations performed
with the proposed model. Experiments of laser surface remelting of Al-9 wt pct Si samples was
carried out in the present investigation, and numerical simulations was applied for the laser machine
operating parameters. The work also encompasses the analysis of microstructural and
microhardness variations throughout the resulting treated and unmolten zones.