bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of the Fabrication Parameters of PZT 52/48 Thin Films by Pulsed Laser Ablation
Authors: Fernandes José R. A. , Joanni Ednan , Savu Raluca
Published: March 2009

Thin films of PbZr0,52Ti0,48O3 (PZT) for applications in piezoelectric actuators were
deposited by the pulsed laser deposition technique (PLD) over Pt/Ti/SiO2/Si substrates. The effect
of different electrode and PZT deposition and processing conditions on the ferroelectric and
piezoelectric properties of the devices was investigated. X-Ray diffraction results showed that the
deposition temperature for the electrodes had a strong influence on the PZT orientation; the increase
in the electrode deposition temperature changes the PZT orientation from random or (111) to (001)
depending also on PZT deposition pressure. From scanning electron microscope (SEM) pictures
one could also observe that the deposition pressure affects the porosity of the PZT films, which
increases with the pressure above 1×10-1 mbar for films deposited at room temperature. The
measurement of the ferroelectric hysteresis curves confirmed that the structural changes induced by
different processing parameters affected the ferroelectric properties of the material. The best
ferroelectric properties including fatigue endurance were obtained for electrodes made at high
temperature and for PZT deposited at 2×10-2 mbar and heat treated at 675°C for 30 minutes in an
oxygen atmosphere. The piezoelectric coefficient d33, measured using a Michelson interferometer,
had values in the range between 20 and 60 pm/V, and showed a strong dependence on the thickness
of the PZT films.
Effect of Oxygen Content on Impedance Spectra of PtRh Electrodes for NOX Sensing Applications
Authors: Kurek Piotr , Thiemann-Handler S. , Marzantowicz M. , Wasiucionek M.
Published: March 2009

Growing awareness of dangers related to NOX emission by industry and road
transportation has resulted in increasing demand for sensors detecting NOX. An important class of
these sensors use Pt-based electrodes applied on yttria-stabilized zirconia (YSZ) substrates.
Performance of such sensors depends on redox reactions occurring at electrodes in the tested
atmospheres. Impedance spectra and j-U curves of PtRh electrodes were measured in a 3-electrode
mode, using Pt metal pads as counter and reference electrodes. The data were collected in a 10mHz-
100kHz frequency range at temperatures from 450 to 750°C. Each series of measurements was
carried out in a gas mixture with different oxygen content ranging from 0 to 21 vol%. It was found
out that the low-frequency part of the impedance spectra (characterizing electrode processes) was
sensitive to the oxygen content in the gas mixtures.
Photoinduced Effects in EPR Spectra of Copper Doped Potassium Tantalate
Authors: Badalyan Andréy G. , Azzoni Carlo B. , Galinetto Pietro , Mozzati Maria Cristina , Jastrabik Lubomir , Rosa Jan , Hrabovsky Miroslav , Syrnikov P.P. , Trepakov V.A.
Published: March 2009

The UV illumination effects in KTaO3 single crystals with Cu2+ impurity ions have been studied by electron paramagnetic resonance method. Single crystals both “as-grown” and thermally treated in oxygen atmosphere were investigated. It was found that the EPR signal of the Cu2+ centers decreases in the “as-grown” crystals during UV-irradiation at 365 nm, in the wholeinvestigated temperature range (3.7- 300 K). On the contrary, for the oxidized specimens a sizeable increase of the EPR signal of Cu2+ centers (except the signal from exchange coupled pair centers) is observed under UV illumination in some temperature regions.
Modification of Organic Coatings with Thin Plasma Polymer Films. Influence on the Barrier Properties
Authors: Serra Ricardo , Zheludkevich Mikhail L. , Grundmeier Guido , Ferreira Mário G.S.
Published: March 2009

Deposition of thin plasma polymer films as final layer on organic coatings can provide
one promising solution to tailor the surface properties offering third functionality and increased
mechanical properties.
The present work is dedicated to the study of the barrier properties of polyurethane coil coatings
modified by different plasma polymerization processes. Microwave (MW) and radio frequency
(RF) plasmas were used to deposit thin films with different composition from various precursor
mixtures. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) were used
to reveal the evolution of the plasma treated coil coatings during weathering tests. Electrochemical
impedance spectroscopy (EIS) was employed to study the barrier properties of the coatings.
The results show a degradation effect of the plasma treatment on the barrier properties of the coil
coatings especially in the case of the oxygen-containing plasmas. However addition of a fluorinecontaining
component to the precursor mixture leads to the elimination of the negative effect of the
plasma treatment on the barrier properties of the coil coatings. The fluorine-containing films exhibit
higher weathering stability in comparison with the fluorine-free ones.
Using Experiments Design to Model the Effect of Raw Materials on the Sintering and Technological Properties of Brick Compositions
Authors: Correia Sivaldo Leite , Grun Elayne , Denardi Christian D. , Hotza Dachamir , Folgueras Marilena Valadares
Published: March 2009

Mixtures of clays are often used in the manufacture of bricks. In industrial practice, it is
desirable to be able to predict, in an expeditious way, what the effects of a change in raw materials
or the proportions thereof might be in the various processing steps towards the final product. When
the property of interest is basically determined by the combination of raw materials, an optimisation
methodology specific to the design of mixture experiments can be successfully used. In the present
study, fired bending strength and linear firing shrinkage were selected as the properties to model.
Ten formulations of three different clays were selected and used in the experiments design. Those
formulations were wet processed, uniaxially pressed, and then fired at 1000 °C for 2 h.. From the
experimental results, regression models were calculated, relating each technological property with
the proportions of raw materials. The regression models were then used simultaneously to define
which combination of those three raw materials was most adequate to produce, under constant
processing conditions, a brick with specified properties.
Optimisation of Cordierite Processing through Taguchi Method
Authors: Oliveira Fernando A. Costa , Tavares Sandra , Domingues Joaquim , Fernandes Jorge Cruz , Dias Diamantino
Published: March 2009

When applied to product engineering, the Taguchi method allows the identification of the
conditions that lead to the development of similar products with a small variation around a
particular target value. In the present work, the Taguchi method was used to evaluate the effect of
four processing parameters on the mechanical properties of a commercial dense cordierite in order
to maximize the flexural strength of the resulting bodies. Using a L9 orthogonal array, four control
factors (named A, B, C and D) at three levels, namely type (AS1, AS2 and AS3) and content (18, 20
and 22 wt%) of alumina added, cooling rate (1, 3 and 5 °C⋅min-1) and average particle size of each
batch (5, 6 and 7 μm) were set. Hence, with a reduced number of experiments, it was possible to
identify the factors and their levels, which have most contributed to an increase in flexural strength
of the resulting cordierite bodies. The optimum conditions to obtain bodies having a flexural
strength higher than 100 MPa were the addition of 22 wt% of AS2 alumina, an average mixture
particle size of 5 μm and a cooling rate of 1 °C⋅min-1. The type of alumina had a negligible effect on
flexural strength whereas the other factors affect considerably the strength.
Multilayer Plug Assisted Thermoforming-Concept and Practical Usefulness
Authors: Duarte Fernando M. , Covas José A.
Published: March 2009

This work presents a methodology to improve the final thickness distribution of
thermoformed parts. The conventional plug is replaced by a new version containing concentric
layers with independent displacements. The results show that thickness gradients can be
significantly reduced, with a simultaneous increase of the minimum values. Varying the relative
displacement of the inner layers can bring about significant differences in the final thickness
distribution, thus enabling the production of parts with prescribed thickness profiles that maximise
their mechanical performance.
Geometry and Topology of 3D Voronoi Partitions
Authors: Reis Nuno , Ferro Alberto C. , Pereira José Carlos
Published: March 2009

A new algorithm to determine Voronoi partitions of space using periodic boundary
conditions has been implemented in GAMGI free software package. This algorithm was used to
study the topological and geometric properties of Voronoi polyhedra obtained for Poisson and
Laguerre seeding distributions. The Random Sequential Adsorption (RSA) method was used to
generate a Laguerre seeding distribution with a volume fraction of spheres φ ≈ 0.36. The resulting
normalised cell volume distributions were compared with the gamma and lognormal density
functions using χ2 goodness of fit testing, and in both cases the gamma function provides a better
description. The Lewis and Aboav empirical relations approximately apply to both partitions, with
least square correlation factors R2 equal to 0.98 for the Lewis law and 0.95 for the Aboav law.
Predicting Shrinkage in Semi-Crystalline Injection Mouldings – The Influence of Pressure
Authors: Pontes A.J. , Pouzada António Sergio
Published: March 2009

In this study, the as-moulded shrinkage and pressure data are obtained experimentally
and compared with numerical simulations. The mouldings were produced in polypropylene (PP).
The effect of pressure on viscosity in the predicted pressure evolution was analyzed and also its
influence on the shrinkage. The results show that the rise of holding pressure determines the
reduction of the shrinkage. Also, it was observed that the pressure predictions are qualitatively in
good agreement with the experimental data. However noticeable quantitative discrepancies can be
observed when the effect of pressure on viscosity is not considered. If the effect of pressure on the
melt viscosity is considered the deviation between predicted and the experimental pressure
evolution is substantially reduced.
EPR and Optical Absorption Investigations of Photochromic Effect in Nearly Stoichiometric LiNbO3:Fe
Authors: Mozzati Maria Cristina , Badalyan Andréy G. , Demaestri Giulia , Galinetto Pietro , Rossella Francesco , Bermúdez Veronica , Azzoni Carlo B. , Samoggia Giorgio
Published: March 2009

EPR and optical absorption measurements have been performed on nearly stoichiometric lithium niobate single crystals with iron in traces and in 0.1% molar nominal amount. Thermal treatments in reducing atmosphere allowed to obtain samples with different Fe2+/Fe3+ ratios. The Fe2+/Fe3+ dynamic has been observed by irradiating the samples with UV and visible light in the
temperature range 4-300 K: the photochromic effect resulted to be more evident in the strongly reduced crystals. A simple model to explain the photochromic behavior in nearly stoichiometric LiNbO3:Fe is proposed.
Diffusion Welding of WC-Co (Hardmetal)/ High Strength Steels
Authors: Gómez de Salazar José Maria , Barrena Maria Isabel , Merino N. , Matesanz Laura
Published: March 2009

The present work shows the microstructural and mechanical results obtained in joints
WC-Co / steel 90MnCrV8 (high strength steel). The joints were carried out using diffusion welding
processes and soft interlayers Cu-Ni. The binary Cu-Ni alloys were obtained by electrochemical
deposition techniques. The microstructural and mechanical changes provoked in the steel, due to
heat treatments, were studied in order to know plastic deformation during the joints. The diffusion
welds were obtained in an Edwards vacuum furnace (10-3 - 10-4 Pa), three welding temperatures
were used, (825 °C, 850 °C and 875 °C) and 30, 45 and 60 minutes, as welding times. The constant
pressure was 5 MPa. The welding interface microstructure was studied by scanning electron
microscopy (SEM-EDX). In order to determine the mechanical behaviour of all joints were carried
out shear tests. The optimum results were obtained at 850 °C / 45 min and 850 °C / 60 min.
Nevertheless, the diffusion welding conditions allowed attaining high quality welding interfaces in
all joints of WC-Co / 90MnCrV8
Application of Braided Fibre Reinforced Composite Rods in Concrete Reinforcement
Authors: Sousa Fangueiro Raul Manuel Esteves , Sousa Guilherme , Soutinho Filipe , Jalali Saíd , de Araújo Mário
Published: March 2009

This paper describes the work that is being done at the University of Minho concerning
the development of braided rods for concrete reinforcement. A preliminary research study has been
conducted to understand the mechanical behaviour of braided fabrics. Various samples have been
produced varying the type of fiber (glass, polyester and aramid), the type of braided fabric (simple,
hybrid and core reinforced) and in the latter case, the number of core reinforcing yarns. The tensile
properties of these samples have been evaluated and the results presented. The influence of each
factor on the tensile properties of braided fabrics has also been analysed and discussed. In order to
produce braided reinforced composite rods to use as a concrete reinforcement, a special technique
has been developed using a standard vertical braiding machine. The braided reinforced composite
materials have been produced in rib structure to improve adhesion between them and the concrete.
Special samples have been prepared and tested to evaluate the adherence between both materials
involved. The tensile and bending properties of braided reinforced composite rods have been
evaluated and the results obtained presented and discussed.
The Influence of Tribophysical Activation on Non-Isothermal Sintering of BaTiO3 Ceramics
Authors: Pavlović Vera P. , Nikolić Maria V. , Spasojević V. , Blanuša Jovan , Živković Ljiljana , Stojanović B.D. , Pavlović Vladimir B. , Ristić Momcilo M.
Published: March 2009

In this paper the influence of tribophysical activation on non-isothermal sintering of
barium titanate has been investigated. BaTiO3 powders were tribophysically activated in a planetary
ball mill for 0, 60 and 120 min., pressed and non-isothermally sintered up to 1380oC. Dilatometric
analysis was performed in air in the temperature range from room temperature to 1380oC with
heating rates of 10, 20 and 30oC/min. The samples were analyzed by the X-ray powder diffraction
method. Investigation of the morphology of microstructure constituents was performed using the
scanning electron microsocopy method. With the purpose of optimizing technological parameters
the results obtained by microstructure analysis were correlated with the results of quantitative
dilatometric analysis.
Adobe's Mechanical Characterization in Ancient Constructions: The Case of Aveiro's Region
Authors: Martins Tiago , Varum Humberto
Published: March 2009

Adobe is commonly found in Aveiro's ancient constructions. Preservation and
rehabilitation of those constructions, some of them with architectural and historical interest, has
been forgotten for many years. As a result, in Aveiro region, the majority of existing constructions
in adobe is structurally weak, and, in several cases, they are in the threshold of ruin. Rehabilitation
and/or strengthening urge.
Despite some efforts has been made, a great difficulty for technicians working on the rehabilitation
of these constructions relies on the lack of knowledge on adobe's mechanical behaviour. In fact, in
order to properly describe the structural behaviour of those constructions, there is a need to
investigate the mechanical behaviour of adobe. Hence, this paper is based on a study intended to
characterise the behaviour of adobe brick units. Specimens were prepared from selected
representative constructions of the Aveiro region. The prepared specimens were tested in order to
evaluate their mechanical behaviour in compression and tension.
Normal Contact Response of a Coating Containing an Interlayer
Authors: Zhang Xian Cheng , Xu Bin Shi , Wang Hai Dou , Wu Yi Xiong
Published: March 2009

The purpose of the present paper was to investigate the effect of interlayer on the
maximum contact stresses in the critical regions in a hard coating under static contact condition
using finite element analysis. Four different elastic moduli and nine different thickness of interlayer
were used. Modeling results showed that the interlayer did not reduce the maximum shear stress at
the coating/substrate interface, whether it was thick or thin. When the thin interlayer was presented,
whether it was soft or hard, the maximum tensile stress on surface and maximum von Mises stress
within coating were decreased.
High Field Polarization Response in Ferroelectrics: Current Solutions and Challenges
Authors: Klotins Eriks
Published: March 2009

Polarization response including ergodicity breaking and the divergence of relaxation time is reproduced for model Hamiltonians of growing complexity. Systematic derivation of the dynamical equations and its solutions is based on the Fokker-Planck and imaginary time Schrödinger equation techniques with subsequent symplectic integration. Test solutions are addressed to finite size and spatially extended problems with microscopically interpretation of the model parameters as a challenge.
On a New Method Based on X-Ray Diffraction to Identify Stress-Strain Laws on Surface-Treated Materials
Authors: Batista António Castanhola , Nobre Joao P. , Dias A. Morão
Published: March 2009

A characterisation technique based on the stress determination by X-ray diffraction has
been developed. It enables the identification of elastoplastic stress-strain laws on materials
presenting an in-depth gradient of mechanical properties on its cross section. This technique is
especially suitable to the characterisation of surfaces due to the small X-rays penetration depth. The
method was applied in the characterisation of a carbonitrided and shot-peened steel, allowing to
evaluate the stress-strain laws of the material at the surface, the intermediate layers and the bulk
material. In addition, the in-depth evolution of microhardness, residual stresses, diffraction peak
broadening and retained austenite contents were analysed. This allowed to understand the results of
the proposed technique.
Influence of Grain Size on the Setting of Portland Cement: A Stray-Field Magnetic Resonance Imaging Study
Authors: Nunes Teresa G.
Published: March 2009

A number of failures of large concrete structures during construction have been reported in the last
decades [1]. The overestimation of concrete strength at early ages was one of the reasons for the
failures. Consequently, reliable information about early age properties of the material is essential to
guarantee life-time performance of structures. Portland cement is a complex heterogeneous
particulate material and a full knowledge of kinetics of the hydration reactions, for example, is still
missing. Gel constitutes the major phase in the hardening cement paste and the corresponding
structure and dynamics represent an important contribution to determine the concrete performance.
X-ray diffraction, which is widely used for the study of crystalline cement components, does not
give information about the gel, amorphous, phase. Conversely, 1H stray-field magnetic resonance
imaging (STRAFI-MRI) technique has proved to be a powerful tool to follow the early hydration
and hardening periods of Portland cement (type I) [2-4]. The setting of cement pastes depends on
parameters like the initial water/cement ratio, R, or particle size of the powder (G) and the
compressive strength can be used to characterize the behaviour of hardening concrete. Water
availability at the particle surfaces, which is controlled by R and G, limits cement hydration. At low
R, G effects are less important. In general, it is accepted that for R<0.42, unreacted solid remain, as
all the free volume is filled with hydration products [5]. For example, hydration of Portland cement
pastes as a function of R (0.24-0.48) was studied using by STRAFI-MRI and hydrogen maps, from
different types of water (capillary, gel or chemically bound water), enabled a spatially-resolved
kinetics to be obtained [4]. Using STRAFI-MRI was now evaluated the influence of G (<70 μm to
< 90 μm) on the early stages of hydration and hardening of Portland cement.
Portland cement uses extend well beyond construction. For example, a mineral trioxide aggregate is
now being applied as a root-end filling material, which was shown to have a similar chemical
constitution to that of Portland cement except for the addition of bismuth compounds, seemingly to
make the materials radiopaque for dental use [6].
Characterisation of Ceramic Pastes of Portuguese Ancient Tiles
Authors: Carvalho Ana P. , Vaz M. Fatima , Samora Maria J. , Pires João
Published: March 2009

Portuguese ceramic tiles of different origins from XVIth century to XXth century were
studied. In this work we describe microstructural, mechanical and mineralogical characterisation
and water absorption studies. Microstructural features (pore size) were determined using Scanning
Electron Microscope (SEM) photographs. Mechanical tests (four point bending) were performed
and the bending strength was determined from the fracture loads. From water absorption essays the
absorption coefficient and the total amount of water retained were obtained and the open porosity
was estimated. The maximum water absorbed tends to decrease from XVIth century until XXth
century, showing a more pronounced drop for the tiles of the XIXth and XXth centuries. This
evolution is also observed in the open porosity values. From image analysis data we also observed
that porosity decreases progressively with time and an important drop is observed for XXth century
tiles. The bending resistance of tiles from XVIIth to XXth century is almost constant and higher
than that of XVIth century samples. This evolution does not correlate with porosity. Advances in
ceramic processing, such as higher firing temperatures may lead to the appearance of quartz as
almost the only crystalline phase. We consider that an increase in the bending strength is due to a
more effective vitrification and a lower porosity.
Low Pressure RF Plasma Jet Sputtering Technique Applied to Ferroelectric Films: Ba1-x SrxTiO3
Authors: Deyneka Alexander , Hubička Zdenek , Trepakov V.A. , Suchaneck Gunnar , Jastrabik Lubomir , Gerlach Gerald , Pokorny Jan , Chvostova Dasgmar , Olejníček J.
Published: March 2009

Technology aspects and characterization of BaxSr1-xTiO3 (BST) films fabricated with low pressure plasma jet technique are presented. BST films were deposited on silicon coated with Pt/TiO2/SiO2 and on bare Si substrates. The nozzles-type RF hollow cathode has been fabricated from hot pressed BaTiO3, SrTiO3, and BST ceramics. Controlling of RF voltage, RF current and substrate temperature allowed us to deposit reproducible films with controlled grain size. Hysteresis
loops, ellipsometric and micro-Raman investigation results are presented and discussed.
Applications of Quantitative Image Analysis to the Description of the Morphology of Boehmite and their Polyurethane Nanocomposites
Authors: Ryszkowska Joanna
Published: March 2009

This paper presents the application of stereology methods to the description of
morphological properties of nanoboehmite and its nanocomposites. Images of boemithe, fracture
and cut surface of composites were obtained using high-resolution electron microscopy technique
and atomic force microscopy. Quantitative analysis of the fracture structure images obtained with
HRSEM technique, allowed us to explain the mechanism of changes of mechanical and thermal
properties of polyurethane nanocomposites, as well as allowed to determine relationships between
structure characteristics and properties of examined materials. Quantitative image analysis was also
found to be useful in comparative analysis of polyurethane nanocomposites structure and structure
of boehmite and products of its modification.
Micromemory Effects Involved during Martensitic Transformation in Ni-Rich NiTi Alloy
Authors: Mahesh Karimbi Koosappa , dos Santos Christian M.L. , Braz Fernandes Francisco Manuel
Published: March 2009

In the present study, interrupted mechanical cycles are performed to observe ‘micromemory
effect’ for the Ni-rich (Ni51.0at%-Ti) Ni-Ti Shape Memory Alloy (SMA) with different
strain rates. In addition, the tensile test is coupled with the four-probe electrical resistivity (ER)
measurements. Coupled measurements of stress-strain and electrical resistivity for mechanical
cycling (with SIM) have not yet been reported in the literature. The behaviour of the alloy during
the interrupted cycles is discussed on the basis of the ER profile
Hardware and Software Improvements in the Hotbird
Authors: Franco Nuno , Alves Eduardo , Barradas Nuno P.
Published: March 2009

The Hotbird is a state of the art X-ray laboratory for advanced materials characterisation,
installed at ITN since 1999. Several major improvements in its capabilities have been implemented.
On the one hand, new hardware developments have extended the applications that can be studied
and on the other hand, new software has enabled both enhanced automated control of the system,
and improved data analysis that leads to extraction of further precise information from the data.
One improvement was the implementation of the x-ray reflectometry (XRR) technique, which is a
major expansion of the Hotbird capabilities. XRR is well-suited to characterise film thickness and
roughness with high resolution. Furthermore, several optics improvements, such as a Göbel mirror
and monochromators were introduced. The combination of this optics allows one to use either a
higher intensity beam (orders of magnitude better) or a higher resolution beam configuration. A
new high-temperature chamber was developed, which allows one to perform in-situ experiments
with excellent temperature control up to 800 °C, in all possible configurations. Data
simulation/fitting analysis software for XRR was developed. Also, to control the diffractometer and
perform experiments, a new user-friendly software package was developed.
In order to illustrate the Hotbird capabilities improvements, several experimental examples will be
described.
Reusing Porcelain Tile Polishing Wastes in the Manufacturing of Aluminosilicate Fireplace Bricks
Authors: Santos Regina C. , Correia António Sousa , Andrade Guilherme
Published: March 2009

Waste porcelain tile polishing sludges result from sediments of the treatment plants of
tile manufacturing industrial wastewater. These polishing by-products are essentially a mix of fine
residues of the specific ceramic body and a coarse residue of the abrasive used for polishing the
surface of the tiles.
In the present work, it was studied the use of porcelain tile polishing sludges, as a raw material in
manufacturing of aluminosilicate fireclay bricks to be used in fireplaces.
In order to establish the feasibility of the process and to develop the addition conditions, a set of
appropriate ceramic compositions of white and red fireclays was studied.
Results showed that up to 10 % in weight of the basic raw materials could be preplaced by tile
polishing dry sludges, without significant changes in the ceramic process and the resulting materials
properties.
Use of Sewage Sludge in the Production of Light-Weight Ceramic Bricks
Authors: Dutra Ricardo Peixoto Suassuna , Gomes Uilame Umbelino , Nascimento Rubens Maribondo , Martinelli Antonio Eduardo , Paskocimas Carlos Alberto
Published: March 2009

Sewage sludge consists of a solid mixture of biological and mineral origin. It is the main
byproduct of Effluent Treatment Stations. Its final draining has been a relevant environmental
problem in several countries. In Brazil, due to the growth of the urban population and the
requirements of environmental agencies, efficient ways for sludge disposal or effluent treatment
have been investigated. Possible discarding solutions include incineration, pelletization, energy
production and addition to fertilizers. This work focuses on the use of sludge in the ceramic
industry for the production of light ceramic blocks, since this residue is basically composed of
organic substances which volatilize during high temperature sintering. Mixtures containing different
contents residue and clayed materials were prepared. For each mixture, after processing, the
physical and mechanical properties of the burned pieces were measured, with emphasis on water
absorption and linear shrinkage tests carried out as a function of the sintering temperature.
Gresification diagrams were plotted for the temperature range of 850 °C to 1150 °C. The addition of
the residue provided an increase in the porosity of the material. Light blocks were sintered and
presented adequate mechanical resistance for application as building material.
Electrical Characterization of Mullite Bodies Containing Al-Rich Anodizing Sludge
Authors: Ribeiro M.J. , Abrantes João Carlos de Castro , Labrincha Joao A.
Published: March 2009

Al-rich sludge produced from industrial anodising and surface treatment processes had
been tested in the fabrication of mullite-based materials, by using unidirectional dry pressing as
shaping technique. Mixture with common natural silica and magnesium-containing materials, like
ball clay, kaolin and diatomite were prepared in order to achieve interesting final fired refractory
and/or electrical insulating materials. Microstructural changes upon sintering and crystalline phase
evolution are detailed and their relationship with the electrical behaviour is also studied, by the use
of impedance spectroscopy. Finally, different models were used to fit the experimental electrical
resistivity values and to estimate the percolation limit of the bi-phase material.
Leaching Behaviour of a Glass Produced from a MSWI Bottom Ash
Authors: Lapa Nuno , Barbosa Rui , Camacho Susana , Monteiro Regina da Conceição Corredeira , Fernandes Maria Helena F.V. , Oliveira José Filipe Santos
Published: March 2009

This paper is mainly focused on the characterisation of a glass material (GM) obtained
from the thermal treatment of a bottom ash (BA) produced at the Municipal Solid Waste (MSW)
incineration plant of Valorsul. By melting the BA at 1400°C during 2 hours, and without using any
chemical additives, a homogeneous black-coloured glass was obtained. The thermal and mechanical
properties of this glass were characterised. The thermal expansion coefficient, measured by
dilatometry, was 9-10 x 10-6 per °C and the modulus of rupture, determined by four-point bending
test, was 75±6 MPa, which are similar values to those exhibited by commercial soda-lime-silica
glasses used in structural applications. The chemical and the ecotoxicological leaching behaviour of
the GM were also analysed. The GM was submitted to a leaching procedure composed of 15
sequential extraction cycles. A liquid/solid (L/S) ratio of 2 l/kg was applied in each cycle. The
leachates were filtered through a membrane of PTFE (porosity: 0.45 8m). The filtered leachates
were characterised for different chemical parameters and for an ecotoxicological indicator
(bacterium Vibrio fischeri). The GM was also submitted to a microwave acidic digestion for the
assessment of the total metal content. The crude BA was also submitted to the same experimental
procedures. The GM showed levels of chemical emission and ecotoxicity for V. fischeri much lower
than those determined for the crude BA. Similar characterisation studies will be pursued with the
glass-ceramics produced by adequate thermal treatment of the glass, in order to investigate the
effect of the crystallization on the final properties.
Relaxor-Like Behavior of Self-Polarized Pb(Zr,Ti)O3 Thin Films
Authors: Suchaneck Gunnar , Deyneka Alexander , Jastrabik Lubomir , Gerlach Gerald
Published: March 2009

Self-polarized Pb(Ti,Zr)O3 thin films deposited under lead enriched conditions by multitarget reactive sputtering at low substrate temperatures are characterized by tetravalent B-site occupation of excess lead. The imaginary part of the dielectric constant of such films shows a relaxor-like behavior. Evidence of a Pb2+/Pb4+ mixed valence is given by the temperature and frequency dependence of the ac conductivity. PbO volatility starts to deplete the growing film at a
critical temperature of 500°C and Pb4+ formation disappears.
Synthesis and Dispersion of PZT Ultra-Fine Powders
Authors: Wu Ai Ying , Van Genechten Dirk , Vilarinho Paula M. , Van Bael Marlies K.
Published: March 2009

In the current work two different routes, an alkoxide based sol-gel and an aqueous
solution-gel route, were used to synthesize PZT (30/70) powders. The phase purity, morphology and particle size of both were studied by XRD, TEM and particle size analysis. The dispersion behavior of the powders in water was investigated by means of light scattering particle size analyzer and zeta potential measurements. The extent to which powder morphology, synthesis route and particle charge state relate to the resulting dispersion behaviour was established. Alkoxide sol-gel
derived powders are better dispersed in aqueous media than aqueous solution-gel derived powders.
The Study of High Temperature Annealing of a-SiC:H Films
Authors: Zhang Shibin , Hu Z. , Raniero Leandro , Liao X. , Ferreira Isabel , Fortunato Elvira , Vilarinho Paula M. , Pereira Luís , Martins Rodrigo
Published: March 2009

A series of amorphous silicon carbide films were prepared by plasma enhanced chemical vapor deposition technique on (100) silicon wafers by using methane, silane, and hydrogen as reactive resources. A very thin (around 15 Å) gold film was evaporated on the half area of the a- SiC:H films to investigate the metal induced crystallization effect. Then the a-SiC:H films were annealed at 1100 0C for 1 hour in the nitrogen atmosphere. Fourier transform infrared spectroscopy
(FTIR), X-Ray diffraction (XRD), and scanning electron microscopy (SEM) were employed to analyze the microstructure, composition and surface morphology of the films. The influences of the high temperature annealing on the microstructure of a-SiC:H film and the metal induced metallization were investigated.
Design and Analysis of the PZT-Based Piezoelectric Transformer
Authors: Kozielski Lucjan , Lisińska-Czekaj Agata , Czekaj Dionizy
Published: March 2009

Piezoelectric transformer (PT) is a combination of piezoelectric actuator and transducer, which serve as the primary side and the secondary side respectively. In the present study the disk – shaped (of 20 mm in diameter and 0.6 mm in thickness), unipoled radial mode piezoelectric transformer based on modified PZT-type solid solution was custom designed and fabricated. Different input and output area ratios of the PT were studied, namely: 21, 4, 1. The electrical
properties like voltage step-up ratio, output power and temperature rise were measured for PT operating at the first resonance frequency. With the driving voltage of 20 VRMS, the 3 W output power, 165 VRMS output voltage an temperature rise of 20 0C was obtained for PT with the input/output area ratio of 1. The voltage step-up ratio of 12.5 was obtained for PT with input/output area ratio of 21.
Dielectric Investigations and Theoretical Calculations of Size Effect in Lead Titanate Nanocrystals
Authors: Grigalaitis Robertas , Banys Juras , Lapinskas Saulius , Erdem Emre , Boettcher Rolf , Glaesel H. Juergen , Hartmann Eberhard
Published: March 2009

In this paper the dielectric properties of nanosize ferroelectric lead titanate crystals are presented. The PbTiO3 samples were prepared by pressing nanopowder into the plates and have been studied experimentally by dielectric permittivity measurements in a wide frequency and temperature range. The obtained TC dependence shows a critical change of behavior with increasing of mean nanoparticle size in a 9 nm region. The theoretical calculations based on Monte Carlo
simulation were performed to describe such behavior of this material. It was shown that taking into account distribution of nanoparticle sizes in sample is possible to describe dielectric properties of PbTiO3 nanocrystals rather well.
Microstructure Characterization and Dielectric Properties of La4Mg3W3O18 Layered Oxide
Authors: Khalyavin Dimitry D. , Senos Ana Maria R. , Mantas Pedro Q.
Published: March 2009

The microstructure development and the dielectric properties of La4Mg3W3O18 layered oxide were investigated. A strong anisotropic grain growth is revealed in ceramics sintered above 1400oC. The anisotropy of the grain reflects the anisotropic character of the crystal structure. Dielectric measurements yield a relative dielectric permittivity, ε, and a temperature coefficient of the dielectric permittivity, TC ε, to be 21 and 95 ppm K-1, respectively. The positive value of TC ε is assumed to be caused by the octahedral tilting by analogy with the behaviour of other complex ordered perovskites.
V2O5-Doped M2+Cu2Nb2O8 Compounds (M2+= Zn, Co, Ni, Mg & Ca) for Microwave Dielectric LTCCs
Authors: Pullar Rob C. , Lai Chang , Alford Neil McN.
Published: March 2009

The copper-niobates, M2+Cu¬2Nb2O8 (M2+ = Zn, Co, Ni, Mg or Ca) have good microwave dielectric properties when sintered between 985 – 1010oC, and 1110oC for CaCu¬2Nb2O8. Therefore they would be potential dielectric Low Temperature Co-fired Ceramic (LTCC) materials if they could be made to sinter below 960oC (melting point of silver). To this end, additions of 3wt% V2O5 were made to ZnCu2Nb2O8, CoCu2Nb2O8, NiCu2Nb2O8, MgCu2Nb2O8 and CaCu2Nb2O8, and their sintering and dielectric behaviour was investigated for samples fired between 800 and 950oC. Doping lowered sintering temperatures to below the 960oC limit in all cases. Doping had the general effect of reducing r, density, Qf and f, although doped CaCu2Nb2O8 had a Qf value of 9300 GHz, nearly four times that of the best undoped sample. When doped and undoped samples all fired to 935oC were compared, all doped samples had greater r and density, and all except ZnCu2Nb2O8 had a smaller f.
Poly-Si Thin Film Transistors: Effect of Metal Thickness on Silicon Crystallization
Authors: Pereira Luís , Barquinha Pedro , Fortunato Elvira , Martins Rodrigo
Published: March 2009

In this work metal induced crystallization (MIC) using nickel (Ni) was employed to obtain poly-Si by crystallization of amorphous films for application as active layer in TFTs. Ni layers with thicknesses of 0.5 nm, 1 nm and 2 nm were used to crystallize the silicon. The TFTs were produced with a bottom gate configuration using a multi-layer Al2O3/TiO2 insulator produced by atomic layer deposition (ALD) as gate dielectric. The best performances of the TFT produced
were obtained when using very thin Ni layers for the crystallization. This is attributed to a lower metal contamination and to the enhancement of grain size, as a result of the lower nucleation density achieved, when using the thinnest Ni layer. Devices that exhibit effective mobility of 45.5 cm2V-1s-1 and an on/off ratio of 5.55×104 were produced using a 0.5 nm Ni layer to crystallize the active channel area.
CVD of CrO2 Thin Films: Influence of the Deposition Parameters on their Structural and Magnetic Properties
Authors: Mota de Oliveira Ana F.S. , Silvestre António J. , Sousa Pedro M. , Conde Olinda , Rosa M. Alexandra , Godinho Margarida
Published: March 2009

This work reports on the synthesis of CrO2 thin films by atmospheric pressure CVD using chromium trioxide (CrO3) and oxygen. Highly oriented (100) CrO2 films containing highly oriented (0001) Cr2O3 were grown onto Al2O3(0001) substrates. Films display a sharp magnetic transition at 375 K and a saturation magnetization of 1.92 µB/f.u., close to the bulk value of 2 µB/f.u. for the CrO2.
Structural and Magnetic Properties of Chemically Deposited Hexaferrites
Authors: Watts Bernard Enrico , Regonini Daniele , Leccabue Fabrizio , Casoli Francesca , Albertini Franca , Bocelli Gabriele , Schmool David S.
Published: March 2009

M-type lead hexaferrites (PbFe12O19) have been prepared using sol-gel methods. Lead and iron precursors were dissolved in butoxyethanol and stabilised with acetylacetone to produce a sol with good wetting and surface coating characteristics. Powder samples were investigated to optimise conditions for the growth of thin films. The «spin on» technique was used to provide homogeneous films. X-ray diffraction and thermomagnetic analysis vibrating sample magnetometry
have been performed to assess phase distribution and transformation. The results show that the hexaferrite phase can be crystallised above 700 °C and that for the first indication that this phase is metastable in air below 650 °C.
Analysis of Phase Transitions in La and Nd Substituted YIG with Magnetic Disaccommodation Measurement
Authors: Hernández-Gómez Pablo , Torres Carlos , de Francisco Carlos , Iñiguez José Ignacio , Perdigão João M.
Published: March 2009

The magnetic disaccommodation on polycrystalline Nd doped YIG NdxY3-xFe5O12
(0<x<2.5) and La doped YIG LaxY3-xFe5O12 (0<x<0.7) is studied in this work. A different behaviour with the sintering atmosphere and the dopant has been observed. For Nd doped garnets sintered in air the characteristic peak of disaccommodation in YIG shifts from 120 K to 100 K; for x=2.0 an additional 300 K peak is observed, due to the presence of magnetite in the sample, thus
indicating that phase transition has been reached. In CO2 sintered samples, the process at 120 K exhibit magnetic accommodation features and the phase transition takes place at a lower doping rate. On the contrary, CO2 sintered La doped samples do not show magnetic accommodation as Nd doped YIG, but normal disaccommodation processes, with the solubility limit observed at x=0.3,
whereas in air sintered samples the phase transition is not observed with disaccommodation measurements.
Characterization of Nickel Implanted α-Al2O3
Authors: Marques Carlos , Franco Nuno , Silva Rui Coelho da , Wemans André , Maneira Manuel J.P. , Alves Eduardo
Published: March 2009

Optical and structural properties of single crystalline α-Al2O3 were changed by the
implantation of high fluences of Ni ions. Sapphire single crystals with <0001> orientation were implanted at room temperature with 150 keV nickel ions. Implantation fluences were in the range 0.3×1015 to 1.8×1017 cm-2. After implantation the optical absorption spectra reveal the presence of a band peaking in the region 300 - 500 nm, depending on the retained fluence. This is usually related to the presence of metallic particles. X-ray diffraction (XRD) studies show the presence of metallic
Ni after implantation. Annealing in oxidizing atmosphere promotes the ecrystallization of the host matrix along with the formation of NiAl2O4 as deduced from Rutherford Backscattering Spectrometry (RBS) and confirmed through XRD. In vacuum the particles formed are metallic like with some Ni spinel also present. The control of the implantation fluence, temperature and annealing atmosphere allows tailoring the component phases.
Effect of Wheel Speed and Boron Content on Microstructure and Crystallographic Texture of Boron Substituted Sm-Co Melt Spun Ribbons
Authors: Makridis Sofoklis S. , Pavlidou Eleni , Neudert A. , McCord J. , Schäfer Rudolf , Hadjipanays George C. , Niarchos Dimitris , Stubos Athanasios K.
Published: March 2009

The Sm(Co0.71Fe0.1Cu0.12Zr0.04B0.03)7.5 (2:17 type magnet) melt spun ribbons have been produced from bulk as cast samples at low (5 m/sec) to medium (40 m/sec) wheel speed by the melt spinning technique. The crystallographic texture on wheel side, the microstructural characteristics
and magnetic properties have been investigated. The soft magnetic fcc-Co forms a very high degree of texture especially at low velocities but for the first time a degree of texturing has been remarked on fcc-Co grains. Diffraction patterns have been traced by x-ray scattering using Cu-Kα radiation on the wheel and free side of the ribbons. In the pattern of ribbons which have been produced at 5 m/sec the (002) plane of fcc-Co is almost the dominant peak while at 40 m/sec this peak diminishes
in parallel to the appearance of the structure type TbCu7 and (111) plane of fcc-Co structure. Scanning electron microscopy on the wheel side of the ribbons has been used to observe microstructural characteristics and showed that the formation of texture is attributed to the appearance of dendrites, with their long axis parallel to the longitudinal direction of the ribbons. Dendrites’ density depends on the wheel speed of the roller and boron content. It decreases as the velocity increases while for constant velocity of about 40 m/sec, higher boron content stabilizes
higher degree of texturing. Magnetic properties are also examined from low to medium wheel speed by also using the magnetooptical Kerr microscopy. Therefore coercive field as high as 3.4 kOe and reduced remanence (mr) of ~0.76 has been detected from the hysteresis curve for as spun Sm Co0.71Fe0.1Cu0.12Zr0.04B0.03)7.5 ribbons at 5 m/sec.
Local Vibrations of Substitutional Carbon in SiGe Alloys
Authors: Khirunenko Lyudmila I. , Pomozov Yu.V. , Sosnin Mikhail G. , Torres Vitor , Coutinho João A.P. , Jones R. , Abrosimov Nikolay V. , Riemann H. , Briddon Patrick R.
Published: March 2009

The influence of Ge content on the local vibrational mode of substitutional carbon in Si-rich Si1-xGex single crystals has been investigated by infrared Fourier-transform spectroscopy and ab initio modeling methods. Czochralski-grown Si1-xGex samples doped with boron and carbon have been studied. The Ge fractional content was varied from x=0.004 to x=0.044. To reveal the CS-related absorption band in the Si1-xGex the difference spectra between carbon-lean and carbon-reach Si1-xGex samples with the same Ge content were studied. We have found that the CS-related absorption band in the Si1-xGex alloys red-shifts and broadens with increasing Ge content. It has been found that at x0.015 the CS absorption band consists of two overlapping lines corresponding to different combinations of Si and Ge atoms neighboring the CS atom. The calculations show that substitutional carbon atoms avoid Ge ligand atoms, and should be found in Si-rich regions. These results also reveal that the softening of the CS mode frequency arises from the SiGe volumic expansion.
Structural and Optical Characterization of Light Emitting InGaN/GaN Epitaxial Layers
Authors: Pereira Sergio , Correia M.R. , Alves Eduardo
Published: March 2009

This paper concerns the structural and optical properties of the group III-V
semiconductor alloy, indium gallium nitride (InGaN). We focus on the reasons of interest to study InGaN. Recent advances regarding the basic understanding (ex. accurate composition determination) and some yet unclear issues (ex. phase separation) regarding this material system, are also briefly discussed. Illustrative results on the light emitting and structural properties are presented.
Investigations of Membrane Electrolytes for PEM Fuel Cell Applications
Authors: Bujlo Piotr , Halama Agnieszka , Paściak Grzegorz , Chmielowiec Jacek
Published: March 2009

The work concerns new polymeric materials for electrolytes synthesized at the
Electrotechnical Institute. Poly(styrene-4-sulfonate)-grafted poly(vinylidene fluoride) (PVDF-g- PSSA) membranes proton-exchange membranes were synthesised by free radical graft polymerization of polystyrene into PVDF films (50 *m thick) followed by sulfonation. Physical and electrochemical properties of that membranes were investigated. The membranes were tested as electrolytes in a single cell configuration system. The influence of working condition, as gas
humidity and cell temperature on fuel cell performance were measured. Obtained performances were lower in comparison with commonly used electrolyte materials. At this stage of development the synthesized materials are not suitable for fuel cell application. The results gave authors information for selection membrane with the best parameters and chemical process configuration.