bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Stability of Mechanical Properties of Copper after Equal-Channel Angular Pressing
Authors: Kravchenko Tamara , Korshunov Alexander , Zhdanova Natalia , Polyakov Lev , Kaganova Irina
Published: March 2009

Annealed oxygen-free and tough-pitch copper samples have been processed by equalchannel
angular pressing (ECAP) by route BC. The samples included 8 x 8 mm section pieces and a
40 mm diameter bar. Thermal stability was assessed based on the changes in the standard
mechanical properties (conventional yield strength, tensile strength, elongation, proportional
elongation and contraction) after annealing at different temperatures for 1 hour.
Thermal stability of the same grade of material has been found to be different for different
batches and to depend on the structural conditions of deformed material. The zone of thermal
stability for copper of the two grades of interest does not depend on the material’s chemical
composition.
Friction Properties of Steel Fibre Reinforced Epoxy Composites Used in Moulding Blocks of Hybrid Moulds
Authors: Sabino-Netto Aurélio C. , Salmoria Gean V. , Ahrens Carlos H. , Pouzada António Sergio
Published: March 2009

Rapid tools for injection moulding are often produced by casting of epoxide filled
composites. The moulding blocks obtained in this way are likely to undergo wear especially at the
surfaces of the moulding cores during the ejection phase. In this study, tribological properties of
epoxide composites containing different volume fractions of short steel fibres used in moulding
blocks were assessed. Friction tests with the composites and moulded polypropylene were carried
out with a prototype equipment that reproduces the actual ejection phase of injection moulding. The
friction data were interpreted in terms of the roughness and compared with the microscopic features
of the epoxy composite surface.
Finite Element Analysis of the Thermal Residual Stresses of Diamond Cutting Tools in the Sintering Process
Authors: Reis Luís G. , Amaral Pedro M. , Li Bin , Anjinho Carlos A. , Rosa Luis Guerra , de Freitas Manuel
Published: March 2009

The main objective of the present work is to present and discuss the effects of the
residual stresses generated in the matrix. Both, elastic and elastic-plastic models using explicit finite
element code Abaqus were developed to investigate the thermal residual stresses generated around a
diamond particle embedded in a metal matrix (a binder) during the sintering process for obtaining a
diamond tool. The first part of the work consists in examining the thermal residual stress field
generated by using three sintering temperatures from which the bodies are cooled from (T1=800°C,
T2=700°C and T3=600°C) and two diamond shapes modelled with 2D axisymmetric elements, one
from a circle the other from an octagon, respectively. In this case only one type of binder showing
typical elastic behaviour is considered. The second part of this work consists in comparing the finite
element solutions using binders with different tensile behaviour (elastic vs. elastic-plastic
behaviour). This last study has used a particle shape generated from the octagon, since this shape
allows, in a great number of real situations, the simulation of a particle with a larger number of
facets, in line with what it is observed when looking at a conventional diamond tool.
Production and Behaviour of Aluminium Matrix Double Composite Structures
Authors: Kientzl Imre , Dobránszky János
Published: March 2009

In this study Nextel 440 type alumina fibre reinforced aluminium matrix composite wires
were investigated. Composite wires produced using the continuous process are suitable to simplify
the introduction of fibre reinforcements into aluminium castings as well as the production of double
composite, sandwich and preferentially reinforced structures. This paper focuses on the porosity of
composite wires because minimizing porosity is the primary condition of good mechanical
properties. Composite wires were produced with different infiltration pressure (0.83 MPa, 1.03
MPa, 1.24 MPa, 1.52 MPa, and 1.65 MPa) to determine the correlation between infiltration pressure
and the porosity of wires. 10 grinded cross-sectional samples were made from each type of
composite wires. Based on the micrographs of these samples the volume fraction of aluminium was
determined by image analysis, which also yielded information on the porosity of wires. The results
show that there is direct (linear) correlation between the infiltration pressure and the decrease in
porosity. These findings, however, are valid only for the investigated range of pressure. The
measured values were in good agreement with the theoretical model used for comparison.
Mechanical and Microstructural Characterization of Al-6082 Ultrafine-Grained Alloys Processed by ECAP Combined with Traditional Forming Techniques
Authors: Krállics György , Fodor Arpad , Gubicza Jenő , Fogarassy Z.
Published: March 2009

An Al-6082 alloy was subjected to equal channel angular pressing (ECAP) and
subsequently to conventional forming methods such as shape rolling and rotary forging. The effect
of different deformation techniques on the microstructure and the mechanical properties was
studied. It was found that the shape rolling and rotary forging increased further the strength of
ECAP-processed samples and induced a loss of ductility.
Evaluation of Microgravity Heat Conductivity Measurements with FLUENT System
Authors: Bánhidi Viktor
Published: March 2009

Microgravity experiments were executed to measure the convection free, pure heat
conductivity and heat diffusivity parameters in molten metals. The application of well known
numerical methods to evaluate the data collected under low gravity conditions was only partially
successful. None of the methods (Crank-Nicolson, error function fitting or simple FEM model)
could be used over the whole measured temperature range. The purpose of this work was to
alleviate the previously experienced problems by using a commercially available finite value
method package on high performance computers, to simulate the coupled thermal and fluid
mechanical model in order to accurately determine the heat transport properties of Ga, Sn-Bi, Sn
and Zn melts, and by incorporating device geometry data, compare the results to the values gathered
from short time microgravity experiments.
Failure Analysis Methods in Electronics Assembly Technology
Authors: Balogh Bálint , Gordon Péter , Kovács Róbert , Nagynémedi Csaba , Szabó Péter János , Harsányi Gábor
Published: March 2009

The aim of this paper is to describe a failure analysis methodology applicable to reveal
the root causes of electronic assembly failures. The most relevant properties of the applied
techniques, i.e. optical microscopy, X-ray microstructure analysis, SEM (scanning electron
microscopy) combined with EDX (energy dispersive X-ray spectroscopy) analysis, are given. Three
recent failure analysis case studies are also presented. In case of a burnt component the microwire
and the leadframe formed AlCu intermetallic compound in the length of several millimeters. The
low joint strength of gullwing leads were deduced back to paste printing and wetting problems. The
fracture surface morphology of a joint broken on the field showed different structure from the ones
broken at room temperature. It was revealed that SnPb solder fracture surface is different at room
temperature and above 100°C.
Estimation and Consequences of Shrinkage of Steel
Authors: Réger Mihály , Kytönen Heli , Verő Balázs , Szélig Árpád
Published: March 2009

Industrial data set with 400 CC steel slabs were analysed by a statistical method for
revealing the real connections between the technological parameters, heat transfer model results and
the precisely determined centerline segregation index. Because of the poor correlations a new model
was developed in which the shrinkage and deformations of the shells of the slabs can also be taken
into account. It has been proved that the stopping of liquid movement below about 30 % liquid ratio
plays an important role in the centerline segregation formation. The conclusions of the calculations
are in good accordance with the results of the metallographical analysis.
Investigation of Performance of Superplasticizing Admixtures Used in Hungarian Building Industry
Authors: Takács Márton , Nemoda Ferenc
Published: March 2009

Concrete is the strongest candidate to be the most important construction material of the
21st century. This can be ensured by the continuous research and development of new materials and
technologies regarding concrete construction. Properties of concrete can be expediently modified by
adding special chemical materials called admixtures.
In this research work effect of type and dosage of different superplasticizing admixtures
available in Hungary were investigated in detail. Standard test methods such as flow table test and
compressive test were applied to obtain effectiveness of the admixtures. Regarding the
examinations done in the course of the research, we refer to the regulations of the EU harmonized
admixture standard currently valid in Hungary MSZ EN 934-2:2002. In connection to that we will
precisely quote the requirements specified in the standard regarding superplasticizers and will also
mention the main differences compared to the plasticizer additives. Types, properties and use of
superplasticizers are introduced in detail, too. Experimental results are evaluated to rate the
efficiency in compliance with the requirements of the standard.
Si- and SiGe-Based LEDs
Authors: Sobolev N.A.
Published: March 2009

Single crystal Si, Si0.948Ge0.052 and Si0.66Ge0.34 diodes as well as Ge transistor structures
with high electroluminescence (EL) intensities in the region of interband transitions at room
temperature were fabricated by different techniques and their luminescence properties were studied.
By varying the Ge content in the solid solution, one can control the wavelength at the emission
maximum in the range of 1.1 - 1.8 μm. The integrated EL intensity varies by a factor of less than
two in the temperature ranges of 80 - 500 and 80 - 300 K for Si and SiGe LEDs, respectively. Si
LEDs can effectively operate, at least, up to ~200°C. The data analysis shows that recombination
involving excitons is the dominant mechanism of near-band-edge radiative recombination in all the
light-emitting structures at room temperature. Some of the structures have record values of EL
intensity and/or quantum efficiency, so they can be used as effective light emitters in Si
optoelectronics. In particular, Si LEDs were designed with a small p-n junction area of 8x10-3 mm2
and a radiation power of 0.3 mW. The record total emission power of 46 mW was achieved in solar
cell LEDs with an emitting surface area of 3 сm2. The internal quantum efficiencies of 0.5% and
0.3% were recorded in Si0.948Ge0.052 and Si0.66Ge0.34 LEDs at the wavelengths of 1.15 and 1.3 μm,
respectively. Room temperature near-band-edge EL was first observed in Ge structures.
A Comparative Study between Low and High-Energy Milling Processes for the Production of HD PrFeCoBNb Sintered Magnets
Authors: Périgo E.A. , Soares E.P. , Takiishi Hidetoshi , Motta C.C. , de Faria Jr. Rubens Nunes
Published: March 2009

Roller-ball milling (RBM) or planetary ball milling (PBM) have been used together with
the hydrogen decrepitation (HD) process to produce sintered permanent magnets based on a mixture
of Pr16Fe76B8 and Pr14.00Fe63.90Co16.00B6.00Nb0.10 magnetic alloys. Five distinct compositions have
been studied comparing low- and high-energy milling. Magnets with a particular composition and
prepared using these two routes exhibited similar magnetic properties. Modifications have been
carried out in the procedure of the HD stage for PBM in order to guarantee a high degree of
crystallographic alignment. Pr15.00Fe69.95Co8.00B7.00Nb0.05 magnets showed the best maximum energy
product for both processing routes (~ 247 kJm-3). A significant reduction in the milling time (93%)
has been achieved with high-energy processing, the greatest advantage over the low-energy route.
Effect of Co Addition on Sintering and Electrical Properties of Yttria-Stabilized Zirconia
Authors: Silva G.C.T. , Muccillo E.N.S.
Published: March 2009

Yttria-stabilized zirconia is the most developed solid electrolyte for use in hightemperature
solid oxide fuel cell (SOFC). Commercial yttria-stabilized zirconia powders reach high
densification at temperatures around 1400 °C. The use of additives may increase the densification
rate by means of a liquid phase formation during sintering. However, these additives should not
cause any degradation on the ionic conductivity of the electrolyte. The main purpose of this work
was to study the effect of Co addition on the densification and electrical conductivity of yttriastabilized
zirconia. Green compacts were prepared by pressureless sintering a mixture of
commercial 8 mol% yttria-stabilized zirconia with cobalt carbonate. Linear shrinkage results show
that the temperature at which the shrinkage starts decreases with increasing Co content. Impedance
spectroscopy measurements reveal that Co additions to stabilized zirconia decrease the total
electrolyte conductivity even for Co contents as low as 0.05 mol%.
Sintering of B4C-SiC Powder Obtained In Situ by Carbothermal Reduction
Authors: da Rocha Rosa Maria , de Melo Francisco Cristóvão Lourenço
Published: March 2009

Boron carbide (B4C) and silicon carbide (SiC) are materials with high hardness and low
density what make them very useful in various applications, such armor plates. Hot press sintering
of B4C-SiC composites was studied. The powder mixture was obtained in situ by carbothermal
reduction using B2O3, SiO2 and carbon black as precursors. Seeds of commercial B4C and SiC were
used to accelerate the synthesis reaction. Compositions were prepared to obtain powders after
carbothermal reduction with 10, 30 and 50 wt% of SiC. Carbothermal reaction was conducted in
argon atmosphere at temperatures up to 1700 °C. The synthesized powders were analyzed by DRX
and SEM. Hot pressing at 1850 °C/30 min (20 MPa) in argon atmosphere was applied. Densities
higher than 93% of theoretical density and microhardness of 34 GPa were achieved for hot pressed
samples.
Evaluation of the Performance of α-SiAlON Tool when Turning Ti–6Al–4V Alloy without Coolant
Authors: Souza José Vitor C. , Nono Maria do Carmo de Andrade , Mineiro Sergio Luiz , Ribeiro M.V. , Silva Olivério Moreira Macedo
Published: March 2009

Due to their high hardness and wear resistance, Si3N4 based ceramics are one of the most
suitable cutting tool materials for machining cast iron, nickel alloys and hardened steels. However,
their high degree of brittleness usually leads to inconsistent results and sudden catastrophic failures.
This necessitates a process optimization when machining superalloys with Si3N4 based ceramic
cutting tools. The tools are expected to withstand the heat and pressure developed when machining
at higher cutting conditions because of their high hardness and melting point. This paper evaluates
the performance of α-SiAlON tool in turning Ti–6Al–4V alloy at high cutting conditions, up to
250 m min−1, without coolant. Tool wear, failure modes and temperature were monitored to access
the performance of the cutting tool. Test results showed that the performance of α-SiAlON tool, in
terms of tool life, at the cutting conditions investigated is relatively poor due probably to rapid
notching and excessive chipping of the cutting edge. These facts are associated with adhesion and
diffusion wear rate that tends to weaken the bond strength of the cutting tool.
Precursor Influence on the Obtention of β-SiC Hollow Fibers
Authors: Carvalho Luiz Eduardo , Florian Marcio , Cairo Carlos Alberto Alves , de Alencastro Graça Mario Lima
Published: March 2009

SiCf/SiC composite has a high potential for applications such as thermal protection
systems due to its high oxidation resistance, high heat emissivity and low through-the-thickness
(transverse) thermal conductivity, mainly if hollow fibers are used as reinforcement phase of the
composite. PAN polymer is a precursor widely used and studied for developing high performance
carbon fibers. Most commercial carbon fibers are basically derived from PAN polymer. In this
work, the influence of the fiber specific mass on the morphology of SiC fiber obtained by
conversion reactions from PAN oxidized fiber precursor was investigated. These oxidized fibers
were obtained by controlling the time and temperature during the process of stabilization/oxidation.
An Optimisation of Scrap Agate Powder Contents in Triaxial Ceramic Bodies Using Mathematical and Statistical Strategies
Authors: Correia Sivaldo Leite , Dienstmann G. , Folgueras Marilena Valadares , Hotza Dachamir
Published: March 2009

In the present study, the waste scrap agate, obtained as a by-product of rock agate
beneficiation as decorating ends and media for wet grinding was used as inert filler in a traditional
triaxial red stoneware tiles composition. The effects on the technological properties have been
investigated. The study has been carried out using the mixtures experiments method for the
experimental design. Characterization results were used to calculate statistically significant and
valid regression equations, relating dried and fired body properties with clay, feldspar and scrap
agate contents in the unfired mixture. The regression models were then used simultaneously to
delimit the combinations of those three raw materials most adequate to produce a ceramic body
with specified properties. The use of mathematical optimisation shown that, for the particular raw
materials under consideration, there is a rather forgiving composition range of clay (20-68 wt.%),
feldspar (17-50 wt.%) and scrap agate (15-45 wt.%) contents within which it is possible to
simultaneously specify the technological requirements for triaxial red stoneware tiles bodies, not
only of the fired products but also of the intermediate materials at important stages of the
processing.
Sintering Sm2Fe17 Prior to Nitrogenation
Authors: Bahr R. , Hesse R. , Boareto J.C. , Wendhausen Paulo A.P.
Published: March 2009

The sintering of Sm2Fe17 compound prior to the nitrogenation process is studied as an
alternative process to produce dense Sm2Fe17N3 hard magnets with higher maximum energy
products (BH)max than conventional polymer bonded magnets. In order to optimize sintering and
nitrogenation processes, powders made from alloys, with different compositions, in the as-cast as
well in the as-homogenized state were used. It could be shown that the amount of α-Fe, formed in
the casting process, was reduced during sintering and that Sm selective loss is restricted to the
surface up to a depth of 100 +m. Moreover the density of the sintered samples was not much
affected by the initial composition or by the prior homogenization of the alloys. Although the
nitrogenation process was successful in producing the Sm2Fe17N3 as proved by the mass gain,
magnetic properties measurements and X-Ray diffraction, the hard magnetic properties were much
lower than expected, indicating that other variables, which are discussed in the text, must be
considered.
The Coercivity Mechanisms in Sm(CoFeCuZr)z Nanocrystalline Magnets: Nucleation x Pinning
Authors: de Campos Marcos Flavio
Published: March 2009

It is discussed the difference between the magnetic reversal mechanisms: i) coherent
rotation, ii) nucleation, iii) unpinning of domain walls. The main argument to suggest pinning as
the coercivity mechanism of Sm(CoFeCuZr)z magnets is the low initial susceptibility of
magnetization curves of thermally demagnetized magnets. However, coherent rotation also implies
in low initial susceptibility, since the grain size of the magnets is near the single domain particle
size. It is unlikely that pinning could be the coercivity mechanism in this case, since the anisotropy
field of Sm2Co17 phase is 65 kOe, whereas the coercivity of magnets can be higher than 40 kOe.
Such coercive field of 60% of the anisotropy field indicates coherent rotation as mechanism. A
model for describing the abnormal coercivity behavior in Sm(CoFeCuZr)z magnets is proposed.
Looking for an Ideal Particle Size for Apatite Flotation
Authors: Santana R.C. , Farnese A.C.C. , Ceolin S.P. , Domingues R.C. , Fortes M.C.B. , Ataíde Carlos Henrique , Barrozo Marcos A.S.
Published: March 2009

Today, the phosphate rock processed in the world represents around some 20 billion
dollars per year. Some exploitable deposits are characterizing by low grade phosphate rocks,
composed of the apatite group in association with a wide assortment of accessory minerals. Usually
a combination of beneficiation techniques is used to process a phosphate rock since run of mine,
and then a flotation is applied to recovery apatite. This work proposes an evaluation of particle size
for apatite recovery by column flotation in bench-scale. The variables collector dosage and
depressant dosage were investigated experimentally applying a factorial design. According to the
experimental results, the particle size range between 37&m and 105&m is an optimum size used to
obtain simultaneously a product with the industry demand grade (at least 33%) and phosphorus
recovery, upper than 60%.
Porous Alumina-Zirconia Prepared by Foam Technique for Applications as Cooling Systems of Artificial Satellites
Authors: Hirschmann Ana Coh O. , Nono Maria do Carmo de Andrade , Riehl R.R. , Silva Cosme Roberto Moreira
Published: March 2009

The interest in porous ceramics has increased concurrently with new processes and new
applications. This material has been used in several industrial applications such as filters, catalysis
and sensors. The objective of the present investigation was to produce porous alumina with 3 % mol
yttria stabilized zirconia in tetragonal crystalline structure (Y-TZP). This material will be used in
cooling systems of satellites, due to its mechanical properties and chemical inertia. To obtain the
porous ceramics was used the direct foaming technique, which is a method based on the preparation
of a stable foam slurry and a slurry of alumina and zirconia that are later mixed and blended for
incorporation of air in the mixture. The sintered ceramics was characterized by scanning electronic
microscopy, mercury porosimetry and permeability measurements. The porous Al2O3–ZrO2
ceramics obtained showed high porosity and uniform microstructure with 20–100 ,m open pores.
The results from these alumina zirconia composites showed a potential to apply in heat pipes.
Synthesis of Core/Shell Type of Hybrid Magnetic Particle by Using Polyionic Copolymer with Extra Magnetic Field
Authors: Wang Cheng Chien , Chen I Han , Lin Chun Rong , Chen Chuh Yung
Published: March 2009

The core/shell type of cobalt ferrite nanocluster formed on the surface of the ionic
copolymer microsphere was prepared by in-situ co-precipitation method. The low treatment
temperature at 90°C with an external magnetic field (0.5T) was used instead of the traditional high
temperature annealing procedure. Interestingly, the crystalline structure and saturation
magnetization of cobalt ferrite nanoclusters preparing with extra magnetic field are better than that
of no extra magnetic field from the XRD and VSM verification. Furthermore, the hollow sphere
type of magnetic particle can be obtained when the ionic copolymer is extracted from the core/shell
nanocomposite by using tetrahydrofuran solvent with supersonic oscillation.
Underfill Injection Molding in Flip-Chip Packaging with Different Bumps Array Arrangements
Authors: Lin Chao Ming , Chu Chun Yi , Chang Wei Lin
Published: March 2009

The injection molding IC packaging process involves chip packaging and encapsulation
techniques comprising mainly of cavity-filling and curing processes. In this paper, the complex 3D
geometries and flow behaviors are simplified and modeled by a 2.5D thin-shell simulation.
Important aspects of the cavity-filling process include the choosing of bumps array types, the cavity
geometry, the injection process, the packing pressure, and the process temperature. The current
investigation considers the filling and curing in the different bumps array types. It is shown that
the applicable array arrangement provides improved filling results on the flow front, curing, shear
strain-rate and velocity vector distributions. These results show the better choice using the geometry
parameters in the bumps array arrangement is to consider the performances of the local and global
penetrations together.
Reliability of SnAgCu Alloys for CMOS Image Sensor QFN Package under Thermal Cycling Loading
Authors: Hsu Hsiang Chen , Lee Hui Yu , Shieh Wen Lo
Published: March 2009

A three-dimensional finite element model of CMOS image sensor QFN packaging using
ANSYS codes is developed to investigate the solder joint reliability under thermal cycle test. The
predicted thermal-induced displacements were found to be very good agreement with the Moiré
interferometer experimental in-plane deformations. The developed finite element model is then
applied to predict fatigue life of Sn4.0Ag0.5Cu, Sn3.5Ag0.5Cu and Sn3.9Ag0.6Cu alloys based on
JEDEC standard JESD22-A104. In order to save computational time and produce satisfactory results
in the region of interest, an independent more finely meshed so-called submodel scheme based on
cut-boundary displacement method is generated. The mesh density for different area ratio of
refinery/coarse model was verified and the results were found to be good agreement with previous
researches. The modified Coffin-Manson equation and strain energy density based equation are
applied to evaluate the reliability of SnAgCu alloys. A series of comprehensive parametric studies
were conducted in this paper.
The Influence of Sintering Temperature on the Performance of Dye-Sensitized Solar Cell
Authors: Chou Chuen Shii , Yang Ru Yuan , Weng Ming Hang , Yeh Chun Hung
Published: March 2009

This study investigated the effect of the sintering temperature on the performance of a
dye-sensitized solar cell (DSSC). A nanocrystalline TiO2 layer was fabricated on the ITO
substrate using the doctor blade technique, and the working electrode was then sintered in a
high-temperature furnace. The working electrode with a TiO2 thin film was immersed in the
solution of the CuPc dye (copper phthalocyanine 32 16 8 C H CuN ) powder for 12 hours. Finally, the
DSSC was assembled, and the short-circuit photocurrent and the open-circuit photovoltage of
DSSC were measured using a home-made I-V measurement system. The short-circuit
photocurrent significantly increases from 8.02 to 16.85 μA as the sintering temperature increases
from 165 to 550 C  . Furthermore, the open-circuit photovoltage substantially increases from
0.084 to 0.42V as the sintering temperature increases from 165 to 550 C  .
Simulation of Cooling Process of Medium Thickness Steel Plate
Authors: Han Ji Guang , Bai Yang
Published: March 2009

By carefully researching and analyzing on cooling process of medium thickness steel
plate, a mathematics model of heat transfer and its corresponding simulation model are established
and evaluated with finite discrimination for a selected cooling object, and a simulation model is
established. Through simulation and locate testing, the calculated values obtained are agreed very
well with the measured ones. This indicates that the simulation model can preferably reveal the
accelerated cooling process of medium thickness steel plate and can be applied to guide the
manufacture of medium thickness steel plate.
Robust Estimation Design of a Class of Systems with Noise Coupling Input Saturation
Authors: Chen Yung Yue , Chang Shyang Jye , Shen Sheng Chih , Chen Yung Hsiang
Published: March 2009

An investigation about the robust estimation of a class of systems with noise coupling
input saturation is presented in this study. In general, the existed estimation algorithm is based on
the exactly known of the input saturation, but in fact, this is not always true in some practical cases
because of the coupling of input saturations and input noises. For treating these kinds of coupling
problems in the state estimations of systems, in this study, one fuzzy-based robust estimation
algorithm is proposed. The proposed robust estimator includes two parts: firstly, a regression form
fuzzy system that is adopted to approximate the unknown input saturation, and then, a robust
estimator that combines the above fuzzy system by robust filter design concept for eliminating the
effects of noises and modeling uncertainties is proposed. This combination of fuzzy approach and
robust filtering technologies successfully offers one a more simple and practical method for treating
the estimation problem of a class of systems that input saturations and input noises couple together.
Impedance Spectroscopy Applied to Metal Corrosion Study in Silicate Melts
Authors: Rapin Christophe , Podor Renaud , Gassert J. , Vilasi Michel
Published: March 2009

The determination of the corrosion processes of metallic materials in glass melts is of
great interest for glass makers. Our attention has been specifically focussed on Cr-bearing alloys
that form Cr2O3 layers when they are immersed in a silicate melt and offer a good resistance to melt
corrosion. The comprehension of the corrosion processes has been extensively studied in the last 10
years using stationary electrochemical techniques. Results relative to the thermodynamic state were
described. Complex impedance spectroscopy offers the possibility to determine the reaction kinetics
in terms of limiting processes.
Three chromium rods were directly immersed in molten glass at T=1050°C, maintained respectively
in the active, passive and transpassive state and studied using electrochemical techniques. The
results that are reported in this paper show a good agreement between complex impedance
spectroscopy data, scanning electron microphotographies of the glass/metal interface and previous
results obtained using stationary electrochemical techniques.
In Situ Thermal Gradient Controlled Investigation of Spallation -Experimental Design and Preliminary Results
Authors: Sniezewski Julien , Le Maoult Yannick , Lours Philippe
Published: March 2009

Based on a coupled numerical and experimental approach, the design and implementation
of an in situ thermal-gradient-controlled cyclic oxidation test, dedicated to the investigation of the
TGO and TBC spallation, is presented. The influence of the specimen through thickness thermal
gradient as well as the benefits of the video real-time monitoring of the cooling phase of an
oxidation test is discussed in the case of the spallation of an alumina scale grown on FeCrAl alloys.
Photoelectrochemical Characterisation of Chromia Scales Thermally Grown on Various Metal Substrates
Authors: Wouters Yves , Galerie Alain , Petit Jean Pierre
Published: March 2009

Chromia scales grown on several chromia-forming metallic substrates in various
conditions were characterised by photoelectrochemistry (PEC), highlighting the presence of two
semiconductor phases signed by their respective bandgaps (3.0 and 3.5 eV) with variations of
semiconduction type (n, p and insulator, more or less doped). The protective character of the scale
was clearly demonstrated when the highest bandgap phase (3.5 eV), identified as the external
subscale was close to an insulator.
Effects of Water Vapour on the Oxidation of Chromia Formers
Authors: Young David J.
Published: March 2009

Water vapour interacts with growing chromia scales in several different ways. Formation
and volatilisation of Cr2O2(OH)2 is shown to account quantitatively for chromium loss from thin
alloy foils reacted with air-steam mixtures over periods of 103 h. In the shorter term, water vapour is
shown to refine the grain structure of Cr2O3 scales grown on Ni-25Cr. Scaling kinetics are at the
same time accelerated by an additional, larger contribution to diffusion by a grain boundary species,
either OH- or H2O. A slight increase in scaling rate observed at low water vapour partial pressures
in H2/H2O gases is thought to be due to hydrogen doping.
A Novel Duplex Re-NiW Based Diffusion Barrier on a Nickel-Base Superalloy for TBC Systems
Authors: Mercier Sebastien , Boivin Denis , Bacos Marie Pierre , Josso Pierre
Published: March 2009

A diffusion barrier between a 4th generation superalloy (MC-NG) and a β-(Ni, Pt)Al has
been studied. The used coating process combines Re and NiW electrolytic deposits followed by
thermal treatments. The diffusion barrier is composed of a continuous 3 &m thick ReWNi layer
under a 10 &m thick β-(Ni, Pt)Al containing W rich precipitates. EDS analysis on as coated samples
and on 50h-1100°C-Ar aged samples showed that the Re-NiW layer works as a diffusion barrier.
The Al reservoir in the bond coat after aging is higher with the diffusion barrier than without. The
concentrations of alloying elements are also lower in the bond coat with the diffusion barrier than
without.
Improvement of High-Temperature Oxidation of Titanium Alloys by Dipping in a Phosphoric Acid Solution
Authors: Brou S.Y. , Bonnet G. , Grosseau-Poussard Jean Luc
Published: March 2009

Gamma-TiAl samples were treated by phosphoric acid solutions at different
concentrations. With 15 mol/dm3, a viscous deposit was left on the surface leading, after drying and
high temperature oxidation, to a very heterogeneous surface aspect. Concentrations below 0.5
mol/dm3 were then used and allowed to greatly ameliorate the homogeneity of the superficial layer.
After heating from ambient to oxidation temperature, however, cracks were always observed, due to
the departure of gaseous molecules. Isothermal oxidation tests come out at 800°C and 900°C under
reconstituted air showed that weight gains were strongly reduced when TiAl had been treated. A
compound containing titanium, oxygen and phosphorus was detected at the end of the heating
period, identified as titanium pyrophosphate, TiP2O7. This compound remained the only one
detected for 100 h when oxidation was come out at 800°C, but evolved towards TiO2 when
oxidation time was increased. In the case of oxidation at 900°C, the evolution from TiP2O7 to TiO2
also happened but appeared to go faster.
Elaboration of Nickel Aluminide Diffusion Coatings: Application to Oxidation Resistance
Authors: Choux Céline , Chevalier Sébastien , Cadoret Yannik
Published: March 2009

Aluminide diffusion coatings are widely used in aeronautic domain. Nickel based
superalloys present good mechanical properties and creep resistance at high temperature but their
corrosion resistance is somewhat poor. In order to enhance their lifetime at high temperature,
aluminide coatings can be applied on alloy surface. Aluminium present on material surface can
form, at high temperature, alumina scale which is a protective oxide scale. In the present study,
nickel aluminide coatings were carried out by aluminisation in a single step pack cementation
process on nickel based superalloys 600 and AM1. Ni-Al intermetallic was obtained in each case.
Oxidation tests were carried out at 900°C in air under atmospheric pressure. At this temperature,
transient alumina as γ-Al2O3 and θ-Al2O3 appear on surface and are less protective than the stable α-
Al2O3. Reactive elements can enhance α-Al2O3 nucleation and change diffusion mechanism during
oxidation leading to a better adherence of alumina scale. In the present work, yttria was introduced
by Metal-Organic Chemical Vapour Deposition (MOCVD) prior to the aluminisation. Yttria doped
and undoped sample behaviours were compared under oxidising atmospheres.
Thermodynamic Modelling of the Destruction of the Surface Cr2O3 on Alloy 230 in the Impure Helium Atmosphere of a Gas Cooled Reactor
Authors: Rouillard Fabien , Cabet Céline , Gossé Stéphane , Wolski Krzysztof , Pijolat Michèle
Published: March 2009

Above a given temperature called TA, the chromium rich oxide which has been
developed on the surface of Haynes 230® and model NiCrWC alloys at a lower temperature
becomes unstable in impure helium: carbon monoxide is released. Actually, oxide is reduced by
carbon from the alloy. A thermodynamic model is developed to rationalize the variation of TA as a
function of the partial pressure of CO in the gas phase. It was found that, at the early stages of the
scale reduction, the relevant reaction occurs at the oxide/metal interface between chromia and
carbon from the alloy. The interfacial activity of carbon in the alloy can be calculated based on
measurements of the interfacial weight percentage of chromium and using ThermoCalc® software.
Excellent agreement is observed between experimental values of TA and theoretical predictions.
Chemical Evolution in the Substrate due to Oxidation: A Numerical Model with Explicit Treatment of Vacancy Fluxes
Authors: Bertrand Nathalie , Desgranges Clara , Nastar Maylise , Girardin Gouenou , Poquillon Dominique , Monceau Daniel
Published: March 2009

To get a better understanding of oxidation behavior of Ni-base alloys in PWR primary
water, a numerical model for oxide scale growth has been developed. The final aim of the model is
to estimate the effects of possible changes of experimental conditions. Hence, our model has not
been restricted by the classical hypothesis of quasi-steady state and can consider transient stages.
The model calculates the chemical species concentration profiles, but also the vacancy
concentration profiles evolution in the oxide and in the metal as a function of time. It treats the
elimination of the possible supersaturated vacancies formed at the metal/oxide interface by
introducing a dislocation density at the interface and in the metal bulk. This latter density can be
related to the cold-working state. Its effect on the vacancy profile evolution is studied in the case of
a pure metal. Eventually an extension of the present model to the oxidation of Ni-base alloys is
discussed regarding a recent vacancy diffusion model adjusted on Ni-base alloys.
High Temperature Oxidation of Fe-9Cr-1Mo Steel in Liquid Metal
Authors: Martinelli Laure , Balbaud-Célérier Fanny , Picard Gerard , Santarini Gerard
Published: March 2009

The oxidation mechanism of the T91 martensitic steel in oxygen-saturated Pb-Bi eutectic
at 470°C has been investigated to develop a long term predictive model of the steel oxidation
kinetic. This work is performed in the frame of life duration studies carried out for the MEGAPIE
spallation module demonstrator dedicated to the feasibility demonstration of an hybrid reactor.
Our scientific approach has been based on an experimental characterization of the oxide scales and
of the T91 steel oxidation kinetics. From these experimental results, an oxidation mechanism has
been elaborated and then simulated.
The oxide scale formed at the T91 surface has a duplex structure, constituted of an external
magnetite scale and an internal Fe-Cr spinel scale. A scale growth mechanism has been proposed:
the magnetite scale growth seems to be limited by the iron lattice diffusion inside the duplex oxide
scale. At the same time, a self-regulation mechanism seems to govern the Fe-Cr spinel scale growth.
This mechanism consists of a non-limiting oxygen diffusion step, which is carried out, across the
oxide scale, inside liquid lead nano-channels and a limiting iron oxide lattice diffusion step.
Considering the proposed oxidation mechanism, a simulation of the growth of the two oxides scales
has been carried out and compared to the experimental oxidation kinetics. The excellent agreement
between the experimental results and the simulations supports to accept the proposed mechanism,
leading to prediction of kinetics for long oxidation durations.
An Expert Software for Multi-Layer Coatings Design in Surface Engineering
Authors: Bondoux Céline , Degrandcourt Christophe , Ailinca George , D'Ans Pierre , Degrez Marc , Wathelet Denis , Barthelemy François , Anciaux Julie , Ospina Gustavo , Jacquet Jean Marie
Published: March 2009

For the first time, a unique expert system able to give assistance to designers in surface
engineering has been built. Not only is this software able to provide multi-layer coating solutions,
but it is also able to rank different solutions according to their technico-economical interest. In
addition to its ability to solve corrosion and wear concerns, it is also able to deal with surface
finishing properties (like brightness, weldability, electrical conductivity, biocompatibility, …). This
paper describes the structure of this expert system together with its main operation principles and
future developments.
Oxidation of Stoichiometric Nickel Ferrites Used as Inert Anodes for Aluminium Electrolysis in Molten Cryolite Mixtures
Authors: Cassayre Laurent , Chamelot Pierre , Arurault L. , Massot L. , Taxil Pierre
Published: March 2009

Thanks to their good electronic conductivity and their low solubility in cryolite melts,
nickel ferrites are considered to be among the most suitable ceramic materials that could be used as
inert anodes in the electrowinning of aluminium. In this work, electrodes composed of single
phased and stoichiometric nickel ferrite NixFe3-xO4 (0≤x<1) have been studied by electrochemical
techniques (linear voltammetry and potentiostatic electrolysis) in a molten cryolite mixture at
960°C. The aim was to understand the oxidation reactions susceptible to take place inside the
material under anodic polarization and oxygen evolution. Ex situ characterization of the electrodes
by SEM-EDX and microprobe analysis allows proposing a degradation mechanism of the pure
nickel ferrites: the formation of haematite Fe2O3 at the grain boundaries was evidenced and it
resulted in a slow degradation. The influence of the Ni content in the ceramic phase was
investigated, and it was shown that rich-Ni compositions exhibit a better resistance to corrosion.
Short Term Oxidation of Stainless Steels during Final Annealing
Authors: Gonzales Sébastien , Combarmond Lucile , Tran Minh Thi , Wouters Yves , Galerie Alain
Published: March 2009

Two ferritic AISI 430 and AISI 441 and two austenitic AISI 304 and AISI 316L stainless
steels were submitted to short term oxidation in a complex atmosphere 3% O2, 16% H2O, 8% CO2,
73% N2 to simulate phenomena occurring during the rapid furnace annealing taking place after the
final cold rolling. This thermal sequence is devoted to metallurgical aims but generates undesirable
oxides which have to be further pickled. Temperature of the furnace was set to the values used in
industrial practice: 900°C for 430, 1060°C for 441 and 1120°C for both austenitics. Six different
oxidation durations were used between 30 and 300 s. For the shortest times, sample temperature
was not constant and heating rate depended on sample thickness. Oxide thickness measured by
GDOS was shown to increase monotonically for all grades whereas mass change measurements
exhibited initial mass losses for the austenitic grades. XRD and Raman spectroscopy were used for
phase characterisation and confirmed the increase of the ratio chromia/haematite with increasing
annealing time. Enrichment of manganese (MnCr2O4), silicon (SiO2) and boron (B-containing
oxide) at the external (Mn) and internal (Si, B) interfaces was observed on the GDOS profiles
(boron for austenitic grades only). Manganese spinel was responsible for blocking chromium (VI)
volatilisation after a certain time, and interface oxides for hindering chromium transfer from the
steel to the oxide scale. Ferritic grades behaved the same, except that no boron enrichment was
detected. Besides, stabilised 441 exhibited Ti and Nb enrichments as oxides at both internal and
external interfaces. External TiO2-NbO2 solid solution was assumed to be hardly dissolved in acidic
pickling baths. All these results were consistent with the different pickling behaviours of the
materials.
Relationship between Chromia Solubility and Superalloy Corrosion in Silicate Melts – A First Attempt
Authors: Khedim Hichem , Abdelouhab S. , Podor Renaud , Rapin Christophe , Vilasi Michel
Published: March 2009

Most of equipments used in glass industry are superalloys containing up to 30 wt%
chromium. The ability of these alloys to resist against silicate melt corrosion is directly linked to the
formation of a chromia (Cr2O3) layer at the alloy/melt interface which can be protective under
particular conditions. These conditions have been previously identified and are the temperature,
melt composition and redox conditions. The aim of the present study is to establish the relationship
between the protective (or non protective) behaviour of the chromia layer with the solubility of
chromia in silicate melts under given conditions.
The combination between results from the electrochemical study of pure chromium corrosion and
total Cr solubility in Na2O-xSiO2 melts clearly indicates that both parameters are linked: the lower
the total Cr solubility, the better the Cr is corrosion resistant.
Modelling the Development of Type I Hot Corrosion on Coated and Uncoated Single Crystal Superalloys
Authors: Simms N.J. , Encinas-Oropesa A. , Nicholls John R.
Published: March 2009

Gas turbines are critical components in the combined cycle power systems being
developed to generate electricity from solid fuels, such as coal and biomass. The use of such fuels
to produce fuel gases introduces the potential for significant corrosive and erosive damage to gas
turbine blades and vanes. Single crystal superalloys have been developed for use with clean fuels
but are now being deployed in industrial gas turbines. The performance of these materials, with
coatings, has to be determined before they can be used with confidence in dirtier fuel environments.
This paper reports results from a series of laboratory tests carried out using the ‘deposit
replenishment’ technique to investigate the sensitivity of candidate materials to exposure conditions
anticipated to cause type I hot corrosion in such gas turbines. The materials investigated have
included the single crystal nickel-based superalloys CMSX-4 and SC2-B, both bare and with Pt-Al
coatings. The exposure conditions within the laboratory tests have covered ranges of SOx (50 and
500 volume parts per million, vpm) and HCl (0 and 500 vpm) in air, as well as 4/1 (Na/K)2SO4
deposits, with deposition fluxes of 1.5, 5 and 15 5g/cm2/h, for periods of up to 500 hours at 900°C.
Data on the performance of materials has been obtained using dimensional metrology: pre-exposure
contact measurements and post-exposure measurements of features on polished cross-sections.
These measurement methods allow distributions of damage data to be determined for use in the
development of materials performance modelling. In addition, the types of damage observed have
been characterised using standard optical and SEM/EDX techniques.
The damage rates of the single crystal materials without coatings are too high for them to be used
with confidence in gas turbines fired with gases derived from ‘dirty fuels’. Under the more severe
combinations of gas composition, deposition flux and metal temperature, the corrosion rates of
these materials with Pt-Al coatings are also excessive. The data produced from these tests has
allowed the sensitivity of hot corrosion damage to changes in the exposure environment to be
determined for the single crystal alloys and coating systems examined.