bluuebunny/crossref_metadata_2025 huggingface dataset:
Residual Stress Analysis Around Foreign Object Damage Using Synchrotron Diffraction
Authors: Frankel P. , Ding Jian , Preuss Michael , Byrne Jim , Withers Philip J.
Published: March 2009

The current study compares the residual strain around foreign object damage (FOD), measured
using synchrotron diffraction, to the strain predicted by a plastic model with power-law dependence.
It is shown that the measured strains are significantly lower than those predicted by the model. This
may be explained in part, by the inability of the model to account for damage mechanisms such as
micro-cracking and shear band formation.
Residual Stress Analysis in Shot Peened and Fretting Fatigued Samples by the Eigenstrain Method
Authors: Korsunsky Alexander M. , Kim Kyung Mok , Regino Gabriel M.
Published: March 2009

Residual stresses in titanium alloy samples that were subjected to shot peening followed
by fretting fatigue loading were investigated using a combined experimental and numerical analysis
procedure based on the concept of eigenstrain. Fretting fatigue loading was carried out in the pad –
on-flat geometry using the Oxford in-line fretting rig. Flat-and-rounded pad shape was used to
introduce the contact tractions and internal stress fields typical of the target application in
aeroengine design. The specimens were in the shape of bars of 10mm square cross-section shotpeened
on all sides. Both the pads and specimens were made from the Ti-6Al-4V alloy. Small
remote displacement characteristic of fretting fatigue conditions was applied in the experiments.
The residual elastic strains in the middle of the pad-to-sample contact and near the rounded pad
edge were measured using synchrotron X-ray diffraction on Station 16.3 at SRS Daresbury.
A combination of finite element analysis and the distributed eigenstrain method was used in
the simulations. Commercial finite element analysis software, ABAQUS ver 6.41, was used to build
the finite element model and to introduce the residual stresses into the model using eigenstrain
distributions via a user-defined subroutine. In an unfretted shot peened sample an excellent
agreement of residual stress profiles was obtained between the experimental data and model
prediction by the variational eigenstrain procedure. In a fretted sample the residual stress change due
to fretting was observed, and predicted numerically. A good correlation was found between the FE
simulation prediction and the experimental data measured at contact edges.
Characterisation of Residual Stresses by X-Ray Diffraction of Laser Welded AZ91 Magnesium Alloy
Authors: Kouadri A. , Barrallier Laurent
Published: March 2009

This study looks at the effect of laser welding on residual stresses in sheets of moulded
magnesium alloy (AZ91). The modifications are significant even though they are localised
along the weld line. The welding process produces a gradient of residual stresses from the
weld line to the base metal and throughout the thickness of the weld zone. The distribution of
these residual stresses has been qualitatively explained by the kinetics of cooling and by the
nature of the multiphase material. Finally, it has been demonstrated that a pronounced
crystallographic texture modifies local distribution of residual stresses. These results show
that there is a complex coupling between the metallurgical, thermal and mechanical aspects
generated by high power welding procedures.
Ultrasonic Stress Measurement in Welded Component by Using Lcr Waves: Analysis of the Microstructure Effect
Authors: Qozam H. , Hoblos J. , Bourse G. , Robin C. , Walaszek Henri , Bouteille Patrick , Cherfaoui M.
Published: March 2009

Welding, which is a largely used process in the mechanical manufacturing, well
known to induce high-level residual stresses. The level of residual stresses is of great
importance for the lifetime of welded components used in mechanical engineering industry.
The use of the ultrasonic method for the evaluation of the residual stresses is based on the
acoustoelastic effect, which refers to the change in velocity of the acoustic waves propagating
in a strained solid. In the case of welding, the microstructure modifications observed in the
heat affected zone (HAZ) and the melted zone (MZ) also induce variations of the velocity of
the acoustic waves. The superposition of the two effects, stresses and microstructure, results
in over-estimating the levels of stresses. This work which was completed in collaboration
with CETIM is a contribution to this problem. The experimental study was carried out on
P460HLE and P265 steels welded sheets. The results obtained by the ultrasonic Lcr wave
technique were compared with those obtained by the hole drilling technique. This work
confirms the possibility of evaluating the residual stresses induced by welding using the
ultrasonic method.
Development of Instrument for Residual Stress Measurement in a 50 mm Inner Diameter Power Generation Pipes
Authors: Belassel M. , Pineault J. , Brauss M.E.
Published: March 2009

With recent issues related to stress corrosion cracking (SCC) and thermal fatigue of power
plant components, including nuclear steam generator tubing, condenser tubing, boiler tubes
steam turbine blades, the residual stress in materials plays an important role in determining
those susceptible for failure caused by fatigue or SCC. These residual stresses, combined
with the applied stresses inherited from manufacturing and assembly can be tensile or
compressive. The SCC can act in a corrosive environment only when the stresses in the
material are tensile, thus leading to cracking of the component and the structure. Thermal
fatigue can be originated from thermal gradients caused during the operation of power plants.
Proto Manufacturing Limited, leader in the residual stress measurement and equipment
development tailored for these applications has developed instruments capable of measuring
residuals tresses in confined areas such as inner diameter of tubes as small as 50 mm in
diameter, non-destructively in the direction of interest, axial direction.
In this paper interesting examples of new x-ray diffraction instrument and measurement
validation are presented along with application inside a 50 mm I.D.
Residual Stress Evolution during Decomposition of Ti(1-x)Al(x)N Coatings Using High-Energy X-Rays
Authors: Terner Mark R. , Hedström Peter , Almer Jonathan , Ilavsky J. , Odén Magnus
Published: March 2009

Residual stresses and microstructural changes during phase separation in Ti33Al67N
coatings were examined using microfocused high energy x-rays from a synchrotron source. The
transmission geometry allowed simultaneous acquisition of x-ray diffraction data over 360° and
revealed that the decomposition at elevated temperatures occurred anisotropically, initiating
preferentially along the film plane. The as-deposited compressive residual stress in the film plane
first relaxed with annealing, before dramatically increasing concurrently with the initial stage of
phase separation where metastable, nm-scale c-AlN platelets precipitated along the film direction.
These findings were further supported from SAXS analyses.
The Effect of Plastic Anisotropy on the Residual Stress within a 316L Stainless Steel Bead-on-Plate Specimen
Authors: Turski Mark , Pratihar S. , Edwards Lyndon , Daymond Mark R. , Fitzpatrick Michael E.
Published: March 2009

Plastic anisotropy can affect the strains measured by neutron diffraction. If this is not
properly accounted for significant errors can result in the calculated stresses. This paper illustrates
addresses this issue using measurements of the residual strain field around a 60 mm long single
weld bead deposited on the surface of a 17 mm thick stainless steel plate. Measurements were made
on ENGIN-X, the engineering spectrometer at the ISIS facility of the Rutherford Appleton
Laboratory (UK). Diffraction spectra from these measurements have been fitted using both single
and multi-peak fitting approaches. Both residual strain and stress results have been presented for
(111) and (200) single peak fits and compared to a multi-peak fit (Rietveld) analysis. Results from
these analyses have revealed significant anisotropy in the response of the individual lattice planes.
This effect is most severe in measurements carried out in the normal direction and is shown to be
predicted using an elasto-plastic self-consistent model.
Effect of Surface Nano Crystallization on Tribological Properties of Stainless Steel
Authors: Roland T. , Retraint Delphine , Lu K. , Lu Jian
Published: March 2009

A novel surface treatment has been developed in the present work to enhance the
tribological properties of 316L Stainless Steel. This Technique involves the formation of a
nanocrystalline layer ascribable to a grain refinement mechanism induced by repeated impact
loadings supported by the surface. The resultant system has a layered structure, comprising
nanometric grains (less than 100 nm) at the top and a strain hardened transition layer in the
subsurface. Such a microstructural feature has the potential to significantlty enhance the surface
hardness and to create a high compressive residual stress state. The tribological properties of the
stainless steel are thus improved in terms of lower friction coefficient and increased wear resistance.
Detailed studies on the response of the nanocrystalline surface layer to annealing at temperatures
between 400°C and 600°C showed that an annealing at high temperature can offer much better
tribological enhancement than low temperature annealings due to enhanced martensitic
transformation.
Effect of Detector Width and Peak Location Technique on Residual Stress Determination in Case of Work-Hardened Materials
Authors: Belassel M. , Bocher Eliane , Pineault J.
Published: March 2009

To enhance the fatigue resistance of mechanical components, different surface treatment
processes are often applied to put the near surface layer into compression. Surface treatment
processes are typically associated with deformation and work-hardening of the material.
When applying x-ray diffraction techniques to the characterization of such surfaces, the
work-hardening will cause the x-ray diffraction peak width to increase. When peak widths
reach high values, the peak tail may extend beyond the active area or window of the multichannel
x-ray detector, in which case the peak is truncated. Subsequent analytical treatment
of broad diffraction peaks is troublesome and advanced numerical methods are required to
accurately determine the peak position. The following work indicates that when a wider
detector is used it is possible to collect the full, non-truncated peak, determine the peak
position with a high level of confidence and subsequently, to calculate the residual stress
with much improved repeatability and reproducibility.
Internal Stress Development during Fatigue Cycling of High-Strength Al/SiC Metal Matrix Composites
Authors: Fitzpatrick Michael E.
Published: March 2009

In this paper, results are presented of the development of internal stresses in 2124
aluminium alloy reinforced with 25% of particulate silicon carbide. Measurements have been
made during in situ low-cycle fatigue loading of this composite, using neutron diffraction. The
neutron measurements were made using the ENGIN-X diffractometer at the ISIS neutron facility,
UK. The results show how the internal stresses evolve with fatigue cycling. Eshelby-based
modelling has been used to allow separation of the internal stress components in the MMC.
Effective Stresses and Plastic Strain Rates in a Superalloy: a High Temperature In Situ Study by Synchrotron X-Ray TCD
Authors: Jacques Alain , Ferry Olivier , Diologent Frédéric , Caron Pierre , Bastie Pierre
Published: March 2009

Variations in the lattice parameters of γ and γ' phases perpendicular to the [001] tensile
axis were recorded in situ at ~10 minutes intervals using the Triple Axis Diffractometer of the High
Energy (ID15) beamline at ESRF. Testing was carried out on an AM1 superalloy specimen with a
raft microstructure at high temperature (1072°C) under load steps between 0 MPa and 300 MPa.
These data were used to evaluate the Young modulus and the effective (Von Mises) stresses within
the γ' rafts and γ corridors, as well the average plastic strain rates of each phase. The recorded stress
data scatter was within the MPa range, and should be good enough to probe the elementary
mechanisms of plasticity.
Data Collection Requirements for the Analysis of Residual Stress in Polycrystalline Coatings
Authors: Vermeulen Arnold C. , Götz Detlev
Published: March 2009

Residual stress in polycrystalline coatings can be determined by X-ray diffraction. The data
collection requirements are summarized and evaluated in this paper. First, general requirements for stress
measurements are described. Then, requirements related to the diffraction geometry and the specimen
manipulation are considered. Finally, requirements with respect to specimen characteristics, including
various coating-substrate combinations are presented. Polycrystalline coatings can be nanocrystalline,
randomly orientated or highly textured. The substrates can be of any nature: amorphous, polycrystalline or
single crystal. The complete set of requirements leads to a measurement advice for a particular coatingsubstrate
specimen, which includes the choice of diffraction geometry and the data collection strategy.
Based on two complementary test cases it is demonstrated that the set of rules is complete and that they can
be applied to any type of polycrystalline specimen.
The Effect of Phase Transformations on Predicted Values of Residual Stresses in Welded Ferritic Components
Authors: Warren Alex P. , Bate Steve K. , Charles Richard , Watson C.T.
Published: March 2009

The accurate prediction of the residual stresses present in welded structures can be of
great importance to the fracture assessment of such components. Therefore, a large amount of
benefit can be gained from improving techniques for measuring and numerically analysing these
stresses. In recent years many advances have been made in the field of analysing residual stresses
using finite element methods. That said, very little work has been conducted on the accurate
modelling of welded ferritic components. This is largely due to the added complication of phase
transformations that occur during the heating and cooling of such steels.
The objective of the work presented in this paper was to improve understanding of the effect that
phase transformations have on residual stresses present within welded ferritic structures. This was
conducted by simulating such welding processes using the finite element package SYSWELD.
An investigation was conducted to determine how phase transformations, and therefore residual
stresses, are affected by the welding process used. Phase transformation and material property data
available within SYSWELD were used for this analysis. An autogenously welded beam provided a
simple basis for this qualitative investigation. In the future the manufacture and measurement of
suitable test-pieces will enable these simulations to be validated.
Residual Stress in EB-PVD Thermal Barrier Coatings
Authors: Suzuki Kenji , Tanaka Keisuke , Shobu Takahisa
Published: March 2009

A NiCoCrAlY bond coating was low-pressure plasma sprayed on a stainless steel sub-
strate. Zirconia with 8 wt% yttria was deposited on the bond coating using an electron beam-physical
vapor deposition (EB-PVD) method. The top coating had the preferred orientation with the h111i
axis direction perpendicular to the coating plane. The distribution of the in-plane residual stress in the
top coating was measured using laboratory Cr-K X-rays with a progressive layer removal method.
The value of the in-plane stresses was determined by the sin2 method after the separation of the
133 and 331 peaks. The distribution of the out-of-plane strain in the top coating was measured using
the strain scanning method with hard synchrotron X-rays. The out-of-plane strain was obtained from
the 333 peak which had strong intensity due to the preferred orientation. The measured value of the
in-plane stress in the top coating was a large compression, and showed a steep decrease near the in-
terface between the top and the bond coatings. The distribution of the out-of-plane stress showed a
compression, and its magnitude was smaller than that of the in-plane stress.
Comparative Studies of Textured Pulsed Laser Deposition and Sol-Gel Growth of Thin Hydroxyapatite Layers on Titanium Substrates
Authors: Carradò Adele , Fabre Agnès , Barrallier Laurent , Viart Nathalie , Mihailescu Ion N. , Socol Gabriel , Grigorescu Sorin , Werckmann Jacques , Ciuca S. , Tarcolea M.
Published: March 2009

The aim of this paper is the residual stress evaluation in dental implants and the improvement
of adherence at the metal-ceramic interface. This study is focused on the development of a multi-layer
system model of Hydroxyapatite/TiO2/Ti components. Our aim is to validate new methods of laser
ablation deposition and sol-gel, by controlling the residual stresses and actual adherence to titanium
substrates. We present a report of the growth of hydroxyapatite layers by PLD (pulsed laser deposition)
and sol-gel deposition, and the measurement of their residual stresses.
Residual Stress and Microstructure in the Rail/Wheel Contact Zone of a Worn Railway Wheel
Authors: Wild Eric , Reimers Walter
Published: March 2009

The rail/ wheel contact comprises interactions of thermal and mechanical loadings which
lead to microstructural changes in the wheel. These were investigated on a wheel from a regional
train using metallographic examinations, X-ray diffraction for phase and residual stress analyses.
The results show that the microstructural alterations, the carbon content and the residual stress
distribution depend on the loading profile of the wheel. The formation of two different martensites
(tetragonal and cubic martensite) on a wheel surface could be detected at different positions. The
martensites are characterized by high hardness values, increased carbon contents in the lattice and
an increased level of compressive residual stresses. Detailed structural analyses of the martensites
which were formed under locally different loading and time conditions gave evidence for different
structural evolutions.
New Ceramic Abrasive Tools for Rough and Finishing Grinding in One Pass
Authors: Herman Daniela , Plichta J. , Nadolny K.
Published: March 2009

A new type of ceramic abrasive tools prepared of aluminium oxide (alumina), designed
to realise the one-pass process of inside diameter grinding.
Distinctive feature of these tools is the gradient distribution of the abrasive grain zones with
different sizes and structure which enables to carry out the rough (efficient) and finishing grinding
in one pass.
An influence of the grinding speed vS and the quantities of the working engagement ae on the worksurface
roughness and the grinding power were determined.
A New Method for Determining the Chip Geometry in Milling
Authors: San Juan M. , Santos Martin Francisco , de la Fuente T. , Aranda S.
Published: March 2009

Frequently, to validate FEM simulations of the cutting process it is compared the
predicted results with the experimental cutting forces. In addition, other parameters are measured
and it is possible to predict the chip geometry in some particular conditions. This paper presents a
new development of the photogrammetry and its applications in the study of the chip geometry. In
the orthogonal milling case, it is possible to obtain a 3D model of the deformed chip employing
photogrammetry digitization techniques.
Fundamental Limitations of SiC PVT Growth Reactors with Cylindrical Heaters
Authors: Drachev Roman , Deyneka E. , Rhodes C. , Schupp J. , Sudarshan Tangali S.
Published: March 2009

The ability to set and accurately control the desired growth conditions is crucial in order
to attain high quality bulk growth of Silicon Carbide (SiC), especially when the ingot size is large
(> 2” in diameter by > 2” long). However, these two aspects of SiC PVT (Physical Vapor
Transport) growth technology are severely limited in “conventional” SiC PVT growth reactors with
single cylindrical heaters. To overcome such shortcomings, an “alternative” furnace design with
two plane resistive heaters is proposed. In order to verify benefits of this design, numerical
modeling and comparative procedures have been employed. Detailed comparative analysis revealed
two fundamental disadvantages of the conventional furnace design, attributed to (a) – significantly
higher in magnitude and spatially nonuniform distribution of the thermal stress that consequently
deteriorates structural quality of the growing SiC boule, and (b) – inability to grow long (> 2”)
monocrystalline ingots of SiC. Furthermore, the potential of the alternative furnace design to
overcome fundamental limitations of the conventional design is also analyzed, with particular
attention being paid to the processes of source material recrystallization.
Lower-Temperature Epitaxial Growth of 4H-SiC Using CH3Cl Carbon Gas Precursor
Authors: Koshka Yaroslav , Lin Huang De , Melnychuk Galyna , Wood Colin
Published: March 2009

The advantages of the CH3Cl carbon precursor were investigated in order to achieve
good-quality homoepitaxial layers of the 4H-SiC polytype at temperatures lower than what was
considered practical (or even possible) with C3H8-based growth. It was observed that the process
window for good epilayer morphology becomes narrower when the growth temperature is
decreased. Successful growth experiments have been conducted in this work down to a temperature
of 1290-13000C, with the growth rate in excess of 2 +m/hr and a mirror-like defect-free epilayer
surface morphology. Growth on a 2” substrate produced promising growth rate homogeneity. The
dependence of the growth rate on SiH4 flow followed a clear exponential dependence. This trend is
tentatively attributed to Si vapor condensation. Photoluminescence results suggest that the
crystalline quality of the epilayers grown at 13000C is comparable to that of 17000C growth.
Selective Etching of Micropipes During Initial Homoepitaxial Growth Stage on Nearly On-Axis 4H-SiC Substrates
Authors: Bahng Wook , Cheong Hui Jong , Kang In Ho , Kim Sang Cheol , Kim Ki Hyun , Kim Nam Kyun
Published: March 2009

The initial homoepitaxial growth behavior on nearly on-axis 4H-SiC substrates was
investigated. We have observed circular etch pits on the surface of on-axis substrate in the presence of
source gases. However, there were no circular etch pits on the surface of off-axis substrates. In
addition, the surface etched by H2 gas did not show circular etch pits even on nearly on-axis substrates.
The shape of the circular etch pits was similar to spiral one. The initial growth behavior of epilayers
was also investigated with various C/Si ratios of source gases (0.6<C/Si<2.0). The circular etch pits
were observed independent of the source gas ratio. It implies that the source gases promote the
selective etching, while the H2 gas etches SiC defect-independent. The spiral shape of etch pits seems
to be produced from the screw dislocation with large burgers vector of micropipes. Therefore, the
circular shape etch pits were not observed in an off-axis substrate.
Halide-CVD Growth of Bulk SiC Crystals
Authors: Polyakov A.Y. , Fanton Mark A. , Skowronski Marek , Chung Hun Jae , Nigam Saurav , Huh Sung Wook
Published: March 2009

A novel approach to the high growth rate Chemical Vapor Deposition of SiC is
described. The Halide Chemical Vapor Deposition (HCVD) method uses SiCl4, C3H8 (or CH4), and
hydrogen as reactants. The use of halogenated Si source and of separate injection of Si and C
precursors allows for preheating of source gases without causing premature chemical reactions. The
stoichiometry of HCVD crystals can be controlled by changing the C/Si flow ratio and can be kept
constant throughout growth, in contrast to the Physical Vapor Transport technique. HCVD was
demonstrated to deposit high crystalline quality, very high purity 4H- and 6H-SiC crystals with
growth rates comparable to other bulk SiC growth techniques. The densities of deep electron and
hole traps are determined by growth temperature and C/Si ratio and can be as low as that found in
standard silane-based CVD epitaxy. At high C/Si flow ratio, the resistivity of HCVD crystals
exceeds 105 _cm. These characteristics make HCVD an attractive method to grow SiC for
applications in high-frequency and/or high voltage devices.
Homoepitaxial Growth of Iron-Doped 4H-SiC Using BTMSM and t-Butylferrocene Precursors for Semi-Insulating Property
Authors: Song Ho Keun , Moon Jeong Hyun , Yim Jeong Hyuk , Kim Hyeong Joon
Published: March 2009

In this paper, we attempted to grow semi-insulating SiC epitaxial layer by in-situ iron
doping. Homoepitaxial growth of iron-doped 4H-SiC layer was performed by MOCVD using
organo-silicon precursor, bis-trimethylsilylmethane (BTMSM, [C7H20Si2]) and metal organic
precursor, t-butylferrocene ([C14H17Fe]). Doping-induced crystallinity degradation showed different
tendency depending on conducting type of substrate. The crystal quality of epilayer grown on n-type
substrate was not degraded significantly despite of the Fe doping but in case of semi-insulating
substrate, crystallinity was remarkably degraded as increasing iron contents. For measurement of
resistivity of highly resistive iron-doped 4H-SiC epilayer, we used the on-resistance technique which
is firstly attempted for measuring resistivity of epilayer. From on-resistance of epilayer measured by
I-V, it is shown that the residual donor concentration of epilayer was decreased as increasing partial
pressure of t-butylferrocene. The resistivity of iron-doped 4H-SiC epilayer was about 107 Ωcm. From
this result, it is concluded that Fe could effectively act as a compensation center in the iron-doped
4H-SiC.
Epitaxial Growth of 4H-SiC {0001} with Large Off-Angles by Chemical Vapor Deposition
Authors: Saitoh Hiroaki , Manabe Akira , Kimoto Tsunenobu
Published: March 2009

We have investigated the morphology and doping characteristics of 4H-SiC epilayers
grown on 13o-22o off-axis (0001) substrates by horizontal hot-wall CVD. Step bunching is not
observed on 18o off-axis substrates as well as on other substrates with large off-angles. The rms
roughness is a minimum (as small as 0.10 nm) on 18o off-axis (0001). Under C-rich condition (C/Si
>1.0), the donor concentration increases by increasing the off-angle, when the off-angle is larger than
15o. This trend in doping characteristic is enhanced in CVD growth at 1450-1500oC. At a high
temperature of 1600oC, however, the off-angle dependence of donor concentration is significantly
reduced. Epitaxial growth on 4H-SiC(000-1) with large off-angles is also reported.
Stability of Thick Layers Grown on (1-100) and (11-20) Orientations of 4H-SiC
Authors: Syväjärvi Mikael , Yakimova Rositza , Yazdi Gholam Reza , Arjunan Arul , Toupitsyn Eugene , Sudarshan Tangali S.
Published: March 2009

Thick layers have been grown on (1120) and (1 1 00)6H-SiC substrates. The thicknesses
are up to 90 #m obtained with growth rate of 180 #m/h. Even in such thick layers the surfaces are
smooth and only disturbed by polishing scratches. The surfaces contain steps which facilitate
reproduction of the substrate polytype.
Comparison of Propagation and Nucleation of Basal Plane Dislocations in 4H-SiC(000-1) and (0001) Epitaxy
Authors: Tsuchida Hidekazu , Kamata Isaho , Miyanagi Toshiyuki , Nakamura Tomonori , Nakayama Koji , Ishii R. , Sugawara Yoshitaka
Published: March 2009

Propagation and nucleation of basal plane dislocations (BPDs) in 4H-SiC(000-1) and
(0001) epitaxy were compared. Synchrotron reflection X-ray topography was performed before and
after epitaxial growth to classify the BPDs into those propagated from the substrate into the epilayer
and those nucleated in the epilayer. It was revealed that the propagation ratio of BPDs for the (000-1)
epitaxy was significantly smaller than that for the (0001) epitaxy. Growing (000-1) epilayers at a high
C/Si ratio of 1.2 achieves a further reduction in BPDs to only 3 cm-2 for those propagated from the
substrate, and 16 cm-2 for those nucleated in the epilayer. A dramatic increase was also found in the
nucleation of BPDs omitting the re-polishing and in-situ H2 etching procedure.
Growth Kinetics and Polytype Stability in Halide Chemical Vapor Deposition of SiC
Authors: Nigam Saurav , Chung Hun Jae , Huh Sung Wook , Grim J.R. , Polyakov A.Y. , Fanton Mark A. , Weiland B.E. , Snyder David , Skowronski Marek
Published: March 2009

Growth rates and relative stability of 6H- and 4H-SiC have been studied as a function of
growth conditions during Halide Chemical Vapor Deposition (HCVD) process using silicon
tetrachloride, propane and hydrogen as reactants. The growth temperature ranged from 2000 to 2150
oC. Silicon carbide crystals were deposited at growth rates in the 100-300 μm/hr range in both
silicon- and carbon-supply limited regimes by adjusting flows of all three reactants. High resolution
x-ray diffraction measurements show that the growth on Si-face of 6H- and C-face of 4H-SiC
substrates resulted in single crystal 6H- and 4H-SiC polytype, respectively. The growth rate results
have been interpreted using thermodynamic equilibrium calculations.
Structure of Carrot Defects in 4H-SiC Epilayers
Authors: Zhang X. , Ha Seoyong , Benamara M. , Skowronski Marek , Sumakeris Joseph J. , Ryu Sei Hyung , Paisley Michael J. , O'Loughlin Michael  J.
Published: March 2009

Structure of the “carrot” defects in 4H-SiC homoepitaxial layers deposited by CVD has
been investigated by plan-view and cross-sectional transmission x-ray topography, cross-sectional
transmission electron microscopy, atomic force microscopy, and KOH etching. The carrot defects
nucleate at the substrate/epilayer interface at the emergence points of threading screw dislocations
propagating from the substrate. The typical defect consists of two stacking faults: one in the prismatic
plane with second one in the basal plane. The faults are connected by a stair-rod dislocation with
Burgers vector 1/n[10-10] with n>3 at the cross-over. The basal plane fault is of Frank-type. Carrot
defects are electrically active as evidenced by contrast in EBIC images indicating enhanced carrier
recombination rate. Presence of carrot defects in the p-i-n diodes results in higher pre-breakdown
reverse leakage current and approximately 50% lower breakdown voltage compared to the nominal
value.
Resistivity Distribution in Undoped 6H-SiC Boules and Wafers
Authors: Li Qiang , Polyakov A.Y. , Skowronski Marek , Sanchez Edward , Loboda Mark J. , Fanton Mark A. , Bogart Timothy , Gamble Rick D. , Smirnov N.B. , Makarov Yuri
Published: March 2009

For undoped 6H-SiC boules grown by physical vapor transport the variations of resistivity,
of the type and density of deep electron and hole traps, and of the concentration of nitrogen and boron
were studied as a function of position in the cross section normal to the growth axis and along the
growth direction. It was observed that the concentrations of all deep electron and hole traps decreased
when moving from seed to tail of the boule and from the center to the edge of the wafers. Modeling of
the growth process suggests that the C/Si ratio increases in a similar fashion and could be responsible
for observed changes. We also discuss the implications of such stoichiometry changes on
compensation mechanisms rendering the crystals semi-insulating and on electrical uniformity of
SI-SiC wafers.
A Study of Nitrogen Incorporation in PVT Growth of n+ 4H SiC
Authors: Hansen Darren M. , Chung Gil Yong , Loboda Mark J.
Published: March 2009

A detailed understanding of the incorporation of N2 gas during PVT growth of SiC is
required to achieve high performance, low resistivity n+ SiC substrates necessary for power device
applications. In this report, nitrogen incorporation is investigated for growth of 4H SiC crystals
from 2” to 3” diameter in conditions ranging from unintentionally doped to low resistivity (0.015 -
cm). For a wafer in a particular boule a resistivity uniformity of ± 5% is typical although the
uniformity decreases when the wafer orientation is cut off axis from the bulk growth direction.
Within a boule growth, the nitrogen incorporation is found to be a function of growth time. As
growth continues, the resistivity of wafers cut further from the seed increases. A typical 3” on axis
sliced wafer has a within wafer resistivity uniformity of 5% compared with an average seed to tail
variation of 10%. Due to the axial resistivity gradient the within wafer resistivity uniformity of off
axis sliced wafers is 8%. These axial and radial gradients are thought to be a function of the
changing C/Si ratio during growth. Nitrogen incorporation as a function of PVT geometry, N2
partial pressure, and growth temperature are investigated and discussed. In particular, nitrogen
incorporation is found to depend on the crucible size and nitrogen partial pressure, but is not
strongly dependent on the absolute growth temperature, for growth temperature ranging over 150°C.
Modeling of PVT growth shows the axial resistivity gradient can be linked with a change in the C/Si
ratio versus time. Trends and N2 gas incorporation behavior will be discussed using resistivity
mapping, SIMS, and Hall effect data.
Modeling and Experimental Verification of SiC M-PVT Bulk Crystal Growth
Authors: Wellmann Peter J. , Müller Ralf , Pons Michel
Published: March 2009

We have studied the impact of the chemical nature of additional gases fed into the
modified physical vapor transport (M-PVT) growth cell. In particular experiments were carried out
using helium, argon, nitrogen and propane in the growth setup. Numerical modeling was used to
address the underlying physical and chemical effects that impact the global temperature field. It is
found that chemical decomposition of complex gases plays a secondary role as heat source or sink.
However, temperature variations related to varying gas compositions fed to the systems are
primarily induced by changes of the graphite foam isolation properties.
Basal Plane Dislocation Dynamics in Highly p-Type Doped versus Highly n-Type Doped SiC
Authors: Wellmann Peter J. , Queren Desirée , Müller Ralf , Sakwe Sakwe Aloysius , Künecke Ulrike
Published: March 2009

The long term performance of today’s SiC based bipolar power devices suffer
strongly from stacking fault formation caused by slip of basal plane dislocations, the latter
often originating from the n-type doped SiC substrate wafer. In this paper, using sequentially
p-type / n-type / p-type doped SiC crystals, we address the question, whether basal plane
dislocation generation and annihilation behaves differently in n-type and p-type SiC. We have
found that basal plane dislocations are absent or at least appear significantly less pronounced
in p-type doped SiC, which may become of great importance for the stacking fault problem in
SiC.
Active Thermal Interaction of Source and Crystal Surfaces in PVT SiC Crystal Growth
Authors: Grasza Krzysztof , Tymicki Emil , Kisielewski Jaroslaw
Published: March 2009

Silicon carbide crystals were grown from the vapor. Improvement of the quality of the
central part of the crystal was achieved by optimization of the geometry of the source material.
Active thermal interaction of the source material and the crystallization front made possible an
effective programming of the shape and morphology of the crystal. Termination of micropipes on
microfacets formed on the crystallization front during growth was observed.
The Influence of SiC Powder Source on 6H-SiC Single Crystals Grown by the Sublimation Method
Authors: Kim Jae Woo , Seo Soo Hyung , Kim Kwan Mo , Song Joon Suk , Kim Tae Sung , Oh Myung Hwan
Published: March 2009

We examined the influence of thermal treatment of high-purity SiC powder on 6H-SiC
crystal growth. The doping concentration was decreased by increasing either thermal treatment
temperature or time. It was also found that the defects such as micropipes and planar cavities were
generated under relatively long treatment time (13 hours), because SiC powders were significantly
graphitized. A 6H-SiC crystal grown by using SiC source treated at 2100oC for 6 hours revealed the
best result with relatively low micropipes. For the effects of thermal treated sources on the
improvement of crystallinity, it could be explained that both the amount of alpha phase transformed
from high-purity beta-SiC powder and the elimination of porous powders in SiC powder had an
influence on the removal of silicon droplets, resulting in higher Si vapor pressure at the initial growth
stage.
Curie Temperature Determination of Pr14Fe79.9-xCoxB6Nb0.1 Permanent Magnet Alloys
Authors: Barbosa Luzinete Pereira , Takiishi Hidetoshi , de Faria Jr. Rubens Nunes , Rodrigues Daniel , Janasi S.R.
Published: March 2009

This paper reports the results of investigations carried out to determine the Curie temperature (Tc) of some annealed praseodymium-based alloys represented by the formula Pr14Fe79.9-xCoxB6Nb0.1. The Curie temperature of these permanent magnet alloys increase linearly with the cobalt content at about (10.2±0.3) oC/at%. Pr14Fe80B6 and Pr14Fe79.9B6Nb0.1 magnetic alloys with a Tc of 290oC have been used as a standard reference. Magnets were prepared from the alloys using the hydrogenation, disproportionation, desorption and recombination (HDDR) process.
Sm2Fe17Nx Produced by Calciothermic Reduction Using Different Iron Powders
Authors: Boareto J.C. , Soyama Juliano , Felisberto M.D.V. , Slaviero André L. , Wendhausen Paulo A.P.
Published: March 2009

This paper compared the influence of the iron powder in the production of Sm2Fe17Nx by calciothermic reduction. Two available iron powders were used: Basf CL carbonyl iron and Ancor MH-100 sponge iron. Both alloys were prepared and analyzed with X-ray diffraction, scanning electronic microscope and vibrating sample magnetometer. The results showed that the alloy produced with Ancor Mh-100 presents a higher anisotropy. The alloy produced with Basf CL has a smaller anisotropy but a higher coercivity. This can be explained by the difference in the microstructure of the two powders.
Porosity Study of Sintered Titanium Foams
Authors: de Oliveira Marize Varella , Moreira Anderson Camargo , Appoloni Carlos R. , Lopes R.T. , Pereira Luiz Carlos , Cairo Carlos Alberto Alves
Published: March 2009

Titanium foams have been used for surgical implants and biomedical engineering
because they exhibit inert behavior and good corrosion resistance. Substantial progress has
been achieved for metallic foam fabrication techniques, however the porosity characterization
methods available haven’t been studied sufficiently. A previous research has developed a
powder metallurgy route to produce pure titanium foams attaining the porosity requisites for
porous surfaced surgical implants. In this study, titanium foams porosity was evaluated
employing different techniques: optical quantitative metallographic analysis with automatic
image technique, gamma-ray transmission and x-ray microtomography. These techniques can
be used for titanium foams analysis, though their results can not be simply compared, because
they use quite different methodologies and take different measurement assumptions.
On the Use of Elemental Powders to Process Fe-50Co Alloys by Powder Injection Molding
Authors: Wendhausen Paulo A.P. , Silva Aline , Slaviero André L. , Machado Ricardo
Published: March 2009

Aiming to obtain components with higher density, this work evaluated the technical and economical viabilities to replace the pre-alloyed Fe49Co2V by an elemental powder alloy of iron and cobalt (Fe-50Co). Using an elemental alloy could increase the density of the final material due to the driving force created by the chemical gradient between the powders. The results showed that is possible to achieve higher densities in an elemental powder Fe-50Co alloy sinterized at the same temperature and in shorter times than the Fe49Co2V alloy. The analysis of economical viability showed that the replacement of the alloys have advantages as the pre-alloyed powder price is higher than the elemental.
Structure and Properties of Gradient Layers Using High Power Diode Laser
Authors: Dobrzański Leszek Adam , Piec Marek , Trojanová Zuzanka , Lelątko Józef , Klimpel Andrzej
Published: March 2009

Investigations include alloying the X38CrMoV5-3 hot-work tool steel surface
layer with the tungsten carbide, using the high power diode laser (HPDL). The tungsten
carbide ceramic particles of the medium grain size according to FSSS = 50 Bm were
introduced using the rotor conveyer to improve the properties of the surface layer. The
powder feed rate was set at the steady level of 8.64g/min. Remelting and alloying were
carried out several times in the laser power range of 1.2 – 2.3 kW in the remelting/alloying,
alloying/remelting sequences. The structural mechanism was determined of gradient layer
development, effect was studied of alloying parameters, gas protection method, and powder
feed rate on its mechanical properties, and especially on its hardness, abrasive wear
resistance, and roughness. Structure changes were revealed consisting, in particular, in its
refining, and also hardness and microhardness changes in comparison to the non-remelted
steel. Examination results obtained with the EDX microanalysis, surface and linear analyses
of the chemical composition, as well as the X-ray qualitative phase analysis are presented.
Concentration Profiles and Iso-Concentration Curves for Batch Settling Using the Gamma Rays Attenuation Technique
Authors: Arouca Fábio de Oliveira , Lopes L.C.O. , Damasceno João Jorge Ribeiro
Published: March 2009

Knowledge of particle concentration is of extreme importance for the settling
phenomenon. For well-diluted suspensions the solids concentration can be measured by
sampling techniques. However, the use of such a technique for more concentrated suspension
does not lead to good results. Knowledge of concentration distribution in sediments formed
by decantation of aqueous suspensions inside a vertical vessel is fundamental for the
evaluation of performance of some pieces of equipment such as continuous thickeners. In this
work, the phenomenon of batch settling of aqueous suspensions of calcium carbonate was
studied by using a nondestructive technique based upon the measurement of gamma-ray
attenuation when the radiation beam goes through the physical medium as a function of the
local concentration in several vertical positions of the vessel, and the sampling of suspension
by aliquots is not necessary. The main objective of this work is to evaluate the use of gammaray
attenuation technique for achieving concentration distributions in the phenomenon of
batch settling as well as curves of iso-concentrations.
Synthesis and Characterization of Nanosized ZrTiO4 Powders Prepared by the Sol-Gel Method
Authors: Cosentino I.C. , Vichi F.M. , Muccillo E.N.S. , Muccillo R.
Published: March 2009

Ceramic ZrTiO4 powders were prepared by a modified sol-gel method using
zirconium oxychloride and titanium tetraisopropoxide. In situ high temperature X-ray
diffraction results show that crystallization of the amorphous gel starts at 400 °C. Singlephase
ZrTiO4 nanoparticles were obtained after heat treatment at 450 oC for 1 h. An average
particle size of 46 nm has been determined by nitrogen adsorption analysis. After pressing
these sinteractive powders, pellets with controlled pore size distribution were obtained by
sintering at temperatures as low as 400 oC. The analysis of pores by mercury porosimetry
shows an average porosity of 45 %. Pressing and sintering the nanosized powders prepared by
that modified sol-gel technique produced pellets that are good candidates to be used in
humidity sensing devices.
Compaction Behavior Study of Powder Composed by Nanoparticle Agglomerates and Aggregates
Authors: Nono Maria do Carmo de Andrade
Published: March 2009

Ceramic powder compaction by pressing requires weak-agglomerated powders to obtain high dense compacts and consequently dense sintered ceramic body. In this work powders with different agglomerated and/or aggregated size distributions was compacted by uniaxial and isostatic pressing. The powder and compacts were characterized by mercury and nitrogen porosimetry, BET and SEM. Analysis of X-rays diffraction peaks was used to determine the particle size (diameter). The Scherrer method was used to obtain the estimated average nanoparticle size. The results showed that all aggregated and weak agglomerated powders were composed by nanoparticles. This study indicated that the nanoparticle aggregates and weak agglomerates were destroyed during the pressing stage conducting to a increase of the packing degree of the powder particles.
Effect of the Particle Size of an Ash from Sugarcane Bagasse in the Properties of Red Ceramics
Authors: Gadioli Monica Castoldi Borlini , Mendonça J.L.C.C. , Conte R.A. , Pinatti Daltro Garcia , Vieira Carlos Maurício Fontes , Monteiro Sérgio Neves
Published: March 2009

The influence of the particle size of an ash from sugarcane bagasse on the
properties of incorporated red ceramics was investigated. Mixtures of kaolinitic clay from the
municipal area of Campos of Goytacazes-RJ were prepared with additions of 0, 5 and 10% in
weight of ashes from sugarcane bagasse. Ashes with different particle sizes lower than
149 μm (100 mesh), 75 μm (200 mesh) and 44 μm (325 mesh), were used in each
incorporated composition. Specimens were 20 MPa uniaxially press-molded and sintered at
900 and 1050°C. The firing technological properties evaluated were diametrical shrinkage,
water absorption and mechanical strength by diametrical compression. The results showed
that the ash incorporation caused significant changes in the ceramic properties.
Obtention of TCP Porous Ceramic Using Albumin
Authors: Ribeiro Christiane , Bressiani José Carlos , Bressiani Ana Helena A.
Published: March 2009

In the last years, the porosity in ceramic materials for implants production has
motivated the development of various technologies. Calcium phosphate ceramics, in special
the tricalcium phosphate - TCP, are very promising as bone substitutes and scaffolds for
tissue engineering. The macroporosity incorporation in TCP ceramics by porogenic, foaming
and consolidator agent, as globular protein (ovalbumin) was the focus of this work.
Preliminary studies of zeta potential were made to have a suitable suspension. Ovalbumin
amounts (5-7 wt%) were added to the ceramic slurries and suspensions with a solid
percentage higher than 60 wt% were obtained. The interaction albumin/surfactant with
detergency properties was evaluated by pH and viscosity measurements. The foam was
produced by mechanical stirring. The results suggested that the presence of the surfactant
increase the volume and stability of foam. After drying, burnout and sintering (1200oC/30
min.) the phase composition of the foams was determined by X-ray diffraction. The
microstructure and porosity were evaluated by scanning electron microscopy. SEM
micrographs of the foam show that the structure consists of a permeable porous network,
being observed spherical and interconnected pores.