bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Trace Element Er on Al-Mg and Al-Mg-Mn Alloys
Authors: Xing Ze Bing , Nie Zuo-Ren , Zou Jing Xia , Ji Xiao Lan , Wang Xu Dong
Published: March 2009

The behaviors of trace element Er on binary Al-Mg and ternary Al-Mg-Mn alloys have
been investigated through optical microscopy, x-ray diffraction, scanning electron microscopy with
energy dispersive spectroscopy and transmission electron microscope. It was found that Er additions
more than 0.4% (wt%) produced a remarkable refinement in grain size of Al-Mg and Al-Mg-Mn
alloys castings. Er can enhance the tensile strength of the two group experimental alloys significantly
but not greatly decrease the elongation due to the formation of many fine like spherical and dispersive
primary and precipitation Al3Er particles during casting and heating process. Al3Er particles have L12
crystal structure (space group Pm3m) with a lattice parameter of 0.42119nm, and have a coherent
relationship with the matrix phase α-Al (mismatch only 4.1%), which can be acted as the
heterogeneous nucleus during solidification to increase the rate of nucleation, and the other hands it
can strongly pin up dislocations and subgrain boundaries and retard the recrystallization of alloys.
Effect of Low Frequency Electromagnetic Field on Microstructures and Macro-Segregation of Direct Chill Casting Al-19.2%Si Alloys
Authors: Qin Ke , Cui Jian Zhong
Published: March 2009

The influences of low frequency electromagnetic field on microstructures and
macro-segregation in direct chill casting process were investigated in the experiments，Al-19.2%Si
alloys were semi-continuously cast into ingots with 100 mm in diameter. Microstructures and
macrostructures of samples taken from different part of the cast with different electromagnetic field
conditions were characterized by optical microscopy. The results showed that low frequency
electromagnetic field refines the microstructures and reduces macro-segregation. Unlike casting
without electromagnetic field, the primary Si grains were homogeneous with fine dimensions and the
morphology of the primary silicon exhibited small blocky structures or near-spherical structures.
Further more, decreasing frequency is beneficial to the improvement. In the range conditions in the
experiments, the optimum frequency is found to be 15Hz. During casting, the temperature of the
liquid metal in the sump was monitored. The results shown, under LFEC the width of the liquid-solid
region became narrowed and the temperature field in the sump also became homogeneous.
Influence of Scandium on Microstructures and Mechanical Properties of Al-Zn-Mg-Cu-Zr Alloys
Authors: Dai Xiao Yuan , Xia Chang Qing , Wu An Ru , Peng Xiao Min
Published: March 2009

The effect of minor scandium addition on the microstructures and mechanical properties of
Al-Zn-Mg-Cu-Zr alloys has been studied. Three alloys were produced by casting and then extruded
to rods. Tensile properties of these alloys in different condition were tested. The relationship between
mechanical properties and microstructures of the alloys was discussed in detial. The results showed
that the tensile strength of Al-9.0Zn-2.5Mg-1.2Cu-0.15Zr-0.12Sc and Al-9.0Zn-2.5Mg-1.2Cu-
0.15Zr-0.20Sc in solution and T6 reaches 763.7MPa and 774.6MPa, respectively, while the
elongation remains 5.7% and 8.3%, respectively.
Microstructures and Mechanical Properties of an Al-Cu-Li-Mg-Zr Alloy Containing Zn and Mn
Authors: Chen Yong Lai , Li Jin Feng , Zhang Yu Wei , Zheng Zi Qiao
Published: March 2009

An Al-3.43Cu-1.28Li-0.49Mg-0.12Zr containing 0.62Zn and 0.29Mn was designed and
the microstructures and mechanical properties of the alloy with various heat treatments were
investigated. The precipitates of the alloy consist of T1 (Al2CuLi), θ′ (Al2Cu)
σ (Al5Cu6Mg2) and δ′
(Al3Li). As solution temperature is changed from 485°C to 530°C, the solution degree of alloying
elements in alloy increased, the amount of T1 in the alloy aged at 160°C for 18 h increased and that of
θ′ is decreased, resulting in an increase of strength. After solution treatment at 530°C, the alloy aged
for 18 h at 145°C is mainly strengthened by G P zones, and a little amount of T1 precipitates. As aging
temperature is increased to 160°C and 175°C, the strength increased, due to the sufficient
precipitation of σ and T1. The smaller amount of T1 in the alloy aged at 190°C is consistent with its
lower strength. Meanwhile, it is found that the σ precipitate does not coarsen as aging temperature
increases in the range from 160°C to 190°C.
Static Recovery and the Orthogonal Strain Path Change Effect in IF Steel
Authors: Bate Pete S. , Brough Ian , Morse S.
Published: March 2009

Tensile tests have been carried out in the rolling and transverse directions of 'interstitialfree' (IF) steel cold rolled to a strain of εh= -0.18. Tests in the transverse direction showed the characteristic features of the orthogonal strain path change effect, with an initially increased flow stress- compared to tests in the rolling direction- followed by a transient regime of very low strain hardening. Tests were also carried out following recovery annealing of the prestrained sheet at 500°C and 600°C. Static recovery had a marked effect on the strain-induced anisotropy, but this was not eliminated even when the cell structure generated by prestraining haD condensed to one consisting of low-angle boundaries. This supports the view that the length scale, with respect to active slip systems, between boundary obstacles is a significant factor in the orthogonal path change effect.
Texture Evolution in Invar® Deformed by Asymmetrical Rolling
Authors: Chhann Sorphal , Solas Denis , Etter Anne Laure , Penelle Richard , Baudin Thierry
Published: March 2009

Asymmetrical rolling, in which the circumferential velocities of the working rolls are different, is a method to impose shear deformation and in turn shear deformation texture to sheet through the thickness. The Invar® alloy has been deformed by asymmetrical rolling with a 84% thickness reduction. The texture of the deformed and annealed alloy was measured by X-ray diffraction at different levels through the thickness: upper side- middle- down side, with unidirectional rolling. The deformed texture is a copper type texture but the components were rotated about 5-7° around the Transverse Direction (TD) axis as compared to the ideal position of these components in the pole figure representation. During recrystallization, the rolling components (brass {011}<112>,copper {112}<111>, aluminum {123}<634>) decrease quickly whereas the cube component {001}<100> is preferentially developed after a short annealing time. However, the rolling components do not disappear completely after complete recrystallization (120 minutes annealing). As a consequence the final texture contains a high cube component and rolling components.
Tool Thermal Behavior in SPF Environment
Authors: Petiot Alain , Favre Thierry
Published: March 2009

During a superplastic cycle and part loading/unloading operations, a superplastic tool
withstands thermal cycles which affect its life-time, the superplastic cycle time and hence the
productivity of the press. A thermal simulation of the tool behavior in superplastic conditions helps to
understand which actions could reduce the effects of heat-shields opening/closing and of part
loading/unloading on the cooling of the tool and on the heating of the part. Temperature
measurements in transitory conditions and in steady-state have been collected on a tool of large
dimensions in superplastic conditions of production. The paper will present the correlation between
actual measures and simulation in steady state, in slow transitory conditions and in fast transitory
conditions.
Submicrocrystalline Structure Formation in Ti and Ti-64 Alloy by Warm “abc” Deformation
Authors: Zherebtsov Sergey V. , Mironov Sergey , Salishchev Gennady A.
Published: March 2009

Mechanical behavior and microstructure evolution of Ti and Ti-64 titanium alloy during
warm “abc” deformation has been studied. The “abc” deformation was consisted of successive
compression of a sample along three orthogonal directions. Mechanical behavior of each material was
described by set of successive σ-ε curves combined into cumulative σ-Σε curve. Microstructure of Ti
was found to be refined to a grain size of about 0.4 μm due to formation of deformation-induced
boundaries within initial grains. Although a stage like steady state flow was observed at the
cumulative σ-Σε curve such mechanical behavior was hardly associated with superplastic flow. In
two-phase Ti-64 alloy the structure was found to be refined to a grain size of about 0.4 μm after warm
“abc” deformation due to globularization α- and β-particles following breaking down of α-lamellar
and β- layers. Microstructure refinement of the alloy was associated with softening and superplastic
flow.
SPF/DB Research in ZK60 Alloy with Gasification Agent as Pressurization Mediator
Authors: Yu Yan Dong , Wang C.W. , Yin D.L.
Published: March 2009

A new SPF/DB technology using gasification agent as pressurization mediator was
proposed in this paper. The forming principle of SPF/DB using the agent was represented. Dies used
for the forming process was designed and manufactured, and new gasification agent N11 which is
white solid powder at normal temperature and it is easy to encapsulate and keep was developed for
magnesium alloy. ZK60 magnesium alloy with a thickness of 1mm and grain size of 7.9μm was
selected to conduct the experiment of SPF/DB. Corrugated ZK60 magnesium alloy parts were well
formed under the temperature between 653K and 673K and forming time of 50 minutes. SEM was
used to observe the microstructures of the diffusion bonding joints. The result shows that the joints
were well bonded.
The Pilot Study on the Defect Prediction and Numerical Simulation in the Superplastic/ Extrusion of Copper Alloy
Authors: Chen F.X. , Li He Jun , Guo J.Q. , Liu X.Z.
Published: March 2009

The aim of the study on the deformation defect is to prevent defects and to improve the
quality and to control the deformation. It is important that the preventive measure could be established
to advance the scientificity of the product and processing design. In this paper, the reasons of the outer
defects such as cracks are analyzed based on the superplasticity of the copper alloy and the process of
solid cages in the superplastic extrusion. The prediction and numerical simulation of these typical
defects are also carried out using the Deform-3D software grounded on the model of the rigid-visco
plastic FEM. The position, time of crack appearance and relation between the strain rate and the
defects are also studied. The simulated results are in equivalent agreement with the experiment.
Development of Superplastic Properties in Quasi Single Phase Alloys
Authors: Grimes Roger , Dashwood R.J. , Dorban A. , Jackson Martin , Katsas S. , Pong I. , Todd G.
Published: March 2009

The early view of superplasticity was that it was a phenomenon that could only be exhibited
by fine grained, two phase alloys. This effectively ruled out most alloys that possessed attractive
service properties. The first material to demonstrate good superplastic properties from a virtually
single phase microstructure was the Al-6%Cu-0.5%Zr, AA 2004 but this was followed by
superplastic versions of AA7475, AA8090 and AA5083. Superplasticity was also demonstrated in
magnesium based alloys at an early stage.
More recently different grain control additions, such as scandium or erbium have been investigated
and it has also been demonstrated that, in certain circumstances, aluminium simply with the addition
of a grain controlling element can exhibit good superplastic behaviour. While conventional wisdom
teaches that large fabricating strains are required to confer good superplastic properties in the sheet
product, recent results with both aluminium and magnesium alloys cast doubt on this belief.
Although, for many years, strip casting has appeared to provide an attractive semi-fabricating route
for superplastic sheet problems with centre line segregation in alloys with a wide freezing range have
precluded its use. It has been demonstrated that recent developments in strip casting enable
production of alloys with as wide a freezing range as AA5182 to be cast with a fine, equiaxed grain
structure across the strip thickness.
The paper will review the state of these various developments and their implications for the
manufacture of superplastic sheet materials.
Microstructure Evolution of the Ti-6.62Al-5.14Sn-1.82Zr Alloy in the Superplastic Compression
Authors: Li Miao Quan , Pan H.S. , Lin Ying Ying
Published: March 2009

Superplastic compression of the Ti-6.62Al-5.14Sn-1.82Zr alloy were carried out at a
Thermecmaster-Z simulator at deformation temperatures of 960°C, 980°C, 1000°C and 1020°C, strain
rate of 0.001 s-1, 0.01 s-1 and 0.1 s-1, and height reduction of 50%, 60% and 70%. The α phase
decreases with the increasing of deformation temperature, and the grain size of α phase has a slight
variation with the deformation temperature. The strain rate affects both the morphologies and the
grain size of α phase, and the optimal strain rate makes the grains be fine. The optimal height
reduction also makes the α phase be fine and well distributed on the matrix of
Ti-6.62Al-5.14Sn-1.82Zr alloy after superplastic compression.
The Effects of Extrusion Ratio and Friction on Material Microstructures during Sandglass Extrusion Process
Authors: Lu W.L. , Wang Y. , Hai Jin Tao
Published: March 2009

Sandglass extrusion is an ultrafine grain size method. Due to the repetitive and multiple
extrusions, large strain can be accumulated and ultrafine grain size can be obtained. Some factors can
affect the experimental results of sandglass extrusion, such as extrusion ratio, number of extrusion,
extrusion temperature, friction and free space in mould cavity etc. These factors have different effects
on material microstructures, properties and defects. In this paper, the effects of extrusion ratio and
friction on material microstructures during sandglass extrusion process have been discussed and
theory analysis and experimental results have been reported.
Superplastic Properties and Superplastic Forming/Diffusion Bonding of γ-TiAl+α2-Ti3Al Sheet Materials
Authors: Safiullin Rinat V. , Imayev Renat M. , Imayev V.M. , Beck Werner , Froes F.H. , Salishchev Gennady A.
Published: March 2009

The as-cast and hot worked microstructures of the newly developed β-solidifying
ingot-metallurgy Ti-45Al-X (Nb,Mo,B) alloy and its superplastic properties in the hot worked
condition have been studied. The obtained experimental findings were used for research of
superplastic forming and diffusion bonding of sheet products, which were cut out of hot worked
preform by spark cutting. It was shown that superplastic forming might be successfully applied to the
obtained fine-grained sheet materials. Relatively low bonding temperatures and pressures were found
to be sufficient to achieve sound joints in the sheet material.
A Study on Superplastic Behavior and Microstructural Evolution of an Isothermally Forged TiAl Based Alloy
Authors: Ding Hua , Song D. , Pan Z.Q. , Zhang C.P. , Cui J.Z.
Published: March 2009

Superplastic behavior and microstructure evolution of an isothermally forged
Ti-47Al-1Cr-1V-1.5Mo-1.5Nb alloy were investigated. The results showed that the strain rate
sensitivity index, m, increased with strain during the superplastic deformation, and it kept as a
constant when the strain reached a certain value. The maximum value of m was 0.53 at 900°C and
strain rate of 5x10-4 s-1. During the superplastic deformation, the as received material with lamellae
and subgrains were refined due to dynamic recrystallization, and small and equiaxed grains with high
angle boundaries were formed, creating a better condition for superplastic deformation. Grain
boundary sliding and boundary migration were the main superplastic deformation mechanisms and
slip and twining were also very important during the superplastic deformation of the alloy.
Synthesis and Superplastic Deep Drawing of TiAl Alloy
Authors: Han Wen Bo , Wang Z.J. , Wu D.Z. , Wang Guo Feng
Published: March 2009

TiAl alloys are powerful candidates for light weight high temperature structural materials
because of their excellent high temperature strength, low density and good oxidation resistance.
Unfortunately, TiAl alloys are difficult to machine and hot working due to ordered structure, which
impede large-scale application. Synthesis and superplastic deep drawing of a TiAl alloy were studied.
Mechanically synthesized fine crystalline Ti/Al composite powders as precursor of TiAl alloy. The
TiAl alloy with fine grain via reactive sintering was obtained. The deformation behavior under biaxial
stress by means of deep drawing was achieved. The optimum temperature is 1100°C≤T≤1150°C. The
microstructures corresponding to deep drawing in the part were studied.
Microstructures after Bending Deformations to Fracture of Zr Ion Irradiated Superplastic Ceramic 3Y-TZP
Authors: Sakuma Takaaki , Motohashi Yoshinobu , Shibata Taiju , Sawa Kazuhiro , Ishihara Masahiro
Published: March 2009

The effects of Zr ion irradiation on the mechanical properties of a typical superplastic
ceramic, 3mol% yttria stabilized tetragonal zirconia polycrystal (3Y-TZP), were examined and
discussed. The specimens were irradiated by Zr11+ ions with 130MeV at fluence level of 3.5×1012 and
2.1×1013 ions/cm2 in the TANDEM accelerator at Tokai Reasearch Establishment of JAEA.
Microstructures after annealing and bending deformations to fracture of Zr ion irradiated 3Y-TZP
were examined. It was found that the ratio of intergranular fracture to intragranular fracture was
increased in the region that was affected by Zr ion irradiation. It seemed that grain boundary cohesion
became relatively weak in the irradiated surface region. The influence of Zr ion irradiation on the
mechanical properties almost disappeared when the irradiated 3Y-TZP was subsequently heated to
1173K.
Tribology in Superplastic Forming Processing of 3Y-TZP/Al2O3 Ceramic at Elevated Temperatures
Authors: Wang F. , Zhang Kai Feng , Han Wen Bo
Published: March 2009

Superplastic forming processing of ceramic materials at high temperatures and high
pressure puts forward very high requests to moulds and lubricants, at which conditions seeking for
appropriate lubricants is one of important preconditions in the superplastic forming of ceramic
materials. Using ring compressive testing, lubricities of hexagonal boron nitride in superplastic
compressive forming processing of 3Y-TZP/Al2O3 ceramic composite at elevated temperatures were
investigated. Theoretical curves of friction factor were drawn according to upper bound method. Ring
compressive tests were adopted at temperature of 1400 °C-1600 °C. The results indicate that when
BN is used, friction factor is about 0.4, meanwhile friction factor don’t have great changes with higher
temperature and increasing strain rate. X-ray diffraction shows that under high temperature and high
pressure no boron nitride converts to cubic phase, which remains at room temperature.
Superplastic Joining of TZP Enhanced by Titania-Doping in the Insert Material
Authors: Takigawa Yorinobu , Takadama Hiroaki , Higashi Kenji
Published: March 2009

Superplastic joining of 3mol% Yttria stabilized tetragonal zirconia polycrystal (3Y-TZP) is
examined using 5wt%TiO2-doped 3Y-TZP as an insert material, in order to decrease the joining
temperature and stress and to realize the local deformation near the joining surface. The joining tests
are conducted by uniaxial compression in a temperature range of 1523 to 1723K. The joined specimen
is characterized by a scanning electron microscopy (SEM), showing a clean interface with no
cavitation. Four point bending tests are conducted to evaluate the joining strength, resulting an
average flexural strength of 960MPa in the specimen joined at 1573K for sample compressed at
10MPa for 30 min, which is 80% of the strength of 3Y-TZP matrix. The temperature of 1573K is
100K lower than that obtained in sample without the insert material. Fracture occurs not at joining
surface but at matrix in bending test. Residual stress is suggested to be introduced during joining
process.
Superplasticity and Microstructure Evolution of Electrodeposited Nanocrystalline Nickel
Authors: Ding S. , Zhang Kai Feng , Wang Guo Feng
Published: March 2009

Nanocrystalline pure nickel (nc-Ni) was produced by pulse electrodeposition and its
superplastic properties at and above room temperature were investigated. The electrodeposited nickel
has a narrow grain size distribution with a mean grain size of 70nm. Uniaxial tensile tests at room
temperature showed that nc-Ni has a limited plasticity but high tensile strength up to 1GPa at strain
rates between 10-5 and 10-2s-1. However, when the temperature increased to 420 and higher, test
specimens showed uniform deformation and the elongation value was larger than 200%. A maximum
elongation value of 380% was observed at 450°C and a strain rate of 1.67x10-3s-1, SEM and TEM
were used to examine the microstructures of the as-deposited and deformed specimens. The results
indicated that fracture was caused by intergranular cracking and most cracks were originated from the
brittle oxide formed during the tensile test. Grain coarsening was observed in the deformed specimen.
The role of temperature and strain on grain growth was evaluated by comparing the microstructure of
deformed samples with that of samples statically annealed. Deformation mechanism was discussed
based upon the deformed microstructure and strain rate jump tests.
High Resolution Surface Studies of Superplastic Deformation
Authors: Rust Martin A. , Todd Richard I.
Published: March 2009

Previous studies of superplasticity using surface markers have tended to use either diamond
paste scratches, with which it is difficult to make quantitative measurements, or regular grids with
spacing greater than the grain size, which prevents measurements of any deformation occurring
within the grains. This paper reports the etching of regular marker grids with submicron line spacings
using Focused Ion Beams (FIB), as well as mesoscopic grids with line spacings many grains across.
These have enabled us to make quantitative measurements of deformation within the surface grains,
and at length scales up to 0.5 millimeters. Further refinements used include the use of Interferometric
Surface Profilometry to measure the out-of-surface displacement during deformation. Results on
Sn-Pb eutectic alloy tested in tension in Regions I and II showed that there was almost no
intragranular deformation anywhere in any of the surface grains. Grain boundary sliding took place,
particularly at Sn-Sn grain boundaries, and the accommodation mechanism was separation of
interfaces normal to the tensile axis where sliding was blocked, particularly Pb-Pb grain boundaries. It
is argued that this is a surface artifact not readily available in the bulk thus the case is made for testing
under a different strain condition.
The Effect of Strain Rate History on the Dynamic Grain Growth Behaviour of AA 5083
Authors: Zhang B. , Bate Pete S. , Ridley Norman
Published: March 2009

Dynamic grain growth in superplastic AA5083 deformed at constant strain rates and
varying strain rates has been studied. It has been found that the strain rate history has a significant
influence on the grain growth behaviour. It is proposed that differences in mechanical behaviour of
AA5083 for the strain rate conditions examined can be attributed to differences in the grain growth
behaviour. The influence of dynamic grain growth on the superplastic behaviour of AA5083 is
discussed.
Cavitation Behavior of Fine-Grained 1420 Al-Li Alloy during Superplastic Deformation
Authors: Shao Jie , Guo He Ping , Li Zhi Qiang , Han X.Q.
Published: March 2009

This paper deals with the cavity formation and growth behavior of fine-grained 1420 Al-Li
alloy during superplastic forming. The results indicated that there were many sub-micron cavities
pre-existing at the particle-matrix interface and these sub-micron cavities grew initially under
deformation. Different from uniaxial tension, the cavities nucleation under biaxial tension was
combinable effect of stress concentration and matrix/particle de-cohesion. With the strain and
temperature increasing, the total number and the average size of cavities increased. By the
calculations, it was seen that diffusional growth process dominates the initial stage of void growth,
and for void radii>~1.7μm, void growth was mainly controlled by plasticity.
Design of an Induction Glass Melting Furnace by Means of Mathematical Modelling Using the Finite Element Method
Authors: Arellano Isaac , Plascencia Gabriel , Carrillo Elías , Barrón Miguel A. , Sánchez Adolfo , Gutiérrez Juliana
Published: March 2009

In this paper we propose the design of a novel induction furnace for glass melting. The design is based on a mathematical analysis and performed numerically by means of the Finite Element Method. Several induction coils configurations were tested. The results from the mathematical model show that it is possible to melt glass in a furnace whose hearth is no larger than half a metre by using axial induction coils and high frequencies. This furnace configuration may result in increased glass melting rates along with the elimination of harmful emissions.
Textured α-SiAlON Ceramics via Templated Grain Growth
Authors: Kushan S.R. , Tamsu N. , Acikbas N.C. , Suvaci E. , Mandal Hasan
Published: March 2009

In this study, textured α-SiAlON ceramic was produced by templated grain growth
process. In order to enhance the alignment of the seeds, gated tape casting arrangement was utilized.
Y-Ce codoped seeds were synthesized to induce the preferred orientation. For the production of the
seeds, Ce3+ was used as a sintering additive due to its well-known effect on the formation of
elongated α-SiAlON grains. In addition, Y3+ was used to stabilize Ce3+ in α-SiAlON structure.
Gated tape casting arrangement was also used to enhance the alignment of the seeds in the green
tape. After the lamination and sintering, preferentially aligned α-SiAlON grains were observed by
the microstructural investigation. In addition, XRD results obtained from the planes parallel and
perpendicular to the casting direction indicated the alignment of grains in α-SiAlON ceramics.
Hardness measurements also confirmed that the alignment of the grains results in 8% increase in
hardness value of the plane perpendicular to the casting direction with respect to that of the parallel
one.
Effects of Nano-Structure of Silica on Dynamic Properties of Styrene-Butadiene Rubber
Authors: Lazić N.L. , Budinski-Simendić J. , Ostojić S. , Kićanović M. , Plavšić M.B.
Published: March 2009

Properties of four materials based on styrene-butadiene rubber (SBR), one without filler and the other three with the same amount but different types of silica fillers, are investigated. The fillers used are Vulkasil S and two new fillers, differing in nano-structures: specific surface area and particle aggregate morphology. All other components in the material formulations are the same as well as the procedures of material preparation. Thermal and thermo-mechanical properties of all four materials are investigated by modulated differential scanning calorimetry (MDSC) and dynamic mechanical analysis (DMA). Morphology of the materials is studied using scanning electron microscopy (SEM). The results for glass transition temperature (Tg ) of gum rubber and three filled rubbers, obtained by MDSC are for all four materials Tg = -50±1 0C, and by DMA loss tangent measurements also for all of them Tg = -29±1 0C. It indicates no significant influence of active silica fillers on the rubber network segment dynamics, in the temperature range close to Tg of SBR. But, at higher temperatures MDSC gives insights into dynamic transitions that are under the influence of filler interactions and sensitive to filler structure. The difference in Tg results obtained for the same material by MDSC and DMA can be understood in terms of different sensitivity of network segment dynamics to conditions provided by those two measuring methods.
Advances in AlGaN/GaN/SiC Microwave Devices
Authors: Uren Michael J. , Kuball Martin
Published: March 2009

Recent work on the thermal and electrical challenges in realizing AlGaN/GaN microwave
heterojunction field effect transistors grown on SiC substrates is discussed. Raman thermography
has been used to directly measure the self-heating induced lattice temperature rise with dramatically
improved resolution and accuracy compared to traditional infrared techniques. It is demonstrated
that defects in the SiC substrate can influence the temperature distribution within the active device
with potential consequences for reliability. Microwave devices require an insulating GaN substrate
material for device isolation. It is shown that the net deep level acceptor concentration has to be
accurately controlled to suppress short-channel effects and to achieve radio frequency power
efficient operation.
Employing Discontinuous and Continuous Growth Modes for Preparation of AlN Nanostructures on SiC Substrates
Authors: Yazdi Gholam Reza , Syväjärvi Mikael , Vasiliauskas Remigijus , Yakimova Rositza
Published: March 2009

In this report we present results on growth and characterization of AlN wires and thin
films on SiC substrates. We have employed PVT technique in close space geometry for AlN
deposition on SiC off oriented substrates, most of which were prepared to have scratch-free smooth
as-grown surface by SiC sublimation epitaxy. By manipulating the surface kinetics we have been
able to determine growth conditions yielding discontinuous or continuous morphologies
corresponding to nanowires and thin films, respectively. A particular feature of the latter
experiments is the fast temperature ramp up at the growth initiation. The AlN surface morphology
was characterized by optical, AFM and XRD tools, which showed good crystal quality independent
of the growth mode.
Homoepitaxial Growth of Vanadium-Doped 4H-SiC Using Bis-Trimethylsilylmethane and Verrocene Precursors
Authors: Song Ho Keun , Seo Han Seok , Moon Jeong Hyun , Yim Jeong Hyuk , Lee Jong Ho , Kwon Sun Young , Na Hoon Joo , Kim Hyeong Joon
Published: March 2009

The authors attempted to grow a semi-insulating SiC epitaxial layer by in-situ vanadium
doping. The homoepitaxial growth of the vanadium-doped 4H-SiC layer was performed by MOCVD
using the organo-silicon precursor, bis-trimethylsilylmethane (BTMSM, [C7H20Si2]) and the
metal-organic precursor, bis-cyclopentadienylvanadium (Verrocene, [C10H10V]). Vanadium doping
effect on crystallinity of epilayer was very destructive. Vanadium-doped epilayers grown on normal
condition had various surface or crystal defects such as micropipes, polytype inclusions. But this
crystallinity degradation was overcome by high growth temperature. For the measurement of the
resistivity of the highly resistive vanadium-doped 4H-SiC epilayers, the authors used the
on-resistance technique. Based on the measurements of the on-resistance of the epilayers using the
current-voltage technique, it is shown that the residual donor concentration of the epilayers was
decreased with increasing partial pressure of verrocene. The resistivity of the vanadium-doped
4H-SiC epilayer was about 107 /cm.
Low-Temperature Halo-Carbon Homoepitaxial Growth of 4H-SiC: Morphology, Doping, and Role of HCl Additive
Authors: Lin Huang De , Melnychuk Galyna , Wyatt Jeffery L. , Koshka Yaroslav
Published: March 2009

Low-temperature epitaxial growth of 4H-SiC with CH3Cl carbon precursor was further
developed. In-situ doping with nitrogen and aluminum was investigated. The nitrogen concentration
in epitaxial layers grown on the C face was almost two orders of magnitude higher than that in the
Si-face epilayers grown in the same growth run at 13000C. The opposite trend was observed for
intentional aluminum doping, with more than an order of magnitude higher aluminum concentration
incorporated in Si-face epilayers. High values of nitrogen and aluminum doping well in excess of
1020 cm-3 without any obvious epilayer morphology degradation can be achieved on C-face and Siface
respectively. Addition of HCl during halo-carbon growth at 13000C resulted in drastic
improvement of the surface morphology. Also, a significant increase of the growth rate took place
confirming that the improvement in the epilayer morphology during HCl-assisted growth is
predominantly related to silicon cluster etching by additional Cl-containing vapor species.
Morphology and Stress Control in UHVCVD of 3C-SiC(100) on Si
Authors: Pezoldt Joerg , Förster Christian , Stauden Thomas , Cimalla Volker , Morales Francisco M. , Zgheib Charbel , Masri Pierre M. , Ambacher Oliver
Published: March 2009

The influence of the growth conditions on the 3C-SiC layer quality in terms of crystallinity,
morphology and residual strain was investigated. In dependence on the chosen growth conditions
the stress state can be varied between inhomogeneous and homogeneous strain. For the reduction
of the residual strain an alternative route for the improvement of the epitaxial growth of 3CSiC(
100) on Si(100) was developed. It consists in covering the silicon wafers with germanium prior
to the carbonization step. The achieved improvement in the residual strain and crystalline quality of
the grown 3C-SiC layers is comparable to SOI substrates. These beneficial effects were reached by
using a Ge coverage in the range of 0.5 to 1 monolayer with respect to the silicon surface.
Trends in Dopant Incorporation for 3C-SiC Films on Silicon
Authors: Zielinski Marcin , Portail Marc , Peyre Hervé , Chassagne Thierry , Ndiaye S. , Boyer Bernard , Leycuras André , Camassel Jean
Published: March 2009

We have investigated the influence of several growth parameters on the incorporation of
doping species in the case of 3C-SiC layers grown by CVD on silicon. This includes nitrogen (both
intentional and residual) as well as residual aluminum. All concentrations have been determined by
SIMS (Secondary Ion Mass Spectrometry). First, we investigated the effect of the growth
temperature, growth rate and C/Si ratio on the doping level of (100) oriented layers. Then, we
compared the change in nitrogen incorporation versus nitrogen flow rate for layers grown on (100),
(111), (110) and (211) oriented wafers.
Behavior of Basal Plane Dislocations and Low Angle Grain Boundary Formation in Hexagonal Silicon Carbide
Authors: Chen Yi , Dhanaraj Govindhan , Vetter William M. , Ma Rong Hui , Dudley Michael
Published: March 2009

The interactions between basal plane dislocations (BPDs) and threading screw and edge
dislocations (TSDs and TEDs) in hexagonal SiC have been studied using synchrotron white beam
x-ray topography (SWBXT). TSDs are shown to strongly interact with advancing basal plane
dislocations (BPDs) while TEDs do not. A BPD can cut through an individual TED without the
formation of jogs or kinks. The BPDs were observed to be pinned by TSDs creating trailing
dislocation dipoles. If these dipoles are in screw orientation segments can cross-slip and annihilate
also potentially leaving isolated trailing loops. The three-dimensional (3D) distribution of BPDs can
lead to aggregation of opposite sign edge segments leading to the creation of low angle grain
boundaries (LAGBs) characterized by pure basal plane tilt of magnitude determined by the net
difference in densities of the opposite sign dislocations. Similar aggregation can also occur against
pre-existing prismatic tilt boundaries made up of TED walls with the net difference in densities of
the opposite sign dislocations contributing some basal plane tilt character to the LAGB.
Defect and Growth Analysis of SiC Bulk Single Crystals with High Nitrogen Doping
Authors: Kato Tomohisa , Miura Tomonori , Wada Keisuke , Hozomi Eiji , Taniguchi Hiroyoshi , Nishizawa Shin Ichi , Arai Kazuo
Published: March 2009

In this study, we report defect analysis in 4H-SiC crystals of high nitrogen doping grown by
sublimation method, and we discuss key points for defect restraint. The growth was performed in two
kinds of growth directions; c-axis and a-axis. In the c-axis grown crystal with carrier density greater
than 1×10-19cm-3, defect propagation was confirmed in the vertical direction for a growth direction
affected by the doping by x-ray topography. This phenomenon was not observed in the a-axis grown
crystals. In sublimation growth, the quantity of impurities tends to increase as growth rate decreases.
Therefore, in the c-axis growth of doped 4H-SiC bulk crystals, we have to be careful so that dopant
does not increase too much without intention in grown layers with lower growth rate, for example at
the beginning and end of the growth.
Epitaxial Growth on Metal Bonded SiC Substrates: Transmission Electron Microscopy and Photoluminescence
Authors: Matko Igor , Chenevier Bernard , Bluet Jean Marie , Madar Roland , Letertre Fabrice , Saikaly Wahib
Published: March 2009

QuaSiC TM substrates can be obtained by transferring a single crystal SiC layer onto a
poly SiC substrate using the Smart Cut TM technology. In order to overcome the difficulty of limited
thickness, an important improvement has been demonstrated, which consists in obtaining thick SiC
structure by growing epitaxial SiC layers on top of transferred layers. The aim of this work is a
structural analysis of such layers by Transmission Electron Microscopy and Photoluminescence.
Effect of Growth Conditions on Cubic Silicon Carbide Crystals Grown from Silicon Solution
Authors: Eid Jessica , Santailler Jean Louis , Ferrand Bernard , Rolland Guy , Burdin Michel , Lewandowska R. , Camassel Jean
Published: March 2009

We report the effect of changing the growth conditions in the case of bulk 3C-SiC
crystals grown by the Travelling Zone Method when the seed is placed on the top graphite rod.
First, we investigated the effect of changing the temperature gradient and the cooling ramp. Next
we studied the effect of changing the seed polytype and misorientation. Every time, working in the
1700 °C temperature range, the grown polytype was 3C. From X-ray analysis we evidenced a better
hetero-epitaxial relationship between the seed and layer when a low misorientation angle was used.
Better quality and homogeneity were obtained on the first 500 .m of the layer and, beyond this
thickness, micro-Raman measurements show that the effect of solvent (Si) incorporation is not yet
fully under control.
EPR, ESE and Pulsed ENDOR Study of Nitrogen Related Centers in 4H-SiC Wafers Grown by Different Technologies
Authors: Kalabukhova Ekaterina N. , Lukin S.N. , Savchenko D.V. , Mitchel W.C. , Greulich-Weber Siegmund , Gerstmann Uwe , Pöppl Andreas , Hoentsch J. , Rauls E. , Rozentzveig Yurii , Mokhov E.N. , Syväjärvi Mikael , Yakimova Rositza
Published: March 2009

D-band electron paramagnetic resonance (EPR) measurements as well as X and Q-band
field-swept Electron Spin Echo (ESE) and pulsed Electron Nuclear Double Resonance (ENDOR)
studies were performed on a series of n-type 4H-SiC wafers grown by different techniques including
sublimation sandwich method (SSM), physical vapor transport (PVT) and modified Lely
method. Depending on the C/Si ratio and the growth temperature the n-type 4H-SiC wafers revealed,
besides a triplet due to nitrogen residing on the cubic site (Nc), two nitrogen (N) related EPR
spectra with g||=2.0055, g⊥=2.0010 and g||=2.0063, g⊥=2.0005 with different intensities. In the samples
with low C/Si ratio the EPR spectrum with g|| =2.0055, g⊥=2.0010 consists of a triplet with low
intensity which is tentatively explained as a N-related complex, while in the samples with high C/Si
ratio the triplet is transformed into one structureless line of high intensity, which is explained as being
due to an exchange interaction between N donors. In the samples grown at low temperature with
enhanced carbon concentration the EPR line with g||=2.0063, g⊥=2.0005 and a small hyperfine (hf)
interaction dominates the EPR spectrum. It is attributed to N on the hexagonal lattice site. The interpretation
of the EPR data is supported by activation energies and donor concentrations obtained
from Hall effect measurements for three donor levels in this series of 4H-SiC samples.
Impurity Conduction in Silicon Carbide
Authors: Krieger M. , Semmelroth Kurt , Weber Heiko B. , Pensl Gerhard , Rambach Martin , Frey Lothar
Published: March 2009

We report on admittance spectroscopy (AS) investigations taken on aluminum (Al)-
doped 6H-SiC crystals at low temperatures. Admittance spectra taken on Schottky contacts of
highly doped samples (NA ≥ 7.2×1017 cm-3) reveal two series of conductance peaks, which cause
two different slopes of the Arrhenius plot. The steep slope is attributed to the Al acceptor, while the
flatter one - obtained from the low temperature peaks - is attributed to the activation energy ε3 of
nearest neighbor hopping. We propose a model, which explains the unexpected sharpness of the
low temperature conductance peaks and the disappearance of these peaks for low acceptor
concentrations. The model is verified by simulation, and the AS results are compared with
corresponding results obtained from resistivity measurements taken on 4H- and the identical 6HSiC
samples.
Optical Investigation of Cubic SiC Layers Grown on Hexagonal SiC Substrates by CVD and VLS
Authors: Habka Nada , Soulière Véronique , Bluet Jean Marie , Soueidan Maher , Ferro Gabriel , Monteil Yves
Published: March 2009

We report an optical investigation of cubic Silicon Carbide (3C-SiC) layers grown on
6H-SiC substrates by Chemical Vapour Deposition and Vapour-Liquid-Solid mechanism. Micro-
Infrared reflectance ('-IR), micro-Raman ('-Raman) and low temperature photoluminescence
spectroscopies were used for the characterisation of such layers. '-IR measurements showed
unusual optical behaviour of 3C-SiC layers. The difference of refraction index between the 3C-SiC
film and the 6H-SiC substrate cannot explain this result. The experimental '-IR reflectance
spectrum was modelled by introducing a thin (thickness ≤ 0.5 'm) metallic-like (doping ≥ 1020
at.cm-3) interfacial film between the layer and the substrate. The photoluminescence spectra
revealed the presence of a peak which may be attributed to recombination at the 3C/6H interface.
All these results suggest the presence of a two dimensional electron gas at the interface.
Temperature Dependence of the Band-Edge Injection Electroluminescence of 3C-SiC pn Structure
Authors: Strel'chuk Anatoly M. , Lebedev Alexander A. , Savkina N.S. , Kuznetsov Alexey N.
Published: March 2009

We present the injection electroluminescence spectra in the temperature range 290-760 K
of 3C-SiC pn structure, which was fabricated by sublimation epitaxy in vacuum on 6H-SiC
substrate. The dominant emission band of injection electroluminescence (IEL) spectrum was
observed in the green region; at room temperature the IEL intensity outside the region of hν ≈ 2.0-
2.5 eV was less than 3% of that of the green peak. The peak parameters at room temperature are:
hνmax ≈ 2.32 eV, full width at half maximum w ≈ 100 meV. The green peak shifted in the longwave
direction with increasing temperature; the hνmax (T) dependence was linear with the slope of -
1.3x10-4 eV/K. Both the IEL intensity of the green peak at hνmax and band width w increased upon
heating. The w(T) dependence was linear with the slope of 4.6x10-4 eV/K; intensity increased with
the activation energy of 70 meV. The green IEL band can be considered to be due to the free
exciton annihilation or to the band-band recombination and edge IEL increasing with rising
temperature can be explained by the nonequilibrium charge carriers lifetime increasing.
Influence Of Growth Conditions on Irradiation Induced Defects in 4H-SiC
Authors: Pintilie Ioana , Irmscher K. , Grossner Ulrike , Svensson Bengt Gunnar , Thomas Bernd
Published: March 2009

Nitrogen doped 4H-SiC epitaxial layers grown by hot-wall chemical vapor deposition
were investigated by Deep Level Transient Spectroscopy after irradiation with 6 MeV electrons at
room temperature. This study is focusing on the influence of nitrogen doping and C/Si ratio on the
behaviour of the Z1,2 and EH6,7 levels which occur in already as-grown material but are substantially
enhanced by electron and ion irradiation. It was found that both the Z1,2 and EH6,7 concentrations
increase with both the nitrogen doping and the C/Si ratio. However, while the Z1,2 concentration
increases during post-irradiation thermal treatment the opposite holds for the EH6,7 level especially
in silicon rich samples. On the basis of these results, the influence of carbon and nitrogen on the
formation of the Z1,2 complex is reconfirmed and a possible identity of the EH6,7 defect is discussed.
Thick Epilayer for Power Devices
Authors: Henry Anne , ul Hassan Jawad , Pedersen Henrik , Beyer Franziska Christine , Bergman Peder , Andersson Sven , Janzén Erik , Godignon Philippe
Published: March 2009

Growth of thick epitaxial SiC layers needed for high power devices is presented for
horizontal hot-wall CVD (HWCVD) reactors. We demonstrate thickness of epilayer of 100 μm and
more with good morphology, low-doping with no doping variation through the whole thick layer
and reasonable carrier lifetime which mainly depends on the substrate quality. Typical epidefects
are described and their density can dramatically be reduced when choosing correctly the growth
conditions as well as the polishing of the surface prior to the growth. The control of the doping and
thickness uniformities as well as the run-to-run reproducibility is also presented. Various
characterization techniques such as optical microscopy, AFM, reflectance, CV, PL and minority
carrier lifetime have been used. Results of high-voltage SiC Schottky power devices are presented.
Sodium Enhanced Oxidation of Si-Face 4H-SiC: A Method to Remove Near Interface Traps
Authors: Sveinbjörnsson E.Ö. , Allerstam Fredrik , Ólafsson H.Ö. , Gudjónsson G. , Dochev D. , Rödle T. , Jos R.
Published: March 2009

We demonstrate how sodium enhanced oxidation of Si face 4H-SiC results in removal of
near-interface traps at the SiO2/4H-SiC interface. These detrimental traps have energy levels close
to the SiC conduction band edge and are responsible for low electron inversion channel mobilities
(1-10 cm2/Vs) in Si face 4H-SiC metal-oxide-semiconductor field effect transistors. The presence of
sodium during oxidation increases the oxidation rate and suppresses formation of these nearinterface
traps resulting in high inversion channel mobility of 150 cm2/Vs in such transistors.
Sodium can be incorporated by using carrier boats made of sintered alumina during oxidation or by
deliberate sodium contamination of the oxide during formation of the SiC/SiO2 interface.
Initial Stages of the Graphite-SiC(0001) Interface Formation Studied by Photoelectron Spectroscopy
Authors: Emtsev Konstantin V. , Seyller Thomas , Speck Florian , Ley Lothar , Stojanov P. , Riley J.D. , Leckey R.C.G.
Published: March 2009

Graphitization of the 6H-SiC(0001) surface as a function of annealing temperature has
been studied by ARPES, high resolution XPS, and LEED. For the initial stage of graphitization –
the 6√3 reconstructed surface – we observe σ-bands characteristic of graphitic sp2-bonded carbon.
The π-bands are modified by the interaction with the substrate. C1s core level spectra indicate that
this layer consists of two inequivalent types of carbon atoms. The next layer of graphite (graphene)
formed on top of the 6√3 surface at TA=1250°C-1300°C has an unperturbed electronic structure.
Annealing at higher temperatures results in the formation of a multilayer graphite film. It is shown
that the atomic arrangement of the interface between graphite and the SiC(0001) surface is
practically identical to that of the 6√3 reconstructed layer.