bluuebunny/crossref_metadata_2025 huggingface dataset:
SiC MOSFET Channel Mobility Dependence on Substrate Doping and Temperature Considering High Density of Interface Traps
Authors: Pérez-Tomás Amador , Jennings Michael R. , Mawby Philip  Andrew , Covington James A. , Godignon Philippe , Millan José , Mestres Narcis
Published: March 2009

In prior work we have proposed a mobility model for describing the mobility degradation
observed in SiC MOSFET devices, suitable for being implemented into a commercial simulator,
including Coulomb scattering effects at interface traps. In this paper, the effect of temperature and
doping on the channel mobility has been modelled. The computation results suggest that the
Coulomb scattering at charged interface traps is the dominant degradation mechanism. Simulations
also show that a temperature increase implies an improvement in field-effect mobility since the
inversion channel concentration increases and the trapped charge is reduced due to bandgap
narrowing. In contrast, increasing the substrate impurity concentration further degrades the fieldeffect
mobility since the inversion charge concentration decreases for a given gate bias. We have
good agreement between the computational results and experimental mobility measurements.
Simulation Study of High-k Materials for SiC Trench MOSFETs
Authors: Tappin Peter , Mahapatra Rajat , Wright Nicolas G. , Bhatnagar Praneet , Horsfall Alton B.
Published: March 2009

This report investigates the advantages of high-k materials as gate dielectrics for high
power SiC trench MOSFET devices, by means of TCAD simulation. The study makes a
comparison between the breakdown characteristics of gate dielectrics comprising SiO2, HfO2 and
TiO2. I-V and Transfer functions show forward characteristics with on-state resistivity of
8.27 m*⋅cm2, 8.65 m*⋅cm2, 15.8 m*⋅cm2 for the respective devices, at a gate voltage of 20 V. The
threshold voltage is 10 V for all devices. The blocking voltage for the HfO2 and TiO2 is increased
from 1800 V (for the SiO2 device) to 2200 V. With a peak electric field of 12 MV/cm through the
oxide of the SiO2 device is reduced to 3.2 MV/cm for the HfO2 and 2.3 MV/cm for the TiO2
devices.
Reliability of SiC Power Devices Against Cosmic Radiation-Induced Failure
Authors: Soelkner Gerald , Kaindl Winfried , Treu Michael , Peters Dethard
Published: March 2009

Cosmic radiation has been identified as a decisive factor for power device reliability.
Energetic neutrons create ionizing recoils within the semiconductor substrate which may lead to
device burnout. While this failure mode has gained widespread acceptance for power devices based
on silicon the question whether a similar mechanism could also lead to failure of SiC devices was
left to be debated. Radiation hardness intrinsic to the SiC material was generally assumed but as
experimental data was scarce reliability problems due to radiation-induced device failure could not
be ruled out. Recent accelerated testing results now show that cosmic radiation will indeed affect
the reliability of SiC power devices, as it is the case for its silicon counterpart, but the problem can
be contained very effectively by device design.
Breakdown Voltage Characteristics of FLR-Assisted SiC-SBD Formed by Aluminum Metal Junction Edge Termination
Authors: Kim S.J. , Choi Y.S. , Yu S.J. , Kim Sang Cheol , Bahng Wook , Lee K.H.
Published: March 2009

This paper demonstrates the breakdown voltage characteristics of different edge
termination structures including aluminum (Al)-deposited guard ring and Al-deposited guard ringassisted
field limiting ring (FLR) for a 4H silicon carbide (SiC) Schottky barrier diode (SBD). In
order to investigate the application feasibility of the Al-deposited junction termination to a high
breakdown voltage SiC-SBD, two types of SiC-SBDs are fabricated using conventional
photolithography, electron beam evaporation, and thermal treatment techniques without ion
implantation and thermal oxidation procedures. The breakdown voltage characteristics of the SiCSBDs
are significantly dependent on the Al-deposited edge termination. The SiC-SBD without the
Al-deposited edge termination shows less than 250 V breakdown voltage, while the Al-deposited
guard ring and Al-deposited guard ring-assisted FLR structures show roughly 700 V and 1200 V
breakdown voltages, respectively. The prominent improvement in the breakdown voltage
characteristics is attributed to the electric field lowering at the Schottky contact edge by the Al
deposition edge termination.
Improvement of SBD Electronic Characteristics Using Sacrificial Oxidation Removing the Degraded Layer from SiC Surface after High Temperature Annealing
Authors: Kinoshita Akimasa , Nishi Takashi , Yatsuo Tsutomu , Fukuda Kenji
Published: March 2009

Ion implantation and a subsequent annealing at high temperature are required for
fabricating a high voltage Schottky Barrier Diode (SBD) with a field limiting ring (FLR) or a junction
termination extension (JTE), but high temperature annealing degrades surface condition of a SiC
substrate and induces a degradation of electronic characteristics of a fabricated SBD. To avoid a
degradation of SBD electronic characteristics after high temperature annealing, the method of
removing a degraded layer from a SiC surface by sacrificial oxidation after high temperature
annealing is studied. In this study, we studied the relationship between the improvement of SBD
electronic characteristics and the thickness of sacrificial oxide grown after high temperature
annealing. 9~12 SBD without edge termination were fabricated on a SiC substrate of 4mm×4mm. The
ratio of good chips to all chips (9~12 SBD) increases with increasing total thickness of sacrificial
oxide grown after high temperature annealing at 1800oC for 30 s, where an SBD with a leakage
current less than 1μA/cm2 at reverse voltage of –100V was defined as a good chip. We applied this
process growing sacrificial oxide of 150nm after high temperature annealing to fabricate the SBD
with an FLR structure designed with 600V blocking voltage on a Si-face SiC substrate. The SBD with
an FLR structure through this process of 150 nm sacrificial oxide is low leakage current of less than
1μA/cm2 at reverse voltage of –100V and achieves 600V blocking voltage, however, the SBD with an
FLR structure without the process of sacrificial oxide after high temperature annealing is high leakage
current at reverse voltage of –100V. It is shown that this process growing sacrificial oxide after high
temperature annealing is useful to fabricate an SBD with an FLR structure.
Simulation, Fabrication and Characterization of 4H-SiC Floating Junction Schottky Barrier Diodes (Super-SBDs)
Authors: Ota Chiharu , Nishio Johji , Hatakeyama Tetsuo , Shinohe Takashi , Kojima Kazutoshi , Nishizawa Shin Ichi , Ohashi Hiromichi
Published: March 2009

The calculation for 4H-SiC floating junction Schottky barrier diodes (Super-SBDs) was
carried out by device simulation and the optimized device structure was fabricated. The best
characteristics of the Super-SBDs were breakdown voltage of 2700V and the specific on-resistance of
2.57m*cm2. The world record of Bariga’s Figure of Merit (BFOM) for SiC-SBD expressed by
4Vbd
2/Ron was improved to 11,354MW/cm2.
An Inserted Epitaxial Layer for SiC Single Crystal Growth by the Physical Vapor Transport Method
Authors: Seo Jung Doo , An Joon Ho , Kim Jung Gon , Kim Jung Kyu , Kyun Myung Ok , Lee Won Jae , Kim Il Soo , Shin Byoung Chul , Ku Kap Ryeol
Published: March 2009

SiC single crystal ingots were prepared onto different seed material using sublimation PVT
techniques and then their crystal quality was systematically compared. In this study, the conventional
SiC seed material and the new SiC seed material with an inserted SiC epitaxial layer on a seed surface
were used as a seed for SiC bulk growth. The inserted epitaxial layer was grown by a sublimation
epitaxy method called the CST with a low growth rate of 2μm/h. N-type 2”-SiC single crystals
exhibiting the polytype of 6H-SiC were successfully fabricated and carrier concentration levels of
below 1017/cm3 were determined from the absorption spectrum and Hall measurements. The slightly
higher growth rate and carrier concentration were obtained in SiC single crystal ingot grown on new
SiC seed materials with the inserted epitaxial layer on the seed surface, maintaining the high quality.
1.2 kV Pin Diodes with SiCrystal Epiwafer
Authors: Vang Heu , Raynaud Christophe , Brosselard Pierre , Lazar Mihai , Cremillieu Pierre , Leclercq Jean Louis , Scharnholz Sigo , Planson Dominique , Chante Jean-Pierre
Published: March 2009

Silicon carbide devices limitations often originate from the quality of the substrate
material. Therefore it is interesting to investigate devices fabricated on alternative source materials.
Currently, CREE is the world market leader of SiC wafers. Nowadays, some new companies begin
to propose alternative material. The European manufacturer SiCrystal furnishes now some
epiwafers for the fabrication of 1,2kV devices. In this paper we present 4H-SiC 1.2 kV pin diodes
with a JTE termination realized on a SiCrystal epiwafer. The devices exhibit a blocking voltage of
1.2 kV, a current density of 420 A.cm-2 and a specific differential series resistance of 4.4 m-⋅cm2.
The yield of fabricated diodes with a breakdown voltage greater 600 V is superior to 75%.
Coupling between the Raman Spectroscopy and Photoemission Microscopy Techniques: Investigation of Defects in Biased 4H-SiC pin Diodes
Authors: Thuaire Aurelie , Mermoux Michel , Bano Edwige , Crisci Alexandre , Baillet Francis , Zekentes Konstantinos
Published: March 2009

Raman spectroscopy and photoemission microscopy were coupled as two complementary
non-destructive optical techniques in order to study biased 4H-SiC pin diodes. These two
characterization tools have been largely used for the study of semiconductors but the combination of
these two techniques has hardly been reported so far. Some structural defects inducing the same
electrical damage could be discriminated and identified. Temperature could be measured in
operating devices and the influence of the diode operating mode on the Raman signal could be
evidenced.
Effects of Very High Neutron Fluence Irradiation on p+n Junction 4H-SiC Diodes
Authors: Moscatelli Francesco , Scorzoni Andrea , Poggi Antonella , Passini Mara , Pizzocchero Giulio , Nipoti Roberta
Published: March 2009

In this work we analyzed the radiation hardness of SiC p+n diodes after very high 1 MeV
neutron fluence. The diode structure is based on a p+ emitter ion implanted in n-type epilayer with
thickness equal to 5 %m and donor doping ND = 3×1015 cm-3. Before irradiation, the average leakage
current density at 100 V reverse bias was of the order of 3 nA/cm2. These devices were irradiated at
four different fluence values, logarithmically distributed in the range 1014-1016 (1 MeV)
neutrons/cm2. After irradiation the epilayer material became more resistive, as indicated by the
reduction of the forward and reverse current density at a given voltage. In particular, after a neutron
fluence of 1×1014 n/cm2 the epilayer active doping concentration decreased to 1.5×1015 cm-3. After
irradiation at 1016 n/cm2, i.e. the highest fluence value, the average leakage current density at 100 V
reverse bias decreased to values of the order of 0.1 nA/cm2. This very low noise even after very high
fluence is very important to obtain a high signal to noise ratio even at room temperature.
Electrical Characterization of High Voltage 4H-SiC pin Diodes Fabricated Using a Low Basal-Plane Dislocations Process
Authors: Ivanov Pavel A. , Levinshtein Michael E. , Boltovets Mykola S. , Krivutsa Valentyn A. , Palmour John W. , Das Mrinal K. , Hull Brett A.
Published: March 2009

Forward current-voltage (I-V) characteristics and non-equilibrium carrier lifetime, τ
were measured in 4H-SiC pin diodes (10-kV rated, 100 μm base width). The τ value was found to
be 3.7 μs at room temperature by measurements of open circuit voltage decay. To the best of the
authors' knowledge, the above lifetime value is the highest reported for 4H-SiC. The forward
voltage drops were measured to be 3.44 V at current density of 100 A/cm2 and 5.45 V at 1000
A/cm2 showing a very deep modulation of the blocking base by injected carriers. Diodes operated
well at elevated temperatures up to 400oC. No essential forward degradation was detected after 300-
A×min current stress at 400oC.
Surface Functionalization of SiC for Biosensor Applications
Authors: Petoral Jr. R.M. , Yazdi Gholam Reza , Vahlberg C. , Syväjärvi Mikael , Lloyd Spetz Anita , Uvdal K. , Yakimova Rositza
Published: March 2009

SiC is a biocompatible material and a candidate as a transducer for biosensors. Here we
have investigated the possibility to functionalize SiC with biomolecules. We have also processed
very simple devices and performed electrical characterization. Double polished SiC samples with a
C-face substrate and Si-face low doped epilayer have been functionalized on both sides. The SiC
was first treated by HF in order to remove the native oxide, partly successful on the Si-face side but
probably not on the C-face side. MPTMS, 3-mercaptopropyl trimethoxysilane, was chosen as the
biomolecule since it has both a silanol group to be used as an anchoring group to the substrate and a
thiol group available for further linking possibilities. The functionalization was evaluated by XPS,
contact angle experiments, AFM and electrical measurements. The MPTMS molecules attached
with the thiol (or sulphur containing) group pointing out from the surface on both faces of the SiC.
Interesting differences between the two faces are however revealed by the analysis.
Analysis of Novel Packaging Techniques for High Power Electronics in SiC
Authors: Rashid S.J. , Johnson C. Mark , Udrea F. , Mihaila Andrej , Amaratunga G. , Malhan Rajesh Kumar
Published: March 2009

A novel high temperature wire bondless packaging technique is numerically investigated
in this paper. Extraction of device effective resistivity with temperature from numerical
characteristics of 1.2kV 4H-SiC MOSFETs at a current density of 400A/cm2 have demonstrated a
T−2 temperature dependence. Electro-thermal finite element analysis (FEA) of 1.2kV 4H-SiC
MOSFETs sandwiched between two etched direct-bonded-copper substrate tiles has been
performed. The thermal resistance of the ceramic sandwich package shows a 75% reduction in
thermal resistance compared to conventional wire bonded assemblies. Mechanical analysis of the
assembly has been used to investigate the residual stresses in the SiC dies at room temperature,
which are then alleviated at higher temperatures during device operation. Mismatch of the
expansion coefficients of the auxiliary materials in the assembly result in elevated stresses at full
load operation, however these are well below the tensile strength of the respective materials and
hence do not compromise the mechanical integrity of the package.
Microwave p-i-n Diodes and Switches Based on 4H-SiC
Authors: Zekentes Konstantinos , Camara Nicolas , Romanov L.P. , Kirillov A.V. , Boltovets Mykola S.
Published: March 2009

4H-SiC p-i-n diodes were designed, fabricated and characterized for use in microwave
applications. The diodes exhibited a blocking voltage of 1100 V, a 100 mA differential resistance of
1-3 &, a capacitance below 0.5 pF at a punchthrough voltage of 100 V and a carrier effective
lifetime between 15-27 ns. Single 4H-SiC p-i-n diode switches, operating in X-band, exhibited
insertion loss 0.7 dB, isolation up to 25 dB and were able to handle microwave power up to 2.2 kW
in pulsed mode of operation. The switching speed of the switches has not exceeded 20 ns.
Mixed Vertex - Monte Carlo Model of Recrystallization
Authors: Piękoś Krystian , Tarasiuk Jacek , Wierzbanowski Krzysztof , Bacroix Brigitte
Published: March 2009

The generalized deterministic vertex model was successfully used to study the recrystallization process and the corresponding results were published elsewhere [1]. In its classical form the vertex model has analytical formulation, basing on the total energy (i.e. boundary energy and stored energy) minimization. A change of grain boundary configuration in classical vertex model is found by the calculation of vertex velocities. Consequently, a global and complex system of equations has to be solved in each step. In order to simplify calculations and to handle the problem in a more flexible way, the statistical model was proposed. Typical elements of Monte Carlo algorithm were incorporated into the vertex model: a random (and small) modification of microstructure is accepted with the probability proportional to Boltzmann factor. This approach is closer to the stochastic nature of recrystallization process. The model was used to study the recrystallization of 70% and 90% cold rolled polycrystalline copper. It predicts correctly recrystallization textures for high and low strains.
Recovery in 15%Cr Ferritic Stainless Steel after Large Strain Deformation
Authors: Belyakov Andrey , Tsuzaki Kaneaki , Kimura Yoshisato , Mishima Yoshinao
Published: March 2009

15%Cr ferritic stainless steel was machined in rectangular samples and then processed by
multiple forging to a total cumulative strain of 7.2 at an ambient temperature. The large strain
deformation resulted in almost equiaxed submicrocrystalline structure with a mean grain/subgrain
size of 230 nm and about 2.2×1014 m-2 dislocation density in grain/subgrain interiors. The annealing
at a relatively low temperature of 500oC did not lead to any discontinuous recrystallizations. The
grain/subgrain size and the interior dislocation density slightly changed to 240 nm and 2.1×1014 m-2,
respectively, after annealing for 30 min, while the Vickers hardness decreased from 3140 MPa in
the as-processed state to 2900 MPa. This annealing softening was attributed to remarkable release
(by 50%) of internal stresses, which are associated with a non-equilibrium character of
strain-induced grain/subgrain boundaries.
Effect of the Intercalation of the Carbon Layer on the Kinetics of Grain Growth of FePt Magnetic Thin Film during Ordering Reaction - A Monte Carlo Simulation Study
Authors: Kim M.C. , Kim D.A. , Park Joong Kuen
Published: March 2009

The effect of carbon addition on the grain growth and ordering kinetics of FePt film has
been experimentally studied by sputter-depositing a monolithic FePt-20at.%C film of 24 nm. Carbon
addition of 20at.% to FePt thin film in a form of FePt (20 nm)/Cn (4 nm) (n = 1, 4) significantly
reduced both the grain growth and ordering kinetics. Reducing the thickness of carbon layer, i.e. from
n = 1 to n = 4, led to a much finer grain size distribution as well as to a finer grain size. The Monte
Carlo simulation study indicated that the decrease of grain growth and ordering kinetics is primarily
due to a continuous decrease of the mobility of order – disorder inter-phase with the progress of
ordering reaction. This can eventually lead to a stable 2-phase grain structure inter-locked by low
mobility inter-phases and is responsible for the formation of a fine grain size distribution in the
FePt/Cn film with n = 4.
Grain Refinement of High-Purity FCC Metals Using Equal-Channel Angular Pressing
Authors: Horita Z. , Kishikawa Kaoru , Kimura Keiichi , Tatsumi Kohei , Langdon Terence G.
Published: March 2009

Equal-channel angular pressing (ECAP) is a valuable technique for refining grain sizes
to the submicrometer or the nanometer range. This study explores the reason for the difference in
the grain refining behavior between pure Al and pure Cu. First, very high purity levels were adopted
in order to minimize any effects of impurities: 99.999% for Al and 99.99999% for Cu. Second, high
purity (99.999%) Au was also used in order to examine the effect of stacking fault energy. All three
pure metals were subjected to ECAP and microstructural observations and hardness measurements
were undertaken with respect to the number of ECAP passes. It is concluded that the stacking fault
energy plays an important role and accounts for the difference in the grain refining behavior in the
ECAP process.
Annealing Texture of ECAE Processed Copper
Authors: Suwas Satyam , Kim Dong Ik
Published: March 2009

The paper deals with the evolution of recrystallization texture during annealing of Equal Channel Angular Extrusion (ECAE) processed copper with different deformation texture that may evolve as a result of different routes of ECAE. The deformation and recrystallization texture components have been separated and corresponding texture analysis has been carried out. An attempt has been made to understand the origin of recrystallization texture.
Recovery and Recrystallization as a Function of Deformed Microstructure Orientation in Coarse Grained Cold-Rolled Ni
Authors: Chen H.S. , Godfrey Andrew , Hansen Niels , Liu Qing
Published: March 2009

The effect of crystal orientation on the recovery and recrystallization of cold-rolled Ni
(99.96% purity) has been investigated. Particular attention was paid to the annealing response of
regions with either the Copper (C), Brass (B) or S rolling texture orientations. Samples with an
initial average grain size of approx. 500μm were deformed to strains of up to εvM = 4.5. As a result
of the large initial grain size, even after high rolling reductions it is possible to find sufficiently large
regions of material with similar crystal orientation to analyze the recovery and recrystallization
behaviour as a function of crystal orientation. Microstructural investigations were carried out in the
scanning electron microscope using both electron channeling contrast and electron backscatter
diffraction orientation mapping. Both the S and C orientation regions exhibit a heterogeneous
microstructure containing bands of localized deformation. The presence of volumes surrounded by
high angle boundaries in these regions strongly influences both the recovery and recrystallization
behaviour of the material. Twinning was observed also to play an important role in the generation of
recrystallized grains, with twin chains of up to 3 generations being observed.
Microstructure Control Using Recrystallisation in Particle-Containing Fe3Al Alloys
Authors: Kobayashi Satoru , Zaefferer Stefan
Published: March 2009

A fine grained and recovered structure with densely formed fine particles has been created
by means of a thermomechanical process (TMP) in Fe3Al (bcc derivative structure)-based alloys. The
TMP consists of the following two parts; the first part is grain refinement and the second the creation
of recovered structure stabilized by fine particles. It was found in the first part that coarse particles are
required in the process of deformation to refine grain size by particle stimulated nucleation (PSN)
mechanism. Fine M2C type carbide particles were densely precipitated in the second part. These
particles were observed to inhibit the growth of subgrains formed around coarse particles during
annealing at 700°C. This result suggests that if the fine particle density remains high, the recovered
structure can be maintained at 700°C.
On the Thermal Stability of ECAP Deformed FCC Metals
Authors: Molodova Xenia , Gottstein Günter , Hellmig Ralph Jörg
Published: March 2009

Pure Cu, CuZr and an Al-alloy were processed by Equal Channel Angular Pressing (ECAP) at room temperature applying route Bc. Microstructure evolution during ECAP and subsequent annealing was investigated. The deformed and annealed states were characterized by EBSD, TEM and microhardness tests. The microstructure variation was recorded and compared to the behavior of conventional cold rolled material. The study revealed a very low thermal stability of ECAP deformed pure Cu samples compared to cold rolled material with same total strain. However, the thermal stability was significantly improved by alloying with Zr. In contrast, ECAP deformed Al-alloy showed higher thermal stability than cold rolled material.
On the Recrystallisation Characteristics and Kinetics of a 9SMn28 Free Cutting Steel
Authors: Somani Mahesh C. , Karjalainen L. Pentti , Bianchi Juan H.
Published: March 2009

The static and metadynamic recrystallisation characteristics of a 9SMn28 (EN 1.0715)
free cutting steel have been evaluated by employing the stress relaxation technique. In the steel, the
sulphur was bound in the form of numerous MnS inclusions. Fractional softening laws stating the
kinetics of static and metadynamic softening behaviour were experimentally determined and
compared with the existing literature data for C/C-Mn steels. The analysis of the static
recrystallisation data suggested the powers of the strain and strain rate to be -2.7 and -0.13,
respectively, and the apparent activation energy was estimated as 177 kJ/mol. The power of grain
size was taken from a regression model developed previously that is able to predict the static
recrystallisation kinetics of vast number of carbon and microalloyed steel grades. Even though a
fraction of Mn was out of the solid solution in the form of sulphides, the predictions by the
regression model as accounting the balance Mn in the solid solution were quite close to the
experimental data, confirming the applicability of the model. As expected, the metadynamic
recrystallisation behaviour showed a strong dependence on the strain rate, the power being -0.78
and the apparent activation energy 57 kJ/mol.
Mapping Partially Recrystallised Structures by 3DXRD
Authors: West S.S. , Winther Grethe , Margulies L. , Knudsen Erik , Sørensen Henning O. , Schmidt Søren , Juul Jensen Dorte
Published: March 2009

A partially recrystallised sample has been characterised by 3DXRD. A gauge volume of 200μm × 700μm × 300μm has been fully mapped. Deformed and recrystallised regions within the selected gauge volume are distinguished based on the sharpness of the diffraction spots. Information corresponding to a 5D (Φ1, Φ, Φ2, z, x · y) map is deducted from the 3DXRD data.
An Analysis of Strain Path Effects on Static Recrystallisation in Hot Worked Aluminium Alloy AA5052 Using Forward and Reverse Torsion
Authors: Wynne Bradley P. , Hernandez-Silva O. , Lopez-Pedrosa M. , Rainforth Mark W.
Published: March 2009

The effects of strain path reversal, using forward and reverse torsion, on the
microstructure evolution in the aluminium alloy AA5052 have been studied using high resolution
electron backscatter diffraction. Deformation was carried using two equal steps of forward/forward
or forward/reverse torsion at a temperature of 300°C and strain rate of 1s-1 to a total equivalent
tensile strain of 0.5. Sections of the as-deformed gauge lengths of both test specimens were then
annealed at 400°C for 1 hour in a salt bath in order to investigate their subsequent recrystallisation
response. In both strain path histories the deformation substructure in the grains analysed consisted
of microband arrays within an equiaxed dislocation cell structure. The material subjected to
forward/forward deformation did, however, have a slightly greater number of low angle boundaries,
i.e. boundaries < 15° misorientation, whilst the forward/reverse material had some grains containing
little evidence of substructure. On annealing both materials had significantly reduced levels of low
angle boundaries but only the forward/forward material had an increased number of high angle
boundaries and a reduced grain size, indicating recrystallisation had only occurred in this material.
This would suggest that the deformation microstructure within the forward/forward condition was
sufficient to initiate and maintain recrystallisation whilst the microstructure produced by the
forward/reverse test contained insufficient nuclei or internal energy to produce a recrystallised
material within 1 hour. Further work is now required at different annealing times in order to
determine if the major effect of strain path is on retarding nucleation, growth or both.
Recrystallization Characteristics of Commercially Pure Titanium Rolled at Elevated Temperatures
Authors: Chun Y.B. , Hwang Sun Keun
Published: March 2009

Effect of deformation temperature on subsequent recrystallization characteristics of commercial purity titanium (CP-Ti) was investigated using EBSD and transmission electron microscopy. CP-Ti plates were rolled to at various temperatures between 25°C and 600°C to achieve 60% reduction, and were subsequently annealed at 600°C for various time periods. Increase in rolling temperature resulted in more refined microstructures, which could be attributed to coactivation of secondary slip systems such as basal  slip or pyramidal  slip in addition to prism  slip. During subsequent annealing, a large number of recrystallization nuclei formed in the warm-worked (below 450°C) CP-Ti while nucleation of recrystallization was slower for coldrolled one. This led to the faster recrystallization kinetics and a finer microstructure in asrecrystallized state for warm-worked CP-Ti. Meanwhile, the rate of recrystallization in CP-Ti rolled at 600°C was significantly retarded because a good portion of strain energy stored in deformed matrix was released by dynamic recovery. In the present work, we show that the widely accepted explanation for the influence of the deformation temperature on the recrystallization characteristics, i.e., increase of the deformation temperature retards the recrystallization process, is not always true for the hcp metals since deformation at elevated temperature activates secondary slip systems, providing more sites for nucleation of recrystallization.
Boundary Mobilities during Recovery and Recrystallization of Binary Al - Mn Alloys
Authors: Barou F. , Guillotin A. , Maurice Claire , Feppon J.M. , Driver Julian H.
Published: March 2009

This paper described new characterization methods and data to quantify the influence of solute atoms on grain boundary and sub-grain boundary mobilities in Al-Mn alloys with a view to their integration into recovery and recrystallization modelling. Detailed SEM measurements of grain boundary mobilities during recrystallization have been made by in-situ annealing experiments on cold deformed Al – 0.1 and 0.3wt.% Mn binary alloys. Stored energies are estimated from the sub-grain sizes and misorientations and the boundary velocities directly measured in the temperature range 200-450°C. It is shown that in many cases good agreement with the Cahn, Lücke, Stüwe model for solute drag is obtained, e.g. the activation energies are intermediate between those of boundary and volume solute diffusion. Some particular cases of rapid growth occur in Al-0.1%Mn indicating boundary breakaway from solute clouds. A complementary study of sub-grain boundary mobilities has started on the same alloys; in this case the average mobilities are estimated from FEG-SEM growth data for the average sub-grain size for temperatures in the range 150-300°C. The results are compared with some previous data on Al- Si and show similar rates.
Modelling of the Dynamic Processes of Structure Formation by Macroscopic Parameters of Plastic Deformation
Authors: Ryabicheva Lyudmila , Usatyuk Dmytro
Published: March 2009

In this paper, the phenomenological approach which connects the recrystallization
parameters with thermomechanical characteristics of deformation is implemented to simulation of
structural transformations. Two cases were considered, when the growth rate of recrystallized
volumes is damping fast, and when a weak growth of recrystallized grains is observed. A pattern of
structural states was obtained among the models with fast decrease in growth rate of recrystallized
grain and weak grain growth. The abatement of the sensibility to the intensity of grain growth with
increasing of strain rate was established. The function of recrystallized volume has oscillating
behaviour depending on time and coefficient of recrystallization intensity. These results were
confirmed by experimental researches of rheological behaviour of steels at low strain rates and high
temperatures.
The Development of Homo and Heterogeneous Rolling Microstructures in Rolled Low Carbon and Interstitial-Free Steel
Authors: Duggan B.J. , Quadir M.Z. , Tse Y.Y. , Shen K. , Liu G.L. , Chen Q.Z.
Published: March 2009

The relationship between the deformation orientation distribution function (ODF) and the primary recrystallised ODF in cold and warm rolled metals, is not a simple mathematical transformation from one to the other, but is through thermally activated processes occurring in the deformation microstructure. In BCC metals the mature rolling microstructure consists of cells, microbands and shear bands on a length scale of fraction of a micron, to deformation and transition bands at the grain scale, when this is of the order of 10 or more microns. There is evidence that grain boundary regions are sometimes distinct from grain interiors. Wherever there is a relatively sharp change in either orientation or microstructure such locations are potential sites of recrystallisation nuclei. In this paper the results of a systematic investigation of the development of microstructure in rolled interstitial free (IF) steel using both transmission and scanning electron microscopy are presented. It is shown how the dislocation mesh structure, formed at the earliest stages of rolling, develops into the mature microstructure consisting of cells, microbands and shear bands. Deformation heterogeneities in the microstructure, known to be of vital significance in the recrystallisation process are associated with the α and γ fibre components of the rolling texture. Shear band thickening and α grain fragmentation are also considered, since both processes can produce recrystallisation nuclei, which in the α fibre case can reduce desirable mechanical properties.
Novel Approaches to the Thermodynamis of Grain Boundaries and Grain Boundary Junctions
Authors: Shvindlerman Lasar S. , Gottstein Günter
Published: March 2009

Three recent investigations in the field of thermodynamics of grain boundaries and grain boundary junctions are presented. 1. The grain boundary excess free volume (BFV) along with the surface tension belongs to the major thermodynamic properties of grain boundaries. A special technique, recently developed, makes it possible to measure the BFV for practically any grain boundary and provides a way of estimating the grain boundary excess free volume for grain boundaries of different classes with rather high accuracy. The experimental values of the BFV measured for different grain boundaries are compared and discussed. 2. A new approach will be presented that makes it possible to correctly measure the grain boundary triple line tension. For this the topography at an equilibrated triple junction was measured by atomic force microscopy. Preliminary results of grain boundary triple line energy measurements are presented. 3. The problem is discussed whether it is possible to achieve an equilibrium grain size during grain growth in single phase alloys. Various approaches to the problem are considered. It is shown that the most realistic possibility to stabilize the grain size in a polycrystal is by impurities with negative grain boundary adsorption.
Annealing Behavior during Heating Rate of Ultrafine-Grained 5052 Al Alloy deformed at Cryogenic Temperature
Authors: Gang Ui Gu , Park Dae Bum , Nam Won Jong
Published: March 2009

The microstructural evolution during thermal annealing of a cryogenic rolled 5052 Al alloy
was investigated. The activation energy for annealing behavior was calculated using DSC data. For
the heating rate of 16°C/min, the precipitation occurred at the annealing temperature of 150~230°C
due to Mg self diffusion, recovery occurred at the annealing temperature of 230~260°C, and
recrystallization proceeded at a higher temperature up to about 370°C. Both recovery and
recrystallization gave rise to non-uniform, bimodal grain-size distributions, which may result from
heterogeneous nanostructures. In addition, the activation energy for the precipitation was found as
~115kJ/mol, indicating the process was diffusion-controlled (Mg in Al), and the activation energy for
recovery was found to be ~140kJ/mol, representing self-diffusion in pure Al.
Characteristic Microstructure and Grain Boundary Motion in Secondary Recrystallization of Fe-3%Si Alloys
Authors: Suzuki Shigeru , Takebayashi Shigeto , Ushigami Yoshiyuki
Published: March 2009

The microstructure of Fe-3 mass% Si alloys before secondary recrystallization has been
characterized by analyzing precipitates and grain boundary segregated elements. The samples used
were mainly sheets of Fe-3%Si alloys containing manganese, sulfur, aluminum, nitrogen and tin,
which were decarburized and annealed up to secondary recrystallization. Grain boundary segregation
in primarily recrystallized samples was studied using Auger electron spectroscopy (AES), and
precipitates were analyzed using transmission electron microscopy (TEM) with an energy dispersive
X-ray spectrometer (EDX). AES spectra showed that tin and nitrogen were enriched on grain
boundaries in the Fe-3 mass% Si alloys. TEM/EDX analysis showed that the morphology and
distribution of the fine precipitates such as manganese sulfide and aluminum nitride were influenced
by addition of tin. The characteristic structure formed by secondary recrystallization of grain oriented
silicon steel is considered to be influenced by the fine precipitates and segregation of a small amount
of elements, as the abnormal motion of grain boundaries of the silicon steel was correlated with the
precipitation and segregation of the alloying elements.
Microstructural Mechanisms of Fatigue Failure in PA66 Fibers
Authors: Herrera-Ramírez J. Martin , Bunsell Anthony , Colomban Philippe
Published: March 2009

The behavior of two different types of ultra-high-performance polyamide (PA) 66 fibers under fatigue loading up to failure, and the correlation between the fibers (nano)structures and their structural heterogeneity with fatigue lifetimes, have been studied using scanning electron microscopy, differential scanning calorimetry, wide angle x-ray diffraction and micro-Raman spectroscopy. The role of the microstructure of the fibers in determining fatigue life is presented and the possibility of improving their resistance to fatigue or eliminating the fatigue process will be discussed.
Prediction of Microstructure and Distribution of Solute in Al-Zn-Mg Non-Dilute Alloys
Authors: Soto José Luis , Campillo B. , Juarez-Islas J.A.
Published: March 2009

The microstructure of directional solidified Al-Zn-Mg alloys is characterized and predicted by means of thermal analysis data, multicomponent equations for dendrite growth and data from ternary AlZnMg phase diagram. The resulting microstructure consists of α-Al dendrites with τ precipitates and eutectic in interdendritic regions. Predictions show that at growth velocities up to 9 x 10-4 m/s, the α-Al and τ intermetallic grew simultaneously. Predictions for solute concentration according to the model for dendrite solidification of multicomponent alloys with unequal liquid diffusion coefficients show a good agreement with experimental results.
Fracture Analysis of Superplastic Diffusion Bonding Joints between Titanium Alloy and Stainless Steel
Authors: Wang Min , Dai J.W. , Guo Hong Zhen , Ma C.X.
Published: March 2009

The microstructure and characteristic of fracture between TC4 titanium alloy and
1Cr18Ni9Ti stainless steel bonding joints were analyzed concretely in this paper. For direct SP/DB of
TC4/1Cr18Ni9Ti, the diffusion layer joint was composed of some new phases such as β-Ti, TiFe2,
TiFe, σ-FeCr and α-Fe, and the shear strength could be ensured when the thickness of TiFe/TiFe2
brittle phases was controlled within 3~5μm. In SP/DB of TC4/1Cr18Ni9Ti, the joint status of
microzone in interface was asymmetric and exhibited different fractograph. The bonding area of
fracture could be divided into three zones: similar original interface zone, metallurgical bonding zone
and quasi-metallurgical bonding zone. The interface deficiencies were constitutive of mechanical
bonding area, cavity and impurity.
Joining of Aluminium Alloy and Mild Steel Sheets Using Mechanical Clinching
Authors: Abe Y. , Kato T. , Mori Kenichiro
Published: March 2009

The aluminium alloy and mild steel sheets were joined with mechanical clinching.
Deforming behaviour of the two sheets during the clinching was observed from finite element
simulation and an experiment to avoid defects. The fracture of the upper sheet, necking and
separation are caused by the small upper sheet thickness in the thick total thickness, the small lower
sheet thickness in the thick total thickness and the small lower sheet thickness, respectively. The
joining range for the combination of the upper aluminium alloy sheet of and the lower steel sheet of
is larger than that of the reverse combination. The effect of the difference between the flow stresses
of the two sheets on the deformation behaviour was examined.
Enhanced Red Emission in Lithium Doped CaWO4:Eu3+ and CaMoO4:Eu3+ Phosphor
Authors: Shi Shi Kao , Gao Jing , Zhou Ji
Published: March 2009

The lithium ions doped red-emitting phosphors of (Ca,Eu)WO4 and (Ca,Eu)MoO4 were
synthesized by solid-state reaction method, and their luminescent properties were investigated. The
XRD patterns show that the phosphors are isostructural and share a tetragonal scheelite structure,
even some lithium ions are doped. The excitation spectra consist of broad charge transfer bands in the
short-wave UV region of W6+→O2- and Eu3+→O2- with three sharp lines around 395, 465 and 535 nm
of the Eu3+ 4f excitation transitions. The characteristic emissions of WO4
2- and MoO4
2- are quenched
absolutely and red light emission of Eu3+ exhibits predominate peak around 615 nm due to the electric
dipole energy transition of 5D0→7F2. Excited with 395 nm, the evident enhanced emission of the
phosphors were observed when Li+ doped in the host, which implies that the addition of some Li+ is
beneficial for the energy transfer from WO4
2- or MoO4
2- to Eu3+.
Effect of Mn Substitution on the Structure and Microwave Properties of Nd-Fe-B Nanocomposites
Authors: Xie Guo Zhi , Wang Ping , Zhang Bao Shan , Yuan Liu Kui , Shi Yi , Lin Ping Hua , Lu Huai Xian
Published: March 2009

The influence of Mn content on the structure and magnetic permeability of
Nd3Fe68-xMnxCo18B11 (x = 0, 1, 2) amorphous soft magnetic alloys was studied. The ribbons were
prepared by melt-spining. The permittivity–frequency and permeability–frequency properties were
determined in the microwave frequency regime of 2-18 GHz by vector network analysis. XRD spectra
showed that only α-Fe diffraction peak was observed in the as-spun alloy. It is found that the acquired
complex permittivity and permeability values match the microwave frequency when the 1at% Mn
content doped. The results suggest a new design of microwave absorbers based on electromagnetic
wave absorbing materials.
Nickel Metal Induced Lateral Crystallization of Patterned Amorphous Silicon Thin Film
Authors: Nakagawa Gou , Asano Tanemasa
Published: March 2009

Metal-induced lateral crystallization (MILC) of patterned amorphous silicon(a-Si) thin
film using Ni as a catalyst has been investigated. Ni-MILC grains are based on the growth of
needle-like crystals due to the migration of NiSi2 precipitates, which located at the crystalline front,
along the <111> directions. In the case where the needle-like crystallites collided at the a-Si pattern
edge, not only “turn” or “branch” of the needle-like crystallites toward one of the possible <111>
directions but also the growth along the pattern edge were observed. By limiting the growth area, the
competitive growth of dendrite crystals that originated in needle-like crystallites was found to appear.
This phenomenon resulted in the orientation alignment of MILC crystals in a wide area. Besides, the
grain-filtering of MILC crystals was found to be possible by narrowing the pattern width.
A Splats Obtaining System for Thermal Spray Deposits
Authors: Hsiao W.T. , Liao W.H. , Leu M.S. , Su Cherng Yuh
Published: March 2009

The image of thermal spray splats is difficult to collect due to its high velocity of
droplets. Especial in High Velocity Oxy-Fuel (HVOF) process, the process present higher velocity
of flame jet correlated to other thermal spray process. The system presents at this article describes a
useful splats catching method to obtaining splats during thermal spray deposited. Capabilities and
advantages of using this instrument are declared at this theme. The final result presented the
instrument caught the single spot of HVOF sprayed splats at sub-micro second. Splats of spot were
dispersed well on the glass substrate at the obtaining system, and presented various information of
droplets impact at different location on the substrate.
Size Controlled ZnO Nanoparticles Prepared by Water-in-Oil Microemulsion
Authors: Han D.Y. , Shen C.B. , Shi Wei Wei , Li D.D. , Chao Zu Bin , Zhao De Zi
Published: March 2009

ZnO nanoparticles were carried out by Microemulsion method in the presence of
TritonX-100 (poly oxyethylene tert-octylphenyl ether) as a surfactant. X-100/n-hextnol/cyclohexane/
waterW/O microemulsion system was also determined. Zinc chloride (ZnCl2·2H2O) and ammonia
(NH3·H2O) were used as raw materials. The results indicated that the formation of ZnO nanoparticles
was confirmed, using X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The
results showed that the nanoparticle was exactly ZnO with wurtzite type crystalline structure and the
size of nanoparticles is strongly affected by the ratio of water to surfactant(R). With the R value
increase, the particles size became larger.
Comparison of Mechanical Properties between As-Quenched and Annealed Metallic Glass Pd44Cu31Ni8P17
Authors: Fukami Takeshi , Fukatani M. , Okai Daisuke , Yamasaki Tohru , Haruyama Osami , Inoue Akihisa
Published: March 2009

In order to examine the correlation between a mechanical property and an excess free volume
for metallic glass Pd44Cu31Ni8P17, longitudinal and transverse ultrasonic velocities were measured to
estimate longitudinal and transverse elastic constants, c11 and c44. An as-quenched sample, an annealed
one at a temperature just below a glass transition temperature Tg and a crystalline one were prepared. The
as-quenched sample contains the excess free volume depending on the preparing process. The Young’s
modulus E, the Poisson’s ratio, a bulk modulus and c12 are estimated using c11 and c44. The values of c11,
c 44 , c12 and E of the as-quenched one are smaller than those of the annealed sample losing excess free
volume by about 0.2 % and much smaller than those of the crystalline one. The Poisson’s ratio for the
as-quenched sample and the annealed one are 0.389 and 0.387, respectively, which are much larger than
that for the crystalline one with 0.349.
Hydrogen Production by Methanol Steam Reforming Using Amorphous Metal Membranes
Authors: Yamaura Shinichi , Uemiya Shigeyuki , Kimura Hisamichi , Inoue Akihisa
Published: March 2009

In this work, we prepared the melt-spun (Ni0.6Nb0.4)70Zr30 amorphous alloy membrane
and designed a catalytic reactor for methanol steam reforming combined with the amorphous
membrane. Comparing the permeated gas with the evaporated gas, it was found that carbon
dioxide (CO2) and carbon monoxide (CO) gases were removed from the permeated gas by using the
amorphous membrane. Therefore, purified hydrogen gas was obtained in the reactor. We
successfully produced pure hydrogen by using the amorphous membrane.
Quasicrystallization of (Zr65Al7.5Cu27.5)95Ti5 Glassy Alloy
Authors: Qiang Jian Bing , Zhang Wei , Inoue Akihisa
Published: March 2009

Phase transformation in the melt-spun (Zr65Al7.5Cu27.5)95Ti5 glassy alloy was
investigated by a combined use of X-ray diffraction (XRD), transmission electron microscopy
(TEM) and differential scanning calorimetry (DSC). It was found that the crystallization mode of
the Zr65Al7.5Cu27.5 glassy alloy was altered by the addition of Ti, and nanometer scaled icosahedral
phase (I-phase) formation was observed in the primary crystallization stage of the
(Zr65Al7.5Cu27.5)95Ti5 quaternary glass, which transformed to the stable Zr2Cu-type phase upon
further annealing. The crystallization behavior of (Zr65Al7.5Cu27.5)95Ti5 glass was further discussed
in terms of the activation energy as compared to that of Zr65Al7.5Cu27.5 alloy.