bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of the 3C-SiC(100) 5x2 Surface Reconstruction Investigated by Synchrotron Radiation Based Grazing Incidence X-Ray Diffraction
Authors: Silly M. , Enriquez H. , Roy J. , D'Angelo M. , Soukiassian P. , Schuelli T. , Noblet M. , Renaud G.
Published: March 2009

In order to give experimental insights on the atomic structure of the Si atomic wires
developing on the β-SiC(100) surface, we use synchrotron radiation-based x-ray diffraction at
grazing incidence to study a network of such atomic lines in a 5x2 surface array. Our results lead to
an accurate surface and sub-surface structure determination evidencing a structure in agreement
with a two adlayer symmetric dimer reconstruction. This atomic structure is significantly different
from the 3x2 surface structure, giving new insights on the Si atomic lines stability.
A Designed Experiment Approach to Improvement and Understanding of the SiC Epitaxial Growth Process
Authors: Oliver James D. , Ponczak Brian H.
Published: March 2009

A series of designed experiments have been conducted over a period of years in a multiwafer,
planetary rotation, epitaxial reactor to quantify the effects of various epitaxial growth process
parameters on the resulting SiC epitaxial layers. This paper summarizes the results obtained through
statistically designed experiments varying process parameters and their resultant effect on the layer
thickness, carrier concentration and the variability of these parameters wafer-to-wafer, and within a
wafer.
Characterization of MOS Capacitors Fabricated on n-type 4H-SiC Implanted with Nitrogen at High Dose
Authors: Poggi Antonella , Moscatelli Francesco , Hijikata Yasuto , Solmi Sandro , Sanmartin Michele , Tamarri Fabrizio , Nipoti Roberta
Published: March 2009

Aiming to minimize the interface state density, we fabricated MOS capacitors on n-type
4H-SiC by using wet oxidation of nitrogen implanted layers. We investigated a wide range of
implantation dose, including a high dose able to amorphise a surface SiC layer with the intent to
reduce the oxidation time. The oxide quality and the SiO2-SiC interface properties were
characterized by capacitance-voltage measurements of the MOS capacitors. The proposed process,
in which nitrogen is ion-implanted on SiC layer before a wet oxidation, is effective to reduce the
density of interface states near the conduction band edge if a high concentration of nitrogen is
introduced at the SiO2-SiC interface. We found that only the nitrogen implanted at the oxide-SiC
interface reduces the interface states and we did not observe the generation of fixed positive charges
in the oxide as a consequence of nitrogen implantation. Furthermore, the concentration of the slow
traps evaluated from the Slow Trap Profiling technique was low and did not depend on the nitrogen
implantation fluence.
Fabrication of MOS Capacitors by Wet Oxidation of p-Type 4H-SiC Preamorphized by Nitrogen Ion Implantation
Authors: Hijikata Yasuto , Yoshida Sadafumi , Moscatelli Francesco , Poggi Antonella , Solmi Sandro , Cristiani Stefano , Nipoti Roberta
Published: March 2009

4H-SiC p-type MOS capacitors fabricated by wet oxidation of SiC preamorphized
by nitrogen ion (N+) implantation have been investigated. The oxidation rate of the SiC layer
preamorphized by high-dose N+ was much larger than that of crystalline SiC, allowing us
to reduce the fabrication time of SiC MOS devices. We found that the presence of the surface
amorphous SiC layer before the oxidation process did not influence the interface state density in
MOS capacitors. Moreover, the shift of the flat-band voltage is not correlated to the amount of
nitrogen in the oxide. On the contrary the density of interface states near the valence band edge
increased according with the high concentration of the implanted N at the oxide–SiC interface,
as in the case of dry oxidation reported by Ciobanu et al. The generation of positive charges
due to the nitrogen embedded inside the oxide layer was smaller compared with dry oxidation.
We discuss the difference between wet and dry oxidation for MOS capacitors fabricated with
N+ implantation.
Evaluation of Specific Contact Resistance of Al, Ti, and Ni Contacts to N Ion Implanted 3C-SiC(100)
Authors: Suzuki Yu , Taguchi Etsushi , Nagata Shouhei , Satoh Masataka
Published: March 2009

The specific contact resistance of Al, Ti and Ni ohmic contacts to N+ implanted
3C-SiC(100) has been investigated by means of TLM method. The p-type epitaxial layer grown on n+
substrate is multiply implanted with N ions with energy ranging from 15 to 120 keV at a total dose of
1.4×1015 cm-2 at room temperature and is subsequently annealed by RF annealer at a temperature of
1400 oC for 10 min in Ar gas flow, resulting in the sheet resistance of 130 0/sq. The deposited Al
layer on the annealed sample shows the extremely low specific contact resistance of about
1×10-7 0cm2. The ohmic contacts of Ti and Ni also show the specific contact resistance of 5×10-6
and 2×10-5 0cm2, respectively. The obtained specific contact resistance is proportional to the
Schottky barrier height of metal cotact to n-type 3C-SiC. The annealing of Ni ohmic contact
above 600 oC results in the considerable reduction of specific contact resistance due to the
silicidation of Ni.
High Temperature Direct Double Side Cooled Inverter Module for Hybrid Electric Vehicle Application
Authors: Buttay Cyril , Johnson C. Mark , Rashid Jeremy , Udrea F. , Amaratunga G. , Tappin Peter , Wright Nicolas G. , Ireland Peter , Yamamoto Takeo , Takeuchi Yuuichi , Malhan Rajesh Kumar
Published: March 2009

In this paper a novel approach to the design and fabrication of a high temperature inverter module
for hybrid electrical vehicles is presented. Firstly, SiC power electronic devices are considered in place of the
conventional Si devices. Use of SiC raises the maximum practical operating junction temperature to well over
200°C, giving much greater thermal headroom between the chips and the coolant. In the first fabrication, a
SiC Schottky barrier diode (SBD) replaces the Si pin diode and is paired with a Si-IGBT. Secondly, doublesided
cooling is employed, in which the semiconductor chips are sandwiched between two substrate tiles. The
tiles provide electrical connections to the top and the bottom of the chips, thus replacing the conventional wire
bonded interconnect. Each tile assembly supports two IGBTs and two SBDs in a half-bridge configuration. Both
sides of the assembly are cooled directly using a high-performance liquid impingement system. Specific features
of the design ensure that thermo-mechanical stresses are controlled so as to achieve long thermal cycling
life. A prototype 10 kW inverter module is described incorporating three half-bridge sandwich assemblies, gate
drives, dc-link capacitance and two heat-exchangers. This achieves a volumetric power density of 30W/cm3.
4H-SiC Planar MESFETs on High-Purity Semi-Insulating Substrates
Authors: Yim Jeong Hyuk , Song Ho Keun , Moon Jeong Hyun , Seo Han Seok , Lee Jong Ho , Na Hoon Joo , Lee Jae Bin , Kim Hyeong Joon
Published: March 2009

Planar MESFETs were fabricated on high-purity semi-insulating (HPSI) 4H-SiC
substrates. The saturation drain current of the fabricated MESFETs with a gate length of 0.5 μm and a
gate width of 100 μm was 430 mA/mm, and the transconductance was 25 mS/mm. The maximum
oscillation frequency and cut-off frequency were 26.4 GHz and 7.2 GHz, respectively. The power
gain was 8.4 dB and the maximum output power density was 2.8 W/mm for operation of class A at
CW 2 GHz. MESFETs on HPSI substrates showed no current instability and much higher output
power density in comparison to MESFETs on vanadium-doped SI substrates.
Critical Reliability Issues for SiC Power MOSFETs Operated at High Temperature
Authors: Tanimoto Satoshi , Suzuki Tatsuhiro , Hanamura Akihiro , Hoshi Masakatsu , Shinohara Toshiro , Arai Kazuo
Published: March 2009

This paper discusses critical reliability issues and their countermeasures for vertically
structured poly-Si gate n-channel power MOSFETs (DMOS) on 4H-SiC when operated at an elevated
temperature of more than 300°C for a long period of time. Two destructive failures were identified in
a storage life test at 500°C: a short-circuit between the source and the gate and a disconnection at the
n+ source contact. The former was caused by interlayer dielectric erosion and/or Al spearing into the
poly-Si gate; the latter was caused by the disappearance of the NiSix contact layer. Effective and
practical countermeasures were devised and implemented. Device lifetime against the three different
failure mechanisms was improved in every case by at least one order of magnitude.
Investigation of Drain Current Saturation in 4H-SiC MOSFETs
Authors: Pennington Gary , Potbhare Siddharth , Goldsman Neil , Habersat Daniel B. , Lelis Aivars J. , McGarrity J.M. , Ashman C.R.
Published: March 2009

Electronic measurement coupled with device and material modeling of lateral longchannel
4H-SiC MOSFETs is used to investigate current saturation. Observed increases in drain
current with increases in temperature are shown to result from a reduction in interface charge
trapping. If trapping is ignored, the saturation current is predicted to decrease with increasing
temperature as a result of interface phonon scattering.
Numerical Investigation of the DC and RF Performances for a 4H-SiC Double Delta-Doped Channel MESFET Having Various Delta-Doping Concentrations
Authors: Kang In Ho , Bahng Wook , Kim Sang Cheol , Joo Sung Jae , Kim Nam Kyun
Published: March 2009

A double delta-doped channel 4H-SiC MESFET is proposed to kick out degradation of the
DC and RF performances caused by the surface traps, by forming a quantum-well-like potential well
and separating an effective channel from the surface. To obtain an optimum device structure, the DC
and RF performances of double delta-doped channel MESFETs having various delta-doping
concentrations but the same pinch-off voltage with that of conventional MESFET were also
investigated. The SilvacoTM simulation results show that the double delta-doped channel MESFET
achieved more improvement of the drain current, the cut-off frequency, and the maximum oscillation
frequency for higher delta-doping concentration near the gate. In all cases, DC and RF performances
for double delta-doped channel MESFETs are much improved than those of the conventional
MESFET.
Realization of Low On-Resistance 4H-SiC Power MOSFETs by Using Retrograde Profile in P-Body
Authors: Fujihira Keiko , Miura Naruhisa , Watanabe Tomokatsu , Nakao Yukiyasu , Yutani Naoki , Ohtsuka Kenichi , Imaizumi Masayuki , Takami Tetsuya , Oomori Tatsuo
Published: March 2009

Inversion-type 4H-SiC power MOSFETs using p-body implanted with retrograde profiles
have been fabricated. The Al concentration at the p-body surface (Nas) is varied in the range from
5×1015 to 2×1018 cm-3. The MOSFETs show normally-off characteristics. While the Ron is 3 cm2 at
Eox = (Vg-Vth)/dox ≅ 3 MV/cm for the MOSFET with the Nas of 2×1018 cm-3, the Ron is reduced by a
decrease in the Nas and 26 mcm2 is attained for the device with the Nas of 5×1015 cm-3. The inversion
channel mobility and threshold voltage are improved with a decrease in the Nas. By modifying the
structural parameter of the MOSFET, a still smaller Ron of 7 mcm2 is achieved with a blocking
voltage of 1.3 kV.
Epitaxial Growth of 4H-SiC on (000-1) C-Face Substrates by Cold-Wall and Hot-Wall Chemical Vapor Deposition
Authors: Stein René A. , Thomas Bernd , Hecht Christian
Published: March 2009

Epitaxial layers have been grown on the (0001) C-face of 2- and 3-inch 4H-SiC wafers.
Growth conditions like temperature, pressure, and C/Si ratio have been varied. In both systems
smooth surface morphologies could be obtained. The main challenge of epitaxial growth on the Cface
of 4H-SiC for electronic device applications seems to be the control of low doping
concentration. High temperature and low pressure are the key parameters to reduce the nitrogen
incorporation. The hot-wall CVD system used for these experiments allowed the application of
higher temperatures and lower pressures than the cold-wall equipment. The lowest doping
concentration of 2.5x1015 cm-3 has been achieved by hot-wall epitaxy using a temperature of
1625 °C, a system pressure of 50 hPa, a C/Si ratio of 1.4, and a growth rate of 6.5 2mh-1. Good
doping homogeneity on 2-inch and 3-inch wafers could be achieved. For a doping level of ND-NA=
3×1015 cm-3 sigma is about 15%.
Film Morphology and Process Conditions in Epitaxial Silicon Carbide Growth via Chlorides Route
Authors: Masi Maurizio , Veneroni Alessandro , Fiorucci A. , La Via Francesco , Foti Gaetano , Mauceri Marco , Leone Stefano , Pistone Giuseppe , Condorelli Giuseppe , Abbondanza Giuseppe , Valente Gian Luca , Crippa Danilo
Published: March 2009

A simplified deposition model, involving both the description of the deposition and of the
film morphology was adopted to quantitatively understand the experimental trends encountered in
the epitaxial silicon carbide deposition in an industrial hot wall reactor. The attention was focused
on the system involving chlorinated species because its really superior performances with respect
the traditional silane/hydrocarbons process. The evolution of the crystalline structure (i.e., from
poly to single) and of the surface roughness can be understood by simply comparing two
characteristic times, like those inherent the surface diffusion and the matter supply to the surface.
Fabrication of a Multi-Chip Module of 4H-SiC RESURF-Type JFETs
Authors: Tamaso Hideto , Shinkai Jiro , Hoshino Takashi , Tokuda Hitoki , Sawada Kenichi , Fujikawa Kazuhiro , Masuda Takeyoshi , Hatsukawa Satoshi , Harada Shin , Namikawa Yasuo
Published: March 2009

We fabricated a multi-chip module of 4H-SiC reduced surface field (RESURF)-type lateral
JFETs. A single chip consists of 4 unit devices of 2.0 mm × 0.5 mm in size, which were isolated
electrically from each other. The multi-chip module consists of 8 chips mounted on an AMC
substrate. The drain current and the breakdown voltage of the module are over 3 A and 771 V,
respectively. The turn-on time and the turn-off time are 36ns and 166ns, respectively. The module
resistance is proportional to the absolute temperature to the 1.05th power.
Texture Invariant Annealing in Severely Deformed Steel
Authors: Tsuzaki Kaneaki , Belyakov Andrey , Yin Fu Xing
Published: March 2009

This paper showed an example of the phenomena that a strong deformed texture does not change after the annealing process in steels. An Fe – 22%Cr – 3%Ni ferritic stainless steel was processed by bar rolling/swaging to a total strain of 4.4 at an ambient temperature, and its annealing behaviour was studied in a temperature range of 400 ~ 700oC. The deformed sample showed a grain size of 200nm, a fraction of high-angle boundary (HAB) of about 0.6, and a strong fiber texture of <110>{uvw}. This texture showed very little change after annealing which was characterised by the development of continuous recrystallization involving recovery processes and followed by a normal grain growth. On the other hand, by annealing a sample that was deformed to total strain of 2.0 containing rather fine grains (270nm) but without a large enough fraction of HAB (0.3), a discontinuous recrystallization took place, and its deformed texture changed considerably.
The Effect of Grain Boundary Junctions on Grain Microstructure Evolution: 3D Vertex Simulation
Authors: Barrales-Mora L.A. , Shvindlerman Lasar S. , Mohles Volker , Gottstein Günter
Published: March 2009

A 3D Vertex Model has been successfully implemented to investigate the evolution of a
special grain assembly during grain growth. The model considers the mean curvature as driving
force for the motion of the vertices and allows the consideration of all parameters affecting the
motion of the system, i.e., grain boundary energy and line tension of the triple lines, as well as grain
boundary (GB), triple line (TL) and quadruple point (QP) mobility as well. The used special
configuration makes it possible to study the influence of all structural elements of a grain boundary
network on the evolution of the system by allowing the steady-state motion of the boundaries of a
shrinking grain. In the present work the different mobilities have been systematically varied and the
evolution of the grain size with time has been studied as a function of TL and QP mobility. The
results of the simulations are finally linked to the different kinetic regimes reached by the system.
Phase Field Model Simulation of Grain Growth in Three Dimensions under Isotropic and Anisotropic Grain Boundary Energy Conditions
Authors: Ko Kyung Jun , Cha Pil Ryung , Park Jong Tae , Kim Jae Kwan , Hwang Nong Moon
Published: March 2009

Phase-field model (PFM) in multiple orientation fields was used to simulate the grain growth in three-dimensions (3-D) for isotropic and anisotropic grain boundary energy. In the simulation, the polycrystalline microstructure was described by a set of non-conserved order parameters and each order parameter describes each orientation of grains. For isotropic grain boundary energy, the simulation showed the microstructure evolution of normal grain growth. For anisotropic grain boundary energy, however, the simulation showed that certain grains which share a high fraction of low energy grain boundaries with other grains have a high probability to grow by wetting along triple junctions and can grow abnormally with a growth advantage of solid-state wetting. The PFM simulation shows the realistic microstructural evolution of island and peninsular grains during abnormal grain growth by solid-state wetting.
Recrystallization of Niobium Single Crystals Deformed by ECAE
Authors: Bernardi Heide H. , Sandim Hugo Ricardo Zschommler , Verlinden Bert , Raabe Dierk
Published: March 2009

High-purity niobium single crystals were deformed by equal-channel angular extrusion (ECAE) at room temperature to an equivalent Von Mises strain of about 1.15. Deformed samples were annealed in vacuum from 500 to 800oC for 1 hour to investigate their microstructure evolution. The microstructure of deformed and annealed samples was characterized by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and Vickers microhardness testing. The deformed structure after one ECAE pass is rather inhomogenous and consists of parallel sets of coarse shear bands whose spacing varies from one region to another in the cylindrical billet. the microstructure within the shear bands consists of elongated subgrains with sizes below 3 μm and lamellar boundaries. The remaining non-sheared regions display a coarser subgrain structure. Recrystallization is virtually absent in samples annealed at 500oC for 1 hour. Nucleation begins mostly within shear bands. The new grains with sizes ranging from 10 to 50 μm are arranged in clusters rather than being homogenously distributed. The recrystallized volume fraction also varies from one region to another indicating an inhomogenous distribution of stored energy. At 700oC, recrystallization is complete after annealing for 1 hour resulting in a structure with a mean grain size of about 100 μm.
Deformation Substructures and Recrystallisation
Authors: Hutchinson W. Bevis
Published: March 2009

The paper surveys various types of dislocation substructure that are created by plastic deformation in metals. Special reference is made to those substructures that accommodate sharp misorientations as these are of fundamental importance to the nucleation of recrystallisation. Several different mechanisms can give rise to high misorientations; these are discussed in terms of the factors that control them and their relationships to orientation and texture. Different mechanisms for nucleation of recrystallisation may occur depending on the type of substructure, allowing some practical control over the final recrystallised texture.
Synthesis and Structural Characterization of Nanoscale BaTiO3 Powders
Authors: Moon S.M. , Cho Nam Hee
Published: March 2009

Nanoscale BaTiO3 powders were prepared by hydro-thermal synthesis as a function of solvent conditions. The size of the BaTiO3 powders was in the range of 20 ~ 100 nm. The variation in the relative volume fraction of the tetragonal phase was analyzed quantitatively by means of XRD and Raman spectroscopy. It was found that the maximum volume fraction of the tetragonal phase was ~ 29 %; this was obtained when the synthesis was performed at a solvent condition R (H2O/(H2O + EtOH)) = 0.25.
The Role of α/γ Orientation Relationships during Ferrite Nucleation in an Fe-Cr-Ni Alloy
Authors: Landheer H. , Offerman S. Eric , Petrov R.H. , Kestens Leo
Published: March 2009

The role of the α/γ orientation relationships during ferrite nucleation is investigated.
EBSD measurements were performed on an especially developed high purity ternary iron-based
alloy with 20 wt.% Cr and 12 wt.% Ni with both austenite and ferrite present at room temperature to
measure the orientation relationship between the austenite and ferrite crystallites. The experimental
results are compared to the nucleation models of Clemm and Fisher and Aaronson and co-workers.
Microstructure Evolution during Tempering of Martensite in a Medium-C Steel
Authors: di Schino Andrea , di Nunzio Paolo Emilio , Lopez Turconi Gustavo
Published: March 2009

To identify the characteristic microstructural length determining the mechanical
properties of a quenched and tempered medium-C steel and its dependence on the prior austenite
grain size, different tempering treatments have been carried out after a fully martensitic quenching.
The resulting microstructures have been analyzed by Orientation Imaging Microscopy (OIM) and
two kind of features have been taken into consideration: packets (i.e. domains delimited by
high-angle boundaries) and cells (domains bounded by low-angle grain boundaries).
The main results can be summarized as follows:
1. A very weak effect of austenite grain size on packet size was found.
2. A finer packet size was measured at mid-thickness with respect to surface after external and
internal water quenching process. This phenomenon was attributed to the effect of the strain path
on the phase transformation during quenching.
3. The through-thickness microstructural gradient remains substantially unchanged after tempering.
4. Grains with high-angle boundaries do not significantly grow after tempering; on the contrary,
low-angle grain boundaries move, fully justifying the hardness evolution with the tempering
temperature.
Microstructure and Mechanical Properties of ZK60 Alloy Sheets during Aging
Authors: Cho Jae Hyung , Jin Y.M , Kim Hyoung Wook , Kang Suk Bong
Published: March 2009

Variations in microstructure and mechanical properties of ZK60 alloy sheets were investigated with aging time. ZK60 alloy sheets with a thickness of 1mm were prepared from a casting ingot followed by homogenization and warm-rolling. Artificial aging process after solution heat treatment (T6) affected both hardness variations and precipitates distributions with aging time. Hardness variations were related to precipitates, i.e. rod-shaped ( 1 β ′ ) or disc shaped ( 2 β ′ ) particles. Rod-shaped ( 1 β ′ ) precipitates mainly consist of Mg and Zn without Zr.
Role of Heavy Deformation in Thermomechanical Processing on the Formation of Ultrafine-Grained Structure in Steels
Authors: Maki Tadashi
Published: March 2009

The formation of ultrafine-grained structure in steels by various thermomechanical
processings is reviewed from a metallurgical point of view. In the recent new type TMCP, ultrafine
ferrite grains with a grain size of about 1μm are obtained when the austenite is heavily deformed at
lower temperatures. In this case, dynamic phenomena such as dynamic recrystallization become
prominent in the process. In the aging after heavy cold rolling of supersaturated matrix phase in
two-phase alloys, the competition between the recovery or recrystallization of matrix phase and the
precipitation of second phase occurs, resulting in various types of two-phase structures including
microduplex structure. Microduplex structure is also obtained by annealing after heavy cold rolling
of coarse two-phase structure in duplex stainless steel and high carbon steel. Recently, various
severe plastic deformation processings, in which very large plastic strain over 4 is applied to the
materials, have been developed to produce ultrafine grained materials with nanocrystalline and/or
submicrocrystalline structures.
Radiation-Induced Recrystallization of U-Mo Fuel Particles and Radiation-Induced Amorphization of Interaction Products in U-Mo/Al Dispersion Fuel
Authors: Ryu Ho Jin , Kim Yeon Soo , Hofman G.L. , Rest J. , Park Jong Man , Kim Chang Kyu
Published: March 2009

Two kinds of radiation-induced structural changes were observed in U-Mo/Al dispersion
fuel: radiation-induced recrystallization of U-Mo fuel particles and radiation-induced amorphization
of interaction products. During irradiation, U-Mo fuel showed refined microstructures of
submicron-size grains due to dynamic recrystallization, occurring initially from pre-existing grain
boundaries. The interaction products formed by interdiffusion between the U-Mo particles and Al
matrix in U-Mo/Al dispersion fuel transformed from crystalline to amorphous during irradiation. In
this paper we deal with both of the phenomena simultaneously.
An Overview of Accomplishments and Challenges in Recrystallization and Grain Growth
Authors: Rollett Anthony D. , Brahme Abhijit P. , Roberts C.G.
Published: March 2009

The study of microstructural evolution in polycrystalline materials has been active for many decades so it is interesting to illustrate the progress that has been made and to point out some remaining challenges. Grain boundaries are important because their long-range motion controls evolution in many cases. We have some understanding of the essential features of grain boundary properties over the five macroscopic degrees of freedom. Excess free energy, for example, is dominated by the two surfaces that comprise the boundary although the twist component also has a non-negligible influence. Mobility is less well defined although there are some clear trends for certain classes of materials such as fcc metals. Computer simulation has made a critical contribution by showing, for example, that mobility exhibits an intrinsic crystallographic anisotropy even in the absence of impurities. At the mesoscopic level, we now have rigorous relationships between geometry and growth rates for individual grains in three dimensions. We are in the process of validating computer models of grain growth against 3D non-destructive measurements. Quantitative modeling of recrystallization that includes texture development has been accomplished in several groups. Other properties such as corrosion resistance are being related quantitatively to microstructure. There remain, however, numerous challenges. Despite decades of study, we still do not have complete cause-and-effect descriptions of most cases of abnormal grain growth. The response of nanostructured materials to annealing can lead to either unexpected resistance to coarsening, or, coarsening at unexpectedly low temperatures. General process models for recrystallization that can be applied to industrial alloys remain elusive although significant progress has been made for the specific case of aluminum alloy processing. Thin films often exhibit stagnation of grain growth that we do not fully understand, as well as abnormal grain growth. Grain boundaries respond to driving forces in more complicated ways than we understood. Clearly many exciting challenges remain in grain growth and recrystallization.
Abnormal Subgrain Growth by Monte Carlo Simulation Based on Hot-Rolled AA5005 Aluminum Alloy Texture
Authors: Wang Sheng Yu , Rollett Anthony D.
Published: March 2009

The subgrain structure of hot rolled aluminum alloy AA 5005 has been characterized on as-received samples using Electron Backscatter Diffraction (EBSD). Based on the OIM scans of RD-ND and TD-ND, 3 dimensional microstructures of subgrains are built up using the 3D Microstructure Builder, which is a method for developing statistically representative digital representations of microstructures. Following the generation of microstructure, different textures were fit to these reconstructed 3D microstructures, based on individual components such as Brass and S textures. For this study, the Brass texture was chosen as an exemplary case. Monte Carlo simulation was used to model subgrain coarsening and visualization was a key to detecting abnormal grain growth. The main objective is to understand the circumstances under which we can expect abnormal (sub-)grain growth to lead to nucleation of recrystallization.
Modelling Dynamic Recovery and Recrystallization of Metals by a New Non-Equilibrium Thermodynamics Approach
Authors: Huang Ming Xin , Rivera-Díaz-del-Castillo Pedro E.J. , van der Zwaag Sybrand
Published: March 2009

A non-equilibrium thermodynamics-based approach is proposed to predict the dislocation density and flow stress at the steady state of high temperature deformation. For a material undergoing dynamic recovery and recrystallization, it is found that the total dislocation density can be expressed as ( )2 ρ = λε& b , where ε& is the strain rate, b is the magnitude of the Burgers vector and λ is a dynamic recovery and recrystallization related parameter.
Controlling the Growth of Cu Particles through Semibatch Process
Authors: Ahn Jong Gwan , Kim Dong Jin , Jang Y.N. , Kim Chong Oh , Chung Hun Saeng , Hai Hoang Tri
Published: March 2009

In order to produce monodispersed particles, two requirements are considered; they are a complete separation of nucleation and growth steps for the formation of particles and an avoidance of their aggregation during the nucleation and growth. In this study, a new method was presented for preparing narrowly size distributed copper powders from CuO slurry by wet chemical reduction with hydrazine used as a reductant. The rapid nucleation was first induced by a very fast reduction of Pd2+ resulted from batch process. Subsequently copper species which contribute to the growth on the formed Pdo nuclei was slowly generated by semibatch process. A complete separation between nucleation and growth therefore was obtained, resulting in a narrow size distribution of final Cu powder product. The effect parameters on the growth such as Pd2+ concentration and temperature were also investigated.
Grain Boundary Character Evolution during Grain Growth in a Zr Alloy
Authors: Bozzolo Nathalie , Sawina Grzegorz , Gerspach Francois , Sztwiertnia Krzystof , Rollett Anthony D. , Wagner Francis
Published: March 2009

Grain boundary character in samples of Zr701 annealed at two different temperatures has been investigated in terms of lattice misorientation. The main difference between the two samples was the extent of grain growth post-recrystallization. The textures were typical for the material. Differences between the texture-based misorientation distribution function (T-MDF) and the microstructure-based MDF (M-MDF) revealed significant preferences for certain grain boundary types, notably those with <11-20> rotation axes.
The Analysis of the Blowing Process with the Top Lance of the Argon Oxygen Decarburization (AOD) in Baosteel
Authors: Li Dong Gang , Chi He Bing , Shao Shi Jie
Published: March 2009

The applications of the single-hole top lance, the 110-three-holes top lance and the
150-three-holes top lance in the speed of the decarburization are compared. The amount of the
Chromium oxidized, and the temperature-increasing speed of the bath is analyzed. The result shows,
if the lance gap is set suitably, the 110-three-holes top lance will be the most beneficial to the stainless
steel-making in the AOD when the high-carbon pre-metal from the EAF is charged.
Microstructure and Mechanical Properties at the Unsteady Areas of Non-Linear Friction Stir Welding
Authors: Takahara H. , Tsujikawa Masato , Chung Sung Wook , Okawa Y. , Higashi Kenji
Published: March 2009

The influence of tool control in non-linear friction stir welding (FSW) on mechanical
properties of joints was investigated. FSW is widely applied to linear joints. It is impossible for five
axis FSW machines, however, to keep all the FSW parameters in optimum conditions at non-linear
welding. Non-linear FSW joints should be made by compromise with the order of priority for FSW
parameters. The tensile test results of butt joints with rectangular change in welding direction on plate
plane (L-shaped butt joints) with various welding parameter change. It was found that turn to the
retreating side is encouraged when welding direction change. And the method of zero inclination tool
angle is effective at non-linear and plane welding.
Microwave-Assisted Synthesis of Phase Pure YFeO3 Nanocrystallite
Authors: Liu Jun , Xie Ji Min , Zhang Hui , Gu Zhan Jun , Lü Xiao Meng
Published: March 2009

Using nitrate precursors, a novel microwave-assisted progress for the preparation of
nanocrystalline pure YFeO3 phase has been developed. Synthesis of perovskite YFeO3 has
been achieved with carbon to enhance microwave absorption, polyvinyl alcohol as inhibitor
and urea as homogeneous precipitator. The precursor led to formation of phase pure YFeO3
nanocrystalline (52-64 nm) after calcination. The obtained YFeO3 samples were characterized
by XRD analysis, N2 adsorption, FT-IR, SEM, TEM, UV-vis/DRS. The synthesis is a fast,
simple and inexpensive process and such nanosized YFeO3 has a potential application in
photocatalysis under visible light irradiation due to its structure of perovskite-type and
photo-absorption property.
Characterization and Microwave Absorption of “Core/Shell”-Type Nanoparticles
Authors: Huang H. , Zhang Xin Fang , Lv B. , Lei J.P. , Sun J.P. , Dong X.L. , Choi Chul Jin
Published: March 2009

The carbon-coated Fe(C), Co(C) and Ni(C) nanocapsules were prepared by a modified
arc-discharge method in methane atmosphere. The nanocapsule powder, 50 % by weight, was mixed
uniformly with paraffin wax to form measurement samples. Their electromagnetic (EM) wave
reflection loss of the composite samples was calculated using the relative complex permeability and
permittivity measured in microwave frequency range of 2-18 GHz. It is indicated that Fe(C), Co(C)
and Ni(C) nanocapsules show the broadband characteristics with strong absorption from 2 to 18 GHz
for a coating thickness of about 2-3 mm. The excellent EM wave absorption properties are mainly
attributed to the proper electromagnetic match in microstructure, strong natural resonance as well as
multi-polarization mechanisms, etc. As an inspiration, we found this kind of nanocapsules with a
dielectric shell and a ferromagnetic core are very promising for new EM wave absorption materials.
Deposition of a Well-Adherent Nano-Crystalline Diamond Coating on Titanium Using CH4-H2 Gas Mixture
Authors: Askari Syed Jawid , Lu Fan Xiu
Published: March 2009

The deposition of a well adherent diamond film on titanium and its alloys is always
complicated due to the different thermal expansion coefficients of the two materials, the complex
nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high
nucleation density. In this work well-adherent and smooth nano-crystalline diamond film was
successfully deposited on pure titanium substrate by microwave plasma assisted chemical vapor
deposition (MWPCVD) method in CH4/H2 environment. It is found that the average grain size was
less than 20 nm with a surface roughness value as low as 28nm. Of particular interest in this study
was the exceptional adhesion of approximately 2μm-thick diamond film to the metal substrate as
observed by indentation testing up to 150 kg load. Experimental results on growth mechanism and
obtaining good adhesion are discussed.
Microstructure and Electrical Properties of Nano Ni-Cr Thin-Films Fabricated by Magnetron Co-Sputtering Techniques
Authors: Zhou Ji Cheng , Yan Jian Wu
Published: March 2009

The nano Ni-Cr thin-film samples with different composition have been fabricated by a
double-target magnetron co-sputtering equipment, through controlling the sputtering power, the
substrate rotate speed, and the substrate temperature, The results showed that the grains sizes with
polycrystalline microstructure were not greater than 10 nm. The crystal microstructure of Ni-Cr
thin-films is Face Centered Cubic (FCC). The dominant texture in the Ni-Cr film was Ni (111) under
this sputtering condition. The lattice parameters of Ni crystal and the inter-planar distances of Ni
(111) increased by Cr solid-soluble in Ni crystal. The surface morphology of the thin-film samples is
smooth and compact. The TCR (temperature coefficient of resistance) value of specimen 3 was
84~130 ppm/k, which show the specimen 3 was the most stable.
Synthesis of Single-Walled Carbon Nanotube Networks on Silicon Nanowires
Authors: Yoshida Hideto , Uchiyama Tetsuya , Kikkawa Jun , Kohno Hideo , Takeda Seiji
Published: March 2009

Single-walled carbon nanotubes (SWNTs) have been synthesized on silicon nanowires
(SiNWs) by ethanol chemical vapor deposition (CVD) using Co catalysts nanoparticles. The surface
SiOx layers assist the formation of catalyst nanoparticles on SiNWs by inhibiting the diffusion of Co
to Si. Co-Si compounds have formed in SiNWs readily when the surface SiOx layers are very thin.
Therefore, the yield of SWNTs is strongly influenced by the thickness of the surface SiOx layers of
SiNWs.
The Role of Deformation Twinning on Creep of Titanium Alloys
Authors: Ankem Sreeramamurthy , Oberson P. Gregory
Published: March 2009

Normally, deformation twinning is a process that occurs at rates approaching the speed of
sound in bulk metals once a critical stress has been reached. However, recently it has been shown
that twins grow at speeds many orders of magnitude lower than the speed of sound during room
temperature creep of titanium alloys. The net result is that this twinning process can contribute to
the low-temperature (less than 0.25*Tm) creep behavior of α, α−β, and β−titanium alloys. For
example, α-Ti alloys with small grain size do not extensively deform by twinning and hence show
little overall creep strain. These recent developments are reviewed in this paper. This work is
funded by the National Science Foundation under Grant Number DMR-0517351.
Ultra-Large Area RF Plasma Sources Employing Multiple Low-Inductance Internal-Antenna Modules for Flat Panel Display Processing
Authors: Setsuhara Yuichi , Takenaka Kosuke , Tsukiyama Daisuke , Nishisaka Kazuaki , Ebe Akinori
Published: March 2009

Plasma-generation and control technologies for meters-scale ultra-large-area RF plasma
sources have been developed with multiple low-inductance antenna (LIA) modules, as a promising
candidate of ultra-large area and high-density (1011-1012 cm-3) plasma sources for next-generation
large-area processing. The present technologies are based on principle of multiple operation and
integrated control of LIA modules, which enables effective control of power deposition profiles and
hence the plasma uniformity over meters-scale large area for processing. This paper presents issues
in designing ultra-large-area plasma sources to demonstrate feasibility of the uniform sources with
3m x 3m scales to meet requirements in the next-generation processes.
Microstructure of 430L Stainless Steel Powders during High-Energy Ball Milling
Authors: Ni Hong Wei , He Hang , Li G.Q. , Zhan Wei Ting , Cang Da Qiang , Dan Z.G.
Published: March 2009

Preparation of nanocrystalline 430L stainless steel powders by high-energy ball milling has
been investigated. The samples were characterized by scanning electron microscope (SEM), X-ray
Diffraction (XRD) and Matersizer. The SEM observation confirmed that the cold welding and
fragmentation behaviors occurred during high-energy ball milling, which has important effect on the
changes of the particle size. In the initial stage (0-10h), particle size increased and crystalline grain
size decreased evidently. The mean particle size got to 330μm and the crystalline grain size got to
23nm for sample of 10h ball milling. In the later stage, the particle size decreased and the refinement
of crystalline grain became difficult. The crystalline grain size of sample for 50h ball milling only got
to 15nm.
Fabrication of Ni52.5Nb10Zr15Ti15Pt7.5 Bulk Metallic Glassy Matrix Composite Containing Dispersed ZrO2 Particulates by Spark Plasma Sintering
Authors: Xie Guo Qiang , Louzguine-Luzgin Dmitri V. , Kimura Hisamichi , Wakai Fumihiro , Inoue Akihisa
Published: March 2009

Spark plasma sintering (SPS), as a developed rapid sintering technique, has a great
potential for producing larger metallic glassy alloy specimens in a variety of shapes than those
fabricated by casting methods, and can readily produce composites by dispersing crystalline particles
in the glassy matrix. In this study, the Ni52.5Nb10Zr15Ti15Pt7.5 bulk metallic glassy matrix composites
dispersed homogeneously with ceramics ZrO2 particulates were fabricated by the SPS process. The
plastic ductility of the Ni52.5Nb10Zr15Ti15Pt7.5 glassy matrix composites was improved by adding ZrO2
particulates into the glassy alloy. The matrix of the fabricated composites maintained a glassy phase
after the SPS process.
Controlled Elasticity in Nano-Structured Metallic Glass by Ion Implantation Method
Authors: Muraishi Shinji , Naito Hirono , Shi Jhi , Nakamura Yoshio , Aizawa Tatsuhiko
Published: March 2009

Different reactivity of ions has been implanted into Zr-Cu metallic glass to obtain
nano-structured surface with controlled elasticity. The penetration of glass forming element of Ni+
into crystalline Zr-Cu stabilizes glassy phase to induce crystalline-amorphous (c-a) transition during
implantation process. In the meanwhile, penetration of N+ into glassy matrix induces precipitation
of (Zr, Cu)N at the mean penetration depth of N. Critical N concentration for nitride formation is
estimated to be (Zr,Cu)-20at%N, which also suggests existing of N solid solution of glassy phase.
Inert element of Ar+ yields dispersion of nano-voids among glassy matrix. Nano-indentation tests
reveal that Young’s modulus of ion implanted glassy film dramatically changes with respect to the
induced nano-structure, to decrease 0.4 times for Ar+, to increase 1.3 times for N+ as comparison
with that for as-deposited state.
Effects of Addition of Al, Ti and Ag on Glass-Forming Ability of Cu50Zr50 Alloy
Authors: Zhang Qing Sheng , Zhang Wei , Inoue Akihisa
Published: March 2009

The thermal stability and crystalline phases precipitated from the as-cast rods of the
Cu50Zr50-based alloys with addition of Al or simultaneous addition of Al/Ti or Al/Ag elements
were investigated using DSC, DTA and XRD. The value of Tx, Trg and γ as a function of alloy
composition shows a same trend, in which the Cu46Zr46Al8 alloy exhibits the largest value of Tx,
Trg and γ. However, this trend is different from the variation of the dc with alloy composition, in
which the Cu42Zr42Al8Ag8 alloy has the largest dc for glass formation. Trg′ based on Tg/Tm has a
good correlation with the critical diameter for glass formation in this alloy system. It was found
that the alloy with higher GFA has more complex precipitated crystalline phases from the as-cast
rod with a diameter larger than the critical diameter for glass formation.
Effects of Sb and RE on the Solutionized Microstructure and Microhardness of Mg-6A1-1Zn-0.7Si Magnesium Alloy
Authors: Yang Ming Bo , Pan Fu Sheng , Ma Yan Long , Tang Li Wen
Published: March 2009

In this paper, the effects of Sb and RE on the solutionized microstructure and
microhardness of Mg-6A1-1Zn-0.7Si magnesium alloy are investigated. The research results indicate
that the solid solution treatment can result to the modification of Chinese script shaped Mg2Si phases
in the microstructure of experimental alloy, and adding small amounts of RE and Sb can strengthen
the modification efficiency. In addition, after the solid solution treatment at 420°C, the
Mg-6A1-1Zn-0.7Si alloy added 0.4%Sb and 0.25%RE exhibits higher microhardness, but the effect
of Sb and RE additions on the changing law between microhardness and solutionized time, is not
obvious.
Microstructure of Rapidly Solidified Co-Sn-Ti and Co-Sn-Si Alloys
Authors: Fujisawa Sachiko , Yoshimi Kyosuke , Kato Hidemi , Maruyama Kouichi
Published: March 2009

In this study, rapidly solidified Co-Sn-Ti and Co-Sn-Si alloys were investigated as
candidate cathodic materials for lithium-ion batteries. (Co0.5Sn0.5)1-xTix (x=0.1, 0.2, 0.3, 0.4) and
(Co0.5Sn0.5)0.9Si0.1 alloys were produced by Ar arc-melting. These alloys were further rapidly
solidified into ribbons by the single-roll melt-spinning method. Constituent phases in the ribbons
were identified by XRD, indicating that all of the alloys were composed of crystalline multi-phases
with no amorphous phase. The microstructure of the ribbons was observed by SEM and TEM, and
the chemical composition of constituent phases was analyzed by TEM-EDS. It is found from the
SEM and TEM observations that the grain size of the constituent phases ranged from tens to
hundreds nanometers due to the rapid solidification effect.
Development of the Ni-Based Metallic Glassy Alloys for PEFC Separator
Authors: Yokoyama Masanori , Yamaura Shinichi , Kimura Hisamichi , Inoue Akihisa
Published: March 2009

We prepared the Ni80-xCrxP16B4 (x = 3, 6, 9, 12, 15, 18, 21, 24, 27 and 30 at.%) alloy ingots in an
Ar flow atmosphere without evacuation and then produced the alloy ribbons by melt-spinning in
evacuation and air. Their thermal stability and other charasteristics were studied and the alloy
composition was optimized.
A supercooled liquid state appeared at Cr content of more than 9 at.%, and their Tg and Tx increased
with increasing Cr content. The 2 Tx increases up to about 45 K with increasing Cr content up to 15
at.%, and then saturates in more higher Cr content. Thus we select the Ni65Cr15P16B4
alloy as an
optimized composition for PEFC separator.
Moreover, the precise grooves were successfully formed under viscous flow process. The
groove-formed sample possessed a single glassy phase, and the Tg, Tx and 2Tx were not changed.It
indicates that the sample was not thermally affected by hot-pressing in this experimental condition.
Characterization and Modification of Nanocrystalline Iron Oxide Powders Prepared by an Inert Gas Condensation Technique
Authors: Lin Chung Kwei , Tsay Chien Yie , Yi Chen Chin , Chan Wei Hsiang , Su Cherng Yuh , Lin Hong Ming
Published: March 2009

Nanocrystalline iron oxide powders were prepared by an inert gas condensation
technique under various oxygen partial pressures. The as-prepared nanocrystalline iron oxide
powders were further modified by electroless nickel plating. The as-prepared and modified
nanocrystalline powders were characterized by X-ray diffraction, transmission electron microscopy,
and synchrotron X-ray absorption techniques. In addition, magnetic properties of the iron oxide
nanoparticles before and after electroless nickel plating were evaluated by vibrating sample
magnetometer. The experimental results show that the as-prepared nanocrystalline iron oxide
powders exhibited a mixture of iron and γ-Fe2O3 phases. TEM observations revealed that oxidation
started from the surface of the gas-condensed iron nanoparticles. The amount of iron oxide
increased with increasing oxygen partial pressure and was confirmed by synchrotron x-ray
absorption examination. A decrease in saturated magnetization and coercivity of the nanocrystalline
iron oxide powders was observed after electroless nickel plating.
The Effects of Size of Catalysts on the Morphology of Carbon Fibers
Authors: Li Fei , Zou Xiao Ping , Cheng Jin , Zhang Hong Dan , Ren Peng Fei , Zhu Guang , Wang Mao Fa
Published: March 2009

A simple method was reported for synthesis of carbon nanofibers. Ethanol burner was
employed as the setup. Different morphological carbon nanofibers were synthesized by the
decomposition of ethanol. As-grown carbon nanofibers were characterized. The results indicate that
depending on the size of catalyst, carbon deposits with different morphologies were produced.