bluuebunny/crossref_metadata_2025 huggingface dataset:
Ohmic Contacts to P-Type Epitexial and Imlanted 4H-SiC
Authors: Crofton John , Williams John R. , Adedeji A.V. , Scofield James D. , Dhar S. , Feldman Leonard C. , Bozack M.J.
Published: March 2009

Nickel ohmic contacts to p-type epitaxial and heavily implanted 4H-SiC are
described. Room and elevated temperature results are presented. Elevated temperature
measurements of specific contact resistance are compared to theoretical calculations. The
calculations require the acceptor doping concentration and the contact’s barrier height.
Epitaxial material has a known acceptor value thereby allowing the barrier height to be
deduced by requiring agreement between the calculated and measured values of the contact
resistance. Calculations of the contact resistance for implanted material use the barrier height
from the epitaxial results along with a variable activated acceptor doping concentration which
is adjusted to give agreement with measured room temperature specific contact resistances.
Specific contact resistances as low as 7x10-6 ohm-cm2 fabricated on the Si face have been
obtained to epitaxial 4H p-type material whereas contacts to implanted material result in
much larger contact resistance values of 4x10-5 ohm-cm2. These results, when compared to
theoretical calculations, indicate that activated acceptor doping concentrations in heavily
implanted material are on the order of 2% of the implant concentration.
The Spatial Distribution of Defects and Its Dependence on Seed Polarity and Off-Orientation during Growth of 4H-SiC Single Crystals
Authors: Rost H. J. , Schmidbauer M. , Siche D.
Published: March 2009

The defect distribution in 4H-SiC single crystals in dependence on the seed polarity and
its off-orientation was investigated by KOH-etching, optical microscopy and X-ray topography.
Micropipe density, stacking fault density and dislocation density were determined for 2” crystals
grown in <000-1> direction 0 - 7° off towards <11-20> and for crystals up to 1” in diameter grown
in <11-20> or a- and <1-100> or m-directions and using repeated a-face growth. For the growth in
polar directions the micropipe density and dislocation density decrease with increasing offorientation
of the seed. A similar behavior was found for the stacking fault density and dislocation
density in non-polar directions with off-orientation to c-direction. Nevertheless, while the
dislocation density could be reduced up to three orders of magnitude for the growth along non-polar
directions, the stacking fault density was continuously increasing. Additionally, the defect
distribution after repeated a-face growth will be discussed in terms of growth related and kinetic
models.
Nanoscale Deep Level Defect Correlation with Schottky Barriers in 4H-SiC/Metal Diodes
Authors: Tumakha Sergey P. , Porter L.M. , Ewing D.J. , Wahab Qamar-ul , Ma X.Y. , Sudarshan Tangali S. , Brillson Leonard J.
Published: March 2009

We have used depth-resolved cathodoluminescence spectroscopy (DRCLS) to correlate
subsurface deep level emissions and double barrier current-voltage (I-V) characteristics across an
array of Ni/4H-SiC diodes on the same epitaxial wafer. These results demonstrate not only a
correspondence between these optical features and measured barrier heights, but they also suggest
that such states may limit the range of SB heights in general. DRCLS of near-ideal diodes show a
broad 2.45 eV emission at common to all diode areas and associated with either impurities or
inclusions. Strongly non-ideal diodes exhibit additional defect emissions at 2.2 and 2.65 eV. On the
other hand, there is no correlation between the appearance of morphological defects observed by
polarized light microscopy or X-ray topography and the presence of double barrier characteristics.
The DRCLS observations of defect level transitions that correlate with non-ideal Schottky barriers
suggest that these sub-surface defect features can be used to predict Schottky barrier behavior.
Investigation of SiO2-SiC Interface by High-Resolution Transmission Electron Microscope
Authors: Dimitrijev Sima , Han Ji Sheng , Zou Jin
Published: March 2009

High-resolution transmission electron microscopy (HR TEM) reveals an atomically flat
SiC surface after oxidation in either NO or dry O2 ambients. This reopens the question of the origin
of the electronically active defects at the SiO2–SiC interface, whose density remains orders of
magnitude higher than in the SiO2–Si interface. Capacitance-transient measurements, analysed in
this paper, demonstrate that the dominant electronically active defects are in the oxide at tunneling
distances from the SiC surface (near-interface traps). The HR TEM results cannot rule out that these
traps are related to carbon/oxygen bonds or even nanometer-sized carbon clusters, which resolves
the apparent inconsistency with the earlier experimental evidence of carbon accumulation at (or
near) the SiO2–SiC interface.
Nitrogen Implantation - An Alternative Technique to Reduce Traps at SiC/SiO2-Interfaces
Authors: Ciobanu Florin , Frank Thomas , Pensl Gerhard , Afanas'ev Valeri V. , Shamuilia Sheron , Schöner Adolf , Kimoto Tsunenobu
Published: March 2009

A near-surface Gaussian nitrogen (N) profile is implanted into the Si- or C-face of n-/ptype
4H-SiC epilayers prior to a standard oxidation process. The corresponding MOS capacitors are
investigated by conductance and internal photoemission spectroscopy. The effect of N-implantation
on the density of interface traps Dit is studied and a model is proposed, which consistently explains
the observed results.
Performance Assessment of Spray Formed AISI M2 High-Speed Steel Tools
Authors: Jesus Edilson Rosa Barbarosa , Jesus Filho E.S. , Rossi J.L.
Published: March 2009

Machining tools (interchangeable inserts) were manufactured from spray formed AISI M2 high-speed steel. The spray formed materials were mechanical and microstructural characterised. An assessment of the machining performance of the spray formed high-speed steel was attained. These results were compared to materials obtained by conventional and powder metallurgy techniques. The results showed that under the used process conditions (hot rolling and heat treating), the spray formed material showed a machining behaviour near closed to other materials; and highlight the potential of the spray forming technique for the obtention of materials with adequate properties for machining tools manufacturing.
Laser Sintering of Greens Compacts of MoSi2
Authors: de Vasconcelos G. , Maia R. Cesar , Cairo Carlos Alberto Alves , Riva R. , Rodrigues N.A.S. , Mello F.C.
Published: March 2009

In this study, the results of the feasibility of sintering green compacts of metallic
powder of MoSi2 by a CO2 laser beam as the heating source has been investigated. The main
advantage of this technique is to promote a dense material in a reduced time when compared
to the conventional sintering process. In order to sintering the MoSi2 powder, green compacts
of 6mm of diameter and 1.6mm thickness were produced in a steel die in a uniaxial press at
100MPa and after, isostatic pressed at 350MPa. The micrograph of the samples exposed to the
laser radiation performed by scanning electron microcopy (SEM) reveal the efficiency of the
sintering process and the X-ray diffraction of the powders confirmed the presence of single
phase after and before laser processing. The average microhardness of these compacts reached
near to 700 Hv0.2 in the cross section to the laser irradiation, indicating the all sintering of the
green compact.
Microstructure Characteristics of Ce-ZTA Ceramic Composites Obtained by Liquid Phase Sintering
Authors: Beck Haine , Nono Maria do Carmo de Andrade , Neto Francisco Piorino
Published: March 2009

Zirconia-toughened alumina (ZTA) ceramics with Ce-TZP (tetragonal zirconia
polycrystalline doped with ceria) volume fraction on 33% were prepared with the addition.. The
influence of glass infiltrated method was investigated. Coprecipitated Zr and Ce hydroxide mixture
was obtained from ZrOCl2.8H2O and CeCl3. 7H2O aqueous solution. CeO2-ZrO2 calcinated powder
was compacted and the compacted samples were sintered at 1180°C. Powder samples were
characterized by scanning electronic microscopy (SEM), The volume fraction of each phase, the
grains size and shapes, and the porosity were investigated with SEM. The relative density and
shrinkage was investigate too. The results showed that the crystalline matrix was composed by
SiO2 -B2O3-La2O3-Al2O3-Ce-TZP and revealed the important role played the glassy phase in the
densification of this ceramic composite.
Microstructure Study of Alumina Ceramics from Powder Mixtures of Nano and Microsized Particles
Authors: Fonseca S.T. , Nono Maria do Carmo de Andrade , Cairo Carlos Alberto Alves
Published: March 2009

In this work, was proposed to produce nanosized α-Al2O3 powder from
precipitation reactions, in order to reduce the alumina ceramics sintering temperature. For this
an addition of nanosized powder in the commercial microsized powders was done. The nano
and microsized powder particle mixtures were obtained by precipitation of nanosized
aluminum hydroxide in microsized Al2O3 in liquid suspension. Several compositions of nano
and microsized powders were carried out. These powder compositions were based on data of
simulated particle packing. The nano and microsized powder mixtures was characterized by
scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric and
differential thermal analysis (TGA and DTG). The powder mixtures were compacted by
uniaxial (75MPa) and isostatic (300MPa) pressing, producing cylindrical samples. The
powder compacted samples were sintered at 1400oC. Sintered ceramics were characterized by
XRD and SEM. The results showed that the higher density of sintered ceramic was obtained
for 65% of microsized powder and 35% of nanosized powder mixture. This composition of
size of particles of the powder was in agreement with the theoretical simulation.
Improvements in P/M Green Strength using Micronized Cellulose Particles (MCP)
Authors: Henderson A. James , Singh Ronnie
Published: March 2009

New P/M lubricant formulations implement micron-sized (“micronized”) cellulose particles
(MCP) to create MCP-enhanced lubricants. Surprising increases in green strength, up to 70% for iron
and even higher for stainless steel are obtained with standard transverse rupture bars shapes made with
0.75 wt-% additive concentrations in iron (MPIF F-0000) and 316L stainless steel powders in
comparison with the same parts made under the same conditions with industry standard lubricantbinders
of zinc stearate, ethylene-bis-stearamide (EBS), and oxidized polyolefin (OP) wax. Two
specific forms of new MCP materials are used in these tests: micronized cotton fibers (MCF), and
micronized starch particles (MSP). The findings support expectations of significantly increased
process yields for green parts and related production cost savings.
An Exploratory Study of Logistics Service Quality Model
Authors: Zheng Bing , Feng Yi Xiong , Tan Jian Rong , Che Jun Hua
Published: March 2009

While logistics services have become a significant source of competitive differentiation
between firms, significant challenges exist relative to developing logistics service offerings for the
business customers. As a service offering, logistics services are also subject to cultural influences that
exist in trade. In this article, we argue that logistics service quality (LSQ) components comprise
personnel contact quality, information quality, ordering procedures, order accuracy, order condition,
order discrepancy handling, order quality, convenience, agility and timeliness in context of China.
This paper presents a hypothesize model of LSQ as a process.
Studying on the Life Cycle Information Share and Discovery for Complicated Products Based on Data Mining and Data Grid Technology
Authors: Fang Xi Feng , Zhao Liang Cai , Su Shi Jie
Published: March 2009

Complicated product lifecycle information including design and manufacturing, operation
and maintenance as well as relative supply information, all are tightly related to the product life cycle
cooperative design and the process of establishing the dynamic alliance. Data grid includes the digital
library and data grid service technologies and it can provide the reliable technique support to
integrated information systems. The grey clustering is used to merge the same type of factors based on
presetting conditions. The improved grey clustering algorithm has been used to find the main failure
types for some equipment. The structure of the multi layers and cross information share in the
dynamic alliance for the ship life cycle information based on two data grid service centers and the
flows of resources and information discovery based on data mining are proposed according to the
information share requirements. A developed protocol system based on two data grid services has
been presented to show ship lifecycle information share and finding the main failure types of pumps
using grey clustering algorithm.
Measurement Technique of Grinding Wheel Topography Based on Binocular Stereo Vision
Authors: Zhang Xiao Feng , Xu Hong Jun , Fu Yu Can
Published: March 2009

Measurement of the grinding wheel topography and its change in machining process is
important for revealing the grinding principle of high-temperature brazed mono-layer
super-abrasive grinding wheel. A new approach of measuring grinding wheel topography based on
binocular stereovision is presented. Firstly, the binocular images are achieved while the optical axes
of the two cameras are parallel, and a corner reflection function algorithm is applied to detect
corners. Secondly, in order to get matching corners, optimal matching template is obtained by
matching curves. The experimental results show that the sequential similarity matching operation
with optimal template has advantages of high accuracy, and less error matching. Finally, the height
of the corners is obtained by calculating their parallax on left and right image, and the height error
is less than 5%.
Research on Sawing and Milling Features and NC Programming of Plastic Door and Window
Authors: Zhao Fang , Wang Wei , Ai Chang Sheng , Zhang Hui
Published: March 2009

In this paper, the structure of plastic door and window and the characteristics of sawing and milling machining PVC profile are introduced, and on the basis of analyzing the relationship between function and kerfs of the window parts, the feature model of machining window profile is constructed, hereby making the geometry modeling and defining the essential elements of design feature make the process of automatic NC code generation simplified and its reliability strengthened.
Semantic Integration of Manufacturing Data Sources
Authors: Wang Ming Wei , Zhang Shu Sheng , Zhou Jing Tao , Zhao Han
Published: March 2009

In order to gain insight into business processes, multiple autonomous data sources
residing in the manufacture enterprise need to integrate not only on storage and access methods but
also capturing the meaning of data to get a coherent and meaningful data views for different
applications requirements. This paper presents a semantic-based architecture for the integration of
heterogeneous manufacturing data sources. The integration is realized on a semantic level by the
explicit presentation of data semantics with ontology and relationships between ontologies. During
applications usage, heterogeneous data sources which represent relations of relevance are
dynamically organized in terms of their semantics. The paper discusses some major problems in the
architecture: unified schema transformation, semi-automatic ontology generation and mediation.
Monitoring Surface Roughness of Turning by Using Image Processing Technology
Authors: Lin Wei Shin , Lee Bean Yin , Chen Hung Hsin
Published: March 2009

This paper is pointed to the turning surface. A surface roughness prediction model is
constructed by polynomial network and image processing technology. After threshold treatment, we
can get the gray scale central line arithmetic mean value, Gra and the distance between black and
white color, Gf. The prediction model is constructed by Gra value, Gf value and cutting condition.
By the experimental results, it can be found that the surface roughness prediction model constructed
by this study is very accurately. It can be used to on-line surface roughness monitoring for turning.
Research on the Plunge Milling Techniques for Open Blisks
Authors: Shan Chen Wei , Zhang Ding Hua , Ren Jun Xue , Hu Chuang Guo
Published: March 2009

In order to improve the efficiency and quality in rough milling for open blisks, the plunge milling strategy is a good choice instead of the traditional 5-axis point milling and flank milling for deep and narrow channels machining. Theory and procedures of using a ruled surface to approximate a freeform surface are presented based on the theory of minimum area. The plunge milling strategy is discussed and developed for open blisks. And the NC programs of plunge milling is further developed and verified based on the UG software. At the end, the open blisk test piece was machined by plunge milling. The result reveals that high-speed plunge milling has increased efficiency greatly in the open blisks rough milling than the traditional methods.
Research on Properties of Ternary Boride Hard Alloy Materials Added Nickel and Chromium
Authors: Huang Wei Ling , Liu Fu Tian , Li Wen Hu , Huang Chuan Zhen , Li Zhao Qian , Yang Zi Run
Published: March 2009

Using Mo powder, B-Fe alloy powder and Fe powder as raw materials, adding Ni and Cr
respectively, with proper forming additives, the green body is formed by coining. The ternary
boride hard alloy material is fabricated by liquid phase sintering technology. The influence of
different content of Cr and Ni on mechanical properties is studied respectively. The optimal content
of Cr and Ni and the optimal temperature are found.
Nano Ferrofluidic Scale the String Axle of Big Length to Radius
Authors: Rui Yan Nian , Wang Ming
Published: March 2009

The scale structure and the experiment equipment are designed on the nano ferrofluidic
scale the string axle of the big length to radius, according to the principle of the nano ferrofluidic
scale. The experiment study is made on the problems of the scale performance relation associated
with this string axle, the rotational speed and the excitation current big or small. The reliability of
the nano ferrofluidic scale the string axle of the big length to radius is proved.
Study on Fixed Abrasive Lapping Technology for Ceramic Balls
Authors: Lv Bing Hai , Yuan Ju Long , Yao Ying Xue , Wang Zhi Wei
Published: March 2009

To improve low lapping efficiency of silicon nitride balls in conventional lapping
process, fixed abrasive lapping technology for ceramic balls is investigated in this paper. Diamond
abrasives and photosensitive resin are used to fabricate the fixed abrasive plate. The lapped ball
surface is observed with microscopy to identify the dominant wear mechanism. The results show
that the material removal rate of the fixed abrasive lapping is about 20 times of that of conventional
free abrasive lapping process, and the roughness is close to the conventional one. The experimental
results indicate that the fixed abrasive lapping technology is a promising process to instead of
conventional free abrasive lapping process for ceramic balls in rough and semi-finishing process.
Parameters Optimization on the Lapping Process for Advanced Ceramics by Applying Taguchi Method
Authors: Yuan Ju Long , Lv Bing Hai , Zhou Zhao Zhong , Tao Bao Chun
Published: March 2009

The surface quality is a critical factor affecting the performance and reliability of advanced
ceramics. This paper focuses on the application of Taguchi method for optimization of advanced
ceramics lapping process parameters to obtain the best finish. An optimization experiment for lapping
silicon wafer with Al2O3 was designed by Taguchi method. Surface roughness Ra and Rt are
considered as criteria for optimization. Influence of parameters involving load, speed, and slurry
concentration for a given workmaterial with given abrasive (material and size) are discussed, and the
optimum lapping conditions are figured out. Compared with single parameter experimental results, it
illustrates that the experiment design based on Taguchi method can successfully applied to determine
the optimum processing conditions for advanced ceramics lapping process.
An XML-Based Middleware for Information Integration of Enterprise Heterogeneous Systems
Authors: Li Shan , Zhang Ding Hua , Zhou Jing Tao , Ma Guang Hui , Yang Hai
Published: March 2009

Nowadays, most data in enterprise systems is still stored in relational databases, which
brings the majority of difficulties to achieve information interoperation between enterprise-level
heterogeneous systems. In this context, we propose a middleware to integrate information from
heterogeneous enterprise system based on XML standard. The proposed integration architecture aims
at providing a coherent and meaningful view of the integrated heterogeneous information systems by
leverage the back-end relational data sources. The architecture of the middleware relies on the
well-known mediator/wrapper architecture and satisfies the semantic integration features by several
main functions including data descriptions, schema transformations and integrations based on the
XML-Schema standard.
Study on Pre-Stress Cutting of Bearing Race and Its Machined Surface State
Authors: Ye Bang Yan , Wu Bo , Liu Jian Ping , Liu Xiao Chu , Zhao Xue Zhi
Published: March 2009

Theoretical analysis and experiments on bearing race show that a suitable residual
compressive stress on roll path of bearing race can prolong its contact fatigue life. However, residual
tensile stress is often found on workpiece surface of bearing race. To actively control the residual
stress state and improve fatigue life of bearing part, a new method of pre-stress hard cutting is applied.
In this paper, the principle of pre-stress hard cutting for bearing race is introduced as well as the
experiments on it. In the experiments, residual stress, hardness and roughness of machined surface are
measured and analyzed. Moreover, micro-topography and texture characteristics of machined surface
are investigated and experimental results are compared with that by grinding. It is found that we can
get residual compressive stress and fine quality on machined surface of bearing race by pre-stress hard
cutting and increase its productivity as well.
High-Quality NC-Data Generation in Mold and Die Manufacturing
Authors: Kim Dong Won , Heo Eun Young , Kim Bo Hyun , Yang Il Hwan
Published: March 2009

The CAM operation which generates a process plan and NC-data for mold machining
plays an important role in mold manufacturing because it quite affects down stream processes such as
NC machining, polishing, and assembly operation. This study proposes a supporting system which
facilitates non-experts to perform the CAM operation easily and to select the high-quality NC-data
which can increase machining productivity. It also designs and implements the support system in
accordance with a CAM operation scenario. To check the usability of the support system developed,
this study applies it to some practical examples of molding dies.
A Research on Manufacture Technology of Superhard Material Precision Reamers Based on Inside-Holding Technique
Authors: Chen Ming , Huang Wei , Wang Chun Hai
Published: March 2009

In modern industry time, more strict requirement on dimension precision, geometry
shape and surface roughness of holes have been set to meet the continue advent of superhard
materials, the interchanges requirement under batch production, and the application of precision and
super-precision machining technique. The super hard material precision reamers have great
advantages in dealing with these problems. This paper presents a new process in designing and
manufacturing of the superhard material precision reamers, which is called inside-holding
electroplating technique. The new process adopts inside-holding electroplating process, eddy
flowage electroplating device, extracting pattern process and etc.. Comparing with traditional
process, the new one has such advantages as low production cost, high precision, long service life,
undressed, and so on.
The Research on the Orientation Error of Three-Axis Turntable in Theory and Measuring Method Based on Assembling
Authors: Li Yan , Fan Da Peng
Published: March 2009

Based on the analysis of geometric errors of mechanism assembling, this paper applies
the multi-body system kinematics theory in building the orientation error model of three-axis
turntable induced by assembling errors. The results using the model could be easily applied in
controlling turntable by error’s compensation, and shows which assembling error item has the larger
effect. Furthermore，referenced by the measuring means of three-axis turntable, this paper conceives
the definitions of the volumetric and orientation accuracy aimed at the turntable system, enlightened
from the conception of NC machine tool. This research may be helpful to the foundation of the
systematic conception of the turntable accuracy no matter in theory or in measuring method.
A Virtual Cutting Based Method for Aero Engine Turbine Blade Reverse Modeling from Its Cone Beam CT Images
Authors: Cheng Yun Yong , Pu Kun , Liu Yuan Peng , Zhao Xin Bo
Published: March 2009

Turbine blade is one of the critical parts of the aero engine and usually has complex
structures. The main purpose of this paper is to present a virtual cutting based method for aero
engine turbine blade reverse modeling from its cone beam computed tomography (CBCT) images.
Based on the turbine blade CBCT images, an improved Marching Cube algorithm was used to
construct a 3D mesh model of the turbine blade. Then, cutting tools of parallel planes, concentric
cylinders, concentric cones or revolved free form surfaces were used to cut the turbine blade mesh
model to get the profile curves. After the profile curves were constructed by curve fitting and
joining, the lofting geometric modeling technique was used to generate the turbine blade airfoil
surface working in parallel flow, cylindrical flow, conical flow and revolved free form flow
respectively. A set of computer simulating turbine blade CBCT images (512×512×512) was used to
test the presented method and the testing results showed that the method was feasible and
convenient.
Nozzles from Alumina Ceramics with Submicron Structure Fabricated by Radial Pulsed Compaction
Authors: Kaygorodov A. , Rhee Chang Kyu , Kim Wheung Whoe , Ivanov Victor , Paranin S. , Spirin A. , Khrustov Vladimir
Published: March 2009

By means of magnetic pulsed compaction and sintering of weakly aggregated alumina
based nanopowders the jet forming nozzle samples for hydroabrasive cutting were fabricated. The
ceramics were obtained from pure alumina, as well as from alumina, doped by TiO2, MgO and
AlMg. The ceramic properties of the channel surface and the nozzle volume were investigated. It
was shown that the samples sintered from AlMg doped Al2O3 powder had the best desired
mechanical properties and structural characteristics: relative density ~0.97, channel microhardness –
18-20 GPa, channel surface roughness ~0.7 /m, average crystallite size ~1 /m.
Synthesis and Mechanical Properties of Nano Laminating Cr2AlC using CrCx/Al Powder Mixtures
Authors: Han Jae Ho , Park Sang Whan , Kim Young Do
Published: March 2009

Cr2AlC, one of the ternary carbide families, was synthesized by a reactive hot pressing of
CrCx (x=0.5) and Al powder mixture used as starting materials at the temperature range of 1200
oC~1400 oC under 25 MPa in Ar atmosphere. Fully dense Cr2AlC with high purity was synthesized
by hot pressing CrCx and Al powder mixture at the temperature as low as 1200 oC. After
synthesizing the bulk Cr2AlC, it was found that it has a typical layered structure as found in other
ternary carbides such as Ti3AlC2 and Ti3SiC2. The average grain size of synthesized bulk Cr2AlC
was varied in the range of 10-100 ㎛ depending on hot pressing temperatures. The Vickers hardness
of bulk Cr2AlC was less than 4 GPa under the loading of 10N and this decreased with increasing
indentation load. The maximum flexural strength of synthesized bulk Cr2AlC exceeded 600 MPa.
Also, it was found that synthesized Cr2AlC was readily machinable by a conventional WC tool bit
due to its low hardness as well as damage tolerance properties upon fracture.
The Effect of Oxygen Addition on Oxidation Resistance and Cutting Performance of Si3N4 Ceramics
Authors: Nagano Mituyoshi , Sano Hideaki , Sakaguchi Shigeya , Zheng Guo Bin , Uchiyama Yasuo
Published: March 2009

The effect of oxygen addition on oxidation behavior of the β-Si3N4 ceramics with 5 mass% Y2O3 and 2 or 4 mass% Al2O3 was investigated by performing oxidation tests in air at 1300° to 1400°C and cutting performance tests. These tests were intended to clarify their ware resistance as cutting tools. The results of mass change, SEM observation and composition analysis of the specimens before and after oxidation test showed that as the Al2O3 content in the β-Si3N4 ceramics increased, mass changes resulted higher oxidation during which process pores and cracks formed due to the release of N2 gas. The values of hardness and bending strength of the specimens with relatively small amount of 2 mass% Al2O3, which formed solid solution in the Si3N4 structure [Si6-zAlzOzN8-z (z = 0.1)], showed larger than those of the specimen with 4 mass% Al2O3 (z = 0.2). The specimens group added with Al2O3 of 2 mass% (Z = 0.1) also showed high wear resistance. From this, we could conclude that the mechanical properties of β-Si3N4 ceramics depending on oxygen introduction is much effective on cutting performance improvements of the cutting performance of β-Si3N4 ceramics.
Development of Tungsten Heavy Alloy with Hybrid Structure for Kinetic Energy Penetrator
Authors: Baek Woon Hyung , Kim Eun Pyo , Song Heung Sub , Hong Moon Hee , Lee Seong , Kim Young Moo , Lee Sung Ho , Noh Joon Woong , Ryu Joo Ha
Published: March 2009

A new tungsten heavy alloy with hybrid structure was manufactured for the kinetic
energy penetrator. The tungsten heavy alloy is composed of two parts: core region is molybdenum
added heavy alloy to promote the self-sharpening; outer part encompassing the core is conventional
heavy alloy to sustain severe load in a muzzle during firing. The fracture surfaces of the specimen is
observed after ballistic tests. The core region revealed brittle behavior with W/W inter-granular
fracture which activates self-sharpening. On the other hand, outer part exhibited conventional
ductile fracture mode. From ballistic test, it was found that the penetration performance of the
hybrid structure tungsten heavy alloy is higher than that of conventional heavy alloy. This heavy
alloy is thought to be very useful for the penetrator in the near future.
Synthesis and Properties of Multimetal Oxide Nanopowders via Nano-Explosive Technique
Authors: Vasylkiv Oleg , Sakka Yoshio , Skorokhod Valeriy
Published: March 2009

We demonstrate the methodology of engineering the multi-component ceramic nanopowder with
precise morphology by ‘nano-blast’ calcinations decomposition of preliminary engineered nanoreactors.
Multiple explosions of just melted C3H6N6O6 embedded into preliminary engineered nanoreactors break
apart the agglomerates due to the highly energetic impacts of the blast waves. Also, the solid-solubility of
one component into the other is enhanced by the extremely high local temperature generated during each
nano-explosion in surrounding area. This methodology was applied for production of agglomerate-free nanoaggregates
of Gd20Ce80O1.95 with an average size of 42 nm and LaSrGaMgO3-x nanopowder with an
average aggregate size of 83 nm.
The Effects of Molybdenum Content on the Dynamic Properties of Tungsten-Based Heavy Alloys
Authors: Lee Woei Shyan , Chan Tien Yin
Published: March 2009

The effects of the content of molybdenum on the dynamic properties of tungsten heavy
alloys were investigated.Increase in mechanical properties was observed in molybdenum-added
tungsten heavy alloys, due to the refined microstructure. On the other hand, decrease in mechanical
properties was also observed in the alloys with high molybdenum concentrations, due to the decreased
strength of the matrix phase and the precipitation of an intermetallic phase. Hopkinson bar
dynamic test under strain rates ranging from 2000 s-1 to 8000 s-1 at room temperature revealed that
the flow stress of tungsten heavy alloys depended strongly on the strain, strain rate, and the content
of molybdenum. The variation of flow stresses was caused by the competition between work hardening
and heat softening in the materials at different strain rates. The high temperature strength of
the matrix phase was increased by the addition of molybdenum, which enhanced the strength of the
tungsten heavy alloys in high strain rate test.
Magnetic Properties Obtained for Fe-50Co Alloy Produced by MIM with Elemental Powders
Authors: Silva Aline , Wendhausen Paulo A.P. , Machado Ricardo , Ristow Waldyr
Published: March 2009

In order to obtain specific magnetic properties, it is of paramount importance to increase the alloy density of components fabricated by powder metallurgy. An alternative to increase the density of alloys such as Fe-49Co-2V would be the use of elemental Fe and Co instead of the prealloyed powder. Trying to give some insight on the industrial application of this strategy, this paper investigates the replacement of more conventional pre-alloyed Fe-49Co-2V powders with elemental Fe and Co. A previous analysis shows that it is possible to achieve higher densities using elemental Fe and Co powders sintered at the same temperature than Fe-49Co-2V. It is also shown that this leads to a noticeable improvement in some important magnetic properties such as permeability and magnetic induction.
Properties of Soft Magnetic Composite with Evaporated MgO Insulation Coating for Low Iron Loss
Authors: Uozumi Gakuji , Watanabe Muneaki , Nakayama Ryoji , Igarashi Kazunori , Morimoto Koichiro
Published: March 2009

MgO insulation coating with thickness of ca. 50nm was evaporated on the surface of
iron powder and fabricated soft magnetic composite(SMC) with low iron loss. The MgO insulation
coating had greater heat resistance than conventional phosphate insulation coating, which enabled
stress relieving annealing at higher temperature (600C). Electrical and magnetic properties of SMC
was examined. The electrical resistivity of the SMC annealed at 700C was 21μΩm. The iron loss at
50Hz for Bm = 1.5T was 5.34W, which was 40% of conventional SMC and was at the same level
with laminated steel plate (t0.35). These results show that MgO insulation coating has enough heat
resistance and adhesiveness to powder surface to obtain SMC with low iron loss.
Sm2Fe17 Prepared by Calciothermic Reduction-Diffusion Using Different Iron Powders
Authors: Boareto J.C. , Soyama Juliano , Felisberto M.D.V. , Hesse R. , Pinto A.V.A. , Taylor T.R. , Wendhausen Paulo A.P.
Published: March 2009

This paper compares the effect of using different types of iron powders for the preparation of Sm2Fe17 by calciothermic reduction-diffusion (CRD). Three types of iron powder were used: carbonyl, sponge and water atomized. The results show that, when immediately nitrogenated after the CRD process, Sm2Fe17 prepared from sponge and water atomized iron powders yield Sm2Fe17N3-magnets with a high degree of texture. However, after a suitable treatment with hydrogen followed by nitrogenation, Sm2Fe17-powders made from Carbonyl iron produce magnets with the best quality regarding coercivity, remanence and degree of texture.
Cold and Detonation Spraying of TiB2-Cu Nanocomposites
Authors: Lomovsky O.I. , Dudina Dina V. , Ulianitsky V. Yu , Zlobin S.B. , Kosarev V.F. , Klinkov S.V. , Korchagin M.A. , Kwon Dae Hwan , Kim Ji Soon , Kwon Young Soon
Published: March 2009

TiB2-43vol.%Cu nanocomposite powders with titanium diboride particle size 50-100 nm were cold and detonation sprayed in order to fabricate coatings on a copper substrate. The powders were produced by self-propagating high-temperature synthesis (SHS) followed by mechanical milling. The temperatures during spraying were calculated and the change in the nanostructure of the powders during spraying was studied: in cold sprayed coatings the size of TiB2 particles was well retained, in detonation sprayed coatings the growth of the particles was observed, the mode of spraying greatly affecting the microstructure and the size of the particles. The hardness of cold sprayed coatings was higher compared to detonation sprayed coatings. This research shows the future potential for development of coatings with submicron and nanostructure by cold and detonation spraying of powders produced by mechanical milling.
Sintering of Mechanically Alloyed YSZ Nanocrystalline Powders
Authors: López de la Torre Marco Antonio , Durá Oscar Juan , Hernández M. , García Cordobés M. , Herranz Gemma , Sánchez Bautista Carlos , Rodríguez Gloria P.
Published: March 2009

We report on the mechanical and structural properties of nanocrystalline 8% and 10% mol yttria stabilized zirconia (YSZ) obtained using mechanical alloying (MA). For milling times above 32 hours the complete alloying of the starting Y2O3 and ZrO2 powders is achieved. The asmilled powders show a body-centered cubic crystalline structure with grain sizes in the order of 10 nm. After uniaxial pressing and sintering the compacts exhibit densities of more than 93% of the theoretical value. The microhardness of the compacts increases with sintering temperature, reaching a maximum value of 913 HV0.5 after sintering at 1220º C for 6 hours. The correlation of these enhanced mechanical properties with the microstructural changes induced by heat treatment of the nanocrystalline MA powders is discussed.
Amorphous Diamond for Generating Cold Cathode Fluorescence Light
Authors: Sung James C. , Kan Ming Chi , Hu Shao Chung
Published: March 2009

Amorphous diamond can emit electrons in vacuum when applied with an electrical field
of only a few volts per micron. It is also extremely thermionic so the emitted current can increase
millions times when heated to only a few hundreds degrees centigrade. As a result, amorphous
diamond can be a thermal generator or a solar cell. The energy conversion efficiency can have much
higher (e.g. 50%) than that (e.g. 15%) of silicon based solar cells that can absorb only a narrow
spectrum of sun light. As a solar cell, amorphous diamond has another advantage that its radiation
hardness is the highest of all materials, hence, its thermal electricity efficiency will not attenuate as
does the solar cell based on photo electric semiconductorls.
An immediate application of amorphous diamond is to coat it on electron emitting electrodes,
such as that used as cold cathode fluorescence lamps (CCFL) that illuminate liquid crystal displays
(LCD) for fornote books and television sets. Amorphous diamond can dramatically reduce the
turn-on voltage to lit CCFL so the lamp life can be greatly extended. Moreover, the electrical
current can be increased to enhance the brightness of the light.
Electrophoretic Deposition of Ni Nano-Particles for Self-Repairing of Heat Exchanger Tubes
Authors: Lee Gyoung Ja , Pyun Su Il , Rhee Chang Kyu
Published: March 2009

The electrophoretic deposition process of Ni nano-particles in organic suspension was employed for self-repairing of heat exchanger tubes. For this purpose, Ni nano-particles prepared by levitation-gas condensation were dispersed into the solution of ethanol with the addition of dispersant. The pitted Ni alloy specimen was prepared by applying a potential of 0.9 V (vs. Ag/AgCl) in aqueous 0.1 M NaCl solution. For electrophoretic deposition of Ni nano-particles on the specimen, a constant electric field of 100 V cm-1 was applied to the specimen for 180 s in Nidispersed solution. It was found that as the electrophoretic deposition time increased, the size of the pit remarkably decreased due to the agglomeration of Ni nano-particles at the pit with a higher current value rather than the outer surfaces of the specimen with a lower current value. Moreover, the current density increased with electrophoretic deposition time and reached a constant value. From the above, it is concluded that as the electrophoretic deposition proceeds, the pit becomes smaller in size, and hence the nano-particles more extensively aggregate at the pit by lyosphere distortion.
Photocatalytic Performance of Barium-Doped Strontium Tantalate
Authors: Kozu Asuka , Fujimori Hirotaka , Kim Ki Young , Oshiro Kazunori , Yamamoto Setsuo , Sakata Yoshihisa , Imamura Hayao
Published: March 2009

Sr2Ta2O7, a layered perovskite compound, has been reported to possess most excellent photocatalytic properties among the layered perovskite materials. Recently, we have successfully demonstrated that Ba5Ta4O15 that was prepared under Ta rich atmosphere has high photocatalytic performance as well as Sr2Ta2O7. In this study, several amount of Ba was doped into Sr2Ta2O7, and the photocatalyst samples with a mol ratio of Sr: Ba: Ta = (1-x): x: 1 were prepared by the polymerized complex method to investigate the effect of Ba substitution for the Sr site on photocatalytic activity. The maximum photocatalytic performance was obtained for x = 0.2 near the solid solubility limit, which is three times as high as that of undoped Sr2Ta2O7 and is in the highest level in a series of tantalum photocatalysts reported so far. The increase of photocatalytic activity would be caused by crystal distortion due to doping of Ba ion.
Thermoelectric Properties of Fe-Doped CoSb3 Prepared by Encapsulated Induction Melting and Hot Pressing
Authors: Park Kwan Ho , Lee Jung Il , Ur Soon Chul , Kim Il Ho
Published: March 2009

The encapsulated induction melting and hot pressing were employed to prepare the Fedoped CoSb3 skutterudites and their thermoelectric properties were investigated. Single phase δ- CoSb3 was successfully obtained by the subsequent heat treatment at 773K for 24 hours. Iron atoms acted as electron acceptors by substituting cobalt atoms. Thermoelectric properties were remarkably improved by the appropriate doping. Co0.7Fe0.3Sb3 was found as an optimum composition for best thermoelectric properties in this work.
Ni3Al-Fe-Cr Alloy Processed by Combined Mechanical Alloying - Reactive Synthesis
Authors: Orban Radu L. , Lucaci Mariana
Published: March 2009

Property modification of Ni3Al with alloying addition of Fe and Cr was investigated
through MA and subsequent SHS processes. Fe addition brought about high temperature
strengthening effect and formed a Ni-Fe compound in the liquid grainboudary phase of Ni3Al
structure and Cr addition showed a retarded homogenization. Homogenized Ni3Al composition with
Fe and Cr addition by MA and SHS showed better mechanical resistace and deformability in the
compression tests at temperatures up to 800°C than the same composition processed by classical
PM routes.
Preparation, Structure, and Properties of Ni3Al and NiAl Light Powder Alloys for Aerospace
Authors: Povarova K.B. , Skachkov O.A.
Published: March 2009

New light super-heat-resistant powder Ni3Al and NiAl-based alloys (of the Ni-Al-Mo-B,
Ni-Al-Fe-La, and Ni-Al-Y2O3 systems), as well as a new technology for preparing and processing
them have been developed. The density of the alloys was 7.3-7.5 and ~6 g/cm 3, respectively. The
Ni3Al sheets were used to prepare shields for combustion chambers in gas-turbine engines by roomtemperature
deformation; the shields are intended for the long-term operation at 1100-1200°C and
for the short-term use at 1300°C. The activated NiAl powders alloyed with Fe+La were used to
produce sintered complex-shape articles, such as combustion stabilizers in a jet unit of combustion
chamber of the gas-turbine installation, heat sources, etc. capable of operating at t≤1500°C under
low mechanical stresses. At 1100, 1300, and 1500°C, the 100-h strength of the heat-resistant NiAl-
(2-7.5) vol. % Y2O3 alloys subjected to directional recrystallization is 70, 35 and ≥10 MPa,
respectively. The vanes, in which the length of recrystallized grain is smaller than the vane length
by a factor of 1.5-2, were manufactured from these alloys.
Effect of Fe Doping on Thermoelectric Properties of Mechanically Alloyed CoSb3
Authors: Ur Soon Chul , Kwon Joon Chul , Kim Il Ho
Published: March 2009

Fe doped skutterudite CoSb3 with a nominal composition of FexCo1-xSb12 (0≤x≤2.5) have been synthesized by mechanical alloying (MA) of elemental powders, followed by vacuum hot pressing. Phase transformations during mechanical alloying and vacuum hot pressing were systematically investigated using XRD. Single phase skutterudite was successfully produced by vacuum hot pressing using as-milled powders without subsequent annealing. However, second phase in the form of marcasite structure FeSb2 was found to exist in case of x≥2, suggesting the solubility limit of Fe with Co in this system. Thermoelectric properties as functions of temperature and Fe contents were evaluated for the hot pressed specimens. Fe doping up to x=1.5 with Co in FexCo4-xSb12 appeared to increase thermoelectric figure of merit (ZT) and the maximum ZT was found to be 0.78 at 525K in this study.
Mechanical Milling of Lithium with Metal Oxide and its Reactivity with Gases
Authors: Yokoi Tomomichi , Yamasue Eiji , Okumura Hideyuki , Ishihara Keiichi N.
Published: March 2009

Lithium is one of the active metals and reacts with nitrogen even at room temperature.
In this study, in order to grind and activate Li, the mechanical milling of Li with stable metal oxide,
namely, Al2O3 and MgO, using a high energy vibrating ball mill was performed. In the case of Li-
MgO system, it reacts with N2, but hardly reacts with O2. The reaction with N2 generally produces
Li3N, while for some vigorous reactions the Mg3N2 and Li2O are produced as the major phases. In
the case of Li-Al2O3 system, however, reactivities with both N2 and O2 are high. The difference will
be explained in terms of the reaction mechanism and the Li state.
The Magnetic and Photo-Catalytic Properties of Fe Doped TiO2 Nanocrystalline Powder Synthesized by Mechanical Alloying
Authors: Uhm Young Rang , Woo S.H. , Lee Min Ku , Rhee Chang Kyu
Published: March 2009

Fe-doped TiO2 nanocrystalline powders were prepared by mechanical alloying (MA) by
varying Fe contents up to 8.0 wt.%. The TEM analyses were carried out to clarify morphologies and
position of Fe within the mechanically alloyed powders. The Fe-doped powder consisted of
spherical particles, and the average grain size was less than 10 nm. For the Fe-doped TiO2, the color
of the powders changed from white to bright yellow with increasing concentration of Fe. The UVvis
absorption showed that the UV absorption for the Fe-doped powder shifted to a longer
wavelength (red shift) and the photo-efficiency was enhanced. The absorption threshold depends on
the concentration of nano-sized Fe dopant. Mössbauer spectrum for 4 wt.% Fe showed the
ferromagnetic phase (sextet) and paramagnetic phase (doublet). However, the only paramagnetic
phase (doublet) was seen for 8 wt.% Fe. As the Fe concentration increased up to 4 wt.%, the UV-vis
absorption and the magnetization were increased. The beneficial effect of Fe doping for
photocatalysis and ferromagnetism was observed at the critical dopant concentration of 4 wt.%.
Based on the UV absorption and magnetization, the dopant level was localized to the valence band
of TiO2.