bluuebunny/crossref_metadata_2025 huggingface dataset:
High Quality SiC Crystals Grown by the Physical Vapor Transport Method with a New Crucible Design
Authors: Ku Kap Ryeol , Kim Jung Kyu , Seo Jung Doo , Lee Ju Young , Kyun Myung Ok , Lee Won Jae , Lee Geun Hyoung , Kim Il Soo , Shin Byoung Chul
Published: March 2009

SiC single crystal ingots grown by sublimation physical vapor transport (PVT) technique
were prepared and then the SiC crystal quality with varying crucible design employing a guide tube
and tantalum foil was systematically investigated. The growth rate of 2-inch SiC crystal grown by
these crucible designs was about 0.3 mm/hr. The n-type and p-type 2”-SiC single crystals exhibiting
the polytype of 6H-SiC were successfully fabricated. The doping concentration level of below
~1017/cm3 was extracted from the absorption spectrum and Hall measurement. The densities of
micropipes and inclusions in SiC crystal boules grown using the graphite/Ta foil double layer guide
tube were significantly decreased. Finally we improved crystal quality through the introduction of
new crucible design.
Titanium Powder on Surface Conditioning of Osseointegrable Surgical Implants Topographics Aspects
Authors: Rodrigues Daniel , Tosetti João Pedro , Neto Flávio Beneduce , Salgado Lucio , Ambrozio Filho Francisco
Published: March 2009

Osseointegrable surgical implants are usually made on titanium or titanium alloys.
The osseointegration process is improved by surface conditioning of these implants,
increasing surface area with no loosing of bio-compatibility, i.e., without contamination by
non bio-compatible materials. The surface conditioning of these implants might be
accomplished in different ways: blasting, chemical etching, deposition, etc. Two alternatives
considering titanium powders are discussed in this work: blasting and plasma spraying
deposition. Results are presented in terms of topography of osseointegrable surgical implants
through scanning electron microscopy techniques.
Effect of High Energy Milling on the Magnetic Properties of the WC-10wt.%Co Cemented Carbides
Authors: Manuel J.B. , Araújo J.H. de , Costa Franciné Alves , Macedo Harim Revoredo de , Gomes Uilame Umbelino , Silva A.G.P.
Published: March 2009

Cemented tungsten carbides were produced by liquid-phase sintering. In these
work high energy milling (HEM) was used to produce homogeneous and finely grained
powder mixtures. The milling effect on the magnetic properties of sintered samples is studied.
Different mixtures in same composition (WC-10wt.%Co) were prepared by conventional
mixture technique and wet HEM up to 300 hs in Planetary Mill. Magnetic hysteresis
measurements on the sintered samples detected a significant increase in the coercitive field
and a decrease on the saturation magnetization with milling time increasing. X-ray
diffractogram show phase transformations with milling time. The Magnetic properties are
correlated with phase relations and microstructural properties of the sintered samples.
Mechanical Properties and Microstructure of Zinc Oxide Varistor Ceramics
Authors: Yoshimura H.N. , Molisani André Luiz , Narita N.E. , Manholetti J.L.A. , Cavenaghi J.M.
Published: March 2009

ZnO varistors are nonlinear resistors used as surge arresters in power transmission and distribution for the protection of electronic devices. Electrical characteristics of these materials have been extensively studied, but their mechanical behavior is not completely understood. It has been suggested that the breakdown of ZnO varistors is related to microstructure heterogeneities and processing defects. These defects are the same that usually control the mechanical strength of ceramic materials. In this work, mechanical properties (flexural strength, fracture toughness, elastic constants, and hardness) of five commercial blocks of ZnO varistors (class I) from different producers were measured and correlated to their microstructure. Pore fraction and size significantly affected the flexural strength.
Sintering Properties of ZrO2 - 3 Mol % Y2O3 Obtained from Mixture of Nano and Microcrystalline Powders
Authors: Mineiro Sergio Luiz , Nono Maria do Carmo de Andrade , Kuranaga Carlos
Published: March 2009

The polymeric precursor route based on the Pechini process was used to prepare a
mixture of nano and microcrystalline powders. The zirconia powder was stabilized with 3
mol% of yttria. Powder characteristics were evaluated by the BET technique determined the
specific area and the BJH method supplied the pore size distribution. The X-ray diffraction
results and SEM observations were carried out to characterize both the powder mixture and
the microstructures of the ceramic bodies. The sintering behavior shown in this work was
studied by dilatometric experiment, being considered the shrinkage rate and densification of
the microstructure.
Synthesis and Determination of the Kinetic Parameters for Non-Isothermal Decomposition of Complexes Ln(thd)3phen
Authors: Lopes Wilton Silva , da Silva Morais Crislene Rodrigues , Souza A.G. de
Published: March 2009

In this work the kinetics of the thermal decomposition of two ß-diketone lanthanide
complexes of the general formula Ln(thd)3phen (where Ln = Nd+3 or Tm+3, thd = 2,2,6,6-
tetramethyl-3,5-heptanodione and phen = 1,10-phenantroline) has been studied. The powders
were characterized by several techniques. Thermal decomposition of the complexes was
studied by non-isothermal thermogravimetry techniques. The kinetic model that best describes
the process of the thermal decomposition of the complexes it was determined through the
method proposed by Coats-Redfern. The average values the activation energy obtained were
136 and 114 kJ.mol-1 for the complexes Nd(thd)3phen and Tm(thd)3phen, respectively. The
kinetic models that best described the thermal decomposition reaction the both complexes
were R2. The model R2 indicating that the mechanism is controlled by phase-boundary
reaction (cylindrical symmetry) and is defined by the function g(α) = 2[1-(1-a)1/2], indicating
a mean reaction order. The values of activation energy suggests the following decreasing
order of stability: Nd(thd)3phen > Tm(thd)3phen.
Microstructural Variations in SiC Ceramics Sintered with AlN-Y2O3
Authors: Strecker Kurt , dos Santos Claudinei , Bondioli M.J. , Hoffmann Michael J.
Published: March 2009

In this work, SiC ceramics were prepared by liquid phase sintering using 10 wt.% of AlN and Y2O3 mixtures in the proportion of 4:1 and 2:3 as additives Sintering was done in a graphite resistance heated furnace at 2080oC under 0.2 MPa N2 atmosphere for 1h. Part of the samples was further heat-treated at 2000oC for 4h to allow grain growth. The microstructures of the sintered samples were analyzed using polished and plasma etched surfaces. Furthermore, relative densities, weight loss during sintering and SiC-polytype distributions are reported.
Biomimetic Coatings on Ti-Based Alloys Obtained by Powder Metallurgy for Biomedical Applications
Authors: Rigo E.C.S. , Bottino M.C. , Carraro B.D. , Taddei Elisa B. , Henriques Vinicius André Rodrigues , Silva Cosme Roberto Moreira , Bressiani Ana Helena A. , Bressiani José Carlos
Published: March 2009

Comparing to hydroxyapatite (HA), which forms a strong chemical bond with the bony tissues, metallic materials are not able to bond with bone. For this reason, a great variety of complex coating methods, such as pulse-laser deposition, ion-beam assisted deposition and plasma-spray has been used to form a HA layer onto metallic surfaces. This study evaluated the performance of the biomimetic technique on apatite-based coating formation on two Tialloys. Ti-13Nb-13Zr and Ti-35Nb-7Zr-5Ta were obtained via powder metallurgy. The Tibased alloys were biomimetically coated using a technique which was modified from the conventional ones using a sodium silicate solution as the nucleant agent. Both alloys presented similar behavior in the evaluated conditions which means the formation of a homogeneous and well defined HA coating. These results show that these new non-toxic Tialloys seem to be very promising for biomedical applications.
Thermal Analysis of Municipal Sludge Waste Combustion
Authors: Dweck Jo , Morais L.C. , Meneses J.C. , Büchler Pedro M.
Published: March 2009

Municipal sludge waste combustion was studied by thermogravimetry (TG) and differential thermal analysis (DTA), to better understand the two main stages which occur during the combustion process, and to evaluate how much of the total and significant generated heat is released is during each combustion stage. A method to measure the lower heating value (LHV) on a dried basis was developed from the TG/DTA data and it was applied to the whole process and to each combustion stage. Chemical analysis of the residual products after each step shows that nitrogen organic compounds are burnt only from 350°C to 550°C, and that the organics which are released and burnt in the previous step, which begins by 150°C, present a heating value of about 32MJ/kg. The nitrogen containing compounds present a lower LHV.
Effect of Addition of Rare Earth Oxide Concentrates on Oxidation Resistance of AISI 304L
Authors: Pillis M.F. , Araújo Edval G. de , Ramanathan Lalgudi Venkataraman
Published: March 2009

Rare earth elements are often added to chromium dioxide forming alloys to improve its high
temperature oxidation resistance. The rare earths can be also added as oxide dispersions.
Significant cost reductions are possible if rare earth oxide concentrates can be used instead of
pure rare earth oxides, the former being the precursor to obtaining pure rare earth oxide. In
this study the effect of adding pure and concentrates of rare earth oxides to AISI 304L on its
oxidation behavior has been evaluated. AISI 304L stainless steel powder compacts containing
2 vol% of pure lanthanum and yttrium oxides or their concentrate were prepared by milling
followed by pressing. The compacts were vacuum sintered and isothermally oxidized in air
for up to 200h at 900°C. The parabolic rate constants were determined and the reaction
products examined using a scanning electron microscope. X-ray diffraction analysis of the
reaction products was also carried out. The compacts with pure rare earth oxides and the
concentrates exhibited similar oxidation behavior.
A CAS Approach for the Coordination and Optimization Problem in Supply Chains
Authors: Hu Hui , Zhu Guang Yu , Shen Jin Sheng
Published: March 2009

The paper concentrates on the issue of coordination and combined optimization of supply
chains. All the member has its own interests, so there are conflicts between members motive and
overall system objective. In the paper CAS theory is used as standard paradigm and complexity of
the supply chain is analyzed. Case study includes some extreme situations of the supply chain in
different levels, namely optimization and coordination problem within operation layer, business
layer and enterprise layer. From the study, some rules are summarized to study the problem.
A Novel Edge Detector for the Pressed Characters Based on the Facet Model and the Topographic Structures
Authors: Li Xue Yong , Lu Chang Hou , Li Jian Mei
Published: March 2009

To improve the edge detecting effect of the pressed character, a novel method based on
facet model and topographic structures is proposed. Firstly, the discrete gray scale image is
approximated by a bivariate cubic function, then, the concerned features of the continuous function
are computed to describe the discrete image. After every pixel in the image has been defined to Peak,
Ridge, Saddle, Flat, Ravine, Pit or Hillside, the edge of the character is detected. To reduce the time in
computing the coefficients of cubic function, an efficient separable algorithm is presented. In addition,
an image enhancement method prior to edge detection is adopted to improve the detecting effect. The
tests show that the proposed method is more suitable for complex edge detecting problems than
common methods.
Constitutive Equation for 7050 Aluminum Alloy at High Temperatures
Authors: Fu Xiu Li , Ai Xing , Zhang Song , Wan Yi
Published: March 2009

Accurately material constitutive model is essential to understand and predict machining
process. High temperature split Hopkinson pressure bar (SHPB) test system is used to investigate
flow stress behavior and characteristics of 7050-T7451 aluminum alloy. Specimens are tested from
200°C to 550°C at intervals of 50°C and room temperature, at strain-rate of 2800s-1. The experimental
results show that flow stress is strongly dependent on temperature as well as strain rate, flow stress
decreases with the increase of temperature, while increase with the increasing of strain rate. The
material parameters are determined for both Johnson-Cook constitutive equation and modified
Johnson-Cook constitutive equation. The modified JC equation is more suitable for expressing the
dynamic behavior of 7050-T7451 aluminum alloy.
Study Morphology Transitions in Self-Assembled Triblock Copolymer Thin Films with Nanostructures by AFM
Authors: Cao Yong Zhi , Dong Shen , Liang Ying Chun , Sun Tao
Published: March 2009

As a “bottom-up” approach to nanostructures for nanofabrication, self-assembled block copolymer thin films have received much attention not only thanks to the scale of the microdomains but also due to the convenient shape tunability. In order to realize applications of self-assembled block copolymer thin films in nanotechnologies, control over microdomain spatial and orientational order is paramount. In this paper, using atomic force microscopy (AFM), we studied systemically nanostructure transitions induced by post-solvent annealing in self-assembled block copolymer thin films. Furthermore, a variety of thin films with well-ordered nanostructures, which can be employed as templates for nanotechnologies, have been realized simply and at low cost.
Experimental Study of Micro Holes Machining by USM
Authors: Jia Bao Xian , Zhao Wan Sheng , Sun Fang , Wang Zhen Long
Published: March 2009

It is necessary to drill micro holes in some hard brittle materials. Comparing with electro
discharge machining, electrochemical machining and laser machining, the ultrasonic machining
(USM) has unique advantages in hard brittle materials machining. The aim of this paper is to
present experimental work that has been done in micro holes machining by micro USM. The main
machining mechanisms of USM are discussed. It is pointed out that the contributions of each
mechanism to material removal rate are different in different cases. By using micro USM with
workpiece vibration and tool feeding in constant rate, the experiments of micro holes machining are
carried out and the process laws of tool wear are studied. Some phenomena are found and the
causation of causing these phenomena is analyzed. A Ø13μm micro hole is obtained.
Hot Press Sintering and Superplastic Forming of Fine-Grained Si3N4-Si2N2O Composites
Authors: Zhang Qing , Luo Jun Ting , Zhang Kai Feng
Published: March 2009

Si3N4- Si2N2O composites were fabricated with amorphous nano-sized silicon nitride
powders by the hot press sintering(HPS). The Si2N2O phase was generated by an in-situ reaction
2Si3N4(s)+1.5O2(g)=3Si2N2O(s)+N2(g). The content of Si2N2O phase up to 60% was accepted when
the sintering temperature was 1650°C and decreased whether the sintering temperature was increased
or not, which indicated that the reaction was reversible. The mass loss, relative density and average
grain size increased with raising of sintering temperature. The average grain size was less than 500nm
if the sintering temperature was below 1700°C. The sintered body crystaled completely at 1600°C .
The microstructure crystaled in 1600°C indicated that most of the grain size was in 150-250nm. The
aspect ratio of some grains reached 1.5. The superplastic deep-drawing forming could be undertaken
at 1550°C with a forming velocity of 0.2mm/min. The complex-shape gears could be formed by a
sinter-forging technology when the sintering temperature was 1600°C and the superplastic forging
temperature was 1550°C.
Development of a Fast Tool Servo for Ultraprecision Turning
Authors: Tian Yan Ling , Zhang Da Wei , Ruan Hong Hui
Published: March 2009

In order to implement dynamic control during ultrapre cision turning operation, a
piezo-electrically driven fast tool servo is developed. The parallel flexure hinge is utilized to guide
the moving platform and to provide preload. A high resolution capacitive sensor is used to measure
the displacement of the fast tool servo for closed loop control. With consideration of the driving
circuit, the dynamic model of the fast tool servo has been established. The effect of the driving
circuit on the dynamic response of the fast tool servo is investigated. The experimental tests have
been carried out to verify the established model and the performance of the fast tool servo.
Experimental Researches on Rapid Forming Full Compacted Metal Parts by Selective Laser Melting
Authors: Deng Qi Lin , Xie An Ning , Ge Zhi Jun , Song Jian Li
Published: March 2009

Rapid prototyping full compacted metal parts has becoming the focus of attention in the
domain of rapid prototyping. In this paper, the method of forming full compacted metal parts by
selective laser melting has been put out and the experimental researches on it have been carried out.
The surface quality and the inner microstructure of the parts formed by selective laser melting were
analyzed. The full compacted metal parts without any micro-cracks have been attained. The test
results show that the tensile strengthen of 316L stainless steel parts formed by selective laser
melting is greater than that of casting 316L stainless steel parts.
Temperature and Humidity Effects on Micro/Nano Handling
Authors: Zhou Quan , Chang Bo , Koivo Heikki N.
Published: March 2009

Micro/nano handling is an important enabling technology for future manufacturing. In the
micro scale, adhesion is a severe problem for efficient and accurate handling tasks. The cause of the
adhesion is largely from the microforces, namely van der Waals, electrostatic and capillary forces.
Those forces, however, are functions of ambient environmental conditions. This paper exams two
important ambient environment parameters in normal micro/nano handling environment: temperature
and humidity, in both theoretical analysis and experimental studies. A short guideline for
microhandling with temperature and humidity consideration is suggested based on the studies.
Convenient Method to Fabricating Complicated Microstructures on Thermoplastics
Authors: Jin Bang Kun , Yung Kai Leung , Xu Yan , Chan Ching Yuen
Published: March 2009

In this paper, a new method to fabricate various microstructures on thermoplastics by soft lithography is demonstrated. Varied line width and varied line depth microstructures that are frequently used in micro optical products, are obtained by micromolding with simple pattern stamps. This has not been reported previously. In the new method, the variations of the line widths and depths can be adjusted by changing the side shape and the curvature of the stamp. Factors, such as temperature, pressure and the degree of crystallinity on the product qualities are analyzed. Results show that besides suitable temperature and pressure, which are important for obtaining consistent microstructures; lower crystallinity can also help for better product qualities. Optical, SEM and AFM analyses show the new method can fabricate varied line width and varies line depth microstructures with desired accuracy and features. The method proposed in this work may find potential applications in producing micro products in areas such as sensors, biochips and non-linear optical devices.
The Effect of Up-Cutting and Down-Cutting Directions on Materials Swelling in Ultra-Precision Raster Milling
Authors: Kong Ming Chu , Lee Wing Bun , Cheung Chi Fai , To Suet
Published: March 2009

The influence of materials swelling across the steps on surface roughness under up-cutting
and down-cutting direction in ultra-precision raster milling was investigated. The normalized extent
of swelling is characterized by a swelling significance index, defined based on the power spectral
density of the roughness profile. Materials swelling was found to be significant in ultra-precision
raster milling, especially when copper alloys machined in the up-cutting direction. The findings in the
present study provide an important means for improving the surface finish of the raster-milled
surfaces and optimizing the cutting conditions.
Investigation on the Mechanisms of Flexible Sheet Metal Forming Using Plasma Arc
Authors: Wang Mao Lu , Yang Li Jun , Wang Yang
Published: March 2009

An investigation on the mechanism of flexible sheet metal forming using plasma arc have been performed in this paper. The experimental results show that temperature gradient mechanism (TGM) is caused by a steep temperature gradient across the sheet metal thickness, which will generates bending towards the plasma arc, while buckling mechanism (BM) usually causes sheet metals to bend away from the plasma arc on the condition that the plasma arc diameter is large compared to the sheet metal thickness and the scanning speed is low. The strain-hardening effects and phase transformation effects were also conducted in the investigation, which can be of great significance for the micro hardness and deformation of sheet metal in the heated area. The investigation reveals the mechanisms of sheet metal forming using plasma arc, and provides theoretical foundation for its industry application.
Firm Discrimination Pricing Strategies with Network Effect
Authors: Pan Xiao Jun , Chen Hong Min , Xu Li
Published: March 2009

We explore the price and welfare effect of price discrimination in a differentiated-goods oligopoly market with network effect and the effect of network effect on the equilibrium price, profit and output. We show that competitive price discrimination and network effect may intensify competition and the price discrimination increases the social welfare under oligopoly market with network effect. If firms differ in which markets they target for aggressive pricing strategy and competitive firm’s reaction is strong, prices in all markets may fall. So both firms agree on the strategies of setting the uniform pricing.
Effect of Powder Synthesis Processing on the Microstructure and Electrical Conductivity of Sintered CNTs/Fe/Al2O3 Nanocomposites
Authors: Choa Yong Ho , Yoo Seung Hwa , Yang Jae Kyo , Park Jin Woo , Oh Sung Tag , Kang Kae Myung , Kang Sung Goon
Published: March 2009

The microstructure and electrical conductivity of CNTs dispersed Al2O3 nancomposites
depending on the powder processing and CNTs content were demonstrated. The composite powders
with homogeneous dispersion of CNTs could be synthesized by a catalytic route for direct
formation of CNTs on nano-sized Fe dispersed Al2O3 powders. The sintered nanocomposite using
the composite powder with directly synthesized CNTs showed homogeneous microstructure and
enhanced elelctrical conductivity. The influence of powder processing on the properties of sintered
nanocomposites was discussed by the observed microstructural features.
Effect of Phase Transformation and Grain-Size Variation on the Dry Sliding Wear of Hot-Pressed Cobalt
Authors: Kim Yong Suk , Lee Jong Eun , Kang Suk Ha , Kim Tai Woong
Published: March 2009

Effect of phase transformation and grain-size variation of hot-pressed cobalt on its dry sliding wear was investigated. The sintered cobalt specimens were heat treated under different conditions and their tribological characteristics were examined. The sliding wear test was carried out against glass (83% SiO2) beads at 100N load using a pin-on-disk wear tester. A constant sliding speed of 0.38m/s and sliding distance of 600m were adapted. Worn surfaces, cross sections, and wear debris were examined by a scanning electron microscopy (SEM). X-ray diffraction (XRD) was utilized to identify phases of the specimen and wear debris. The cobalt specimens exhibited low friction coefficients of around 0.2. Thermal transformation of the cobalt from the hcp ε phase to the γ (fcc) phase during the wear was detected, which was deduced as a wear mechanism of the sintered cobalt. Typical wear characteristics of the cobalt including a thin detaching surface layer and fine wear debris were explained by the transformation. A correlationship between the grain size and the transformation was also explored.
New Pcbn for Heavy Interrupted Cutting of Hardened Steel
Authors: Okamura Katsumi , Kukino Saturo , Fukaya Tomohiro
Published: March 2009

PCBN tools are used worldwide for machining of hardened steel parts in automotive
industries. Because cutting by PCBN tools has many advantages, which are high-precision, highefficiency,
high-flexibility and low total machining cost, compared with conventional grinding
methods. But in heavy interrupted cutting of hardened steel, the tool life is not so stable by sudden
breakage of the cutting edge, and total cost of cutting by PCBN is not so economical compared to
the grinding. So the conventional grinding is still main process in such applications. Recently,
demand for decreasing machining cost has grown in heavy interrupted cutting and much tougher
PCBN material is required. To solve this problem, new PCBN has been developed. New PCBN has
very fine and homogeneous microstructure to increase the toughness of sintered body that it
provides a reliable tool life for heavy interrupted cutting. The features and cutting performances of
new PCBN are described in this report.
Formation of Twinned WC Grains during Carbonization of Eta Phase (W3Co3C)
Authors: Kim Jong Dae , Lee Kern Woo , Lee Joo Wan , Sharon Moshe , Kang Suk Joong L.
Published: March 2009

Twinned WC grains are sometimes observed in WC powder and sintered WC-Co alloys. The present investigation has studied the formation of twinned WC grains during carburization of an Eta phase. Eta grains were carburized at 700-1450°C for 1 min to 9 h. Twinned WC grains formed during the carburization. Crystallographic characterization of the formed twins were made using SEM and TEM. The formation of twins was found to be affected by the carbon activity during carburization. The twins formed under high carbon activities while no twins formed under low carbon activities. Two kinds of twins with different orientations were observed. The present experimental observation suggests that the twins formed via 2-dimensional nucleation and layer-bylayer growth on small WC clusters under high supersaturation and high driving force for the growth of WC grains.
Effect of Cu during Non-Isothermal Hydrogen Reduction of MoO3
Authors: Kim Gil Su , Kim Dae Gun , Oh Sung Tag , Suk Myung Jin , Kim Young Do
Published: March 2009

The effect of Cu on the hydrogen reduction of molybdenum oxide powders was investigated by measuring the humidity change during a non-isothermal process of hydrogen reduction. The presence of Cu induced a shift in the reduction temperature and strongly affected the reduction processes of MoO3→Mo4O11→MoO2, which comprised the contained chemical vapor transport of MoOx(OH)2. This study suggests that the surface of the Cu grains acts as a nucleation site for the reduction of MoOx(OH)2 to MoO2 particles from MoO3 or Mo4O11 phases. Such an activated reduction process results in the deposition of metallic Mo and MoO2 particles on the surface of the Cu grains.
Synthesis of Nano Metal Powder by Electrochemical Reduction of Iron Oxides
Authors: Seong Ki Hun , Lee Jai Sung
Published: March 2009

Synthesis of iron nanopowder by room-temperature electrochemical reduction process of α-Fe2O3 nanopowder was investigated in terms of phase evolution and microstructure. As process variables, reduction time and applied voltage were changed in the range of 1~20 h and 30~40 V, respectively. From XRD analyses, it was found that volume of Fe phase increased with increasing reduction time and applied voltage, respectively. The crystallite size of Fe phase in all powder samples was less than 30 nm, implying that particle growth was inhibited by the reaction at room temperature. Based on the distinct equilibrium shape of crystalline particle, phase composition of nanoparticles was identified by TEM observation.
NiAl Behavior at Plasma Spray Deposition
Authors: Orban Radu L. , Lucaci Mariana , Rosso Mario , Grande Marco Actis
Published: March 2009

The behavior of stoichiometric and near-stoichiometric NiAl at plasma spray deposition,
without and with a bond coat, for coating layers realization on a low alloyed steel substrate has been
investigated and is presented. In all variants, NiAl particle melting and their welding at the impact
with substrate were observed. Furthermore, a relatively compact and adherent coating layer was
formed and the NiAl was found to maintain its stability. These are all important factors for assuring
the coating layer oxidation and corrosion resistance. Good results from the coating structure and
adherence to the substrate points of view were obtained for the 45:55 Ni:Al composition, without a
bond coat but adopting an Ar protective surrounding of plasma jet. The high resistance to corrosion
of 45:55 NiAl composition was further validated through corrosion tests.
Thermoelectric Properties of n-Type 90% Bi2Te3+10%Bi2Se3 Thermoelectric Materials Produced by Melt Spinning Method and Sintering
Authors: Kim Taek Soo , Chun Byong Sun
Published: March 2009

N-type Bi2Te3-Sb2Te3 solid solutions doped with CdCl2 was prepared by melt spinning, crushing and vacuum sintering processes. Microstructure, bending strength and thermoelectric property were investigated as a function of the doping quantity from 0.03wt.% to 0.10wt.% and sintering temperature from 400oC to 500oC, and finally compared with those of conventionally fabricated alloys. The alloy showed a good structural homogeneity as well as bending strength of 3.88Kgf/mm2. The highest thermoelectric figure of merit was obtained by doping 0.03wt.% and sintering at 500oC.
Difference in Filling Property between Two Types of Binder Treated Powders Made of Atomized or Reduced Iron Powder
Authors: Uenosono Satoshi , Ozaki Yukiko
Published: March 2009

The filling property of the binder treated iron based powder made of atomized iron
powder was compared with that of the one made of reduced iron powder. The latter one showed a
better filling property than the former one, although the original reduced powder showed a worse
flow rate. Changing the particle size distribution of the original atomized powder from wide to
narrow like the original reduced iron powder, improved the filling property of the binder treated
powder. As a result, the particle size distribution of the original iron powder was found to strongly
affect the filling property of the binder treated powder.
Fabrication of Aluminum/Aluminum Nitride Composites by Reactive Mechanical Alloying
Authors: Yu Seung Hoon , Shin Kwang Seon
Published: March 2009

Various reactions and the in-situ formation of new phases can occur during the mechanical alloying process. In the present study, Al powders were strengthened by AlN, using the in-situ processing technique during mechanical alloying. Differential thermal analysis and X-ray diffraction studies were carried out in order to examine the formation behavior of AlN. It was found that the precursors of AlN were formed in the Al powders and transformed to AlN at temperatures above 600oC. The hot extrusion process was utilized to consolidate the composite powders. The composite powders were canned in an Al can and then extruded at elevated temperatures. The microstructure of the extrusions was examined by SEM and TEM. In order to investigate the mechanical properties of the extrusions, compression tests and hardness measurements were carried out. It was found that the mechanical properties and the thermal stability of the Al/AlN composites were significantly greater than those of conventional Al matrix composites.
Development of Optical Device Housing Compacted Using SUS304L Granulated Powders
Authors: Suzuki Hironori , Hara Toshihiro , Ogino Yukinobu , Sato Yasushi , Tomota Yo
Published: March 2009

In order to develop the SUS304L housing by powder metallurgy for an optical device
useful for the FTTH communication system, the optimum compacting pressure and sintering
temperature were investigated using granulated powder as the material to satisfy high air-tightness
and high laser-weldability. Then the laser-welding test of specimen made under the optimum
condition was carried out to observe welding sputters.
Fabrication of Ti(Al,O)-Al2O3 Powder Feedstock for Thermal Spraying and Evaluation of Composite Coating
Authors: Cao Peng , Gabbitas Brian , Zheng Ling , Zhang De Liang
Published: March 2009

Ti(Al,O)-Al2O3 composite powders were produced by high energy mechanical milling of a mixture of Al and TiO2 powders followed by combustion reaction. The powders were then thermally sprayed on H13 steel substrates. Microstructural examination was conducted on the composite powders and thermally sprayed coatings using X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The performance of the coatings was evaluated in terms of microhardness and thermal fatigue. The thermally sprayed coatings showed fairly good performance in the preliminary thermal fatigue tests and did not display any wetting tendency to molten aluminum.
Ti-Based Quasicrystal Layers Produced by Plasma Thermal Spraying
Authors: Takasaki Akito , Uematsu Susumu , Kelton K.F.
Published: March 2009

Ti45Zr38Ni17 powders were thermally sprayed onto mild steel substrates in air and under a reduced pressure of argon. Two kinds of powder samples were used in this study. For one type the elemental powders were gently (manually) mixed in a vial, and for the other type they were mechanically alloyed by a planetary ball mill. Several kinds of oxides were formed after thermally-spraying the mechanically-alloyed powders in air. After spraying in a reduced pressure of argon, on the other hand, the coating layers obtained from the gently mixed powders consisted of the three elemental metals (Ti, Zr, Ni), but an amorphous phase primarily appeared in the thermallysprayed mechanically-alloyed powders. This amorphous phase transformed into the icosahedral quasicrystal phase and a minor Ti2Ni-type crystal phase after annealing in vacuum at 828 K. The Vickers hardness and the contact angle with pure water for the quasicrystal layers were about 7 GPa and 92˚ respectively.
Grain Growth Rate in SnO2 Ceramics Doped with Varying Ratios of Nb2O5/CoO
Authors: Chang Dong Gyu , Lee Joon Hyung , Kim Jeong Joo
Published: March 2009

In this study, aliovalent ions of Nb2O5 and CoO were co-doped in SnO2 with different Nb2O5/CoO ratios and the grain growth rate of SnO2 was examined. The maximum grain growth rate was observed to be around Nb2O5/CoO = 0.25. Here, the results will be discussed in connection with the defect concentration and the change in diffusion rate-determining species with different Nb2O5/CoO ratios.
The Effect of MgO-Y2O3 on Al2O3-TiC Composites
Authors: Kasuriya Supawan , Atong Duangduen
Published: March 2009

The effect of the additives, Y2O3 and MgO, on the sintering and properties of Al2O3-TiC
composites was investigated. It is known that MgO is used as additive for improving densification
and Y2O3 is applied as sintering aid. In this study, the amounts of TiC were varied in the range of
30-47 wt%. The 0.5 wt% MgO and also varied amounts of Y2O3 from 0.3 to 1 wt% were added into
the composites. The sintering of Al2O3-TiC composites was performed in a graphite- heating
element furnace at different sintering temperature, 1700 and 1900°C, for 2 hr under an argon
atmosphere. The results demonstrated that the properties of the composites sintered at 1700°C were
much better than those sintered at 1900°C. The comparisons on physical properties, mechanical
properties and microstructure of composites with and without additives were reported. Comparing
with other samples, Al2O3-30wt%TiC composites with 0.5wt% MgO and 1 wt%Y2O3 exhibited the
highest density of approximately 98% of theoretical and flexural strength of 302 MPa.
Sintering Stainless Steels with Boron Addition in Nitrogen Base Atmosphere
Authors: Abenojar J. , Esteban D. , Martinez M.A. , Velasco Francisco
Published: March 2009

Stainless steel has become increasingly used in the nuclear industry recently. Thus, this
study is aimed at investigating stainless steel 316L with boron addition and the possibility of sinter
these materials in nitrogen rich atmospheres. By analyzing the final product, the properties of the
stainless steel 316L (good mechanical properties and high corrosion resistance) with the boron
neutron absorption properties were found to unify. The P/M technologies enable higher boron
quantities to be added to the steel. This was not possible with the solidification conventional
technologies, as segregation is produced in the latter.
Mixtures with 0.75 and 1.5% boron were prepared. Uniaxial compaction (at 700 MPa) was
carried out to study the green density of compacted materials. The sintering atmosphere used was
N2-10%H2-0.1%CH4, and was used to form boron nitrides instead of chromium nitrides. Although
some boron nitride was formed, not all chromium nitride formation was avoided.
The sintered samples were characterized through their physical properties (density and
dimensional change), chemical analysis (carbon and nitrogen contents), mechanical behavior
(bending strength and hardness) and wear behavior. To finish the materials characterization, a
microstructural study is proposed. Lastly, the wear tracks were observed by SEM. Boron nitride has
precipitated in grain boundaries, making more difficult the sintering of the material and reducing
the properties of the stainless steel.
Aging Characteristics of Al P/M Composites with Variation of Ceramic Contents
Authors: Min Kyung Ho , Chang Si Young , Kim Deok Soo , Kim Ji Soon , Kim Young Do
Published: March 2009

The aging behavior of sintered Al composites with various ceramic contents was investigated. 2xxx series blended powder was used as the starting powder. Ceramic contents were 0 wt.% and 5 wt.%. The blended powders were compacted at 250 MPa. The sintering process was performed at 620oC for 60 min in a N2 atmosphere. After sintering, each part was solution-treated at 518oC for 60 min and aged at 180oC. The Rockwell hardness value at the peak aging time increased with increased ceramic contents. However, the peak aging time at maximum hardness was reduced with increased ceramic contents. The changes in aging behavior may have been caused by the acceleration of diffusion due to the strain induced by differences in the thermal expansion coefficients of the matrix and the ceramic phases.
Fabrication of Al2O3/Cu Nanocomposites by Atmosphere-Controlled Sintering and Their Properties
Authors: Oh Sung Tag , Kim Young Do , Lee Jeong Keun
Published: March 2009

The microstructure and mechanical property of hot-pressed Al2O3/Cu nanocomposites with a different temperature for atmosphere changing from H2 to Ar have been studied. When the atmosphere changed from H2 to Ar gas at 1450°C, the hot-pressed composite was characterized by inhomogeneous microstructure and low fracture strength. On the contrary, when the atmosphere changed at a lower temperature of 1100°C, a more homogeneous microstructure and higher fracture strength was observed.
Reaction Synthesis and Mechanical Properties of B4C-Based Ceramic Composites
Authors: Han Jae Ho , Park Sang Whan , Kim Young Do
Published: March 2009

Boron carbide is a very hard material with high abrasive wear resistance. It requires a
very high sintering temperature of above 2200 oC to fabricate a monolithic B4C close to the
theoretical density. However, the mechanical property of monolithic B4C is not good enough to use
it directly to industrial applications. In this investigation, B4C based ceramic composites were
fabricated by in-situ reaction hot pressing using B4C, TiC and SiC powder as starting materials. The
reaction synthesized composites by hot pressing at 1950 oC was found to posses very high relative
density. The reaction synthesized B4C composites comprise B4C, TiB2, SiC and graphite by the
reaction between TiC and B4C. The newly formed TiB2 and graphite was embedded both inside
grain and at grain boundary of B4C. The mechanical properties of reaction synthesized B4C-TiB2-
SiC-graphite composites were more enhanced compared to those of monolithic B4C. The flexural
strength and fracture toughness of these in-situ B4C synthesized composites were 400-570 MPa and
6-9.5 MPam1/2, respectively.
The Effect of Microstructure on the Wear Phenomena
Authors: Kovács Tünde , Dévényi László
Published: March 2009

When investigating the wear phenomena often there is a need for studying the wear process on the basis of variable parameters (microstructure, surface roughness, and load). A new experimental method was developed thorough several set of tests, by which the effects of the mentioned parameters in the wear process can be examined. The method is based on the ball/plane contact which is suitable for examination of the local wear phenomena. There is a point like contact at the beginning of the experiments. The equipment gives the opportunity to analyse the “behaviour” of the specimens depending on the given load (normal load), on the rotations per minute, and on the surface roughness (Ra). The roughness of the counter ball does not change during the tests because of the random walk motion of the ball. A good understanding of the microstructure and its influence on wear resistance is of great importance to designers and engineers in selecting wear-resistant materials [1]. Under conditions of severe wear, the original structure with higher hardness does not exhibit a better wear resistance [2]. The experimental results demonstrate the influence of the local microstructure on the mechanism of the wear process and the dependancy of wear resistance as a function of the microstructure.
Intermediate Temperature Steam Electrolysis Using Doped Lanthanum Gallate Solid Electrolyte (2) Effects of CeO2 Interlayer on Activity
Authors: Jirathiwathanakul Nitiphong , Matsumoto Hiroshige , Ishihara Tatsumi
Published: March 2009

Steam electrolysis is attracting much interest method to produce hydrogen and
also the new energy recovery process of wasted heat energy. Up to now, Y2O3
stabilized ZrO2 (YSZ) has been used for a solid electrolyte and so the operating
temperature is limited down to 1273K. This study is focused on increasing the
performance of steam electrolysis by using LaGaO3 based oxide for electrolyte at
intermediate temperature of 873 K, which is upper limit of the obtainable wasted heat.
It was found that the formation amount of H2 is almost obeyed the Faraday law up to
1.8 V suggesting that the ionic transport number of oxide ion in LaGaO3 was kept to
be 1 under the steam electrolysis condition. The electrolyzing current is improved as
following order; La0.6Sr0.4CoO3<Sm0.5Sr0.5CoO3<< Ba0.6La0.4CoO3 for anode and
Pt<Ni<Ni-Fe for cathode, respectively. Hydrogen production rate higher than 100
μmol ml-1 min-1 at 873 K and 300 mA cm-2 were successfully demonstrated at 1.8 V in
this study. Electrolysis reaction under various reaction conditions are also presented.
The H2 formation rate increased with increasing total flow rate due to the diffusion
resistance.
Nano Composite Membranes of Sulfonated Poly (Ether Ketone)/ Poly (Ether Sulfone) Copolymer and SiO2 for Fuel Cell Application
Authors: Park Hae Suck , Suh Dong Hwan , Lee Dong Hun , Kim Whan Gi
Published: March 2009

Novel bisphenol-based wholly aromatic poly(ether ketone)/poly(ether sulfone)
copolymers containing pendant sulfonate groups were prepared by direct aromatic nucleophilic
substitution polycondensation of 4,4-difluoro-3,3’-disodiumsulfonylbenzophenone (40mol% of
bisphenol), difluorophenylsulfone and bisphenol A. Organic-inorganic composite membranes were
obtained by mixing organic polymers with hydrophilic SiO2 (ca. 20nm) obtained by sol-gel process.
The physic-chemical properties of these composite membranes were studied by thermogravimetry
analysis(TGA), differential scanning calorimetry (DSC) and transform infrared(FTIR) spectroscopy.
Scanning electron microscopy (SEM) and atomic Force microscopy (AFM) were used to observe
the surface of membrances. The proton conductivity as a function of temperature decreased as SiO2
content increased, but water uptake increased. The membranes were shown all requisite properties;
IEC (1.5meq./g), thermal stablity (Tg= 185°C), and low affinity towards methanol (1.5x10-7 -
4.3x10-7 cm2/S).
Novel Pt-Tm/Carbon Nanocomposite for the Catalyst of Direct Methanol Fuel Cell
Authors: Lee Sang Mock , Chung Jang Hoon
Published: March 2009

Pt-Tm/carbon nanocomposite has been prepared, using a heterobimetallic organometallic
complex precursor {(DMF)10Tm2[Pt(CN)4]3} as a source of metals which was obtained in the
reaction of TmCl3 with K2Pt(CN)4 in DMF at room temperature. For the electrocatalytic properties
of the Pt-Tm catalyst composed with Ketjen Black, the incipient wetness and impregnation method
were used. The XRD analysis of this noncomposited half cell materials shows nano size Pt
crystalline with no other crystalline phases. Meanwhile, the presence of Tm within cell materials
was confirmed by both EDX, and ICP analysis. ICP analysis indicates that the residual carbon
from precursor exists as amorphous phase at a given thermal treatment condition. Average Pt
particle is slightly bigger than standard Pt catalyst. Even though the particle size of active catalyst
is rather similar, the cyclic voltammetry for the oxidation reduction reaction (ORR) shows that the
coreduced electrocatalyst, Pt-Tm/carbon nanocomposite has lower catalytic activity compared with
the typical Pt/carbon catalyst prepared from H2PtCl6/C. Along with the oxidation reduction
reaction (ORR) results, the catalytic activity of methanol oxidation reaction (MOR) was also
characterized .
Observation of Effective Micro-Organisms Attached on Porous Ceramics
Authors: Seo Dong Seok , Kim Yong Gook , Hwang In Ok , Park You Bok , Lee Jong Kook
Published: March 2009

Effective micro-organisms (EM) increase the natural resistance of soil and plants, and it
considerably improves the quality and fertility of soil as well as the growth and quality of crops. In this
study, we prepared two types of porous ceramics with high and low porosity, and observed the
attaching behavior of micro-organisms to the surface of ceramics. In the case of highly porous
ceramics with large pore (80% in porosity), many of micro-organisms were observed in the pores of
interior as well as on the ceramic surfaces. However, most of micro-organisms attached on the surface
of the low porous ceramics with small pore (45% porosity), and only a few micro-organisms observed
in pore inside.
Preparation and Characterization of High-Power Anode Materials Using Soft Carbon Precursors for Lithium Ion Battery
Authors: Kim Taek Rae , Lee Ji Na , Lim Yun Soo , Kim Myung Soo
Published: March 2009

In order to apply to the high-power anode materials of lithium ion battery, various cokes
samples were prepared by milling, pitch coating, and following heat treatment. The samples were
milled and the larger particles were removed by sieving. Two types of raw cokes and four pitch
coated cokes treated at different temperatures were tested as the anode materials for lithium ion
battery, and their electrical performance was compared with the cokes without pitch coating.
Although the anode materials prepared with cokes showed lower charge-discharge capacity than the
graphite anode materials, their power capability was superior to that of graphite. The
electrochemical performance of various anodes with the pitch coated cokes was demonstrated as a
function of preparation conditions.