bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetoresistance of La2/3(CaxBa1-x)1/3MnO3/NiO Composite Materials
Authors: Chen Shui Yuan , Huang Zhi Gao , Lai Heng , Gai Rongquan , Zhang Feng Ming , Du You Wei
Published: March 2009

Ferromagnetic (FM) La2/3(Ca0.6Ba0.4)1/3MnO3 and antiferromagnetic (AFM) NiO nanoparticles were synthesized using sol-gel method, respectively. La2/3(Ca0.6Ba0.4)1/3MnO3 (1 mol)/ x NiO (x= 0, 0.05 and 0.15mol) composites with the coated NiO were prepared. The experimental results indicate that, both phases of LCBMO and NiO coexist clearly in the composites and the sizes of the NiO nanoparticles in the intergranular region between the LCBMO particles are very small; the interface of NiO influences evidently the value of MR and it is found that the tunneling MR for x=0.05 is the largest in three samples. The magnetoresistance behavior has been explained by two-level model of tunneling magnetoresistance and percolation model well.
Solidification of Aluminum Infiltrated Composites
Authors: Yu J.K. , Yan Q. , Fang Pin Yang
Published: March 2009

The solidification and defects of Al/SiC and Al/C composites were investigated by
directional solidification techniques. The solidification and defects of Al/SiC composites are greatly influenced by temperature gradients, solidification rates, the size of SiC particles and the chemical composition of magnesium, but slightly by the volume fraction of SiC particles and the chemical composition of silicon. The solidification shrinkage feeding of Al/C composites is greatly improved by hybridizing carbon fiber bundles with 3 vol% of SiC particles. A model of the solidification
feeding was proposed and the solidification feeding distance was derived according to the preform geometry.
Rolling and Annealing Textures of SiCw/Al Composite
Authors: Zhang W.L. , Gu M.Y. , Wang De Zun
Published: March 2009

A squeeze casting 15vol.%SiCw/Al and pure aluminum were cold rolled to 50 pct
reduction in thickness and then annealed at 500°C for 1h. The textures of the treated materials were examined using XRD. The dominant texture components in the cold rolled composites consisted of {112}<111>、{100}<011> and {123}<634> and were much weaker than those in the cold rolled aluminum. The new texture components in annealed composites were {211}<213>、{013}<131>
and {011}<211> and had the similar intensity as those remained from the deformation state. This indicated that the recovery reaction and recrystallization occurred simultaneously when the cold rolled composite was annealed at 500°C. Also, the annealing texture was much weaker in the composite than that in the aluminum. The weaker deformation and annealing textures in the composites can be attributed to the introduction of the whiskers.
Fabrication of the Aluminum Matrix Composite by Ultrasonic Infiltration Technique
Authors: Sasaki Gen , Adachi Junichi , Choi Yong Bum , Pan Jin , Fujii Toshio , Matsugi Kazuhiro , Yanagisawa Osamu
Published: March 2009

In order to infiltrate the molten aluminum alloy to the reinforcement preform by low
pressure in casting process and acquire the high performance composites with high density, the effect of the ultrasonic vibration on the infiltration was investigated by model experiments using clear solution and glass or aluminum borate preform, which is correspond to a molten matrix and reinforcement, respectively. Ultrasonic vibration improves the wettability of liquid polyester resin on glass plate, dramatically. The final infiltration height and infiltration speed of liquid polyester resin in glass capillary were improved by the ultrasonic vibration. Furthermore, the infiltration speed of water to aluminum borate preform accelerated by ultrasonic vibration. This effect was more remarkable, when the infiltration height is lower or infiltration time is shorter. In actual, the molten aluminum alloy infiltrate to SiC preform using ultrasonic vibration easily and acquire the high dense composites without pores.
Fracture Behavior of Brittle Coating Layer on Metal Substrate
Authors: Ochiai Shojiro , Tomida T. , Nakamura Toyomitsu , Iwamoto S. , Okuda Hiroshi , Tanaka Masashi , Hojo M.
Published: March 2009

The compressive fracture and spalling of multiply-cracked brittle coating layer on metal substrate under tensile stress was studied for the anodic-oxidized aluminum wire with the Al2O3 coating layer and galvannealed IF steel plate with the intermetallic compound coating layer consisting of ζ, δ1 and Γ1 and Γ phases. The thin Al2O3 coating layer on Al wire was fractured by buckling in the circumferential direction by the compressive hoop stress, but thick layer was debonded by the tensile radial stress at interface. The thickness of the coating layer at the transition
from the compressive fracture to interfacial debonding was around 30 µm. In the galvannealed steel plate sample, the (ζ+δ1) phases were fractured by buckling in the width direction, resulting spalling of the (ζ+δ1) phases in the first stage, and the remained (δ1+Γ1+ Γ) phases or (Γ1+Γ) phase was again fractured by buckling, followed by the spalling of the remained phase.
Microstructures and Properties of a Bainite and Martensite Dual-Phase Cast Steel Fabricated by Combination of Alloying and Controlled Cooling Heat Treatment
Authors: Jiang Ye Hua , Zhou Rong Feng , Lu Dehong , Li Zhen Hua
Published: March 2009

A bainite/martensite dual-phase cast steel was fabricated by a process of combination of alloying with Si and Mn elements and controlled cooling heat-treatment. Its microstructure was consisted of fine lower bainite with carbide particles precipitated homogeneously, martensite and a little residual austenite. Because of the good match of hardness and impact toughness, its impact wear performance was a little better than that of the isothermal quenching steel, and much better than that of high manganese steel such as Mn13.
Process Conditions and Interfacial Characteristics of Al/Cu Clad Composite Formed by Hot Hydrostatic Extrusion
Authors: Yoon Duk Jae , Jeong Ha Guk , Lim S.-J. , Na Kyoung Hoan , Kim E.Z.
Published: March 2009

The relations between interfacial properties of clad composite and process conditions are studied. Adherence on interface of two materials is most significant property of clad composite. Properties of composite material are manifestation of its microstructure, and process conditions are decisive factor to the microstructure in interfacial area. In-depth understanding about the composite’s properties is only achieved through appreciation of the mechanism by which the process conditions
affect the microstructure. Aluminum and copper clad composite bars are extruded at the various process conditions. Interfacial adherence of the extruded composite is examined. Microstructure of the dispersed layer and its vicinity is investigated.
Synthesis of In-Situ Titanium Carbide Particle Reinforced Titanium Composites
Authors: Kim Myoung Gyun , Sung Si Young , Kim Young Jig
Published: March 2009

Titanium carbide particle reinforced titanium composites were prepared by in-situ
synthesis reaction between titanium and carbon liquid alloys. The phases constitute and microstructures of titanium composite have been investigated by OM, XRD, SEM and EPMA. Although it was possible to synthesize titanium carbide particle reinforced titanium composites, the morphology of in-situ titanium carbide grows into typically dendritic shape due to the compositional supercooling theory. Using computerized image analysis, the average particle size and aspect ratio of in-situ formed titanium carbide is about 28.1 ㎛ and 1.9, respectively.
On Carbide Particle Reinforced Al Composites Fabricated by Pressureless Infiltration Technique
Authors: Lee Kon Bae , Sim Ho Sup , Yang Hyung Ryul , Kwon Hoon
Published: March 2009

5052 Al matrix composites reinforced with carbide particles (SiC, TiC, and B4C) were fabricated by the pressureless infiltration and the tensile properties were analyzed. The strength values in the control Al were significantly increased over those of the commercial alloy while the strain to failure of the former decreased. Strength values in the composite reinforced with carbide particles were further increased compared to the control alloys. It was observed that strengthening effect by an addition of reinforcement varied with according to reinforcement types. By relative comparison, both TiC and B4C particles may be effective reinforcement compared to SiC particles in Al matrix composites.
On Thermomechanical Processing of High Ductility SiCp/Zn 22wt.%Al Metal Matrix Composites
Authors: Zhu P. , Yeung Wing Yiu , Heness Greg , Duggan B.J.
Published: March 2009

SiCp/Zn-22 wt% Al metal matrix composites of different particulate sizes have been
prepared and tensile tested at 250°C at various strain rates. Scheduled thermomechanical treatment of structural refinement was employed to enhance the ductility of the composites. Substantial ductility of over 500% elongation bas been achieved within the strain rates investigated. The highest elongations are generally obtained by the samples reinforced with large particulates. Microstructural examination of the tested samples shows significant material cavitation and particulate separation in the material after tensile deformation. It was found that the particles had a de-strengthening effect.
Stabilization of Nano-Al2O3p/Cu Composite after High Temperature Annealing Treatment
Authors: Song Ke Xing , Liu Ping , Tian Bao Hong , Dong Qi Ming , Xing Jian Dong
Published: March 2009

Al2O3 dispersion strengthened copper composite (Al2O3p/Cu composite) was produced by internal oxidation. The hardness and electrical conductivity of the produced Al2O3p/Cu composite (0.60 wt.% Al2O3) subjected to high temperature annealing treatments after different cold work deformations have been investigated; the microstructures of the composite have also been analyzed by TEM. Results show that the microstructure of the composite is characterized by an uniform distribution of nano-Al2O3 particles in Cu-matrix; the composite can maintain more than 91% hardness retention after 1h, 1000°C annealing treatment; the recrystallization of the Cu-matrix can be largely retarded and only partially happened even annealing for 1h at 1050°C, following cold deformation of 84%.
Photoacoustic Spectroscopy Applied to the Study of Bone Consolidation in Fractures
Authors: Lomeí Mejia P.A. , Urriolagoitía G. , Jiménez Pérez J.L. , Hernández-Gómez Luis Héctor , Lecona Butron H. , Cruz Orea A.
Published: March 2009

By using photoacoustic (PA) spectroscopy it was performed a study about bone
consolidation in fractures. It was obtained the optical absorption spectra of callus of male rat fractured bones at different consolidation times. From these spectra it was possible to observe the presence of alkaline phosphatase through their absorption peaks which were compared with characteristic peaks reported in the literature for this phosphatase. In this study we showed that alkaline phosphatase could be considered as an indicator of the repair process of bone fractures.
Martensitic α↔γ Phase Transition and Ionic Conductivity in "Pure" and Doped LiIO3 Single Crystals
Authors: Trnovcová Viera , Hanic František , Šrámková Tatjana , Škubla Andrej
Published: March 2009

The polymorphism and anisotropy of electrical, dielectric, and thermophysical properties of “pure” and doped LiIO3 single crystals are studied. The hexagonal a-LiIO3 phase is a 1-D ionic conductor (along the c axis). The anisotropy of the ionic conductivity of the a-phase can be reduced by doping with transitive metals (Fe, Mo, Ni). The martensitic character of the a«g transition is proved. In the γ-phase, only a slight anisotropy of the conductivity is found. The a«g transition is not an ionic-superionic one.
Electron Wind Induced Mass Transport in Sub-Micrometer Size Wires
Authors: Zehe A. , Ramírez A. , Patiño A.
Published: March 2009

Nanoscale metallic wires play a pivotal role in future microelectronics. Extremely high current densities, present in silicon-based integrated circuits, cause wire destruction by electron-wind induced atomic migration and void formation. In the present paper we elaborate a theoretical model, which describes the interaction of impurity-vacancy pairs. Criteria are given for an optimum material selection, based on the atomic valence of matrix and alloying metal, which reduce (or enhance) the probability of void formation.
Holographic Gratings with Different Spatial Frequencies Recorded on BB-640 Bleached Silver Halide Emulsions Using Reversal Bleaches
Authors: Álvarez M.L. , Camacho N. , Neipp C. , Márquez A. , Beléndez A. , Pascual I.
Published: March 2009

The research made in the field of recording materials for holographic applications has yielded to materials of improving quality. Photographic emulsions have played an important role in this investigation, since although this is the first material used for recording purposes, there are a series of characteristics that convert the photographic emulsion in a very interesting material for holographic recording. In this work we will present the optimisation of a reversal bleaching process. This process has been largely used for Agfa 8E75 HD emulsions, but there is still a significant lack of information about it when used with BB-640 emulsions. There are some differences between BB-640 and Agfa 8E75 HD emulsions such as the degree of hardening of the gelatin, the mean grain size or the emulsion thickness. These differences must be taken into account in order to use the same chemical procedures commonly used for Agfa plates with BB-640 ones. For instance, one of these differences, the mean size of the silver halide grains present in the emulsion, influences directly in the scattering of the final hologram recorded in the emulsion. It will be demonstrated that the use of ultra-fine grained emulsions, such as BB-640, allows obtaining holograms with high diffraction efficiencies and low absorption and scattering. In particular, in this work a reversal bleach procedure will be optimised for diffraction gratings recorded with different spatial frequencies on BB-640 emulsions.
Electrical Property of Calcium-Zirconium-Indium Oxide by Irradiation
Authors: Tsuchiya Bun , Nagata S. , Saito Kesami , Toh Kentaro , Shikama Tadaaki
Published: March 2009

Radiation induced changes in electrical properties of calcium-zirconium-indium oxide ceramics (CaZr0.9In0.1O3-d) were investigated using a fission reactor of Japan Materials Testing Reactor (JMTR). Electrical conductivity of CaZr0.9In0.1O3-d under the reactor irradiation increased by the Radiation Induced Conductivity (RIC), Radiation Induced Electromotive Force (RIEMIF)and Radiation Induced Electrical Degradation (RIED), caused by the electronic excitation. The RIC and the RIEMF decreased gradually for the constant value of the reactor power with the increase of irradiation time. Moreover, it was confirmed by Post-irradiation Examination (PIE) experiments that the initial electrical and thermal properties were completely degraded by the irradiation. These radiation effects are attributed to point defects or their clusters produced by atomic displacements caused by neutron collisions and also by the radiolysis.
Measurements of Zeta Potential of Poly(Tetrafluoroethylene) Foils
Authors: Šoster Robert , Stana-Kleinschek Karin , Brumen Milan , Ribitsch Volker
Published: March 2009

Zeta potential (ZP) of poly-tetrafluoroethylen (PTFE) and polyamide 6 (PA 6) foils was measured using the streaming potential method. All measurements were carried out in a flat cell where PTFE foils are usually used in electrokinetic measurements as a part of the measuring device, to form the channel and to achieve a proper distance between the foils surface of measured samples.
The primary interest of the present work was to investigate the influence of pretreatment of PTFE foils on their electrokinetic properties in order to find out to what extent such pretreatment may affect measuring results of other samples and to develop a procedure of PTFE foils preparation with purpose to achieve the same initial conditions for all measurements.
Electrochemical Characteristics of Silicon-Doped Tin Oxide Thin Films for Application of Lithium Secondary Micro-Battery Anode
Authors: Park Chul Ho , Son Young Gook , Ko Tae-Ho
Published: March 2009

The SnO2 thin films doped with traces of silicon were deposited on the p-type (100) Si substrate by the r.f. magnetron sputtering method from Sn0.94Si0.06O2 target for the application of lithium secondary micro-battery anode. The crystal orientation of tin oxide thin films was changed from (110) to (101) or (211) with the increase of the substrate temperature. Contrarily, the
crystallization of tin oxide thin films, which were heat-treated in the RTA furnace from 450°C to 650 °C under the O2 ambient, did not show significant difference. As a result of the electrochemical analysis, we could see that the irreversible capacity was reduced during the first discharge/charge cycle. Capacity increased with the increase of substrate temperature, but decreased with the increase of RTA temperatures. In particular, the maximum value of reversible capacity was 700mAh/g under the deposition condition of the substrate temperature of 300°C and the Ar:O2 ratio of 7:3.
Changes in Mechanical Properties of the Wide-Gap Region Brazed with Various Brazing Temperatures and Times
Authors: Kim Yong Hwan , Kwun S.I.
Published: March 2009

The microstructural changes and the relations between mechanical properties and additive powder with various brazing temperatures and times were investigated. The IN738 and BNi-3 alloy powders were used as an additive and filler metal powders for the brazing process. The wide-gap brazing process was carried out in a vacuum of 2×10-5 torr. The wide-gap region brazed with 60wt.%
IN738 additive powder had a microstructure consisting of IN738 additive, and binary eutectic of Ni3B-Ni, and (Cr, W)B. As the brazing temperature and time were increased, the size of IN738 additive powder increased to 181µm, which decreased the amount of low strength Ni3B-Ni eutectic structure, thereby increasing the fracture strength of the wide-gap brazed region. Cracks in the brazed
region were observed to propagate through the Ni3B-Ni structure, which lowered the fracture strength of the wide-gap brazed region.
Surface Characteristics of Ni-Diamond Composite Powders by Electroless Plating Method
Authors: Ahn Jong Gwan , Kim Dong Jin , Hai Hoang Tri , Lee Jae Ryeong , Chung Hun Saeng , Kim Chong Oh
Published: March 2009

Ni-diamond composite powders with nickel layer of round-top type on the
surface of synthetic diamond (140/170 mesh) were coated with semi-batch reactor by an electroless plating method (EN). The effect of nickel concentration and feeding rate of reductant, temperature, reaction time, and stirring speed on the weight percentage of deposited Ni and morphology, mean particle size, and specific surface area of the composite powders were investigated by AAS, FE-SEM, PSA and BET. The weight percentage of Ni in the composite powder increased with time and temperature but decreased with stirring speed, and the weight percentage was 55% at 150 min., 200 rpm and 70oC.
Fluxless Brazing of Al6061 Alloys Using Ag-28Cu Insert
Authors: Lee Young Sup , Lee C.H. , Lim Cheol Ho , Cho Dong Choul , Shin Seung Y.
Published: March 2009

A diffusion brazing of aluminium alloy A6061 was preformed using a Ag-28Cu insert to conduct eutectic brazing. Interface behaviors of the brazed joints were observed after brazing at 450-560°C. The tensile property of the brazed joints was also examined. During diffusion brazing of Al6061 alloys with Ag-28Cu insert, eutectic melts were formed by eutectic reaction between Al6061 and Ag-28Cu insert. It was found that the reaction layers composed of two phases were formed at the
interface between Al6061 and Ag-28Cu insert. EPMA analysis revealed that two phases in the reaction layers consist of Ag-rich phase and Cu-rich phase. The tensile strength of the joints brazed at 560°C for 30min was 160 MPa.
Stress Concentration Regions in Ceramic Ball Heads for Total Hip Replacement Considering Trauma-Like Loading
Authors: Aum Ho Sung , Curiel M.C. , Carillo Daniel G.
Published: March 2009

A high stress condition in the hip system may cause fracture of the ball head. This failure may appear after a heavy accident such as sudden fall. The aim of this investigation is to make a computer simulated model of the hip system to evaluate the regions of stress concentration as well as the pressure in the stem-ball junction. 3D Non-Linear Finite Element Analyses were performed taking into consideration a high peak load to simulate trauma conditions. Ball heads from 22 to 36 mm in diameter were modeled, and also two sizes for taper lock were simulated to report their influence on the stresses over the critical areas of the ball head. Two different materials of common ball head ceramics (Alumina and Zirconia) were considered to evaluate its relation to the stresses produced. It was found that the ball head cone’s depth has major incidence in the stress concentration surrounding the stem when an impact load is applied, and that a deeper cone may offer a more relieved loading configuration when considering stress related parameters such as Von Mises stress, contact pressure and friction stress.
Plasma-Sprayed Wollastonite Coatings for Biomedical Application
Authors: Xue Wei Chang , Liu Xuan Yong , Zheng Xue Bin , Ding Chuan Xian
Published: March 2009

A new bioceramic coating based on wollastonite was prepared by plasma spraying. The coatings exhibited good mechanical properties. The bond strength of the coating on substrate was about 40 MPa, which is higher than that of HA coatings used in orthopedics and dentistry. The bioactivity of wollastonite coatings was evaluated in vitro and in vivo. After immersed in simulated body fluid, a bone-like apatite layer was formed on the surface of wollastonite coatings. Osteoblast
could survive and proliferate on the surface of coatings. After implanted in dog’s cortical bone, histological observation demonstrated that bone tissue could extend and grow along the surface of wollastonite coatings. The coating bonded directly to bone without any fibrous tissue, indicating good biocompatibility and bone conductivity. The wollastonite coatings also showed good bone
inductivity property, inducing new-bone formation on their surface after implanted in marrow. The results obtained indicated that the plasma-sprayed wollastonite coatings possessed good mechanical properties and excellent bioactivity in vitro and in vivo. It appears that a wollastonite coating may be suitable for the repair and replacement of living bone, especially for load-bearing situations.
Contact Fracture Behaviors of Ti3SiC2 Synthesized by Hot Pressing Using TiCx and Si Powder Mixture
Authors: Hwang Sung Sic , Park Sang Whan , Cho Seong Jai , Lee Dong Bok
Published: March 2009

The contact fracture behaviors of fine-grained Ti3SiC2 and coarse-grained high purity Ti3SiC2 are examined by the Hertzian indentation and Vickers indentation technique. The Vickers hardness of bulk Ti3SiC2 is as low as 5.3~6.3 Gpa, and the Hertzian contact stress-strain curves for Ti3SiC2 deviate much from linearity, which resembles the fracture behavior of a ductile metal rather than a brittle ceramic. The contact damages by both Vickers indentation and Hertzian indentation reveal a fairly good plastic deformation nature of Ti3SiC2. Un-reacted TiCx in fine-grained Ti3SiC2
may impede the plastic deformation by slip along basal plan inside Ti3SiC2 grain, making Ti3SiC2 less plastic under loading.
Morphology and Microstructure of Graphitic Nanofibers Synthesized by the CVD Method Using Nickel-Copper as a Catalyst
Authors: Cho Kwon Koo , Lee Bong Ki , Ahn Jae Pyong
Published: March 2009

This paper describes the morphology and microstructure of graphitic nanofibers(GNFs) synthesized by the catalytic decomposition of ethylene in the presence of Ni:Cu(70wt%:30wt%) as catalyst at 550°C to 700°C. The catalyst was prepared by the coprecipitation method using aqueous solution of metal nitrates. The catalysts and the graphitic nanofibers(GNFs) were characterized by
FE-SEM, HR-TEM and EDXS. The shape, composition and microstructure of the catalyst according to the synthesis temperature of graphitic nanofibers(GNFs)were changed so that it brought about the change of morphology and microstructure of graphitic nanofibers(GNFs). In particular, it should be noted that the composition change of catalysts with different synthesis temperature is one of the key factors in determining the morphology of graphitic nanofibers(GNFs)
Fabrication of Calcium Based Fine Ceramic Materials by Recycling Eggshell
Authors: Lee Sang Jin , Chun S.Y.
Published: March 2009

A raw eggshell shows CaCO3 phase, and pure CaO can be obtained by calcination of the raw eggshell. And the morphology of the calcined eggshell is grape-type granular with uniform particles. By using the recycled eggshell, biocompatible and highly sinterable calcium phosphate bio-ceramics were successfully fabricated, such as hydroxyapatite (HAp) and b-tricalcium phosphate
(b-TCP), and wollastonite (CaSiO3). The observed phases and microstructures on the powder synthesis process are dependent on the content of eggshell and calcination temperature. In this study, the crystalline development and the microstructure of synthesized powders and the densified specimens are examined by X-ray diffractometry and scanning electron microscopy.
Decomposition of Dioxins in Gas and Water Using Photocatalytic Silica-Gel
Authors: Taoda Hiroshi
Published: March 2009

Dioxins are extremely toxic, and it is difficult to treat them with the conventional method. When irradiated by light, photocatalysts generate strong oxidative potential and decomposes almost all organic substances containing dioxins to water, carbon dioxide and others. Silica-gel has high adsorptive activity as well as large surface area, and it is transparent to ultraviolet light. Photocatalytic silica-gel was prepared by a dip coating method using TiO2 sol obtained by hydrolyzing titanium
tetraisopropoxide on silica-gel bead (about 3mm in diameter) and heat-treated at 550°C. Since the surface area of the photocatalytic silica-gel is 300m2/g, the reaction area is large and allows the highly efficient decomposition of harmful organic substances, unpleasant odors and colored matters contained in waste water. The photocatalytic apparatus for decomposition of dioxins in emission gas
from waste incinerators is composed of the catalyst layer consisting of 95dm3
photocatalytic silica-gel and 16 units of UV lamp. The photocatalytic apparatus was connected to the bypass line led from the outlet duct of cyclone, and the concentration of dioxins in the exhaust gas was measured. Decomposition test of dioxins in scrubber water was also performed using a photocatalytic apparatus
with 150g photocatalytic silica-gel and 8 units of UV lamp. After 0.5dm3 of scrubber water containing dioxins was circulated in the photocatalytic apparatus for 1, 2 and 24 hour, each concentration of dioxins in the water was measured. As a result, the removal efficiency over 99% of dioxins in emission gas and scrubber water from waste incinerators has been obtained.
Preparation and Properties of Carbon Nanofiber/Polyimide Composite Films
Authors: Yamamoto Aya , Sano Hideaki , Zheng Guo Bin , Uchiyama Yasuo
Published: March 2009

Carbon nanofiber/polyimide (CNF/PI) composite films were prepared by dispersing CNFs in polyamic acid, the precursor of polyimide, followed by imidization. Because the as-synthesized CNFs were difficult to disperse, they were treated with ball-milling in water and surfactant solution for 12 or 24 hours. MgO microparticles were also added to enhance the ball-milling effect. As-prepared composite films were approximately 0.05 mm in thickness. The volume fractions of
CNFs in composites were 0.1%, 0.2%, 0.5%, 1%, 2%, and 5%, respectively. The effect of treatment of CNFs on the tensile strength and electric resistivity of CNF/PI films were investigated.
Removal of Cu++ Ions from Aqueous Cu-EDTA Solution Using ZnO Nanopowder
Authors: Lee Ju Hyeon , Kim Byoung Sung , Lee Jae Chun , Park Sung
Published: March 2009

Nanometer size zinc oxide (ZnO) powder was prepared by a novel “solution-combustion method (SCM)”, and it was used as a semiconductor photocatalyst to evaluate its photoreduction properties. Aqueous solution of heavy metal ions (Cu-EDTA) was used for the photocatalysis reaction under UV illumination. The result was then compared with other semiconductor photocatalyst powders such as titanium dioxide (TiO2) powder (P25; Degussa) and TiO2 powder
prepared by a homogeneous precipitation process at low temperature (HPPLT). The zinc oxide nanopowder showed the highest removal rate of the Cu++ ions from the solution among the photocatalyst powders compared. The superior photoreduction ability of the ZnO nanopowder appears to be due to its excellent UV absorption capacity.
Reactive Sputter Deposition of WCx Films for Replacing Hexavalent Chromium
Authors: Park Yeon Kyu , Kang Seung Mo , Kim Daekyu , Lee Chong Mu
Published: March 2009

This paper investigates the reactive sputter deposition of tungsten carbide (WCx) films for replacing hexavalent chromium which was found to cause cancer in human body. The deposition rate of the films was proportional to rf-power and inversely proportional to the CH4 content in the sputtering gas. The hardness of the WCx coatings increased as the rf-power increased. The highest hardness was obtained at the CH4 concentration of 10 vol.% in the sputtering gas. The hardness of the WCx film deposited under optimal conditions was far higher than that of the electroplated chromium film although the corrosion-resistance of the former was slightly inferior to that of the latter. Considering all these experimental results, it may be concluded that the reactive sputterdeposition of WCx coatings can be effectively applied to the parts with complex geometries as an alternative to chromium electroplating.
Synthesis of Heterogeneous β-SiC Nano-Particles and Nano-Whisker from TEOS/SiO2 Bead/PMMA Ternary Xerogel
Authors: Kim Jae Won , Lee Seoung Soo , Hur Sung Kang , Jung Yeon-Gil , Jo Chang Yong
Published: March 2009

A modified sol-gel method is proposed for the preparation of silicon carbide nano-particles and nano-whisker. Tetraethoxysilane (TEOS), SiO2 bead, and PMMA as precursor of carbon source were used for preparing a ternary carbonaceous silicon xerogel, and morpholine is employed in the sol-gel process as a catalyst reagent. SiC nano-particles and nano-whisker were obtained from
carbothermal reduction and vapor-solid (VS) reaction of the ternary xerogel at 1300°C for 9h in a dynamic argon atmosphere (flow rate; 600 cm3/min), and then purified by removing excess silica, residual carbon, and other impurities. The purified SiC sample was characterized by TG/DTA, XRD, SEM, and HRTEM. The nano-particles and the nano-whisker were synthesized by different growth
mechanisms, with an initial nucleation via a VS reaction between SiO vapor and carbon precursor (PMMA) and a partially subsequent growth via a vapor-vapor (VV) reaction between SiO and CO, respectively.
Influence of Heat-Treatment on the Mechanical Properties of Lotus-Type Porous Carbon Steel Fabricated by Continuous Zone Melting Method
Authors: Kujime Toshihiko , Hyun Soong Keun , Nakajima Hideo
Published: March 2009

Lotus-type porous carbon steel with cylindrical pores was fabricated by a continuous zone melting method under pressurized mixture gases of hydrogen and helium. The microstructure of lotus-type porous steel was analyzed, and the tensile test was carried out. In the case of tensile test of the specimen with the cylindrical pores parallel to the solidification direction, the ultimate tensile strength was lower than the estimated value, but the yield strength was higher than the estimated
value. It was assumed that the strength was decreased in proportion to decreasing cross section area of the specimen. The increasing of yield strength was attributed to precipitation strengthening. The influence of heat treatment (Quenching and tempering, normalizing) on the tensile properties was investigated.
Synthesis of Calcium Carbonate from Calcium Chlorine Solution Using Homogeneous Precipitation Method
Authors: Kim Kyung Nam , Shin Dae Yong , Son Se Gu , Kim Yong Do
Published: March 2009

Calcium carbonate(CaCO3) was synthesized from aqueous CaCl2 solution, using the homogeneous precipitation technique, which uses the hydrolysis of urea. The effects of reaction conditions on the morphology of CaCO3 were examined at 50-90°C. Particle size of CaCO3 decreases, as the concentrations of urea and [Ca2+] are increased. Calcite is produced more, as the concentration of [Ca2+] is increased. Method to stir the reaction solution affects significantly the
particle size and morphology of CaCO3. Uniform needle-like aragonite particles were obtained, when left at 90°C for 4hours without stirring.
Thermoelectric Properties of Co1-xNbxSb3 Prepared by Induction Melting
Authors: Park J.B. , You S.-W. , Cho K.W. , Lee J.I. , Ur Soon Chul , Kim Il Ho
Published: March 2009

Induction melting was attempted to prepare the undoped and Nb-doped CoSb3
compounds, and their thermoelectric properties were investigated. Single phase d-CoSb3 was successfully obtained by induction melting and subsequent annealing at 400°C for 2 hours in vacuum. The positive signs of Seebeck coefficients for all the specimens revealed that Nb atoms acted as p-type dopants by substituting Co atoms. Electrical conductivity decreased and then increased with increasing temperature, indicating mixed behaviors of metallic and semiconducting
conductions. Electrical conductivity increased by Nb doping, and it was saturated at high temperature. Maximum value of the thermoelectric power factor was shifted to higher temperature with the increasing amount of Nb doping, mainly originated from the Seebeck coefficient variation.
Characteristics of Polymer Composite Electrolyte for MEMS Power System
Authors: Kim Jung Nam , Park Jong Wan
Published: March 2009

In the polymer electrolyte, lots of salt have been studied and synthesized in many laboratories. In the previous our work[1,2], we found that the SiO2 (-7 nm, Degussa-Huls), which had the OH- and (CH3)3 surface groups, could help to enhance the ionic conductivity and the interfacial stability. We used as a plasticizer. It has the four CN groups at the end of chains. It was helpful to enhance the ionic
conductivity, as respected. The ionic conductivity of the composite electrolytes was about 5.0ⅹ10-5 S/cm at room temperature. In addition, we conducted the charge/discharge test with LiMn2O4 at room temperature and 45 °C. The retention of 1st cycle to 100th cycle was 74 % at 45°C.
Self-Discharge Behavior of Lithium/Sulfur Battery Using Aluminum Current Collector
Authors: Ryu Ho Suk , Ahn Hyo Jun
Published: March 2009

We investigated the self discharge behavior of lithium/sulfur cell using an alumium current collector. The discharge capacity decreased by 14% for oriniginal one after 30 days’ storage at room temperature. The open circuit voltage(OCV) of Li/S battery gradually decreased from 2.45V to 2.38V during the 30 days. The self discharge behavior was related to the decrease of elemental sulfur in the
sulfur electrode.
Effect of H2 on Microstructure and Property of Nano-Titania Coatings
Authors: Zhao Xiao Bing , Liu Xuan Yong , Ding Chuan Xian
Published: March 2009

Nanostructured titania coatings were prepared by atmospheric plasma spraying using commercial nano-powder. The effects of plasma forming gas H2 on microstructure and anatase content of coatings were examined by X-ray diffraction and field emission scanning electron microscopy. Photocatalytic properties of coatings were evaluated through a photo degradation of methylene blue in water solution under ultraviolet illumination. The results obtained indicated that the TiO2 coating was a mixture of anatase and rutile. The anatase content of coatings increased with increase in the flow rate of plasma forming gas H2. The content of anatase was as high as 60% in the as-sprayed coatings under optimal spray parameters. The photocatalystic property was improved by the content of anatase in coatings. It was found that all fabricated TiO2 coatings exhibited photocatalytic activity for the methylene blue test regardless of spraying parameters.
The Paths and Strategies for Increased Magnesium Applications in Vehicles
Authors: Schumann S.
Published: March 2009

The use of magnesium in motor vehicles today and in future depends on numerous
technical and economical factors, though the cost factor is essential. How might use of magnesium in vehicles develop, what prerequisites are necessary, what R&D efforts are required These questions will be addressed as follows based on component and project examples. The main focus of the current magnesium applications can be seen in the drive train and in the interior. In the short term, these applications will be further expanded: doubling the amount is feasible. This will be supported by the currently developed Mg alloys with extended application potential (creep resistance). Mg components in the body, Mg-sheets and Mg-extrusions applications will appear initially in niche-market and premium vehicles. This can prepare the way for and eventually lead to greater use of Mg in volume-production models as part of a multi-material design concept. The essential prerequisites for such increased use of magnesium will be discussed.
Effects of Zr on Microstructures and Properties of a β Matrix Mg-13Li-3Al-0.7Zr Alloy
Authors: Chen Bin , Feng Lin Ping , Zhou Tie Tao , Liu Pei Ying , Li Huan Xi
Published: March 2009

The effects of Al, Zr additions on the microstructure and properties of a β matrix
Mg-Li-Al-Zr alloy of hot forged, cold rolled and heat- treated states have been systematically investigated. The tensile properties of the alloy was tested, and microstructure was studied by X-ray diffraction and SEM methods. The results showed that the addition of zirconium in the aluminum containing Mg-Li alloy was effective for grain refinement. The alloy containing zirconium of rolled state exhibited higher strength and satisfied ductility compared with the alloy without zirconium. The existence of zirconium in the alloy was mainly in the form of Al-Zr compounds of Al2Zr
andAl3Zr. The reason for less age-hardening effect may be caused by the capture of aluminum by zirconium and as a consequent by the lake of aluminum in the matrix.
A Rheological Model of Semisolid Magnesium Alloy Slurries
Authors: Li L. , Zhou X.W. , Chen J.Y.
Published: March 2009

In this paper a rheological model is presented which describes the rheological behaviors of liquid-like semisolid magnesium alloy under a simple shearing flow. On the basis of Chen and Fan’s mono-dispersion microstructure model of semisolid metal slurry, the particle size distribution is considered in this model. It is believed that it is the state of agglomeration which determines the rheological behaviors of the slurry, whereas the external flow conditions such as shear rate and shearing time, affect the rheological properties by changing the state of agglomeration. The
expressions of collision rate between two agglomerates, effective solid fraction and the formula of apparent viscosity of Chen and Fan’s model are corrected according to the experimental results and statistical mechanics. Finally calculated apparent viscosity and the average number of the particles of AZ91D by the developed model as functions of shear rate are presented. These results show that
there is a one to one coupling between the rheological properties of the magnesium alloy slurries and the state of the agglomeration.
Investigation on Low-Frequency Electromagnetic DC Casting of AZ91 Magnesium Alloy
Authors: Le Q. , Cui J. , Guo Shi Jie , Zhao Z. , Yu F.
Published: March 2009

Direct chill (DC) casting is a dominant way of producing aluminum and copper alloy billets. In the past we developed a new technique, namely Low Frequency Electromagnetic Casting (LFEC), in which low-frequency electromagnetic field (LFEF) is incorporated to DC casting processing. In this work, LFEF was introduced to the magnesium DC casting processing. Experimental investigations and numerical simulation indicate that application of LFEF to DC casting magnesium alloy can significantly improve the surface quality of the AZ91 billets, refine microstructure and reduce both macro and micro segregations. It was also found that high casting velocity become possible for magnesium alloys through LFEC processing.
Research and Development of Wrought Magnesium Alloys in China
Authors: Pan Fu Sheng , Yang Ming Bo , Zhang Ding Fei , Wang Ling Yun , Ding Pei Dao
Published: March 2009

Recent research and development status of wrought magnesium alloys in China is
reviewed, and more attentions are paid to structure controlling, plastic processing, welding, surface treatment and product application. The control of alloy phases, grain refinement, deforming behavior and twin-roll strip casting process are discussed. The existing problems on the research and development of wrought magnesium alloys in China are analyzed.
Yield and Plastic Deformation of Mg-Alloy AZ31 at Elevated Temperatures
Authors: Qan Gaofeng
Published: March 2009

The yield and plastic deformation behaviour of wrought Mg-alloy AZ31 sheets were
investigated at elevated temperatures from ambient to 300°C. It is found that the 0.2% proof stress and ultimate strength decrease linearly with increasing temperature, and the Young’s modulus goes down in the same way. Whereas the ductility, expressed by elongation, increases with temperature, in contrast to the decrease in uniform elongation. The plastic deformation anisotropy, represented
by the ratio of transverse and thickness strain of the plate sample, decreases as the temperature increases, and at about 225°C, coincidentally, reaches to unity. The activation volumes for yield stress and ultimate strength are discussed with a thermal activation law-Arrhenius Equation.
An OIM Analysis on the Deformation Mechanism in Hot Compressed AZ31 Magnesium Alloy
Authors: Meng Li , Yang Ping , Zhao Zude , Mao Wei Min
Published: March 2009

Orientation mapping based on EBSD technique was applied to analyze the rules of
orientation evolution of grains in AZ31 magnesium alloy. Results show that not only under deformation strain rate of 1×10-2s-1, but under 4×10-4s-1(the superplastic deformation condition), grains in all samples with initial textures rotate gradually to near basal orientation ({0002} || compression plane) at different ways, and basal texture becomes stronger with increasing strain, which indicates plastic slip plays an important role during hot deformation. Otherwise, no evident non-basal pyramidal slip of  as some studies mentioned was observed in the sample with the initial basal texture, and the basal orientation is kept unchanged during the deformation process, which suggests that basal slip is the uppermost plastic slip mechanism in this sample. In addition, the phenomenon of viscous laminar flow was observed in the sample with initial basal texture.
Microstructure and Mechanical Properties of Ceramic Coating on AM50 Magnesium Alloy by Microarc Oxidation
Authors: Zhao Hui , Chen Ji , Liu Zhen
Published: March 2009

The coating formed on AM50 magnesium alloy by microarc oxidation (MAO), using DC pulse power in Na2SiO3 solution. The oxide coating contains a loose layer and a compact layer, the loose layer consisting of MgO, Mg2SiO4 and MgSiO3 phases and the compact layer mainly of the MgO phase. The curves of hardness (H) and elastic modulus (E) across the coating are similar, from the surface to the interior of the coating, H and E increase, and both of them exhibit a maximum value at the same depth of the coating. After MAO treatment, the mechanical properties, such as hardness and elastic modulus, can be improved, and the microstructure of the alloy substrate has not been changed.
Comparison of Corrosion Properties of Squeeze Cast and Thixocast MgZnRE Alloys
Authors: Blawert Carsten , Morales Emma D. , Dietzel Wolfgang , Kainer Karl Ulrich
Published: March 2009

Thixocasting is a new semi-solid processing route for magnesium alloys; it is claimed
that finer microstructures can be produced and as a consequence, better corrosion resistance can be achieved. Therefore, it is of great interest to compare the corrosion properties of two Mg-Zn-RE alloys produced by standard squeeze casting and new semi-solid casting technique. The influence of the two different processing routes and the replacement of rare earth elements by Ca additions on
the corrosion behavior were studied in NaCl aqueous solutions by (a) analyzing the corrosion morphology, (b) measuring electrochemical polarization curves, and (c) carrying immersion tests at constant pH-value. Using light microscopy, scanning electron microscopy and X-ray diffraction, the corrosion results were related to the microstructures on the specific alloys. The results indicate that Ca cannot replace rare earth elements under corrosion aspects, but they also showed that the thixocasting process resulted in better corrosion resistance.
Effect of Aging on Yield Stress and Corrosion Resistance of Die Cast Magnesium Alloy
Authors: Song Guang Ling , Bowles Amanda L. , StJohn David H.
Published: March 2009

Corrosion resistance is an important property that could be affected by the ageing
process. In order to investigate whether aging affects the corrosion resistance, corrosion rate and yield strength of diecast magnesium alloy AZ91D were measured and analysed after ageing. It was found that the dependence of the corrosion rate on ageing time can be ascribed to the changes in microstructure of the alloy and chemical composition of its matrix. Precipitation of the β phase (Mg17Al12) occurred along the grain boundaries during the initial ageing stages, resulting in a
decreasing corrosion rate and an inceasing yield strength. In the later stages, the decreasing aluminium content in the a matrix made it more active, causing an increase in the corrosion rate. The decrease in aluminium content in the matrix also leads to a decrease in yield strength.
Fatigue and Corrosion Fatigue of Magnesium Alloys
Authors: Zeng Rong Chang , Han En-Hou , Ke Wei
Published: March 2009

This paper consists of a review of investigations and the factors affecting the fatigue of Mg and its alloys. The effect of materials, loading conditions and environmental factors on fatigue is discussed in detail. Particular attention has been paid to the influence of frequencies and the pH value of solutions on the fatigue life. The correlation between the threshold stress intensity factor range (ΔKth) and load ratio (R) for Mg alloy fatigue crack propagation (FCP) is summarized in a
figure. Finally, the mechanisms of fatigue and corrosion fatigue (CF), crack initiation and crack propagation are also discussed.
Mechanical Properties and Creep Behavior of Mg–Al–Ca Alloys
Authors: Liu Man Ping , Wang Qu Dong , Zeng Xiao Qin , Yuan Guang Yin , Zhu Yan Ping , Ding Wen Jiang
Published: March 2009

This paper investigates the microstructure, mechanical properties and creep behavior of Mg–Al–Ca alloys with different Ca content. SEM and EDAX analyses show that the dominant second phase in the as-cast Mg–Al–Ca alloys is Al2Ca, which distributes at the grain boundaries and disperses in the grain interior as well. Both the elevated tensile strength and the creep resistance of Mg–Al–Ca alloys obviously increased with increasing Ca at high temperature. TEM analyses reveal
that finer Al2Ca particles with an average size of 0.02 µm precipitated dynamically during the creep process. Selected area electron diffraction (SAD) patterns show that the dynamic Al2Ca precipitates have a coherent interface with matrix as (0110) Mg // (220) Al2Ca, [2110] Mg // [112] Al2Ca. The strengthening mechanism of Mg–Al–Ca alloys at elevated temperature was discussed.