Texture Formation Behaviour during High-Temperature Plane Strain Compression Deformation in AZ91 Magnesium Alloy

Han, Dong Keun,Park, Min Soo,Kwon, Han Sang,Kim, Kwon Hoo Scientific.Net 2018 Materials Science Forum Vol. No.

<P>In previous study, it was investigated texture formation behaviour of high-temperature plane strain compression test at 723K, under a strain rate of 5.0. It was found that the main texture component and it was sharpness vary depending on deformation conditions. To clarify the characteristic of texture formation behaviour, it is necessary to investigate at various deformation condition. Therefore, in this study, is investigating the influence or texture formation behaviour and strain, strain rate at 673K. Three kinds of specimens with different initial textures were machined out from a rolled plate having a <0001> texture. The plane strain compression tests were conducted at a temperature 673K, and a strain rate of 5.0, with strain between-0.4 to-1.0. After compression tests, the specimens were immediately quenched in oil. The texture evolution was conducted by the Schulz reflection method using Cu Kα radiation and EBSD. Before the deformation, {0001} of specimen A was accumulated in the center of pole figure. The {0001} of specimen B was accumulated at the RD direction. The {0001} of specimen C was accumulated TD direction. As a result, work softening is observed in all the cases at the true stress - true strain curve for three types of specimens. After deformation, the maximum pole density of increases with increasing strain. In this study, it was found that the stable orientation was (0001)<100> and (0001)<110> during deformation.</P>

Preparation and Characteristics of Monodispersed MFe₂O₄ Nanoparticles for Applications in Biomedicine

Park, S.I.,Kim, J.H.,Kim, Cheol Gi,Kim, Chong Oh Scientific.Net 2007 Materials Science Forum Vol.558-559 No.1

<P>The monodispersed hydrophilic magnetic fluids with nanometric MO·ferrite (M=Cu, Co, Ca, Ni) particles were prepared by the sonochemical method. The substituted amounts of M elements were analyzed with different x values by ICP-AES quantitatively for MxFe3-xO4 particles.</P>

Nanoporous Titania by Embossing with PMMA Nanopoles Made from Nanoporous Alumina Template

Her, Hyun Jung,Kim, Jung Min,Lim, Yun Soo,Kim, Jae Wan,Choi, Y.J.,Kang, C.J.,Kim, Yong Sang Scientific.Net 2007 Materials Science Forum Vol.544-545 No.-

<P>We produced highly uniform nanoporous thin films of the dense array of titania (TiO2) pores of 70~80 nm in diameter with nanoimprinting method. Titania in HCl and 2-propanol solution was coated on an indium tin oxide (ITO) surface and embossed with an array of PMMA nanopoles which was produced using a nanoporous alumina (Al2O3) template. Two-step anodization was introduced to produce highly uniform and dense nanopores on the aluminum surface. The polymethyl methacrylate (PMMA) was poured onto and infiltrated into the nanoporous alumina surface which was heated at 150 oC. The alumina nanopores and aluminum plate were removed by wet-etching leaving an array of PMMA nanopoles. These highly uniform nanostructured titania films will be very useful for photovoltaic and photocatalytic applications where nanostructuring of surface with controlled dimensions are essential.</P>

Characteristic of Carbonation Reaction from Municipal Solid Waste Incinerator Bottom Ash as a Function of Water Content and their Effect on the Stabilization of Copper and Lead

Ahn, Ji Whan,Cho, Hee Chan,You, Kwang Suk,Han, Gi Chun,Um, Nam Il Scientific.Net 2007 Materials Science Forum Vol.544-545 No.-

<P>Most carbonation processes utilizing municipal solid waste incineration bottom ash characteristically involve a high water content (over 100%). In this work, we developed an improved carbonation process, utilizing various water contents. In addition, we investigated the characteristics of a carbonation reaction using municipal solid waste incinerator bottom ash as a function of water content and their effects on the stabilization of copper and lead. As a result of such a carbonation reaction, the effect on the stabilization of heavy metals can be obtained. Due to this, the leaching concentrations of these were reduced. In a high water content, calcium aluminum compounds via carbonation reaction adsorbed Cu and Pb ions. Where a low water content (especially 30%) is present, particle surfaces are surrounded by calcium aluminum compounds of bottom ash as a result of the carbonation process. The leaching concentration of Cu and Pb were decreased through the carbonation process.</P>

Design of Manufacturing Process of Oxygen-Free High Conductivity Copper Using Mahalanobis-Distance Outlier Detection Method

Lee, Jung Il,Lee, Joo Ho,Park, Seung Hwan,Choi, Han Shin,Cho, Hoon,Jo, Hyung Ho,Kim, Skae K.,Kwon, Hyuk Chon,Hong, Jung Eui Scientific.Net 2007 Materials Science Forum Vol.544-545 No.-

<P>The proper control of total impurities and oxygen contents of oxygen-free high conductivity (OFHC) copper prepared by vacuum high-frequency melting technique was studied using Mahalanobis-Distance (MD) outlier detection method as functions of raw material purities, vacuum pressure, melting temperature and holding time. The properties of vacuum-melted OFHC copper was examined by thermo-gravimetric analysis, differential scanning calorimetry, hardness test, macro and optical microstructure analyses and ultimate tensile test. In multivariate systems, the existence of outlier makes it difficult to analyze the system and oultier detection belongs to the most important tasks in experimental data analysis. Mahalanobis Distance is most commonly used as a diagnosis of existance of outlier in multivariate system. The relationship between experiment conditions and total impurities and oxygen contents can be defined with the regression analysis results. At this research, our desirable manufacturing conditions is to obtain the total impurities under 40 ppm and oxygen contents under 5 ppm. After this statistical approach, the suggested minimum maufacturing conditions are the purity of raw material was 4N, vacuum pressure was 10-1 torr, melting temperature was 1150°C and melt holding time was 20 minutes.</P>

A Study on the Electrochemical Properties of PEO-Carbon Composite Polymer Electrolytes for Lithium/Sulfur Battery

Choi, Young Jin,Kim, Sung Hyun,Park, Sang Choul,Shin, Dong Hyun,Kim, Dong Hun,Kim, Ki Won Scientific.Net 2007 Materials Science Forum Vol.544-545 No.-

<P>In this study, we investigated ionic conductivities of the electrolytes and cycle performances of Li/S cells using the electrolyte. (PEO)10LiCF3SO3 composite polymer electrolyte(CPE) containing carbon powders and Brij dispersant was prepared by ball milling for 12hr. The 5wt% carbon powders having high surface area (~ 80 m2/g) was added into the (PEO)10LiCF3SO3 electrolyte. To get a well-dispersed structure, Brij dispersant was also added into the (PEO)10LiCF3SO3-5wt%Carbon electrolyte. Li/CPEs/50wt%S cells showed initial discharge capacities of between 1,250 and 1,413 mAh/g-sulfur with current density of 100 mA/g-sulfur at 80 °C. These results led us to conclude that the dispersants added into the CPE improved the initial discharge capacities and cycle performances.</P>

Milling and Sintering Behavior of the Metal-Ceramic Mixed Powders

Yang, Z. X.,Youn, Sang Heum,Hwang, Kyu Hong,Yoon, Seog Young,Lee, Jong Kook,Kim, Hwan Scientific.Net 2007 Materials Science Forum Vol.534-536 No.1

<P>The reaction-sintered alumina ceramics with low firing shrinkage were prepared from Al/Al2O3 powder mixture by attrition milling and the effect of milling characteristics of raw powders on reaction sintering was investigated. Powder mixtures of flaky shape Al with coarse alumina was much more effectively comminuted by the attrition milling than the mixtures of globular shape Al with coarse alumina powders. Furthermore the coarse alumina was much more useful in pulverizing and grinding the ductile Al particles than fine alumina. After attrition milling and isopressing at 400MPa, the Al/Al2O3 specimen was oxidized at 1200°C for 8 hours followed by sintering at 1550°C for 3 hours. Because mixed powder of coarse alumina with flaky Al was much more effectively comminuted than the globular Al, sintered body of more than 97% theoretical density was achieved, but low contents of Al leads to relatively higher shrinkage of about 8%. As the coarse alumina particles are much more useful in cutting and reducing the ductile Al particles, the use of the coarse alumina powder was much more effective in reaction-sintering.</P>

Effect of Product Quality on Life Cycle Assessment in Aluminum Die Casting Process

Scientific.Net 2007 Materials Science Forum Vol.544-545 No.-

<P>Driven largely by the never ending quest for weight reduction to decrease fuel consumption and emission, the automotive industry is predicting significant growth in the use of aluminum alloys. Generally, cold chamber type die casting process is utilized for aluminum alloys. In order to comply with the growing demand for life cycle environmental effect, life cycle assessment (LCA) was carried out for producing A356 aluminum alloy by cold chamber type die casting process, based on what has been experienced as needed for LCA study. The main emphasis of this study is to evlauate the effect of trial of improving die casting process and product quality on the environmental value obtained by LCA. Also the results will be compared by the trial of life cycle improvement. In LCA, the process evaluated was based on yields of finished parts relative to the metal input. This is important both in environmental point of view and in commercial point of view, because the environmental data are sensitive to the design of the cast part and the efficiency of the die casting operation.</P>

Expansion Behavior of Iron-Copper Compact from (FeCu) Pre-Alloyed Powder

Kim, Youn Che,Suk, Myung Jin Scientific.Net 2007 Materials Science Forum Vol.534-536 No.1

<P>Dilatometric curves of iron-copper compact made from elemental or pre-alloyed powder were compared in order to study its expansion mechanism. The compacts from a mixture of elemental iron and copper powders showed the maximum expansion at the copper powder content of 7.44mass% and at the sintering temperatures above the copper melting-point. In the case of the compacts from a mixture of iron pre-alloyed powder of (Fe- 3.44mass%Cu) and copper powder, the maximum expansion which is lower than the former case was obtained at the additive copper powder content of 4.00mass%. But the compact from a mixture of iron pre-alloyed powder of (Fe-7.18mass%Cu) and copper powder showed only shrinkages at any additive copper powder content. The penetration of liquid copper into the interstices between solid grains was observed in all sintered compacts. The iron-copper compacts containing the same content of copper powder showed a very different expansion behavior depending on the amount of copper content in the starting iron raw powder.</P>

Remodeling Techniques of Water Storage Tanks and Residual Chlorine Remaining Devices

Kim, Seog Ku,Lee, Hyun Dong,Kwak, Pill Jae,Kim, So Jung,Hong, Seong Ho,Kim, Sung Jin,Choi, Ju Sol Scientific.Net 2007 Materials Science Forum Vol.544-545 No.-

<P>We developed the remodeling techniques of water storage tanks and the residual chlorine remaining devices. Eco-TIR((Total Internal Remodeling) is remodeling technique that cover the inside wall of concrete tank with SMC(Sheet Mold Compound) Block. Eco-SL(Stainless steel Lining) and Eco-GS(Glass sheet) is similar to Eco-TIR(Total Internal Remodeling) but stainless steel or glass tile is substituted for SMC block as a cover material. We tested the residual chlorine remaining devices and the results are as follows. First, it was estimated that mixing efficiency is increased if inflow energy to the water tank is used in the results of variation of residual chlorine concentration. Secondly, result showed that the removal percent of residual chlorine concentration was up to 90% by using ACF filter and feed water of high residual chlorine concentration can be controlled to 0.2mg/L〜0.4mg/L by using ACF and by-pass of inflow to the water tank. Also, in the water tank inlet pipe of 3-ways out using inflow energy is more effective in mixing than conventional inlet pipe. It is expected to enhance the safety of service water and management efficiency by applying mentioned techniques properly.</P>