Designing, Processing and Properties of Advanced Engineering Materials

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Authors: Chung Hyo Lee, S.H. Lee, S.Y. Chun, Sang Jin Lee, Young Soon Kwon
Abstract: Nanocomposite formation of metal-metal oxide systems by mechanical alloying (MA) has been investigated at room temperature. The systems we chose are the Fe 2O 3-M(M=Al,Ti,Zn,Cu), where pure metals are used as reducing agent. It is found that nanocomposite powders in which Al 2O 3 and TiO 2 are dispersed in Fe matrix with nano-sized grains are obtained by mechanical alloying Fe 2O 3 with Al and Ti, respectively. However, the reduction of Fe 2O 3 with Cu by MA is not occurred. And the system of Fe 2O 3-Zn results in the formation of FeO plus ZnO after 120 h of milling. It is also shown that the magnetic evidence for the solid state reduction by mechanical alloying through changes in saturation magnetization and coercivity.
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Authors: Chung Hyo Lee, S.H. Lee, S.Y. Chun, Sang J. Lee, Joo Sun Kim
Abstract: The mechanochemical reaction of hematite with graphite by mechanical alloying (MA) has been investigated at room temperature. The solid state reduction of hematite to Fe3O4 and FeO has been observed after 120 hours of MA by a planetary ball mill. Saturation magnetization is gradually increased with milling time up to 80 h, and then deceased after 120 h of MA, indicating the transformation of Fe3O4 into nonmagnetic FeO through further reduction. Neither the solid state reduction of Fe2O3 by graphite nor a sizable grain refinement is observed in the MA process using a horizontal ball mill.
257
Authors: Tea-Jung Chang, Sang Hoon Yoon, Yong Seog Kim
Abstract: Various closed-cells of plasma display panel were prepared via capillary moldingof paste containing ceramic powders of barrier ribs. The cells include meander, honeycomb, waffle and SDR. In this study, the sintering behaviors of such barrier ribs were investigated. The effects of pre-firing temperature, solid content in the paste, and type of cells on morphologies of the ribs were examined. The results indicated that cells with asymmetric geometry such as SDR and meander results in severe distortion after the sintering. The cells with symmetric geometry such as waffle and honeycomb, on the other hand, the distortion was negligible. Using the waffle type cells, the luminance characteristics of PDP device were evaluated.
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Authors: Tetsuhiko Onda, H. Yamauchi, Motozo Hayakawa
Abstract: The effect of CoO addition into Y-TZP (Yttria doped Tetragonal Zirconia Polycrystals) was studied on the evolution of its sintering ability, grain size, grain boundary structure and mechanical properties. The doping of a small amount of CoO effectively reduced the sintering temperature. A small amount of CoO up to ~ 0.3 mol% was effective for the suppression of grain growth, but the addition of 1.0 mole % resulted in an enhanced grain growth. The hardness and toughness of the CoO doped TZP were about the same as those of undoped TZP. Furthermore, despite the grain refinement, CoO doped TZP did not exhibit improved mechanical properties. This may be suggesting that CoO dopant had weakened the grain boundary strength.
265
Authors: Y. Harada, M. Ohmori, Lei Wang
Abstract: Serration phenomenon of sintered and cast chromium was investigated by means of tension test at various strain rates. With increasing test temperature, tensile strength decreased gradually at first and showed a minimum at a certain temperature. Above this temperature, the strength continued to increase to a maximum value. Serrated flow appeared between the temperatures of the minimum and maximum tensile strengths. Tensile ductility minimum was also observed around the temperature of the maximum tensile strength. Relation between the strain rate and the temperature T of the maximum tensile strength could be well described by an Arrhenius equation. Activation energy of 101.3kJ/mol found in the present study is in good agreement with the activation energy for diffusion of nitrogen atom in chromium.
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Authors: Ki Hyun Kim, Young Gab Chun, Byung Ok Park, Kyung Hoon Yoon
Abstract: Chalcopyrite CuInSe 2 (CIS) and CuInGaSe 2
273
Authors: Kang Sup Chung, Jae Chun Lee, Eun Jin Kim, Kyung Chul Lee, Yang Soo Kim, Kenta Ooi
Abstract: Adsorbing and salvaging extremely small quantities of lithium ion, high-performance ion-exchange type lithium ion adsorbent was prepared through the ion-sieve formation method. The method uses acid treatment after the synthesis of spinel-structured nano-Li1.33Mn1.67O4 precursor through the tartaric acid gel process. It has good selectivity and high efficiency in adsorbing lithium ion in seawater. The generated adsorbent showed a 28.2 mg/g lithium uptake from artificial seawater. This adsorbent further showed a difference reproducibility that was lower than 10% when subjected to five cycles of adsorption and desorption experiments.
277
Authors: Seijiro Maki, Yasunori Harada, Kenichiro Mori
Abstract: Resistance sintering characteristics of electrolytic and atomized copper powders mixed with graphite powder in steps of 10vol% up to 50vol% were experimentally investigated. In the experiments electrifying voltage and time, and applied pressure were varied. Post-electrification pressurization and insertion of low thermal conductive austenitic stainless steel discs between the sintering powder cake and electrodes were attempted to promote the sintering. The effects of the operational parameters including the two devices on sintering performance are discussed. Sintering strength of the resistance-sintered composites is also discussed.
281
Authors: Yong Nam Kim, Jeong Hyun Park, Hyun Gyu Shin, Jun Kwang Song, Hee Soo Lee
Abstract: Nanosized ITO powder was fabricated by homogeneous precipitation which used formamide as a precipitator. ITO thin film was deposited by RF magnetron sputtering using ITO target which was prepared by sintering of nanosized ITO powder. From the accelerated degradation test with stress factor of temperature, the lifetime estimate, degradation rate/degree, activation energy and etc. were calculated. It was showed that under thermal condition, the prominent failure mechanism of degradation was the decrease of oxygen vacancies due to oxidation of ITO thin film.
285
Authors: Jae-Kil Han, Sung Min Choi, Ik Hyun Oh, Fumio Saito, Byung Teak Lee
Abstract: TiO2(1-.ZrO2. (.=- 0.2, 0.4, 0.6 and 0.8) composite powders having a homogeneous distribution and nanocrystalline were successfully synthesized by sol-gel process using titanium iso-propoxide as precursor. The particle sizes of TiO2-ZrO2 powders calcined at 600°C were measured ranging from 10nm to 19nm by XRD and TEM. For the comparison of photocatalytic activity, TiO2-ZrO2 composite powders were tested in the degradation of phenol and the photoreduction of inorganic pollutants. The degradation of phenol increased with increase the content of anatase TiO2 phase.
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