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The effects of high-energy electron beam irradiation on surface hardening and microstructural modification in a gray cast iron currently used for a diesel engine cylinder block were investigated in this study. The gray cast iron samples were irradiated by using an electron accelerator (1.4 MeV ), and then their microstructures, hardnesses, and wear properties were examined. Upon irradiation, the unirradiated microstructure containing flake graphites and the pearlite matrix was changed to martensite, ledeburite, and retained austenite, together the complete or partial decomposition of graphites. This microstructural modification improved greatly the surface hardness and wear property due to transformation of martensite whose amount and type were determined by the input energy density during irradiation. The peak hardness and the case depth were increased linearly with increasing the input energy density, and thus the high-energy electron beam irradiation can be effectively applied to the surface hardening process of a diesel engine cylinder block.

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Thermal analyses of the surface layer of a gray cast iron irradiated with high-energy electron beam have been studied. In order to investigate the complex microstructures which were composed of plate martensite, retained austenite, ledeburite, and flake graphite, the thermal analysis using a heat-transfer model and the simulation test including thermal cycles of abrupt heating and quenching were carried out. The results indicated that the irradiated surface was heated up to the austenite temperature region and then quenched to room temperature, which was enough to obtain surface hardening through martensitic transformation. When the surface temperature reached the melting temperature, the ledeburite eutectic structure was formed. The thermal analysis data matched well with the microstructures of the thermally simulated specimens, confirming that the thermal analysis is quite useful for the microstructural analysis of the surface layers irradiated with high-energy electron beam.

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The effects of infiltration temperature and time on the infiltration behavior of molten metal, tensile properties and interfacial reaction in Al-3wt%Mg/SiC_p composite fabricated by pressureless infiltration method were investigated. It is believed that spontaneous infiltration of molten metal is related to the formation of Mg₃N₂ by the reaction of Mg and nitrogen. The addition of Mg to the powder mixture bed made the infiltration occur even at a low temperature of 700℃. Tensile and y field strengths and elongation tended to decrease with increasing infiltration temperature and time, due to enhancement of interfacial reaction. Both Al₄C₃ and Si were formed as a result of the interfacial reaction between Al alloy melt and SiC particulates. The Si rejected into the matrix which combined with the Mg in the matrix during aging after solution treatment led to the age hardening.

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Effects of coating treatment of metallic Cu and Ni-P film on SiC fiber for Al/SiC composite were studied. Ni-P and Cu were deposited on SiC fiber by electroless plating method. The morphology of coated film and wetting behavior of composite were analysed by SEM The coating treatment on SiC fibers improved wettability of Al melt on SiC comparing to the non wated SiC fiber, and especially Ni-P coating turned out most effective. This improved wettability seems strongly concerned to the increase of chemical reactivity between coating layer and Al matrix. The reaction between Al melt and coated metallic film forms eutetic melt, and those reaction may accelerates the break down of Al oxide film to promote wettability positively.

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The organic type ECD device for optical shutter on DVD player was successfully fabricated & evaluated. This device employ : an evaporated a-WO₃ film as electrochromic layer ; a PVDF-EC-NMP-THF-LiClO₄ as electrolyte layer ; a NiO film as counter electrode ; and ITO layer as transparent electrode between soda-lime glass substrate. This ECD shutter exhibited an useful operating characteristic such as contrast ratio as high as 30 to 1 in the transmission mode with an He-Ne laser(632.8㎚), operating voltage of lower than 2.5V, and response time less than 0.5 sec at room temperature. Cycling test with coloring and bleaching on this device was carried out for more than several hundred times, along with analysis and evaluation of optical properties & microstructure of fabricated layers by means of spectro-photometer, TEM and XRD method, and the accumulation of Li in both a-WO₃nd ITO film after cycling test was investigated by AES & SIMS analysis. From this research, it is found that a number of factors including maintenance of uniformity in both film & electrolyte, prevention of Li ion accumulation in film, optimization of structure design and good sealing condition can contribute to attaining the improvement of properties & life extension in ECD shutter for DVD player.

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Giant magnetoresistance(GMR) has been investigated for Co_xCu_(100)-x liquid quenched ribbons. Solid solutions were obtained for a concentration with X<15, and the microstructure associated with the spinodal decomposition produced by isothermal aging for Co_(10)Cu_(90) ribbons is closely correlated with the giant magnetoresistance. In the phase decomposition in the constant wave length region, the MR ratio due to the spin dependent scattering increases with the increase in the surface-to-volume ratio. By longer aging, the MR ratio decreases with the increase of the wavelength, while the field dependence of the MR ratio becomes larger in low field due to the coalescence of the magnetic particles. On the other hand, the lower isothermal aging temperature, the shorter periodic fluctuation of the composition, and accordingly the largest MR ratio of 8.1% is achieved by aging at 673K for 166h.

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The microfailure of thin-film interconnect by electromigration phenomena is one of the primary causes to degrade the reliability of microelectronic circuits. Tn this study, we analyzed the electromigration-induced microfailure considering thermal stress effect in the interconnect. The thermal stress is generated by the difference of thermal expansion coefficient between metal interconnect and oxidized silicon substrate. This thermal stress, which is developed during fabrication, produces the defects such as microvoids which accelerate the electromigration. The effect of thermal stress on the electromigration-induced failure was analyzed via the kinetic considerations. For those, after applying different thermal cycles to develop various thermal stress in the test specimens, the MTF (mean time to failure) was evaluated by measuring the change of electrical resistance during the electromigration test. And then, the apparent activation energy for electromigration was calculated. The experimental results show that the apparent activation energy and MTF tend to decrease with increasing thermal stress. Microvoids due to thermal stress are the important factor to accelerate the electromigration-induced failure. And, the presence of stress-induced microvoids was ascertained by the fact that the initial resistance increases with increasing thermal stress.

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Manganese nodules have high porosity and specific surface area and comprised mainly of δ-MnO₂ which has excellent adsorption capacity for heavy metal ions. The principal purpose of this study is to examine the practical applicability on the removal of heavy metal ions from a waste water using the nodules as an adsorbent. The nickel adsorption capacities of the manganese nodule were 8.0㎎ Ni/g at solution pH 1.5 and 28.0㎎ Ni/g at pH 4.5, respectively. The adsorption of nickel ion was found to be an endothermic reaction and increased with temperature between 20 and 80℃ from 28.0㎎ Ni/g to 36.0㎎ Ni/g. The adsorption of nickel on the nodule powder increased with the decreasing particle size. The amount of nickel adsorbed on the nodule powder descreased with the increasing heat treatment temperature of the nodule powder (without heat treatment : 28.0㎎ Ni/g, with heat treatment at 500℃ 16.5㎎ Ni/g).

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Oxidation behavior of Ti-45at%Al-1.6at%Mn intermetallic compounds fabricated by respectively a reactive sintering and a melt process was studied at the temperature range of 800 1100℃. The reactive-sintered alloy showed superior oxidation resistance to the melted alloy above 900℃. Protective Al₂O₃ scale was formed up to 1000℃ on the reactive sintered alloy, while such scale was only visible at 800℃ for the melted alloy. According to Pt diffusion marker experiment it was found that oxide scale of the reactivesintered alloy grows inward below 1000℃, while both the inward and outward growth of oxide scale is observed for the case of the melted alloy above 900℃. The excellent oxidation resistance of the reactive-sintered alloy was considered to be due to the existence of chlorine, and/or both carbon and chlorine which were introduced from raw titanium powders. Chlorine could decrease oxygen ion vacancies in TiO₂ from the early stage of oxidation so that TiO₂ growth was interrupted and protective Al₂O₃ scale was easily formed on the reactive-sintered alloy. The growth of TiO₂ could also be interrupted by the chlorination of TiO₂ at the presence of both Cl₂ and C, or both Cl₂ and CO for the reactive-sintered alloy.

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Retained δ-ferrite in 304 stainless steel is known to prevent hot cracking during continuous casting. Excess content of retained 8-ferrite lowers the hot workability. So it is necessary to control the amount of retained E-ferrite in stainless steel. A numerical model based on coupled analysis of macro heat transfer and micro diffusion transformation has been developed in order to predict retained δ-ferrite in continuously cast 304 stainless steel slab. The finite difference technique for moving boundary problem has been formulated utilizing "Murray-Landis wariable-grid method". The reliability of numerical model is compared with the other results. The prediction of δ-ferrite content in CC type 304 stainless steel slabs shows good agreement between measured and predicted results. Effect of secondary cooling condition on the δ-ferrite has been also investigated.

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