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The characteristics of Li-Mn-O ternary compound was studied as a cathode active material for lithium secondary batteries. Li-Mn-O cathode active materials were prepared by the reaction of γ-MnO₂(EMD) and LiOH·H₂O at 375℃ with various molar ratios. As the contents of lithium increased, the cyclic reversihility was improved. Compound with Li/Mn=3/7 molar ratio showed the best results, considering reversibility and discharge capacity at the same time. The effects of the types of MnO₂ on the cyclic behaviour were also studied. It was shown that the channel structure of MnO₂ played important roles on the cyclic behaviour of Li-Mn-O cathode. Themodynamically, the larger the channel size, the greater the discharge capacity. The α-phase, however, which has the largest [2×2] channels showed lower lithium ion diffusivity than the γ phase having [1×2]+[1×1] channels. It was thought that this behaviour was attributed to the impurities inserted in the process of synthesis of α-MnO₂, So, as the discharge rate increased, γ-phase showed better result than α phase.

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The fine flake type graphite, directionally solidified from Fe-3.4 wt % C-2 wt % Si alloys doped with either 0.02 wt % S or 0.05 wt % Te, was investigated by using a transmission electron microscope. The presence of rotational stacking faults was observed in more than 90% of the graphite samples examined here, regardless of the doping element S or Te. The two elements were, however, found to have a distinctly different effect on the selection of rotation angles. The S-doping induced in the fault formation the various rotation angles predicted by theory, while the Tedoping induced angles mostly close to 30 degrees.

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A computational method, which is based on a modified SMAC method, has been developed to analyze three dimensional incompressible viscous flow in mold filling. A marker transport technique was used for the purpose of tracing three-dimensional melt free surfaces, and a marker generation method was adapted to treat an arbitrary number of inlet or outlet boundary conditions for the design of gating systems. In order to enhance the solution accuracy, the convective terms were treated by the hybrid scheme. Simulations were carried out on two types of stepped plate die casting and a three-spoke wheel gravity casting, in order to analyze the filling sequence and to predict cold shut or entrapment of air. Computational results on the two types of stepped plate casting were in good agreements with those of water model experiments.

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DLC(Diamond-Like Carbon) films were deposited using a CH₄-Ar ECR plasma on either Si or slide glass substrates. RF bias was applied to substrate to study the effects of the ion bombardment energy on the structure and properties of the deposited film. We identified that the hard carbon films were obtained above 40V bias. The transition of the as-deposited film from soft polymer-like to hard diamond-like was identified by using Knoops microhardness test, Ellipsometry, Roman and FT-IR spectroscopy. The plasma potential of about 20V were measured at a place close to the substrate to be independent of the rf bias by inserting single langmuir probe into CH₄-Ar ECR plasma. The impacting ion energy was thus calculated by summing the ion energy at bulk plasma and the accelerating energy in sheath due to the plasma potential and rf negative bias. From this we can conclude that the impacting ion energy higher than 60 eV is required to obtain hard diamond-like carbon films.

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A new mechanism of MoSi₂ formation during self-propagating high-temperature synthesis(SHS) was proposed based on the observation of the reaction front quenched into liquid nitrogen and copper block. The effects of processing variables such as Mo particle size, preheating temperature, and diluent content on the size of MoSi₂ powders formed were discussed based on the mechanism proposed in this study.

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The corrosion and microstructural characteristics with heat treatment of Zircaloy-4 alloy were investigated for the specimens heated in the temperature range of α, α+β and β. The microstructures of specimens heated in the α, α+β and β range showed the equiaxed α, the mixed type of equiaxed and widmansta¨tten structure, and widmanstatten structrue, respectively. As the annealing temperature increased, the volume fraction and size of precipitates decreased. Mini autoclave tests were carried out at steam temperature of 500℃ and steam pressure of 1500psi to investigate the effect of annealing temperature and annealing time on the corrosion resistance of Zircaloy-4 alloy. It was observed that the corrosion resistance of β-heat treated specimen was higher than that of α-heat treated specimen. From combining the present results with other works, it is suggested that the nodular corrosion occur in the local region where alloying elements are depleted.

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In this study we have tried to fabricate nitride particle-reinforced composite materials through blowing nitrogen gas into Al-Li alloy melts, and identified the formation of nitride particles such as AlN and Li₃N. The average size of AlN and Li₃N dispersoids formed by nitriding reaction were a few ㎛ and nm order, respectively. The addition of Mg appeared to be effective to facilitate the nitriding reaction and to prevent the loss of Li due to deoxidation in the melt. And the tensile strengths of these N₂ gas-blowed composites were greatly increased compared to that of unblowed Al-Li alloy. Therefore it is clear that the formation of nitride particles had a great effect on the increase of tensile strength of the composites. However, long time blowing of more than 20 minutes resulted in a decrease of tensile strength due to the removal of preformed nitrides by the blowing gas. Ductility, which is a major problem of Al-Li alloys, is also greatly improved by this process compared to that of conventional Al-Li alloys.

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A thermodynamic assessment of the Ti-Ni binary system has been made by applying the CALPHAD method. A set of self-consistent Gibbs energy parameters describing all the present phases in the system has been obtained through a least-squares optimization procedure using the available thermodynamic and phase equilibria information. The calculated phase diagram as well as the thermodynamic functions are in good agreements with the experimental data available in the literatures. The thermodynamic aspects on the glass forming ability in the Ti-Ni system are briefly discussed based on the To criterion. The calculated thermodynamic functions and phase diagrams are presented with the optimized thermodynamic parameters.

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Smelting reduction behaviors of the chrome ore by carbon with and without CaCO₃ as a flux were studied to understand its effects on reduction rate and possibly to determine the rate controlling step. Mixed powder batches of chrome ore and stags of CaO-MgO-Al₂O₃-SiO₂ in various concentration of MgO and Al₂O₃ combined with a constant ratio of CaO to SiO₂ at an unity were held in graphite crucible for 120 minutes at 1600℃. The results were as follows: An addition of CaCO₃into chrome ore which resulted in a formation of low melting merwinite (C₃MS₂) had no effect on the reduction rate in slag of up to 45wt% of MgO and Al₂O₃ combined. Mass-transfer in slag phase was not likely a rate controlling step in view of an extremely vigorous stirring by CO generated at slag and graphite interface. The fractional conversion of chrome ore bore out zero-order reaction by a linear relationship with time within the threshold content of MgO and Al₂O₃, beyond which no further reaction took place. Chrome ore particles remaining unconverted at the termination of the experiment were surrounded by euhedral crystals of a high melting MgAl₂O₄ which had been precipitated from liquid slag due to accumulation of MgO and Al₂O₃. An addition of CaCO₃ into chrome ore acted as a diluent in the slag for Mg0 and Al₂O₃.

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