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A study has been made of blow forming of 3㎜ thick superplastic 8090 Al alloy sheets into a 6㎝ dia. cylindrical die and a 3㎝ × 9㎝ rectangular die to form a hemispherical cup and plane strain deformation, respectively. Forming pressure-time curves for hemispherical cup forming and plane strain deformation have been analytically calculated using Ragab`s method and Ghosh`s method, respectively, which are based on the membrane theory. The flow curves for calculation of the pressure-time curves were measured at an optimum strain rate. The measured deformation behaviors of the sheets during blow forming in accordance with the forming pressure-time curves have been compared with results predicted by the analytical methods and the elasto-plastic finite element method. The pole height, stress and strain distributions, and thickness distributions of the formed cups are better simulated by the FEM than the analytical methods.

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Bioceramics for artificial dental crowns in dentistry have been fabricated by sol-gel process and melting method, respectively. Sintering characteristics have been investigated after compositing powder mixtures relative to leucite content(0∼30wt.%) added to glass matrix. Highly pure leucite powders have been fabricated by sol-gel process and glass powders have been manufactured with 20∼30㎛ particle size by a melting method. Sintering temperatures could be controlled from 1020℃ to 1175℃ relative to the powder mixtures of leucite and glass powders. The relative sintered density was 80∼83% of theoretical density. Shrinkage was about 20∼25% after sintering.

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Planar Flow Casting has been carried out so as to develop the continuous process which can produce the wide polycrystalline ribbons up to 50㎜ width with reliability. The material used in this investigation was tin for the sake of ease in processing. A series of experiments have been performed with 50㎜ width graphite nozzle, using argon gas to eject the molten tin onto a rotating steel substrate. The process conditions have been varied in order to determine the optimun casting parameters for the apparatus used. The basic relationships between the process parameters and ribbon geometry were exanined by measuring the thickness, surface roughness test, optical microscopy, SEM and XRD analysis. Polyscrystalline ribbons of several hundred ㎛ thick and 50㎜ wide have been cast continuously exceeding 30m in length for one batch procedure. The empirical relationship t.=8.785(Q^(0.17)/V^(0.84)) was proposed for the description of the dependence of ribbon thickness on melt flow rate and substrate velocity.

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A comprehensive mathematical model that combines turbulent transport phenomena of particle-laden gas jets, chemical reaction, and thermal radiation has been developed to describe the various aspects of chalcopyrite concetrate combustion inside an axi-symmetric reaction shaft of flash-furnace. The key features include the use of the k-ε turbulence model, incorporating the effect of particles on turbulence and the four flux-model for radiative heat transfer. Numerical computations have been performed predict the various aspects of rate processes occurring in a commercial-scale flash-smelting furnace for different inlet feeding modes. Model predictions indicate that the overall performance of the flash-smelting furnace is greatly affected by the inlet geometry and the gas-phase turbulent field is significantly affected by the presence of particles. Model predictions also show that the reaction of sulfide particles is almost completed in the upper zone of the furnace within about lm from the burner, the axial wall feeding mode of the secondary jet shows better performance than any other feeding modes considered in this study. The study of the commercial scale flash-smelting operations can be summarized as follows: (1) Reactions of sulfide particles are almost completed in the upper zone of the flash-furnace shaft, within about 1m of the burner tip in most cases except the axial feeding modes of both input streams. (2) Model predictions indicate that the overall performance of the flash-smelting furnace is greatly affected by the inlet geometry. (3) The double-entry burner system with the radial feeding of the concentrate-laden distribution air shows better performance than the single-entry burner system. (4) The axial wall feeding mode of the secondary jet is one of the recommended input geometries for good performance of the flash-smelting operation with an axisymmetric furnace shaft.

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Electrochemical insertion and removal of lithium into nickel oxide films prepared by reactive sputtering have been investigated. The chemical diffusion kinetics of lithium in NiO thin films have been evaluated by Cyclic Voltammetry and AC impedance spectroscopy. It has been found that charge transfer density improves as NiO becomes lithiated and enhancement of lithium diffusion coefficient with increase of x in Li_xNiO is mainly responsible for it.

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It is described a computational model of the gas phase diffusion m reaction in the chemical vapor deposition reactor. The model, consider a diffusion mixing mode of source material for the reaction of SnCl₄ and water vapor, predicts condensable chemical species concentration distribution as a function of partial pressure of SnCl₄, reaction temperature and total vapor pressure in the reactor. It also predicts a particle size by collision theory. It is founded good agreement with experimental results. The model indicates concentraction distribution of condensable chemical species is important in predi partcle size.

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The effect of titanium addition on the deoxidation and denitrogenization of stainless steel was studied by laboratory scale experiments using a 50㎏ induction furnace at 1600℃. The equilibrium dissolved oxygen content in 18%Cr-8%Ni steel containing titanium concentration between 0.1 and 0.35wt.% is in the ranges from 35 to 40 ppm in agreement with the measured values. The deoxidation products formed in liquid steel were identified as TiO and TiO₂ at the Ti concentration between 0.15 and 0.25wt.%. These oxides were found to have spherical shape of single phase with the size less than 3㎛. Titanium nitridue(TiN) of hexagonal shape was formed mainly as clusters. The top slag treatment of CaO-Al₂O₃ was found to be superior to the 100%CaO treatment in removing titanium oxides and nitrides out of the melt.

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The steady state shapes of solid-liquid interface under various conditions, during directional solidification of pure materials between two straight walls, were calculated by numerical analysis. The transition from the interface shapes governed by the interface energy to that governed by the mobility can occur as the pulling rate changes. At a high pulling rate where the interface shapes are governed by the mobility anisotropy, there is a critical mobility anisotropy above which the faceted interface appears. At a high pulling velocity and with a high mobility anisotropy, the faceted interface shapes depend on the wetting angle, ψ between the interface and the wall only at the range of π/4$lt;ψ$lt;5π/4. At the other range of wetting angle the macroscopic interface shape is independent of the wetting angle. The faceted interface can be composed of the planes with high crystallographic indices if the mobility anisotropy, at the high pulling velocity, is slightly larger than the critical value or if the wetting angle, at the high pulling velocity and with the high mobility anisotropy, is at a range of π/4$lt;ψ$lt;π2.

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An attempt io explain the low temperature fracture mechanism was made by investigating fracture processes involued in microcrack formation of an 8090 Al-li alloy. A specially designed chilling equipment was attatched to a wedge loading stage in an SEM for the low temperature in-situ observation. In the S-L oriented specimen, microcracking occurred along grain boundaries at the low stress level, and the crack propagated readily along the grain boundary, while the cracked grain boundary did not appear to have any significant effect on the crack propagation process in the L-T oriented specimen. It is interesting to note that slip bands were hardly observed at the low temperature case, although a number of slip bands were found at room temperature because of the well developed planar slip lines. Thus, the direct observation of the crack initiation and propagation strongly suggests that the most important factor affecting the cryogenic properties of the 8090 Al-Li alloy is a slip mode since homogeneous slip was predominant at cryogenic temperatures.

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Densities and electrical conductivities in D₂O-Pb(NO₃)₂ binary solutions have been measured. The densities could be represented as the 1st order linear equations of concentration and temperature, but the electrical conductivities as the 2nd order one of the same parameters. Molar volumes exhibit negative deviations from a additive line at all compositions tested. This means the packing states of the solutions are more dense than the single phases. The equivalent conductivities derived from the electrical conductivities showed general characteristics that could be observed in the electrolyte of 2-1 ionic valances.

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