발간논문

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Synthesis of an intermetallic compound based on Ti_5Si₃ by an explosive compaction of elemental powders was studied. The main experimental variable was the detonation velocity, and it was found that the relative density of the compacted compound increased with the detonation velocity. To enhance the density of the compound further, however, it was deemed necessary to consider variables such as the can, powder and the backup tube. From an X-ray diffraction analysis of the explosion-compacted compound it was confirmed that formation of the Ti_5Si₃ phase was complete. Apart from the needs to further improve the density and crack resistance of the compacted alloy, the present work indicates that the explosion synthesis has a potential to be developed as a consolidation method for Ti_5Si₃ intermetallic compounds.

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In order to utilize the limestone sludge of limestone calcination plant as a by-product, present study had been performed to estimate the usability of limestone sludge as a raw material of sinter mixture in iron ore sintering process and the influence of addition of limestone slurry and dried limestone sludge on the sintering properties. The results of sintering pot tests showed that limestone sludges might be used in iron ore sintering process in the phase of slurry and dried powder without the deterioration of sinter quality. The optimum density of limestone slurry and ratio of sludge to sinter mixture were 20% and 1.2%, respectively. In the respect of sinter quality, strength(TI) and reduction index(RI) was decreased with the increase of limestone sludge containing dolomite particles due to the decrease of calcium ferrite and the increase of low reducible magnetite of sinter.

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Kinetics of chemical vapor deposition of silicon on Ni substrate was investigated in the temperature range between 1173K and 1323K using hot-wall reactor and a gas mixture of SiCl₄ and H₂ The deposition rate of silicon was proportional to the square root of total flow rate of reactants and constant at a rate above 100sccm at 1273K and 300sccm at 1273K, respectively. The dependence of deposition rate of silicon on Cl/H input ratio was explained by the combined effect of that on the deposition rate and etching rate of silicon. Kinetics of silicon deposition obeyed the linear rate law. The deposition rate of silicon was controlled by the gas transport process through a gas boundary layer to the Ni substrate over 1248K and the activation energy for silicon deposition was 2.5 ㎉/mole. However, the rate determining step was chemical reaction process for silicon deposition below 1235K because the activation energy was 26.5 ㎉/mole, which was similar to that for silicon deposition on Si substrate.

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(Ti_(1-x)Al_x)N coatings of constant as well as continuously changing Al concentrations were deposited onto M2 high speed steel(HSS) substrates by the ion-plating method, and the microstructure and adhesion strength of the coatings were investigated. The Al concentration could be easily controlled by using separate evaporation sources for Ti and Al, and changing the evaporation rate of the metals. With increase of Al concentration, the grain size decreased and the microstructrure of the coating became denser. Although the hardness of the coating increased by the structural effect, the adhesion strength decreased with the Al concentration. The adhesion strength could be considerably increased by changing the Al concentration in the coating continuously, as the abrupt stress change at the interface between the coating and the substrate could be minimized.

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The oxidation behavior of Ti₃Al+(0, 0.6, 1.1, 1.9at%)Si alloys has been investigated in air at 700, 800, 900℃. The matrix of the plasma jet melted alloys had Ti₃Al with some TiAl. TiAl₃ and Ti_5Si₃. After oxidation, a multi-layered scale was formed on Ti₃Al+Si alloys as was frequently observed on pure Ti₃Al alloys, consisting of an outer TiO₂ layer, an intermediate relatively protective thin Al₂O₃ layer, and an inner TiO₂+Al₂O₃ mixed layer. The major effect of Si on Ti₃Al are considered to be; (1) increment of the oxidation resistance by being oxidized to amorphous SiO₂. (2) refinement of grains or densification of the outer TiO₂ layer by positioning between the TiO₂ grains, though the amount of SiO₂ in this area is extremely small. (3) enhancement of intermediate Al₂O₃ layer formation by decreasing Ti activity, and thereby, increasing Al activity owing to the formation of Ti_5Si₃ inside the matrix.

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The purposes of this research were to develop the magnetic thin films using for high frequency range and to establish the processing technique of a meander type micro-coil in order to produce the micro magnetic device(MMD) and analyze its electrical characteristics. As magnetic thin films, we used Fe_(78.8)Ta_(8.5)N_(12.7) films which had nano-crystalline structure produced by a DC magnetron reactive sputtering system, magnetic properties were like these : Bs=15∼16 kG. Hc=0.12∼0.17 Oe, μ`=2800∼4000. The Cu coil produced by selective electro-plating(SEP) showed the resistivity of 2 μΩ-㎝. In case of the meander type magnetic thin films inductor with 5 turns, an inductance of 229 nH which is about 4 times higher than that of air core inductor was shown, and a resonance frequency of 37 MHz and a quality factor of 1.8 at 10 MHz were also shown.

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The microstructural evolution of Cu films deposited by electroplating was investigated with the variation of the deposition rate from 0.1 ㎛/min to 3 ㎛/min by using a copper sulfate solution. Electrodeposition of copper was conducted on 0.1 ㎛ or 0.5 ㎛ thick copper seed layer deposited by sputtering process. The growth characteristics were investigated by monitoring the surface microstructure, electrical resistivity and chemical composition. The feasibility of electroplating process for ultra-large-scale integration(ULSI) metallization scheme was demonstrated through preferred crystallographic growth direction, resistivity and step coverage. The uniform Cu film was successfully electroplated at deposition rates from 0.5 to 3 ㎛/min and its continuous growth on the copper seed layer was observed in every specimen. The resistivity of as-deposited copper film made at deposition rates from 0.5 to 3 ㎛/min was about 2.5μΩ-㎝ and subsequent annealing in a vacuum at 200℃ for 2 min reduced it to 2.3μΩ-㎝.

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The dielectric layers for plasma panel display device were prepared from two series of glass-ceramics, namely, P₂O_5-ZnO-BaO and SiO₂-ZnO-B₂O₃ glass-ceramics containing filler. The nucleation and crystallization process of glassceramics for dielectric layer have been examined by differential thermal analysis, X-ray diffraction and light and electron microscopy. Optical, thermal and electrical properties of the dielectric layer were evaluated by means of spectrophotometer, dilatometer and LCR meter. From this research, it was found that these glass-ceramics are useful materials for dielectric layers in plasma panel display device, as those have a similar thermal expansion to soda-lime glass plate, high reflectance, low sintering temperature. Also the addition of Al₂O₃ and TiO₂ as fillers to these glass-ceramics is considered to be suitable for acquiring good properties of dielectric layer for PDP device.

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The change of growth rate with supercooling and growth time was investigated in the thick film growth of (TbBi)₃(FeAlGa)_5O_(12) garnet single crystal. At the degree of supercooling smaller than critical supercooling having maximum growth rate, growth rate was kept constant and the film composition did not change until the supersaturated garnet solute was depleted. After depletion the Bi concentration profile was decreased with the film thickness. At the degree of supercooling larger than critical supercooling, growth rate was decreased with growth time because of nucleation and growth of garnet microcrystals at the Pt crucilble wall. Bi concentration profile was decreased with the film thickness but concentration of Fe, Al, Ga was kept constant. The variation of Bi concentration with the film thickness is proportion to the film growth rate. It is found out that the interfacial supersaturation βi is decreased with growth time even though growth temperature is kept isothermally.

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This paper was focused to investigate the effect of bonding temperature on the microstructure of Ti/Al bond interface and the bonding strength. The bonding of Ti/Al with Al-10Si-1Mg(wt.%) filler metal has been conducted at the temperature range of 560∼640℃ for 30min under bonding pressure of 0.4MPa. The liquidus temperature of filler metal was 582℃. The intermetallic compounds, such as Ti_7Al_5Si_(12), Ti_9Al_(23) and Al₃Ti, are found to be formed in the Ti/Al interface at bonding temperatures above 600℃. Dominant phase in intermetallic compound layer is Ti_7Al_5Si_(12) at 600℃ and Ti_9Al_(23) at 640℃. The thickness of intermetallic compound layer was increased with increasing bonding temperature. It was considered that the growth of intermetallic compound layer had relevance to the transformation of dominant phase in intermetallic compound layer with bonding temperature; the intermetallic compound layer tend to grow by the diffusion of silicon to aluminium-base metal from Si rich phase(Ti_7Al_5Si_(12)). This result indicated that dominant phase was transformed Ti_7Al_5Si_(12) into Ti_9Al_(23) With increasing bonding temperature through diffusion of silicon. It was found that the maximum bonding strength was 92MPa at the temperature of 600℃.

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