SiC whisker reinforced Al2O3-SiC composite was fabricated by reaction synthesis method whish is cost ef-fective and allows good dispersion of whiskers. Fracture strength at room temperature showed the highest value with 150 reaction temperature because a lot of SiC whiskers was formed. Fracture strength at 135 did not show big differences with reaction temperature due to agglomeration of whiskers and formation of sil-icon oxynitride during hot MO(modulus of rupture) test probably promoting grain boundary sliding.

Mullitization in a multicomponent oxide system(alumina-kaolin-quartz-feldspar-talc) was studied as a function of sintering temperature from 1200 to 1500 based upon a quantitative X-ray diffraction analysis. In the present study mullite grew as wiskers and its formation reaction showed characteristic there stages as follows In the first stage(1255-1295) an appreciable mullitization(nucleation) occurred while corun-dum dissolution into glass (increasing glass content ) limited the rate of the reaction. At 1295-1335 (second state) the reaction was significantly enhanced with a considerable glass consumption and with no appreciable change in corundum content. Finally (above 1335) the reaction rate was attenuated re-markably with an apparent decrease in glass consumption rate. The impingement of mullite whiskers by oth-er whiskers and crystals was speculated to cause mullite growth in thickness direction with a slow growth rate resulting in the diminished reaction rate in the final stage.

thin films have been prepared on borosilicate glass substrate using alkoxide method to characterize the effects of fabricating factors on thermochromic performance. The gel films formed by spin coating were converted to phase during oxidizing heat-tratment and the phase were formed by reducing heat-treatement. The thermochromic switching properties of thin films are strongly affected by the crystal phase and microstructure and those could be controlled by reducing heat-treatment conditions. The ther-mochromic switching characteristics of thin films synthesized were measured at IR (2.5) as the transition temperature of the transition width of and the maximum and minimum transmittance of 84% and 14% respectively.

B-doped ZnO thin films on glass substrates were prepared by sputtering the ceramic targets which had been prepared by sintering disks consisting of ZnO and various amounts of B2O3 While pure ZnO films show-ed a c-axis oriented growth the B-doping retarded the prefered orientation and grain growth of the film. Electron concentrations for undoped and B-doped ZnO films were on the order of 7.81018 cm-3 and 5{{{{ {10 }^{20 } }} c{{{{ {m }^{-3 } }} respectively. The electron mobility however decreased with the B-doping concentration. Optical meas-urements on the films showed that the average transmittance in the visible range was higher than 85% The measurements also indicated a blueshift of the absorption edge with doping.

Al2O3/Al composites were produced by immersing the sintered silica preform in molten aluminum which contained magnesium as impurity. Three distinct regions existed in the penetration behavior of molten me-tal with changing the reaction temperature. These regions are denoted as low temperature regime(75-85) intermediate regime(90-95) and high temperature regime(100) In the low temperature regime the penetration speed of molten aluminum increased with increasing reaction temperature whereas it decreased in the intermediate regime due to the phase transition of alumina formed by displacement reac-tion. In the high temperature regime the penetration speed of molten aluminum was the highest at 100 which was 3.6 mm/hr But above 105 molten aluminum did not penetrate into the silica preform because of the formation of a dense spinel layer at the preform surface by magnesium in molten Al

A MgO-CaO-based coating material for ferrous melt refining is applied to the tundish operation for mol-ten steel having low carbon. The changes in the total oxygen content insoluble aluminum content and the content of inclusions in molten steel during tundish operation were measured at the pouring part strand of tundish and mold. On the basis of the experimental results the interfacial reaction occurring between the coating materials and the molten steel in tundish was discussed and compared with the theoretical con-sideration. It is concluded that interfacial reaction is not active at the strand part of tundish but is active at the pouring part because of the turbulent flow in the molten steel.

Cutting and planarization of diamond films have been performed using copper vapor laser under air at-mosphere. Diamond films of about 350 and 800 thick have been synthesized with DC plasma assisted chemical vapor deposition. The position of a specimen has been controlled by computer-driven stage. With copper vapor laser beam of 7W cutting depth increases rapidly and saturates with increasing scan number and decreasing scan speed. 8 repetitive scans at scan speed 0.5 mm/sec produce the maximum cutting depth without focus shifting Rod-shape copper vapor laser beam can be made and used effectively in planar-ization of rough diamond surface.

The effect of coating thickness on the contact fracture was studied, in Si3N4 coated Si3N4-BN system When the elastic/plastic mismatch is relatively large betwen two layers in bilayer certain critical coating thickness was required to prevent cone crack initiation and this critical thickness was decreased by de-creasing the elastic/plastic mismatch,. In addition the required critical thickness should be increased when higher loads apply. In conclusion an appropriate coating thickness should be designed by elastic/plastic mismatch between two layers and environment (applied load) to prevent the coating fracture,

The oxidation behavior of Ag-36.8a%Cu-7.4at%Ti alloy brazed on Si3N4 substrate was investigated at 400, 500 and 600 in air. Under this experimental condition Si3N4 and Ag were not oxidized whereas Cu and Ti among the brazing alloy components were oxidizied obeying the parabolic oxidation rate law. The activation energy of oxidation was found to be 80kj/ mol which was smaller than that of pure Cu owing to the presence of oxygen active element of Ti. The outer oxide scale formed from the initial oxidation state was always composed of Cu oxides which were known to be growing by the outward diffusion of Cu ions. As the oxidation progressed the concentration gradient occurred due to the continuous consumption of Cu as Cu oxides and consequently build-up of an Ag-enriched layer below the Cu oxides resulted in the formation of multiple oxide scales composed of Cu oxide (CuO) /Ag-enriched layer/Cu oxide (Cu2O) /Ag-enriched layer. Also the inward diffusing of oxygen through Cu oxide and Ag-enriched layers led to the formation of internal oxides of TiO2

the microstructure and mechanical properties of seeded and ball-milled dry gels prepared by boehmite sol-gel method were discussed. The densification of seeded gels was improved with increasing seed content namely the number of seed The number of seed was 1.09, 3.35, 5.721012/cm3 boehmite when seeded with 1, 3, 5wt% respectively The ball milled gel contained about 0.5wt% seed and the number of seed was 4.721012/cm3 boehmite. The sintered density of 5wt% seeded gel was below 80% when sintered at 1300 for 1h. On the other hand that of ball milled gel was very improved and reached to 97% In the case of 3wt% seeded gels the density over 97% was attained when sintered at 1500for 1h. and the grain of the sintered body was several micrometers in size. However the sintered body of ball milled gel showed grain size of submicrometer when sintered at 1300 for 1h. And this specimen showed highest harness value of 1900kg/mm2 The fracture toughness increased with increasing sintering temperature. The sintered body of ball milled gel showed the largest grain size and the highest fracture toughness without regard to sint-ering temperature.

Melt spun YbBa2Cu3Agx(x=0, 5, 12, 16 and 53) precursor alloy ribbons were oxidized at 263-330 and treated at 820, 855 and 885 under 1.0 atm oxygen pressure. In the ribbons treated at 820, 855and 885 1-2-4 phase (YbBa2Cu4O8) and 1-2-3 phase (YbBa2Cu3O{{{{ OMICRON _7- }})were formed respectively. The shape of 1-2-4 phase was distorted or ellipsoid. The 2-4-7 and 1-2-3 phases tooked the shape of bar. All the ribbons showed zero critical current density Jc at 77K in zero magnetic field. By considering the shape and the highest critical temperature (among the three phases) of the 1-2-3 phase we tried to increase the critical current density of the ribbons treated at 885 by press deformation. About tenribbons were stacked and coupled by press deformation and then treated at 885 These 1-2-3 phase did not show any texture in any of the ribbons. However they exhibited weak texture in the multilayered specimens. Among the multilayered specimens YbBa2Cu3Ag16 exhibited a Jc of 180 A/cm2 Among the above ribbons YbBa2Cu3Ag16 ribbon has the optimum composition to produce textured superconducting oxide with improved Jc by press deformation. Onset critical temperatures Ton of the multilayered YbBa2Cu3Agx(x=5, 12, 16 and 53) were measured as 88-90 K.

The structural and electrical properties of titanium dioxide(TiO2) thin films deposited on p-type (100) si and 4off(100) Si substartes by metalorganic chemical vapor deposition (MOCVD) have been studied with post rapid thermal annealing. TiO2 thin films of anatase phase were grown at 300-500 using titanium post rapid thermal annealing at a temperature of 800 for 30sec. rutile phase was observed in the condition of the deposition temperature over 350 in the ambient air atmosphere and at 500 in cacuu,. SEM and AFM study show-ed surface roughness were increased slightly from 40to 55 after annealing due to grain growth and phase transformation. From capacitane-voltage measurement of Al/TiO2./p-Si structure after annealing we obtained ideal capacitance-voltage characteristics of MOS structure with dielectric constant of 16-22 in case of (100) Si and about 30- in case of 4off(100) Si but showed the higher leakage current.

20mol% Gd-doped CeO2 ultrafine powders as a promising electrolyte for the low temperature solid ox-ide fuel cells were synthesized with particle sizes of 15-20 nm using glycine nitrate process(GNP) fol-lowed by sintering their pellets at 150 for various times in air and then the electrical properties of the sintered pellets were investigated. The sintering behaviors and electrical properties for the sintered 20 sintered mol% Gd-doped CeO2 pellets were analyzed using dilatometer and SEM and AC two-terminal impedance technique respectively. As the heating temperature increased the synthesized powder had the sintering behaviors to show the start of the significant shrink at temperature of about and to show the end of the shrink at the temperature of about 147. When the pellets were sintered with the vaious times at 150 the temperatuer which the shrink had been already completed the grain sizes in the sintered 20 mol% Gd-doped GeO2 pellets increased with the increase of the sintering time but their electrical resis-tivities showed the minimum value at the sintering time of 10h. It is due that the pellet sintered for 10h had the minimum activation energy fior the electtrical conduction. Thus it is thought that the decrease of the activation energy with the increase of the sintering time to 10h is induced by the enhanced mi-crostructure like the decrease of pore amount and the grain growth and its increase with the sintering times more than 10h is induced by the increase of the amounts of the impurities such as Mg. Al and Si from the sintering atmosphere.