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Influence of solder alloy composition on the wettabiliy and the shear stress of the solder joint was investigated. Also, the effect of the growth of the intermetallic compounds on the shear stress of Sn-Bi and Sn-Pb solder joints was investigated. Sn-Bi and Sn-Pb alloys were electroplated on a Cu plate from methane sulfonate bath and then reflowed at 250℃. The wetting angle of Sn-Bi solder was increased with increasing Sn content in the solder due to increase in the surface energy. Two Cu plates electrodeposited with Sn-Bi and Sn-Pb were clamped each other and soldered at 220℃ to produce solder joints. The solder joints were pulled to failure at strain rate from 3.3×10 exp (-4) to 3.3×10 exp (-2) / s to measure the shear strength of the solder joints. At low strain rate, the shear strength of the Sn-Bi solder joint decreased with increasing Sri content in the solder, but at high strain rate, the shear strength increased due to the brittleness of Bi. The shear strength of the 80Sn-2OPb solder joint was higher than that of the 60Sn-4OPb solder joint at all strain rate. The shear strength of the 42Sn-58Bi solder joint was higher than that of the 8OSn-2OPb at low strain rate, but lower at high strain rate. The shear strength was increased with increasing aging time until 24 hours because the rough surface of the intermetallic compounds acted as wedge at the intermetallic compound/solder interface. After 24 hours, the increase in thickness of the brittle intermetallic compound layer decreased the shear strength of the 42Sn-58Bi solder joint.

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(Bi_(1-x)Sb_x)_2Te_3 thermoelectric thin films were prepared by DC magnetron sputtering process, and their thermoelectric characteristics were investigated with the Sb_2Te_3 content and annealing process in hydrogen atmosphere. With annealing in hydrogen atmosphere, the compositions of (Bi(1-x)Sb_x)_2Te_3 thin films were changed to be Bi-surplus and Te-deficient. Seebeck coefficient and electrical resistivity of (Bi(1-x)Sb_x)_2Te_3 thin films decreased with annealing due to increase of hole concentration. Power factor of (Bi(1-x)Sb_x)_2Te_3 films increased with increasing the Sb_2Te_3 content, and was improved about two times with annealing in hydrogen atmosphere. As-annealed (Bi_0.15Sb_0.85)_2Te_3 film exhibited a maximum power factor of 0.64×10 exp (-3) W/K^2 -m.

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The effect of irradiation damage on FZ silicon crystal properties has been studied by electrical measurements. 4 FZ silicon wafers of high resistivity of 1000∼2000Ω-㎝ with (100) orientation were irradiated with thermal neutron fluences of 1.815E18/㎠ and 6.406E18/㎠ by HANARO nuclear reactor to compare resistivity, point defect due to fluence differences. SRP results showed that the obtained resistivities approached to the designed ones. Point defect generation due to irradiation was observed using FTIR and DLTS. In the case of Si-1, two point defects were observed at 100 K and 230 K and they were named E_l and E_2. The sample of Si-2 had four point defects which were included two point defects of Si-1 sample. The two point defects of Si-2 were measured at 125K(E_4) and 300K(E_3). The point defects which were E_2 and E_3 were first observed in this study.

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A kinetic study of nitrogen dissolution in STS304 stainless steel melt containing Ti and Nb has been carried out at 1500℃ using an induction furnace and a levitation melting furnace. At low O and S levels, the nitrogen dissolution rate showed the first-order kinetics being controlled by the mass transfer of nitrogen in the melt. Ti addition to STS304 stainless melt significantly retarded the nitrogen dissolution rate by the formation of solid Ti oxide layer adhered on the melt surface. Nb did not affect the rate of nitrogen dissolution. In the levitation melting experiment where the oxide layer was removed from the melt surface, Ti did not retard the nitrogen dissolution rate. Simultaneous addition of Ti and Al increased the dissolution rate by the formation of non-wetting A1_20_3 on the melt surface. A small addition of CaO-Al_2O_3 synthetic flux to Ti containing melt was very effective to remove the oxide layer, hence to increase the nitrogen dissolution rate.

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Solidification contraction during crystallization of molten mold fluxes has been observed in a laboratory scale mold. Mold fluxes with larger contraction show smaller mold heat flux in thin slab caster. This implies that thermal resistance at mold/mold flux interface arises from the solidification and crystallization of the flux film. Also, the effect of chemical composition on the solidification contraction has been clarified using synthetic mold fluxes of 1.25∼1.45 basicity, 8∼12 mass % Na_2O, 7∼11 mass % F, 2∼6 mass % Al_2O_3, 1.5∼4.5 mass % MgO. Larger basicity and Na_2O/F ratio yield larger contraction. Especially, mold flux of 12% Na_2O and 7% F shows larger contraction than that of 8% Na_2O and 11% F. Microphotograph analysis shows that the crystallization of sodium fluoride dicalcium silicate (NaF.2CaO.SiO_2) is the main reason for the increase of solidification contraction.

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