• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.584-584
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• 2000

Electronic structures of ordered Fe$_3X (X = Al, Si), and their derivative ternary alloys of Fe_2TX (T = 3d transition metal) have been investigated by using the linearized muffin-tin orbital (LMTO) band method. The role of the coupling between substituted transition metal and its neighbors is investigated by calculating the magnetic moments and local density of states (LDOS). It is shown that it is essential to include the coupling beyond nearest neighbors in obtaining the magnetic moment of Fe alloy. The preferential sites of T impurities in Fe_3X are determined from the total energy calculations. The derivative ternary alloys of Fe_2TX have characteristic electronic structures of semi-metal for Fe_2VAI and (nearly) half-metal for Fe_2TAI (T = Cr, Mn) and Fe_2TSi (T = V, Cr, Mn)

• Journal of the Korean earth science society
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• v.25 no.1
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• pp.48-51
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• 2004

The light element candidates such as S, O, Si, and K are discussed for the reasonable compositions in the earth's core since the available data show density difference from pure iron core. These candidates are favored by the some evidences such as depletion in the crust and mantle, and lower eutectic temperature of Fe-FeS melt for sulfur. FeO phase for oxygen, lighter mass than sulfur and solubility in metallic phases for silicon, and partitioning in Fe-FeS melt for potassium. However, other problems such as short experimental data, initial compositions of these elements, and oxidation state during the formation of the earth should be solved simultaneously to confirm these light elements.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.406-409
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• 2001

The conductivity properties and synthesis of LaNiO$_3$ ceramics from La$\sub$1+$\delta$/NiO$_3$($\delta$=--0.06, 0, 0.06) were investigated. A single perovskite phase was realized at 800$^{\circ}C$. La$_2$NiO$_4$ and other unexpected oxide were observed at 1000$^{\circ}C$. The Microstructure was showed clearly that it is a low density porous material. LaNiO$_3$ ceramic showed a metallic conductivity. The conductivity of La rich samples had a higher value than the La poor samples.

• Journal of Korea Foundry Society
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• v.22 no.2
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• pp.82-88
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• 2002

Al-5.5Zn-2.5Mg-l.5Cu semi-solid slurry was prepared by cooling the liquid metal with a low superheat to a solid and liquid co-existing temperature. Relatively round solid particles could be obtained in the slurry through the simple process. The prepared slurry was deformed into the metallic mold by a press and the mechanical properties of obtained specimens were investigated. Mold filling ability of the alloy slurry was also investigated and compared with that of A356 alloy. Al-Zn-Mg-Cu alloy showed lower mold filling ability than A356 alloy probably because small amount of eutectic phase is present and the heat of fusion generated during solidification is smaller than that of A356 alloy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.47-47
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• 2007

Indium oxide conducting films were dep9sited on Si(100) substrates at various temperatures by liquid delivery metal organic chemical vapor deposition using Indium (III) tris (2,2,6,6-tetramethyl-3.5-heptanedionato) $(dpm)_3$ precursors. The films deposited at $200{\sim}400^{\circ}C$ were grown with a (111) preferred orientation and exhibit an increase of grain size from 21 to 33nm with increasing deposition temperature. In the range of deposition temperature, there is no metallic indium phase in deposited films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.3
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• pp.256-260
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• 2011

ZnO nanostructures with tetrapod, needle and multipod shapes were synthesized without catalysts through a simple thermal oxidation of metallic Zn powder in alumina crucible under air atmosphere. X-ray diffraction data revealed that the ZnO nanostructures had wurtzite structure of hexagonal phase. Energy dispersive X-ray (EDX) spectra showed that the ZnO was of high purity. After the oxidation of Zn powder, white colored product was mainly observed and yellow colored product was observed only a very little on the surface of the oxidized source materials. The white product consisted of tetrapods, while yellow product was composed of needles and multipods. Cathodoluminescece spectra showed that the crystalline quality of tetrapods was better that those of needles and multipods.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.157-157
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• 2010

Programmable Metallization Cell (PMC) is a memory device based on the electrolytical characteristic of chalcogenide materials. PMC components of Ge-Se doped with Ag ions were studied with help of the previous studies and copper was used for metallic ions taking into account of economy of components. In this study, we investigated the nature of thin films formed by photo doping of Cu ions into chalcogenide materials for use in solid electrolyte of programmable metallization cell devices. We were able to do more economical approach by using copper which play role of electrolyte ions. The results imply that a Cu-rich phase separates owing to the reaction of Cu with free atoms from chalcogenide materials.

• Journal of Welding and Joining
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• v.7 no.2
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• pp.12-24
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• 1989

천이액상확산접합법은 접합계면에 일시적으로 액상이 형성되기 때문에, 고상확산접합법과 비교 하여 비교적 쉽게 금속결합을 이룰 수 있을 뿐만 아니라, 정밀하게 표면을 가공할 필요가 없으 며, 접합압력이 거의 필요 없다는 것이 잇점이라고 할 수 있다. 도한, 접합온도에서 등온응고되 기 때문에, 브레이징법과 비교하여 접합계면에 취약한 금속간화합물(Metallic Compound)이 생 성되지 않으므로, 기계적성질 및 내식성이 우수한 접합이음부를 얻을 수 있다는 잇점이 있다. 따라서, 본 접합법은 원리적으로 모재(Base Metal)와 거의 같은 정도의 물리적, 화학적, 기계적 성질을 갖는 접합이음부(Joint or Bonded Interlayer)를 얻을 수 있는 접합법이라고 생각되어진 다. 본 해설에서는 천이액상확산접합법의 기본원리, 접합기구, 접합인자 및 실용된 예에 대해서 서술하고자 한다.

• Bulletin of the Korean Chemical Society
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• v.20 no.8
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• pp.893-896
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• 1999

Novel citric acid based Ti, Nb and Ta precursors that are highly stable in the presence of water were developed. No alkoxides of Ti, Nb and Ta were utilized in the preparation, instead much less moisture-sensitive metallic Ti, NbCl5 and TaCl5 were chosen as starting chemicals for Ti, Nb and Ta, respectively. The feasibility of these chemicals as precursors is demonstrated in the powder synthesis of BaTi4O9, Y3NbO7 and LiTaO3. The water-resistant Ti precursor was employed as a new source of water-soluble Ti in the amorphous citrate method, and phase pure BaTi4O9 in powdered form was successfully synthesized at 800 ？. The Pechini-type polymerizable complex method using the water-resistant Nb and Ta precursors was applied to the synthesis of Y3NbO7 and LiTaO3, and both the powder materials in their pure form were successfully synthesized at reduced tempera-tures, viz. 500-700 ？. The remarkable retardation of hydrolysis of these water-resistant precursors is explained in terms of the partial charge model theory.

• Bulletin of the Korean Chemical Society
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• v.16 no.10
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• pp.929-933
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• 1995

The electronic band structure and electrical properties of KMo4O6 containing chains of condensed molybdenum octahedra are analyzed by means of the extended Hu&ckel tight-binding method. KMo4O6 has partially filled bands of 1D as well as 3D character. They also exhibit the anisotropic band dispersions with bandwidths much larger along the c* axis than along the directions perpendicular to it. Thus, conduction electrons are essentially delocalized along the c* direction (i.e., the chain of condensed molybdenum octahedra) in the solid. The 1D band of two partially filled d-block bands leads to Fermi surface nesting with the wave vector q=0.3c*. The CDW instability due to this nesting is expected to cause the phase transition associated with the resistivity anomaly at low temperature. The characteristics of metallic behavior in the crystallographic ab plane are explained on the basis of the unnested 2D Fermi surfaces.