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pISSN : 1225-1429 / eISSN : 2234-5078

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2005, Vol.15, No.5

  • 1.

    A study on the growth mechanism of rutile single crystal by skull melting method and conditionsof RF generator

    Choi Jong Keon | SEOK, JEONG-WON | 2005, 15(5) | pp.175~181 | number of Cited : 0
    Abstract PDF
    Ingots of rutile single crystals were grown by the skull melting method, and their characteristics were comparedin terms of melt-dwelling time for each melt. The method is based on direct inductive heating of an electrically conducted2 is an insulator at roomtemperature but its electric conductivity increases elevated temperature. Therefore, titanium metal ring(outside diameter : 6 cm,inside diameter : 4 cm, thickness : 0.2 cm) was embedded into TiO2 powder (anatase phase, CERAC, 3N) for initial RFinduction heating. Important factors of the skul melting method are electric resistivity of materials at their melting point,working frequency of RF generator and cold crucible size. In this study, electric resitivity of TiO2 (102~101 Ω· m) at itsthe cold crucible was 11 and 14 cm, respectively, which were determined by considering of the penetration depth(0.36~1.13 cm) and the frequency of RF generator.
  • 2.

    A study on the identification of ruby and garnet by optical method

    Choi Jong Keon | 황지호 | 2005, 15(5) | pp.182~187 | number of Cited : 0
    Abstract PDF
    The FT-IR absorption spectrum by the lattice vibrations of ruby and garnet obtained from FT-IR shows quitediferent characteristics. By the UV-VIS spectroscopy it was found that the ruby has two transmission bands in red andblue region, while garnet has only one transmission band in red region. The color filter to distinguish ruby from garnetwas developed and named HWANG JI HO filter. Through the HWANG JI HO filter, ruby was shown in blue color andas spinel, tourmaline were shown in dark red color like as garnet. The ruby could be recognized easily from the red stone.
  • 3.

    Crystal growth and pinning enhancement of directionally melt-textured (Y0.5Nd0.25Sm0.25)Ba2Cu3Oyoxides in air

    So-Jung Kim | 2005, 15(5) | pp.188~192 | number of Cited : 1
    Abstract PDF
    High Tc (Y0.5Nd0.25Sm0.25)Ba2Cu3Oy [(YNS)-123] superconductors with/without CeO2 additive were systematically investigated by the zone melt growth process in air. Cylindrical green rods of (YNS)-123 oxides were fabricated by cold isostatic pressing (CIP) method using rubber mould. A sample prepared by this method showed well-textured microstructure, and (Y0.5Nd0.25Sm0.25)2BaCuO5 [(YNS)211] nonsuperconducting inclusions were uniformly dispersed in large (Y0.5Nd0.25Sm0.25)Ba2Cu3Oy [(YNS)123] superconducting matrix. In this study, optimum melting temperature and growth rate were 1100oC and 3 mm/hr, respectively. The directionally melt-textured (YNS)-123 sample with CeO2 additive showed an onset critical temperature (Tc) Tc ≥ 93 K and sharp superconducting transition.
  • 4.

    Synthesis of CuO from organic-inorganic hybrid

    Young Duk Huh | 권석순 | 국원근 | 2005, 15(5) | pp.193~197 | number of Cited : 0
    Abstract PDF
    CuO has been synthesized using the layered organic-inorganic hybrids, Cu2(OH)3(CH3COO) · H2O as precursor.The simple thermal decomposition of Cu2(OH)3(CH3COO) · H2O is used without any external organic templates. Thisagregated particles is strongly dependent on structure of the precursor.
  • 5.

    Control the growth direction of carbon nanofibers under direct current bias voltage applied microwaveplasma enhanced chemical vapor deposition system

    Kim Sung-Hoon | 2005, 15(5) | pp.198~201 | number of Cited : 0
    Abstract PDF
    Carbon nanofibers were formed on silicon substrate which was applied by negative direct current (DC) bias voltage using microwave plasma-enhanced chemical vapor deposition method. Formation of carbon nanofibers were varied according to the variation of the applied bias voltage. At −250 V, we found that the growth direction of carbon nanofibers followed the applied direction of the bias voltage. Based on these results, we suggest one of the possible techniques to control the growth direction of the carbon nanofibers.
  • 6.

    Effects of viscosities of slip on slip casting and properties of sintered bodies of cordierite

    BAEKYONGHYEOK | PokKieChang | Kwak Hyo Sup | 2005, 15(5) | pp.202~207 | number of Cited : 0
    Abstract PDF
    We have investigated the relationship between a viscosity of the slip prepared from kaolin, quartz, Mg(OH)2, etc and its influence on the speed of slip casting and the microstructure of a sintered body. The speed of slip casting decreases as a viscosity of a slip decreases. The optimized viscosity range of a slip was found to be around 3.0~17.0 cP. By careful controlling a viscosity of slip, homogeneous icrostructure of outer surface layers, inner surface layers, intermediate layers, and inside layers were obtained by casting process. The specimen sintered at 1350 oC consists of a cordierite crystalline phase only as a constituent mineral.
  • 7.

    The mechanism of black core formation

    박지윤 | KIM, YOOTAEK | Lee,Ki-Gang and 2other persons | 2005, 15(5) | pp.208~215 | number of Cited : 12
    Abstract PDF
    The 10 m diameter aggregates made of clay, carbon and Fe2O3 were prepared to investigate the mechanism ofblack core formation. The specific gravity, absorption rate, percent of black core area, fracture strength, total Fe analysis,sintering methods. Small addition of Fe2O3 did not afect physical properties of the aggregates; however, the percent ofblack core area increased with increasing carbon contents and increasing sintering temperature. Specific gravity of theaggregates decreased and the water absorption ratio increased with increasing percent of black core area. The aggregatessintered at oxidation atmosphere showed clear border betwen shell and black core area. Hence, the agregates sintered atreduction atmosphere showed only black core area in the cross-section of the aggregates. The specific gravity of thecomparing other agregates sintered at diferent atmospheres. Adsorption rate increased with increasing carbon contents atal atmospheres. The fast sintered agregates showed lower specific gravity, higher absorption rate, and more black corearea than the normally sintered aggregates. It was turned out that the aggregates having more black core area showedhigher fracture strength than that of aggregates with no black core area. From the total Fe analysis, the concentration of Feand FeO was higher at black core area than at shel. Because the concentration of Fe2O3 in the shell was higher than othercore area.