Korean | English

pISSN : 1225-1429 / eISSN : 2234-5078

2020 KCI Impact Factor : 0.17
Home > Explore Content > All Issues > Article List

2008, Vol.18, No.1

  • 1.

    Growth of GdVO4 composite single-crystal rods by the double-die edge-defined film-fed growth technique

    Y. Furukawa | M. Matsukura | O. Nakamura and 1other persons | 2008, 18(1) | pp.1~4 | number of Cited : 0
    Abstract PDF
    The growth of composite-structured Nd : GdVO4 single crystal rods by the double die EFG method is reported. Two crucibles are combined with an outer and inner die for ascending of different melt. The composite-structured Nd : GdVO4 single crystal rods with a length of 50 mm and an outer diameter of 5 mm including of inner Nd-doped core region with diameter 3 mm were grown successfully. Nd distribution in the radial direction has graded profile from result of EPMA. Absorption coefficient in the core region at 808 nm was 42 cm−1 . Finally, we demonstrated the laser oscillation using our composite crystal and 2-W output was obtained.
  • 2.

    Fabrication and characteristics of porous ceramics from ZrTiO₄based ceramic material

    허근 | Kwang Bo Shim | 명성재 and 4other persons | 2008, 18(1) | pp.5~9 | number of Cited : 0
    Abstract PDF
    Cordierite has a very low thermal expansion coefficient, but has problem that it has a weak mechanical strength and is apt to be attacked by acid such as sulfur for using as a diesel particulate filter support. The physical properties of ZrTiO₄modified with SiO₂, Al₂O₃, MoOx, Cr₂O₃ and Nb₂O5 were investigated with XRD, SEM, UTM and thermal expansion, etc. in this paper. ZrTiO₄powder was synthesized as a monoclinic structure with processes that starting materials of TiO₂ and ZrO₂were mixed with ball mill and calcined above 1240℃ for 3 hr. Additive modified ZrTiO₄specimens for flexural strength and thermal expansion measurement were obtained by mixing ZrTiO₄ powder with additives, pressing and firing at 1300℃ for 3 hr. The porosity of additive modified ZrTiO₄decreased monotonically with increasing additive content by 5 wt% regardless of additive types and saturated for further increase of additive by 10wt. The flexural strength of Al2O3 (5, 10 wt%) modified ZrTiO₄shows a large increase, but that of other additives modified ZrTiO₄decreased. The thermal expansion coefficient of additive modified ZrTiO4 except Nb₂O5 decreased continuously with the content of additive. In particular, the lowest thermal expansion coefficient of ZrTiO₄was obtained for the additive of SiO₂.
  • 3.

    Distance between source and substrate and growth mode control in GaN nanowires synthesis

    신동익 | Yoon Dae Ho | Hojune Lee and 1other persons | 2008, 18(1) | pp.10~14 | number of Cited : 0
    Abstract PDF
    We synthesized GaN nanowires with high quality using the vapor phase epitaxy technique. The GaN nanowires were obtained at a temperature of 950℃. The Ar and NH3 flow rates were 1000 sccm and 50 sccm, respectively. The shape of the GaN nanowires was confirmed through FESEM analysis. We were able to conclude that the GaN nanowires synthesized via vapor-solid (VS) mechanism when the source was closed to the substrate. On the other side, the VS mechanism changed to vapor-liquid-solid (VLS) as the source and the substrate became more distant. Therefore, we can suggest that the large amount of Ga source from initial growth interrupt the role of catalyst on the substrate.
  • 4.

    Effect of carbon and boron addition on sintering behavior and mechanical properties of hot-pressed SiC

    안종필 | HyungSun Kim | 채재홍 and 3other persons | 2008, 18(1) | pp.15~21 | number of Cited : 1
    Abstract PDF
    SiC has an excellent resistance to oxidation and corrosion, high temperature strength and good thermal conductivity. However, it is difficult to densify because of its highly covalent bonding characteristics. Hot-press sintering process was applied to fabricate fully densified SiC ceramics with carbon and boron addition as a sintering additive. The addition of carbon improved the mechanical properties of SiC because it could induce a fine and homogeneous microstructure by the suppression of abnormal growth of SiC grain. Also, the addition of carbon could control the phase transformation of SiC. The phase transformation of 6H to 4H increased with sintering temperature but the addition of carbon decreased that kind of phase transformation.
  • 5.

    A study on the luminescence characterization of red long persistent phosphors by the B₂O₃ addition

    황구현 | Choi Jong Keon | 2008, 18(1) | pp.22~26 | number of Cited : 2
    Abstract PDF
    Red long persistent phosphors of CaZrO₃: Pr was synthesized by a solid reaction method. CaCO₃ and ZrO₂wereused as hosting materials and Pr was doped as luminescence center element, and B₂O₃was used as flux. The XRD patternand 590~700 nm. Phosphor samples were synthesized with B₂O₃flux concentration of 1, 5, 10 %, and luminescent peak ofmaximum intensity at 494 nm was obtained for 1 % B₂O₃. Luminescent peak of red color at 620 nm was of highestintensity for 10 % B₂O₃.
  • 6.

    Synthesis and luminescent properties of Er³+ doped CaZrO₃long persistent phosphors

    박병석 | Choi Jong Keon | 2008, 18(1) | pp.27~32 | number of Cited : 2
    Abstract PDF
    Novel long persistent phosphors of CaZrO₃:Er³+ have been synthesized by traditional solid state reaction method.The long persistent phosphor crystaline particles were characterized by the X-ray difraction (XRD), photoluminescencespectrophotometer, thermoluminescence (TL) and luminance meter. The results reveal that the samples are composed ofsingle CaZrO₃ phase. The broadband emission spectra of 446 nm peak and 550 nm peak was revealed by synthesized athigh temperature in N2 gas. Gren long persistent phosphors have been observed in the system for over 6 h after UViradiation (254 nm). The main emission peak was ascribed to Er³+ ions transition from 5D5/2→4F9/2, 2H12/2, 4S3/2→4I13/2 and2G9/2→4I13/2, and the afterglow may be ascribed to the suitable trap centers in the CaZrO₃ host lattice.
  • 7.

    The effect of Cu and Sb on the microstructure and mechanical properties in Sn-Sb-Cu-Ni-Cd whitemetal

    Jin-Kon Kim | Cho, Hyun | Sang Hie Sun and 3other persons | 2008, 18(1) | pp.33~37 | number of Cited : 0
    Abstract PDF
    The effects of Cu and Sb on the microstructure and mechanical properties of Sn-Sb-Cu-Ni-Cd whitemetal were investigated. Any compound phase was not observed in the whitemetal with 0.05 wt% Cu, while as the Cu content was increased, star- or needle-like Cu6Sn5 phases were found. The tensile strength gradually increased with Cu up to 5 % and then remained almost constant with Cu content above 5 %, while the hardness continuously increased with Cu content because of the increased hard Cu6Sn5 phases. As the Sb content increased, SbSn cuboids were present as well as Cu6Sn5. The tensile strength and hardness continuously increased and the elongation decreased with Sb content.
  • 8.

    Synthesis of zeolite MFI films on alumina and silicon supports using seed crystals

    Koh Tae Seok | 2008, 18(1) | pp.38~44 | number of Cited : 0
    Abstract PDF
    Contiuous c-oriented zeolite MFI films (< 35 μm) were prepared by hydrothermal secondary growth of silicalite- 1 seed crystal in the surface of alumina porous substrate and silicon substrate. The supported films were characterized with scanning electron microscopy and X-ray diffraction. Effect of substrate surface roughness were investigated and a mechanism for c-oriented film formation and characteristic dom-like defects formation which is observed after seeding growth was discussed. The roughness of substrate plays an important role.
  • 9.

    Simulation by heat transfer of ADS process for large sized polycrystalline silicon ingot growth

    서중원 | Sang-Jin Moon | Jung-Hoon Hwang and 3other persons | 2008, 18(1) | pp.45~49 | number of Cited : 2
    Abstract PDF
    The development of manufacturing process of silicon (Si) ingots is one of the important issues to the growth of the photovoltaic industry. Polycrystalline Si wafers shares more than 60 % of the photovoltaic market due to its cost advantage compared to monocrystalline silicon wafers. Several solidification processes have been developed by industry including casting, heat exchange method (HEM) and electromagnetic casting. In this paper, the advanced directional solidification (ADS) method is used to growth of large sized polycrystalline Si ingot. This method has the advantages of the small heat loss, short cycle time and efficient directional solidification. The numerical simulation of the process is applied using a fluid dynamics model to simulate the temperature distribution. The results of simulations are confirmed efficient directional solidification to the growth of large sized polycrystalline Si ingot above 240 kg.
  • 10.

    Characteristics of Al-doped ZnO thin films prepared by sol-gel method

    김용남 | 이승수 | 송준광 and 3other persons | 2008, 18(1) | pp.50~55 | number of Cited : 0
    Abstract PDF
    Al-doped ZnO(AZO) thin films have been fabricated on glass substrate by sol-gel method, and the effect of Al precursors and post-annealing temperature on the characteristics of AZO thin films was investigated. The sol was prepared with zinc acetate, EtOH, MEA and Al recursors. In order to dope Al in ZnO, two types of aluminum nitrate and aluminum chloride were used as Al precursor. Zinc concentration was 0.5 mol/l and the content of Al precursor was 1 at% of Zn in the sol. The sol was spin-coated on glass substrate, and the coated films were annealed at 550℃ for 2 h and were post-annealed at temperature ranges of 300~500℃ for 2 h in reducing atmosphere (N₂/H₂ = 9/1). Structural, electrical and optical propertis of the fabricated AZO thin films were analyzed by XRD, FE-SEM, AFM, hall effect measurement system and UV-visible spectroscopy. Optical and electrical properties of AZO thin films prepared with aluminum nitrate as Al precursor were better than those of films prepared with aluminum chloride. The electrical resistivity and the optical transmittance of films decreased with increasing post-annealing temperatures. The minimum electrical resistivity of 2 × 10−3 Ω·cm and the maximum