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pISSN : 1225-1429 / eISSN : 2234-5078

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2015, Vol.25, No.3

  • 1.

    A study on SiC crystal growth by sublimation process using resistance heating method

    Kang, Seung-Min | 2015, 25(3) | pp.85~92 | number of Cited : 2
    Abstract PDF
    SiC crystals are well known for their true potential as high power devices and their crystal growth activity is actively carried out in domestic as well as in abroad. Until now the process to grow this crystal has been done by sublimation technique using radio frequency induction heating method. However in order to get better quality of SiC crystals, the stability of temperature is needed because SiC crystal tends to transform to other polytypes. So, the possibility of SiC crytals growth was evaluated by different heating method. This study aimed to observe whether the resistant heating method would show stable growth and better quality of SiC single crystal than that of RF induction heating. As a result, polycrystalline SiC crystals were grown by the growth rate of 0.02~0.5 mm/hr under the condition of 2100~2300oC at the bottom side of the crucible and 10~760 torr. The polycrystalline SiC crystals with 0.25 and 0.5 mm in thickness were grown successfully without seed and characterized by optical stereo microscopic observation.
  • 2.

    The synthesis of high purity micro Ag particle using the rapid firing -liquid phase precursor method

    임병석 | Song YoungHyun | 이민지 and 2other persons | 2015, 25(3) | pp.93~97 | number of Cited : 0
    Abstract PDF
    To synthesis of high purity micro silver particle, we extracted the silver from the waste by liquid-liquid extraction and used the rapid firing-liquid phase precursor (RF-LPP) method. The silver micro particle was synthesized at 500 o C for 3 hr in air atmosphere by RF-LPP method. As a result of the research, micro silver particle is measured X-ray diffraction (XRD), the main peak is nearly corresponded to the same as JCPDS card (No.87-0719). With using the RF-LPP method, the fine Ag micro particle indicated due to the control of nucleation site and the oxygen contents was decreased by reducing treatment. We expect this research contribute to advance in field of the recycling technology.
  • 3.

    Effect of surface-treatments on flexibility and guided bone regeneration of titanium barrier membrane

    김진태 | 김병수 | 정희석 and 5other persons | 2015, 25(3) | pp.98~104 | number of Cited : 3
    Abstract PDF
    Titanium barrier membranes are prepared to investigate the effect of surface-treatments, such as machining, electropolishing, anodizing, and electropolishing + TiN coating, on the biocompatibility and physical properties of the membranes. The surface roughness (Ra) of the membrane decreases from machining (0.37 ± 0.09 μm), TiN coating (0.22 ± 0.09 μm), electropolishing (0.20 ± 0.03 μm), to anodizing (0.15 ± 0.03 μm). The highest ductility (24.50 %) is observed for the electropolished Ti membrane. No evidence of causing cell lysis or toxicity is found for the membranes regardless of the surface-treatments. Cell adhesion results of L-929 and MG-63 show that the machined Ti membrane exhibits the highest cell adhesion while the electropolished membrane is the best membrane for the L-929 cell proliferation after 7 days. However, no appreciable difference in MG-63 cell proliferation among variously surface-treated membranes is detected, suggesting that the electropolished Ti membrane is likely to be the best membrane due to the synergic combination of tailored flexibility and excellent fibroblast proliferation.
  • 4.

    Preparation and properties of glass fiber-reinforced endodontic (root canal therapy) posts

    손재용 | KIM,KYUNGJA | 김경훈 and 2other persons | 2015, 25(3) | pp.105~110 | number of Cited : 0
    Abstract PDF
    The fiber-reinforced endodontic posts were prepared using a photocurable resin and a glass fiber. The mechanical property of the posts increased with increasing density of glass fiber and the micro-pores in the post were removed by a vacuum impregnation process. To improve the interfacial adhesion between glass fiber and polymer, silane coupling agent was used. The surface treatment of glass fiber increased the surface wettability of resing on glass fiber and increased the adhesion property with resin, consequently improved the mechanical property of posts.
  • 5.

    Core region and optical properties of Er 3+ doped Y3Al5O12 single crystals

    심장보 | 이영진 | 강진기 and 1other persons | 2015, 25(3) | pp.111~115 | number of Cited : 1
    Abstract PDF
    Er 3+ doped Y3Al5O12 (Er : YAG) single crystals, in which the concentrations of Er 3+ ion were 5, 7.3, 8, and 10 at.%, were grown by the Czochralski method under nitrogen atmosphere. The <111> oriented Er : YAG single crystals with diameters of up to 50 mm were grown at a pulling rate of 1.0 mm/h and rotation rate of 10 rpm. The thick part of the core region was generated mainly when there was a diameter change during the crystal growth. The concentrations of Er 3+ ion in the crystals were the same as it was in the melt. Er 3+ concentration of core region was slightly higher than the other regions in the compositional analysis. The fluorescence lifetime was saturated according to the increase of Er 3+ doping concentrations.
  • 6.

    Structural and electrochemical characterization of K2NiF4 type layered perovskite as cathode for SOFCs

    Jaeha Myung | Younwoo Hong | LEE MI JAI and 5other persons | 2015, 25(3) | pp.116~120 | number of Cited : 0
    Abstract PDF
    La2NiO4 + δ based oxides, a mixed electronic-ionic conductors (MIECs) with K2NiF4 type structure, have been considerably investigated in recent decades as electrode materials for advanced solid oxide fuel cells (SOFCs) due to their high electrical conductivity, and oxidation reduction reaction (ORR). In this study, structure properties of La(Ca)2Ni(Cu)O4 + δ were studied as a potential cathode for intermediate temperature SOFCs (IT-SOFCs).
  • 7.

    Synthesis of Lu2.94Ce0.06MgAl3SiO12 phosphor and its photoluminescent properties

    Lee, Jung-il | 김태완 | 신지영 and 1other persons | 2015, 25(3) | pp.121~126 | number of Cited : 1
    Abstract PDF
    A novel Ce3+ doped Lu3MgAl3SiO12 phosphor (Lu2.94Ce0.06MgAl3SiO12) was successfully synthesized by a conventional solid-state reaction at 1450oC for 5 h. The crystal structure of the synthesized phosphor powder was characterized by X-ray diffraction and Rietveld refinement. The prepared phosphor powder showed a broad peak at 550 nm, and the temperature dependence on photoluminescence properties of the prepared Lu2.94Ce0.06MgAl3SiO12 phosphor was investigated from 300 to 525 K. The activation energy for thermal quenching was determined by Arrhenius fitting. The experimental results clearly indicate that prepared Lu2.94Ce0.06MgAl3SiO12 phosphor has great potential for a down-conversion yellow phosphor in white light-emitting diodes.