Korean | English

pISSN : 1225-1429 / eISSN : 2234-5078

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

2007, Vol.17, No.4

  • 1.

    Morphology-controlled synthesis of BaWO4 crystals using bidentate ligands

    Young Duk Huh | 유은경 | 2007, 17(4) | pp.139~144 | number of Cited : 0
    Abstract PDF
    BaWO4 crystals were synthesized using bidentate ligands. The reaction parameters such as the concentration ofligand and molar ratio of [WO42]/[Ba2+] played important roles in the formation of BaWO4 crystals with various morphologies.When TMEDA was used as a ligand, the microrods of BaWO4 crystals with length of 15~20m were formed via the selfassembly of cross-like plates of 250 nm in width and 2~3m in length.Key words BaWO4, Bidentate ligand, Morphology2.. .... ... BaWO4 ... .. .. ....... ...†..... ... , .. , 140-714(2007. 5. 22. .. )(2007. 7. 6. .... ). . 2.. .... .... BaWO4 ... ..... . ... [WO42]/[Ba2+] ... .. .. ... ... ... BaWO4 ... ..... .. ... ... .. . TMEDA. .... .... .. 250 nm. .. 2~3 m. ... .. .... .... .. ... ... 15~20 m ... .... .... BaWO4 ...... .1. BaWO4. .. ... .. ..... , ... .... (stimulated Raman scatering, SRS) .. ...
  • 2.

    Optical properties of SiO2 and TiO2 thin films deposited by electron beam process with and withoution-beam source

    송명근 | Yoon Dae Ho | Yo-Seung Song and 5other persons | 2007, 17(4) | pp.145~150 | number of Cited : 0
    Abstract PDF
    The SiO2 and TiO2 thin films for the multilayer interference filter application were manufactured by electron beam process. In case of electron beam process with ion source, the anode current was controlled by gas volume ratio of O2 and Ar. Substrate temperature of electron beam deposition without ion source was increased from 100 to 250oC with 50oC increment. The surface roughness values of SiO2 thin films was most low value at 200 oC substrate temperature and 0.2 A anode current respectively. And the surface roughness values of TiO2 thin films was most low value at room temperature and 0.2 A anode current repectively. The refractive index of SiO2 and TiO2 thin films to be deposited with ion source was usually lower than that of thin films without ion source.
  • 3.

    Fabrication of a periodically poled MgO : LiNbO3 ridge waveguide for a green laser generation

    Woo Seok Yang | Yoon Dae Ho | Lee Han Young and 5other persons | 2007, 17(4) | pp.151~155 | number of Cited : 0
    Abstract PDF
    Quasi-phase-matched (QPM) second harmonic generation (SHG) waveguide devices for a green light generation were fabricated by a periodically patterned electrode on the +Z crystal surface and homogeneous LiCl solution using a 5 mol% MgO doped congruent z-cut lithium niobate crystals. Using selective chemical etching, we confirmed the periodic (~6.8 μm) domain inverted structure and measured SHG properties of fabricated periodically poled MgO : LiNbO3 ridge-type waveguides.
  • 4.

    Photoluminescence properties of SrAl12O19 : Mn4+ red phosphor depending on Mn concentration and fluxes

    박우정 | Yoon Dae Ho | 정몽권 and 1other persons | 2007, 17(4) | pp.156~159 | number of Cited : 0
    Abstract PDF
    The red emission properties of Mn4+ doped SrAl12O19 prepared by the solid-state reaction was investigated, inorder to verify its potential to act as the red emitting phosphor of white LEDs. The emision spectrum exhibits a narrowband between 600~700 nm with four sharp peaks occurring at about 643, 656, 66, 671 nm due to the 2E→4A2 transitionof Mn4+. The excitation spectrum exhibits a broad band betwen 20~500 nm with three peaks occuring at about 338, 398and 468 nm, respectively. Moreover, the relative emission intensity of SrAl12O19 :Mn4+ with or without CaF2 and MgOfluxes measured at excitation source 390 nm. The relative emission intensity of SrAl12O19 :Mn4+ containing 0.67 mol% MgOwas aproximately 30 % higher than that of the base composition sample. Strontium hexa-aluminate measured at roomtemperature as a function of the substituted Mg concentration. MgO was aded to replace part of the Al2O3. Also, therelative emission intensity of SrAl12O19 :Mn4+ containing 0.67 mol% MgO and 0.67 mol% CaF2 was approximately about48 % higher than that of the base composition SrAl12O19:Mn4+.Key words SrAl12O19 :Mn4+, Red phosphor compensate effect, Luminescence, Mn4+ transition, White LEDsSrAl12O19:Mn4+.. .... .... Mn ... .. .. . ....
  • 5.

    Enhancement of the characteristics of carbon nanofibers by the on/off cyclic modulationof C2H2/H2 flow

    Kim Sung-Hoon | 2007, 17(4) | pp.160~164 | number of Cited : 0
    Abstract PDF
    Carbon nanofibers were deposited on silicon oxide substrate by thermal chemical vapor deposition method. Forthe enhancement of the characteristics of carbon nanofibers, the source gases (C2H2, H2) flows were intentionallymanipulated as the cyclic on/of modulation of C2H2 flow. By the cyclic modulation process during the initial depositionstage, the formation density of carbon nanofibers on the substrate could be much more enhanced. The diameter of as-characteristics of carbon nanofibers by the cyclic modulation process was discussed in association with the hydrogen gasetching ability.Key words Carbon nanofibers, Cyclic modulation of C2H2/H2 flow, Nucleation density, Surface morphology, Thermal CVD1. IntroductionDue to their fascinating geometries and unique electri-cal properties, carbon nanofilaments, called carbon nan-otubes if hollow and carbon nanofibers if filled [1-3],have been regarded as the promising materials to fabri-of the carbon nanofilaments, up to the present, variousmethods have been introduced, such as arc discharge[7], pyrolysis [8], laser ablation [9], plasma or thermalchemical vapor deposition methods [4, 10], and so forth.Among these methods, chemical vapor deposition meth-ods have been noted for having the advantages of thehigh purity and the high yield of carbon nanofilamentsformation [11]. Despite these advantages, however, thepractical applications of carbon nanofilaments to fulfillthe industry’s expectations still requires the massive pro-duction and/or the higher purity of carbon nanofilaments.Therefore, the development of their formation process toenhance their purity and formation yield would be inevi-
  • 6.

    Characterization and hydrothermal surface modification of non-swelling property micausing nano silver

    SEOK, JEONG-WON | KIM PAN CHAE | 박라영 | 2007, 17(4) | pp.172~178 | number of Cited : 1
    Abstract PDF
    Mica (muscovite) powders were synthesized by hydrothermal method (horizontal turning method). The hydrothermalconditions for the synthesis of mica were prepared by the ratio of K2O : Al(OH)3:SiO2 = 1 : 3 : 3 mol% as the starting materialswith KOH (8 mol%) solution as the hydrothermal solvent and reaction temperature at 260oC for 72 hrs. The synthetic powderas nano silver coating were prepared by the synthetic powder as raw materials, triple distilled water (0.5l) solution as thehydrothermal solvent with nano silver sol (1,000 ppm) as the material of nano silver coating and reaction temperature at160~260oC for 72 hrs. After hydrothermal treatment, structural, judgment of nano silver coating and character of nano silvercoated mica were examined by XRD, SEM, TEM-EDX and shake plask method.Key words Muscovite, Horizontal turning method, Nano silver coated mica, Hydrothermal method