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2005, Vol.15, No.6

  • 1.

    Evaporation and stabilization of the heavy metals in EAF dust-clay bodies

    김정환 | 2005, 15(6) | pp.217~221 | number of Cited : 0
    Abstract PDF
    The evaporation amounts of volatile Cd, Pb and Zn were characterized by measuring their total concentrationsin the EAF dust-clay bodies with various mixing ratio and heat treatment temperature. TCLP test was conducted for evaluatingthe chemical stabilities of the heavy metal elements. Evaporation amounts and leaching concentrations of heavy metalcomponents were strongly dependent on the mixing ratio and heat treatment temperature. The evaporation of the heavymetal components were decreased with increasing clay content and temperature. 20 wt% EAF dust-80 wt% clay sampleshows nearly zero evaporation and leaching concentrations of heavy metal components. XRD analysis showed that peakintensities of major crystalline phases such as franklinite and quartz were decreased with increasing the heat treatmenttemperature which means that the stabilization mechanism of the heavy metals was related with the vitrification process ofthe SiO2 in the clay.
  • 2.

    Growth of 1 inch LuVO4 single crystals by the edge-defined film-fed-growth (EFG) technique

    V.V. Kochurikhin | A.V. Klassen | E.V. Kvyat and 1other persons | 2005, 15(6) | pp.222~224 | number of Cited : 0
    Abstract PDF
    In spite of their superior optical and laser properties rare-earth orthovanadate single crystals have not been adopted yet into extensive industrial applications because of crystal growth difficulties. The edge-defined film-fed-growth (EFG) technique was applied successfully for the production of such crystals. At first time 1 inch LuVO4 single crystals were grown by the EFG technique using newly developed die construction of high porous iridium with the application of automatic diameter control system.
  • 3.

    Growth of long persistent SrAl2O4 : Eu2+, Dy3+ phosphor single crystals by the Verneuil method

    Choi Jong Keon | Kyungju Nam | 2005, 15(6) | pp.225~228 | number of Cited : 1
    Abstract PDF
    We have grown the long persistent SrAl2O4 :Eu2+, Dy3+ phosphor single crystal by Verneuil method. The obtainedsingle crystals were long persistent phosphorescence peaking at λ= 520 nm with a size of about 5 m diameter, 55 m length.The melting temperature of SrAl2O4 :Eu2+, Dy3+ measured Tmp=1968oC. The optimum composition was SrCO3 :Al(OH)3 :Eu2O3 :Dy2O3 = 1 : 2 : 0.015 : 0.02. Flow rate of H2 :O2 is about 4 : 1. Growthing rate is about 5 m/hr. The spectra of thephosphorescence from the crystals are quite similar to those obtained with sintered powders used for luminous pigments.The crystalline structure of long persistent SrAl2O4 :Eu2+, Dy3+ phosphor single crystal was determined by X-ray diffraction.
  • 4.

    Micro-porous ceramics using directionally solidified MgAl2O4/MgO eutectic crystals

    Jongho Lee | 2005, 15(6) | pp.229~233 | number of Cited : 0
    Abstract PDF
    Novel process was tried to obtain micro-porous ceramic body containing continuous pore channel. MgAl2O4/MgO eutectic fibers and rods have been grown successfully by the micro-pulling-down method, and the microstructures and optical characterizations of grown crystals were performed. MgAl2O4/MgO eutectic fibers of 0.3~1 mm in diameter and about 500 mm in length, and the rods having 5 mm in diameter with approximately 60 mm in length have been grown with the 6~120 mm/hr of growth speed. The eutectic fibers showed homogeneous microstructure in which MgO fiber aligned to the growth direction in the MgAl2O4 (spinel) matrix. The grown crystals looked semitransparency under naked eyes. Optical and orientational characterizations were performed. The second phase of MgO (periclase) was easily removed by selective etching with hydrochloric acid, and then porous bodies were obtained.
  • 5.

    High density plasma etching of single crystalline La3Ga5SiO14 for wide band, high temperature SAWfilter devices

    Cho, Hyun | 2005, 15(6) | pp.234~238 | number of Cited : 0
    Abstract PDF
    Effects of plasma composition, ion flux and ion energy on the etch rate, surface morphology and near surface stoichiometry of a single crystalline La3Ga5SiO14 wafer have been examined in Cl2/Ar inductively coupled plasma (ICP) discharges. Maximum etch rate ~1600 ?min was achieved either at relatively high source power (~1000 W) or high Cl2 content conditions in Cl2/Ar discharges. The etched surfaces showed similar or better RMS roughness values than those of the unetched control sample and the near surface stoichiometry was found not to be affected by ICP etching.
  • 6.

    Dispersion stability of ultra-fine BaTiO3 suspensions in aqueous medium

    전명표 | Cho Jeong Ho | 마용준 and 2other persons | 2005, 15(6) | pp.239~243 | number of Cited : 0
    Abstract PDF
    The effect of pH and particle size on the dispersion stability of ultra-fine BaTiO3 suspensions in aqueous medium have been investigated by means of zeta potential, sediment experiments, and powder properties (particle analysis, specific surface area) etc. Zeta potential as a function of pH for two particles of different size increases from -75 to +10 mV with decreasing pH from 8.5 to 1.4. The curve of zeta potential for small particle (150 nm) has slow slope than that of large particle (900 nm), giving IEP (isoelectric point) value of pH = 1.6 for small particle and pH = 1.9 for large particle respectively, which means that it is more difficult to control zeta potential with pH for small particle than large particle. The dispersion stability of BaTiO3 particles in aqueous medium was found to be strongly related with the agglomeration of colloidal suspensions with time through the sedimentation behaviors of colloidal particles with time and pH value.
  • 7.

    Characterization of relationship between particle size and powder properties for BaTiO3

    전명표 | Cho Jeong Ho | KIM BYUNG IK | 2005, 15(6) | pp.244~251 | number of Cited : 0
    Abstract PDF
    The relationship betwen particle size of hydro-thermally synthesized barium titanate powders (BT01, BT02,BT03, BT04, BT05) and the powder properties was investigated by means of particle size, specific surface area, zetapotential, XPS, XRD and SEM. Particle size determined by laser light scattering is closely related with specific surfaceincreasing particle size except BT03 powder. BT03 sample showed higher surface area than BT04 sample of equivalentparticle size, which was atributed mostly to the agglomeration of particles in terms of SEM image and XRD analysis.Zeta potential increased with increasing particle size with the exception of BT02 and BT03 which showed larger minusvalue of zeta potential in comparison with other BT powders. Zeta potential results of BT02 and BT03 are considered tobe related with the disolution of Ba2+ ion in these powers which was examined by XPS.
  • 8.

    Growth of CuGaSe2 single crystal thin film for solar cell development and its solar cell application

    Yun,Suk-Jin | Kwangjoon Hong | 2005, 15(6) | pp.252~259 | number of Cited : 0
    Abstract PDF
    Single crystal CuGaSe2 layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at 450oC with hot wall epitaxy (HWE) system by evaporating CuGaSe2 source at 610oC. The crystalline structure of the single crystal thin films was investigated by the photoluminescence (PL) and double crystal X-ray diffraction (DCXD). The carrier density and mobility of single crystal CuGaSe2 thin films measured with Hall effect by Van der Pauw method are 4.87?017 cm-3 and 129 cm2/V톝 at 293 K, respectively. The temperature dependence of the energy band gap of the CuGaSe2 obtained from the absorption spectra was well described by the Varshni뭩 relation, Eg(T) = 1.7998 eV - (8.7489?0-4 eV/K)T2/(T + 335 K). The voltage, current density of maxiumun power, fill factor, and conversion efficiency of n-CdS/p-CuGaSe2 heterojunction solar cells under 80 mW/cm2 illumination were found to be 0.41 V, 21.8 mA/cm2, 0.75 and 11.17 %, respectively.
  • 9.

    Optimization of p+ seeding layer for thin film silicon solar cell by liquid phase epitaxy

    이은주 | Soohong Lee | 2005, 15(6) | pp.260~262 | number of Cited : 0
    Abstract PDF
    Thickness optimization of heavily doped p-type seeding layer was studied to improve performance of thin film silicon solar cell. We used liquid phase epitaxy (LPE) to grow active layer of 25 mm thickness on p+ seeding layer. The cells with p+ seeding layer of 10 mm to 50 mm thickness were fabricated. The highest efficiency of a cell is 12.95 %, with VOC = 633 mV, JSC = 26.5 mA/cm2, FF = 77.15 %. The p+ seeding layer of the cell is 20 mm thick. As thicker seeding layer than 20 mm, the performance of the cell was degraded. The results demonstrate that the part of the recombination current is due to the heavily doped seeding layer. Thickness of heavily doped p-type seeding layer was optimized to 20 mm. The performance of solar cell is expected to improve with the incorporation of light trapping as texturing and AR coating.
  • 10.

    Preparations and characteristics of the ceramic balls for heavy metals absorption and antibacterialactivities in the drinking water

    박춘원 | 박라영 | 박선민 | 2005, 15(6) | pp.263~268 | number of Cited : 0
    Abstract PDF
    The ceramic balls impregnated with 20~40 nm sized Ag colloid were examined for heavy metals absorption and antibacterial activities in the drinking water. The preparation conditions of ceramic ball that the porosity was excellent were as follows: starting material: 85 wt% Ca10(PO4)6(OH)2, binder: 5 wt% PVA and 15 wt% a-Ca3(PO4)2, heating temperature: 1000oC, duration: 3 hrs. The ceramic balls obtained under these conditions showed specific surface area of 110 m2/g, pore size of 120 mm and porosity of 80 %. Also, as the results of a performance test on a rate of adsorbing and removing heavy metals in the drinking water by using the AAS, heavy metals such as Zn, Mn, Fe and Cu were removed to the extent that their content became 0.03 mg/l or lower after 1 day and they showed an excellent bactericidal activity that all coliforms were killed after 3 hrs.
  • 11.

    Crack propagation behavior of in-situ structural gradient Ni/Ni-aluminide//Ti/Ti-aluminide laminatematerials

    Jin-Kon Kim | 정동석 | Cho, Hyun | 2005, 15(6) | pp.269~275 | number of Cited : 0
    Abstract PDF
    Ni/Ni-aluminide//Ti/Ti-aluminide laminate composite, considered as a functionally gradient material, was manufactured by thin foil hot press technique. Thick intermetallic layers of NiAl and TiAl3 were formed by a self-propagating high-temperature synthesis (SHS) reaction, and thin continuous layers of Ni3Al and TiAl were formed by a solid-state diffusion. Fracture resistance with loading along the crack arrester direction is higher than crack divider direction due to the interruption of crack growth in metal layers. The Ni3Al and NiAl intermetallic layer showed cleavage and intergranular fracture behavior, respectively, while the fracture mode of TiAl3 layer was found to be an intragranular cleavage. The debonding between metal and intermetallic layer and the pores were observed in the Ni/Ni-aluminide layers, resulting in the lower fracture resistance. With the results of acoustic emission (AE) source characterization the real time of failure and the effect of AE to crack growth could be monitored.