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pISSN : 1225-1429 / eISSN : 2234-5078

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2010, Vol.20, No.5

  • 1.

    Preparation and characterization of ZnWO4 nanocrystallines and single crystals

    Chang Sung Lim | 2010, 20(5) | pp.197~201 | number of Cited : 0
    Abstract PDF
    ZnWO4 nanocrystallines were prepared from polymeric complex method using microwave irradiation. The average nanocrystalline sizes were 18~25 nm showing an ordinary tendency to increase with the temperatures from 400 to 600oC. Bulk type single crystals of ZnWO4 were grown successfully in the [100], [010] and [001] directions using the Czochralski method. The effect of the growth parameters, such as the rotation speed, pulling rate and diameter of the grown crystals, were examined. The hardness, thermal expansion coefficients and dielectric constants of the crystals were evaluated.
  • 2.

    Growth parameters and formation of slip plane in ZnWO4 single crystals by the Czochralski method

    Chang Sung Lim | 2010, 20(5) | pp.202~206 | number of Cited : 0
    Abstract PDF
    Single crystals of ZnWO4 were grown successfully in the [100], [010] and [001] directions using the Czochralski method. The growth parameters and the formation of slip plane in ZnWO4 crystals were studied. ZnWO4crystals had a cleavage plane of (010). The dislocation density on the (010) plane at the center of the crystal was lower than that of the edge region. It was inferred that the high density at the edge of the crystals was caused by the thermal gradient during crystal growth. The etch pit arrangement revealed the (100) slip plane to be most active during crystal growth.
  • 3.

    The chemical composition and shape of inclusion of amethyst

    윤시내 | Song Young Jun | YON SEOG JOO | 2010, 20(5) | pp.207~215 | number of Cited : 1
    Abstract PDF
    This study was carried out for the purpose of obtaining the basic data for identifying the origin of amethyst. For this, the three dimensional shapes of inclusions contained in various amethyst were observed with Stereo Zoom microscope. The shape and chemical composition of cross section of solid inclusion and the chemical composition of evaporite were investigated by SEM-EDS. The evaporite is made from evaporating of liquid inclusion which is flowed out of amethyst sample by decompressing. Lastly, The trace mineral composition of amethyst was investigated by ICP-AES after digesting the amethyst sample with HF-H2SO4 solution.
  • 4.

    Phase transformation and magnetic properties of NiFe thin films on Si(100) wafer and SiO2/Si(100) substrate by co-sputtering

    강대식 | Song Jong Han | Nam, Joong-Hee and 2other persons | 2010, 20(5) | pp.216~220 | number of Cited : 1
    Abstract PDF
    Ni-Fe alloys have various applications such as thin film inductor, thin film transformer, magnetic head’s shield case, etc. Magnetic properties of Ni-Fe thin films depend on the process parameters such as thickness, contents, deposition rate, substrates, etc. In this study, NiFe films with a thickness of about 150nm were deposited on Si(100) wafer and SiO2/Si(100) substrate at room temperature by a DC magnetron co-sputtering using Fe and Ni targets. Their phase formation and magnetic properties as a function of annealing temperature were investigated with XRD, FE-SEM and VSM. The assputtered films have BCC structure. With increasing annealing temperature, NiFe thin film for SiO2/Si(100) substrate transformed completely from BCC to FCC phase above 500oC, but some BCC phase remained above 500oC on Si(100)wafer. For samples annealed at 450oC, squareness ratio of NiFe thin film shows peak value and its saturation magnetization is around 0.0118 emu, which means that the optimum annealing temperature of NiFe thin film seems to be 450oC. The saturation magnetization of films decreased rapidly above the annealing temperature of 500oC due to phase transformation from BCC to FCC phase.
  • 5.

    Fabrication of TiO2/polyelectrolyte thin film for a methyl mercaptan gas sensor

    김진호 | 황종회 | LEE MI JAI and 2other persons | 2010, 20(5) | pp.221~226 | number of Cited : 1
    Abstract PDF
    Quartz crystal microbalance (QCM) gas sensor to detect methyl mercaptan (CH3SH) gas was fabricated by depositing TiO2 nanoparticles and polyelectrolyte on the electrode of QCM. The TiO2/poly(sodium 4-styrenesulfonate) (PSS)thin film fabricated by a layer-by-layer self-assembly (LBL-SA) method showed a high surface area and increased the sensitivity of gas sensor. When the QCM sensors coated with triethanolamine (TEA) or (TiO2/PSS) were exposed to methyl mercaptan gas (1.0 ppm), the frequency shifts of QCM with TEA casting film and TiO2/PSS thin film were ca. 9 Hz and ca. 24 Hz, respectively. As the bilayer number of (TiO2/PSS) increased, the frequency shift of QCM sensor with (TiO2/PSS)thin film was gradually increased. In addition, the frequency shift of QCM sensor was gradually increased as the concentration of methyl mercaptan gas increased from 0.5 ppm to 2.0 ppm. In this study, the surface morphology and sensor property of QCM sensor coated with (TiO2/PSS) thin film were measured.
  • 6.

    Fabrication of super hydrophilic TiO2 thin film by a liquid phase deposition

    김진호 | 황종회 | Tae-Young Lim and 2other persons | 2010, 20(5) | pp.227~231 | number of Cited : 3
    Abstract PDF
    광촉매 특성을 지닌 초친수 TiO2 박막을 액상증착법에 의해 유리 기판 위에 성공적으로 제조하였다. 제조된TiO2 박막은 70oC에서 박막표면에 TiO2 나노 입자들을 형성하였다. TiF4 용액의 침적시간이 증가됨에 따라 박막의 두께도일정하게 증가되었다. TiO2 박막은 약 5o이하의 접촉각과 가시영역에서 약 75~90 %의 투과율을 보여주었다. 또한 제조된TiO2 박막은 자외선 조사에 의해 메칠오렌지 용액을 분해하는 광촉매 특성을 보여주었다. 침적시간 조건에 따라 제조된 박막의 표면 구조, 광학적 특성, 접촉각을 FE-SEM, AFM, UV-Vis, contact angle meter를 이용하여 측정하였다.
  • 7.

    Molecular dynamic studies for elastic constant of SiC crystal at high temperature

    박병우 | Ho-Yong Shin | Jong Ho Kim and 1other persons | 2010, 20(5) | pp.232~236 | number of Cited : 0
    Abstract PDF
    Silicon carbide (SiC) ceramics are widely used in the application of high-temperature structural devices due to their light weight as well as superior hardness, fracture toughness, and temperature stability. In this paper, we employed classical molecular dynamics simulations using Tersoff’s potential to investigate the elastic constants of the SiC crystal at high temperature. The stress-strain characteristics of the SiC crystal were calculated with the LAMMPS software and the elastic constants of the SiC crystal were analyzed. Based on the stress-strain analysis, the SiC crystal has shown the elastic deformation characteristics at the low temperature region. But the slight plastic deformation behavior was shown as applied the high strain over 1,000oC. Also the elastic constants of the SiC crystal were changed from about 475 GPa to 425 GPa as increased the temperature to 1,250oC.
  • 8.

    Suitability evaluation of magnesium substituted biphasic calcium phosphates prepared by coprecipitation method

    이형신 | Taewan Kim | Donghyun Kim and 2other persons | 2010, 20(5) | pp.237~242 | number of Cited : 2
    Abstract PDF
    Magnesium-substituted BCP (biphasic calcium phosphate) powders were prepared by incorporating small amounts of magnesium into the structure of different hydroxyapatite (HAp)/β-tricalcium phosphate (β-TCP) ratios through coprecipitation method. A series of magnesium substitutions ranging from 0, 0.5, and 1.0 wt%, which are comparable to the measured magnesium contents, were performed. The obtained powders were characterized by the following analytical techniques: X-ray diffraction analysis (XRD), Thermo Gravimetric Analyzer (TGA) and Fourier transform infrared spectroscopy (FT-IR). The results have shown that substitution of magnesium in the calcium-deficient apatites resulted in the formation of biphasic mixtures of different HAP/β-TCP ratios after heating above 1000oC. The 1.0 wt% magnesiumsubstituted-BCP were soaked in Hank's solutions after 2 weeks to observe the morphology of the biocement, especially needle-like hydroxyapatite crystals and to estimate the length and diameter of nanoneedle crystals.
  • 9.

    Synthesis and characterization of silicon ion substituted biphasic calcium phosphate

    송창원 | Taewan Kim | Donghyun Kim and 2other persons | 2010, 20(5) | pp.243~248 | number of Cited : 2
    Abstract PDF
    Si-substituted biphasic calcium phosphates (Si-BCP) were prepared by co-precipitation method. X-ray diffraction and fourier transform infrared spectroscopy were used to characterize the structure of Si-BCP powders. The Si-BCP powders with various Ca/(P+Si) molar ratio were carried out on structural change of hydroxyapatite (HAp) and β-tricalcium phosphate (ß-TCP). The in-vitro bioactivity of the Si-BCP powders was determined by immersing the powders in SBF solution, after that observing the chemical composition and morphology change by X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy.