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2009, Vol.19, No.6

  • 1.

    Fabrication and properties of superhydrophobic SiO2 thin film by sol-gel method

    Jinho Kim | Tae-Young Lim | Sae-Hoon Kim and 1other persons | 2009, 19(6) | pp.277~281 | number of Cited : 2
    Abstract PDF
    Superhydrophobic SiO2 thin films were successfully fabricated on a glass substrate by sol-gel method. To fabricate SiO2 thin film with a high roughness, SiO2 nano particles were added into tetraethoxysilane (TEOS) solution. The prepared SiO2 thin film without an addition of SiO2 nano particles showed a very flat surface with ca. 1.27 nm of root mean square (RMS) roughness. Otherwise, the SiO2 thin films fabricated by using coating solutions added SiO2 nano particles of 1.0, 2.0 and 3.0 wt% showed a RMS roughness of ca. 44.10 nm, ca. 69.58 nm, ca. 80.66 nm, respectively. To modify the surfaces of SiO2 thin films to hydrophobic surface, a hydrophobic treatment was carried out using a fluoroalkyltrimethoxysilane (FAS). The SiO2 thin films with a high rough surface were changed from hydrophilic to hydrophobic surface after the FAS treatment. Especially, the prepared SiO2 thin film with a RMS roughness of 80.66 nm showed a water contact angle of 163 o .
  • 2.

    Phase transformation and magnetic properties of NixFe100 − x thin films deposited by a co-sputtering

    강대식 | 송조한 | Nam, Joong-Hee and 2other persons | 2009, 19(6) | pp.282~287 | number of Cited : 0
    Abstract PDF
    NixFe100 − x films with a thickness of about 100nm were deposited on Si(100) substrates at room temperature by a DC magnetron co-sputtering using Fe and Ni targets. Compositional, structural, electrical and magnetic properties of the films were investigated. Ni67Fe33, Ni55Fe45, Ni50Fe50, Ni45Fe55, Ni40Fe60 films are obtained by increasing the sputtering power of the Fe target. The films of x < 55 have BCC structure and show the phase transformation after annealing at the range of 300~450℃ for 2 h. On the other hand, the films of x < 50 have the mixed crystalline phases of BCC and FCC after the annealing treatment. The saturation magnetization was decreased initially by the phase transformation effect but then increased again after annealing at 450℃ due to the grain growth and crystallization of BCC phases.
  • 3.

    Fabrication of patterned substrate by wet process for biochip

    Jinho Kim | 이민 | Jonghee Hwang and 2other persons | 2009, 19(6) | pp.288~292 | number of Cited : 1
    Abstract PDF
    Hydrophobic/hydrophilic patterned substrates were fabricated on a glass substrate by a liquid phase deposition (LPD) method. Hydrophobic surface was obtained by modifying ZnO thin films with a rough surface using a fluoroalkyltrimethoxysilane (FAS) and hydrophilic surface was prepared by decomposing FAS on an exposed to UV light. The hexagonal ZnO rods were perpendicularly grown by LPD method on glass substrates with a ZnO seed layer. The diameter and thickness of hexagonal ZnO rods were increased as a function of increases of immersion time. The surface morphology, thickness, crystal structure, transmittance and contact angle of prepared ZnO thin films were measured by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), UV-visible spectrophotometer (UV-vis) and contact angle measurement. Hydrophilic ZnO thin films with a contact angle of 20 o ~30 o were changed to a hydrophobic surface with a contact angle of 145 o ~161 o by a FAS surface treatment. Prepared hydrophobic surface was pattered by an irradiation of UV light using shadow mask with 300 μm or 3 mm dot size. Finally, the hydrophobic surface exposed to UV light was changed to a hydrophilic surface.
  • 4.

    Reflectance spectrum properties of DBR and microcavity porous silicon

    김영유 | 김한중 | 2009, 19(6) | pp.293~297 | number of Cited : 0
    Abstract PDF
    In this paper, we made three kinds of porous silicon samples (single layer, distributed Bragg reflector, and microcavity) by electrochemical etching p-type silicon substrate. And then, we investigated their reflectance spectrum properties. We found that the number of fringe patterns and the maximum reflectivity of porous silicon multilayer increased compared with a porous silicon sinlge layer. In addition, we can observe that the DBR (distributed Bragg reflector) porous silicon has a full-width at half-maximum about 33 nm which is narrower than the porous silicon single layer and porous silicon microcavity.
  • 5.

    Thermal properties of the surface-modified Inconel 617

    Cho, Hyun | Kwang-Hyun Bang | BYEONG WOO LEE | 2009, 19(6) | pp.298~304 | number of Cited : 1
    Abstract PDF
    The effect of the surface treatments on the high temperature properties of the Inconel 617, one of the promising candidate alloys for high temperature heat-transport system, has been studied. Various surface modification methods including a rapid thermal process (RTP), a hydrothermal treatment, and a physical vapor deposition (2 μm thick TiAlN film by an arc discharge) were applied to the Inconel 617. The morphological and the structural properties of the surfacemodified Inconel 617 samples after heat treatment at 1000℃ in the air were compared to find out whether inhomogeneous formation of Cr2O3 crust at the surface region was suppressed or not. TiAlN-coated Inconel 617 showed homogeneous microstructure and the lowest wear loss compared to bare, RTP- and hydrothermally-treated Inconel 617 by suppressing the Cr2O3 crust formation.
  • 6.

    Fabrication of functional nanoparticles by layer-by-layer self-assembly method

    Jinho Kim | Jonghee Hwang | Tae-Young Lim and 1other persons | 2009, 19(6) | pp.305~310 | number of Cited : 1
    Abstract PDF
    TiO2 thin films consisting of positively charged poly (diallyldimethylammonium chloride) (PDDA) and negatively charged titanium (IV) bis (ammonium lactato) dihydroxide (TALH) were successfully fabricated on a poly (methyl methacrylate) (PMMA) by layer-by-layer (LBL) self-assembly method. By the measurement of quartz crystal microbalance (QCM), it was found that as the solution pH of TALH decreased, the deposition volume of TALH increased and the thickness of (PDDA/TALH) thin film coated on the surface of PMMA particles increased. The PMMA particles coated with the coating sequence of (PDDA/TALH)n showed the variation of color changes as a function of the number of bilayer. The number of bilayer (n) of (PDDA/TALH) thin films was 10 and 20, the values of a* and b* decreased from those of PMMA particles without coating films and the color changes was shifted to green and blue direction in the a*, b* chromaticity diagram. And then, the number of n increased to 30 and 40, the values of a* and b* increased and the color changes was shifted to red and yellow direction, respectively. Finally the PMMA particles coated with (PDDA/TALH)50 thin film showed a little same value of a* and b* with the PMMA particles without (PDDA/TALH) thin film.
  • 7.

    Preparation and characteristics of HfO2 and CeO2 doped 3Y-TZP block for dental ceramic block

    지상용 | 지형빈 | PARK,HONG-CHAE and 1other persons | 2009, 19(6) | pp.311~317 | number of Cited : 0
    Abstract PDF
    3Y-TZP block doped with HfO2 and CeO2 for dental ceramic block to the proliferation of CAD/CAM systems was prepared by heating at 800~1100℃ and then sintering at 1450℃. The influences of heating temperature and addition of HfO2 and CeO2 on the mechanical and chemical properties of 3Y-TZP block were investigated. Using the EDS mapping images, HfO2 and CeO2 was well dispersed in the 3Y-TZP matrix. 3 wt% HfO2 doped block showed the optimum biaxial strength (1 GPa), while 3 wt% CeO2 doped block enhanced the stability of t-ZrO2 under hydrothermal atmosphere.
  • 8.

    A study on the black core formation of artificial lightweight aggregates at various sintering atmospheres

    KIM, YOOTAEK | 류유광 | 장창섭 and 3other persons | 2009, 19(6) | pp.318~323 | number of Cited : 4
    Abstract PDF
    The lightweight aggregates made of bottom ash (70 wt%) and dredged soil (30 wt%) were prepared to investigate the property differences at various sintering atmospheres. The green aggregates were sintered at 1150℃ and 1200℃ with oxidized, neutralized and reduced atmospheres. The aggregates sintered with oxidized atmosphere showed a clear border between shell and black core area. However, the aggregates sintered with a reduced atmosphere showed only black core area in the entire cross-section of the aggregates. The black core area of the aggregates sintered with a neutralized atmosphere increased with increasing N2 gas flow rates. It was determined that the sintering atmosphere was similar to that of rotary kiln when the CO gas flow was 100 cc/min to make a reduced atmosphere in tube furnace. The water absorption rates of both aggregates from tube furnace with reduced atmosphere and rotary kiln were very similar to each other.
  • 9.

    The effect of Ca additions on the ignition and combustion behaviors of Mg alloys

    정동석 | Cho, Hyun | Jin-Kon Kim | 2009, 19(6) | pp.324~327 | number of Cited : 0
    Abstract PDF
    In the present study, the effect of Ca additions on the ignition and combustion behaviors of Mg alloys has been investigated. Cracks and inclusions were observed at the free surface and interior in as-cast pure magnesium but not in Cabearing Mg alloys. There was a tendency that ignition temperature rapidly increased with increasing Ca content in Mg-Ca alloy. Saturated composition for increasing of ignition temperature was related with solid solubility of Ca in Ca-bearing Mg alloys. The protective oxide layers, MgO, could also be found on the combustion surface of Ca-bearing magnesium alloy.