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2012, Vol.22, No.2

  • 1.

    Effects of Ni layer as a diffusion barrier on the aluminum-induced crystallization of the amorphous silicon on the aluminum substrate

    윤원태 | KIM YOUNG KWAN | 2012, 22(2) | pp.65~72 | number of Cited : 0
    Abstract PDF
    Aluminum induced crystallization of amorphous silicon was attempted by the aluminum substrate. To avoid the layer exchange between silicon and aluminum layer, Ni layer was deposited between these two layers by sputtering. To obtain the bigger grain of the crystalline silicon, wet blasted silica layer was employed as windows between the nickel and a-Si layer. Ni obtained after the annealing treatment at 520oC was found to be a promising material for the diffusion barrier between silicon and aluminum. One way to obtain bigger grain of crystalline silicon layer applicable to solar cell of higher performance was envisioned in this investigation.
  • 2.

    The optical and structural properties by ZrO2 and Y2O3 compositional ratio of Co- and Ce-doped cubic zirconia (YSZ) single crystals

    Moon, So-I | 박희율 | SEOK, JEONG-WON | 2012, 22(2) | pp.73~77 | number of Cited : 1
    Abstract PDF
    Co-(0.8 wt%) and Ce-(0.4 wt%) doped cubic zirconia (ZrO2 : Y2O3 = 80 : 20, 70 : 30, 60 : 40, 50 : 50 wt%) single crystals grown by a skull melting method were heat-treated in N2 at 1000oC for 5 hrs. The orange, yellowish brown and brown colored as-grown single crystals were changed into either brownish red, yellow and green color after the heat treatment. Before and after the heat treatment, the YSZ (yttria-stabilized zirconia) single crystals were cut for wafer form (φ6.5 mm × t2 mm). The optical and structural properties were examined by UV-VIS spectrophotometer and X-ray diffraction. Absorption by Ce3+(2F5/2, 7/2(4f) → 2Tg(5d1)), Co2+(4A2(4F) → 4T1(4F) or 4T1(4P)) and Co3+, change of ionization energy and lattice parameter were confirmed.
  • 3.

    Structural change and electrical conductivity according to Sr content in Cu-doped LSM (La1 − xSrxMn0.8Cu0.2O3)

    류지승 | 노태민 | 김진성 and 1other persons | 2012, 22(2) | pp.78~83 | number of Cited : 1
    Abstract PDF
    The structural change and the electrical conductivity with Sr content in La1 − xSrxMn0.8Cu0.2O3 (LSMCu) were studied. La0.8Sr0.2MnO3 (LSM) and La1 − xSrxMn0.8Cu0.2O3 (0.1 ≤ x ≤ 0.4) were synthesized by EDTA citric complexing process (ECCP). A decrease in the lattice parameters and lattice volumes was observed with increase of Sr content, and these results were attributed to the increasing Mn4+ ions and Cu3+ ions in B-site. The electrical conductivity measured from 500oC to 1000oC was increased with increase of Sr content in the 0.1 ≤ x ≤ 0.3 composition range, and it was 172.6 S/cm (at 750oC) and 177.7 S/cm (at 950oC, the maximum value) in x = 0.3. The electrical conductivity was decreased in x = 0.4because of the presence of the second phase in the grain boundaries. The lattice volume was contracted by increase of Mn4+ ions and Cu3+ ions in B-site according to increase of Sr content and the electrical conductivity was increased with increase of charge carriers which were involved in the hopping mechanism.
  • 4.

    NO2 gas sensing based on graphene synthesized via chemical reduction process of exfoliated graphene oxide

    Tran Van Khai | maneeratanasarnprachuporn | Kwang Bo Shim | 2012, 22(2) | pp.84~91 | number of Cited : 1
    Abstract PDF
    Single and few-layer graphene nanosheets (GNs) have successfully synthesized by a modified Hummer’s method followed by chemical reduction of exfoliated graphene oxide (GO) in the presence of hydrazine monohydrate. GO and GNs were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), X-ray diffractions (XRD), Raman spectroscopy, Transmission electron microscopy (TEM), Atomic force microscopy (AFM),Optical microscopy (OM) and by electrical conductivity measurements. The result showed that electrical conductivity of GNs was significantly improved, from 4.2 × 10−4 S/m for GO to 12 S/m for GNs, possibly due to the removal of oxygencontaining functional group during chemical reduction. In addition, the NO2 gas sensing characteristics of GNs are also discussed.
  • 5.

    Bioactivity behavior of Si and Mg ion-substituted biphasic calcium phosphate powders

    김태완 | 김동헌 | 진형호 and 3other persons | 2012, 22(2) | pp.92~98 | number of Cited : 1
    Abstract PDF
    The co-precipitation technique has been applied to synthesize biphasic calcium phosphate (BCP). Ca(NO3)2 · 4H2O,(NH4)2HPO4, TEOS and Mg(NO3)2 · 6H2O as the starting materials was used. After the heat treatment of powder crystalline phases HAp and β-TCP analysis showed a mixed phase. The overall spectra appear to have mainly two modes corresponding to characteristic PO43− and OH− groups. After immersion in Hanks’ Balanced Salt Solution (HBSS) for 1week a precipitation started to be formed with individual small granules on the specimen surface. An MTT assay indicated that ionic substituted BCP powders had no cytotoxic effects on MG-63 cells, and that they have good biocompatibility.
  • 6.

    Bioactivity behavior of biphasic calcium phosphate powders prepared by co-precipitation method

    Taewan Kim | Kim Donghyun | 진형호 and 3other persons | 2012, 22(2) | pp.92~104 | number of Cited : 2
    Abstract PDF
    The co-precipitation technique has been applied to synthesize biphasic calcium phosphate (BCP). Ca(NO3)2 · 4H2O and (NH4)2HPO4 as the starting materials was used. X-ray diffraction (XRD) and Fourier transformed infrared (FT-IR)spectroscopy were used to characterize the structure of as-synthesized and calcined BCP powders. After immersion in Hanks’ Balanced Salt Solution (HBSS), for 1 week a precipitation started to be formed with individual small granules on the specimen surface. An MTT assay indicated that BCP powders have no cytotoxic effects on MG-63 cells, and that they have good biocompatibility.
  • 7.

    A study on the ideal structure of feed sprue in the investment casting process

    이광열 | 2012, 22(2) | pp.105~113 | number of Cited : 1
    Abstract PDF
    Maintenance training is generally provided to teach employees new knowledge and techniques in order to increase their qualities.It means that the purpose of maintenance training is to increase an employee's knowledge or technique level and to maintain or increase their performance level through continuous training in their field, and the methods, contents and the level of training vary depending on the type of job they perform. Maintenance training is more important for jobs that require continuous technical increases or research, or for professional jobs that continuously require new knowledge and techniques. The purpose of this study is to provide quality service to consumers by responding to the rapidly changing jewelry distribution environment and to quickly and accurately acquire new and advanced jewelry inspection and appraisal techniques, and to contribute to the healthy consumption culture through a general quality increase in the jewelry industry.