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2004, Vol.14, No.3

  • 1.

    Preparation of hydroxyapatite/TiO2 biocomposite powders by wet chemical method

    정항철 | Jong-Kook Lee | 2004, 14(3) | pp.83~89 | number of Cited : 0
    Abstract PDF
    In this work, HA/TiO2 biocomposite to get high mechanical properties with biocompatibility were prepared. HA/ TiO2 biocomposite powders were prepared by mixing TiO2 and HA powders which were synthesized through sol-gel, precipitation and hydrothermal methods. The mixing ratio was fixed at 1 : 1 ratio (HA/TiO2, wt%). HA/TiO2 biocomposite powders showed different microstructures depending on their particle size and shape. The smaller particles were coated on the surface of larger particles, whereas they were well mixed and dispersed when both TiO2 and HA were nanocrystallites. HA/ TiO2 biocomposite powders with homogeneous microstructure showed high sintered density and good mechanical properties.
  • 2.

    Electrical charateristics of MIS BST thin films

    Park Chi Sun | 2004, 14(3) | pp.90~94 | number of Cited : 0
    Abstract PDF
    The variation of electrical properties of (Ba,Sr)TiO3 [BST] thin films for Metal-Insulator-Semiconductor (MIS)capacitors was investigated. BST thin films were deposited on p-Si(10) substrates by the RF magnetron sputtering withtemperature range of 500~600oC. The dielectric properties of MIS capacitors consisting of Al/BST/SiO2/Si sandwichstructure were measured for various conditions. We examined the characteristics of MIS capacitor with various oxygenpressure, substrate temperature and (Ba+Sr)/Ti ratio. It was found that the leakage curent was reduced in MIS capacitorwith high quality SiO2 layer was grown on bare p-Si substrate by thermal oxidation. The BST MIS structure showedrelatively high capacitance even though it is the combination of high-dielectric BST thin films and SiO2 layer. The chargestate densities of the MIS capacitors and Current-voltage characteristics of the MIS capacitor were investigated. By applyingSiO2 layer between BST thin films and Si substrate, low leakage current of 10-10 order was observed.
  • 3.

    Effects of elastic strain on the agglomeration of silicide films for electrical contacts in integrated circuit applications

    최준호 | 2004, 14(3) | pp.95~100 | number of Cited : 0
    Abstract PDF
    This paper reports a potential problem in the electrical performance of the silicide film to silicon contacts withrespect to the scaling trend in integrated circuit (IC) devices. The effects of elastic strain on the aglomeration of thecoherent silicide film embedded in an infinite matrix are studied employing continuum linear elasticity and finite-differencenumerical method. The interface atomic difusion is taken to be the dominant transport mechanism where both capilarityand elastic strain are considered for the driving forces. Under plane strain condition with elasticaly homogeneous andanisotropic system with cubic symetry, the dilatational misfit and the tetragonal misfit in the direction parallel to the filmthickness are considered. The numerical results on the shape evolution agree with the known trend that the equilibriumaspect ratio of the film increases with the elastic strain intensity. When the elastic strain intensity is taken to be only afunction of the film size, the flat film morphology with a large aspect ratio becomes increasingly unstable since theequilibrium aspect ratio decreases, as the film scales. The shape evolution results in a large decrease in contact to siliconarea, and may deteriorate the electrical performances.
  • 4.

    A study on the nature of needle-like inclusions in corundum crystals

    배상덕 | KIM PAN CHAE | 김상기 and 1other persons | 2004, 14(3) | pp.101~104 | number of Cited : 0
    Abstract PDF
    It was realized that MC-XRD is useful for phase analyzing of inclusions in crystals because it can focus the XRay beam to the small particles sized dozens of mm with high S/N ratio. By using this MC-XRD, needle-like inclusions which are seen generally in corundum crystals known as rutile was found to be the iron titanium oxide and iron oxide which has the chemical composition of Fe2TiO4, Fe2TiO5 and Fe2O3 respectively
  • 5.

    Appraising elements of natural diamonds and influences on the value

    김상기 | KIM PAN CHAE | 배상덕 and 1other persons | 2004, 14(3) | pp.105~109 | number of Cited : 0
    Abstract PDF
    In this study, we analyzed the influences of appraising elements such as weight, color and clarity of natural diamonds on their value in the round brilliant cut diamonds. To analyze the influences of these elements on the value of diamonds, data were made from a Rapaport Diamond Report which is the most reliable source of diamond prices. As the result of this study, it is clearly understood that color and clarity equally influenced the value of diamonds as a whole, but there were some partial variations according to grades of both elements. That is, value of clarity was higher than that of color in higher-quality diamonds but value of clarity was lower than that of color in lower-quality diamonds. Also, value of diamonds were closely co-related by three main elements which were weight, color and clarity, but weight was the most influencing element on the value of natural diamonds.
  • 6.

    Synthesis of aragonite precipitated calcium carbonate by homogeneous precipitate reaction of Ca(OH)2 and Na2CO3

    박진구 | KIM HWAN | Hyun Seo Park and 2other persons | 2004, 14(3) | pp.110~114 | number of Cited : 5
    Abstract PDF
    Formation behavior of aragonite precipitated calcium carbonate was investigated with changed the concentration of Na2CO3 solution and addition method which added in the Ca(OH)2 slurry at 75oC. In this reaction, we found that Na+ ions were substituted into Ca2+ ion site then disturb the growth of calcite, and while proceed the crystal growth in a certain direction and promote the formation of aragonite. Also, a decrease of reaction rate by control the concentration of CO32- ion, induce the homogeneous precipitate reaction and increase substitution ability of Na+ ions, consequently it was promote the formation and growth of aragonite.
  • 7.

    Multi-scale simulation of drying process for porous materials using molecular dynamics (part 1 : homogenization method)

    오진원 | Young Tag Keum | 백성민 | 2004, 14(3) | pp.115~122 | number of Cited : 0
    Abstract PDF
    When porous materials are dried, the particles flocculate into fish-net structure in gel phase. In order to exactly analyze the stress distribution of porous materials during drying process, the elastic tensor of microscopic gel tructures has to be predicted considering pore shapes as well as porosities of porous materials. The elastic characteristics of porous materials associated with porosities were predicted analyzing microscopic gel structures with circular and cross pores via homogenization method and the drying processes of the lectric porous ceramic insulator were simulated using finite element method (FEM). Comparing analysis results between consideration and negligence of pores, the deformed shape and distributions of temperature and moisture were similar but the residual stress was significantly different0
  • 8.

    Effects of B2O3 composition for the photoluminescence and after-glow charcteristics of SrAl2O4:Eu+2, Dy+3 phosphors

    Young-Ki Lee | 엄기석 | 2004, 14(3) | pp.123~128 | number of Cited : 0
    Abstract PDF
    Both photoluminescence and the long-phosphorescent properties for SrAl2O4 : Eu+2,Dy+3 phosphor powder synthesized by the solid phase reaction were investigated as a function of B2O3 composition (0~10 wt%). The highest emission wavelength (520 nm) of photoluminescence spectra was not affected by B2O3 concentration. The highest emission intensity was obtained by the concentration of 3 wt% B2O3. After the removal of the Xenon lamp excitation (360 nm), also, the excellent long-phosphorescent property of the phosphors was obtained by the concentration of 3 wt% B2O3, although the decay times for all phosphors decreased exponentially.