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pISSN : 1225-1429 / eISSN : 2234-5078

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2016, Vol.26, No.6

  • 1.

    Vanadium-doped semi-insulating SiC single crystal growth by using porous graphite

    이동훈 | 김황주 | 김영곤 and 7other persons | 2016, 26(6) | pp.215~219 | number of Cited : 0
    Abstract PDF
    Vanadium-doped SiC crystals have been grown by using a porous graphite inner crucible filled with vanadium carbide (VC) and by using a porous graphite plate and SiC + VC powders, respectively. Semi-insulating SiC crystals were grown onto the 6H-SiC seed crystals by PVT (Physical Vapor Transport) method. The grown crystals were indicated to be 6H-SiC polytype by XRD. As result of SIMS analysis, vanadium-rich precipitates were observed when the vanadium concentration was relatively higher than the maximum solubility of vanadium (3-5 × 10 17 cm−3 ) in vanadium-doped SiC crystals, which resulted in degradation of crystal quality.
  • 2.

    Fabrication of anti-reflection thin film by using sol-gel hybrid solution

    박종국 | JISun Lee | LEE MI JAI and 3other persons | 2016, 26(6) | pp.220~224 | number of Cited : 0
    Abstract PDF
    Anti-reflection (AR) thin films were fabricated on a glass substrate by using an ultrasonic spray. Glycidoxypropyl trimethoxysilane (GPTMS) and tetraethyl orthosilicate (TEOS) were used to synthesize a sol-gel hybrid coating solution. The moving speed of spray nozzle was changed from 15~25 mm/s to control the coating thickness of AR thin film. As the moving speed of spray nozzle increased, the thickness of AR thin film decreased from 138 nm to 86 nm. When the AR thin film was fabricated by nozzle moving speed of 20 mm/s, the refractive index and thickness of AR thin film was measured to be 1.31 and 104 nm, respectively. The average reflectance and transmittance of AR thin film coating glass was measured to be 0.75 % and 94 %, respectively into the visible light range of 380~780 nm.
  • 3.

    Band alignments in Al-doped GaInAsSb/GaSb heterojunctions

    심규리 | 2016, 26(6) | pp.225~231 | number of Cited : 0
    Abstract PDF
    The valence band maximum (VBM) and conduction band minimum (CBM) of Al-doped GaInAsSb alloys substrated on GaSb are calculated by using an analytic approximation based on the tight binding method. The relative positions of the VBM and CBM between Al-GaInASSb and GaSb determine band alignement type, valence band offset (VBO) and conductin band offset (CBO) for the heterojunctions. In this study, aluminium doping is assumed to be substituted in the cation site and limited up to 20 % because it can easily oxidize and degrade materials. It is found that the Al-doped alloys exhibit type-II band alignments over the entire composition range and make the band gaps increase, whereas the VBO and CBO decrease. The decreasing rate of VBO is higher than that of CBO, which implies the Al components play a decisive role in controlling electrons at the interface. The Al-dopled GaInAsSb alloy has a direct band gap induced by E(Γ) with a considerable distance from the E(L) and E(X), however, E(Γ) approaches to E(L) and E(X) in the high Sb concentration (Sb > 0.7-0.8) which might affect the electron mobility and degrade the optical quality.
  • 4.

    Liquid-free milling to prepare a cocrystal of ibuprofen and nicotinamide

    함진옥 | 장지선 | 김일원 | 2016, 26(6) | pp.232~237 | number of Cited : 0
    Abstract PDF
    Cocrystallization of active pharmaceutical ingredients has been widely recognized as a versatile tool to regulate the physical properties of pharmaceutical compounds through designed crystal structures. Grinding or milling has been especially useful to screen the feasibility of cocrystal formation, and the addition of a small amount of liquid is routinely necessary. In the present study, the effect of temperature was studied for the milling cocrystallization of ibuprofen and nicotinamide to establish a liquid-free method. The milling-induced cocrystallization was more effective with liquid nitrogen cooling than at room temperature, which was confirmed by XRD and DSC analyses. This behavior was attributed to the limited molecular mobility below the glass transition temperatures of the cocrystal components, which made it effective to destruct the crystals of raw materials and consequently form the ibuprofen/nicotinamide cocrystal. Further studies would be necessary to establish the utility of the current conclusion to the field of pharmaceutical crystallization.
  • 5.

    The deactivation behavior of SCR catalyst by alkali and alkali earth metal

    한승윤 | Shin Min Chul | Lee, Hee-Soo | 2016, 26(6) | pp.238~242 | number of Cited : 0
    Abstract PDF
    The effect of the alkali, alkali earth metal elements on selective catalytic reduction(SCR) catalyst deactivation behavior were investigated in terms of microstructure, surface area, pore volume and De-NOx test. Poisoned SCR catalyst were manufactured by injection of K2CO3, Na2CO3, Ca(CH3COO)2 · H2O, C4H6MgO4 · 4H2O, H3PO4 solutions in the new SCR catalyst at 350 o C for 6 hours. New and poisoned catalysts surface were similar. But specific surface area, pore volume decrease from Na, Mg, K, Ca, P compared to new SCR catalyst. Especially, Na poisoned catalyst surface area and pore size extremely decreased by 10.20 m 2 /g, 0.061 cm 2 /g. De-NOx test results of new and poisoned catalysts at 150~450 o C indicated that alkali metal (K, Na) poisoned SCR catalysts have the lowest De-NOx efficiency, alkali earth metal poisoned SCR catalysts (Ca, Mg) De-NOx efficiency are higher than alkali metal poisoned SCR catalysts. P poisoned SCR catalyst De-NOx efficiency is similar new SCR catalyst. It were considered that physical deactivation of SCR catalyst was affected by SCR catalyst surface area and pore volume change.
  • 6.

    Preparation and characterization of silanized-hydroxypropyl methylcellulose/ phase transformed calcium phosphate composite bone cements

    정나현 | 김동현 | 조훈상 and 1other persons | 2016, 26(6) | pp.243~251 | number of Cited : 1
    Abstract PDF
    Silanized-hydroxypropyl methylcellulose (Si-HPMC)/phase transformed calcium phosphate (PTCP) composites are prepared to purpose application of injectable bone cements with enhanced biocompatibility. The crystal structure and chemical state of the synthesized PTCP and Si-HPMC as solid and liquid phase of the composite cements were measured by XRD and FT-IR. The handling and mechanical properties of cements were measured by injectability tests and threepoint bending tests. The in-vitro mechanical properties, XRD, and SEM results of bone cements were showed that enhanced hardening behavior was an inherent function of bone cements after in-vitro test. The cytotoxicity result of bone cements also was showed enhanced biocompatibility. Therefore, these injectable cements had potential be used as calcium phosphate cements for biomedical applications.
  • 7.

    FEM simulation on dust-collecting performance of tonpilz transducer using finite element method

    서진원 | Kyoon Choi | 이호용 | 2016, 26(6) | pp.252~257 | number of Cited : 1
    Abstract PDF
    Dust-collecting behavior of tonpilz transducer was simulated with finite-element-method (FEM) software. In order to optimize the performance of tonpilz transducer, the shape factors including the thickness of head mass, the diameter of tail mass and the depth of bolt were analyzed as variables. As a vibrating energy source, the piezoelectric materials was also tested with PZT-4 and two kinds of piezoelectric single crystals. The output power of the transducer was maximized with the shape factors and then the behavior of the dust-collection was demonstrated with the multi-physics software, COMSOL.
  • 8.

    Numerical analysis on foam reaction injection molding of polyurethane, part B: Parametric study and real application

    한혁수 | 남현남 | 은영기 and 5other persons | 2016, 26(6) | pp.258~262 | number of Cited : 0
    Abstract PDF
    Foam reaction injection molding (FRIM) is a widely used process for manufacturing polyurethane foam with complex shapes. The modified theoretical model for polyurethane foam forming reaction during FRIM process was established in our previous work. In this study, using the modified model, parametric study for FRIM process was performed in order to optimize experimental conditions of FRIM process such as initial temperature of mold, thickness of mold, and injection amount of polymerizing mixture. In addition, we applied the modified model to real application of refrigerator cabinet to determine optimal manufacturing conditions for polyurethane FRIM process.