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졸-겔법으로 성장시킨 바나듐이 도핑된 ${Bi_4}{Ti_3}{O_{12}}$ 박막의 미세구조 및 전기적 특성
김종국,김상수,최은경,김진흥,송태권,김인성,Kim, Jong-Guk,Kim, Sang-Su,Choe, Eun-Gyeong,Kim, Jin-Heung,Song, Tae-Gwon,Kim, In-Seong 한국재료학회 2001 한국재료학회지 Vol.11 No.11
$Bi_{3.99}Ti_{2.97}V_{0.03}O_{12}$ (BTV) thin films with 3 mol% vanadium doping were Prepared on $Pt/Ti/SiO_2/Si$ substrate by sol-gel method. X-ray diffraction analysis indicated that single-phase layered perovskite were obtained and preferred orientation was not observed. Under the annealing temperature at $600^{\circ}C$, the surface morphology of the BTV thin films had fine-rounded particles and then changed plate-like at $650^{\circ}C$ and $700^{\circ}C$. The remanent polarization $(2P_r)$ and coercive field $(2E_c)$ of $700^{\circ}C$ annealed BTV thin film were 25 $\mu$C/cm$^2$ and 116 kV/cm, respectively. In addition, BTV thin film showed little polarization fatigue during $10_9$ switching cycles. These improved ferroelectric properties were attributed to the increased rattling space and reduced oxygen vacancies by substitution $Ti^{4+}$ ion (68 pm) with smaller $V^{5+}$ ion (59 pm). The dielectric constant and loss were measured 130 and 0.03 at 10 kHz, respectively.
Nylon 6/Polypropylene 블렌드의 충격특성 및 모폴로지
김종국,윤주호,고재송,최형기,김상욱,Kim, Jong-Guk,Yun, Ju-Ho,Go, Jae-Song,Choe, Hyeong-Gi,Kim, Sang-Uk 한국재료학회 2002 한국재료학회지 Vol.12 No.1
Melt blends of maleic anhydride grafted polypropylerle(PP-g-MA) and Nylon 6 were prepared to study the influence of chemical reaction between the two polymer components. By adding the MA grafted polystyrene pold (ethylene/butadiene) and polystyrene[SEBS-g-MA] as the compatible modifiers to reinforce the impact resistance, the Izod impact strength, high rate impact strength and morphology were studied. The notched Izod impact strength increased with the content of PP-g-MA and SEBS- g-MA. The energy of high rate impact strength increased as the thickness of specimen increased, while, it increased as the specimen displacement decreased. In the morphology observed by SEM, finally, we confirmed the improvement of the compatibilization and interfacial adhesion with the content of SEBS-g-MA. The continuous phase of PP-g-MA was the main cause of the modified properties.
비정질 다이아몬드 코팅을 위한 자장여과 아크소스의 동작 특성에 관한 연구
김종국,이구현,kim, Jong-Guk,Lee, Gu-Hyeon 한국기계연구원 2000 硏究論文集 Vol.30 No.-
The filtered vacuum arc source (FVAS), which is adopted by magnetic filtering methode to remove the macro-particle in vacuum arc plasma, was composed of a torus structure with bending angle of 60 degree. The radius of torus was 266 mm, the radius of plasma duct was 80 mm and the total length was 600 mm. The magnet parts were consisted of one permanent magnet, one magnetic yoke and five solenoid magnets. The plasma duct was electrically isolated from the ground so that a bias voltage could be applied. The baffles inside plasma duct were installed in order to prevent the recoil effect of macro-particles. Graphite was used as the cathode material to coat the amorphic diamond film and its diameter was 80 mm. The amorphic diamond film attracts much attention due to its excellent mechanical, optical and tribological properties suitable for wide range of applications. The effects of solenoid magnet in plasma extraction were studied by computer simulation and experiment using Taguchi's method. The source and extraction magnet affected the arc stabilization. The extraction beam current was maximized with low value of the source magnet current and high value of the filtering magnet current. Optimum deposition condition was obtained when the currents of arc discharge, source, extraction, bending, deflection and outlet magnet were 30 A, 1 A, 3 A, 5 A, and 5 A, respectively.