• Journal of Food Hygiene and Safety
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• v.13 no.4
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• pp.344-354
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• 1998

This study was conducted to evaluate the MSPD and HPLC method about simultaneous determination for residual synthetic antimicrobials of sixteen species such as sulfonamide etc. in livestock products. Elution solvent used in HPLC was ethylacetate:acetonitrile (4:1), and mobile phases for solvent A and B were water:methanol:acetonit rile:phosphric acid (700:250:50:0.2) and 100% acetonitrile respectively. The detector and absorbency used in HPLC was UV 266 nm. This study showed the reduction effect of 99.1% for organic solvents, 94% for experimental steps, 95% for analytical time and manpower and 98.9% for costs compared with korea food standard method. The average recovery rates for chicken, bovine, pork and milk were 67.7% 96.2%, 67.7%~96.6%, 70.0%~96.2%, and 13.8%~97.8%.

• Journal of the Korean Ceramic Society
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• v.32 no.8
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• pp.909-914
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• 1995

From alumina powder and TEOS, $\alpha$-Al2O3/SiO2 composite powder for reaction-sintered mullite was synthesized by heterogeneous coagulation and surface coating, and investigated the mullitization reaction and sintering behavor of these powders. In $\alpha$-Al2O3/SiO2 composite powder prepared by heterogeneous coagulation, each alumina particles were surrounded by silica particles of 50~60 nm in size. And the alumina particles in composite powder prepared by surface coating were coated by uniform silica layer with thickness of 50 nm. In both methods, mullitization reaction was completed at 1$650^{\circ}C$ for 3h, and specimen sintered above 145$0^{\circ}C$ was about 95% fo the theoretical relative density. Mullite grains formed from the reaction with composite powders showed spherical shape with a size of 1~2${\mu}{\textrm}{m}$.

• Journal of the Korean Ceramic Society
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• v.50 no.3
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• pp.226-230
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• 2013

We performed high pressure high temperature (HPHT) sintering for the 20 nm MgO powders at the temperatures from $600^{\circ}C$ to $1200^{\circ}C$ for only 5 min under 7 GPa pressure condition. To investigate the microstructure evolution and physical property change of the HPHT sintered MgO samples, we employed a scanning electron microscopy (SEM), density and Vickers hardness measurements. The SEM results showed that the grain size of the sintered MgO increased from 200 nm to $1.9{\mu}m$ as the sintering temperature increased. The density results showed that the sintered MgO achieved a more than 95% of the theoretical density in overall sintering temperature range. Based on Vickers hardness test, we confirmed that hardness increased as temperature increased. Our results implied that we might obtain the dense sintered MgO samples with an extremely short time and low temperature HPHT process compared to conventional electrical furnace sintering process.

• Journal of the Optical Society of Korea
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• v.4 no.1
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• pp.7-10
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• 2000

The soft x-ray(10nm-100nm) interferometer is a modified Mach-Zehnder type interferometer and it consists of two beam-splitters and four totally reflecting mirrors. The beam-splitters used here are 50% transmission and 50% reflection grating type. The diffraction patterns of beam splitters(1st B.S.) were investigated with a He-Ne laser. The diffraction patterns produced by the soft x-ray interferometer (2nd B.S.) were also investigated in intensities positions. The diffraction patterns of 20 degree grazing incidence on the beam splitters(1st B.S.) show a circular array of spots. Both the reflected and the transmitted beams show the same patterns but symmetric circles on the screen. The maximum intensity appears roughly when n is in the zeroth and odd orders and the suppressed peak(missing order) appears when n is in even orders. Intensities of 3 center fringes(n = 0, $\pm$1) are stronger than others. These results confirm the reduced grating equation and make agree with the intensity distribution function. It was found that the final patterns produced by the soft x-ray interferometer (2nd B.S.) consisted of fine fringes which were caused by two of three diffraction beams that were arrived at the second beam-splitter.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.234-234
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• 2011

IGZO 투명 전도 박막은 TFT-LCD에 사용되는 투명 전도성 산화물 박막으로서 다양한 광전자 소자의 투명 전극으로 널리 사용되고 있다. 본 연구에서는 RF magnetron sputtering법으로 corning 1737 유리기판 위에 RF 파워의 변화에 따라 증착한 IGZO박막의 광학적 전기적 특성 변화를 연구하였다. 박막 증착 조건은 초기 압력 $2.0{\times}10^{-6}$ Torr, 증착 압력 $2.0{\times}10^{-2}$ Torr, 반응가스 Ar 50 sccm, 증착 온도는 실온으로 고정하였으며, 공정변수로 RF 파워를 25 w, 50 w, 75 w, 100 w로 변화시키며, IGZO 타겟은 $In_2O_3$, $Ga_2O_3$, ZnO 분말을 각각 1 : 1 : 2 mol% 조성비로 혼합하여 소결한 타겟을 사용하였다. 표면분석(AFM)결과 RF 파워가 증가함에 따라 거칠기가 증가하였으며, XRD 분석결과 Bragg's 법칙을 만족하는 피크가 나타나지 않는 비정질 구조임을 확인할 수 있었다. 가시광 영역에서 (450 nm~700 nm) 25 w일 때 85% 이상을 확인하였고, RF 파워가 증가할수록 밴드갭이 감소하는 것을 확인하였다. RF 파워가 100 w인 경우 carrier 밀도는 $7.0{\times}10^{19}\;cm^{-3}$, Mobility 13.4 $cm^2$/V-s, Resistivity $6.0{\times}10^{-3}\;{\Omega}-cm$로 투명전도막의 특성을 보였다.

• Korean Journal of Materials Research
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• v.13 no.9
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• pp.631-634
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• 2003

To fabricate W-Cu nanocomposite powder, $WO_3$-CuO powder mixture was high-energetically ball-milled and subsequently hydrogen-reduced. The effect of ball-milling on the hydrogen-reduction behavior of$ WO_3$-CuO was investigated with non-isothermal hygrometric analysis during hydrogen-reduction. Increasing the ball-milling time, the reduction peak temperatures of humidity curves were shifted to low temperature. It was considered that the reduction temperature should be decreased because the specific surface area of each oxide considerably increased with increasing the ball-milling time. In case of ball-milling for 0 h, $WO_3$and CuO were independently hydrogen-reduced and W particles were nucleated on the surface of Cu adjacent to W by CVT. However, in case of ball-milling for 50 h, the aggregates of about 200-300 nm were observed. W particles of size below 30-50 nm were homogeneously distributed with Cu in the aggregates.

• Journal of the Korean institute of surface engineering
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• v.36 no.5
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• pp.418-422
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• 2003

평판형 유도결합 플라즈마 식각장비(inductively coupled plasma etcher)를 이용하여 각종 공정조건들에 따른 GaAs의 식각특성을 연구하였다. 공정변수들은 ICP 소스파워(0-500 W), RIE 척파워(0-150 W), 가스 종류($BCl_3$, $BCl_3$/Ar, $BCl_3$/Ne) 및 가스혼합비였다. $BCl_3$ 가스만을 이용하여 GaAs를 식각한 경우보다 25%의 Ar이나 Ne같은 불활성 기체를 혼합한 $15BCl_3$/5Ar, $15BCl_3$/5Ne 가스를 이용한 경우의 식각률이 더 우수한 것을 확인하였다. 그리고 50% 이하의 Ar이 혼합된 $BCl_3$/Ar의 경우는 높은 식각률 (＞4,000 $\AA$/min)과 평탄한 표면(RMS roughness : ＜2 nm)을 얻을 수 있었지만 지나친 양(＞50%)의 Ar의 혼합은 오히려 표면을 거칠게 하거나 식각률을 떨어뜨리는 결과를 가져왔다. 그리고 20 sccm $BCl_3$, 100 W RIE 척파워, 300 W ICP 소스파워, 공정압력이 7.5 mTorr인 조건에서의 GaAs의 식각결과는 아주 우수한 특성(식각률: ∼ 4,000, $\AA$/min, 우수한 수직측벽도: ＞$87^{\circ}$, 평탄한 표면: RMS roughness : ∼0.6 nm)을 나타내었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.103-106
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• 2002

We prepared $Co_{77}Cr_{20}Ta_{3}$ thin film with Facing Targets Sputtering Apparatus. which can deposit a high quality thin film CoCrTa magnetic layer for Perpendicular magnetic recording media. In order to obtain Good Crystal orientation of CoCrTa thin films. We prepared Thin Films on slide glass substrate. The thickness of Buffer-layer were varied from 10 to 50 nm and Magnetic layer thickness fixed 100[nm]. input current was varied from 0.2[A] to 0.5[A]. Substrate temperature was varied from room temperature to ${250^{\circ}C}$ respectively. The crystal orientation of the CoCrTa film were examined with XRD. Introduce Buffer-layer thin films showed improvement of dispersion angle of c-axis orientation (${\Delta\theta}_{50}$).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.47-50
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• 2002

ZnO nanowires were coated conformally with aluminum oxide ($Al_{2}O_{3}$) material by atomic layer deposition (ALD). The ZnO nanowires were first synthesized on a Si (100) substrate at $1380^{\circ}C$ from ball-milled ZnO powders by a thermal evaporation procedure with an argon carrier gas without any catalysts; the length and diameter of these ZnO nanowires are $20\sim30{\mu}m$ and $50{\sim}200$ nm, respectively. $Al_{2}O_{3}$ films were then deposited on these ZnO nanowires by ALD at a substrate temperature of $300^{\circ}C$ using trimethylaluminum (TMA) and distilled water ($H_{2}O$). Transmission electron microscopy (TEM) images of the deposited ZnO nanowires revealed that 40nm-thick $Al_{2}O_{3}$ cylindrical shells surround the ZnO nanowires.

• Korean Journal of Materials Research
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• v.15 no.8
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• pp.548-553
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• 2005

Trivalent cerium$(Ce^{3+})$ activated YAG (yttrium aluminum garnet, $Y_3Al_5O_{12})$) thin films phosphor were deposited on quartz glass substrates by rf magnetron sputtering. The effects of sputtering parameters, annealing atmosphere, and substrates on growing behaviors and luminescent properties were investigated. The sputtering parameters were $O_2/(Ar+O_2)$ gas ratio, rf power, and deposition time. XRD (X-ray diffractometery) spectra exhibited that as-deposited films were amorphous, while they were transformed to the crystalline phases by post-annealing. The crystallinity and the atomic ratio strongly depended on the sputtering gas ratio $O_2/(Ar+O_2)$. High quality YAG:Ce thin films could be obtained at the gas ratio of $50\%$ oxygen. After annealing process, PL (Photoluminescence) spectra excited at 450nm showed a yellow single band at 550nm. The films deposited at the sputtering gas ratio of 50% oxygen exhibited the highest PL intensity.