• 열처리공학회지
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• 제14권5호
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• pp.292-296
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• 2001

In this work, an ultra-high vacuum activated reactive evaporation equipment was built. With reaction of Al and oxygen plasma, $Al_2O_3$ was deposited on the surface of etched Al foil. The chamber was evacuated down to $2{\times}10^{-7}$ torr initially. The Ar and $O_2$ gas introduced into the chamber to maintain $5{\times}10^{-5}$ torr during deposition. Ar gas prevents recombining of the ionized oxygen. Evaporation was maintained by electron beam evaporator continuously. Heating filament and electrode were used in order to generate plasma. The substrate bias of -300V was introduced to accelerate deposition of evaporated Al atoms. The composition and morphology of deposited $Al_2O_3$ films were analyzed by x-ray photoelectron spectroscopy(XPS) and atomic force microscopy (AFM), respectively. The Al oxide was formed on the surface of etched Al foil. According to AFM results, the surface morphology of $Al_2O_3$ film indicates uniform feature. Dielectric characteristic was measured as a function of frequency. Measured withstanding voltage and capacitance were 52V and $24{\mu}F/cm^2$, respectively. The obtained $Al_2O_3$ film shows clean condition without contaminants, which could be adapted to capacitor production.

• Carbon letters
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• 제18권
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• pp.37-42
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• 2016

Graphene was grown on molybdenum (Mo) foil by a chemical vapor deposition method at different growth temperatures (1000℃, 1100℃, and 1200℃). The properties of graphene were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and Raman spectroscopy. The results showed that the quality of the deposited graphene layer was affected by the growth temperature. XRD results showed the presence of a carbide phase on the Mo surface; the presence of carbide was more intense at 1200℃. Additionally, a higher I_2D/I_G ratio (0.418) was observed at 1200℃, which implies that there are fewer graphene layers at this temperature. The lowest I_D/I_G ratio (0.908) for the graphene layers was obtained at 1200℃, suggesting that graphene had fewer defects at this temperature. The size of the graphene domains was also calculated. We found that by increasing the growth temperature, the graphene domain size also increased.

• 한국광학회:학술대회논문집
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• 한국광학회 1988년도 광학 및 양자전자학 워크샵
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• pp.135-144
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• 1988

1-GW Iodine photodissociation Laser (λ=1.315${\mu}{\textrm}{m}$)is focused to generate the continuum x-ray radiation at titanium(z=22)target. A piced of aluminum(360 )-mylar(8${\mu}{\textrm}{m}$) film is used to isolate the soft X-ray radiation emitted. Convex-xurved mica crystal spectrometer is used to obtain the soft x-ray spectra from the laser titanium target plasma and the slope of continum X-ray spectra are found to show two different different electron effective temperaturres, 0.11keV and 7.1KeV. We compare the two temperature result with the foil absorption method.

• Tribology and Lubricants
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• 제35권2호
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• pp.114-122
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• 2019

High-speed rotating machinery requires low cost and reliable bearing elements with low friction, stable rotordynamic characteristics, and a simple design. This study experimentally evaluates the effects of bearing-support elements on the vibrational characteristics of a small-sized, high-speed permanent magnetic motor. A series of coast down tests from 100 krpm characterize the vibrational behaviors, rotor displacement, and housing acceleration of motors supported by ball bearings, ball bearings with a metal mesh damper, and gas foil bearings, respectively. Two eddy-current sensors installed in the horizontal and vertical directions measure the displacement of the rotor at its front nut, and a 3-axis accelerometer attached to the motor housing measures the housing acceleration. The test results reveal that synchronous (1X) vibration components most significantly affect the rotor displacement and housing acceleration, independent of the bearing-support elements. The motor supported by the deep-groove ball bearings results in the largest rotor vibrations increasing with speed; this is due to the absence of a damping mechanism. Additionally, the metal mesh damper effectively reduces the rotor displacement, housing acceleration, and sound-pressure level in the high-speed region (i.e., above 40 krpm), thus implying its substantial damping performance when installed on the outer race of the ball bearing. Lastly, the gas foil bearing supported motor yields the smallest rotor displacement, housing acceleration, and lowest sound-pressure level because of its hydrodynamic airborne operation, which does not require rolling elements that may cause mechanical friction and vibrations.

• 한국산학기술학회논문지
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• 제20권6호
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• pp.80-85
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• 2019

이산화바나듐은 잘 알려진 금속-절연체 상전이 물질이며, 바나듐 레독스 흐름 전지는 대규모 에너지 저장장치로 활용하기 위해서 많은 연구가 이루어져왔다. 본 연구에서는 바나듐 옥사이드 ($VO_x$) 박막을 리튬이온 이차전지의 양극으로 적용하는 연구를 수행하였다. 이를 위해서 $VO_x$ 박막을 실리콘 웨이퍼 위에 열산화공정으로 300 nm 두께의 $SiO_2$ 층이 형성된 Si 기판 및 쿼츠 기판 위에 RF 마그네트론 스퍼터 시스템으로 60분 동안 $500^{\circ}C$에서 다른 RF 파워로 증착하였다. 증착된 $VO_x$ 박막의 표면형상을 전계방출 주사전자현미경으로 조사하였고, 결정학적 특성을 Raman 분광학으로 분석하였다. 투과율 및 흡수율과 같은 광학적 특성은 자외선-가시광선 분광계로 조사하였다. Cu Foil 위에 증착된 $VO_x$ 박막을 리튬이온전지의 양극물질로 적용하여 CR2032 코인셀을 제작하였고, 전기화학적 특성을 조사하였다. 그 결과 증착된 $VO_x$ 박막은 RF 파워가 증가할수록 낟알 크기가 증가하였고, RF 파워 200 W 이상에서 증착된 박막은 $VO_2$상을 나타내었다. 증착된 $VO_x$ 박막의 투과율은 결정상에 따라 다른 값을 나타내었다. $VO_x$ 박막의 이차전지 특성은 높은 표면적을 가질수록, 결정상이 혼재될수록 높은 충방전 특성을 나타내었다.

• 한국자기학회지
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• 제9권4호
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• pp.190-195
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• 1999

최대 출력 3.5kW인 고주파에 의한 알곤 플라즈마 분위기에서 제작한 Fe1-xCox(x=0.2와 0.4)계와 25$\mu\textrm{m}$의 철 박막의 자기적인 성질을 상온에서의 X선 회절과 진동시료자력계를 이용한 자기이력곡선 측정 방법을 사용하여 연구하였다. arc로에서 제작된 시룐느 삼단계 처리 가공하였다. 첫째는 수압기로 9,000N/$\textrm{cm}^2$의 압력을 가하여 알약 형태로 만들었다. 이 단계는 압연기로 눌러 얇은 sheet로 만들었다. 삼단계는 시료는 질소 가스 분위기에서 90$0^{\circ}C$로 열처리하였다. 일단계 시료의 X선 회절결과는 시료가 균질이며 각 시료는 철과 동일한 bcc 결정구조를 갖는 단일결저상(single crystal phase)임을 보였다. 철 박막은 43 Oe의 항자력과 인가자기장에 대한 자화, 즉 초기 기울기는 0.328 emu/gOe를 나타냈다. 이단계 시료에서는 Co량이 증가함에 따라 항자력과 포화자화값은 증가하였다. 반면 초기 기울기는 감소하였다. 이는 항자력의 증가로 인해서 계면이동이 억제되었음을 의미한다. 삼단계 시료에서 두 시료 모두 포화자화값은 증가하였다. 반면 이들 시료의 항자력은 감소하였다. 3단계 시료의 포화자화의 열처리로 인한 시료의 X선 회절강도 변화와 연관이 있어 보인다. 또한 몇 개의 자기 매개변수를 단순모형을 써서 계산하여 다른값과 비교하였다.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.525-532
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• 2016

High-energy linear accelerators are increasingly used in the medical field. However, the unwanted photo-neutrons can also be contributed to the dose delivered to the patients during their treatments. In this study, neutron fluxes were measured in a solid water phantom placed at the isocenter 1-m distance from the head of an18-MV linac using the foil activation method. The produced activities were measured with a calibrated well-type Ge detector. From the measured fluxes, the total neutron fluence was found to be $(1.17{\pm}0.06){\times}10^7n/cm^2$ per Gy at the phantom surface in a $20{\times}20cm^2$ X-ray field size. The maximum photo-neutron dose was measured to be $0.67{\pm}0.04$ mSv/Gy at $d_{max}=5cm$ depth in the phantom at isocenter. The present results are compared with those obtained for different field sizes of $10{\times}10cm^2$, $15{\times}15cm^2$, and $20{\times}20cm^2$ from 10-, 15-, and 18-MV linacs. Additionally, ambient neutron dose equivalents were determined at different locations in the room and they were found to be negligibly low. The results indicate that the photo-neutron dose at the patient position is not a negligible fraction of the therapeutic photon dose. Thus, there is a need for reduction of the contaminated neutron dose by taking some additional measures, for instance, neutron absorbing-protective materials might be used as aprons during the treatment.

• 한국산학기술학회논문지
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• 제20권2호
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• pp.638-643
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• 2019

자동차 소프트 인스트루먼트 패널의 비용과 중량을 줄이기 위하여 두 가지 사출을 동시에 수행하는 방법을 이용한 새로운 인스투르먼트 패널이 개발되었다. 첫 번째 사출은 뒷면 발포체 포일을 삽입하는 압축 사출을 하는 방법이고, 다른 하나는 동승석 에어백에 도어와 동시에 2샷 사출하는 방법이다. 우리는 그것을 'IMX-IP'라고 부르며, 이것은 인스트루먼트 패널의 모든 부품들이 종류가 다른 수지와 하나의 금형 안에서 만들어지는 방법인 것이다. 본 기술의 개발 과정은 (1) TRIZ 기법을 이용한 새로운 사출 금형 설계, (2) 사출 조건의 최적화와 폼의 손실과 두께 편차를 최소화하기 위한 뒷면 발포체 포일의 최적화, (3) 2샷 사출 압축에 대한 CAE 해석 검증, (4) 신뢰성 검증 시험과 양산에의 적용 순서로 이루어져 있다. 뒷면 발포체 포일 삽입을 이용한 2샷 사출을 통한 공정 감소는 개발비와 중량 절감과 함께 소프트 인스투루먼트 패널의 부드러운 느낌을 향상시키는 것을 가능하게 하였다.

• 대한금속재료학회지
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• 제47권4호
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• pp.256-260
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• 2009

This study examined the effects of plated temperature on the surface morphology and property of an electrodeposited copper foil. The morphology, crystal structure and electric characteristics of the electrodeposited copper foil were examined by scanning electron microscopy, X-ray diffraction, and a four-point probe, respectively. The surface roughness, crystal growth orientation and resistivity could be controlled using various temperature of electrolyte. Large particles were observed on the surface of the copper layer electroplated onto the $30^{\circ}C$. However, a uniform surface, lower resistivity and high flexibility were obtained when a $50^{\circ}C$ electrolyte was used.

• 한국표면공학회지
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• 제47권1호
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• pp.1-6
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• 2014

The copper deposit on steel plate was prepared by pyrophosphate copper plating solution made with variation of inorganic additive. $NH_4OH$ and $NH_4NO_3$ were used as inorganic additives. The copper layer characteristics - tensile strength, crystallite size and crystal orientation - were evaluated by X-ray diffraction and Universal Test Machine. The presence of ammonium nitrate results in reduction of average roughness value from $0.08{\mu}m$ to $0.03{\mu}m$. In pyrophosphate copper plating solution without Inorganic additive, tensile strength of electrodeposit copper foil was reduced from 600 MPa to 180 MPa after 7 days aging. However, when adding ammonium nitrate, there was almost no change of tensile strength, intensity of crystal orientation - (111), (200) and (220) - and crystallite size (2~30 nm).