• 한국초전도ㆍ저온공학회논문지
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• 제17권4호
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• pp.38-42
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• 2015

In terms of food safety,mixture of contaminants in food is a serious problem for not only consumers but also manufacturers. In general, the target size of the metallic contaminant to be removed is 0.5 mm. However, it is a difficult task for manufacturers to achieve this target, because of lower system sensitivity. Therefore, we developed a food contaminant detection system based on high-Tc RF superconducting quantum interference devices (SQUIDs), which are highly sensitive magnetic sensors. This study aims to improve the signal to noise ratio (SNR) of the system and detect a 0.5 mm diameter steel ball. Using a real time digital signal processing technique along with analog band-pass filters, we improved the SNR of the system. Owing to the improved SNR, a steel ball with a diameter as small as 0.3 mm, with stand-off distance of 117 mm was successfully detected. These results suggest that the proposed system is a promising candidate for the detection of metallic contaminants in food products.

• Progress in Superconductivity
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• 제14권2호
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• pp.82-86
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• 2012

A sensitive eight-channel high-Tc Superconducting Interference Device (SQUID) detection system for magnetic contaminant in a lithium ion battery anode was developed. Finding ultra-small metallic foreign matter is an important issue for a manufacturer because metallic contaminants carry the risk of an internal short. When contamination occurs, the manufacturer of the product suffers a great loss from recalling the tainted product. Metallic particles with outer dimensions smaller than 100 microns cannot be detected using a conventional X-ray imaging system. Therefore, a highly sensitive detection system for small foreign matter is required. We have already developed a detection system based on a single-channel SQUID gradiometer and horizontal magnetization. For practical use, the detection width of the system should be increased to at least 65 mm by employing multiple sensors. In this paper, we present an 8-ch high-Tc SQUID roll-to-roll system for inspecting a lithium-ion battery anode with a width of 65 mm. A special microscopic type of a cryostat was developed upon which eight SQUID gradiometers were mounted. As a result, small iron particles of 35 microns on a real lithium-ion battery anode with a width of 70 mm were successfully detected. This system is practical for the detection of contaminants in a lithium ion battery anode sheet.

• Current Photovoltaic Research
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• 제6권1호
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• pp.17-20
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• 2018

The dependency of the photovoltaic performance of p-/n-type silicon solar-cells on the metallic contaminant type (Fe, Cu, and Ni) and concentration was investigated. The minority-carrier recombination lifetime was degraded with increasing metallic contaminant concentration, however, the degradation sensitivity of recombination lifetime was lower at n-type than p-type silicon wafer, which means n-type silicon wafer have an immunity to the effect of metallic contamination. This is because heavy metal ions with positive charge have a much larger capture cross section of electron than hole, so that reaction with electrons occurs much more easily. The power conversion efficiency of n-type solar-cells was degraded by 9.73% when metallic impurities were introduced in the silicon bulk, which is lower degradation compared to p-type solar-cells (15.61% of efficiency degradation). Therefore, n-type silicon solar-cells have a potential to achieve high efficiency of the solar-cell in the future with a merit of immunity against metal contamination.

• 월간포장계
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• 통권248호
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• pp.64-67
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• 2013

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1887-1889
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• 2002

One of the most frequent sources of the accident is metal contaminant in GIS. This paper deals with the characteristics of breakdown voltage of metallic particles using electrodes of various epoxy coating thickness. As experimental results, breakdown voltage of the thickly coated electrode is higher than that of thinly coated electrode. It is considered that resistance of the epoxy coating impedes the development of pre-discharges in the gas.

• 한국응용과학기술학회지
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• 제32권1호
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• pp.23-30
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• 2015

The properties of dust collected from electric arc furnace of ferro manganese production units was investigated, and also the metallic manganese was recovered from the dust by aluminothermy process. The ferromanganese dust collected from electric arc furnace contained about 15% of manganese oxide ($Mn_3O_4$) and 9% of carbon as the contaminant, and have a 5um of 50% median diameter and irregular particle shape. The carbon contaminant in the dust could be reduced until about 0.1~0.5% level by roasting in the air at a temperature of 600~900C for 60minutes. The recovery of manganese could not be carried out using only ferromanganese dust from electric arc furnace by aluminothermy process, but the ferromanganese which contained manganese of about 92% and iron of about 5% could be obtained from the mixture of ferromanganese dusts from electric arc furnace and converter. The best mixing condition of dust fixed at electric arc furnace dust / converter dust ratio of 1:9 and 2:8, and the mixing rato of 3:7 or more could not separated the metal and slag from the reactant after aluminothermy reaction.

• 한국재료학회지
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• 제9권5호
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• pp.491-495
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• 1999

In this study, we focus on Ca contaminant which affects on the roughness Si substrate after thermal process. The initial Si substrates were contaminated intentionally by using a standard Ca solution. The contamination levels of Ca impurity were measured by TXRF and the chemical composition of that was analyzed by AES. Then we gre the thermal oxide to investigate the effect of Ca contaminants. The microroughness of the Si surface, the thermal oxide surface, and the surface after removing the thermal oxide were measured to examine the electrical characteristics. The initial substrates that were contaminated with the standard solution of Ca exhibited the contamination levels of 10\ulcorner~10\ulcorneratoms/$\textrm{cm}^2$ which was measured by TXRF. The Ca contaminants were detected by AES and exhibited the peaks of Ca, SI, C and O.After intentional contamination, the surface microroughness of this initial substrate was increased from $1.5\AA$ to 4$\AA$ as contamination levels became higher. The microroughness of the thermal oxide surfaces of both contaminated and bare Si substrates exhibits similar values. But the microroughness of the contaminated$ Si/SiO_2$ interface was increased as contamination increased. The thermal oxide of contaminated substrate exhibited the small minority carrier diffusion length, low breakdown voltage, and slightly high leakage current.

• 보존과학회지
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• 제38권3호
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• pp.243-253
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• 2022

본 연구에서는 청송심씨묘 출토 금직물 유물 2점(부금 원삼, 직금 치마)에 대한 비파괴 분석방법을 이용하여 유물 상태, 섬유 재질, 표면 오구(汚垢), 금속사에 대한 재료적 특성을 파악하였다. 출토 당시 유물의 상태는 모두 갈변되어 본래의 색상을 확인할 수 없으며, 섬유재질은 SEM과 FT-IR의 Amide I, II, III, IV 피크와 정색 반응 결과들로 누에고치로부터 얻은 견 섬유임을 확인할 수 있었다. 표면 오염물인 흰색 오구와 검정색 오구는 FT-IR, XRF 분석결과 시신의 부패와 미생물 분해로 나타난 지방질, 단백질 등의 가수분해 물질임을 확인할 수 있었다. 금속사의 금박층을 XRF로 분석한 결과 금(Au)으로 확인되었으며, 금속사 배지에 대한 FT-IR, 정색 반응 결과 배지의 접착제 성분은 Amide I, II, III와 3000 cm^-1 전·후의 Amide A, B의 결과로 동물성 교(膠)로 확인되었고, 배지는 정색 반응 결과 국내에서 생산된 닥나무 인피 섬유인 한지로 확인할 수 있었다.

• 방사성폐기물학회지
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• 제6권1호
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• pp.17-23
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• 2008

이 연구에서는 플라즈마 제염 기술의 실용화를 위해 $CF_4/O_2$, $SF_6/O_2$, $NF_3$ 등의 반응성 플라즈마 기체를 이용하여 원자력 시설의 주요 오염원인 코발트 핵종에 대한 표면 제염 모의실험을 수행하였다. 디스크 형태의 금속코발트에 대하여 시편 표면 온도를 변수로 플라즈마 식각 실험을 수행한 결과 반응율은 $420^{\circ}C$에서 $NF_3$ 기체의 경우 $17.2\;{\mu}m/min.$ 그리고 $SF_6$와 $CF_6/O_2$ 기체의 경우 각각 $2.56\;{\mu}m/min.$과 $1.14\;{\mu}m/min.$이었으며, 이들 반응의 활성화에너지는 각각 39.4 kJ/mol, 42.1 kJ/mol, 116.0 kJ/mol이었다. 이와 함께 AES (Auger Electron Spectroscopy)를 이용하여 반응 생성물 성분 분석 결과 이들 반응의 주요 반응 기구는 코발트의 불화 반응임이 밝혀졌다. 이 연구를 통해 확보된 $17\;{\mu}m/min.$의 금속 표면 식각율은 주요 반도체 공정의 식각율을 뛰어넘는 높은 식각율로 플라즈마 제 염 기술의 실용화를 앞당길 수 있는 고무적인 결과라 할 수 있을 것이다.

• 한국진공학회지
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• 제11권2호
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• pp.87-96
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• 2002

위성체가 작동하는 우주환경인 고진공상태에서는 위성체의 부품에서 발생 할 수 있는 outgassing으로 인해 위성체가 오염되어 위성체의 성능이 저하될 수 있으며, 특히 이차면경(second surface mirror) 및 광학렌즈 등을 오염시킴으로써 위성체 본연의 임무수행 실패라는 결과를 초래할 수도 있다. 따라서 지상에서 위성체의 부품에 대해 고온($85^{\circ}C$ 이상)과 고진공($5.0\times10^{-3}$ Pa 이하)의 상태를 모사하여 오염물질을 제거함으로써 outgassing의 발생을 막고, 아울러 오염근원을 검출할 수 있는 vacuum bake-out 시험이 필수적이라 할 수 있다. 이를 위해서 한국항공우주연구원 우주시험동에 설치된 bake-out 챔버를 이용하여 위성체 부품 중에서 SAR(Solar Array Regulator)와 MLI(Multi Layer Insulator)를 예를 들어 오염측정에 관한 연구를 수행하였다. 항공우주연구원의 bake-out 챔버는 rotary vacuum pump와 booster pump를 이용하여 5.0 Pa의 저진공을 형성하고, 2대의 cryopump를 이용하여$5.0\times10^{-3}$ Pa 이하의 고진공을 생성하게 된다. 또한 $180^{\circ}C$까지의 고온을 모사하기 위하여 챔버 shroud 안쪽에 ceramic 재질로 된 heater가 $30^{\circ}$간격으로 총 48개를 설치되어 있으며, 온도제어는 PID(Proportional Integral Differential) 제어 방식이 이용되었다. Vacuum bake-out 시험시에는 RGA(Residual Gas Analyzer)를 이용하여 각종 오염물질을 검출할 수 있고, TQCM(Thermoelectric Quartz Crystal Microbalance)을 사용하여 발생하는 오염물질의 방출률(outgassing rate)을 측정한다. 또한 필요시에는 IR/UV Spectrometer를 이용하여 witness plate에 흡착된 오염물질의 성분을 분석하여 위성체 부품으로의 적합성을 판단한다. SAR의 bake-out에서는 TQCM 측정결과 오염물질이 시간에 따라 감소추이는 보이지만 꾸준히 배출되고 있는 경향을 나타내고, RGA 분석결과 그 성분이 고분자 화합물로 추정되어 위성체 부품으로 사용하기에는 적절하지 못할 것으로 판단하였다. MLI의 bake-out에서는 RGA 및 witness plate를 이용한 오염측정 결과 특이한 오염물질을 발견할 수 없었다.