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Mn-Zn 페라이트 다결정의 첨가물에 따른 초투자율의 변화 기구
변순천,변태영,고경현,홍국선,Byeon, Sun-Cheon,Byeon, Tae-Yeong,Go, Gyeong-Hyeon,Hong, Guk-Seon 한국재료학회 1997 한국재료학회지 Vol.7 No.9
52mol% Fe$_{2}$O$_{3}$, 26mol% MnO의 조성에서 calcium과 vanadium의 동시첨가에 의한 투자율의 변화원인을 살펴보았다. 초투자율은 첨가물의 농도가 커짐에 따라 감사하였으나 소결체의 밀도나 입자크기는 증가하였으므로 초투자율의 변화는 미세구조의 변화로는 설명되지 않았다. 전기비저항은 첨가물의 농도가 증가함에 따라 증가하였으며 이는 입계의 고저항층의 생성과 vanadium ion에 의한 Fe$^{2+}$이온의 산화로 설명되었다. 첨가물의 농도가 증가함에 따라, 초투자율의 제 2차 최대치가 나타나지 않는 것과 초투자율이 감소하는 것으로부터, 결정자기이방성 상수의 값은 음으로 커짐을 알 수 있었다. 투자육의 온도의존성과 비저항의 변화로부터, 첨가물의 농도에 따른 상온 초투자율의 감소는 Fe$^{2+}$ 이온 농도의 감소에 따른 결정자기이방성 상수의 증가에 의한 효과와 입계에 유리질이 생겨 자벽이 쉽게 이동하지 못하는 효과 때문인 것으로 판단되었다.
변순천,제해준,홍국선 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.5
Mn-Zn ferrite granules were prepared by spray drying of the slurry containing different kinds and concentration of binders at various spray drying temperatures and atomizing pressures. The characteristics of the spraydried granules were analyzed according to the processing variables of spray drying and the slurries containing different solid loading and kinds and concentration of binders. Typical shape of the spray dried granules was spherical. The granules spray dried at 15$0^{\circ}C$ were more spherical and containing lower hollow percentage than any other granules prepared at higher temperature. The granules prepared at higher atomizing pressures were more spherical and become smaller in size. The granules prepared using slurry containing higher solid loading were larger in size and less defective in shape. As increasing the concentration of binder the number of donut-shaped granules was increased and the size distribution become broader. The granules prepared using the slurry containing PVA 205 were more spherical than those containing PVA 217 and PVA 117. As the amount of granules which were donut-shaped or dimpled increased the compaction response were less effective. The hollows were not fractured completely even at hight pressures and remained after sintering.
Mn-Zn 페라이트 다결정의 조성에 따른 투자율의 변화 기구
변순천,제해준,고경현,홍국선 한국세라믹학회 1997 한국세라믹학회지 Vol.34 No.4
The origin of the variation of initial permeability in manganese-zinc ferrite polycrystals with a content of hematite was investigated. Initial permeability showed maximum with hematite content while there was no significant change in microstructure. Saturation magnetization increased with hematite content. So the variation of initial permeability was not explained on the basis of microstructural change or saturation magnetization. Temperature dependence of initial permeability revealed magnetocrystalline anisotropy was the origin of the variation of initial permeability. The change in magnetocrystalline anisotropy was ascribed to the variation in ferrous ion concentration. Therefore the variation of initial permeability in manganese-zinc ferrite polycrystals with a content of hematite was due to ferrous ion concentration via magnetocrystalline anisotropy.
결합제의 종류와 양에 따라 분무건조된 페라이트 분말의 성형특성
홍대영,변순천,제해준,홍국선 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.9
Mn-Zn ferrite granules were formed by a spray-drying method of the slurry containing different kinds and concentrations of binders at various temperatures. The slurry was made by conventional ceramic processing method, that is, by mixing Fe2O3, MnO, ZnO powders (52 : 24 : 24 mol%), calcining and milling. Typical shape of the spray dried granules was spherical. The compaction behavior of these granules was dependent on the spray-drying temperature and the kind and concentration of binders. At lower pressure the granules were displaced and at higher pressure the granules were deformed and fractured to fill pores among the granules. The optimum concentration of the binder was 0.5wt%. The granules containing 0.5wt% PVA 205 were deformed and fractured well and the green density was higher than others. At higher concentrations of the binder the granules were deformed rather than fractured, therefore the green density was lowered because of the remaining unfilled pores. The decomposition temperature and the heat released were increased with increasing the concentration of the binders. The compaction response of the granules containing PVA 205 was more efficient than those containing PVA 217 and PVA 117. Green density was not dependent on the degree of hydrolysis of the binders. The compaction response of the granules spray-dried at 15$0^{\circ}C$ was most efficient.
$Fe_2O_3$ 미량 변화에 따른 Mn-Zn 페라이트 단결정의 전자기적 특성
제해준,변순천,홍국선,장성도 한국세라믹학회 1993 한국세라믹학회지 Vol.30 No.10
The electro-magnetic properties of the Mn-Zn ferrite single crystal with small variation of Fe2O3 concentration at the high permeability composition, 53mol% Fe2O3-28.5mol% MnO-18.5mol% ZnO, have been studied for the VCR magnetic head application. With the increase of the Fe2O3 concentration, the Fe2+ concentration increased, the specific resistivity decreased, the secondary maximum permeability shifted to the lower temperature, and the initial permeability decreased. It was concluded that the small variation of $\pm$0.5mol% Fe2O3 concentration greatly affected the electro-magnetic properties of Mn-Zn ferrite single crystals. At the composition of 53mol% Fe2O3, the initial permeability was comparatively high (650 at 5MHz) and its temperature dependence was small.
한민규(Min-Kyu Han),김병수(Byoung Soo Kim),유지연(Jiyeon Ryu),변순천(Soon Cheon Byeon) 한국기술혁신학회 2010 기술혁신학회지 Vol.13 No.2
2008년 기술수준평가 대상기술 중 하나인 ‘바이오칩ㆍ센서기술’은 바이오 분야의 중점과학기술로서 세 가지 세부기술로 구성되어있다. 본 평가에서는 앞선 다른 수준평가의 한계를 극복하기 위하여 델파이와 함께 동태적 방법론(기술성장모형)을 분석틀로 사용하였다. 그 결과 바이오칩ㆍ센서기술은 ‘궁극의 기술’을 기준으로 한국 51.5%, 최고선진국(미국) 75.1%, 두 국가의 기술격차는 6.1년으로 분석되었으며, 5년 후에는 각각 60.1%, 78.4%, 4.3년이 될 것으로 예측되었다. 바이오 분야의 다른 기술과 비교했을 때, 해당 기술은 수준격차가 상대적으로 작았으며, 격차 역시 빠르게 좁혀질 것으로 나타났다. 이러한 특징은 세부기술 수준에서도 마찬가지였다. 설문 분석 결과 해당 기술의 강점은 전문인력 및 연구자금의 효과에 기인하는 것으로 나타났으며, 기초지원의 미비가 취약한 측면으로 지적되었다. 그 외에 이 기술이 상대적으로 신흥 분야이며, 집중적인 연구 활동이 이뤄지고 있다는 점 역시 높은 기술 수준의 요인으로 볼 수 있다. 따라서 바이오칩ㆍ센서 기술의 발전을 위해서는 이러한 강점을 더욱 지원하고, 약점을 보완하는 정책 방안이 필요할 것이다. In this paper, we analyze the result of the Technology Level Evaluation of ‘Biochip and biosensor (BB) Technology’ consisted of 3 sub-categorized technologies; biochip sensing (BS), lab on a chip and high-efficient customized health care technology. As an analysis tool, authors used a delphi (a repeated survey) and dynamic methodology with technology growth model to overcome limits of previous evaluations. As a result, levels of BB were evaluated 51.5% (Korea) and 75.1% (US), and the technology gap between two countries was 6.1 yrs. In 2013, these levels were expected to change to 60.1% (Korea), 78.4% (US) and 4.3 yrs, respectively. In comparison with other biotechnology, the gap of BB was smaller and expected to catch up with US faster. In the case of sub-categorized technologies, they showed the smallest gap and would have faster catch-up speed than other sub-categorized technologies in the Biotechnology field. Based on the result of the survey, relative superiority of BB in Korea was originated from competent researchers and research fund, but weak basic science would be weak points. We think that BB’s characteristic as an emerging technology and concentrated research activities on BB are additional strong points. This research proposes the supporting and supplemented points to promote the BB in Korea.