Syntheses and Characterization of Co/Fe3O4 Nanocomposites by Polyol Process

오영우,고근호,박문수 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.4

Co, Fe3O4 and Co/Fe3O4 nanoparticles were synthesized by a polyol process in order to develop their new applications and improve chemical, magnetic properties. The synthesis involved a polyol process using Fe, Co acetylacetonate as precursors and 1-2 hexadecanediol as the polyol. The synthesized Fe3O4 and Co/Fe3O4 nanocomposite particles were monodispersed and self arrayed ranging in size of 8~10 and 10~25 nm, respectively. The Co nanoparticle has a crystallite size of 10~40 nm. The synthesized nanoparticles were characterized by their structural, morphological, compositional and magnetic properties using TEM-EDS, XRD, and PPMS techniques.

클라우드 기반의 SRM 시스템을 통한 효율적 기업전략구매 : SAP Ariba 솔루션 사례를 중심으로

오영우,박주석 차세대컨버전스정보서비스학회 2021 차세대컨버전스정보서비스기술논문지 Vol.10 No.3

Recently, major South Korean companies are rapidly shifting to strategic procurement through the introduction of cloud-based SRM (Supplier Relationship Management). SRM automates the process from sourcing to procurement across the supply base and strategically operates relationships with external suppliers to increase efficiency across the supply chain. This study explores the efficiency of strategic procurement that companies can acquire through the introduction of cloud-based SRM solution and we want to analyze a relevant case for companies that have deployed cloud-based SRM solutions. In this process, we studied the nature of the cloud and how key features of SRM solutions can enhance the change and efficiency of strategic procurement for companies. To this end the SAP Ariba Solution with the highest market share was analyzed. As a result, we confirm that the SAP Ariba deployment can help to maximize the instability and limitations of existing supply and demand and improve the procurement process to supply parts and optimize central purchasing and intelligent procurement process in a timely manner strategically. Based on the results of this study, we proposed strategy for utilization in building cloud SRM solutions and made suggestions for future research 최근 국내 주요 기업들은 클라우드 기반의 SRM(Supplier Relationship Management) 도입을 통해 기업 간 연계 중심의 전략구매로 빠르게 전환하고 있다. SRM은 공급기반 전반에 걸쳐 소싱에서 조달에 이르는 과정을 자동화하고 외부 공급사와의 관계를 전략적으로 운영하여 공급망 전체의 효율을 높이는 물류시스템이다. 본 연구는 클라우드 기반의 SRM 시스템 도입을 통해 기업이 획득할 수 있는 전략구매의 효율성을 탐색하는 연구의 일환으로서, 클라우드 기반의 SRM 솔루션 사례를 분석하였다. 이러한 과정에서 클라우드 SRM의 특성 및 주요 기능이 기업의 전략구매에 어떠한 변화와 효율성을 증진시킬 수 있는지를 검토하였다. 이를 위해 시장점유률이 가장 높은 SAP Ariba 사례를 분석하였고, 그 결과 표준화된 업무 프로세스를 통해 컴플라이언스 문제와 보안취약점 문제를 해결하고, 전략적으로 조달프로세스를 개선하여 중앙조달 구매체계 및 지능형 자율조달을 통한 기업전략구매 최적화에 기여할 수 있음을 확인했다. 마지막으로 본 연구결과에 근거하여 기업에서 클라우드 SRM솔루션의 구축시 활용 전략과 향후 연구를 위한 제언을 하였다.

非晶質 B₂O₃-BaO-Fe₂O₃系의 超急冷合成 및 磁氣特性

吳英佑 慶南大學校 附設 工業技術硏究所 1987 硏究論文集 Vol.5 No.-

새로운 응용이 기대되는 非晶質材料中 B₂O₃-BaO-Fe₃O₃系의 非晶質 酸化物磁性體를 자체 제작한 超急冷장치로서 제조하였으며, 이를 結晶化시켜 미세한 Ba-Ferrite 입자를 추출하였다. 이때 비정질체의 결정화는 DTA에서 복잡한 양상의 단계인 것이 확인되었다. 결정화 시편으로부터 추출된 Ba-Ferrite 미세입자는 균일한 크기를 가지며, 수직기록자기용 재료로서 가능성을 보여주었다. An amorphous caramics with composition 0.30B₂O₃-0.40BaO-0.30Fe₂O₃(mole%) was prepared by an ultra rapid-quenching technique. X-ray and electron diffraction reveal the product to be amorphous at room temperature. The crystallization, as shown by DTA studies, has complex steps and begins at 525℃ up to 820℃, a temperature at which BaFe??O?? is shown to be present, the crystallizing products are mainly evolutive. Fine particles of obtained BaFe??O?? have little size distribution and would be appreciated as perpendicular magnetic records.

Mn-Zn 페라이트의 입계 전기저항층 형성

오영우,김현식 경남대학교 신소재연구소 1996 論文集 Vol.7 No.-

Mn-Zn 페라이트 입계에 높은 전기 저항층을 형성해 전기 전도에 의한 손실을 감소시키는 것으로 알려진 CaO와 SiO_2를 복합적으로 첨가하여 미세구조와 물성에 대해 고찰하였다 SiO_2의 첨가량이 증가함에 따라 밀도는 증가하였으나, 과잉으로 첨가된 시편은 과대 입성장으로 인해 결정립 내부에 고립 기공을 형성시켜 밀도는 감소하였다. SiO_2의 첨가량에 따라 전기 비저항은 감소하는 경향을 나타내었다. 초기 투자율과 손실은 SiO_2를 200ppm 첨가하였을 때 가장 우수한 값을 나타내었다 The current experiment has quantitatively investigated the effect of the CaO+SiO₂on the microstructures and properties of Mn-Zn ferrites. The density was increased initially with SiO₂content. But increasing of SiO₂lowered the density and the electrical resistivity due to the developing the abnormal grain growth included numerous pores in it. The initial permeability and power loss showed the excellent values at 200ppm of SiO₂content.

한국의 온라인 저작권 정책

오영우 동국대학교 비교법문화연구원 2008 比較法硏究 Vol.9 No.1

Ni-Zn ferrite의 조성변화에 의한 물성[1] : Ni₁-xZnxFe₂O₄(x=0.45∼0.65)의 열처리 온도와 특성 Heating Temperatures and Properties of Ni₁-xZnXFe₂O₄(x=0.45∼0.65)

오영우 慶南大學校 附設 工業技術硏究所 1997 硏究論文集 Vol.14 No.2

비저항이 큰 고주파용 Ni-Zu ferrite를 합성할 경우 NiO와 ZnO의 몰비 변화와 하소온도 및 소결온도의 변화에 따른 ferrite의 물성을 조사하였다. Ni₁-xZnxFe₂o₄에서 x를 0.45에서 0.65의 범위로 하고, 하소온도는 750℃에서 50℃의 간격으로 950℃까지 5단계를 두었으며, 소결은 각각 1200℃와 1250℃로 하여 2시간 유지시켰다. Ni-Zn ferrite의 합성은 x=0.6, 하소온도 900℃에서 미반응의 Fe₂O₃가 존재하지 않았으며, 1250℃에서 소결시킨 시편이 1200℃에서 소결시킨 시편보다 K₁, 기공율 등의 원인으로 투자율값이 높고, 손실값이 작은 자기적 성질을 보였다. Magnetic properties, such as permeability, magnetic losses of Ni-Zn ferrite were investigated. The calcining temperatures were varied from 750℃ to 950℃, with the intervals of 50℃, and matured for 2 hrs. Mole ratio of Ni₁-xZnzFe₂O₄also varied from 0.45 to 0.65. As a result, mixed raw materials were synthesized Ni-Zn ferrite without unreacted Fe₂O₃at 900℃, x=0.6, and higher permeability and low losses were obtained from sintered specimen at 1250℃ than 1200℃ because of the higher K₁ and low porosity.

Cu 치환에 따른 Ni-Zn 페라이트의 전자파 흡수 특성

오영우,이선학,김종령,안용운,이승관 경남대학교 신소재연구소 2001 신소재연구 Vol.13 No.-

고상반응법을 이용하여 Ni_0.6-xCuZn_0.4Fe _2O_4(x=0, 0.1, 0.2, 0.3) ferrite 분말을 제조하고 1200℃에서 열처리하여 Cu 치환에 따른 입자변화와 전자파흡수 특성과의 관계를 조사하였다. Ni 자리에 Cu를 0.1mol 치환했을 때는 포화자화값은 큰 변화 없이 일정하였고 우수한 전자파습수능을 나타내었고, 그 이상 첨가 시는 포화자화값과 전자파흡수능은 직선적으로 감소하였다. Ni_0.6-xCuZn_0.4Fe _2O_4 ferrite powder was prepared by the solid-reaction method and sintered at 1200℃ and investigated grain size related with electromagnetic wave absorbing properties were investigated as a function of Cu substitution. The saturation magnetization and electromagnetic wave absorbing efficiency were rarely changed until substitution of Cu 0.1mol into Ni-site, but decreased strongly over 0.1mol Cu,

박막 인덕터와 제조와 DC-DC Converter에의 적용

오영우,민복기,송재성 경남대학교 신소재연구소 1999 論文集 Vol.11 No.-

Thin film inductors of 10 mm×10 mm with inner coil type of 5 turns were fabricated by sputtering, photo-masking, and etching processes. The inductor has an inductance of 585 nH at 1MHz. And to estimate the applicability of the thin film inductors fabricated in this research to DC-DC converters. the test board of DC-DC converters was made. It was a boost type and input voltage of 2.7 to 5 volts. output voltage of 5 volts, and the switching frequency was 1.6 MHz. When the thin film inductor was adopted, the converter was operated normally. and the maximum efficiency was 49 % at the load of 50.5 Ω and the output power was 0.51 W. This result was not satisfactory for practical usage at present, but the switching FET devices for higher frequency use be developed in the near future, and then more higher frequency switching DC-DC converter will adopt these inductors.

NTC 서미스터용 스페넬 페라이트의 특성

오영우,허정섭,김현식,이승관 한국전기전자재료학회 1998 전기전자재료학회논문지 Vol.11 No.7

$Mn{1-X}Fe{2+X}O_4, Mg_{1-X}Fe_{2+X}O_4$ (x=0.0, 0.025, 0.1, 0.2) for negative temperature coefficient (NTC) thermistor was prepared by calcination at $800^{\circ}C$ and sintering at form 1100 to $1250^{\circ}C$ with $50^{\circ}C$ intervals. The best linear property was obtained in the Mn-based sample sintered at $1200^{\circ}C$ with x=0.0 composition. Temperature coefficient of resistance, $\alpha$, was $-5.6%/^{\circ}C$ in the Mn-based sample, $-5.2%/^{\circ}C$ in the MM-based sample, and $-1.6%/^{\circ}C$ in the Mg-based sample. thermistor parameter, B, was in the range of 2665~7780 K. The results show the possibility that Mn-Ni-Co based thermistor could be substituted by the composition used in this study.

Blocking filter용 자심 재료의 전자기 특성 및 신호 감쇄율

오영우,이해연,김현식 한국전기전자재료학회 2003 전기전자재료학회논문지 Vol.16 No.6

The electromagnetic properties and thermal behavior of Mn-Zn ferrite cores for the blocking filter of Power Line Communication(PLC) application were investigated as a function of additives. The highest density and permeability were 4.98 g/$\textrm{cm}^2$ and 8,221, respectively and were obtained to the specimen with composition of MnO 24 mol%, ZnO 25 mol% and Fe$_2$O$_3$ mol%, added MoO$_3$ of 400 ppm, SiO$_2$ of 100 ppm, and CaO of 200 ppm. The uniform grains were organized, and the microstructures were densified due to reduction of pores in the specimen. The permeability was increased up to 13,904 as the temperature of specimen increased to 110$^{\circ}C$. However, it was decreased precipitously under 100 over 110$^{\circ}C$. The exothermic behavior was observed in the frequency range from 1 kHz to 1 MHz, and the maximum temperature of specimen was 102$^{\circ}C$ at 1 MHz. In the consequence, the Mn-Zn ferrite core developed in this research will maintain the stable electromagnetic properties since the temperature of ferrite core rose to 93$^{\circ}C$ in the range of 100 kHz to 450 kHz bandwidth qualified for PLC. The blocking filters were designed for single phase and three phases using the in-line and non-contact core. The best attenuation ratios of -46.46 dB and -73.9 dB were measured in the range of 100 kHz to 450 kHz bandwidth, respectively.