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Microstructure and Magnetic Property of Nanostructured NiZn Ferrite Powder
남중희,Nam, Joong-Hee The Korean Ceramic Society 2002 한국세라믹학회지 Vol.39 No.12
Nanostructured spinel NiZn ferrites were prepared by the sol-gel method from metal nitrate raw materials. Analyses by X-ray diffraction and scanning electron microscopy showed the average particle size of NiZn ferrite was under 50 nm. The single phase of NiZn ferrites was obtained by firing at 250${\circ}C$, resulting in nanoparticles exhibiting normal ferrimagnetic behavior. The nanostructured $Ni_{1-X}Zn_XFe_2O_4$ (x=0.0∼1.0) were found to have the cubic spinel structure of which the lattice constants ${\alpha}_2$ increases linearly from 8.339 to 8.427 ${\AA}$ with increasing Zn content x, following Vegard's law, approximately. The saturation magnetization $M_s$ was 48 emu/g for x=0.4 and decreased to 8.0 emu/g for higher Zn contents suggesting the typical ferrimagnetism in mixed spinel ferrites. Pure NiZn ferrite phase substituted by Cu was observed before using the additive but hematite phase was partially appeared at $Ni_{0.2}Zn_{0.2}Cu_{0.6}Fe_2O_4$. On the other hand, the hematite phase in this NiZn Cu ferrite was disappeared after using the additive of acethyl aceton with small amount. The saturation magnetization Ms of $Ni_{0.2}Zn_{0.8-y}Cu_yFe_2O_4$(y=0.2∼0.6) as measured was about 51 emu/g at 77K and 19 emu/g at room temperature, respectively.
NiCuZn계 페라이트의 조성에 따른 복소투자율 변화 해석
남중희(Joong-Hee Nam),오재희(Jae-Hee Oh) 한국자기학회 1996 韓國磁氣學會誌 Vol.6 No.6
The characteristics of the complex permeability of (Ni_xCu_(0.2)Zn_(0.8-x)O)_(1-w) (Fe₂O₃)_(1+w) with various Ni and Co₃O₄ contents were investigated in this work. It is found that the NiCuZn ferrites with x≥0.6 have a relatively small peak width of the imaginary part of permeability μ″. The resonance frequency is increased as Ni content becomes higher, where the loss is low. The μ″ value decreases with increasing Fe₂O₃ deficiency, but the resonance frequency(fμㆍmax) is only slightly affected by Fe₂O₃ deficiency. In case of Co₃O₄ addition to the NiCuZn ferrites, the fμㆍmax increases since the initial permeability decreases with the amount of Co₃O₄. It is concluded that the Ni content in the NiCuZn ferrite is a dominant factor for the total loss of these spinel ferrites.
자료(資料) : 수입원료견(輸入原料繭)의 견질조사(繭質調査)
남중희 ( Joong Hee Nam ) 한국잠사학회 1983 한국잠사곤충학회지 Vol.25 No.2
최근, 우리나라가 외국산견을 수입하여 기계 검정한 성적을 비교 분석한바 다음과 같은 결과를 얻었다. 1) 원료견의 성상이 고르지 못한데 특히 선제견비율과 건견생사량비율에서 심한 변동을 나타내었다. 2) 상위등급의 원료견을 수입하지 못하고 D, E격의 하위등급견이 수입되었으며 가격이 높은 편이다. 3) 상위격의 원료견을 수입하는 것이 향후 우러나라 견제품의 고급화를 피하리라고 본다. This survey was to realize the foreign cocoon quality and to provide data for suitable reeling conditions. Cocoons were inported from Taiwan (7 packs) and Hongkong (12 packs) in 1983. The practical inspection and classiffication of above cocoon was performed at Provincial Institute of cocoon testing and tested data were collected to evaluate the cocoon quality. The results were as follows. 1. It showed higher variation of the average raw silk yield percentage and cocoon assorting rate than domestic cocoon. 2. In view of the low quality products, cocoon price was expensive and most of packs were evaluated as inferior grade. 3. It was supposed that importing the superior quality cocoon from foreign country may be contributed to manufacturing of silk commodity of higher grade.
근역장 통신용 0-3형 고분자 자성 복합소재의 복소투자율 변화
남중희(Joong-Hee Nam),임충혁(Choong Hyuck Lim),윤지선(Ji Sun Yun),정영훈(Young-Hun Jeong),조정호(Jeong-Ho Cho),백종후(Jong Hoo Paik),김효태(Hyo Tae Kim),김종희(Jong-Hee Kim) 한국자기학회 2012 韓國磁氣學會誌 Vol.22 No.6
Magnetic properties of composite materials consisting of polymer filled with ferromagnetic powders (MnZn ferrite, Fe-Si alloy) were investigated in this study. The volume fraction of magnetic powders as fillers was varied from 70 % to 95 %. This paper presents the fabrication method of polymer magnetic composites in an effort to produce the 0-3 types of MnZn ferrite and FeSi as fillers with a proper complex permeability through the optimization of some experimental parameters. The polymer matrix composites were prepared by mixing the crushed ferrites and flaky FeSi powders homogenously with low-density resins (EPDM, epoxy). The relationships among the manufacturing technology of these materials, their filler volume fraction, as well as their complex permeability were measured and analyzed.
전기방사법에 의한 NiZn 페라이트 나노섬유의 제조 및 특성 연구
주용휘,남중희,조정호,전명표,김병익,고태경,Joo, Yong-Hui,Nam, Joong-Hee,Cho, Jeong-Ho,Chun, Myoung-Pyo,Kim, Byung-Ik,Ko, Tae-Gyung 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.1
Electrospinning process is the useful and unique method to produce nanofibers from metal precursor and polymer solution by controlled viscosity. In this study, the NiZn ferrite nanofibers were prepared by electrospinning with a aqueous metal salts/polymer solution that contained polyvinyl pyrrolidone and Fe (III) chloride, Ni (II) acetate tetrahydrate and zinc acetate dihydrate in N,N-dimethylformamide. The applied electric field and spurting rate for spinning conditions were 10 kV, 2 ml/h, respectively. The obtained fibers were treated at $250^{\circ}C$ for 1 h to remove the polymer. Finally, the NiZn ferrite fibers were calcined at $600^{\circ}C$ for 3 h and annealed at $900{\sim}1200^{\circ}C$ in air. By tuning the viscosity of batch solution before electrospinning, we were able to control the microstructure of NiZn ferrite fiber in the range of $150{\sim}500\;nm$ at 770 cP. The primary particle size in $600^{\circ}C$ calcined ferrite fiber was about 10 nm. The properties of those NiZn ferrite fibers were determined from X-ray diffraction analysis, electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, thermal analysis, and magnetic measurement.
강경민,조정호,남중희,고태경,전명표,Kang, Kyung-Min,Cho, Jeong-Ho,Nam, Joong-Hee,Ko, Tae-Gyung,Chun, Myoung-Pyo 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.7
The most widely used piezoelectric ceramics are lead oxide based ferroelectrics (PZT). However, the toxicity of lead oxide and its high vapor pressure during processing have led to a demand for alternative lead-free piezoelectric materials. We synthesized Lead-free piezoelectric ceramics of $0.96(K_{0.5}Na_{0.5})NbO_3-0.04SrZrO_3+x$ mol% $ZrO_2$ [KNN-SZ+$xZrO_2$; x= 0~0.10] doped with 0.1 wt% $MnO_2$ by a conventional solid state method. We investigated the piezoelectric properties and microstructures of these disk samples sintered in reduced atmosphere in order to evaluate the possibility of the multilayered piezoelectric ceramics having the base metal such as Ni as a internal electrode. All of these KNN-SZ samples sintered in 3%$H_2-97%N_2$ atmosphere at $1,140^{\circ}C$ exhibit pure perovskite structure irrespective of the content of $ZrO_2$. Meanwhile, the sintering denisty and piezoelectric properties such as $K_p$, $Q_m$ and $d_{33}$ of KNN-SZ samples as a function of $ZrO_2$ content show the maxima ($k_p$=28.07%, $Q_m$= 101.34, $d_{33}$= 156 pC/N) at x= 0.04 and it is likely that there is some morphotropic phase boundary(MPB) in this KNN-SZ+$xZrO_2$ composition system. These results indicate that the ceramic composition is a promising candidate material for applications in lead free multilayer piezoelectric ceramics.
Si(100) wafer와 SiO<sub>2</sub>/Si(100) 기판에 동시 스퍼터링법으로 증착된 NiFe 합금 박막의 상변화 및 자기적 특성
강대식,송종한,남중희,조정호,전명표,Kang, Dae-Sik,Song, Jong-Han,Nam, Joong-Hee,Cho, Jeong-Ho,Chun, Myoung-Pyo 한국결정성장학회 2010 한국결정성장학회지 Vol.20 No.5
Si(100) wafer와 $SiO_2$/Si(100) 웨이퍼에 증착된 NiFe 합금 박막의 결정상과 자기적 특성을 비교하고자 동시 스퍼터링법을 이용하여 두 기판 위에 150 nm의 박막을 제조하여 그의 상변화와 자기적 특성을 XRD, FE-SEM, VSM으로 비교하였다. 두 기판 위에 증착된 NiFe 박막은 BCC상으로 증착되었으나 $400^{\circ}C$에서 2시간 열처리를 한 결과 BCC에서 FCC로의 상전이가 일어나는 것을 관찰 할 수 있었으며 Si(100) wafer위에 증착된 박막에서는 $500^{\circ}C$에서 열처리 후에도 BCC와 FCC가 혼재하여 나타나는 것을 알 수 있었다. $450^{\circ}C$에서 열처리 하였을 때 각형비가 가장 높았으며 포화자화는 0.0118 emu로 나타나고 있었다. $500^{\circ}C$ 이상의 온도에서는 상전이로 인해 포화자화가 급격히 감소하는 것을 볼 수 있었다. Ni-Fe alloys have various applications such as thin film inductor, thin film transformer, magnetic head's shield case, etc. Magnetic properties of Ni-Fe thin films depend on the process parameters such as thickness, contents, deposition rate, substrates, etc. In this study, NiFe films with a thickness of about 150nm were deposited on Si(100) wafer and $SiO_2$/Si(100) substrate at room temperature by a DC magnetron co-sputtering using Fe and Ni targets. Their phase formation and magnetic properties as a function of annealing temperature were investigated with XRD, FE-SEM and VSM. The assputtered films have BCC structure. With increasing annealing temperature, NiFe thin film for $SiO_2$/Si(100) substrate transformed completely from BCC to FCC phase above $500^{\circ}C$, but some BCC phase remained above $500^{\circ}C$ on Si(100) wafer. For samples annealed at $450^{\circ}C$, squareness ratio of NiFe thin film shows peak value and its saturation magnetization is around 0.0118 emu, which means that the optimum annealing temperature of NiFe thin film seems to be $450^{\circ}C$. The saturation magnetization of films decreased rapidly above the annealing temperature of $500^{\circ}C$ due to phase transformation from BCC to FCC phase.