• 한국세라믹학회지
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• 제16권2호
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• pp.89-98
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• 1979

In order to prepare ferroxplana ZnY $(Ba_2Zn_2Fe_{12}O_{22})$, which would be useful for GHz-band communication, the optimum coprecipitation condition of 1 $BaCl_{2-1} Zn(NO_3)_2-6FeCl_3$ in $NaOH-Na_2CO_3$ solution was investigated by use of a new apparatus invented in our laboratory. By freeze-drying and calcining the coprecitated hydroxide-carbonate, the very reactive powder was obtained, from which the synthesis process of ZnY and the other related crystals were investigated by means of X-ray diffraction. In results, it was found that the reactive powder containing ZnY as the major component can be prepared by this method, which may be used in manufacturing the various magnetic cores for the microwave communication.

• 한국입자에어로졸학회지
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• 제6권1호
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• pp.21-27
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• 2010

New process consisting of electrospray and epitaxial crystal growth processes was applied to the preparation of c-plane oriented barium ferrite ($BaFe_{12}O_{19}$) thin film for high density magnetic recording media. Sodium citrate aided process was proper to preparation of amorphous $BaFe_{12}O_{19}$ nanoparticles with geometric mean diameter of 3 nm and geometric standard deviation of 1.1. The electrospray was applicable to the prepare of amorphous $BaFe_{12}O_{19}$ thin film on a substrate, and the film thickness could be controlled by adjusting the electrospray deposition time. The c-plane oriented $BaFe_{12}O_{19}$ thin film was successfully prepared by 3 step annealing process of the $BaFe_{12}O_{19}$ amorphous film on a sapphire($Al_2O_3$) substrate; annealing at $350^{\circ}C$ for 30 min, annealing at $500^{\circ}C$ for 30 min, and annealing at $700^{\circ}C$ for 60 min.

• 한국자기학회지
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• 제9권1호
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• pp.35-40
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• 1999

M-type Ba 페리이트를 Ba 대신 Sr으로 치환시킨 페라이트 분말과 Fe대신 Co-Ti으로 치환시킨 육방 페라이트 분말을 각각 citrate sol-gel법과 2 MOE sol-gel법으로 합성하였다. 이들 분말들을 소결 처리 후 수소 분위기 하에서 온도를 변화시키면서 환원처리 하였다. X-선 회절을 이용한 결정구조 해석에서 105$0^{\circ}C$에서 소결 처리된 분말의 경우 단일상의 M-type 육방정 구조로 나타났다. X-선 회절실험 결과 Sr0.5Ba0.5Fe12O19과 다르게, Co-Ti 치환형 페라이트인 Sr0.7Ba0.3Fe10CoTiO19에서는 Co-Ti 치환이 환원과정을 저지시키는 효과가 있는 것으로 나타났다. 육방 페라이트에서 수소환원에 의한 포화자화 Ms값의 증가 원인을 알아보기 위하여 Mossbauer 분광실험을 실시하였다. Mossbauer 실험결과는 대부분의 $\alpha$-Fe가 4fvi자리와 12k자리로부터 발생되는 것으로 나타났으며, 이 $\alpha$-Fe 형성에 의한 Fe3+이온의 결함이 자기 상호작용의 붕괴를 가져와서, 자기이방성의 변화를 초래하고 또한 Ms값의 증가를 가져오는 것으로 추측된다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2010년도 임시총회 및 하계학술연구발표회
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• pp.62-63
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• 2010

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2000년도 춘계연구발표회 논문개요집
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• pp.136-137
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• 2000

• 한국결정성장학회지
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• 제1권1호
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• pp.100-106
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• 1991

pH에 따른 Ba.Fe 수산화물의 용해도를 용해도적(Ksp)을 가지고 계산하여 침전물을 얻었으며 침전물은 $750^{\circ}C$에서 결정화하여 $BaFe_12O_19$ 단일상을 형성한다. 공침물을 각기 다른 Process를 사용하여 filtering과 sintering하였다. 즉 공침전물을 filter cake drying과 일반적인 grinding한 후 pressing하는 방법으로 소결시켰으며 각각 $950^{\circ}C$와 $1,100^{\circ}C$ 2시간 열처리에 의해 이론밀도의 98%에 이르는 치밀한 소결체를 얻을 수 있었다. 또한 freezing process에 서는 colloid상태의 침전물이 수십$\mu\textrm{m}$의 분말을 형성하여 Filtering 효율을 크게 증진시킬 수 있었다.

• 한국세라믹학회지
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• 제34권1호
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• pp.37-44
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• 1997

졸겔법중 딥코팅법을 이용하여 조성비 2Fe/Ba=5.25 졸로부터 바륨페라이트 박막을 제조하였다. 졸의 겔화과정은 4단계로 구분할 수 있으며, 8$0^{\circ}C$에서 90분간 반응시켜 제조한 졸이 코팅용 졸로서 가장 적합한 특성을 나타내었다. 박막층에 형성된 침상 형태의 입자들은 기판에 수평 하게 위치하고 있었으며, 박막 두께가 증가함에 따라 그 경향은 증가하였다. 침상형 입자의 자화용이축 방향은 장축 방향이었다.

• 한국생산제조학회지
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• 제19권4호
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• pp.491-497
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• 2010

The magnetic polishing is the useful method to finish some machinery fabrications by using magnetic power. This method is one of the precision techniques and has an aim for clean technology in the clean pipes. The magnetic abrasive polishing method is not so common in the field of machine that it is not known to widely. There are rarely researcher in this field because of non-effectiveness of magnetic abrasive. This paper deals with mediocritizing magnetic polishing device into regular lathe and this experiment was conducted in order to get the best surface roughness at low cost. This paper contains the result of experiment to acquire the best surface roughness, not using the high-cost polishing material in processing. In this paper, We could have investigated into the changes of the movement of magnetic abrasive grain. In reference to this result, we could have made the experiment which is set under the condition of the magnetic flux density, polishing velocity according to the form of magnetic brush.

• 한국세라믹학회지
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• 제34권10호
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• pp.1045-1052
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• 1997

Barium ferrites (BaFe12O19) were synthesized at the various temperature by the coprecipitation-oxidation method. X-ray diffraction Rietveld analysis for barium ferrites were performed, their microstructures were observed and their magnetic properties were measured, in order to analyze the crystal structures and determine the optimal temperature of heat-treatment. The barium ferrite, its average particle size 80 nm, was formed at 600℃ through the hematite (α-Fe2O3), but the site occupations of the Fe's in tetrahedral and bipyramidal sites and of the Ba relatively low. Increasing the heating temperature, these occupations and the magnetization increased, and the crystal c-axis decreased. These changes were very small at the heat treatment of above 800℃, but the particles were rapidly grown. It is suggested that the optimal temperature of heat-treatment is 800℃, at which temperature crystal structure is relatively stable and the particles hardly ever grow.

• Journal of Magnetics
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• 제4권2호
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• pp.65-68
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• 1999

The M-type barium ferrite ($BaFe_{12}O_{19}$) is well known magnetic material to be used as a permanent magnet due to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ sublattices reduces the uniaxial anisotropy and those compounds open a new application field of noise suppressor at high frequencies. In this study, the magnetic and microwave absorbing properties are investigated in Ti-and Co-substituted barium ferrites ($BaFe_{12-2X} Ti_XCo_XO_{19}$). The saturated magnetization decreases linearly with the substitution of Ti and Co. The rapid drop in coercive force is observed with Ti and Co substitution upto x=1.2. The magnetic permeability spectrum shows the natural magnetic resonance in the specimens with small coercive force and large attenuation of microwave is predicted in those specimens at high frequencies (above 4 GHz).