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변태봉,이재영,김대영,손진군,권순주,Byeon, T.B.,Lee, J.Y.,Kim, D.Y.,Shon, J.G.,Kwon, S.J. 한국세라믹학회 1991 한국세라믹학회지 Vol.28 No.2
$\gamma$-FeOOH suitable for magnetic recording media was synthesized using waste acid which is the by-product of the iron works factory. Effects of concentration of the acid and alkali and reaction temperature on the particle properties of $\gamma$-FeOOH and magnetic properties of $\gamma$-$Fe_2O_3$ were studied. $\gamma$-FeOOH single phase was formed below 1M of acid concentration with 1M of alkali concentration and at 0.4M of acid concentration with 4M of alkali concentration. While the width of acicular particle was increased, the length of acicular particle was decreased with diluting acid concentration. The magnetic properties of the $\gamma$-$Fe_2O_3$ improved with increasing acid concentration. $\gamma$-FeOOH single phase was formed in the temperature range of 30 to $80^{\circ}C$. The length of the particle was decreased with increasing temperature. $\gamma$-Fe2O3 produced from dehydration of $\gamma$-FeOOH showed bad magnetic properties due to the presence of many pores in the particle. But with successive reduction and oxidation of $\gamma$-$Fe_2O_3$ produced from dehydration of $\gamma$-FeOOH, $\gamma$-$Fe_2O_3$ showed good magnetic properties.
코발트 훼라이트 에피탁시얼 산화철의 생성과 자기특성(Ⅰ)
변태봉(T. B. Byeon),김대영(D. Y. Kim),이재영(J. Y. Lee),손진군(J. G. Shon) 한국자기학회 1992 韓國磁氣學會誌 Vol.2 No.1
To improve the coercivity of γ-Fe₂O₃ particles. We have made cobalt ferrite epitaxial γ-Fe₂O₃ particles by crystallizing cobalt ferrite on the surface of γ-Fe₂O₃ particles. The coercivity of Co_xFe_(3-x)O₄ which is conform to coating layer showed the most superior characteristic when the value of x was 1. On the formation of cobalt epitaxial γ-Fe₂O₃ particles, controlling reaction atmosphere as oxidation atmosphere after non-oxidation atmosphere was the optimum condition to prepare cobalt epitaxial γ-Fe₂O₃ particles with superior magnetic properties. Epitaxial growth of cobalt ferrite on the surface of γ-Fe₂O₃ particles was accomplished at 90℃ for 30 minutes.
제이철염 용액으로부터 α - Fe2O3 의 직접 합성 ( α - Fe2O3 입자 생성에 미치는 반응 온도와 구연산의 영향 )
변태봉 ( T . B . Byeon ) 대한금속재료학회 ( 구 대한금속학회 ) 1996 대한금속·재료학회지 Vol.34 No.8
We have synthesized α-Fe2O3 particles directly from ferric salt solution by hydrothermal reaction. The effect of citric acid concentration and hydrothermal reaction temperature on the formation of α-Fe2O3 particles, formation process of α-Fe2O3 particles were investigated. Also, we proposed a formation model of needle-like α-Fe2O3 particles in this reaction system. The length and aspect ratio of α-Fe2O3, particles were decreased gradually with increasing of citric acid concentration. The crystallization of needle-like α-Fe2O3 particles was inhibited beyond citric acid concentration of 1.5 × 10(-4) mol. We can synthesized α-Fe2O3 particles with the most superior acicularity at 140℃. Aspect ratio of α-Fe2O3 particles was decreased with increasing reaction temperature. α-Fe2O3 particles formed above 220℃ exhibited sphere-like particles. The crystallization to α-Fe2O3 particles from ferric salt was accomplished at 140℃ in 10 minutes. Citric acid was adsorbed with the form of citrate anion(R-COO(-)) on the ferric hydroxide and exerted important role on the formation to the needle-like α-Fe2O3, particles in this reaction system.
비정질 수산화제이철로 부터 자기 기록 매체용 전구체인 헤마타이트 입자의 제조
변태봉(Tae-Bong Byeon),손진군(Jin-Gun Sohn),김태옥(Tae-Ok Kim) 한국자기학회 1996 韓國磁氣學會誌 Vol.6 No.4
Needle-like α-Fe₂O₃ particles as precursor for magnetic recording media were prepared directly from amorphous ferric hydroxide in the aqueous solution by hydrothermal reaction.<br/> Ellipsoidal or rectangular α-Fe₂O₃ particles were formed in the range of pH 10.75~11.75. The length and acicularity of α-Fe₂O₃ particles were decreased gradually with increasing of citric acid concentration. The formation of needle-like α-Fe₂O₃ particles was inhibited above citric acid concentration of 1.5×10-⁴㏖. We can synthesize α-Fe₂O₃ particles with the most superior acicularity at 140 ℃ and can not expect a good needle-like particles above 220 ℃.
변태봉,김태욱,Byeon, Tae-Bong,Kim, Tae-Uk 한국재료학회 1997 한국재료학회지 Vol.7 No.5
졸-겔 dip coating법에 의해 제조한 바륨페라이트 박막의 미세구조와 결정학적인 구조 특성에 관해 조사하였다. 기판에 형성된 바륨페라이트 입자는 침상 형태의 입자들로 구성되어 있었으며, C축은 장축 방향이었고, 막 두께가 증가함에 따라 침상형 입자들은 기판에 평행하게 배향하는 경향을 나타내었다. 박막은 바륨페라이트층, Ba, Fe, SiO$_{2}$로 구성되어 있는 중간층, 그리고 기판층인 SiO$_{2}$층으로 구성되어 있었으며, 중간층과 SiO$_{2}$층간의 계면은 Ba 와 SiO$_{2}$간의 화합물로 구성되어 있었다. 침상 형태의 입자는 95$0^{\circ}C$에서 3시간 열처리하므로써 완전히 소실하였고, 130$0^{\circ}C$에서 3시간 열처리하므로써 c면이 기판에 평행하게 위치하는 완전한 육각판상 형태의 입자로 변화되었다.
결정 성장 조절제를 이용한 침상형 $\alpha$산화철의 제조
변태봉,손진근,Byeon, Tae-Bong,Son, Jin-Geun 한국재료학회 1996 한국재료학회지 Vol.6 No.8
결정 성장 조절체를 이용하여 수용액 중에서 직접 $\alpha$산화철을 제조하였으며, 염기도에 따른 생성물의 입자 특성과 반응기구, $\alpha$산화철의 생성 과정과 침상형 입자의 생성 반응 기구를 고찰하였다. pH 9.0이하에서는 hexagonalgudxo, pH 10.75-11.75범위에서는 ellipsoidal 또는 rectangular 형태의 $\alpha$-${Fe}_{2}{O}_{3}$입자로 각각 생성되었으며, pH12.50이상에서는 acicular 형태의 $\alpha$-FeOOH입자가 생성되었다. pH 10.75-11.75범위에서 제조된 생성물의 염기도는 결정 성장 조절제의 해리에 의해 생성된 수산기 이온(OH-) 때문에 반응물의 염기도에 대비해 약간 증가하는 현상을 나타내었다. 결정 성장 조절제로 사용한 구연상은 제이철 수산화물에 구연산 음이온(R-COO-) 형태로 흡착되어 생성물인 $\alpha$산화철의 입자 형태를 침상 형태로 유도하였다. Iron oxide (hematite, $\alpha$-${Fe}_{2}{O}_{3}$) particles were prepared directly from aqueous solution using a crystal growth controller. Paticles properties and reaction mechanisum of products as a function of basicity, formation process and mechanism of needle-lkie hematite were investigated. hexagonal hermatite particles were formed in teh range below pH 9.0, ellipsoidal or rectangular hematite particles in the range of pH 10.75-11.75 respectively. In the range above pH 12.50, acicular $\alpha$-FeOOH was formed. Basicity of product solution produced in the range of pH 10.7511.75 was increased slightly as compared with basicity of reastants due to hydroxly ion(OH-) formed by dissociation crystal growth controller. Citric acid which is acted as a crystal growth controller was adsorbed in the form of itrate anion(R-COO-) on the ferric hydroxide and exerted important role on the formation to the needle-like $\alpha$-${Fe}_{2}{O}_{3}$ particles in this reaction system.
이재영(J. Y. Lee),변태봉(T. B. Byeon),김대영(D. Y. Kim),이현(H. Lee),한기현(K. H. Han),손진군(J. G. Sohn) 한국자기학회 1993 韓國磁氣學會誌 Vol.3 No.2
This paper presents a study on the effects of silica coating in the production of γ-Fe₂O₃ powders suitable for magnetic recording media. Emphasis has been put on investigating the relationship between the powder characteristics and the effects of silica coating in the heat-treatment stage of γ-Fe₂O₃ production. After we prepared non-coated γ-Fe₂O₃ and silica coated γ-Fe₂O₃ with coating water glass on the surface of goethite and heattreatment process, we compared and investigated powder characteristics. As silica coated layer played a role of preventing the powders from overreduction to metal iron and rapid oxidation, silica coated γ-Fe₂O₃ showed superior magnetization value due to inhibiting the adulteration of α-Fe₂O₃ into the final product. When silica coated layer acted as a sintering restrainer, silica coated γ-Fe₂O₃ showed high coercivity and specific surface area due to good acicularity.