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초임계수 결정화법에서 반응온도 및 압력이 바륨페라이트 제조 특성에 미치는 영향
Influence of Reaction Temperature and Pressure in the Barium Ferrite Synthesis by Supercritical Water Crystallization
한국에너지기술연구원 에너지환경연구부, 대전 305-600 1인하대학교 화학공학과, 인천 402-751
Korea Institute of Energy Research, Daejeon 305-600, Korea 1Department of Chemical Engineering, Inha University, Incheon 402-751, Korea
sdopark@kier.re.kr
HWAHAK KONGHAK, August 2001, 39(4), 417-423(7), NONE
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Abstract
바륨헥사페라이트 분말은 Ba(NO3)2, Fe(NO3)3·9H2O 및 KOH 혼합수용액을 열수처리에 의한 가수분해와 탈수과정을 통한 초임계수 결정화법에 의해 제조되었다. 회분식 실험의 경우, 반응온도와 압력이 증가함에 따라 생성된 바륨헥사페라이트 입자의 결정화도는 향상됨을 알 수 있었으며, 또한 입자의 크기는 증가하고 있는 것으로 나타났다. 그러나 초임계수 결정화법에 의한 연속식 합성공정의 경우, 반응온도가 증가함에 따라 입자의 크기가 감소한 반면, 압력이 증가함에 따라서는 거의 입자의 크기 변화가 없었다. 따라서, 연속식 합성공정에서는 반응온도가 반응압력에 비해 입자의 크기를 제어하는 지배 변수임을 확인하였다. 특히, 전체 계의 압력을 40 MPa, 혼합점(MP2)의 온도를 200 ℃, 반응관내의 온도는 400 ℃, 체류시간을 100초로 하였을 때 생성된 입자의 형태는 육각판상의 단일상이 확인되었으며, 입자크기는 0.1-0.2 μm로 비교적 균일한 입자 분포를 나타내었다.
BaO·6Fe2O3 was produced by hydrothermal treatment of barium nitrite, ferric nitrite and potassium hydroxide under supercritical water conditions. The crystallinity and size of the barium hexaferrite particles were enhanced by increasing the reaction temperature and pressure in the batch system. In the continuous synthesis process, the particle size was decreased by increasing the reaction temperature but was not changed when the reaction pressure was increased. The reaction tempera-ture is a major operational variable for the control of particle size in this rocess. In particular, 0.1-0.2 mm fine particles were synthesized at a pressure of 40 MPa, mixing point(MP2) temperature of 200 ℃, tubular reactor temperature of 400 ℃ and residence time of 100 sec. The particle size distribution was very narrow.
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