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RISS 인기검색어
- 검색키워드
- 저자 : 김혁돈 (검색결과 2 건)
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화학기상응축법으로 제조된 Fe계 나노 분말의 특성분석 연구
In this study, Fe-base nanopowders were prepared and characteristics were investigated using chemical vapor condensatio. The analysis results of XRD and TMA of Fe-N nanopowder manufactured at 500 ℃ in atmospheric pressure or at 850 ℃ in vacuum conditions were Fe_(3)N (ε-type) phase and synthesized powders below 700 ℃ vacuum conditions existed as most of α-Fe phas. Regardless of its phase, Fe-N nanoparticles formed in atmospheric pressure were finer than those formed in vacuumed conditions. But in the same pressure condition, the particle size also increased with increase of reaction temperature in vacuum condition(0.01torr). It has been found that Fe_(3)N nanoparticles take long chain form connected to each other, which are generally spherical particles of nanometer-sized for minimum of electromagnetic energy. Also it was found that synthesized Fe_(3)N powders in 500 ℃ atmospheric pressure were coarser than particles formed in 850 ℃ vacuum conditions. The average particle size should be about 40 nm. Fe-C nanopowder manufactured by CVC method is unlike Fe-N. Fe-C synthesized vacuum condition clearly showed increased size with increase of reaction temperature and spherical particles existed rather in cluster form than in chain form. As a result of magnetic properties, the magnetic saturation grew to 150 emu/g from 100 emu/g as reaction temperature was increased. The magnetic hysteresis loop showed that of a typically α-Fe nanopowder. In a vacuum environment, the reaction time of Fe atom and C atom is so short that synthesis of Fe-C compound is not easy, even in high temperature. By increasing the reaction time from few millisecond to few seconds to attempt synthesis in atmospheric pressure, Fe-C nanopowder was successfully obtained, which is existing as main phase. The shapes of Fe-C nanopowders manufactured in atmospheric pressure are spherical particles, just as Fe-N. The particle sizes clearly increased as synthesis temperature increased. Therefore the average particle sizes of synthesized particles in 650 ℃ is 30 nm, while that of synthesized particles in 800 ℃ is 50 nm. FePt nanopowders were manufactured by CVC method. It is possible to make FePt nanopowder of L10 phase without heat treatment. When the mixing ratio of Fe and Pt is 2.5 : 1, FePt nanopowder of 50 : 50 is produced. It has been found that spherical FePt nanopowder on the average less than 5nm in 900 ℃ were obtained and average size of FePt powder also increased by increasing the temperature from 800 to 1000 ℃. The FePt nanopowder obtained with the ratio of 50 to 50 at 900 ℃ were treated by heating for 30 minutes from 300 to 700 ℃ in a hydrogen atmosphere, and FePt powder of L10 shape was fond at 600 oC and have changed to FePt of A1 shape at 700 ℃. FePt powder by heat treatment at 500 ℃ showed the highest magnetic properties. Magnetic fluids were prepared using Fe powder, manufactured by CVC method, and investigated the stabilization. Although it lasts as an aqueous fluid for hours, there's no big difference in diffraction peaks of nanopowder and α-Fe nanopowder. This is certifying that oxidation is not processed any more during which α-Fe particles in magnetic fluid covered well with fatty acid of surfactant, and it was found that enhanced magnetic fluid could be produced using Fe-base nanopowder by CVC method. The magnetic fluid showed good dispersibility with increasing pH. When pH is 11, it showed the optimum dispersibility over 80 %. In addition, when pH is over 12, condensation of nanoparticle occurred.
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