Production Conditions of Acicular Magnetic Metal Nanoparticles for Magnetic Recording
Production Conditions of Acicular Magnetic Metal Nanoparticles for Magnetic Recording
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磁记录用针状磁性金属纳米粒子的制备条件
DOI：
10.2320/matertrans.46.1368
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发表时间：
2005
影响因子：
1.2
通讯作者：
T. Yamamura
中科院分区：
文献类型：
--
作者：
K. Iwasaki;Takuya Itoh;T. Yamamura
研究了针状α-Fe 2 O3颗粒的氢还原条件和通过氢还原和低氧缓慢氧化工艺得到的金属纳米颗粒的表面钝化条件，以确定用于磁记录的针状磁性金属纳米颗粒的最佳制备条件。用表面处理过的针状α-FeOOH纳米粒子（含12.6at%Co-9.4at%Si-7.0at%Al），在α-FeOOH粒子加热脱水温度为823 K，流量为5 × 10 - 6 m3（STP）·s - 1，还原气体组成为50mol%H2 - 50mol%Ar，和823 Kin还原温度。所得到的还原金属颗粒由单晶或多晶组成。颗粒内部是还原的致密金属相，其中既没有缺陷也没有孔隙的晶体生长充分进行。金属颗粒的表面氧化层是由缓慢氧化形成的，结果是尖晶石结构的Fe 3 O 4。金属芯完全被表面氧化物层覆盖，并且观察到氧化物层内部没有缺陷、孔等的致密晶体充分生长。据推测，具有更高耐腐蚀性的钝化层可以用更厚的表面氧化物层获得，因为金属纳米颗粒表面上的氧化物层随着缓慢氧化的温度升高而变得更厚。在338 K的氧化温度条件下，可以制备出具有优异耐蚀性能的针状磁性金属纳米颗粒。流量为5 × 10 - 6 m3（STP）·s - 1，氧化气体组成为0.5mol%O2 - 99.5mol%N2。
Hydrogen reduction conditions of α-Fe 2 O 3 particles and surface passivation conditions of metal nanoparticles obtained through a hydrogen reduction process of acicular α-Fe 2 O 3 particles and a slow oxidation process in a low oxygen concentration have been studied in order to determine optimum production conditions of acicular magnetic metal nanoparticles utilized for magnetic recording. Acicular magnetic metal nanoparticles were produced by using the surface-treated acicular α-FeOOH nanoparticles containing 12.6 at %Co-9.4 at % Si-7.0 at %Al under the condition of 823 K in temperature of dehydration of α-FeOOH particles by heating, 5 x 10 - 6 m 3 (STP).s - 1 in flow rate, 50 mol%H 2 -50mol%Ar in composition of a reducing gas, and 823 Kin reduction temperature. The resulting reduced metal particles are composed of either a single crystal or polycrystals. The inside of the particles was a reduced dense metal phase in which the crystal growth with neither defect nor pore was sufficiently proceeded. The surface oxide layer of metal particles which is formed by the slow oxidation results in a spinel structure of Fe 3 O 4 . The metallic core was entirely coated by the surface oxide layer, and it was observed that the dense crystal having no defect; pore and so forth inside the oxide layer was sufficiently grown. It is assumed that a passivation layer possessing a higher corrosion-resistant property can be obtained with a thicker surface oxide layer, since the oxide layer on the surface of the metal nanoparticle becomes thicker with higher temperature of slow oxidation. Acicular magnetic metal nanoparticles having the excellent property of corrosion resistance were able to be produced under the condition of 338 K in oxidation temperature. 5 × 10 - 6 m 3 (STP).s - 1 in flow rate and 0.5 mol%O 2 -99.5 mol%N 2 in composition of oxidizing gas.