氢还原制备树枝状Fe_3O_4和α-Fe及其静磁性能研究

Hydrogen Reducing Synthesis and Magnetic Properties of Dendritic Fe_3O_4 and α-Fe

以树枝状α-Fe2O3为前驱物,通过氢还原制备得到Fe3O4和α-Fe树枝状结构,系统研究热处理还原条件对产物形貌和成分的影响。结果表明:随着还原温度和还原时间的增加,树枝状α-Fe2O3前驱物逐渐被还原为α-Fe,还原产物的树枝状形貌保持程度依次降低。还原是一个缓慢且分级进行的过程,因此通过控制还原反应的温度和时间,可以得到形貌良好的树枝状Fe3O4和α-Fe。而当还原温度和时间增加时,产物会发生晶粒生长以及重结晶过程,从而导致树枝状形貌被破坏程度逐渐增加,精细结构逐渐消失。对其进行静磁性能表征发现:由于具有大的形貌各向异性,Fe3O4和α-Fe树枝状结构在室温下具有大的矫顽力和剩余磁化强度。

The dendritic Fe304 and α-Fe were synthesized by a high temperature hydrogen reduction, using the dendritic α-Fe as starting materials. The influences of reduction conditions on the final products were studied systematically. It was found that the dendritic α-Fe2O3 was reduced to dendritic Fe3O4 and α-Fe gradually, and the dendritic morphology of the finally obtained products was destroyed gradually. Because the reduction was a slow and multi-step process, the Fe304 and ct- Fe which maintained the dendritic morphologies could be obtained through controlling the reduction temperature and time. However, when the reduction time prolonged, since there were crystal growth and recrystallization in the reduction process, the fine structure disappeared and the dendritic morphology was damaged gradually. Because of the large effective anisotropy constant derived from the peculiar morphology the dendritic structure, the as-obtained dendritic Fe304 and α-Fe exhibited enhanced coercivity and remanent magnetizations at room temperature.