Formation of Ultra-fine Amorphous Powders in (Fe, Co, Ni)-B Systems by Chemical Reduction Method and Their Thermal and Magnetic Properties

概要

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Amorphous ultra-fine powders in (Fe, Co or Ni)-B, Fe-Co-B, Fe-Ni-B and Co-Ni-B systems were produced by reduction of metal ions in an aqueous solution by use of KBH_4. The powders have a spherical shape with diameters ranging from 5 to 20 nm. The boron concentration is in the range of 28 to 37 at% and the composition of metal elements can be controlled by changing the concentration of metal ions. Crystallization temperatures (T_x) and heats of crystallization for the (Fe-Ni)_<72>B_<28> powders agree with those obtained for the amorphous alloys of the same composition produced by melt spinning. Furthermore, the compositional dependences of T_x, coercivity and magnetization are very similar to those obtained in the chemically synthesized (Fe-Co)_<63>B_<37>, (Fe-Ni)_<72>B_<28> and (Co-Ni)_<67>B_<33> amorphous powders and melt-spun (Fe-Co)_<78>Si_8B_<14>, (Fe-Ni)_<78>Si_8B_<14> and (Co-Ni)_<78>-Si_8B_<14> amorphous ribbons. It is concluded that there is no significant difference in the amorphous structure obtained in the chemically synthesized powders and the melt-spun ribbons, in spite of an essential difference in the formation mechanism of these amorphous alloys.
東北大学の論文
1989-03-20