A STUDY OF FE-NI-B ULTRAFINE ALLOY PARTICLES PRODUCED BY REDUCTION WITH BOROHYDRIDE

Fe-B, Fe-Ni-B, and Ni-B ultrafine alloy particles have been prepared by reduction of metal ions in aqueous solution with borohydride. It is shown that iron and nickel contents in the particles can be easily varied by changing the Ni/(Ni + Fe) ratio in the aqueous solution; however, the boron content is constant when the concentration of the borohydride is kept constant. Several experimental results show that the alloy particles are amorphous. The scanning electron microscopic image indicates that the surface morphology of Fe35Ni15B26 alloy particles looks like cotton clusters. From the high-resolution image, the average size of the high-resolution image, the average size of the particles was determined to be about 30 +/- 5 nm and the fine structure of the particles indicates that there is an obvious boundary between the outer shell with a thickness of about 5 nm and the inner core with a diameter of about 20 nm. The particles are partially crystallized on the outer shell while the inner core is almost completely amorphous.