Characterization of powders obtained by comminution of Fe₄₀Ni₄₀B₂₀ amorphous ribbons

Abstract

A possible attractive use of amorphous alloys is as catalytically active materials. The aim of the present work is to find a treatment leading to an increase in the surface areas of the ribbon by direct comminution of the glassy alloys, meanwhile maintaining the amorphous state. Amorphous Fe₄₀Ni₄₀B₂₀ ribbons produced by a planar-flow casting technique were comminuted in a high-energy ball mill for 20 and 40min. To evaluate the influence of treatment temperature, the comminution of a part of the samples was performed after a cooling pre-treatment of the mill by liquid nitrogen. Furthermore, a batch of samples was cathodically charged by hydrogen, to test the effect of the resulting embrittlement. X-ray analysis and differential scanning calorimetry were employed to evaluate the extent of crystallization of the comminuted ribbons.

The results show a noticeable influence of hydrogen embrittlement on particle size. Comminution of hydrogen-embrittled ribbons for the same time as the as-quenched ribbons increases to a great extent the fraction of particles of smaller size. The cooling pre-treatment with liquid nitrogen contributes to the maintenance of a higher degree of amorphicity.