Amorphous metallic powders prepared by chemical reduction of metal ions with potassium borohydride in aqueous solution

Abstract

Amorphous metal-metalloid powders have been prepared by chemical reduction of Fez+, Co2+, and Ni2+ 
\nions with potassium borohydride in aqueous solution. The chemical composition of the samples, TM-B-0, 
\nvaries with the metal and with the preparation steps. The as-prepared Co-B-0 and Ni-B-0 samples are 
\ndefinitely amorphous, while the FeB-O sample mainly consists of bcc a-Fe. Crystallization of the samples 
\nthrough thermal treatment has been investigated by X-ray diffraction. The Co-B-O sample evolves toward 
\nfcc metallic cobalt accompanied first by metastable o-Co3B and, at high temperature, by t-Co,B. The Ni-B-O 
\nsample gives rise to fcc metallic Ni and o-Ni3B, which decomposes at higher temperatures. Iron borides 
\nare not detected in the thermal treatment of the Fe-B-0 sample. No evidence of metal oxides is present 
\nin all the samples, thus suggesting the prevalent bonding of oxygen to boron.