Amorphous metal-metalloid powders have been prepared by chemical reduction of Fez+, Co2+, and Ni2+ ions with potassium borohydride in aqueous solution. The chemical composition of the samples, TM-B-0, varies with the metal and with the preparation steps. The as-prepared Co-B-0 and Ni-B-0 samples are definitely amorphous, while the FeB-O sample mainly consists of bcc a-Fe. Crystallization of the samples through thermal treatment has been investigated by X-ray diffraction. The Co-B-O sample evolves toward fcc metallic cobalt accompanied first by metastable o-Co3B and, at high temperature, by t-Co,B. The Ni-B-O sample gives rise to fcc metallic Ni and o-Ni3B, which decomposes at higher temperatures. Iron borides are not detected in the thermal treatment of the Fe-B-0 sample. No evidence of metal oxides is present in all the samples, thus suggesting the prevalent bonding of oxygen to boron.
Amorphous Metallic Powder Prepared by Chemical Reduction of Metal Ions with Potassium Borohydride in Aqueous Solution
CORRIAS, ANNA;ENNAS, GUIDO;
1990-01-01
Abstract
Amorphous metal-metalloid powders have been prepared by chemical reduction of Fez+, Co2+, and Ni2+ ions with potassium borohydride in aqueous solution. The chemical composition of the samples, TM-B-0, varies with the metal and with the preparation steps. The as-prepared Co-B-0 and Ni-B-0 samples are definitely amorphous, while the FeB-O sample mainly consists of bcc a-Fe. Crystallization of the samples through thermal treatment has been investigated by X-ray diffraction. The Co-B-O sample evolves toward fcc metallic cobalt accompanied first by metastable o-Co3B and, at high temperature, by t-Co,B. The Ni-B-O sample gives rise to fcc metallic Ni and o-Ni3B, which decomposes at higher temperatures. Iron borides are not detected in the thermal treatment of the Fe-B-0 sample. No evidence of metal oxides is present in all the samples, thus suggesting the prevalent bonding of oxygen to boron.
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