Reactive deposition of ultrafine cobalt powders - Part I Electrochemical investigation

Abstract

During the reactive deposition of cobalt powders, Co(OH)2 colloidal layers are formed at the electrode surface; the individual cobalt crystals are isolated by the Co(OH)2 colloid around the grain boundaries so that their growth is inhibited and ultrafine cobalt crystal grains are formed, which are loosely attached to the titanium substrate. The existence of Co(OH)2 colloid layer at the electrode surface depresses the hydrogen evolution reaction in the deposition process and accelerates the decrease of the interfacial Co2+ concentration. Therefore, compared to the normal deposition of cobalt powders, it has several unique advantages: (1) ultrafine cobalt powders (0.4-0.6 μm) can be produced; (2) the amount of Co(OH)2 in the powders is decreased; (3) there is a wider range of current density for the formation of cobalt powders. © 1993 Chapman & Hall.