Hydrothermal preparation of nickel hydroxide coated iron oxide particles

A novel hydrothermal coating process has been developed to deposit nickel compound over octahedral α-Fe 2 O 3 particles of narrow size distribution (0.2–0.3 μm) by treating aqueous dispersions of the preformed cores at elevated temperatures in Ni(NO 3 ) 2 /CH 3 COONa solutions. A study of the process parameters on the characteristics of the so prepared particles indicated that deposits containing 48.5–51.4 wt.% of nickel could be obtained at temperatures 140–200 °C and reactant concentrations (Ni(NO 3 ) 2 and CH 3 COONa) of 0.1–0.6 mol/l, yielding coatings composed of amorphous Ni(OH) 2 ·H 2 O. The nickel hydroxide films may be formed via the hydrolysis of CH 3 COO − ions followed with the further interaction of OH − and Ni 2+ ions.