SYNTHESIS OF COPPER(II)-CONTAINING NICKEL(II) HYDROXIDE PARTICLES AS PRECURSORS OF COPPER(II)-SUBSTITUTED NICKEL(II) OXIDES

Copper(II)-containing nickel(II) hydroxide particles, i.e., alpha-Ni1- xCux(OH)(2) (0 < X less than or equal to 0.4), have been prepared by a ging 0.5 mol dm(-3) urea, Ni(NO3)(2), and Cu(NO3)(2) solutions at 363 K. After 3 h, coprecipitation is almost complete. The formed solids, c haracterized by powder X-ray diffraction, scanning electron microscopy , energy dispersion X-ray spectroscopy, and Fourier transform infrared spectroscopy, preserve the typical characteristics of alpha-Ni(OH)(2) . Still, their chemical composition, i.e., the copper-to-nickel ratio, is nearly that of the initial solutions. The analysis of the processe s that take place during the formation of alpha-Ni1-xCux(OH)(2) indica tes that, although Cu(II) and Ni(II) precipitation are separate events , the simultaneity of am-Cu(OH)(2) (amorphous copper(II) hydroxide) re dissolution and cr-Ni(OH)a growth provides the appropriate conditions for the intercalation of aqueous Cu(II) species within the interlayer space of the growing alpha-Ni(OH)(2) particles. Upon mild thermal trea tment, i.e., T greater than or equal to 523 K, alpha-Ni1-xCux(OH)(2) p owders are readily converted in Ni1-xCuxO (bunsenite), provided x less than or equal to 0.33; when x is larger than 0.33, the thermodynamica lly expected segregation of tenorite is realized. The ease of Ni1-xCux O (bunsenite) formation is rationalized in terms of the topotatic rela tionship between the layered structure of the precursors and the rock salt structure of the mixed oxide.