Sintering of High‐Purity Nickel Oxide, II

Abstract

The effects of particle size, compacting pressure, additives, and mode of preparation on the sintering of nickel oxide are presented. A low calcining temperature results in a high bulk density of a sintered compact. No appreciable change in the rate of sintering is found above 1000 kg. per sq. cm., whereas the unheated density increases with increasing pressures. Additions of CaO promote sintering, additions of Na 2 O, Fe 2 O 3 , and Al 2 O 3 retard sintering, and CeO 2 and Ag 2 O have no effect; B 2 O 3 accelerates grain growth but retards densification. Nickel oxide from oxalate has a small rate of sintering as compared with nickel oxides from hydroxide, nitrate, and carbonate. The effects of the mode of preparation of nickel oxide are discussed in view of the activation energy of electronic conductivity and particle size.