Nanocrystalline NiO and NiO-Ni(OH)2 composite powders prepared by thermal and mechanical dehydroxylation of nickel hydroxide

摘要

Nanocrystalline NiO and nanocompositeNiO-Ni(OH)2, in the form of ultrafine powders, wereprepared from Ni(OH)2 by thermal and mechanicaldehydroxylation respectively. The powders werecharacterized by X-ray diffraction, differentialscanning calorimetry, secondary electron imaging andtransmission electron microscopy. An orientationrelationship was observed such that the (0001) planesin the original hexagonal hydroxide structure wereparallel to (111) planed in the cubic NiO followingthermal dehydroxylation. It is proposed that thecrystallographic transformation required for thedehydroxylation process involves the glide of Shockleypartial dislocations. It is further suggested that theeffect of mechanical grinding is to cause extensivefaulting through the glide of Shockley partialdislocations. Which lowers the activation energy fordehydroxylation so that the process proceeds at ambient temperature..