Study of preparation conditions of NiO-MgO systems to control the morphology and particle size of the NiO phase

Several NiO-MgO samples were prepared from nickel nitrate hexahydrate and d ifferent sources of magnesia by using a NiO/MgO weight ratio of 1:1 and 4:1 and two different preparative paths. All the samples were structurally cha racterized using BET, XRD, SEM and TPR techniques. The results showed that the sequence of decomposition of the Ni(NO3)(2) 6H(2)O-MgO systems is simil ar to the sequence reported for the nickel nitrate hexahydrate without magn esia. XRD identified complete solid solutions for all the NiO-MgO systems p repared. Their BET areas were similar but their different morphologies and particle sizes mainly depended on the preparative path. Independently of th e magnesia used, the NiO-MgO systems prepared by controlled decomposition o f the nickel nitrate hexahydrate until Ni-3(NO3)(2)(OH)(4) was formed and w hich were subsequently calcined to form NiO (path B) led to very homogeneou s particles of sizes around 100 nm. Path B also gave the highest degrees of NiO reduction. (C) 2000 Elsevier Science B.V. All rights reserved.