Influence of the preparation method on the morphology of templated NiCo <inf>2</inf> O <inf>4</inf> spinel

The synthesis of NiCo 2 O 4 spinel by several nanocasting strategies (i.e., multi-step nanocasting, one-step nanocasting and soft-templating), in which nickel and cobalt nitrates are used as precursors and Pluronic P123 as surfactant, is explored. First, in the multi-step nanocasting, the effect of the impregnation method (evaporation, solid-liquid and two-solvent) of the SBA-15 silica template on the morphology of NiCo 2 O 4 replica is investigated. The evaporation method seems to be the best choice to obtain mesoporous NiCo 2 O 4 powder which, after calcination at 375 °C and subsequent template removal, displays the highest surface area (93.1 m 2 /g). We have also checked the feasibility of the one-step nanoscating approach for the synthesis of ordered NiCo 2 O 4 arrays, though this methodology entails severe difficulties, mainly related to the different decomposition temperature of the nitrate precursors and the P123 surfactant. Finally, randomly oriented, aggregated NiCo 2 O 4 nanoparticles are obtained by means of P123 surfactant-assisted soft-templating approach. © Springer Science+Business Media B.V. 2011.