Porous structure of NiO‐based xerogels

NiO‐based xerogels were prepared by sol‐gel processing starting from the NiCl 2 ‐BuOH‐H 2 O system. Structural features associated to the porosity of xerogels were studied by small‐angle X‐ray scattering. Xerogels heat‐treated at low temperatures (423 and 573 K) are composed of hydrated NiCl 2 small crystals and exhibit an essentially single mode nanoporous structure with an average pore radius of ∼75 Å. Xerogels heat‐treated at 973 and 1173 K are composed of aggregates of NiO crystals which only contain intergrain mesopores with radii exceeding 200 Å. A mixture of phases is observed in xerogels heat‐treated at 773 K. Xerogels with a water concentration of 2 mol/(mol NiCl 2 ) exhibit a narrow nanopore size distribution. Water concentrations higher or lower than 2 mol promote the formation of nanoporous structures with wider size distributions.