Solution combustion synthesized NiFe2O4/reduced graphene oxide composite nanomaterials: morphology and electrical conductivity

Ultrafine NiFe2O4 (T0) and NiFe2O4 / rGO composites have been synthesized by solution combustion method. The presence of rGO in the composite (33 wt.% (T1) or 66 wt.% (T2)) causes a decrease in the average particle size of the oxide phase from 16 to 10-11 nm with their transition to superparamagnetic with a decrease in the mixed spinel inversion degree. The SBET values for T1 and T2 are 180 and 315 m2/g, respectively, decreasing to 78 and 169 m2/g after annealing in the temperature range of 200-800 degrees C. Both micro- and small mesopores (size of 2.0-4.5 nm) have been observed for samples T2, while samples T0 and T1 are mainly mesopores. The small polaron mechanism of electrical conductivity is observed for pure spinel, when the electron hopping charge transport prevails for NiFe2O4 / rGO composites. It can be assumed that the GO component lowers the combustion reaction temperature and prevents particle agglomeration.