Abstract
Cobalt oxide, hematite, and Co
3
O
4
/α-Fe
2
O
3
nanopowders (NPs) have been successfully synthesized by hydrothermal technique. Co
3
O
4
is well crystallized in spinel cubic structure, while the hematite possesses the rhombohedral structure. The mixture of these two materials gave spinel cobalt ferrite. The average crystallite size calculated from Scherer’s equation was 49 and 34 nm for Fe
2
O
3
and Co
3
O
4
, respectively, while it is decreased to 19 nm for the Co
3
O
4
/α-Fe
2
O
3
NCs. This reduction is probably attributed to the high enthalpy of formation of the mixture in comparison with the two other materials. Scanning electron microscopy and transmission electron microscopy photographs indicate that the Co
3
O
4
/α-Fe
2
O
3
NPs are composed of homogenous spherical grains and small agglomerated crystallites. All the prepared samples exhibited a superparamagnetic behavior with very low remanence and coercivity. The origin of the superparamagnetism may be related to the uncompensated surface spin and tiny size of the nanoparticles. The magnetization at saturation of the mixture is strongly enhanced to 45.7 emu/g after it was around 2 emu/g for both Co
3
O
4
and hematite. BET analysis showed that the composite had a high surface area (around 60 m
2
/g) compared to Co3O4 and hematite. This makes Co
3
O
4
/α-Fe
2
O
3
a good candidate for several applications such as drag delivery, supercapacitors, and magnetic resonance imaging.