Synthesis of nickel ferrite nanoparticles by sol-gel method

NiFe2O4 nanoparticles were prepared by the sol-gel method using polyacrylic acid (PAA) as a chelating agent. it was shown that pure spinel NiFe2O4 nan oparticles with a diameter of 5 similar to 30 nm and a specific surface are a of 20.0 similar to 55.2 m(2)/g could be produced by calcining the gel pre cursors with various molar ratios of PAA to total metal ions (0.5 similar t o2.0) in air at 300 degreesC for 2h. As the molar ratio of PAA to total met al ions increased, particle sizes decreased but the crystallinity increased , revealing PAA not only worked as a chelating agent to disperse the cation s homogeneously but also contributed its combustion heat to increase the cr ystallinity of NiFe2O4 nanoparticles. Moreover, the magnetic analysis showe d the resultant NiFe2O4 nanoparticles might be superparamagnetic. Their sat uration magnetization (0.19 emu/mol at 298 K) was slightly lower than that for bulk materials due to small size and increased slightly with decreasing the temperature below 360 K (C) 2001 Elsevier Science Ltd. All rights rese rved.