Facile synthesis of nickel nanoparticles supported on carbon and silica matrix via a novel silica sol-gel process

In this work, we introduce a modified novel silica sol-gel process to synthesize hexagonal close-packed (hcp) and face-centered cubic (fcc) nickel (Ni) nanoparticles supported on amorphous carbon and silica matrix. The supporting of amorphous carbon and silica can prevent the Ni nanoparticles from aggregating and being oxided which would result in the loss of their magnetism and dispersibility. The phase structure of the Ni nanoparticles which were obtained from the gels pyrolyzed from 250 to 350 degrees C is hcp structure, whereas that of the Ni nanoparticles pyrolyzed at 750 degrees C is fcc structure. The grain sizes of the hcp Ni nanoparticles calcined at 250 degrees C range from 5 to 20 nm in diameter, and that of the fcc Ni nanoparticles calcined at 750 degrees C range in 7-35 nm. The studies of magnetic properties of the hcp and fcc Ni nanoparticles show that both have quite different magnetic behaviors.