Simple Hydrothermal Synthesis for Mesoporous Pebble-Like NiCo{sub 2}O{sub 4} Nanostructures and Their Attractive Magnetic Properties

The mesoporous pebble-like NiCo{sub 2}O{sub 4} nanostructures were smoothly obtained via a simple hydrothermal route and the succeeding annealing treatment. Various techniques, including XRD, SEM, TEM, Raman spectra, FTIR, and MH curves have been used to study the obtained products. The obtained results exhibited that the morphology of spinel NiCo{sub 2}O{sub 4} could be controlled by adjusting the content of cetyltrimethylammonium bromide (CTAB). The morphology of NiCo{sub 2}O{sub 4} nanostructures transformed from a 300-nm popcorn-like to 30–40-nm pebble-like nanostructure by changing the content of CTAB. Compared with the popcorn-like NiCo{sub 2}O{sub 4} nanostructures, the pebble-like samples showed effective blue shifting of Raman spectroscopy, which might be due to the nano-sized effect of NiCo{sub 2}O{sub 4} particles. Finally, vibration sample magnetometer (VSM) measurements indicated the samples transformed from weak ferromagnetic (popcorn-like) to paramagnetic (pebble-like) due to small particle size.