Preparation of nanosized NiFe2O4 particles by mechanochemical reaction(NiO þ a-Fe2O3) and subsequent thermal treatment was investigated using X-ray diffraction (XRD). Thermal treatment of the as-milled powder at 700℃ for 1h led to the formation of NiFe2O4 nanoparticles with an average crystal size of about 23nm. Effect of thermal treatment temperature on the crystal size of the nanoparticles was studied. The mechanism of nanoparticles growth was primarily discussed. The activation energy of NiFe2O4 nanoparticle formation during calcination was calculated to be 16.6 kJ/mol.

In2O3/CuO nanocomposites have been successfully synthesized by heating the precursor obtained via a mechanochemical reaction. The precursor and the nanocomposites were characterized using X-ray diffraction and scanning electron spectroscopy. The heat treatment of the precursor at 600℃ in air for 2h resulted in the formation of In2O3/CuO nanocomposites with an average crystal size of about 22nm, varying with the calcination temperature. The lattice parameter of the nanocomposites, lower than that of single In2O3, decreased with increasing the heat treatment temperature. The mechanochemical method is a novel, cheap and convenient technique suitable for large-scale synthesis of composite nanocrystallites. The mechanism of nanocrystallite growth is primarily investigated.

Pure and doped ZnS nanoparticles have been successfully synthesized via microwave irradiation. X-ray diffraction (XRD) analysis shows that the crystal size of the pure ZnS particles is about 6.5 nm. The ultraviolet–visible (UV–vis) absorption spectra of the samples indicate that the irradiation time shows no significant influence on the size of ZnS nanoparticles. It is also found that the luminescent properties of ZnS nanoparticles are greatly affected by either the microwave irradiation time or dopants of various metallic ions (Ag+, Cu2+, Ce3+ and Sn4+). The intensity of photoluminescence (PL) emission reaches its maximum and then decreases with prolonging the microwave irradiation time. The luminescence intensity of ZnS nanoparticles doped with 0.2% cerium, which is stronger than that of other dopants, is about two times that of sample doped with 0.2% Ag+ and 1.6 times that of pure ZnS nanoparticles. But when the amount of doped cerium reaches 0.4%, the emission efficiency is lower than that of pure ZnS. All peak emission wavelength is 450 nm, indicating that the luminescent centers of various metallic ions are not formed within the doped ZnS nanoparticles.

In2O3 nanoparticles were synthesized by a mechanochemical reaction (InCl3·4H2O+ NaOH) with NaCl as a diluent and subsequent calcination, producing In2O3 nanoparticles (26.7nm) at 500℃ for 1h. The size of the nanoparticle increases with increasing calcination temperature.

Cobalt oxide (Co3O4) nanoparticle was synthesized by thermal treatment of the precursor obtained via mechanochemical reaction of Co(NO3)2+6H2O with NH4HCO3. Calcination of the precursor at 300 jC resulted in the formation of Co3O4 nanoparticles of 13 nm in crystal size. The precursor was examined by simultaneous differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The Co3O4 nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Effect of calcination temperature on Co3O4 crystal size was discussed. The activation energy (E) of Co3O4 nanoparticle formation during thermal treatment was calculated to be 15.9 kJ/mol.