The preparation of nickel nanorods in water-in-oil microemulsion

Nickel nanorods with a diameter of 8-10 nm and a length of 100-200 nm have been prepared by reduction of nickel chloride with hydrazine hydrate in water/butanol/potassium oleate/kerosene microemulsion. Transmission electron microscope (TEM) and X-ray diffraction characterizations indicated that these nickel nanocrystallites were rod-shaped with a face-center-cubic phase. The possible growth process of the particles was investigated. TEM images of the samples taken out from the reaction system at different periods revealed that as-prepared particles grew from spherical to rod-like shape. The size of the nanorods was influenced by the length of micelles and the molar ratio of water to surfactant. The effect of the weight ratio of cosurfactant to surfactant on the formation of the particles was also discussed. The coercivity of as-prepared nanorods reached as high as 332 Oe at room temperature, superior to that of bulk nickel and spherical nanoparticles with a mean size of 10 nm. (C) 2003 Elsevier Science B.V. All rights reserved.