Preparation and characterization of Ni ferrite powders by urea decomposition

초록

A homogeneous precipitation method using urea is well known process for the formation of a particular form of metal hydroxides. Furthermore, it has been understood that this method is very effective to immobilize the precursor hydroxides on the carrier or substrate homogeneously. In this work, the effects of process parameters such as concentration ratio of urea and nickel(Ⅱ) iron(Ⅱ,Ⅲ) salt solutions, period of aging and the pH of the solution on the synthesis of Ni ferrite from aqueous solutions by decomposition of urea was investigated to develop porous ceramic fiber materials containing ferrite. The XRD patterns for the precipitation showed that at pH value lower than 6 both akagenite(beta-FeOOH) and Ni ferrite was formed simultaneously. At pH above 6 Ni ferrite single phase could be obtained. The precipitates heat treated at 300K under nitrogen atmosphere resulted in fine powder with BET areas ranged from 9 to 23m2/g and the spherical Ni ferrite particles showed uniform size of 200 nm in diameter. The effects of additional aging of the precipitates in organic solvents on the formation of Ni ferrite are also discussed in this work.