Structural and magnetic properties of nanocrystalline ZnFe2O4 powder synthesized by reactive ball milling

The zinc ferrite (ZnFe2O4) has been obtained in nanocrystalline state by reactive milling in a high energy planetary mill from a stoichiometric mixture of oxides (ZnO and α-Fe2O3). A post milling annealing promotes the solid state reaction, improves the ferrite crystalline state and removes internal stresses. The formation of zinc ferrite was studied by X-ray diffraction and magnetic measurements. The chemical homogeneity and morphology of the powders were studied by X-ray microanalysis and scanning electron microscopy. The mean crystallite size after 16 h of milling was found to be 18 ± 2 nm. The lattice parameter of the obtained ferrite depends on the milling time and subsequent annealing treatment. It is lower than that of zinc ferrite obtained by the ceramic method. The evolution of the magnetization versus milling time is discussed in terms of milling induced cations reorganisation into the spinel structure

Consolidation and DC magnetic properties of nanocrystalline Supermalloy/iron composite cores prepared by spark plasma sintering

International audienceThe spark plasma sintering technique is used to prepare composite compacts starting from nanocrystalline Supermalloy and iron powder. The sintered compacts are investigated by X-ray diffraction, scanning electron microscopy, X-ray microanalysis, electrical resistivity and DC magnetic measurements. It is found that iron addition leads to an enhanced sintering process, the relative density of the compacts increases upon increasing iron content. The mean crystallite size of Supermalloy increases from 19 to 27±2 nm with increasing the iron content from 0% to 50 wt% (for identical sintering conditions). The interface created during the sintering process between iron and Supermalloy particles has a wide range of chemical composition including that corresponding to Rhometal like alloys. This leads to an increase of the electrical resistivity and coercivity of the compacts. The saturation induction and maximum relative permeability increase by 58% and 143% respectively, when the iron content increases up to 50 wt%