Preparation and magnetic properties of spinel-type ferrite fibres

The spinel-type MeFe2O4(Me=Zn,Ni0.5Zn0.5, Ni0.4Zn0.4Cu0.2) ferrite fibres with diameters of 0.5-20.0 mu m and high aspect ratio (length/diameter) were successfully prepared by the organic gel-thermal decomposition process using metal salts and citric acid as raw materials. The structure, thermal decomposition process and morphologies of the gel precursors and the fibres derived from thermal decomposition of these precursors were characterized by FT-IR, XRD, TG-DSC and SEM, and the electromagnetic performance of ferrite fibers were measured by VSM. The results show that linear-type structural molecules for the gel precursor is formed by a single dentate liganding type or bidentate-chelating mode among citric acid and metal ions during the complexation reaction, and the gel composed of these linear-type molecules exhibits a good spinning performance. The MeFe2O4(Me=Zn, Ni0.5Zn0.5, Ni0.4Zn0.4Cu0.2) ferrite fibres all exhibit a soft magnetic performance, and chemical composition, grain size and morphology have considerable influence on the magnetic properties of these ferrite fibres. The saturation magnetization(M-s) of ZnFe2O4, Ni0.5Zn0.5Fe2O4 and Ni0.4Zn0.4Cu0.2Fe2O4 fibres are 2.6, 12.7 and 40.0A.m(2).kg(-1), and coercivity of these fibres correspondingly are 4.77, 5.82 and 4.04kA.m(-1), respectively.