Preparation of spinel ferrite NiFe2O4 fibres by organic gel-thermal decomposition process

Functional spinel ferrite fibers are attractive for high-tech applications. The spinel NiFe₂O₄ fibres have been successfully prepared by the organic gel-thermal decomposition process from raw materials of Ni, Fe nitrate salts and citric acid. The gel spinning performance was a major factor for preparation of uniform gel fibrous precursors. The gel spinnability was related to the citrate-metal complex structure and linear-type structural molecules (C₆H₆O₇)₄NiFe₂]_n for the gel precursor was possibly formed during the complexation reaction between the citric acid and metal ions at pH 5. The composition, structure of the gel precursors and products derived from thermal decomposition of these precursors were characterized by FTIR, XRD, and SEM. The thermal decomposition process of the gel precursors was investigated by TG-DSC. The prepared spinel NiFe₂O₄ fibres having grain sizes of 60–70 nm were featured with diameters of about 1 μm, and aspect ratios up to 10⁶ (length/diameter).