Preparation Of Spinel Type Ferrite Fibres By Organic Gel-thermal Decomposition Method

Spinel type ferrite fibres are a novel kind of ceramic fibrous materials. These fibers can be used in high-tech and national defence fields because of its excellent refractory, corrosion resistant, inoxidizable and electromagnetic absorbing performances. The major aim for this investigation is to prepare ferrite fibres with thin diameter and high aspect ratios (length/diameter).In this thesis, the spinel type ferrite (CoFe₂O₄,NiFe₂O₄,MnFe₂O₄,ZnFe₂O₄) fibres have been prepared by organic gel-thermal decomposition method using metal salts and citric acid as the starting reagents. The gel precursors of CA-Co-Fe, CA-Ni-Fe, CA-Mn-Fe, CA-Zn-Fe were characterized by Fourier-Transform Infrared Spectroscopy (FT-IR), Thermo-Gravimetric (TG) and X-Ray Diffraction (XRD). It is reasoned that these gel precursors are amorphous substances. The carboxylic radiacl ligand reacts with metal ions in the aqueous solution by a single dentate model and the gel precursors consists of linear-typr structural moliculars. These gel precursors with a linear type structure exhibited good spinnability and the molecular formulas of gel precursors were suggested to be: (C₆H₆O₇) ₄Fe₂Co.9H₂O, (C₆H₆O₇) ₄Fe₂Ni.6H₂O,(C₆H₆O₇) ₄Fe₂Mn.7H₂O, (C₆H₆O₇) Fe₂Zn.6H₂O. All these four gel precursors could be drawed to long gel fibres.The gel fibre precursors have been investigated by Thermo-Gravimetric and Differential Scanning Calorimeter(TG-DSC) and the precursors experienced dehydration, decomposition, cracking and heat treatment conditions were determined for the subsequent thermal decomposition process.After the thermal treatment , spinel type ferrite fibres with thin diameter,high aspect ratios (length/diameter), smooth surface were obtained. These spinel type ferrite fibres were characterized by Scanning Electron Microscopy (SEM) and the fibres were featured with diameter<1μm, crystalline grains<100nm, length2O₄,NiFe₂O₄,MnFe₂O₄,ZnFe₂O₄ ferrite fibres, it is significant for the development of duality (Mn_0．5 Zn_0．5 Fe₂O4,Ni_0．5 Zn_0．5 Fe₂O₄ and so on), ternary ((NiZnCu)Fe₂O₄,(NiZnCo)Fe₂O₄,(MnZnCu)Fe₂O₄ and so on) spinel type ferrite fibres and other oxide ceramic fibres.