Ligand Coprecipitation Thermal Decomposition Reduction Method To Prepare Porous Fibrous Iron-nickel Alloy Powder

With many special qualities,for example,small size,large specific surface area,active chemic property,special magnetism and etc,the ultra-fine iron-nickel alloy powders are widely used in wave-absorbing materials,magnetic materials,alloy plating materials and et al.After overviewed the preparation method of iron-nickel alloy powders in home and abroad,a new technique,called coordination precipitation-thermal decomposition reduction,is proposed to produce the fibrous-porous ultra-fine Fe-Ni alloy powder in the paper.According to the law of conservation of mass and law of simultaneous equilibrium,the mathematics model of Fe(Ⅱ)-Ni (Ⅱ)-NH₃-SO₄^2--C₂O₄^2--H₂O and Fe(Ⅱ)-Ni(Ⅱ)-C₂N₂H₈-SO₄^2--C₂O₄^2--H₂O thermodynamic equilibrium system is established,and the corresponding logarithms concentration of metal ions-pH value diagrams are also drawn.Based on these diagrams,the range of pH value in the coordination precipitation process is determined.Using this new precipitation method,the fibrous precursor powders of(Fe,Ni) complex are obtained.The effects of pH value,original metal ion concentration, temperature,charging rate,ripening time and surfactant on the morphologies,particle sizes and dispersion of precursor powders are studied on this paper systemicly.In addition,the fibrous precursor powders with fine dispersion are produced on optimum condition:pH value 6.2,the total metal ion concentration 0.8mol/L,temperature 60℃, charging rate 0.2L/h,ripening time 60min.Based on the results of analysis on the precursor powders by XRD,EDX,element analysis,IR spectra and TGA/DTA methods,it can be inferred that the precursor is one type of cobalt complex and the constitutional formula is Fe_xNi_1-xC₂O₄·zH₂O·nC₂N₂H₈.In this paper,the effects of morphologies of precursors,temperature and time during the thermal decomposition process on the morphologies of decomposed products are also investigated.It can be concluded that the morphologies of Fe-Ni powders greatly inherit their corresponding precursors.The fine fibrous-porous Fe-Ni powder with 25.99m²/g surface area could be obtained in weak reducing atmosphere while keeping temperature 420℃,heating rate 10～12K/min and time of heat preservation 30～45min.The structure of pores in Fe-Ni powders is capillary tube with open ports and the majority is mesoporous,the average aperture is about 3～4 nanometer.One patent has been applied and one paper has been published on the international meeting-TMS.