Preparation And Properties Of Spinel Ferrite/Polypyrrole Composites

With the rapid development of science and technology,the research on magnetic absorbing materials has become more and more important.Magnetic materials such as ferrites are the most important materials of which many researches have been focused on.Spinel ferrite is widely used in catalysis,magnetic storage,biomedicine and other fields because of its superior performance.It also has excellent microwave absorbing performance.Among a variety of different forms of ferrites,magnetic hollow microspheres have attracted wide attention due to their high specific surface area and excellent properties in micro-encapsulation.Compositation of ferrite and polypyrrole can improve its magnetic and absorbing properties.In this experiment,glucose was used as the carbon source substrate,copper nitrate was used as the copper source,and silver nitrate was used as the silver source.Spinel Cu/RFe₂O₄（Ag/RFe₂O₄）was successfully synthesized with hydrothermal method.Fe in spinel was further substituted by cerium to form Cu/RFe_2-xCe_xO₄（R stands for metal ions such as Ni、Co、Zn,X=0.005,0.01,0.015,0.02）.The product not only has good magnetic properties and optical properties from copper nanoparticles,but also has the corresponding chemical properties from rare earth elements.Polymerization of pyrrole monomer under low temperature conditions makes the polypyrrole（PPY）uniformly distributed on the surface of the ferrite powder,and the polypyrrole-coated ferrite composite was obtained.Cu/CoFe₂O₄ has excellent magnetic properties and microwave absorbing properties.Its saturation magnetization Ms,residual magnetization Mr,and coercive force Hc are 34.7emu/g,17.1 emu/g,and 515Oe,respectively.The maximum dielectric loss It is 1.129,the maximum magnetic loss is 1.141,and the maximum power absorption coefficient is0.54mm^-1.The absorbing and magnetic properties of Cu/NiFe_2-xCe_xO₄ are significantly improved with the increase of the Ce³⁺doping amountuntil the best result at x=0.02with the maximum dielectric loss of 0.553,the maximum magnetic loss of 1.162,and the power absorption coefficient of 0.327mm^-1;after the spinel ferrite sample is coated with polypyrrole,the specific saturation magnetization and specific residual magnetization becomes smaller,and the coercive force and the microwave absorbing ability increase significantly.Maximum Hc value of 545Oe is achieved by PPY/Cu/CoFe₂O₄.Among PPY/Cu/RFe₂O₄（R-Ni、Co、Zn）,PPY/Cu/Ni_0.5Zn_0.5Fe₂O₄ has the best microwave absorbing performance.The maximum dielectric loss,magnetic loss,and power absorption coefficient are 1.458,1.984,and 1.762 mm^-1,respectively.Among PPY/Ag/RFe₂O₄（R-Ni,Co,Zn,Cu）,PPY/Ag/Zn_0.5Co_0.5Fe₂O₄ has the best microwave absorbing performance,and its maximum dielectric loss,magnetic loss,and power absorption coefficients are 1.183,0.091,and 0.505mm^-1.PPY/Cu/RFe₂O₄（R-Ni、Co、Zn）has better magnetic and microwave absorbing properties than PPY/Ag/RFe₂O₄（R-Ni、Co、Zn、Cu）.At the same time,copper metal is cheap and easily available with abundant resources.This experiment uses hydrothermal synthesis,which can reduce the reaction temperature and greatly shorten the reaction time,thereby achieving the effect of energy saving.