Preparation Of Composites From Nickel-slag-derived Fe₃O₄ And Conducting Polymers And Research Of Microwave Absorption Properties

Nickel slag contains a variety of valuable metal elements,so its comprehensive utilization is attracting more and more attention.The total iron content of nickel slag is close to 40%.If these iron resources are recycled and designed as electromagnetic functional materials,it will provide a new way for the comprehensive utilization of nickel slag.In this paper,the magnetite crystals extracted from nickel slag according to the group’s previous work and conductive polymers（polypyrrole,polyaniline）were used as the raw materials to prepare microwave absorbing materials by in situ oxidation polymerization.The effects of the composition on its microwave absorbing properties were investigated.The specific content are given as follows:（1）ENS-Fe₃O₄/PPy composites were prepared by in-situ oxidative polymerization,with which polypyrrole（PPy）and Fe₃O₄particles extracted from nickel slag（ENS-Fe₃O₄）were used as magnetic loss medium.The effects of pyrrole content on the microwave absorbing properties of the composite were studied.The results show that when the mass ratio of Fe₃O₄to pyrrole is 2:1,the minimum reflection loss of the composite reaches-24 dB at 15.2 GHz,with the matching thickness of 1.75 mm and the effective absorption bandwidth of 5.44 GHz.The introduction of polypyrrole enhances the dipole polarization and interface polarization of the composite material.The loss of the composite material to electromagnetic waves mainly comes from the magnetic loss and the dielectric loss.The magnetic loss is dominated by natural resonance and exchange resonance,and the dielectric loss is Dipole polarization and interface polarization dominate.（2）ENS-Fe₃O₄/PANI composites were prepared by in-situ oxidative polymerization,with which polyaniline（PANI）and Fe₃O₄particles extracted from nickel slag were used as magnetic loss medium.The effects of aniline content on the microwave absorbing properties of the composite were studied.The results show that when the mass ratio of Fe₃O₄to aniline is 5:1,the minimum reflection loss of the composite reaches-38.9 dB at 15.8 GHz,with the matching thickness of 1.5 mm and the effective absorption bandwidth of 4.24 GHz.The introduction of polyaniline enhances the dipole polarization and interface polarization of the composite material.The loss of the composite material to electromagnetic waves mainly comes from the magnetic loss and the dielectric loss.The magnetic loss is dominated by natural resonance and exchange resonance,and the dielectric loss is Dipole polarization and interface polarization dominate.（3）ENS-Fe₃O₄/PPy/PANI composites were prepared by a stepwise in-situ oxidative polymerization,in which Fe₃O₄particles extracted from nickel slag were used as the core and PPy as the first-step shell and PANI as the second-step shell.The effects of aniline content on the microwave absorbing properties of the composite were studied.The results show that when the mass ratio of ENS-Fe₃O₄/PPy to aniline is 10:3,the minimum reflection loss of the composite reaches-43.57 dB at 14.88 GHz,with the matching thickness of 1.5 mm and the effective absorption bandwidth of 4.24 GHz.The loss of the composite material to electromagnetic waves mainly comes from the magnetic loss and the dielectric loss.The magnetic loss is dominated by natural resonance and exchange resonance,and the dielectric loss is Dipole polarization and interface polarization dominate.（4）Comparing the three composite materials,ENS-Fe₃O₄/PPy has the widest effective absorption bandwidth（5.44GHz）,but the minimum reflection loss is not ideal.ENS-Fe₃O₄/PANI and ENS-Fe₃O₄/PPy/PANI have relatively good minimum return loss（-38.9dB and-43.57 dB）and good matching thickness（1.5mm）,but the effective absorption bandwidth is slightly disadvantaged.