Preparation And Microwave Absorption Properties Of Fe-based Magnetic Particles

In recent years,considerable experimental investigations have been focused on the effective microwave absorption materials in order to solve the expended electromagnetic interference problems.Three microwave absorption mechanisms were found in the materials:dielectric loss,conduction loss and magnetic loss. Magnetic loss materials have been investigated broadly for their high complex permeability.Magnetic metals and alloys are ideal electromagnetic wave absorber materials because of higher complex permeability at high frequency.Metal Fe has higher saturation magnetization and lower coercive force,and iron alloys also attract much attention in the field of microwave absorption materials. Many research work have been done on Fe-Co,Fe-Ni and Fe-Si alloy,etc.However, only few reports about microwave absorption properties of Fe-Zr alloy were reported until now.We prepared Fe-Zr alloy by mechanical alloying method and studied the microwave absorption properties.Meanwhile,in order to find low density microwave absorb materials,we also explored the fabrication method to obtain ferrite/carbon nanotubes composites using improved co-precipitation method.The main results are: Fe₉₀Zr₁₀ alloy prepared by MA has high saturation magnetization and low coercive force.It exhibits irregular spherical particle after dry milling,and has good microwave absorption properties.The microwave absorption of Fe₉₀Zr₁₀ alloy/paraffin composite is less than -20 dB(more than 99%energy were absorbed) at frequency range from 4.5 to 17.6 GHz by changing ball-mill parameters and thickness. If NaCl was used as process control agent,Fe₉₀Zr₁₀ alloy shows flake morphology, and better microwave absorption properties can be obtained.It is possible to get absorption intensity less than -20 dB at frequency range from 2.8 to 15.9 GHz by changing ball-mill parameters and thickness.The microwave absorption mechanism of the composite is ferromagnetic loss.Multiwalled carbon nanotubes have been coated with cobalt ferrite and nickel zinc ferrite by an improved co-precipitation method.The MWCNTs coated with different ferrites could be used as a new low density microwave absorber.