Synthesis Method And Microwave Absorption Properties Of Soft Magnetic Nanoparticles/Polymer

Nowadays,our surrounding environment is filled with electromagnetic radiation pollution due to the development of electronic and communication industry.The demand of microwave absorption materials utilized in GHz range has been increasing in civil and military engineering field.Based on the electromagnetic mechanism,microwave absorption characteristics of materials depend on their dielectric properties as well as magnetic properties.It is no surprise that composite materials have wide modulation space of electromagnetic performance by optimizing configuration of dielectric and magnetic components in them.In this thesis,a series of FeNi and FeCoB nanoparticle films and corresponding composites are manufactured by electric field assisted deposition technology.The microstructure,magnetic properties and microwave absorption characteristics are studied by transmission electron microscope,superconducting quantum interference device and vector network analyzer.The mainly results are as follows:(1)The purpose of the application of electric field during deposition is to accelerate the condensed nanoparticles to form the compact films with in-plane magnetic softness.The overlarge electric field can induce the appearance of lattice kinks and shoulder characteristics of loops.The in-situ variable temperature TEM experiments with the measurement of magnetic properties indicated that excellent in-plane magnetic softness could be obtained by annealing.(2)The field assisted deposition technique can dramatically induce in-plane magnetic anisotropy of Fe50Ni50 nanoparticle films.Fe50Ni50 nanoparticles were deliberately deposited on the dielectric Teflon sheet to form composites.The application of electric field is an effective avenue to improve the GHz microwave absorption performance of our composites expressed by the movement of reflection loss peak from X to K bound for the composites.(3)Graphene was incorporated into polyimide resin to obtain Polyimide-Graphene polymer sheet via in-situ polymerization method.FeCoB nanoparticles were then deposited on the Polyimide-Graphene sheets by electric field assisted deposition technology to form FeCoB/Polyimide-Graphene ternary composites.It is found that the deposition of a small amount of FeCoB nanoparticles promote the improvement of electromagnetic properties by enhancing reflection loss about 10 dB.