Studies On The Morphology Control And Electromagnetic Properties Of Magnetic Nanocomposites Based On Conducting Polymers

Conducting polymer based inorganic magnetic nanocomposites are electromagnetic composite materials obtained from conducting polymer and inorganic magnetic nanoparticles by certain ways.They have wide application prospects in military stealth and civil electromagnetic protection.It is becoming one of research focuses in fields of organic/inorganic hybrid functional materials.In this thesis,conducting polymer/Fe₃O₄ nano-composite materials with various morphologies were synthesized by soft template or hard template method using aniline and/or pyrrole as monomers,and Fe₃O₄ ferro-fluid as inorganic component.These morphologies include nano-particles,network nano-fibers,string bead nano-chains,network nano-branch,nano-tubes,nano-rods and nano-rods with hollow spheres in them.Systematic studies were made on the composition,structure, properties and functions of the composites.The possible formation mechanism was therefore proposed.The main research results were as follows:1.Polyaniline/Fe₃O₄ network nano-fiber composites with diameter size in 50-90 nm have been synthesized via emulsion polymerization method(soft template).The structure,morphology and crystalline forms of products were characterized by FT-IR,SEM and XRD,respectively. Room temperature conductivity,saturated magnetization and electromagnetic parameters were measured,and the absorbing properties of nano-composites were discussed.The maximum reflection loss was found to be -17.1 dB at 9.0 GHz,and the frequency width of loss over -10 dB was 1.0 GHz.2.Polypyrrole/Fe₃O₄ nano-particles,network nano-moniliforme, nano-rods composites with diameter size in 30-70 nm were successfully synthesized via emulsion polymerization method.The structure, morphology,crystalline forms and thermal stability of products were characterized by FT-IR,SEM,XRD and TGA,respectinely. Electromagnetic properties and absorbing properties were measured and studied,and the formation mechanisms were discussed.The maximum reflection loss was found to be -21.0 dB at 12.4 GHz,and the frequency width of loss over -10 dB was 3.0 GHz.3.Polypyrrole/Fe₃O₄ nano-tube composites with diameter size in 80-100 nm have been successfully synthesized via hard template method. The structure,morphology and crystalline forms of products were characterized by FT-IR,SEM and XRD,respectively.The specific surface area,electromagnetic properties and absorbing properties of composites were measured and studied,and the formation mechanism was discussed. The maximum reflection loss was found to be -24.2 dB at 11.0 GHz,and the frequency width of loss over -10 dB amounted to 5.8 GHz.4.Poly(aniline-co-pyrrole)/Fe₃O₄ network nano-fibers,nano-rods with hollow spheres in it,network nano-branch with diameter size in 30-80 nm have been successfully synthesized via emulsion polymerization method.The structure,morphology,crystalline forms and thermal stability of products were characterized by FT-IR,SEM,XRD and TGA,respectively.Electromagnetic properties and absorbing properties were measured and studied.The maximum reflection loss was found to be -36.5 dB at 9.0 GHz,and the frequency width of loss over -10 dB was 4.7 GHz.In conclusion,the conducting polymer/Fe₃O₄ nano-composites via template-directing in-situ chemical oxidative polymerization method exhibit the advantages of tunable morphologies and favorable electromagnetic properties.They show attractive application prospects both in military stealth and civil electromagnetic protection as novel microwave absorbing materials.