Synthesis And Microwave Absorption Performance Of Polyaniline/Ferrite Nanocomposites

In recent years, with the fast development of information technology, the electromagnetic pollution is worsening, which affects the normal running of the electronic equipment and interferes with the radar, broadcast services, and satellite digital data transmission sharply. Therefore, the electromagnetic pollution is getting more and more attention of all countries. Now, the research and development of a new type of microwave absorption material with a cheap price, effective microwave absorption and wide-band frequency become the important direction of electromagnetic wave absorption materials. Polyaniline (PANI) is one of the most promising conducting polymers with excellent chemical stability, simple synthesis method, easy obtainment of the raw material, and high electrical conductivity. The composites containing PANI and ferrite nanoparticles have the advantages of both polymer and ferrite inorganic materials, and novel performance, and they are a type of multi-functional material.Based on the application advantages of polymer/inorganic materials and graphene, in the dissertation, PANI/ferrite/(grapheme) or graphene/ferrite composite nanomaterials with different morphologies and dimensions have been synthesized, including one-dimensional (ID) PANI/Ni0.5Zn0.5Fe2O4(NZFO) hybrid nanorods,2D PANI/NZFO and PANI/GO/SrFe12O16(SrFO) composite nanoslices, and3D porous rGO/SrFO composite hydrogel. Their electromagnetic wave absorption properties were also investigated.The main results can be summarized as follows:1. PANI/NZFO ferrite composite nanoslices were successfully prepared by two steps. Firstly pure PANI nanoslices were synthesized via ultrasound assisted chemically oxidative polymerization. Then the nanoslices were used as templates to induce the formation of PANI/NZFO composites under hydrothermal conditions. The investigation results indicate that PANI nanoslices were coated by the NZFO nanoparticals with average size of18nm, and there exists the coordination interaction between M2+(M=Fe, Ni, Zn) on the surface of NZFO nanoparticles and PANI. The PANI/NZFO composite nanoslices show better microwave absorption properties than pure PANI or pure NZFO. These composite materials may be applied in microwave absorption and electromagnetic interference shielding fields.2. The novel uniform PANI/NZFO one-dimensional (ID) hybrid nanorods were firstly in situ synthesized by ultrasonic-assisted magnetic field guidance methods. The as-synthesized hybrid nanorods possess uniform shape, adjusted magnetic properties, high saturated magnetization and high coercivity. The electromagnetic data demonstrate that hybrid nanorods present stronger reflection loss and a wider absorption band in comparison to pure NZFO. PANI/NZFO hybrid nanorods with addition of59%NZFO exhibit excellent microwave absorption performances, with a maximum reflection loss (RL) of-27.5dB observed at6.2GHz, and the widest absorption band (RL<-10dB) is8.1GHz, corresponding to a matching thin thickness of2mm. Besides, microwave absorption mechanism of hybrid nanorods was explored further.3. Using GO nanosheets as soft template, the PANI/SrFO/GO composite nanoflakes were in situ synthesized by chemical oxidation polymorization method. The results show that SrFO nanoparticles and PANI were tightly bound to the surface of graphene sheets to form interlayer structure. The formation mechanism of the as-synthesized composites was discussed. The coordination effect, π-π interaction and hydrogen bonding exist among polyaniline, SrFO nanoparticles and graphene nanosheets. The microwave performance measurement of the products shows that PANI/SrFO/GO-1(weight ratio of aniline/GO/SrFO is10:5:5) and PANI/SrFO/GO-2(weight ratio of aniline/GO/SrFO is10:5:10) both possess excellent electromagnetic loss performances, with a maximum absorption value of about37dB at9.1and6.4 GHz, respectively. And their-10dB bandwidth surpassed10GHz in2-18GHz ranges.4. A novel3D porous rGO/SrFO composite hydrogel was synthesized by one step hydfothermal method in the presence of graphene oxide nanosheets and SrFO nanoparticles due to the hydrophobic effect and π-π interaction between rGO nanosheets. The microwave absorbability of products with the different of SrFO contents were tested in the frequency range of2-18GHz. The results show that the product with weight ratios of10:4for GO to SrFO exhibits strongest wave absorption performance. The maximum absorption reaches51dB at frequency of3GHz, and the widest absorption band (RL≤-10dB) is10.5GHz, corresponding to a matching thin thickness of1mm. It is evidently that the3D porous structure of composite hydrogel plays an important role in cavity resonator and lowers microwave reflectivity. It is a way to design and prepare3D porous lightweight and high performance electromagnetic wave absorption materials based on graphene and other nanomaterials.