Preparation, Characterization and Electromagnetic Loss Properties of Polymer-Spinel Ferrite Nanocomposites

Preparation, Characterization and Electromagnetic Loss Properties of Polymer-Spinel Ferrite Nanocomposites
　　Magnetic nanocomposites can be controlled and tailored to provide the desired mechanical, physical, chemical, and biomedical properties depending on the final applications. Magnetic polymer nanocomposites are obtained as the magnetic nanoparticles are embedded in polymer matrix. since they combine the advantages of the inorganic materials (mechanical strength, good chemical resistance and thermal stability, etc.) and the organic polymers (flexibility, dielectric, ductility and good processibility, etc.), the nanocomposites represent as a class of functional materials. The coating of ferrite nanoparticles with polymers affords the possibility of minimizing Alnico magnets agglomeration in large-scale commercial synthesis of nanocomposite materials. The nano-size spinel ferrite is an excellent absorbing material for electromagnetic wave using for electromagnetic interference (EMI) and shielding because of its characteristic electromagnetic loss properties. Based on the aim above, we combine the nano-size spinel ferrite with different kinds of polymers, such as polyacrylate, polyacrylamide and polyaniline, to improve electromagnetic loss properties of the compound materials for more broad application in the present paper. In the paper, the main investigation content is showed as follow:The nano-size NiZnCu-ferrite and NiZnCr-ferrite doped with different content of La are synthesized by the citrate precursor sol-gel method; polyacrylate/NiZnCu-ferrite, polyacrylamide/NiZnCu-ferrite and polyaniline/polyacrylamide/NiZnCu-ferrite nanocomposites are prepared by in situ emulsion polymerization of monomers in the presence of NiZnCu-ferrite colloid.The microstructure of the nano-size NiZnCr-ferrite doped with different content of La is characterized by X-ray diffractometer (XRD) and transmission electron microscope (TEM).
　　The results show that the rare earth La can restrain the growth of the nano-size ferrite. Meanwhile, the results of Impendence/Materials analyzer in the 1 MHz～1 GHz ranges show that the La weaken the ability of electromagnetic loss for the magnetic materials; In addition, the ability of electromagnetic loss for NiZnCu-ferrite improves obviously compared with NiZnCr-ferrite, so the NiZnCu-ferrite is chosen as the magnetic particle in the nanocomposites.The microstructure, micromorphology and thermal stability of all the nanocomposites are characterized by Fourier http://www.999magnet.com/
 transform infrared spectra (FT-IR), XRD, TEM, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), respectively. The results of XRD and FT-IR indicate the formation of nanocomposites. That the thermal stability of nanocomposites has been improved is revealed by TGA. The images of TEM and SEM show that the magnetic particles are dispersed homogeneously in the continuous polymer matrix.The electromagnetic loss properties of PAA/NiZnCu-ferrite, PAM/NiZnCu-ferrite and PANI/PAM/NiZnCu-ferrite nanocomposites are measured by the Impendence/Materials analyzer in the 1 MHz-1 GHz ranges. The results show that the magnetic loss is dominant for PAA/NiZnCu-ferrite and PAM/NiZnCu-ferrite nanocomposites, and the ability of magnetic loss improves with the content of magnetic particles increase. Compared PAA/NiZnCu-ferrite nanocomposite with PAM/NiZnCu-ferrite nanocomposite under the same condition, the later can incorporate more ferrite and the coating effect is better than the former obviously; The PANI/PAM/NiZnCu-ferrite nanocomposite not only hold the excellent magnetic loss properties, but also improve the electronic http://www.999magnet.com/
 loss properties obviously. And the ability of electronic loss increases with the PANI content.