Synthesis And Magnetic Research Of Magnetic Composite Nanoparticles And Chain-like Co Nano-materials

As materials science and nanometer technology unceasing development, some newnanometer scales of composite functional material gradually become a more and moreattention by people of research direction in the material science field. Magnetic materials andother functional materials synthesis of magnetic composite nanometer material is one of them.In this paper, three special structure of magnetic composite nanometer material Fe/CNTs,SiO₂@CoFe₂O₄, SiO₂@BaFe₁₂O₁₉were synthesized with different methods. Meanwhile,chain-like Co structure was synthesized under different induced magnetic field. The research ofthe special structure of magnetic nanometer material is mainly the preparation technology andmagnetic property. Main content is listed as follow:1. We propose an effective technique for the synthesis of Fe nanoparticles （Fe-NPs）decorating MWCNT samples of various concentrations through a facile solvothermal method. Weonly need to control the initial mass ratio of ferrocene to CNTs. A detailed test and analysis to thesample magnetism performance was implemented by XRD, FTIR，SEM and PPMS. The resultshows that the Fe/CNTs composites display good ferromagnetic properties at room temperature,with a saturation magnetization of125emu/g-Fe and a coercivity of276Oe. The Curie temperatureof the sample is about1038K, slightly lower than that （1043K） of the bulk iron.2. The monodisperse CoFe₂O₄nanoparticles were prepared by the coprecipitation method.The monodisperse CoFe₂O₄nanoparticles have been coated with silica using the improved methodof hydrolysis of TEOS method. In the experiment, we just change the concentration of TEOS andadding number can control the thickness of SiO₂shells. Through the research SiO₂@CoFe₂O₄nanoparticles of microstructure and magnetic properties can view, we found that coating magneticnanoparticles with amorphous silica can effectively reduce interparticle magnetic interactions andprotect nanoparticles from oxidation and reduction.3. In order to measure the Curie temperature of barium ferrite BaFe₁₂O₁₉nanoparticles moreaccurate, study the finite-size effect, and reduce the particles growth in high temperaturemeasurement.We coat the nanoparticles with amorphous silica by using the above TEOShydrolysis method.The result indicated that the Curie temperatures of the package nanoparticlescan obtain more accurate. We find that the Curie temperature of the nanoparticles decreases withdecreasing particle size and in accordance with the scaling theory. 4. Chain-like Co stuctures connected with nano-spheres were synthesized under inducedmagnetic field. The morphology and magnetic properties are characterized and also dicuss theassembling mechanism of the magnetic induction.