Fe3O4/reduced graphene oxide(r-GO) composites have potential applications in many fields due to their novel electrochemical and magnetic properties, such as electromagnetic shielding, magnetic, lithium ion batteries (LIBs), and catalyst materials. In this thesis, we have successfully synthesized varieties of the Fe3O4nanoparticles and Fe3O4/r-GO composites via a solvothermal method, respectively. The morphology and microstructure of the products were studied by employing scanning electron microscopy (SEM), transmission electron microscopy (HRTEM), X-ray diffractometer (XRD) and Raman spectra. The possible growth mechanism of Fe3O4nanoparticles and bowl-like hollow Fe3O/4on r-GO sheets were investigated preliminarily. Meanwhile, we also have studied the applications of the Fe3O4nanoparticles and hollow spheres, Fe3O4nanoparticles/r-GO and bowl-like hollow Fe3O4/r-GO composites in the microwave absorption materials and the anode material for lithium ion batteries. Additionally, we have explored the influence of morphology on the properties of the composites.The mainly works can be summarized as follows:1. Fe3O4nanoparticles and Fe3O4r-GO composites were synthesized via a solvothermal method in EG/DMF mixed solvent. The morphology of the products was studied by employing SEM and TEM, and the results show that the average size of Fe3O4nanoparticles is60nm and most of the nanoparticles are agglomeration. Fe3O4nanoparticles loacated on the surface of r-GO sheets are distributed uniformly and the average size is20nm, which demonstrated the addition of r-GO can inhibit the agglomeration of nanoparticles effectively. The charge-discharge performances of Fe3O4nanoparticles and Fe3O4/r-GO composites utilized as an anode material for LIBs were investigated, and the result indicated that the Fe3O4/r-GO composites show higher reversible capacity and better cycle performance than the pure Fe3O4nanoparticles.2. Fe3O4hollow spheres were synthesized by using P123as a "soft template" via a solvothermal method in EG solvent. The morphology of the products were studied by employing SEM and TEM, and the results showed that the size of Fe3O4hollow spheres with rough surface are mainly distributed in the range of200-600nm. whcih is consist of many small nanoparticles. Meanwhile, bowl-like hollow composites was synthesized with the presence of r-GO via a solvothermal method. We have studied the influence of different parameters including the feeding ratio, reaction time and temperature on the morphology of the products. The possible growth mechanism of bowl-like hollow Fe3O4on r-GO sheets was investigated preliminarily.3. It is believed that r-GO exhibits excellent microwave absorption property arising from residual defects and groups on the surface of nanosheet which can introduce defect polarization and groups’electronic dipole relaxation, due to its higher conductivity and hydroxyl, carboxyl, carbonyl and epoxy groups on the surface of r-GO. The Fe3O4/r-GO composites have both dielectric loss and magnetic loss, which is helpful to realize the impedance match. Moreover, reflection loss of r-GO appear in lower frequency range (8~12GHz) and reflection loss of Fe3O4commonly appear in higher frequency range, therefore the Fe3O4/r-GO composites are also helpful to increase bandwidth of the microwave absorption. The results demonstrate that the sample containing30wt.%as-synthesized bowl-like hollow Fe3O4/r-GO composites with a coating layer thickness of2.0mm exhibits a maximum absorption of24dB at12.9GHz as well as a bandwidth of4.9GHz (from frequency of10.8-15.7GHz) corresponding to reflection loss at-10dB. The calculated results demonstrate that the as-synthesized bowl-like hollow Fe3O4/r-GO presents a better microwave absorption performance than those of the pure r-GO, Fe3O4nanoparticles and hollow spheres, and the reported solid nano-Fe3O4/r-GO composites.4. The charge-discharge performances of Fe3O4hollow spheres and bowl-like hollow Fe3O4/r-GO composites utilized as an anode material for LIBs were investigated. The bowl-like hollow Fe3O4/r-GO composites have an initial discharge capacity of1568.6mAh/g and a Coulombic efficiency of77.3%. After55th cycles, the specific capacity of the Fe2O4/r-GO composites fades slowly and retains a value of940mAh/g. The results demonstrate that bowl-like hollow Fe3O4/r-GO composites have a higher reversible capacity, improved cycle stability and rate performance compared to those Fe3O4nanoparticles and hollow spheres and composites. |