The Study Of Microwave Absorption Performance On Graphene-based Nanocomposite

Microwave absorption material (MAM) is of great importance in both civil and military applications. Considerable attention has been paid to the development of MAM with low density, high stability and excellent absorption performance.Magnetic metal is usually to be utilized as MAM. However, its absorption propery is limited since magnetic loss is the only mechanism for dissipating microwave energy. If dielectric loss is involved in, the absorption performance of magnetic metal would be further improved. In this dissertation, we investigated the dielectric, magnetic and microwave absorption properties of Fe@Graphene core-shell structure and FeNi3-Graphene nanocomposite. The main results are as follows:1. Microwave absorption performance of Fe-Graphene core-shell structure.We synthesized Fe@Graphene core-shell structure by hydrothermal reaction and following reduction in H2. The experimental results show that the dielectric property of the core-shell structure is totally different from that of pure Fe and mechanically-mixed Fe-Graphene composite. In the core-shell structure, the difference of work function and the chemical interaction at the interface of Fe-graphene introduce free charges to graphene. The charges vibrate with the stimuli of the microwave and bring about polarization, increasing the value of the real part of permittivity (ε’). Furthermore, the relaxation of polarization results in the decrease ofwith the increase of frequency, i.e., dielectric dispersion. Meanwhile, the motion of free charges would lead to the absorption of microwave energy. Thus, the dielectric loss is also enhanced. The increased ε’ and dielectric dispersion give rise to a good impedance matching and the enhanced dielectric loss is more favorable for the dissipation of microwave energy. The aforementioned factors would account for the excellent microwave absorption performance of the core-shell structure. In addition, the strong hybridization between the graphene π and Ni3d valence-band states at interface leads to the transfer of partial charge, which would give rise to the change of microwave absorption performance. This work provides a novel idea for exploring high-performance microwave absorption material as well as expands the application field of graphene-based materials.2. Microwave absorption performance of FeNi3-Graphene nanocomposite.The microwave absorption performance of FeNi3-Graphene nanocomposite with different concentration of graphene was studied. Compared with pure FeNi3, FeNi3-Graphene compositie shows quite different microwave dielectric response and exhibits excellent microwave absorption property. Moreover, the absorption performance is influenced by the concentration of graphene. This work indicates that the co-growth of FeNi3and graphene can intrinsically change the dielectric property of FeNi3-Graphene nanocomposite and lead to a high-performance microwave absorption nanocomposite. Moreover, the physical mechanism of the improved absorption performance needs to be further investigated.