Preparation And Microwave Absorbing Performance Of Ni/RGO,Ni?OH?₂/RGO Composite

Originally, the research about absorption materials was for the purpose of military stealth technology, but with more and more electronic equipment applied in people's daily life, the absorption material is not only very important in military field, it also plays an significant rule in some other civil areas, such as human electromagnetic protection, information security and videocast. Ferrite, as a traditional absorber, because of its high density, poor absorption effect in low frequency, can no longer meet the "thinner thickness, lighter weight, broader bandwidth and higher absorption" requirements. Graphene is considered as a potential absorbing material owning its unique properties such as low density, huge specific surface and electron which relaxation polarization can easily occurred in it. In addition, nickel has drawn attention of scholars recently, because nickel has a higher curie temperature and magnetization intensity, and it remains a high complex relative permeability at high frequencies, comparing with ferrite.In this paper, we use graphene oxide which has excellent ions adsorption capacity as precursor to synthesize Ni/RGO and Ni?OH?₂/RGO compound via chemical vapor deposition?CVD? and hydrothermal method respectively. We examined the influences of several primary processing parameters during the preparation on the microstructures of products, and the microwave absorption properties were also evaluated. The main results are as following:Ni/RGO can be successfully prepared by CVD method, through analyzing the effects of the Ni?NO3?2 concentration, reduction temperature and reduction time, we found that the quantity of nickel particle increases as the Ni?NO3?2 concentration rises, and two different sizes were observed when the Ni?NO3?2 concentration is too high. At the concentration of 1M Ni?NO3?2, the size of nickel particle is highly uniform, about 10nm. In addition, excessive heat would cause the inhomogeneity of nickel particle,650? is an relatively appropriate reaction temperature in this study.There is a strong correlation between the Morphology of Ni?OH?₂ and the ratio of SO42- mole number to OH- mole number?The valve of R?. When the R valve is 2:1, the Ni?OH?₂ is Two-dimensional structure, when the R valve is 1:1, the Ni?OH?₂ is observed in the shape of nanobelt, and the form of Ni?OH?₂ will transform into polygon when the valve of R is 1:2.Under the conditions that the R valve is 1:1, Ni?OH?₂ of amorphous state will be gained when the temperature is too low, only the temperature reaches a certain valve of 160?, crystalline Ni?OH?₂ can be prepared, furthermore, the regularity and crystal integrity increases as the hydrothermal time rises, the Ni?OH?₂ nanobelt is about 200nm in length, 10nm in width when the hydrothermal time is 6h.The Ni/RGO and Ni?OH?₂/RGO both show great microwave absorption property. When the Ni?NO3?2 concentration is 1M, thermal reduction is 700? and reduction time is 6h, the max valve of reflection loss of Ni/RGO can reach -42dB in 2.0mm thickness. The max valve of reflection loss of Ni/RGO is -43dB, under the conduction that the R valve is 1:1, hydrothermal temperature is 160? and hydrothermal time is 6h. Ni/RGO has strong absorption at lower frequency range while Ni?OH?₂/RGO possess relative broader absorption bandwidth. As a result, we can choose among them as microwave absorbers according to the practical requirements.