Preparation Of Three-dimensional Ni/c Composites And Microwave Absorbing Properties

In today's era of pluralism,we have a variety of high-tech products in our life,these high-tech products in the process of use will radiate electromagnetic waves to our living space environment,resulting in electromagnetic pollution problems.Electromagnetic wave absorption materials can effectively solve the problem of electromagnetic pollution.The mechanism of electromagnetic wave loss mainly depends on the mechanism of dielectric loss and magnetic loss.The composite of magnetic materials and carbon materials can have both dielectric loss and magnetic loss properties.It can also better meet the characteristics of the new absorbing materials "thin,light,wide and strong ".In this paper,magnetic metals are combined with carbon materials,and three-dimensional reticular magnetic carbon matrix composites are prepared by high temperature pyrolysis.The effects of different chemical compositions of the materials on the attenuation ability of electromagnetic waves are studied.The dielectric properties of the composites are adjusted by regulating the deposition of carbon nanotubes,and then the absorbing properties of the materials are optimized.Three-dimensional(3D)mesh Ni/C-X composite was successfully prepared by using metal nitrate pyrolysis to produce gas to form a 3D porous cavity carbon skeleton structure.The 3D reticulated porous cavity structure has multiple reflection mechanism,which can prolong the time of repeated oscillation between electromagnetic wave and material.By changing the mass ratio of Ni(NO3)2·6H2O to PVP,the ratio of magnetic metal to carbon component in the final three-dimensional reticulated Ni/C-X composite absorbing material is changed.The results show that the sample Ni/C-1 has the most excellent absorbing property when the mass feeding ratio of Ni(NO3)2·6H2O to PVP is1:1,that is,the maximum reflection loss is 18.0 GHz,the value is-20.7 d B.The effective bandwidth is 5.2 GHz(12.8 GHz-18.0 GHz)when Ni/C-1 composite thickness is 2.0mmIn order to further optimize the electromagnetic wave absorption performance of Ni/ C-X composites,based on the three-dimensional porous Ni/C-1 composites,the carbon nanotubes were loaded on the three-dimensional porous Ni/C-1 composites by vapor deposition method to improve the wave absorption performance of the materials.Melamine was used as the carbon source,and the amount of carbon nanotubes loadedwith three-dimensional carbon skeleton was adjusted by adjusting the amount of melamine added.By regulating the amount of carbon nanotubes deposited to modify the material,graphitic carbon nanotubes can effectively improve the impedance matching ability of the material.The study showed that the optimal feeding ratio of melamine to three-dimensional reticulated Ni/C skeleton was 6:1.In other words,Ni/C/CNTs-2composites have excellent electromagnetic wave absorption performance.When the thickness of Ni/C/CNTs-2 is 3.4 mm,the maximum reflection loss is 6.6 GHz,and the value is-69.3 d B.The effective bandwidth is 5.6 GHz(12.4 GHz-18.0 GHz)when Ni/C/CNTs-2 composite thickness is 1.8 mm.This study provides an important idea for the study of carbon-based magnetic absorbing materials in structure construction and component design.