Fabrication And Electromagnetic Properties Of Porous Carbon / Iron Nano-composites

With the development of modern military and electronics industries, new kinds of radar absorbing materials are required to follow the "thin, light, wide, strong" direction. Current frontier researches on nano-materials and porous materials provide new ideas and approaches for the design and the fabrication of new absorbing materials. It can be envisaged that radar absorbing composites which contain some structure and materials can be designed and fabricated by using porous materials as template and artificially introduction of necessary materials and components.Based on the above thoughts, a function composite containing fractional pores and carbon/metal nano-structures was prepared by adopting natural porous material - activated carbon powder as template, introducing metal inorganic precursor which can catalyze formation and growth of carbon nano-structure, taking the amorphous carbon in activated carbon for carbon source, and controlling the chemical coupling process of metal precursor and amorphous carbon. By using thermal gravimetric analysis and X-ray diffraction test, the components and changes during the preparation process were analyzed; by using transmission electron microscopy, structure and morphology of carbon nano-structure were studied; by using nitrogen adsorption test, pore structure was characterized; by using coaxial determination, electromagnetic parameters of paraffin-based composites in 2~18GHz were measured; by using arch beam auto sweep frequency system, the electromagnetic waves reflection loss of the epoxy-based composites in 2~18GHz were measured. The main conclusions are as follows:C/Fe nanocomposite has the features of hierarchical pore and the carbon/metal nano-structure: C/Fe nanocomposite, based on activated carbon, inherited and retained the original natural micro-porous and nano-porous structure, and formed carbon/metal nano-structures in the matrix of amorphous carbon. When the heat treatment temperature is during 700~1000°C, the higher the heat treatment temperature is, the higher the degree of graphitization of carbon is, and the more the carbon nano-band structure formed. The growth mechanism of C/Fe nanocomposite is in line with "dissolution - precipitation" model. C/Fe nanocomposite magnetic properties relates to porous structure and carbon/metal nanostructures which can be controlled by heat treatment temperature. When the heat treatment temperature is during 700~1000°C, the real and imaginary parts of C/Fe nanocomposite permittivity is along with the increasing of heat treatment temperature, while the changes in permeability very small. Radar absorbing performance of C/Fe nanocomposite is related with fabrication process, structure, content and dispersion in the matrix. With the heat treatment temperature increasing, the graphitization of amorphous carbon and the formation of carbon/metal nanostructures improves the dielectric constant and the dielectric loss, expands the frequency range of low reflection loss. But the impedance matching of C/Fe nanocomposite is poor. Multi-layer absorbing composite is more likely to achieve the impedance matching of C/Fe nanocomposite and air, thus letting more electromagnetic waves get into the material, and making absorbing bandwidth wider and the reflection loss peak larger.In this paper, the research of a new kind of radar absorbing material was explored meaningfully, and provided theoretical basis and practical methods for research of new absorbing materials and application in related fields.