Keywords: microwave absorption nano material
Summary:Microwave-absorbing materials (MAMs) are a kind of functional materials which can have absorb electromagnetic radiation in microwave region and thereofore applied to the surface of stealth military aircraft, to reduce the radar cross-section and thereby make them harder to detect by radar. They are also finding importance in commercial applications due to tremendous rise in the use of RF and microwave electronics in the modern day smart electronic devices where it is increasingly necessary to use MAMs for electromagnetic interference (EMI) shielding, reducing the reflected radiation from microstripradiators, electronics safety and human exposure mitigation etc. An efficient microwave absorber should be light weight, wide absorption bandwidth, strong absorption capability, thermally/chemically stable. Also it is imperative that synthesis of such materials is scalable in a manufacturing setting for mass production. The ferrites and ferromagnetic metals show excellent microwave absorption properties, but their application as microwave absorber is limited due to their high specific gravity and low absorption bandwidth and hard to mass produce. It should be noted that for many practical applications such as for stealth technology and the aerospace industry, the weight and thickness of the resultant microwave absorber is of prime importance. Carbon-based materials such as carbon nanotubes, graphene, graphite in combination with dielectric materials such as organic polymers are shown exhibit microwave absorption behavior, however poor chemical compatibility between an organic and inorganic component makes it harder to process. Here we report a scalable synthesis of a MAM material using graphene-based materials such as graphene nanopowder and inorganic dielectric material such as silicon carbide. We also report a process to convert synthesized composite into a conventional paint and process to use it in spray coating. Synthesis of graphene nanopowder and silicon carbide nanocomposite: A 0.3-0.5 and 0.1-0.2 wt% weight fraction of silicon carbide and graphene nanopowder are dispersed in ethanol using magnetic stirrer at room temperature. Once the solutes dispersed, the beaker mouth was closed to avoid evaporation and stirred it for 30 min and sonicated the prepared solution for 120 min to avoid agglomerations and to enhance homogeneity. The sonicated solution was transferred into a stainless-steel autoclave with Teflon coated tin for a hydrothermal reaction. The autoclave was kept under300- 400 ◦C for 12-15 h and then at room temperature to cool it down. In order to collect the GNP-SiC nanocomposite, the obtained solution after the hydrothermal reaction was centrifuged at 3000 rpm for 20 min, and the precipitated particles were washed several times with the distilled water. Finally, the washed black precipitate was dried at 60 ◦C for 3 h in a vacuum oven. The same procedure was followed for different wt % of GNP- SiC. After synthesising GSC nanocomposite powder, the graphene nanopowder + silicon carbide (GSC) paint is prepared by multiple methods detailed below. Each of the following method requires detailed experimental optimization with its composition in order to obtain the best electromagnetic reflection loss behavior in the X-band.