MATERIAL CHARACTERIZATION FOR MICROWAVE ABSORBING AND SHIELDING APPLICATIONS

The rapid advancement and widespread of microwave and RF-communication systems have contributed to an abundant rise in electromagnetic energy radiation in our living environment. Such an increase in microwave sources is due to the development and advancement in communication techniques (mobile phones, laptops, and antennas for aeronautics or automobile) and electronic warfare in the military field (radar and satellite). To address these concerns, EM absorbing materials are used to ensure public safety and the safety of military operations. Various types of EM absorbing materials made up of composite materials have been produced and studied. This thesis discusses the microwave properties of different sets of composite materials. Firstly, the samples of polymer with varying concentrations of weight (wt. %) (1%, 5%, 8%, and 10%) of Multi-Wall Carbon Nanotube (MWCNT) are studied. Secondly, the CNT sample is functionalized with metal alloy oxides, such as Cobalt oxide, Cobalt Iron oxide, and Iron oxide in three different concentrations (5%, 10%, and 20%) are embedded in a polyurethane matrix are investigated. The dielectric properties of the samples are studied using an open-ended coaxial probe technique in the wide frequency range (5 - 50 GHz). The reflection loss at normal incidence is then used to calculate the composites\u27 absorption efficiency, a minimum reflection of -43dB was obtained at 8 GHz frequency with a small thickness of 3.5mm. The results reveal that by varying the CNT content and material thickness, the spectrum range of absorption can be modified. The absorption efficiency of polyurethane/CNT composites was improved by functionalizing CNT with various alloyed metals. Thus, functionalized composites can be used as a lightweight material for microwave absorption and shielding