Preparation and Analysis of Nickel-Filled Polyurethane for Microwave Absorption in the K- and Ku-Band

This paper is focused on the investigation of a polymer–metal composite radio frequency absorber applications used for airborne, submarines, EMI shielding, etc. Nickel (Ni) metal powders having mesh size of 100 and 325 are used as fillers and finely dispersed in the millable polyurethane (m-PU) matrix to prepare flexible absorber sheets, using solvent casting process. The filler volume fraction is varied from 20 to 40 in the m-PU matrix to find the optimal filler loading based on density as 30 and 35 vol%. The samples are characterized by X-ray diffraction (XRD) to ascertain phase stability and scanning electron microscopy (SEM) for microstructure analysis, and tensile test is performed to determine mechanical properties and Fourier transform infrared (FTIR) for elemental composition analysis. The electrical permittivity, magnetic permeability and their losses are ascertained using vector network analyzer at the K- and Ku-band (12–27 GHz) to analyze the absorption.