Investigation of the properties of carbonyl iron-based microwave-absorbing composites

This paper presents the results of experimental and numerical investigations of the electrophysical properties of carbonyl iron–based composite materials designed for applications in the microwave frequency range. The main objective of the study was to determine the frequency-dependent dielectric and magnetic permeabilities of microwave-absorbing polymer composite materials (PCMs) with varying carbonyl iron content and to establish an extended database of material parameters suitable for accurate modeling and design of microwave devices. The measurements were performed using the Nicholson–Ross–Weir (NRW) method implemented in custom software developed by the authors. The software includes a de-embedding module that eliminates the influence of connecting waveguide sections, thereby improving the accuracy of the calculated electromagnetic parameters. The measuring setup and the data-processing algorithms were verified using reference dielectric and magnetic materials (PTFE, polystyrene, and air), demonstrating good agreement with tabulated data. The proposed approach enables reliable determination of the frequency dependences of the real and imaginary parts of the dielectric and magnetic parameters in the 8–12 GHz range. The effect of the mass fraction of carbonyl iron (40–80 %) on the electromagnetic properties of the composites was investigated. It was found that a composition containing 70 wt.% carbonyl iron provides the optimal balance between manufacturability and microwave absorption performance, exhibiting a maximum absorption level of approximately –28 dB and stable electrophysical characteristics. The developed experimental–computational methodology extends the available reference data on microwave-absorbing composites, complements the standard specifications (OST 107.460007.006–92), and provides a foundation for constructing a digital database of material parameters applicable to computer-aided design (CAD) systems for microwave components and devices.