Electromagnetic, morphological and structural characterization of microwave absorbers based on POMA/magnetic filament composites

• Published in: Journal of magnetism and magnetic materials 2018-03, Vol.449, p.406-414
• Main Authors: de Souza Pinto, Simone, Machado, João Paulo Barros, Gomes, Newton A.S., Rezende, Mirabel Cerqueira
• Format: Article
• Language: English
• Subjects: Attenuation; Composites; Dielectric properties; Electromagnetism; Epoxy resins; Filaments; Magnetic fields; Magnetic materials; Magnetic permeability; Magnetic properties; Metallic filaments; Microwave absorber; Microwave absorbers; Microwaves; Morphology; Permittivity; POMA; Reflectance; Scanning electron microscopy; Structural analysis; Studies; X-ray diffraction
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2017.09.073

•This article focuses on recent progresses involving RAM based on hybrid composites.•Magnetic and dielectric properties of materials were combined in a hybrid composite.•Hybrid composites based on POMA and metallic filaments were prepared.•Electromagnetic properties of RAM show the influence of the hybrid composites.•Good results of microwave attenuation were determined for the studied absorbers. This study aims to combine dielectric and magnetic properties of different materials in an unique composite. For this, poly(o-methoxyaniline), POMA, was chemically synthesized in situ on magnetic metallic filaments (MF). The obtained composite was inserted into an epoxy resin matrix in the proportions of 40, 50 and 70%, in weight (wt%). The samples were characterized by scanning electron microscopy (SEM), X ray diffraction (XRD) and electromagnetic measurements. On the last case, the measurements considered the reflectivity and the complex parameters of electrical permittivity and magnetic permeability in the frequency range of 8.2–12.4 GHz (X-band). Specimens with different thicknesses were evaluated by reflectivity. XRD results show that the filaments are based on Fe-α steel and SEM analyses show the good incorporation of POMA/MF in the epoxy resin composite. The complex parameters show that the real component of permittivity shows the largest variation with the POMA/MF concentration increasing in epoxy resin and the loss tangent indicates that the magnetic losses are preponderant on dielectric ones. The reflectivity measurements show that the 5 mm-specimen with 50 wt% of POMA/MF presents the best result of attenuation (−21.5 dB, i.e. above 99% of attenuation). Already, the sample containing 70 wt% shows the worst performance (up to −9.0 dB). The increase of POMA/MF concentration in epoxy resin confers maximum attenuation values for less thick specimens. The results show that the combination of dielectric and magnetic materials in a composite contributes for the improvement of microwave absorbing performance, and extends the possibilities of RAM processing with different characteristics.