Effect of Particle Size and MWCNTs Content on Microwave Absorption Characteristics of Cobalt

• Published in: IEEE transactions on magnetics 2022-10, Vol.58 (10), p.1-16
• Main Authors: Jamwal, Udeshwari, Singh, Dharmendra, Yadav, K. L.
• Format: Article
• Language: English
• Subjects: Absorption; Bandwidths; Broad bandwidth; Coating; Cobalt; Dielectric losses; Genetic algorithms; high-energy ball milling; Magnetic hysteresis; Magnetic losses; Magnetism; Microwave absorbers; Microwave absorption; Microwave attenuation; Microwave communication; Microwave imaging; Microwave theory and techniques; Morphology; Multi wall carbon nanotubes; multiwall carbon nanotubes (MWCNTs); Particle size; reflection loss (RL); Structural design; Thickness
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2022.3199582

In today's ever-developing electronic world, tremendous efforts are being made to develop highly efficient microwave absorbing materials with thin thickness and broad bandwidth while maintaining a simple manufacturing procedure. Since so much study is devoted to structural and component designing of microwave absorbers, the mechanism of microwave absorption still has potential for improvement. It is critical to have fundamental mechanistic knowledge of microwave absorption by absorbing materials with diverse types of geometries and components. It is also important to explore the influence of different physical/chemical characteristics of absorbing materials on microwave absorption performance. The methodical and thorough examination of these issues may provide internal information on the interaction of the microwave absorber's components and subsequent structural design. Therefore, in this article, by taking cobalt (Co) as the base material, an attempt has been made to comprehend the microwave absorption mechanism of Co milled at various times, which results in changes in particle size and morphology. A significant change in the microwave absorption of Co has been observed with changed morphology after milling. The enhancement in microwave absorption characteristic of milled Co with the addition of different wt% of multiwall carbon nanotubes (MWCNTs) has also been analyzed. MWCNTs in milled Co increase interfacial polarization and multiple reflections in the sample, resulting in microwave attenuation. The prepared Co/MWCNTs composite samples yielded excellent bandwidth with low coating thickness. The effective bandwidth of 10 GHz (3.73-13.73 GHz) was obtained for the composite of 20 h wet-milled Co and 2 wt% MWCNTs, with a coating thickness of 2.5 mm. To further enhance the microwave absorption bandwidth and reduce coating thickness, a genetic algorithm (GA)-assisted multi-layering approach has been implemented for designing triple-layer microwave absorbers. The optimized triple-layer result for combination 5W4-10W1-20W2 shows an effective bandwidth of 13.65 GHz (4.35-18 GHz), with an overall coating thickness of 2.31 mm.