Abstract
Magnetic and dielectric materials can be blended to enhance absorption properties at microwave frequencies, although the materials may have relatively weak attenuation capabilities by themselves. The specific goal of this work is to enhance microwave absorption properties of materials with interesting dielectric behavior by blending them with magnetic materials based on transition metals. The synthesized Mn1−xZnxFe2O4 (x = 0.0 and 1.0) spinel ferrite nanoparticles (MZF NPs) were blended with commercial multi-walled carbon nanotubes (MWCNTs) in various proportions with a binder matrix of paraffin. This simple and efficient process did not cause a significant variation in the energy states of MWCNTs. MZF NPs were synthesized with a citric acid assisted sol–gel method. Their electromagnetic characteristics and microwave absorption properties were investigated. These properties were derived from the microwave scattering parameters measured via the transmission line technique by using a vector network analyzer (VNA) in conjunction with an X band waveguide system. The return loss (RL) values of the samples were obtained from the electromagnetic constitutive parameters (permittivity and permeability). The results indicate that the minimum RL value and the bandwidth change significantly with the amount of ferrite material in the blend. These results encourage further development of MWCNTs blended with ferrite nanoparticles for broadband microwave applications.
Highlights
Microwave absorbers are widely used in various defense and aerospace applications, such as designing “stealth” aircraft, camouflaging ground-based military assets against air-based radar surveillance, and constructing anechoic chambers
We investigated the effect of multi-walled carbon nanotubes (MWCNTs) on magnetic, dielectric, and microwave absorption properties of MnFe2 O4 and ZnFe2 O4 spinel ferrite radar-absorbing materials (RAMs) according to their mass fractions
No secondary impurity phase was detected, the absence of any additional peaks assigned to the graphite plane of MWCNTs
Summary
Microwave absorbers are widely used in various defense and aerospace applications, such as designing “stealth” aircraft, camouflaging ground-based military assets against air-based radar surveillance, and constructing anechoic chambers (where the radar signatures of aircraft and other targets are experimentally measured). The objective of “stealth” and camouflage designs is to reduce the radar cross-section (RCS) of potential targets, i.e., to make aircrafts, vehicles, or hardware systems less detectable to hostile radar observation systems. RCS: shaping the target so that the signal coming from the radar is guided in the desired directions (less “backscatter”) and using radar-absorbing materials (RAMs) for attenuating the incoming signal. In morphing applications, where large shape changes may be expected, the first approach will have obvious limitations. The design and application of RAMs has to be Aerospace 2017, 4, 2; doi:10.3390/aerospace4010002 www.mdpi.com/journal/aerospace
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