Microwave absorption in epoxy composites filled with MoS2 and carbon nanotubes

Abstract

In this study, the microwave absorbing properties of epoxy composites filled with micro-sized MoS2 and carbon nanotubes (CNT)/MoS2 were investigated in the frequency range of 1–67 GHz. Sample characterization was performed using electron microscopy and Raman spectroscopy methods. Direct current (DC) conductivity, complex permittivity, and shielding properties of composite materials with 50 wt. % of MoS2 and 1.5–2 wt. %CNT/50 wt.%MoS2 were measured. The permittivity of 50 wt. % MoS2/epoxy composite was found to be equal to 7.3, decreasing monotonically down to 4.5 at 67 GHz, while the imaginary part is equal to 1 and does not change. The addition of 2 wt. % of CNTs increases the real part of permittivity εr′ up to 30 at 1 GHz (13 at 67 GHz) and also leads to a large increase of the imaginary part of permittivity, with the most pronounced relaxation peak εr′′=10 at 10 GHz. Such an increase of dielectric loss correlates with the increase of DC conductivity up to 3.2 × 10−5 S/m as compared to the two-phase composite 50 wt. %MoS2/epoxy (σdc = 1.7 × 10−9 S/m). It was shown that 50 wt. %MoS2/epoxy composite exhibited an effective microwave absorption bandwidth of 9.9 GHz at the sample thickness of 2.0 mm with reflection loss minimum of -20.0 dB at 51.5 GHz. 2 wt. %CNT/50 wt. %MoS2/epoxy composite with a thickness of 0.9 mm showed a reflection loss minimum of −38 dB at 20.2 GHz with the absorption bandwidth of 3.68 GHz. The influence of sample thickness on position, width, and depth of EMR absorption maximums for the composites filled with MoS2 and mixed filler CNT/MoS2 was also determined.