Realizing significant dielectric dispersion of composites based on highly conducting silver-coated glass microspheres for wide-band non-magnetic microwave absorbers

Abstract

Achieving broadband microwave absorption with non-magnetic thin coatings is quite challenging due to the lack of dielectric dispersion in most materials. In this work, significant microwave dielectric dispersion (SMDD) in a broad bandwidth was realized using silver-coated glass microspheres (GM@AgCPs) as fillers at a near percolating volume fraction in composites. First, the dense silver shells of GM@AgCPs are critical to enhancing the dielectric properties of the composites at low frequency owing to their strong interface polarization, oscillation resonance and coupling interaction. Second, GM@AgCPs exhibit long effective paths for electron oscillation, which result in long relaxation times. Therefore, the strong dielectric responses are not extended to the high frequency because the excited electrons on GM@AgCPs cannot respond rapidly to changes in the external electromagnetic field, leading to significant microwave dielectric relaxation. Subsequently, high-performance microwave absorbing materials (MAMs) were for the first time demonstrated by SMDD coupled with the quarter-wavelength resonance in a broad bandwidth. Consequently, the as-obtained MAMs with a matching thickness of 2.2 mm at a volume fraction (V) of 45% exhibited an absorption bandwidth of at least 11.8 GHz for reflection loss ≤−8.0 dB, which greatly surpasses the performance of their literature dielectric counterparts. Our work has potential important applications in electromagnetic compatibility and stealth.