Implications from Broadband Microwave Absorption of Metal-Modified SiC Fiber Mats

Abstract

Understanding the physical requirements for a broad bandwidth is vital for the design of high-efficiency microwave absorber. Our recent works on silicon carbide (SiC) fiber mats-based absorbers imply that metal modification (e.g., Fe or Hf) could benefit their bandwidth effectively. For verification, we fabricated a Co/SiC fiber mat via a similar electrospinning process and subsequent pyrolysis at 1400 °C in Ar atmosphere. The results indicate that after Co modification, the SiC fiber mats show elevated permittivity and tangent loss. With a proper amount of Co adding, the mats could exhibit a wide bandwidth of around 8 GHz (ranging from 10 to 18 GHz) for effective absorption (reflection loss (RL) less than −10 dB) at 2.8 mm thickness. This is similar to our previous findings, confirming that metal modification could be an effective approach to extend the bandwidth of SiC mat absorbers. Explanations can be found through theoretical analysis with the quarter wavelength (λ/4) cancellation theory. It suggests that the declining permittivity (with the increase of frequency) is the key to keep the wavelength in material (λm) nearly unchanged within a frequency range. As a result, in this range, λ/4 cancellation could still be satisfied without changing thickness, which could explain the reasons for the broad bandwidth of metal-modified SiC fiber mats. With this model, it is further predicted that the effective absorption bandwidth could be even extended to be around 12 GHz with appropriate tangent loss. It should be emphasized that the implications obtained in this study could also be applicable to other dielectric absorbers. The requirement of permittivity and the proposed approach could serve as guidelines to achieve a wide bandwidth on a dielectric absorber relying on the λ/4 cancellation principle.

Ni Flower/MXene-Melamine Foam Derived 3D Magnetic/Conductive Networks for Ultra-Efficient Microwave Absorption and Infrared Stealth

“…So far, graphene [ 10 ], MoS 2 [ 11 ], CNT [ 12 ], SiC [ 13 ], and MXene have been recognized as representative candidate materials for high-efficiency EM absorbers. The two-dimensional structure of MXene is considered to be the most potential absorbing material due to its strong conduction loss and polarization loss provided by excellent conductivity and abundant surface groups (-OH, -O, -F) [ 14 ].…”

Flexible Ceramic Fibers: Recent Development in Preparation and Application

“…Polymer conversion is a method for preparing high temperature resistant FCFs from polymers containing silicon (Si), carbon (C), nitrogen (N) and other elements [133]. The polymer precursors are first processed into fibrous materials by fiber processing methods, such as electrospinning, solution Polymer conversion method is often used to prepare non-oxide ceramic fiber materials, and SiC fiber is the most studied [72,73,76,[134][135][136][137][138][139][140]. Hou et al [134][135][136][137]139] developed SiC fibers and a series of modified SiC fibers by electrospinning combined with polymer precursor conversion: First, the spinning solutions containing polymers, ceramic precursors and other ingredients such as modifiers are prepared, then the composite fibers are prepared by electrospinning process, and eventually the SiC fibers or modified SiC fibers are obtained by thermal curing and pyrolysis (Fig.…”

“…[132]. Copyright 2020, American Chemical Society Currently, iron (Fe) [139], Fe 3 Si [135], Fe 3 O 4 [154], hafnium carbide (HfC) [137], cobalt (Co) [134] have been reported as modifiers of SiC fibers. Taking HfC as an example, the addition of a small amount of HfC component in the SiC fibers can significantly improve the electrical conductivity of the fibers, thus improving the dielectric property and electromagnetic wave absorption property (Fig.…”

Flexible Mo2C‐Modified SiC/C Nanofibers for BroadBand Electromagnetic Wave Absorption

“…An excellent precursor of adjuvant should simultaneously have good stability, well solubility, and excellent spinnability, and the adjuvant had a synergistic effect for losing EM wave energy. [21][22][23] For instance, Hou et al reported a range of modified SiC/C fibers by adding metal acetylacetone complex (M(AA), M = Fe, Zr, Hf, or Co) to enhance their conductivity and EM wave absorption performance. [22][23][24][25] After researching a large number of pieces of literature, we choose the molybdenum acetyl acetone (MoO 2 (acac) 2 ) as adjuvant, due to the excellent spinnability and good solubility.…”

“…[21][22][23] For instance, Hou et al reported a range of modified SiC/C fibers by adding metal acetylacetone complex (M(AA), M = Fe, Zr, Hf, or Co) to enhance their conductivity and EM wave absorption performance. [22][23][24][25] After researching a large number of pieces of literature, we choose the molybdenum acetyl acetone (MoO 2 (acac) 2 ) as adjuvant, due to the excellent spinnability and good solubility. [26] What's more,…”