Preparation of SiC Nanowire/Carbon Fiber Composites with Enhanced Electromagnetic Wave Absorption Performance

Abstract

Herein, the SiC‐coated carbon fiber decorated with SiC nanowire (SiCnw/CF) composites are successfully prepared by one‐step chemical vapor infiltration (CVI) process. Microstructures, the formation mechanism of SiCnws, thermal stability performance, and electromagnetic wave (EMW) absorption performance of the composites are investigated in detail. In particularly, benefiting the dielectric loss and conductive loss, the SiCnw/CF composites obtained at 1500 °C exhibit superior EMW absorption property with the minimum reflection loss (RL) of −36.5 dB with the effective absorption band of 5.5 GHz at a thickness of 1.88 mm. This work provides a simple way to obtain and design the CF‐based materials with good microwave absorption.

Morphology‐controlled preparation and tunable electromagnetic wave absorption performance of manganese dioxide nanostructures

“…As shown in Figure 12, when the hydrothermal reaction temperature increase, the RL min values of other samples are −47.94 dB@5.04 GHz@3.4 mm, −36.20 dB@2.8 GHz@4.8 mm, and −48.94 dB@11.28 GHz@3.0 mm, respectively. It is clearly presented in Figure 11 that the reflection loss peak gradually shifts to lower frequency with the increase of the absorber thickness, which is in agreement with the quarter wavelength theory 34,38 . The inferior EMW absorption property should be attributed to poor impedance matching ( Z m = Z in / Z 0 ), which is significantly beyond 1 (Figure 11F).…”

“…It is clearly presented in Figure 11 that the reflection loss peak gradually shifts to lower frequency with the increase of the absorber thickness, which is in agreement with the quarter wavelength theory. 34,38 The inferior EMW absorption property should be attributed to poor impedance matching (Z m = Z in /Z 0 ), which is significantly beyond 1 (Figure 11F). However, the impedance matching is improved after the δ-MnO 2 phase transfers to α-MnO 2 phase, as shown in Figure 11G-J.…”

“…Besides, the enhanced dielectric loss could be put down to the urchin‐like structures with radial growth of MnO 2 nanorods, which can be regarded as the vast antennas to take in the EMW and transfer it to vibrating microcurrent. To further understand the resonant peaks in ε′′ curves, the Debye relaxation should be mentioned to explain this phenomenon as follows 34,35 : $$\begin{equation}{\left( {\varepsilon ^{\prime} - \frac{{{\varepsilon _{\rm{s}}} + {\varepsilon _\infty }}}{2}} \right)^2} + {\rm{\;}}{\left( {\varepsilon ^{\prime\prime}} \right)^2} = {\left( {\frac{{{\varepsilon _{\rm{s}}} - {\varepsilon _\infty }}}{2}} \right)^2}\;\end{equation}$$…”

Quinary High‐Entropy‐Alloy@Graphite Nanocapsules with Tunable Interfacial Impedance Matching for Optimizing Microwave Absorption

“…For the impedance matching behavior, it carried out the value of | Z in / Z 0 | between 0.8 and 1.2 which is regarded as an excellent impedance matching behavior. [ 40,42 ] As shown in Figure 3 and Figures S20–S23 (Supporting Information), it can be noted that the nanoparticles when compositing with Mn can reach a better matching performance than other elements. Moreover, the impedance matching behaviors ( Δ ) at different thicknesses (0–5 mm) have also been investigated based on the electromagnetic parameters (Figures S20–S23 and S26, Supporting Information), in which the value below 0.4 represents a proper impedance matching property.…”

Multiscale SiCnw and carbon fiber reinforced SiOC ceramic with enhanced mechanical and microwave absorption properties

“…So, the SiOC/SiCnws/CF‐1200°C‐1 is used for another PIP process for improving the impedance matching. Herein, the impedance matching could be calculated by the following equation 33 : $$\begin{equation}{Z_{\rm{m}}} = {Z_{{\rm{in}}}}/{Z_0}\end{equation}$$…”