Effect of MWCNT length and coating cycles on electromagnetic wave absorption of MWCNT-coated honeycomb core fabricated by simple dip-drying process

초록

Stealth technology can improve the mission capability and survivability of military weapon systems by avoiding detection by enemy radar. In this study, lightweight multi-walled carbon nanotube-coated honeycomb cores (M-HC) were fabricated for use in electromagnetic interference (EMI) shielding materials and structures. The electrical conductivity of M-HC increased with the number of coating cycles, and long-MWCNT (LM) exhibited higher conductivity than small-MWCNT (SM) at the same coating cycle. At $f_{center}$fcenter, the normalized real part of the permittivity decreased at ten and five coating cycles for SM and LM, respectively, before increasing again, while the loss tangent initially increased and subsequently decreased. The development of the MWCNT network led to a transition from dielectric polarization to electron conduction. In addition, the absorption of M-HC increased up to five coating cycles but then decreased due to enhanced conductivity, which favored reflection over absorption. At $f_{center}$fcenter, the absorption after five coating cycles was 84.6 % for SM and 70.2 % for LM, respectively. The scattering ratio (SR) also increased with the number of coating cycles, primarily due to enhanced electrical conductivity and reduced skin depth. While the increase in SR was mainly driven by the absorption component (SRA), the reflection component (SRR) also increased, leading to a trade-off that requires balance between reflection and absorption. At twenty coating cycles, the transmittance of LM-HC was reduced to 0.0001%, while the specific RSR (SRSR) was 160 cm3 g-1, demonstrating excellent lightweight electromagnetic shielding performance. Therefore, M-HC can serve as an excellent component for lightweight radar-absorbing structures with high specific RSR in aerospace and military applications.

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