The influence of the transparent layer thickness on the absorption capacity of epoxy/carbon nanotube buckypaper at X‐band

Abstract

Carbon nanotube films (BPs) as EMI shielding materials can be applied in electronic and communication devices due to their high electrical conductivity.Sandwich structures can offer excellent shielding effectiveness by introducing a wave-transmitting layer between conductive films. However, the optimization of the structure demands a deep investigation and plays a crucial role in the final shielding properties of the composites. In this work, BPs are incorporated into epoxy substrates with variable thicknesses (1-6 mm) to fabricate epoxy/BP sandwich structures. The morphology of the CNT films is analyzed by SEM, and the electrical conductivity of all prepared samples is measured by 4-point method. The electromagnetic tests are carried out in the X-band (8.2-12.4 GHz) through the scattering parameters. SEM images reveal a porous structure without visible agglomeration. The electrical conductivity of the BP reaches up to 996 S/m, whereas the values for epoxy/BP composites varies in the range of 8.51-3.13 S/m (1 to 3 mm). BP total shielding efficiency (SE T ) is approximately 14 dB along the X-band spectrum, with similar contributions of reflection and absorption losses. While, the composites show mainly absorbing behavior, especially in the thicker samples, with more significant SE T values (23.4 dB-6 mm).

Improved dispersion of reduced graphene oxide in benzoxazine composites via electrostatic interaction with M‐cresol

“…In order to further illustrate the utility and advancement of in‐situ synthesized rGO/mC‐A, the comparison of the dielectric constants and EMI SE performance of our results and previously reported values are shown in Figure 5. As a result, Figure 5E, F demonstrate the superiority of in‐situ synthesized rGO/mC‐A with in terms of relatively high dielectric constants and EMI SE values at low addition of rGO, compared to other systems, such as CNT/Epoxy, [ 40 ] MWCNTs/Epoxy, [ 41 ] MWCNT/PS, [ 42 ] MWCNT/PP, [ 43 ] TGO/SCI/Epoxy, [ 44 ] Graphene/Epoxy, [ 45 ] GNPs/Epoxy, [ 46 ] rGM/Epoxy, [ 47 ] GNPs/Epoxy, [ 48 ] Graphene/PU, [ 49 ] Graphene/TPU, [ 50 ] at 8.2–12.4 GHz.…”

Síntese e caracterização do polímero condutor polipirrol e do compósito condutor de polipirrol/caulinita/epóxi para aplicação em material absorvedor de radiação eletromagnética

“…Quando uma onda eletromagnética incidente atinge um material, duas ondas resultantes podem ser criadas, sendo uma porção transmitida através do material e outra refletida. A onda transmitida percorre o material em direção à sua segunda face, podendo ser absorvida nesse percurso, e a onda refletida no material retorna em direção contrária à incidência (REIS et al, 2021). Para que uma onda incidente se propague no material, deve existir o casamento de impedâncias entre o espaço livre e o material.…”

“…Quando a onda atinge a superfície oposta, parte pode ser transmitida para o espaço livre e parte refletida dentro do próprio material. Os parâmetros S são medidos pelos coeficientes de reflexão (S11, S22) e pelos coeficientes de transmissão (S21, S12) (REIS et al, 2021).…”