Electromagnetic characteristic and microwave absorption properties of carbon nanotubes/epoxy composites in the frequency range from 2 to 6 GHz

Abstract

The preparation and characterization of carbon nanotubes (CNTs)/epoxy composites were studied for microwave absorption, which frequency is from 2 to 6 GHz. The absorbing coating with a loading of 15 wt % CNTs/epoxy resin, which thickness is 3 mm, exhibited an absorbing peak of 10.5 dB at 3.85GHz. After being treated by HNO3–H2SO4 acid at the temperature of 100 °C, the real and imaginary part values of permittivity of CNTs have a larger increase in quantity, and the absorbing peak position moves to lower frequency of 3.35 GHz showing an increasing the dielectric loss in lower microwave frequency. Two-layer coating with CNTs/epoxy resin and graphite/epoxy resin composites have been also investigated in order to widen the frequencies range of CNTs microwave sorbent in the low microwave frequency application. The results indicated that two-layer coating (15 wt % loading CNTs/epoxy resin and 9 wt % loading graphite/epoxy resin) can obtain 2.4 GHz broad frequencies band for absorption of 5.0 dB. The absorbing peak intensity and position can be adjusted by changing the thickness of each layer coating in the case of fixed total thickness. The two-layer coating of 15 wt % loading CNTs/epoxy resin (dtop=2 mm) and 9 wt % loading graphite/epoxy resin (dbottom=1 mm) has a strong absorbing peak at 5.52 GHz and achieves an absorbing value of 20.79 dB.

Design and experimental verification of a thin broadband nanocomposite multilayer microwave absorber using genetic algorithm based approach

“…It is very difficult to achieve effective microwave absorption using absorber alone, so current need of research is to utilize the concept of multilayering in order to provide a thin broadband microwave absorber [2]. But selection of material for different layer as well as preference of layer for multilayered MAM structures is still a challenge for researchers.…”

Radar-cross-section reduction of wind turbines. part 1.

“…As carbon fiber is commonly used in wind-turbine blades, and its use will likely increase as blades grow larger, this technology has great potential to meet both mechanical and electrical design constraints with no modification to fabrication processes. Carbon is a common absorber material with natnral abundance that has been used as a loss mechanism in numerous forms [90,91,92,93,94,95,96]. Although time and scope prevented a more in-depth investigation of various carbon based absorbers (graph ene-based, nanostructures, fabrics) carbon based loss mechanisms should be investigated more thoroughly.…”

Designing of Nano Composites of Conducting Polymers for EMI Shielding

“…However, the higher energy of the quinoid section between them binds them together resulting in correlated motion. The net effect is the formation of a doubly charged defect acting like a single entity and delocalized over several rings (3)(4)(5) i.e., a bipolaron. The formation of bipolarons implies a net free energy gain in forming a closed shell defect from two open shell structures.…”

“…It has been shown recently that promising shielding performance could be achieved with composites comprising of an electrically non-conducting polymer matrix filled with conducting objects such as CNT-polymer composites, nickel ceramic composites etc. [5][6][7]. However, high filler contents are required from 10-15% for fibers and 30% for spheres to reach a percolation level leading to microwave losses.…”