Electromagnetic wave absorption property of carbon microcoils in 12–110 GHz region

Abstract

The electromagnetic (EM) wave absorption properties in the gigahertz region (12–110 GHz) of carbon microcoils (CMCs) with a three-dimensional-helical/spiral chiral structure (1–10 μm coil diameter and 0.1–10 mm coil length) were examined using the open space method. It was found that the target value of reflection loss, over −20 dB (above 99% absorptivity) necessitated for commercial applications, could be obtained for EM absorption composites of only 1–2 wt % addition of CMCs in a polyurethane matrix for the 30–35, 50–55, 75–80, and 95–100 GHz bands. A CMCs addition of more than 3 wt % resulted in a decrease of the EM wave absorptivity, because of the increase in the reflection of the EM waves. Multilayer absorption composites showed a higher EM absorptivity than that of single-layer composites. The longer the coil length, the higher the absorptivity could be obtained. The absorption mechanism of the EM waves by CMCs is discussed.

Growth and Properties of Carbon Microcoils and Nanocoils

“…These properties have led to the evaluation of helically shaped filaments with nano and micrometer coil diameters for use as tactile sensors, electromagnetic interference (EMI) shielding, and field emission devices [7,10,11]. In the early years, despite reports by several groups of successfully growing coiled carbon filaments, reproducing published results remained challenging.…”

“…Motojima et al [10] reported 12-110 GHz electromagnetic (EM) wave absorption of double helical CMC/polyurethane. As illustrated in Figure 19, the EM wave absorption property of this CMC composite was compared to other types of carbon composites.…”

“…have been found to possess attractive morphologies, as well as excellent mechanical and electrical properties including superelasticity, low Young's modulus, relatively high electrical conductivity, and good electromagnetic (EM) wave absorption [7][8][9][10]. These properties have led to the evaluation of helically shaped filaments with nano and micrometer coil diameters for use as tactile sensors, electromagnetic interference (EMI) shielding, and field emission devices [7,10,11].…”

Development of ceramic microcoils with 3D-herical/spiral structures

“…(b) Electromagnetic properties: 23), 24) It is considered that the CMC is a promising candidate as a novel EM absorber, especially in the GHz range, because of its micro-coiling morphology. That is, the micro-coiling morphology is the most effective and ideal one for the generation of inductive current by Faraday's Law resulting in absorption of EM wave.…”

Preparation and Characterization of Carbon Microcoils (CMCs)

“…3.3.4 Electromagnetic Properties: [21][22][23][24] It is considered that the CMCs are promising candidates for use as EM absorbers, especially in the gigahertz (GHz) range, because of its micro-coiling morphology. In other word, the micro-coiling morphology is the most effective and ideal morphology for the generation of an inductive current by Faraday's Law resulting in absorption of EM wave.…”