Carbon microcoils were deposited onto Al2O3 substrates using C2H2/H2 as source gases and SF6 as an incorporated additive gas in a thermal chemical vapor deposition system. At as-grown state, the carbon coils (d-CCs) show the diverse geometry. The geometry-controlled carbon microcoils (g-CMCs) could be obtained by manipulating the injection time of SF6 in C2H2 source gas. The d-CCs with polyurethane (PU) composite (d-CC@PU) and the g-CMCs with PU composite (g-CMC@PU) were obtained by dispersing d-CCs and g-CMCs in PU, respectively. The electromagnetic wave shielding properties of d-CC@PU and g-CMC@PU composites were investigated in the frequency range of 0.25 - 4.0 GHz. The shielding effectiveness (SE) of d-CC@PU and g-CMC@PU composites were measured and discussed according to the weight percent of d-CCs and g-CMCs in the composites with the thickness of the composites layers. On the whole frequency range in this work, the SE of g-CMC@PU composites was higher than those of d-CC@PU composites, irrespective of the weight percent of carbon coils in the composites and the layer thickness. Furthermore, we confirmed that the absorption mechanism, instead of the reflection mechanism, seemed to play the critical role to shield the EMI for not only the g-CMC@PU composites but also the d-CC@PU composites.
Due to their unique geometry and the chirality, carbon coils were supposed to have unique electrical and optical properties that could be used in nanoelectronics [
In general, the geometry of carbon coils (d-CCs) was known to be very diverse at as-grown state [
In this work, we investigated the shielding properties of the d-CCs and g-CMCs in the polymer composites. The d-CCs with polyurethane (PU) composite (d-CC@ PU) and g-CMCs with PU composite (g-CMC@PU) were obtained by dispersing d-CCs and g-CMCs in PU, respectively. The electromagnetic wave shielding properties of d-CC@PU or g-CMC@PU composites were measured according to the weight percent of d-CCs or g-CMCs in PU and the thickness of the composites layers in the frequency range of 0.25 - 4.0 GHz. Based on these results, we also discussed and compared the main shielding mechanism of d-CC@PU and g-CMC@PU composites.
For the deposition of d-CCs and g-CMCs, a home-made thermal chemical vapor deposition system was employed. C2H2, H2 were used as source gases. The incorporated additive gas, SF6, was continuously or on/off cyclic injected into the reactor during the reaction.
The detailed reaction conditions were shown in
For d-CC@PU and g-CMC@PU composites, d-CCs and g-CMCs were dispersed in PU solvent with the addition of dimethyl formamide (DMF) using ultrasonic system.