Synthesis, Microwave Electromagnetic, and Microwave Absorption Properties of Twin Carbon Nanocoils

Abstract

Twin carbon nanocoils (T-CNCs) were synthesized by means of acetylene decomposition over nickel nanoparticles. From the TEM image, one can see the growth of carbon nanocoils from the opposite sides of a nickel nanodisc, making an interangle of 180 degrees. We examined the microwave electromagnetic (EM) and microwave-absorbing properties of the as-prepared and annealed (1400 degrees C in Ar) T-CNCs systematically. A composite containing the as-prepared T-CNCs (15 wt %) and paraffin exhibited strong microwave absorption in a frequency range of 2 to 18 GHz. Over an absorber of double-layered composite (2.5 and 3.5 nim thickness), an absorption bandwidth of ca. 10 GHz corresponding to reflection loss below -10 dB can be obtained. We found that the magnetic parameters of the composite are low and suggest that the good absorption properties of T-CNCs should be attributed to dielectric rather than magnetic loss. It was observed that the as-prepared T-CNCs are superior to the annealed T-CNCs in microwave absorption ability, and such a phenomenon is interpreted in terms of the defect and graphitic nature of the materials. We also demonstrated that the complex permittivity and electric conductivity of T-CNCs can be controlled via annealling of T-CNCs at high temperature

Growth of morphology-controllable carbon nanocoils from Ni nanoparticle prepared by spray-coating method

“…Carbon nanocoils (CNCs) are attracting increasing interest due to their unique helical morphology and have wide applications such as resonators [1], microwave absorbers in stealthy coating [2] and electrodes in supercapacitors [3], etc. Generally, both morphology and quality of CNCs can be dramatically influenced by the size and composition of metal catalyst commonly used in chemical vapor deposition (CVD).…”

Controllable synthesis of porous C x N y nanofibers with enhanced electromagnetic wave absorption property

“…In addition, the decrease of ε′ and ε′′ as a function of frequency is defined as frequency dispersion [44], which could help to improve the impedance matching condition between the C x N y nanofibers and the ambient air. The excellent EM wave absorption of the as-prepared C x N y nanofibers could be mainly controlled by the dielectric loss of the EM waves, resulting form the doping of N atoms in the carbon structure.…”

High Frequency Properties of Carbon Nanotubes and Their Electromagnetic Wave Absorption Properties

“…However, many researchers have reported that CNTs exhibit weak ferromagnetic properties (Tang et al, 2008;Zhang et al, 2000;Kudo, et al, 2007). For MWCNTs, Hc value is about 127.5 Oe.…”