Carbon coated Co–SiC nanocomposite with high-performance microwave absorption

Abstract

A carbon coated Co-SiC nanocomposite was fabricated via in situ pyrolysis of methane on a hierarchical Co3O4-SiC nanostructure, which was obtained by hydrothermal synthesis. By the reduction of methane, the Co3O4 was in situ converted to cobalt nanoparticles, and coated by carbon or filled in the CNTs. The as-prepared composite exhibits excellent microwave absorption performance in the frequency range of 2-18 GHz. When the match thickness is 1.8 mm, the composite has a reflection loss value below -10 dB in the range 12.2 to 18 GHz, which nearly covers the whole Ku-band (12-18 GHz). When the thickness is 2.6 mm, the reflection loss value below -10 dB distributes at 8.2-11.5 GHz, covering most of the X-band (8-12 GHz). Moreover, by further tuning the match thickness, the composite can selectively absorb some certain frequency bands of microwaves.

Fe‐, Co‐, and Ni‐Loaded Porous Activated Carbon Balls as Lightweight Microwave Absorbents

“…It is known that e' and e'' represent the energy storage( polarization)a nd dissipation capability (dielectric loss), respectively. [49,50] The permittivity of MAMs mainly originated from electronic polarization, ion polarization, and intrinsic electric dipole polarization, [51,52] which are determined by the nature,c rystal structure, size, and shape of the nanomaterial and its microstructure. [40,41] From the free-electron theory, [53] e'' = 1/2p1fe 0 ,where 1 is the electric resistivity and e 0 is the permittivity in vacuum, it can be speculated that al ower e'' value indicates ah ighere lectric resistivity, which may be attributed to the different metal and/or metal oxidesp articles dispersed in the PACB composites.…”

A three-dimensional graphene/Fe3O4/carbon microtube of sandwich-type architecture with improved wave absorbing performance

“…4(c), the μ′ values of the graphene/Fe 3 O 4 /CMT (10:1:0.5, w/w/w) are to be slightly higher than those of CMTs/Fe 3 O 4 (10:1, w/w) . While the μ″ values of the graphene/Fe 3 O 4 /CMT increases from 0.01 to 0.06 at 2-18 GHz, in which appears obvious resonance peaks at higher frequency from a magnetic loss due to a domain wall resonance as reported in the carbon/Ni, Co/CNTs and so on [29][30].…”

Strong and Thermostable Boron-Containing Phenolic Resin-Derived Carbon Modified Three-Dimensional Needled Carbon Fiber Reinforced Silicon Oxycarbide Composites with Tunable High-Performance Microwave Absorption Properties

“…Similarly, the ε" values for the composites shown in Figure 8b also increase first and then decrease with increasing PIP cycle number, whose value strongly depends on the electrical conductivity of the tested sample, and thus the variation tendency for ε" value should be attributed to the different content SiOC introduced after different PIP cycle numbers, which could be confirmed by the above result of density for different composites (in Figure 5). In addition, some peaks around at 4, 12, and 14 GHz should be ascribed to the resonance behaviors [38,39]. Besides the above real and imaginary parts of complex permittivity, another critical electromagnetic parameter for an absorber is the dielectric tangent loss (tanδ e = ε"/ε'), which presents the microwave attenuation capability, and thus the value of tanδ e was calculated and is displayed in Figure 8c.…”