Electromagnetic wave absorption properties of porous carbon/Co nanocomposites

Abstract

Porous carbon/Co nanocomposites were fabricated by a sol-gel method. The electromagnetic parameters were measured in the 2–18GHz range. Compared with porous carbon composite, porous carbon/Co nanocomposite has larger dielectric loss due to the enhanced interfacial polarization relaxation loss and Ohmic loss. The maximum reflection loss of the porous C(Co) nanocomposite can reach 40dB at 4.2GHz with 5mm in thickness and the primary microwave absorptive mechanism is ascribed to the dielectric loss. The effect of porous structure on microwave absorption property of the carbon/Co nanocomposite was also discussed.

Ultra-light carbon nanotube sponge as an efficient electromagnetic shielding material in the GHz range

“…Moreover, the real permittivity presents low values along all the swept frequencies, which is noteworthy for a material composed of highly conducting CNT percolating networks. According to the effective medium theory, the permittivity of the material will have the contribution of both, air and CNTs, and hence, its value will be lower than that of a material exhibiting analogous conductivity values but being compact or non-porous [20]. The material lightness might enable its correlation with the dielectric properties found in aerogels and foams.…”

“…In some cases, these foams might have an additional advantage regarding EMI shielding by absorption-dissipation, as reported in MWCNT/polycaprolactone composites [19], in which the reflectivity was efficiently lowered using low CNT volume fractions when compared to solid composites having similar electrical conductivities. This reflection results from the mismatch of impedances at the propagating medium (air)/shield interface; the relative volume of air at the interface lowers the shield surface impedance, thus boosting the wave propagation within the material [6,20].…”

Strengthened electromagnetic absorption performance derived from synergistic effect of carbon nanotube hybrid with Co@C beads

“…The transformation of magnetic energy to electric energy indicates that, at high frequency, the EM absorption is mainly ascribed to the dielectric loss in the CNTs/Co@C hybrid. The negative permeability value and totally contrary variation trend of tangent loss have also been observed in other magnetic carbon hybrids such as CNTs/wax composite [49], Fe/Co/Ni nanoparticle-coated carbon nanofibers [50], graphene oxide/ CNT-Fe 3 O 4 composite [10], and porous carbon/Co hybrid [51]. To reveal the EM wave absorption performances of the CNTs/Co@C hybrid, the RL values were calculated according to Eqs.…”

Bio-Inspired Functional Materials Templated From Nature Materials

“…Finally the mixture was molded into disk specimens with 115mm and 6mm in diameter and thickness, respectively. In these molding processes, various pressures (12,16 and 20 MPa) were applied on the mixture for initial 20 min, and then solidification of the mixture was continued free from compression for 12 h. Secondary carbonization was carried out at the temperatures of 800 , 1200 and 1400 to yield nickel-loaded carbon matrix composites. The influence of carbonization temperature, molding pressure, nickel loading and the porous structure on the as-synthesized rice husk composites are discussed, which are summarized in Table 1.…”