Synergy Effects in Electromagnetic Properties of Phosphate Ceramics with Silicon Carbide Whiskers and Carbon Nanotubes

Abstract

Hybrid composite materials based on an aluminium phosphate matrix with silicon carbide whiskers and multi-walled carbon nanotubes were studied in a wide frequency range (20 Hz to 36 GHz). It was demonstrated, that the addition of the silicon carbide whiskers enhances the dielectric permittivity and conductivity. This was explained by the difference in tunnelling parameters. Hybrid ceramics with nanotubes and whiskers also exhibits substantially improved electromagnetic shielding properties. The hybrid ceramics with 10 wt. % silicon carbide whiskers and a 1 mm thick 1.5 wt. % carbon nanotube layer, show higher than 50% absorption of electromagnetic radiation.

Dielectric Properties of Hybrid Polyethylene Composites Containing Cobalt Nanoparticles and Carbon Nanotubes

“…The values of the complex dielectric permittivity of the composites with a high concentration of MWCNT (above percolation threshold) in microwaves is quite high (for example, for composites with 13.4 wt% MWCNT and 1.1 wt% Co ε′ ≈ ε″ ≈ 20 at 30 GHz, it corresponds to microwave absorption 50% of 1 mm thick plate in the waveguide [ 32 ]) ( Figure 2 ); therefore, these composites are suitable for electromagnetic applications. The electromagnetic properties of these composites in microwaves are comparable with the best properties of the composites published in literature [ 32 , 33 ]. The dielectric spectra of all investigated composites can be explained by Maxwell–Wagner polarization [ 34 ].…”

Electrical percolation and electromagnetic properties of polydimethylsiloxane composites filled with Ag nanoparticles of different sizes

“…[33] (please see Table 2) indicate that composites, depending from AgNPs size and concentration, are suitable for electromagnetic shielding applications. [34] T A B L E 1 Percolation threshold, fc, and corresponding critical exponents of the permittivity, g, and of the electrical conductivity, t, below and above the threshold Below room temperature, the electrical conductivity increases when the temperature decreases, and reaches a maximum around 180 K, which is close to the glass transition temperature of the pure PDMS matrix (150 K) ( Figure 4). [30] The behavior can be explained by a rapid shrinkage of the PDMS matrix upon cooling down to the glass transition temperature, and consequently by the increase in the tunneling conductivity between Ag particles during cooling.…”

“…[ 33 ] (please see Table 2) indicate that composites, depending from AgNPs size and concentration, are suitable for electromagnetic shielding applications. [ 34 ]…”

Phosphate Ceramics with Silver Nanoparticles for Electromagnetic Shielding Applications

“…Ceramics with conductive nanoparticles have thermally stable electromagnetic properties and excellent mechanical properties [ 3 , 4 ]. Therefore they are highly desirable for various electromagnetic shielding applications [ 5 , 6 ]. One most important parameter, which determines the electromagnetic properties of the composite insulator–conductor system, is the percolation threshold, the lowest concentration of fillers when the electrical conductivity is observed [ 7 ].…”