Abstract
Polymer composites with electrically conductive inclusions are intensively developed for microwave shielding applications, where lightweight and elastic coatings are necessary. In this paper, dielectric properties of hybrid polyethylene composites containing cobalt nanoparticles and multi-wall carbon nanotubes (MWCNT) were investigated in the wide frequency range of 20–40 GHz for electromagnetic shielding applications. The percolation threshold in the hybrid system is close to 6.95 wt% MWCNT and 0.56 Co wt%. Cobalt nanoparticles (up to highest investigated concentration 4.8 wt%) had no impact on the percolation threshold, and for the fixed total concentration of fillers, the complex dielectric permittivity is higher for composites with bigger MWCNT concentrations. Moreover, the microwave complex dielectric permittivity of composites with high concentration of fillers is quite high (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 thickness plate); therefore, these composites are suitable for electromagnetic shielding applications.
Highlights
Fast progress of telecommunications and electronics leads to the broad use of electromagnetic waves in various areas
The microwave complex dielectric permittivity of composites with high concentration of fillers is quite high; these composites are suitable for electromagnetic shielding applications
The study of the electrophysical properties of the composites showed that the uniform distribution of multi-wall carbon nanotubes (MWCNT) in polyethylene provides high values of conductivity, which correlate with high values of the complex dielectric permittivity [30]
Summary
Fast progress of telecommunications and electronics leads to the broad use of electromagnetic waves in various areas. The issues of electromagnetic interference become principal since various apparatuses work in the same or neighbor frequency ranges and are due to the generation of electromagnetic waves by some natural phenomena (for example lightning); the power of electromagnetic waves increases with the number of apparatuses working in the same place and by the fast growing industry of telecommunications, where higher frequencies and higher power are needed for the transference of a larger quantity of information [1,2]. The electromagnetic interference can cause damages to electronic devices and can be harmful for human health [3]. The electromagnetic waves can be used for unsanctioned information collecting or tracking of peoples or vehicles. Traditional electromagnetic shielding materials involve highly electrically conductive metals such as Al, Cu [4]. The main drawbacks of metals for such applications are the high density, easy corrosion, poor flexibility and big reflected part of electromagnetic radiation. Coatings based on polymer composites filled with various electrically conductive inclusions are lightweight, easy processable and chemically inert [5]
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