Creating Self-Regulating Electric Heaters and Materials for Protection Against Electromagnetic Radiation

The article presents the results of studies of elastomers modified by multilayer carbon nanotubes (MCNTs). An elastomer, polydimethylsiloxane, served as the polymer base while MCNTs synthesized on Co–Mo/Al2O3–MgO and Fe–Co/2.1Al2O3 catalysts were used as a filler. The structural analysis of particle sizes of MCNTs was carried out. It showed that MCNTs synthesized on Co–Mo/Al2O3–MgO catalysts have the outer diameter of 25–35 nm and the inner diameter of 10–15 nm, while MCNTs synthesized on Fe–Co/2.1Al2O3 catalysts have the outer diameter of 5–15 nm and the inner diameter of 5–7 nm. The electrical conductivity of the heating elements samples was studied. The maximum electrical conductivity (1.66×10–1 Sm/cm) was observed for a composite based on polydimethylsiloxane modified with 7 wt % MCNTs (synthesized on the Co–Mo/Al2O3–MgO catalyst) while the sample modified with MCNTs (synthesized on the Fe–Co/2.1Al2O3 catalyst) had the maximum heat release rate coupled with evenly distributed heat flow pattern. The maximum heating temperature of 102°C corresponded to a constant voltage of 18–24 V. The studies of electromagnetic radiation interaction with the samples were executed. In those studies, heating element samples made of MCNTs (synthesized on the Fe–Co/2.1Al2O3 catalyst) demonstrated wide-band attenuation of impinging radiation (up to 20%) while heating element samples made of MCNTs (synthesized on the Co–Mo/Al2O3–MgO catalyst) showed the ability of electromagnetic shielding in the range of 26 to 40 GHz at the level of 15%.