Heat-treated nano-structured shungite rocks and electrophysical properties associated

Shungite rocks of two different types were treated at $\sim$ 1400$^\circ$C and a set of nanomaterials have been obtained. Among the different materials obtained were: carbon hollow fibers; spherical or ellipsoid particles; silicon carbide amorphous; crystalline nanofibers and nanoparticles having different morphologies; iron and iron silicide nanoparticles encapsulated into carbon shells. Measurements were performed for shielding effectiveness (SE) and the electrical conductivity ($\sigma$) of untreated and heat-treated shungite rocks. The shungite rock with dominated hyperfullerene carbon is remarkable for a two-fold increase in the $\sigma$ and a 10 dB increase in SE with a slight decrease of the carbon content by 1.5% in relation to the untreated sample. In contrast, the treated shungite rock with high SiC nanofiber content is characterized by a halving of the $\sigma$ and a 10 dB decrease in SE with a decrease of the carbon content by 6% relative to the original sample.