Synergistic effect causes significant decreasing of the percolation threshold in the ternary polymer composites filled with carbon nanotubes (CNT) and graphite nanoplatelets (GNP) in comparison with binary ones. Enhancement of the percolation threshold strongly depends only on the relative aspect ratios of the filler particles due to the formation of the bridges between puddles of the different filler components. Conditions of both appearance and fading away of the synergistic effect are investigated depending on the relative morphology of CNT or GNP components of the filler. Different lateral sizes, aspect ratios, and volume concentrations of both CNT and GNP in the selected ternary composites were considered. Conditions of the effective substitution of GNP with CNT and vice versa in equal volume concentrations without enlarging of the percolation threshold were established. The results are obtained numerically using the Monte Carlo simulation of the percolation threshold of the different ternary composites.

Polyethylene (PE) based composites with segregated carbon nanotubes (CNTs) network was successfully prepared by hot compressing of a mechanical mixture of PE and CNT powders. Through comparison with a composite comprising randomly distributed carbon nanotubes of the same concentration, we prove that namely the segregated CNT network is responsible for the excellent electrical properties, i.e., 10⁻¹ S/m at 0.5–1% and 10 S/m at 6–12% of CNT. The investigation of the complex impedance in the frequency range 1 kHz–2 MHz shows that the sign of real part of the dielectric permittivity ${\epsilon }_r^{\prime }$ changes from positive to negative in electrically percolated composites indicating metal-like behavior of CNT segregated network. The obtained negative permittivity and AC conductivity behavior versus frequency for high CNT content (3–12%) are described by the Drude model. At the same time, in contrast to reflective metals, high electromagnetic shielding efficiency of fabricated PE composites in the frequency range 40–60 GHz, i.e., close to 100% at 1 mm thick sample, was due to absorption coursed by multiple reflection on every PE-CNT segregated network interface followed by electromagnetic radiation absorbed in each isolated PE granule surrounded by conductive CNT shells.

Thermo-exfoliated graphite (TEG)/CuO/Cu₂(OH)₃NO₃:(Co²⁺/Fe³⁺) composites were prepared using a wet impregnation method and subsequent thermal treatment. The physicochemical characterization of the composites was carried out by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Ar temperature-desorption techniques. The catalytic efficiency toward CO conversion to CO₂ was examined under atmospheric pressure. Characterization of species adsorbed over the composites taken after the activity tests were performed by means of temperature programmed desorption massspectrometry (TPD MS). (TEG)/CuO/Cu₂(OH)₃NO₃:(Co²⁺/Fe³⁺) composites show superior performance results if lower temperatures and extra treatment with H₂SO₄ or HNO₃ are used at the preparation stages. The catalytic properties enhancements can be related to the Cu₂(OH)₃NO₃ phase providing reaction centers for the CO conversion. It has been found that prevalence of low-temperature states of desorbed CO₂ over high-temperature ones in the TPD MS spectra is characteristic of the most active composite catalysts.

Conductive polymer composites are widely used for electromagnetic radiation protection. Several strategies can be employed for creating shield materials with enhanced efficiency: the use of a hybrid filler that contains nanoparticles of different types, specific structural design, and methods for decreasing the percolation threshold. We present the study of segregated polymer composites (SPCs) with ultrahigh molecular weight polyethylene (UHMWPE) matrix and hybrid fillers of NiFe-decorated graphite nanoparticles (GNPs). The microstructure, electrical percolation behavior, and electromagnetic shielding efficiency of the developed SPCs as a function of conductive filler content are determined. The combination of the advantages of the segregated structure with a synergistic effect of a hybrid filler in (GNP-NiFe)/UHMWPE allows decreasing the percolation threshold to 0.45 vol. %. The enhanced shielding efficiency of 37 dB in the frequency range of 26–37.5 GHz is achieved at the filler content of 3.4 vol. % in 1 mm thick composite samples. The dominant shielding characteristic of absorption renders hybrid composites with a segregated structure promising materials.