Thin-film composites (TFCs) based on poly(vinyl chloride) (PVC) and multi-walled carbon nanotubes (MWCNTs) were fabricated by hot pressing to produce a compositional series of $(\text { PVC })_{100-x} /(\text { MWCNTs })_{x}$, where $x=0.2-10$ wt %. The morphology and elemental composition of the MWCNTs were examined by SEM and EDX spectroscopy, while TGA in air suggested the presence of carbon domains with different structural ordering and revealed characteristic oxidation kinetics. Microwave characterization in the X-band frequency range (8–12 GHz) showed that the TFCs remained weakly interacting with microwave radiation at MWCNT loadings up to 5 wt%, exhibiting only weak attenuation of transmitted radiation. With a further increase in MWCNT content, a pronounced nonlinear variation in reflection and transmission coefficients was observed, culminating in a threshold-like transition near 10 wt.% filler. This behavior is consistent with the formation of a continuous conductive network within the PVC matrix—i.e., an electrodynamic percolation-type transition—which drastically modifies the dielectric and electromagnetic response of the TFCs. The identified transition thus indicates a critical composition range for achieving efficient electromagnetic shielding in PVC/MWCNT TFCs.

Activated carbon (AC) prepared by carbonization of pit stones was used as received and after surface oxidation with hydrogen peroxide (H2O2) and nitric acid (HNO3) as carbon fillers for poly(vinyl chloride) (PVC) composite films. Thermal analysis confirmed the formation of carboxyl, lactone, anhydride, and phenolic surface groups in the oxidized samples. Morphological changes induced by oxidation were examined by scanning electron microscopy. Microanalysis showed that treatment with H2O2 increased the oxygen content to 7.5 at. %, while HNO3 oxidation increased it to 11.9 at.%. X-band microwave measurements were performed to evaluate the influence of AC–H2O2 and AC–HNO3 fillers on the electromagnetic response of PVC composites. The reflection coefficient $S_{11}$ became less negative with increasing filler concentration, indicating an increase in reflected power that was more pronounced for the oxidized fillers. The most negative $S_{11}$ value for PVC/AC was −9.4 dB, whereas for PVC/AC–H2O2 and AC–HNO3 it was −11.8 dB at the highest filler loading. Surface oxidation had only a minor influence on transmission and absorption in the X-band.

Thin-film poly(vinyl chloride) (PVC) composites containing 0.2-30 wt% carbon nanoparticles (CNPs) were prepared by hot pressing. The morphology and elemental composition of the CNPs were analyzed by SEM and EDX, and their thermal stability was evaluated under inert and oxidative atmospheres. FTIR spectroscopy confirmed the absence of any chemical interaction between PVC and CNPs. Ka-band microwave measurements revealed a composition-dependent electromagnetic response. Composites with <= 5 wt% CNPs remained largely transparent to microwaves, whereas higher filler loadings increased reflectivity. The S-21 and S-11 parameters varied from -0.7 to -2.4 dB and -15.0 to -7.2 dB, respectively, with a transition observed at 10-20 wt% CNPs.

Poly(vinyl chloride) (PVC) composite thin films containing $20 \mathrm{wt}. \%$ yttrium iron garnet (YIG) and $10 \mathrm{wt}. \%$ carbon filler, namely, activated carbon (AC), multi-walled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs), carbon nanoparticles (CNPs), or carbon black (CB), were fabricated by hot pressing to evaluate the influence of carbon filler morphology on their microwave behavior in the X-band. SEM was used to characterize the morphology of the carbon fillers. FTIR analysis suggested polymer-filler interactions manifested by shifts in characteristic PVC bands. S-parameter measurements revealed significant differences in microwave response depending on filler type. MWCNT-filled composites exhibited the strongest attenuation of the transmitted signal and the highest absorption (average $26.26 \%$), while CNP-filled films demonstrated a weak resonance-like feature in S11 at 8.9 GHz. Composites with AC, GNPs, and CB showed minimal changes in transmission and reflection, indicating limited interaction with the incident electromagnetic field. These findings indicate that filler morphology and dimensionality strongly influence the balance between reflection, transmission, and absorption in PVC/YIG/carbon composites. While AC-, GNP-, and CB-filled films remain largely transparent in the Xband, the incorporation of MWCNTs or CNPs enhances attenuation and absorption characteristics.

Films of composite materials based on thermoplastic polyurethane (TPU) with birch activated carbon (TPU/BAC) were obtained with a filler concentration from 0.5 to 40% by mass. The morphology of BAC was studied by the SEM method. The films' average thickness varied from 0.22 to 1.47 mm. The microwave studies indicate that the investigated TPU/BAC composites are generally transparent in the X-band. They have small transmission losses (less than 0.8 dB for 0.5-30 wt.% concentration and 1.1-1.5 dB for 40 wt.%) and reflection coefficient remained below -10 dB for all investigated in the whole frequency range.

Poly(vinyl chloride) (PVC) and carbon black (CB) powders were hot-pressed to form (PVC)(100-x)/(CB)(x) thin-film composites (TFCs), where x = 0.2-30 wt%. SEM-EDX showed spherical CB morphology and 0.61 wt% oxygen content. TGA and TPD MS studies of the CB showed high thermal stability and oxidation resistance and presented surface carbon-oxygen groups; FTIR indicated physical interactions within the TFCs. TFCs with x < 10 wt% remained Ka-band transparent, but increasing x enabled tuning of microwave reflection (similar to 10 dB), transmission (<5 dB), and absorption (<1.8 dB). These results highlight that (PVC)(100-x)/(CB)(x) TFCs are lightweight, tunable, and cost-effective materials for advanced electronics.

Polycyanurates (PCNs), offer a unique outstanding combination of physical properties that makes them suitable for use in aerospace and microelectronics, e.g. as composite matrices for strakes, fins, nose radomes, heat shields, printed circuit boards, and as encapsulants and adhesives. The attractive features of PCNs are their low dielectric losses (≈ 2.6–3.2), dimensional stability at molten solder temperatures (220–270 °C), high purity, inherent flame-retardancy (giving the potential to eliminate brominated flame retardants), low moisture absorption, and good adhesion to miscellaneous substrates.The microwave characteristics of thermostable nanocomposites based on polycyanurate, derived from industrial oligomer of dicyanate ester of bisphenol A, "Primaset BA-230S 75") and the addition of small concentrations of multiwalled carbon nanotubes (MWCNTs) up to 0.1 wt.% were investigated in the X-band using standard reflectometry methods. It was found that such concentrations of filler have a weak but ambiguous effect on the microwave characteristics of the composites. These composites, as well as the base material, are sufficiently transparent for microwave radiation. As a result, the properties of the materials in the X-band are weakly absorbing and weakly reflecting. A composite with 0.02 wt.% MWCNTs is more promising compared to the base in use as a shelter for antennas or electromagnetic radiation sources from external factors.

Carbon fibers derived from carbonized and activated polyacrylonitrile (CFPAN) were sequentially brominated and subsequently functionalized with selected primary and secondary amines to engineer a directional electromagnetic (EM) response. Besides bromine incorporation, bromination introduced oxygen-containing surface groups (e.g., carboxyl, lactone), enabling nucleophilic substitution by amines. Surface characterization (SEM-EDS, FTIR ATR) confirmed successful amine grafting, while thermal analysis (TGA, TPD MS) revealed increased weight loss in the 150–450 °C range due to the decomposition of covalently bonded nitrogen- and oxygen-containing moieties, evidencing strong surface functionalization. Microwave characterization in the X-band (8.2–12.4 GHz) demonstrated that functionalization strongly influences the EM response of CFPAN fibers. The measured reflection coefficient varied from −1.0 to −2.5 dB for sulfonylethylenediamine (SuEn)-functionalized fibers and from −2.0 to −4.0 dB for ethylenediamine (En)-treated ones, depending on frequency and fiber orientation. The frequency-averaged absorption coefficient of pure CFPAN amounted to 32–41%, with absorption maxima and minima corresponding to orientations differing by 90°. SuEn modification decreased absorption to 21–35%, while En functionalization enhanced it to 32–51%. Pure CFPAN exhibited the lowest absorption anisotropy (factor 1.28), whereas piperazine- and En-modified samples showed the highest anisotropy (1.57 and 1.59, respectively). Across all compositions, the attenuation constant remained within 1.5–4.5 mm−1. The observed anisotropic behavior is governed primarily by orientation-dependent variations in characteristic impedance and, to a lesser extent, by anisotropic attenuation constants. Such tunable anisotropy is particularly advantageous for EM shielding textiles, where fiber alignment can be tailored to enhance interaction with polarized fields. Among the tested amines, En-functionalized CFPAN exhibited the highest nitrogen content (up to 10.1 at%) and the most significant enhancement in microwave absorption, positioning it as a promising candidate for advanced orientation-sensitive shielding applications.

Poly(vinyl chloride) (PVC) and carbon nanoparticles (CNPs) powders were hot-pressed into (PVC)100–x/(CNPs)x thin-film composites (TFCs), where x = 0.2–30 wt%. The morphology and composition of CNPs were investigated by SEM and EDX. Thermal stability and oxidation resistance of the CNPs as a filler were determined by thermolysis in argon, vacuum pyrolysis, and combustion in air, correspondingly. FTIR studies revealed possible interactions in the TFCs. The resulting composite at low filler concentrations (up to 5%) by characteristics is close to composites radio-transparent in the X-band and it does not have good reflective properties (at low filler concentrations). At high filler concentrations, the ability of the composite to reflect the electromagnetic waves increases dramatically, the difference in reflection losses for samples with a minimum (0.2%) and maximum (30%) concentration of CNPs is quite significant and amounts to 13.1 dB. By increasing the concentration of the filler, it is possible to precisely change the attenuation of microwave transmission and reflection over a fairly wide range (–21.0 dB to –7.9 dB for reflection and –0.2 dB to –3.9 dB for transmission).

This work presents the obtaining of polyvinyl chloride (PVC)/yttrium iron garnet (YIG) composites and investigating their microwave properties. Composites in the form of thin flexible films with a thickness of 0.25 cm were investigated by the SEM, TGA, PXRD, and FTIR methods. The magnitudes of electromagnetic wave transmission are within - (0.3-0.5) dB for all the range of filler concentrations whereas the reflection coefficient varies within approximate to - (15.6-13.0) dB. Such radio-transparent materials can be used as a component of enclosures that protects a radar and avionics equipment antennas from weather and physical damage while allowing unrestricted microwave energy penetration.

Brominated polyacrylonitrile-based carbon fibers (PAN CFs) were obtained by bromination with low-temperature bromine plasma and liquid bromine. The brominated PAN CFs with different bromine concentrations demonstrated different thermal stability and carbon surface oxidation. Besides, the bromination changes the microwave properties of PAN CFs in the X and Ka bands. The magnitude of losses S-21 and the voltage standing wave ratio (VSWR) showed complex dependencies on the bromine concentration and the bromination method used. Typically, adding more bromine degrades the shielding properties but improves the VSWR in the Ka-band.

Activated Carbon (AC) prepared by the carbonization of pit stones was used as is and was subjected to surface oxidation with nitric acid (HNO 3 ) to be used as carbon filler for polyvinyl chloride (PVC) in order to prepare PVC-based composite films. Thermal analysis of AC and AC-HNO 3 revealed the presence of carboxyl, lactone, anhydride, and phenolic groups on the surface of the oxidized AC. The morphological changes for oxidized ACs were imaged by scanning electron microscopy. Microanalysis data showed that treatment with HNO 3 increased the oxygen content by up to 15 wt%. In the study, we used X-band microwave frequency analysis to investigate the effect of AC-HNO 3 in PVC composite films on the electromagnetic properties. The reflection loss S 11 of electromagnetic waves increases with the AC-HNO 3 content in PVC-based composites according to a linear law. High concentrations of the AC filler weaken the radio-masking properties of the investigated PVC/AC-HNO 3 composites while improving the EM wave absorption capability.

Here, we report how the oxidation of carbon fibers (CFs) with H2O2 and HNO3 affects the CFs' microwave properties. The CFs were characterized by SEM and TEM, and oxygen-containing surface groups were quantified by thermal analysis methods. Treatment with H2O2 and HNO3 solutions increased the oxygen content to about 6 at% and up to 10 at%, respectively, which decreased the reflection loss and increased the transmission loss at 25.86-37.5 GHz. The microwave properties showed pronounced correlations with the concentration of HNO3 and not with H2O2, indicating that the HNO3 oxidant is more promising for microwave loss tuning.

Carbon fibers (CFs) were prepared from viscose and oxidized with HNO 3 solutions, which is an effective method for the carbon surface modification. The thermal stability of the oxidized CFs was investigated by thermal analysis methods. According to the results of thermogravimetric analysis and thermoprogrammed desorption mass spectrometry, the oxidized CFs contain carboxyl, lactone, anhydride, and phenolic surface groups. The relief of the oxidized CFs was examined by SEM. According to the SEM/EDX analysis, the oxygen content increases up to five times after oxidation. The used oxidation of CFs has a significant effect on their microwave properties in the K a -band. Oxidation causes a 4.3 dB decrease in electromagnetic wave reflection and an 18.3 dB increase in electromagnetic wave transmission. The studies show a correlation between the concentration of HNO 3 and the reflection and transmission losses. This objective correlation suggests the possibility of programming the reflection and transmission loss values when modifying the microwave properties of carbon materials or carbon composites.

We present the results of a systematic study of the influence of isomerism of selected primary and secondary alcohols on their processes of solvation in dimethylimidazolium (dmim+) chloride ionic liquids. The properties of this system are investigated near the melting temperature by means of the molecular dynamics method. The study of single particle tracking (SPT) trajectories plays a significant role in the present analysis of the features of the microscopic movement of molecules of the dissolved substance in the solution. We demonstrate that the isomerism of alcohol molecules in case of isobutanol and isopentanol leads to the increase of their self-diffusion coefficients due to the growth of the IL’s local structure near the solute as we move from the alcohol to its isomer. The motion of butanol/isobutanol and pentanol/isopentanol alcohols molecules in this process is determined both by the mass, and the hydrophobic properties of the solute. Conversely, we demonstrate that the motion of systems with propanol/isopropanol are determined by the structure of the solute.

This work presents the synthesis of ferrite with the composition Ni0.5Zn0.5Fe2O4, its investigation by the methods of SEM, TG/DTA, PXRD, FTIR and the preparation of thin composite films using polyvinylchloride (PVC) as the base material and ferrite as fillers. Nickel-zinc ferrite nanopowder with a cubic spinel structure was synthesized by glycine-assisted sol-gel route. From TG/DTA experiment it was found that single phase product was formed already after combustion of dried glycine-nitrate gel. According to X-Ray diffraction and SEM it was determined that ferrospinel after annealing at 650 degrees C during 5 h has a porous structure, homogeneous composition. The crystallite size was approximately 29-31 nm. On the FTIR spectra of oxide-polymer composites showed the presence of a characteristic band of PVC, ferrite and plasticizer. The radio-absorbing properties of the resulting films in the Ka-band were investigated. The microwave studies indicate that radio-transparent composite material was obtained on the basis of PVC/Ni0.5Zn0.5Fe2O4, with a weak dependence of the reflection value on the concentration of the ferrite filler.

In this work, an investigation of the optical properties for the nanoribbons of nickel on chromium nanofilm and the set of chromium nanofilms is proposed in terms of Mueller ellipsometry. It was observed that if a nickel nanoribbon with a thickness of 250 nm is produced at 250 ^∘ C on a chromium film with a thickness of 250 nm, then the experimentally observed state (internal structure) of the nickel nanoribbons is different for the nanosystems, such as nickel nanoribbon-chromium nanofilm and nickel nanoribbon-glass substrate. Despite the opacity of the nickel nanoribbons with the given thicknesses for the used laser light source, the optical properties of the outer surface are thus determined by the interface between the nanoribbon and the type of material of the next layer. For the investigated multilayer nanosystem of the nickel nanoribbons on chromium nanofilm, the global extremum (in the sense of the quadratic dependence indicated above) of the value of the ellipsometric angle is 74.5^∘ for the incident light beam that coincides with the system of chromium nanofilm on glass substrate. At the higher temperature than the Néel temperature for a macroscopic bulk of chromium, the observed abrupt change in the ellipsometric parameters of the nickel nanoribbons on the chromium film is the pretendant to be discussed as the confirmation of the phase transition in the ordering of the internal structure of system with the ferromagnetic–antiferromagnetic interface.

This work presents the investigation of thermostable thin composite films based on Cyanate Ester Resin (CER) network as the base material and the Multi-Walled Carbon Nanotubes (MWCNTs) as a filler. During the study of the thermal stability of the CER/MWCNTs nanocomposites synthesized, it was found that the presence of carbon nanotubes dispersed in the polymer matrix in an amount of 0.01 and 0.10 wt.% slightly increased the resistance of these nanocomposites to thermal oxidative degradation (in air) compared to the pure CER network. This is due to a certain contribution of MWCNTs, which have very high thermal stability. The radio-absorbing properties of the resulting films of the CER/MWCNTs nanocomposites in the X-band were investigated. It has been shown that when adding nanotubes, the attenuation of the electromagnetic signal increases and there is a slight dispersion of the increase in the attenuation of the signal in the direction of increasing the frequency of the electromagnetic signal.

Polyacrylonitrile-based carbon fibers (PAN CFs) were chlorinated with carbon tetrachloride vapor at 300 °C, 450 °C, and 600 °C. The surface chlorine concentration in the chlorinated PAN CFs increased from 1.82 to 3.73 mmol g –1 with increasing temperature. The chlorinated PAN CFs were characterized by SEM, TEM, and FTIR-ATR methods. The surface morphology is preserved after chlorination at the SEM characterization level; the HRTEM shows the formation of nanoscale surface carbon structures. FTIR-ATR showed the oxidation of the carbon surface and the formation of carbon–oxygen groups. From the TGA and TPD MS analysis of HCl vacuum thermodesorption below 800 °C, the most thermally stable CCl 3 groups were proposed as the source of HCl gas, and their highest concentration corresponds to the highest chlorination temperature. From the results of electromagnetic shielding studies, higher chlorination temperature increases the attenuation parameter S 21 and reflection coefficient S 11 measured for a layer of the chlorinated PAN ACFs over the X-band and Ka-band frequencies. Both the S 21 and S 11 parameters have nearly constant values over a wide range of frequencies. This behavior can be used to construct the latest generation of microwave attenuators with attenuation controlled by chlorination, and they are also promising microwave absorbers for the protection of biological objects.