Composite films based on thermoplastic polyurethane (TPU) filled with birch-derived activated carbon (BAC) were investigated in a wide filler concentration range of 10–40 wt.%. The structural features of the BAC particles were examined by scanning electron microscopy, revealing a porous, irregular particle morphology. The TPU/BAC composites were further investigated using FTIR spectroscopy to assess chemical interactions, and it was shown that the filler mainly modifies the microenvironment of the urethane groups. The microwave properties of the composites were studied in the X-band (8–12 GHz). TPU/BAC films containing up to 30 wt.% BAC exhibit high microwave transparency, with the reflection coefficient ($S_{11}$) ranging from −14.5 to −15.7 dB and the transmission coefficient (${S}_{{21}}$) varying from −0.4 to −0.82 dB across the X-band. A pronounced change in electromagnetic response occurs at 40 wt.% BAC, where $S_{11}$ becomes less negative, reaching approximately −10 dB, and $S_{21}$ becomes more negative, reaching approximately −1.5 dB; together with increased absorption, this suggests the formation of a continuous conductive carbon network. The obtained results demonstrate that TPU/BAC composites combine environmental sustainability with tunable microwave behavior and can be considered promising candidates for flexible, lightweight, and radio-transparent components in high-frequency and microwave electronic applications.

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.

Viscose-derived carbon fibers (VDCFs) are lightweight and flexible textile materials with strong potential for electromagnetic interference (EMI) shielding; however, their performance is governed by surface chemistry. This study aims to tailor the functional properties of VDCFs via process-driven sulfurization. The fibers were treated with sulfur vapor at 400–800 °C under argon, followed by rapid quenching, enabling controlled sulfur incorporation (0.5–12 mmol g−1). Structural and chemical analyses (XRD, SEM–EDS, ATR–FTIR, and TPD–MS) revealed temperature-dependent sulfur incorporation and evolution of sulfur-containing surface functionalities. Sulfurization at 400–500 °C favored the formation of thermally labile sulfur species, tentatively assigned to mercapto-, sulfide-, and polysulfide-type groups, whereas higher treatment temperatures promoted more thermally stable sulfur-containing functionalities associated with the carbon framework. Two desorption regimes (120–250 °C and 250–500 °C) indicate the coexistence of weakly and strongly bound sulfur species. Importantly, sulfurization preserved fibrous morphology while increasing surface roughness and defect density, enhancing interfacial activity. The treatment temperature was identified as the key factor controlling sulfur loading and distribution, with sulfur content continuing to decrease above 600 °C, albeit at a reduced rate. Electromagnetic characterization in the X-band (8–12 GHz) showed a transition toward reflection-dominated EMI shielding, with reflectivity increasing from 87% for pristine fibers to 94–95% for sulfurized samples at 10 GHz, accompanied by corresponding decreases in transmission and absorption. These results demonstrate a clear processing–structure–property relationship and highlight sulfur-functionalized VDCFs as efficient textile components for EMI shielding.

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.

This work presents the synthesis of ferrite with the composition Ni0.5Zn0.5Fe2O4, its investigation by SEM, XRD, TGA, IR-Fourier methods, and the preparation of thin composite films using PVC as the base material and ferrite as a filler. It was found that the average crystal sizes are approximately 29.8 +/- 0.2 nm and 31.3 +/- 0.1 nm for Ni0.5Zn0.5Fe2O4 powder, respectively. The radio-absorbing properties of the resulting films in the X-band were investigated. Radiotransparent in the X-band composite material based on PVC/Ni0.5Zn0.5Fe2O4 ferrite with a weak dependence of the reflection value on the concentration of the filler (ferrite) was obtained.

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.

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).

Monoethanolamine, ethylenediamine, sulfolanylethylenediamine, and piperazine were used to aminate polyacrylonitrile (PAN) precursor-based carbon fibers (CFs), previously brominated using an aqueous KBr3 solution. HRTEM and SAED were confirmed the carbon nanostructures in PAN-CFs, comprising derivatives of turbostratic graphite layers. Successful amination was verified by FTIR-ATR, TGA, and TPD-MS. Thermal analysis in the 100-500 degrees C range revealed the decomposition of from 0.42 to 1.10 mmol g-1 amino groups in the aminated PAN-CFs/KBr3, with peak decomposition temperatures ranging from 230 to 310 degrees C. Amination significantly influenced the microwave properties of PAN-CFs/KBr3. Among the samples aminated with selected amines, the difference in average reflection loss S11 values reached 0.6 dB in the X-band and 0.9 dB in the Ka-band. For the average transmission loss S21 values, the corresponding differences were 1.1 dB and 1.5 dB, respectively.

Thin-film composites (TFCs) composed of poly(vinyl chloride) (PVC) and hydrogen peroxide-oxidized activated carbon (AC-H2O2) were fabricated via rapid thermal pressing, with filler loadings (x) ranging from 0.2 to 30 wt%. Characterization using SEM/EDX, FTIR, TGA, and Boehm titration confirmed the enhanced surface functionality of AC-H2O2. Microwave measurements in the Ka-band demonstrated radiotransparency at x <= 10 wt%, whereas higher x increased reflection (up to similar to 27%) and decreased transmission (down to similar to 48%). The electromagnetic response of the TFCs was tunable by adjusting x, with low x favoring transparency and high x providing effective shielding. These flexible TFCs show promising potential for scalable, lightweight applications in Ka-band electromagnetic inference shielding.

In this work, we investigated the microwave properties of ethylenediamine (En)- and sulfonylethylenediamine (SuEn)-aminated carbon fibers (CFs) derived from polyacrylonitrile (PAN CFs) within the X-band frequency range (8–12 GHz). Microwave measurements revealed that both En- and SuEn-aminated PAN CFs exhibited higher attenuation constants than the unmodified PAN CFs, indicating greater internal energy dissipation of electromagnetic waves. Furthermore, the results demonstrated that attenuation is anisotropic, depending on the alignment of the CF axis relative to the polarization of the electric field of the incident electromagnetic wave. This anisotropic attenuation, combined with the presumably anisotropic characteristic impedance of the modified CFs, led to significantly direction-dependent transmission and reflection coefficients. Compared to the SuEn-aminated PAN CFs, the En-aminated PAN CFs showed the most promising performance, exhibiting both enhanced microwave losses and reduced reflection relative to the unmodified PAN CFs. The combination of these properties makes En-aminated PAN CFs particularly suitable for electromagnetic shielding applications, where effective wave absorption and minimal reflection are critical. These findings underscore the potential of chemically functionalized PAN CFs as advanced materials for electromagnetic interference shielding in applications ranging from military stealth technology to commercial electronic protection systems.

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.

The article considers in detail the formation of liquid clathrates in ionic liquids (IL) -aromatic hydrocarbons (benzene, toluene, anisole, phenol) systems and shows that the size and nature of the movement of liquid clathrates formed by IL components and aromatic hydrocarbons are determined by the structural properties of aromatic hydrocarbon molecules. In addition, the paper presents the results of a systematic study of the influence of the dipole moment and the structure of aromatic hydrocarbons on the dynamics of ionic liquid (IL) of dimethylimidazolium chloride and considers the heterogeneity dynamics of aromatic hydrocarbons in the IL at T = 400 K.

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.