A comprehensive simulation of the carbon structures and surface properties during bromination was performed, taking into account potential carbon edge-related pathways. This objective was achieved through the implementation of quantum chemical DFT and ab initio methods. By integrating the data obtained from quantum chemical modeling with empirical data from gas-phase halogenation of activated carbons, the size of carbon clusters, which serve as the structural units of carbon materials, were estimated in the context of thermodynamic Gibbs free energy considerations. The estimated concentration of double C=C bonds involved in electrophilic addition reactions is 1.0 to 1.5 mmol/g, which corresponds to 0.2 to 0.3 mmol/g of carbon clusters, representing five of the six peripheral C=C bonds of the reacting carbon cluster. Assuming that half of the carbon atoms in carbon solids are surface carbon and that carbon solids should consist only of carbon clusters with no functional groups, the average carbon cluster size is estimated to be between 140 and 210 atoms. Considering the heterogeneity of the carbon matrix and the possible presence of up to 1 mmol/g of oxygen-containing surface groups, it is reasonable to assume that the average carbon cluster size is likely to be considerably smaller. These estimates confirm the suitability of the proposed quantum chemical approaches for analyzing the reactivity of the carbon surface in activated carbon solids during bromination.

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.

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.

In this study, glass microspheres (GMs) of varying sizes, both pure and decorated with nano-sized bimetallic Ni (80)Fe(20) particles, were incorporated into epoxy-based composites filled with 3 wt% graphite nanoparticles (GNPs) to create 2D and 3D structures. The electromagnetic interference (EMI) shielding properties were analyzed in the Ka-band (25-36 GHz). The addition of GMs altered the frequency dependence of shielding efficiency (SET) and shifted the balance between shielding by reflection (SER) and absorption (SEA). In GNPs-only composites, SEA was much smaller than SER, whereas in all GMs-containing materials, SEA significantly exceeded SER. At higher frequencies, the absorption-to-reflection loss ratio increased, reaching 4 at 36 GHz. For 2D GM structures with a thickness of 0.6-0.8 mm, absorption exhibited a sharp frequency dependence at lower frequencies. In contrast, 3D GM structures with a thickness greater than 2.5 mm maintained a frequency-independent absorption with a value of 0.95. These results highlight that incorporating GMs into epoxy/3% GNP composites enhances absorption mechanisms in their interaction with electromagnetic waves.

The composites based on ternary oxide Al2O3-SiO2-TiO2 (AST1), decorated with nanoparticles of nickel, cobalt, and iron oxides, were prepared by the solvate-stimulation method from nitrate and formate solutions with subsequent homogenization, calcination, and hydrogen reduction. The study of the CO2 conversion over the formed bimetallic particles Ni(80)Fe(20) and Co(93)Fe(7) (wt.%) deposited on AST1 was carried out under gas chromatographic control. The TPD MS technology was used to evaluate the desorption of species involved in the mechanism of methane formation. Textural and structural characteristics of as-prepared and post-reacted composites were examined using low-temperature nitrogen adsorption, CO2 and H-2 chemisorption, SEM-EDX, XPS and XRD methods.

Petrodarco (R) 4X10 nanoporous activated carbon (NAC) was thermolytically fluorinated at 400-800 degrees C using pentafluoroethane and 1,1,1,2-tetrafluoroethane gases. The incorporation of fluorine-containing functional groups into the carbon surface was quantitatively analyzed, and the evolution of the carbon surface after fluorination and fluoroalkylation was characterized using F-19 ss-NMR and XPS spectroscopy. The process achieved a fluorine enrichment of about 3 mmol g(-1) (3.9 wt%), while partially preserving the microporous structure of the initial NAC, as confirmed by nitrogen adsorption analysis. Thermogravimetry, FTIR ATR, TPD MS, and XPS showed that oxygen-containing groups of the carbon surface are replaced by more thermostable fluorine-containing groups at treatment temperatures above 600 degrees C. The proposed fluorination process allows control of the type of fluorine groups, including freon residues, as well as CF3 and CF2 groups, by adjusting the treatment temperature. Fluoroalkyl groups are grafted at 400-500 degrees C, while semi-ionic fluorine groups are added above 600 degrees C. Improved surface chemistry, with potential for special applications, was observed on the selectively fluorinated NAC surface. Furthermore, fluorination at 600-800 degrees C effectively replaced surface hydroxyl groups with fluorine-containing groups, optimizing the NAC surface for the passage of high-temperature gas-solid phase reactions by improving the surface thermostability at temperatures below 400 degrees C. This study presents a scalable method for converting highly fluorinated gases into functionalized NAC solids, highlighting its potential for chemical and industrial applications.

Petrodarco (R) 4X10 nanoporous activated carbon was halogenated in the gas phase using 1,1,1,2-tetrafluoroethane, dichlorodifluoromethane and 1,2-dibromotetrafluoroethane, followed by sulfonation of the carbon surface to create specific active sites. The concentration of halogen groups introduced into the activated carbon at high temperatures was measured, and these groups were transformed into functional groups favorable for substitution or catalytic applications. Catalytic studies confirmed that selected halogen groups could be efficiently substituted with highly catalytic active SO3H groups, making the material particularly effective for the catalytic dehydration of 2-propanol in the gas-solid phase, with excellent efficiency and stability at temperatures below 200 degrees C. Based on these findings, we have developed a promising process for converting highly halogenated freons into effective carbon-based catalysts for dehydration reactions or, potentially, as acidic electrodes in fuel cells.

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.

A series of samples of carbon microspheres (CMS) have been synthesized by the hydrothermal method. It was found that varying the synthesis temperature between 200 and 300 degrees C and introducing iron salts into the reaction mixture had no significant effect on the structural or compositional properties of the CMS. The resulting CMS consisted of 69.5-75 wt% carbon and 25-30.5 wt% oxygen. Heat treatment was shown to decompose surface functional groups and promote "aromatization" of the carbon matrix. In addition, the synthesized CMS, when incorporated into an epoxy matrix, demonstrated effective absorption, and shielding of electromagnetic waves.

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.

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.

According to the proposed pyrolytic method, granular activated carbon (AC) Norit 830 W was functionalized by thermal treatment of AC in hydrofluorocarbon (HFC) gases, pentafluoroethane and 1,1,1,2-tetrafluoroethane, at 400-800 degrees C. This method does not require activation by plasma and photons. Chemical and elemental analysis showed that the pyrolytic treatment provides a loading of 2.95 mmol (5.6 wt%) of fluorine per gram of AC. Nitrogen adsorption measurements indicated that the microporous structure contracted when AC was treated with HFC at temperatures above 400 degrees C. Thermogravimetry, Fourier transform infrared spectroscopy (FTIR) with attenuated total reflectance (ATR), and X-ray photoelectron spectroscopy (XPS) demonstrated the evolution of oxygen-containing and fluorine-containing groups to more thermostable groups with treatment temperature. The fluorine-containing groups grafted at high temperature, above 600 degrees C exhibited the highest thermal stability up to 1250 degrees C in dry argon. From the data of XPS and solid-state F-19 nuclear magnetic resonance spectroscopy data, the grafted fluorine exists in several types of grafted F-containing groups, the HFC residues. By changing the thermal regime of fluorination, the composition of fluorine-containing groups on a carbon surface can be regulated. Isolated fluoroalkyl groups can be grafted at temperatures of 400-500 degrees C, while at 600 degrees C and above, the semi-ionic fluorine groups increase significantly. The hydrophobized surface demonstrated the ability to effectively decompose H2O2 in methanol solutions.