Carbon Nanostructures Research Articles

Evolution of carbon nanostructures during coal graphitization: Insights from X-ray diffraction and high-resolution transmission electron microscopy

The evolution of carbon nanostructures during coal graphitization was investigated. The X-ray diffraction (XRD) results showed that amorphous and microcrystalline carbon coexist in anthracite and meta-anthracite, and the latter has a higher proportion of microcrystalline carbon; additionally, semi-graphite and coal-based graphite are mostly composed of crystalline carbon. Coal graphitization starts in anthracite, accompanied by an increase in crystallite size and a decrease in interplanar spacing nonlinearly, especially in semi-graphite, and a large ordered structure is formed in coal-based graphite. The high-resolution transmission electron microscopy (HRTEM) results intuitively reveal the graphitization process by false-colored microphotography, and both the XRD and HRTEM results indicate similar evolution paths. Four types of carbon nanostructures, namely, amorphous, turbostratic, concentric and graphitic-like structures, are identified according to their morphology. Aromatic fringes are arranged randomly in the amorphous structure and are composed of amorphous carbon; local ordering occurs in the turbostratic structure and is commonly observed in anthracite and meta-anthracite. In addition, a concentric structure with hollow pores and parallel annular aromatic fringes was observed, indicating multiple preferred orientations, and the graphitic-like structure was composed of parallel aromatic fringes. Micropores provide the necessary adjustment space for the ordered conversion of carbon nanostructures, and the flattening and merging of micropores may contribute to the enhancement of graphitization.

Ceramic matrix composite based on silicon carbide and nanostructured nitrogen-doped carbon for supercapacitor electrodes

The results of studies on the production of a porous ceramic-matrix composite material C–N/SiC from silicon carbide and nitrogen-doped nanostructured carbon for subsequent use as supercapacitor electrodes are presented. The material is formed by pressing silicon carbide micropowder (1 µm) and impregnating with a solution of carbamide (nitrogen source) in phenol-formaldehyde varnish (carbon source), curing and pyrolysis in a nitrogen atmosphere. The maximum concentration of carbamide was obtained in the solution (16 wt.%) at 50 ºС with a viscosity of 134.3 mPa⋅s. Thermogravimetric analysis in nitrogen of the cured solution revealed multistage decomposition with a residual mass of C–N of 48 % at 1000 ºС. Studies of the elemental composition showed a nitrogen content of 1.4 wt.% in C–N/SiC composite (up to 7 % of C–N active mass). In the composite structure, the C–N carbon-nitrogen layer (up to 12 wt.%) distributed inside the matrix pores and covering the SiC grains is X-ray amorphous has a complex nanoscale relief with an average pore size of 1.0–1.5 nm. According to electrochemical studies, the specific capacitance of the C–N/SiC material and the C–N active layer is 16.84 and 153.2 F/g respectively, and the equivalent resistance of the test supercapacitor cell with C–N/SiC electrodes is 0.567 Ohm for samples with maximum doping. The electrodes operate according to the sorption-desorption mechanism of charge accumulation and release, which is typical for a classic supercapacitor based on a double electric layer without the presence of redox reactions on the electrodes. The influence of technological regimes of pyrolysis on the electrophysical parameters of the cell is revealed: lower values of the pyrolysis temperature and nitrogen pressure in the chamber lead to an increase of the material specific capacitance and reduction of the cell equivalent resistance. The obtained results demonstrate the possibility of utilizing C–N/SiC material for the manufacture of supercapacitor electrodes.

Active machine learning model for the dynamic simulation and growth mechanisms of carbon on metal surface

Substrate-catalyzed growth offers a highly promising approach for the controlled synthesis of carbon nanostructures. However, the growth mechanisms on dynamic catalytic surfaces and the development of more general design strategies remain ongoing challenges. Here we show how an active machine-learning model effectively reveals the microscopic processes involved in substrate-catalyzed growth. Utilizing a synergistic approach of molecular dynamics and time-stamped force-biased Monte Carlo methods, augmented by the Gaussian Approximation Potential, we perform fully dynamic simulations of graphene growth on Cu(111). Our findings accurately replicate essential subprocesses–from the preferred diffusion of carbon monomer/dimer, chain or ring formations to edge-passivated Cu-aided graphene growth and bond breaks by ion impacts. Extending our simulations to carbon deposition on metal surfaces like Cu(111), Cr(110), Ti(001), and oxygen-contaminated Cu(111), our results align closely with experimental observations, providing a practical and efficient approach for designing metallic or alloy substrates to achieve desired carbon nanostructures and explore further reaction possibilities.

Fullerene-Amyloid Complexes as Perspective Nanocomposites: Molecular Docking Studies

The molecular interactions between the amyloid fibrils from Aβ-peptide, insulin and α-synuclein and fullerenes of different sizes, including C20, C36, C60, C70, and C84, have been studied using the molecular docking approach. The fullerenes are found to bind to the loop or turn region of Aβ- and α-synuclein fibrillar assemblies, but reside at the end of insulin amyloid fibers, reflecting the lower affinity of carbon nanostructures to the latter aggregated protein. For all systems studied here, the fullerene binding to amyloid fibrils is size-dependent, with larger fullerenes exhibiting a higher binding affinity and a lower total energy of complexation. The analysis of side chain contacts highlights the pivotal role of van der Waals forces, specifically, alkyl and π-alkyl interactions, in the stabilization of the fullerene-amyloid complexes. The results obtained are discussed in terms of novel nanocomposite materials based on carbon nanoparticles and fibrillar proteins, as well as of the fullerene role in anti-amyloid therapy.

Comparative analysis of modified reverse degree topological indices for certain carbon nanosheets using entropy measures and multi criteria decision‐making analysis

AbstractThe diverse applications of various carbon nanostructures have sparked significant research interest. The potential significance of carbon nanosheets lies in their exceptional mechanical, electrical, and thermal properties, enabling advancements in various technological applications such as energy storage, electronics, and engineering, playing important roles in material science and nanotechnology. In the field of mathematical chemistry, topological indices play a crucial role by providing numerical insights into molecular structures. These insights facilitate predictive correlations with chemical properties and reactivity, ultimately finding utility in areas like drug design and material sciences. Expanding on this, the study delves into the application of entropy‐based methodologies that originates from the arrangement of chemical structures. By assessing the complexity and other features of these structures, graph entropies are translated into information‐theoretic metrics. This article examines modified reverse degree‐based topological indices with its universal applicability to all degree‐based indices. The standout feature is the adaptable parameter “” effectively shaping the molecular graphs degree sequence to best fit each dataset with their unique physicochemical properties, distinguishing it from conventional fixed degree methodologies. Additionally, we investigate graph entropies and examine the impact of varying the parameter “” on entropy measures across a range of nanosheet structures. The research focuses on characterizing carbon nanosheets, employing effective (MCDM) multiple criteria decision‐making methods like VIKOR, TOPSIS, and SAW. Through these techniques, a comprehensive comparative analysis of the nanosheets is conducted with the aim of establishing optimized rankings for each type based on their unique attributes and characteristics.

Compact and accurate chemical mechanism for methane pyrolysis with PAH growth

A reliable and compact chemical mechanism of gas-phase methane pyrolysis leading to formation of large polycyclic aromatic hydrocarbon (PAH) molecules has been developed. This model is designed for studies of carbon nanostructure synthesis such as carbon black and graphene flakes, including soot growth kinetics. Methane pyrolysis with carbon nanostructure synthesis is a two-stage process where conversion of CH4 to C2H2 precedes the growth of PAH molecules from acetylene. We present a single chemical mechanism that accurately describes both stages. We have constructed a compact and accurate chemical mechanism capable of modeling both stages of methane pyrolysis based on the ABF [1] mechanism which was expanded with the most prominent reaction pathways from the mechanism by Tao [2] for small PAH molecules and HACA pathways for larger PAH molecules, up to 37 aromatic rings. The resulting mechanism was validated through comparison to multiple available sets of experimental data. Good agreement with the experimental data for both processes was obtained. Performance of the mechanism was tested for pyrolysis of methane-rich mixtures under long residence times leading to abundant formation of PAH molecules. It is shown that the inclusion of larger PAH species (up to A37) in the chemical mechanism is important for accurate prediction of the fraction of carbon converted to PAH molecules and, correspondingly, the residual fraction of acetylene in the mixture. The mechanism file is available upon request.

Engineering the growth and electrochemical assessments of phosphorous-doped nitrogen-based carbon nanofibers with 3D-interconnected weaving network structure for high-energy symmetric supercapacitors

The growing demand for sustainable energy sources has led to a change in attention towards developing cost-effective, high-performance energy storage devices. The construction of porous carbon network nanostructures with high surface area is complex for current-generation supercapacitors, mainly due to molecular flexibility and carbon production constraints. This work successfully produced a porous carbon nanostructure by doping phosphorous into nitrogen-based carbon nanofibers (P-doped NCNFs) utilizing a simple and controllable approach. This process entailed electrospinning diammonium hydrogen phosphate and polyacrylonitrile, subsequent high-temperature carbonization, and substantial segmented hydrogen peroxide activation processes. The P-doped NCNFs had a notable surface area of 100.69 m2 g−1, characterized by a distinct 3D-interconnected weaving network morphology. The 1 % P-doped NCNFs exhibited an exceptionally high capacitance of 265 ± 2 F g−1 when tested in a three-electrode setup at a current density of 0.5 A g−1. In addition, the constructed symmetrical supercapacitors with two identical P-doped NCNFs using a neutral Na2SO4 electrolyte exhibited remarkable electrochemical characteristics, which include a substantial capacitance of 225 ± 2 F g−1 at a current density of 0.5 A g−1, a high energy density of 30.9 Wh kg−1, an excellent Coulombic efficiency of 98.8 % over 6000 cycles, an impressive power density of 250 W kg−1, and significant capacitance retention of 85.6 %. These findings suggest that P-doped NCNFs could be excellent options for next-generation high-performance supercapacitors.

Effects of mechanical properties of carbon-based nanocomposites on scaffolds for tissue engineering applications: a comprehensive review.

Mechanical properties, such as elasticity modulus, tensile strength, elongation, hardness, density, creep, toughness, brittleness, durability, stiffness, creep rupture, corrosion and wear, a low coefficient of thermal expansion, and fatigue limit, are some of the most important features of a biomaterial in tissue engineering applications. Furthermore, the scaffolds used in tissue engineering must exhibit mechanical and biological behaviour close to the target tissue. Thus, a variety of materials has been studied for enhancing the mechanical performance of composites. Carbon-based nanostructures, such as graphene oxide (GO), reduced graphene oxide (rGO), carbon nanotubes (CNTs), fibrous carbon nanostructures, and nanodiamonds (NDs), have shown great potential for this purpose. This is owing to their biocompatibility, high chemical and physical stability, ease of functionalization, and numerous surface functional groups with the capability to form covalent bonds and electrostatic interactions with other components in the composite, thus significantly enhancing their mechanical properties. Considering the outstanding capabilities of carbon nanostructures in enhancing the mechanical properties of biocomposites and increasing their applicability in tissue engineering and the lack of comprehensive studies on their biosafety and role in increasing the mechanical behaviour of scaffolds, a comprehensive review on carbon nanostructures is provided in this study.

Unravelling the formation of carbyne nanocrystals from graphene nanoconstrictions through the hydrothermal treatment of agro-industrial waste molasses.

The delicate synthesis of one-dimensional (1D) carbon nanostructures from two-dimensional (2D) graphene moiré layers holds tremendous interest in materials science owing to its unique physiochemical properties exhibited during the formation of hybrid configurations with sp-sp2 hybridization. However, the controlled synthesis of such hybrid sp-sp2 configurations remains highly challenging. Therefore, we employed a simple hydrothermal technique using agro-industrial waste as the carbon source to synthesize 1D carbyne nanocrystals from the nanoconstricted zones of 2D graphene moiré layers. By employing suite of characterization techniques, we delineated the mechanism of carbyne nanocrystal formation, wherein the origin of carbyne nanochains was deciphered from graphene intermediates due to the presence of a hydrothermally cut nanoconstriction regime engendered over well-oriented graphene moiré patterns. The autogenous hydrothermal pressurization of agro-industrial waste under controlled conditions led to the generation of epoxy-rich graphene intermediates, which concomitantly gave rise to carbyne nanocrystal formation in oriented moiré layers with nanogaps. The unique growth of carbyne nanocrystals over a few layers of holey graphene exhibits excellent paramagnetic properties, the predominant localization of electrons and interfacial polarization effects. Further, we extended the application of the as-synthesized carbyne product (Cp) for real-time electrochemical-based toxic metal (As3+) sensing in groundwater samples (from riverbanks), which depicted superior sensitivity (0.22 mA μM-1) even at extremely lower concentrations (0.0001 μM), corroborating the impedance spectroscopy analysis.

Metal–organic framework-derived hierarchical porous N/Co-doped carbon-supported sponge-like Pd–SnO2 nanostructures for low-temperature CO oxidation

Metal–organic framework-derived porous N/Co-doped carbon (MOF-PNC) anchored sponge-like Pd–SnO2 nanoparticles (Pd–SnO2/MOF-PNC), prepared by microwave-irradiation, annealing and chemical etching, delivered excellent low-temperature carbon monoxide oxidation.

Fast proton transport enables the magnetic relaxation response of graphene quantum dots for monitoring the oxidative environment in vivo.

A magnetic relaxation switch (MRS) that targets small molecules such as H2O2 is difficult to realize because of the small size of the targets, which cannot gather enough MRS probes to form aggregates and generate a difference in magnetic relaxation times. Therefore, the development of small molecule-targeted MRS is strongly dependent on changes in the interfacial structure of the probe, which modulates the proton transport behavior near the probe. Herein, functionalized graphene quantum dots (GQDs) consisting of GQDs with disulfide bonds, polyethylene glycol (PEG), and paramagnetic Gd3+ were used as the MRS probe to sense H2O2. The structure of GQDs changed after reacting with H2O2. The PEG assembled a tube for transmitting changes in GQDs via proton transport and thus enabled the magnetic relaxation response of the probe towards H2O2. Pentaethylene glycol was experimentally and theoretically proven to have the strongest ability to transport protons. Such a probe can be applied in the differentiation of healthy and senescent cells/tissues using in vitro fluorescent imaging and in vivo magnetic resonance imaging. This work provides a reliable solution for building a proton transport route, which not only enables the response of the MRS probe towards the targets but also demonstrates the design of carbon nanostructures with proton transport behaviors.

Tailoring giant quantum transport anisotropy in nanoporous graphenes under electrostatic disorder.

During the last 15 years bottom-up on-surface synthesis has been demonstrated as an efficient way to synthesize carbon nanostructures with atomic precision, opening the door to unprecedented electronic control at the nanoscale. Nanoporous graphenes (NPGs) fabricated as two-dimensional arrays of graphene nanoribbons (GNRs) represent one of the key recent breakthroughs in the field. NPGs interestingly display in-plane transport anisotropy of charge carriers, and such anisotropy was shown to be tunable by modulating quantum interference. Herein, using large-scale quantum transport simulations, we show that electrical anisotropy in NPGs is not only resilient to disorder but can further be massively enhanced by its presence. This outcome paves the way to systematic engineering of quantum transport in NPGs as a novel concept for efficient quantum devices and architectures.

Oxidative desulfurization of VGO using carbon nanostructures created by NTP-pyrolysis of fuel oil

Desulfurization of heavy oil fractions is complicated due to the high content of stable polycyclic systems including thiophene ring. Therefore, there is a need to develop new efficient and cost-effective desulfurization methods. The catalytic activity of carbon structures obtained by plasma-chemical pyrolysis of hydrocarbon feedstock (fuel oil, non-hydrorefined vacuum gas oil and catalytic cracking residue) was investigated in this work. The catalytic activity of carbon structures was investigated in relation to the process of oxidative desulfurization of light vacuum gas oil. The oxidation process was carried out at 60°C using ultrasonic dispersion for 1 minute. The oxidation products were extracted with furfural. As a result of oxidation followed by extraction, the sulfur content in gas oil decreased from 0.64 to 0.24% wt.

Dynamics of carbon framework of coal tar pitch with carbon additives in the thermolysis process

This paper studies the transformation of the carbon framework of coal tar pitch in the process of thermolysis in the presence of carbon additives of different structures. It is established that as a result of the application of all investigated carbon additives, the content of volatile products released as a result of the thermolysis of the ash, including carcinogenic compounds, decreases, which contributes to the increase of the coke residue yield. The highest yield of coke residue was found when using nanostructured carbon materials as an additive, but the structure of the resulting carbon material is more disordered than in the case of individual pitch. It is shown that the use of such additives promotes the formation of graphite-like structures in the process of thermolysis of pitch and to a greater extent than amorphous carbon additives, reduces the amount of carcinogenic volatile products of coal tar pitch thermolysis.

Applications and synthesis of nanostructured carbon in the food industry

Applications and synthesis of nanostructured carbon in the food industry

In English

The article discusses methods for obtaining carbon nanostructures (CNS), as well as their use to create three-dimensional (3D) products using FDM, CJP, SLA, SLS technologies. The process of manufacturing consumables for 3D printing technologies (FDM, CJP, SLA, SLS) for creating new composite 3D products based on carbon nanostructures is described. The paper contains a detailed description of which methods of CNS synthesis are more productive and how they allow you to guarantee the production of one or another type of CNS. The paper analyzes the existing 3D printing technologies using CNS, developed a scheme for the full cycle of creating a 3D product containing CNS, taking into account various methods for the synthesis of CNS with the transformation of graphite or other carbon-containing material. It also describes the process of creating composite coils for FDM 3D printing from nanocomposite filaments (rigid polymer-CNS) based on a rigid polymer, which have undergone the process of preparation in a special mixer. The process of preparing consumables and printing a 3D volumetric product using FDM, CJP, SLA, SLS technologies using CNS is described. An overview of consumables for 3D products of FDM technology is presented. The analysis of composite 3D products (ceramic-CNS, rigid polymer-CNS) obtained by FDM and CJP technology was carried out. The paper also describes the three most productive methods for the synthesis of CNS: plasma-chemical synthesis in gas or liquid and pyrolytic method. These synthesis methods make it possible to guarantee the production of a certain type of CNS and have a high quality of the obtained nanoproducts. Various types of CNS are described, including soluble (fullerenes and fullerene-like structures) and insoluble nanostructures (graphenes, carbon nanotubes, carbon nanofibers, nanocomposites, etc.).

Large hysteretic hydrogen adsorption in Double Wall Carbon Nanotubes bundles

We have observed isothermal large hysteretic hydrogen adsorption in samples made out of Double Wall Carbon Nanotubes (DWCNTs) bundles at 50 K, 77 K and 150 K and up to 1.3 MPa of pressure. In order to gain information about the microscopic mechanisms responsible for this remarkable phenomena we made a series of inelastic neutron scattering measurements at various temperatures and H2 loads. The elastic component of the signals (diffraction) observed at different loads are consistent with the uptake of the H2 molecules within the interstitials of the bundles. The quasielastic part, i.e., that centered around the null energy transfer, displays a dependence on momentum transfer which is reproduced by a 1D dimensional diffusion model as expected for interstitial confinement of the H2 fluid. Finally, the inelastic signals reveal rotational spectra that preclude the possibility of chemisorption onto the sample metallic impurities. To the best of our knowledge this is the first observation of supercritical H2 hysteretic adsorption in nanostructured carbons not ascribed to chemisorption onto metallic centers. Instead, the results point to the hierarchy of energy and entropic barriers associated with the adsorption into the bundle interstitials through the external grooves as the microscopic origin of the observed metastable adsorption.

The oxygen behavior in the carbon nanostructures synthesized by CVD with recycling precursor

The oxygen behavior in the carbon nanostructures synthesized by CVD with recycling precursor

Microstructure and Phase Composition of Ti-Al-C Materials Obtained by High Voltage Electrical Discharge/Spark Plasma Sintering.

Titanium-based composite materials arouse interest in fields like aerospace, transportation, medicine, and other applications. This research project presents the analysis of phase composition of sintered Ti-Al-C composite materials under high voltage electrical discharge. The new technology, described in the previous work of the authors, allows to synthesise the composites containing various intermetallics, carbides, and nanostructures. The samples of Ti-Al-C powder composites were tested by SEM, Raman spectroscopy, and XRD. It was determined that the treatment of the powder by high voltage electrical discharge (HVED) and further sintering at high temperatures using the spark plasma sintering (SPS) method encouraged the formation of the intermetallic reinforcing phases, carbides, and different nanocarbon structures like graphene and fullerenes, as well as pure graphite. Intermetallic phases and nanocarbon structures improved the mechanical and physical properties of the composites. By using the experimental methods mentioned above, the phase composition of Ti-Al-C powder composites obtained at different sintering temperatures was determined. It was revealed that new composite materials produced by HVED and further SPS were rich with carbides, intermetallics, and MAX phases. Therefore, the carbon nanostructures (graphene and graphite) were detected existing in the structure of the produced new Ti-Al-C composite material. All these reinforcing particles improved the microstructure and the mechanical properties of the composites, as was proved in the previous research by the authors and by the different scientific resources. This project is a pilot experimental work, therefore not all peaks of Raman and XRD were detected; they will be analysed in future works.

All-scale approach to evaluate the elasticity and strength of carbon-allotrope reinforced polyimide

This computational study conducts a comprehensive all-scale analysis to predict the mechanical behavior (elasticity and strength) of polyimide matrices (Kapton®) reinforced with carbon nanostructures, spanning nanoscale, microscale, mesoscale, and macroscale. Representative volume elements at each scale undergo tensile and shear loadings to extract mechanical properties. Homogenization techniques are applied to transition between scales, considering these properties. Two nanostructures (graphene and γ-graphyne) are explored as reinforcements, evaluating the influence of volume fraction and orientation on composite mechanical properties. Results are validated through comparison with theoretical, computational, and experimental studies. Composite materials exhibited significant improvements in stiffness (up to 44% at a volume fraction of 0.5%) and tensile strength (up to 25% at a volume fraction of 0.5%) compared to the pristine polymeric matrix.