C — Journal of Carbon Research

The global carbon cycle model is presented as a natural self-regulating machine that provides renewable biomass synthesis during evolution. The machine consists of two parts, geological and biosphere. Between the parts, there is an interaction. The geological part is controlled by the movement of lithosphere plates, which is under the guidance of gravitational forces from celestial bodies acting on the Earth. The movement of the lithosphere plates is divided into a phase of a relatively quick movement, occurring in the tectonically active state of the Earth’s crust, named the orogenic period, and a phase of a relatively slow movement, occurring in the phase of the tectonically quiet state of the crust, named geosynclinal period. In the orogenic period, the energy of moving plates’ collisions is sufficient to initiate sulfate reduction, proceeding in the subduction zone. This is the reaction where sedimentary organic matter is oxidized. Resultant CO₂ is injected into “atmosphere—hydrosphere” system of the Earth. Its concentration achieves maximal values, whereas oxygen concentration drops to a minimum since it reacts with the reduced sulfur forms that evolve in the thermochemical sulfate reduction and due to binding with reduced forms of metals, coming to the Earth’s surface with volcanic exhalations. Carbon dioxide initiates photosynthesis and the associated biosphere events. In the geosynclinal period, the sulfate reduction ceases, and CO₂ does not enter the system anymore, though photosynthesis in the biosphere proceeds in the regime of CO₂ pool depletion. Under such conditions, the surface temperature on the Earth decreases, ending with glaciations. The successive depletion of the CO₂ pool results in a regular sequence of climatic changes on the Earth. The ratio of CO₂/O₂ is the key environmental parameter in the orogenic cycle providing climatic changes. They consistently vary from hot and anaerobic in the orogenic period to glacial and aerobic by the end of the geosynclinal period. The climatic changes provide biotic turnover. Especially abrupt changes accompany the transition to a new orogenic cycle, resulting in mass extinction of organisms and the entry of huge masses of biogenic material into the sediment. This provided the conditions for the formation of rocks rich in organic matter (“black shales”). It is shown that the suggested model is supported by numerous geological and paleontological data evidencing the orogenic cycles’ existence and their relationship with the evolution of photosynthesis. Full article

With its exceptional strength characteristics, diamond has some mechanical drawbacks, significant brittleness being among them. In particular, some HPHT-grown diamonds crack when the extreme parameters inherent to the diamond growth process gradually decrease. The cracking is caused by excessive stress due to the poor plastic properties of the diamond growth catalytic medium at certain stages of reducing the pressure and the temperature. An insulating container with the growth cell and heating circuit fragment inside can also make a significant contribution to the probability of cracking. This paper considers the possibility of minimizing the mechanical stress in the growth cell and, consequently, in the diamond crystal by choosing the optimal trajectory for the decrease in the pressure and temperature from diamond growth conditions to normal conditions. Full article

In recent years, the possibility of combining graphene and carbon nanotubes has attracted much attention from researchers attempting to obtain new multifunctional hybrid materials with promising properties. Optoelectronics shows potential as a field of application for such hybrid structures. The variety of existing structural configurations of graphene-nanotube hybrids requires preliminary detailed studies of their optical properties by computer simulation methods. In this paper, we consider island-type graphene-nanotube hybrid films formed by AB-stacked bilayer graphene and single-walled carbon nanotubes (SWCNTs). In this case, bilayer graphene is located above the surface of the nanotube, forming areas with an increased density of carbon atoms, creating so-called “islands.” To meet the conditions of a real experiment, we chose chiral SWCNTs (12,6) with a diameter of 1.2 nm, which are most often synthesized in real experiments. All constructed atomistic models of bilayer graphene-chiral SWCNT films were tested for thermodynamic stability at room temperature and proved their suitability for research. Using Kubo-Greenwood formalism, we calculated the complex optical conductivity tensor and absorbance coefficient in the wavelengths of ultraviolet, visible, and near-infrared radiations. The photocurrent spectra are calculated based on the obtained absorption spectra and solar radiation spectra on the earth’s surface (AM1.5) and outside the earth’s atmosphere (AM0). The results of calculations revealed regularities in the influence of structural parameters (nanotube diameter, graphene width) on the optical and optoelectronic properties of graphene-chiral SWCNT (12,6) with an island structure. Full article

DLC coatings have low adhesive bond strength with the substrate and a high level of residual stresses. This paper is devoted to researching a complex of characteristics of a DLC-Si coating deposited on samples of SiAlON ceramics with intermediate coatings (CrAlSi)N pre-formed to improve the adhesive bond strength employing vacuum-plasma spraying. DLC-Si coatings were formed by chemical vapor deposition in a gas mixture of acetylene, argon, and tetramethylsilane supplied through a multichannel gas purge system controlling the tetramethylsilane volume by 1, 4, 7, and 10%. The SiAlON samples with deposited (CrAlSi)N/DLC-Si coatings with different silicon content in the DLC layer were subjected to XPS and EDX analyses. Tribological tests were carried out under conditions of high-temperature heating at 800C. The nanohardness and elasticity modulus of the rational (CrAlSi)N/DLC-Si coating with Si-content of 4.1% wt. were 26 ± 1.5 GPa and 238 ± 6 GPa, correspondingly. The rational composition of (CrAlSi)N/DLC-Si coating was deposited on cutters made of SiAlON ceramics and tested in high-speed machining of aircraft nickel-chromium alloy compared to uncoated and DLC-coated samples. The average operating time (wear resistance) of (CrAlSi)N/DLC-Si(4.1% wt.)-coated end mills before reaching the accepted failure criterion was 15.5 min when it was 10.5 min for the original cutters. Full article

Waste insulation electrical cables (WIEC) currently do not have an added value, due to their physical–chemical characteristics. Carbonization is known to enhance feedstock properties, particularly fuel and material properties; as such, this article aimed to study the production and activation of biochars using WIEC and lignocellulosic biomass wastes as feedstock. Biochars were produced in a ceramic kiln with an average capacity of 15 kg at different temperatures, namely 300, 350 and 400 °C. After production, the biochars were further submitted to a washing process with water heated to 95 °C ± 5 °C and to an activation process with 2 N KOH. All biochars (after production, washing and activation) were characterized regarding an elemental analysis, thermogravimetric analysis, heating value, chlorine removal, ash content, apparent density and surface area. The main results showed that the increase in carbonization temperature from 300 to 400 °C caused the produced biochars to present a lower amount of oxygen and volatile matter, increased heating value, greater chlorine removal and increased ash content. Furthermore, the activation process increased the surface area of biochars as the production temperature increased. Overall, the carbonization of WIEC mixed with lignocellulosic wastes showed potential in enhancing these waste physical and chemical properties, with prospects to yield added-value products that activates biochar. Full article

Activated carbon (AC) is widely utilized in water treatment, gas adsorption, and purification as well as the protection of environment due to the characteristics of prominent catalytic and adsorbent effect. The heating performances are therefore of significant importance for the further applications. The main objective of this study was therefore to detail the heating performance of activated carbon in microwave field, and the factors affecting the heating performance were also explored. In this study, the heating performance of AC as affected by microwave power (400, 450, 500, 550, and 600 W), feeding load (5, 10, 15, 20, and 25 g), and reactor volume (50, 100, 150, 200, and 250 mL) were detailed and reported. The results showed that when the microwave powers were 400, 450, 500, 550, and 600 W, the temperatures of AC increased to the desired value (about 200 °C) within 90, 85, 70, 60, and 35 s with average heating rates of 2.0, 2.2, 2.8, 3.0, and 5.9 °C/s, respectively. When the feeding loads were 5, 10, 15, 20, and 25 g, the temperatures of AC increased to desired temperature within 40, 70, 60, 50, and 50 s with average heating rates of 4.2, 2.8, 3.1, 3.50, and 3.55 °C/s, respectively. When the reactor volumes were 50, 100, 150, 200, and 250 mL, the temperatures of AC increased to the desired temperature within 25, 60, 70, 70, and 160 s with average heating rates of 7.6, 3.3, 2.8, 2.6, and 1.2 °C/s, respectively. In general, the faster heating rate of activated carbon was achieved at higher microwave power, more feeding load, and smaller reactor volume. Fitting formulae were given to predict the transient temperatures of AC in the microwave field, and the relative errors were in the ranges of −15.4~12.4%, −15.4~13.5% and −18.7~12.4% at different microwave powers, feeding loads, and reactor volumes, respectively. Full article

Pharmaceutical and personal care products are emerging as a new category of environmental pollution. Analytical drug detection from a biological sample for detection is still crucial today. Mefenamic acid (MA) is an anti-inflammatory drug utilized for its antipyretic and analgesic properties, which is harmful to patients at higher dosages and is also recognized as a chemical pollutant that harms the environment. In this view, Dysprosium manganite/carbon nanofiber (DMO/CNF) was prepared by hydrothermal method for the electrochemical detection of MA. DMO/CNF/GCE exhibits high selectivity, excellent anti-interference, good stability, and reproducibility toward the detection of MA. The enhanced electrochemical performance of DMO/CNF/GCE was attributed to their synergetic interaction. Under optimized conditions, DMO/CNF/GCE shows a wide linear range of 0.01–741 μM and a low LOD of 0.009 μM. Satisfactory recoveries were obtained for human blood and tablet samples. Thus, the proposed DMO/CNF nanocomposite emerges as a promising material for the detection of MA. Full article

This paper describes a single-stage synthesis process for activated carbon using cherry seeds. The influences of the carbonization temperature and the time were investigated. Using the BET method, the surface area of the obtained activated carbons was determined, as well as the pore distribution, while SEM images provided further insight into the structure of the surface. Next, the adsorption isotherm was derived. For the test, Pd(II) chloride complex ions were used. It was found that the obtained activated carbon were suitable for palladium(II) recovery from diluted aqueous solutions. Out of the tested parameters of carbon synthesis, the most optimal one was found to be 500 °C for 3 h. Additionally, it was confirmed that the increase in the adsorption temperature affects the increase in palladium load from 1.6 mg/g at 20 °C to 15.6 mg/g at 50 °C (for the best-performing sample). This fact may suggest that the process of adsorption is associated with chemical reactions. Full article

A top-down synthesis of graphene quantum dots (GQD) was carried out by hydrothermal method from different carbon sources (graphene, multi-walled carbon nanotubes, and black carbon) and ${\mathrm{H}}_2{\mathrm{O}}_2$ as an oxidizing agent, with an N source added in the reaction to modify the chemical surface of the GQD, giving rise to the nanomaterial N-GQD. The modified chemical surface of N-GQD partially allowed the nucleation and coupling of gold nanoparticles from a $\mathrm{H}\mathrm{A}\mathrm{u}\mathrm{C}{\mathrm{l}}_4$ solution. The X-ray diffraction spectrogram confirms the amorphization of the precursor materials, while the functionalized surface of N-GQD was characterized through UV-Vis, Fourier transform infrared, and photoluminescense spectrometry; TEM and FE-SEM show particle sizes between 8 and 15 nm. [email protected] presence can be confirmed by UV-Vis spectroscopy and TEM analysis, showing partial coupling and nanoparticle nucleation of Au in the structure with particle sizes between 20 and 40 nm. Full article

In this study, ryegrass straw agricultural residue (Lolium multiflorum L.) was employed as an adsorbent material to remove methylene blue (MB) dye from aqueous solutions. Four adsorbents were produced using phosphoric acid and pyrolysis as activating agents. The samples were analyzed with TGA, FTIR, SEM, and XRD techniques. A rapid adsorption of the MB was obtained with the ryegrass treated with 40% H₃PO₄, reaching equilibrium in 2 min. Moreover, a maximum adsorption capacity of 80.79 mg g⁻¹ and a removal efficiency of 99% were achieved. The results demonstrate a good performance of adsorbents from ryegrass for removing dye contaminants, such as methylene blue, from the aqueous solutions. Full article

The substitution of traditional copper power transmission cables with lightweight copper–carbon nanotube (Cu–CNT) composite fibers is critical for reducing the weight, fuel consumption, and CO₂ emissions of automobiles and aircrafts. Such a replacement will also allow for lowering the transmission power loss in copper cables resulting in a decrease in coal and gas consumption, and ultimately diminishing the carbon footprint. In this work, we created a lightweight Cu–CNT composite fiber through a multistep scalable process, including spinning, densification, functionalization, and double-layer copper deposition. The characterization and testing of the fabricated fiber included surface morphology, electrical conductivity, mechanical strength, crystallinity, and ampacity (current density). The electrical conductivity of the resultant composite fiber was measured to be 0.5 × 10⁶ S/m with an ampacity of 0.18 × 10⁵ A/cm². The copper-coated CNT fibers were 16 times lighter and 2.7 times stronger than copper wire, as they revealed a gravimetric density of 0.4 g/cm³ and a mechanical strength of 0.68 GPa, suggesting a great potential in future applications as lightweight power transmission cables. Full article

We consider the effect of the external magnetic field on the in-plane conductivity in the AA-stacked bilayer graphene system in the strong excitonic condensate regime. We include the effects of the applied inter-layer electric field and the Coulomb interactions. The on-site and inter-layer Coulomb interactions were treated via the bilayer Hubbard model. Using the solutions for the physical parameters in the system, we calculate the in-plane conductivity of the bilayer graphene. By employing the Green-Kubo formalism for the polarization function in the system, we show that the conductivity in the AA bilayer system is fully controlled by the applied magnetic field. For the partial filling in the layers, the electrical conductivity is different for different spin orientations, and, at the high values of the magnetic field, only one component remains with the given spin orientation. Meanwhile, for the half-filling limit, there is no spin-splitting observed in the conductivity function. The theory evaluated here shows the new possibility for spin-controlled electronic transport in the excitonic bilayer graphene system. Full article

[5.5.5.5]hexaene is a [12]annulene ring with a symmetrically bound carbon atom in its center. This is the smallest hydrocarbon with a hyperbolic paraboloid shape. [5.5.5.5]hexaene and related hydrocarbons are important building blocks in organic and materials chemistry. For example, penta-graphene—a puckered 2D allotrope of carbon—is comprised of similar repeating subunits. Here, we investigate the thermochemical and kinetic properties of [5.5.5.5]hexaene at the CCSD(T) level by means of the G4 thermochemical protocol. We find that this system is energetically stable relative to its isomeric forms. For example, isomers containing a phenyl ring with one or more acetylenic side chains are higher in energy by ∆H₂₉₈ = 17.5–51.4 kJ mol⁻¹. [5.5.5.5]hexaene can undergo skeletal inversion via a completely planar transition structure; however, the activation energy for this process is ∆H^‡₂₉₈ = 249.2 kJ mol⁻¹ at the G4 level. This demonstrates the high configurational stability of [5.5.5.5]hexaene towards skeletal inversion. [5.5.5.5]hexaene can also undergo a π-bond shift reaction which proceeds via a relatively low-lying transition structure with an activation energy of ∆H^‡₂₉₈ = 67.6 kJ mol⁻¹. Therefore, this process is expected to proceed rapidly at room temperature. Full article

Currently, heavy metal-contaminated groundwater is an environmental concern. This study investigated the use of bamboo biochar, chitosan-impregnated biochar, and iron-impregnated biochar for arsenic, iron, and manganese removal from groundwater. Isotherms of arsenic, iron, and manganese adsorption by bamboo derived biochar were compared with those of commercial activated carbon in simulated groundwater composed of single and trinary heavy metal solutions. The binding of heavy metals by virgin and loaded bamboo biochar and activated carbon was also investigated by sequential extraction. Chitosan and iron-impregnated biochar had enhanced arsenic adsorption, but these sorbents turned the pH of solution acidic, while it was alkaline for activated carbon. Adsorption equilibrium times of arsenic and iron were faster for single than trinary heavy metal systems because less ion competition occurred at active sites. The Langmuir model fitted the adsorption data well. The maximum adsorption capacities of arsenic, iron, and manganese by bamboo biochar in trinary heavy metal system were 2.2568, 0.6393, and 1.3541 mg g⁻¹, respectively. The main mechanism for arsenic removal was precipitation with iron. Bamboo biochar bound iron in organic and sulfide fractions and manganese with iron-oxide. Bamboo biochar can replace activated carbon as a more efficient and sustainable carbonaceous sorbent material for removal of mixed heavy metals from groundwater within acceptable pH ranges. Full article

Oil spills necessitate the development of effective methods for preventing their damaging effects on the environment. A number of physical, chemical, thermal, and biological methods are used to combat oil spills. Among them, sorption is considered to be efficient in removing thin oil films from water surfaces. Currently, there is an urgent need for simple methods of obtaining oil sorbents that include a magnetosensitive component to optimize the process of removing oil from the water surface. The purpose of the work is to obtain and research oil sorbents resistant to destruction, with increased bulk density and complex magnetosensitivity, based on thermally expanded graphite (TEG) with the inclusion of micro- and nano-particles of iron and its oxides. The structure and composition of the new composite material was characterized using scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffractometry, thermogravimetric analysis, and laser diffraction particle sizing. The composite sorbent comprised TEG with the inclusion of iron-containing magnetosensitive particles. Metal-carbon nanoparticles (MCN) were used as the magnetosensitive component; they had a magnetosensitive iron core covered with a carbon shell. We used two methods of synthesis, namely (i) mechanical mixing of the TEG flakes and MCN particles, and (ii) applying a thermal shock (microwave processing) to the mixture of graphite intercalated with sulphuric acid and micro- and nanoparticles of iron and iron oxides. In the first case, MCN particles were fixed on the faces, edges, and other surface defects of the TEG flakes due to intermolecular forces, coordinate bonds, and electrostatic interaction. The strong adhesion of magnetosensitive iron/iron oxide and TEG particles in the second case was due to the mutual dissolution of iron and carbon components during the thermal shock, which formed an interfacial layer in which iron carbide is present. The presence of magnetosensitive components in the structure of the proposed oil sorbents allows the use of magnetic separation for the localization and removal of oil spills, increases the density of sorbents, and, accordingly, leads to a decrease in windage while retaining the advantageous properties of thermally expanded graphite. According to the results of laboratory studies, the efficiency of removing oil from the water surface is not lower than 95–96%. Full article

This review focuses on techniques for modifying the surface of carbon that is produced from sustainable resources, such as pyrolytic carbon. Many of these materials display high specific surface area and fine particle distribution. Functionalization of a surface is a commonly used approach in designing desired surface properties of the treated material while retaining its bulk properties. Usually, oxidation is a primary step in carbon functionalization. It can be performed as wet oxidation, which is a type of chemical surface modification. Wet oxidation is usually performed using nitric acid and hydrogen peroxide, as well as using hydrothermal and solvothermal oxidation. On the other side, dry oxidation is representative of physical surface modification. This method is based on corona discharge and plasma oxidation which are promising methods that are in line with green chemistry approaches. Whilst the oxidation of the carbon surface is a well-known method, other chemical modification techniques, including cycloadditions and various radical reactions on graphene layers, are presented as an alternative approach. Regarding secondary functionalization, coupling organosilanes to activated carbon is a common technique. Organosilanes bearing reactive groups present a bridge between inorganic species and polymer systems, e.g., epoxy and polyurethane resins, and facilitate the use of carbonaceous materials as reinforcing components for polymers and thermosetting resins. Along with the presented functionalization methods, this review also provides an overview of new applications of modified (i.e., functionalized) carbon materials, e.g., for the building industry, wastewater treatment, semiconducting materials and many more. Full article

There have been several emphasized pathways toward a reduction in carbon footprint in the built environment such as recycling, technologies with lower energy consumption, and alternative materials. Among alternative materials, bio-based materials and nature inspired solutions have been well-received. This study examines the merits of using rice husk ash as a replacement for lime; lime has a high carbon footprint mainly associated with the decomposition of calcium carbonate to calcium oxide to form lime. Lime is commonly used in bituminous composites for roadway construction to mitigate their susceptibility to moisture damage. Replacing lime with a low-carbon alternative could allow a reduction in CO₂ equivalent of bituminous composites. This paper studies the merits of using rice husk ash (RHA) as a substitute for conventional hydrated lime (HL) in bituminous composites. It should be noted that rice industries burn rice husks in a boiler as fuel, generating a substantial volume of RHA. The disposal of this ash has major environmental impacts associated with the contamination of air and water. Here, we study physical and chemical characteristics of both HL and RHA for use in bitumen mixtures. This was followed by examining the extent of dispersion of each filler in bitumen via optical microscopy to ensure their uniform dispersion. The properties of the mixtures were further studied using the Marshall mix design method. It was found that a 25.67% increase in Marshall stability and a 5.95% decrease in optimum binder content were achieved when HL was replaced by RHA at 4% filler concentration. In addition, mixtures containing RHA exhibited higher resistance to cracking and permanent deformation compared to mixtures containing HL. Additionally, 4% RHA in the mix showed stripping resistance similar to the conventional mix with HL. The mixture with 4% RHA had a lower carbon footprint with enhanced economic and environmental impacts compared to the conventional mix with HL. The study results provide insights pertaining to the merits of bio-based materials to reduce the carbon footprint of pavements. Full article

The inclusion of carbon nanotubes (CNTs) in cementitious composites has been studied due to their electrical, thermal, and mechanical enhancing properties. Considering the hydrophobic characteristics of CNTs, these nanomaterials need to be well dispersed in the aqueous media in which they are inserted to guarantee those gains. Among the methods applied to produce such composites is the dispersion of CNTs on the surface of anhydrous cement particles using non-aqueous suspensions such as acetone, ethanol, or isopropanol. Even though those non-aqueous media have been individually studied by researchers, comparisons of the efficiency of CNTs dispersion was not found in the literature. Therefore, as a novelty, the present article aims to analyze the influence of the addition of the multi-walled CNTs dispersed in the cited three types of non-aqueous suspensions on the cement paste’s electrical and mechanical properties. Pastes containing 0%, 0.5%, and 1.0% of CNTs were prepared on the surface of anhydrous cement particles using a pre-dispersion technique based on simultaneous sonication and mechanical agitation in the three cited media. Tests to determine electric-volumetric resistivity, compressive strength, and splitting tensile strength were performed. It was observed that acetone dispersion decreases the cement paste’s electrical resistivity, even without the addition of CNTs. The cementitious composites with CNTs demonstrated increased mechanical strength (both compressive and tensile) using all three dispersion media. Statistical analysis (analysis of variance—ANOVA—and Tukey’s Test) was performed to evaluate the significance of the results. Full article

Microalgae carbon dioxide (CO₂) fixation technology is among the effective ways of environmental protection and resource utilization, which can be combined with treatment of wastewater and flue gas, preparation of biofuels and other technologies, with high economic benefits. However, in industrial application, microalgae still have problems such as poor photosynthetic efficiency, high input cost and large capital investment. The technology of microalgae energy development and resource utilization needs to be further studied. Therefore, this work reviewed the mechanism of CO₂ fixation in microalgae. Improving the carbon sequestration capacity of microalgae by adjusting the parameters of their growth conditions (e.g., light, temperature, pH, nutrient elements, and CO₂ concentration) was briefly discussed. The strategies of random mutagenesis, adaptive laboratory evolution and genetic engineering were evaluated to screen microalgae with a high growth rate, strong tolerance, high CO₂ fixation efficiency and biomass. In addition, in order to better realize the industrialization of microalgae CO₂ fixation technology, the feasibility of combining flue gas and wastewater treatment and utilizing high-value-added products was analyzed. Considering the current challenges of microalgae CO₂ fixation technology, the application of microalgae CO₂ fixation technology in the above aspects is expected to establish a more optimized mechanism of microalgae carbon sequestration in the future. At the same time, it provides a solid foundation and a favorable basis for fully implementing sustainable development, steadily promoting the carbon peak and carbon neutrality, and realizing clean, green, low-carbon and efficient utilization of energy. Full article