Formation Of Carbon Nanostructures Research Articles

In Ukrainian

The regularities of the formation of nanostructures during the evaporation of graphite by the electric ARC – method are studied. Described physicochemical processes in the synthesis reactor . At plasma temperatures taking into account the behavior of particles in electromagnetic fields with extreme temperature and pressure grants. A sequence of organization of matter in the process of forming a structure according to nano-dimensional characteristics is proposed. The self-organization of systems during electric arc evaporation of graphite or graphite-containing electrodes has been studied. The mechanisms of formation of soluble (fullerenes and fullerene-like structures) and insoluble (nanocomposites, CNTs, graphenes) carbon nanostructures are considered. The processes occurring in the electric arc synthesis reactor are analyzed: the process of distribution of charged particles in an electric arc at different times; processes taking place at the anode; the mechanism of carbon vapor formation during graphite evaporation; processes in the gas phase and on the walls of the reactor under the conditions of an electric arc discharge; model of the reactor space zones; formation of carbon nanostructures in the gas phase and on the inner surface of the reactor. use of doped electrodes and metal inserts (sleeves) as catalysts for the synthesis of carbon nanostructures. The sequence of processes in the formation of spherical carbon molecules is studied, and the processes and structural transformations are considered. In the research work, the products (fullerenes and fullerene-like structures, nanocomposites, VNT, graphenes) of electric arc synthesis are presented, and modern methods of analysis are used for their fixation and identification.

Formation of carbon nanostructures in a high-temperature flame

Carbon nanostructures in the form of tubes are formed during the heterophase regime of metal combustion with fluoroplastic. These tubes are filled with condensed particles of combustion products and change the optical properties of the flame.

Fabrication of field-effect transistors with transfer-free nanostructured carbon as the semiconducting channel material

Carbon nanostructures used as the active channel material in field effect transistors (FETs) are appealing in microelectronics for their improved performance, such as their high speed and low energy dissipation. However, these devices require the incorporation of nanostructure transfer steps in the fabrication process flow, which makes their application difficult in large scale integrated circuits. Here we present a novel method for the fabrication of FETs with nanostructured carbon in the channel with p-type semiconducting properties and intermediate drain-source current (IDS) on/off ratio. The method is based on the use of Ni nanoparticles in the source-drain gap region as the seed material for the formation of carbon nanostructures in the FET channel. FETs without Ni nanoparticles in the channel showed no modulation of IDS as a function of gate voltage. The device fabrication process does not require any carbon nanostructure transfer steps since it directly forms carbon nanostructures electrically connected to the device’s source and drain electrodes via electron-beam evaporation of carbon and conventional lithographic processes. Since all device fabrication steps are compatible with existing Si technology processes, they are capable of being further optimized following process development protocols practiced by the semiconductor industry.

Synthesis of porous carbon nanostructure formation from peel waste for low cost flexible electrode fabrication towards energy storage applications

Abstract Porous activated nanostructure carbon is prepared by feasible two steps method utilizing naturally available bio-wastes such as jack fruit peel waste (JFW) and studied the effect of pyrolysis condition for porosity formation. X-ray analysis and BET pore size analysis confirmed the formation of graphitic nature carbon with micro and mesoporous existence. HR-SEM and TEM images of Jack fruit (JF) derived porous carbon samples are shown spherical nanoball and tiny nanotube morphology. High resolution SEM images further confirms that the, increase in the activation temperature increase the uniform hexagon shape porous structure formation. The superior electrochemical activity and recycling stability was achieved for our method prepared (phohphoric acid activation method using graphite crucible mold) porous carbon materials. The Cs (specific capacitance) of the JF-9 (porous carbon prepared Jack fruit at 900 °C) sample was shown 324 F/g at the scan rate of 5 mV/s using Na2SO4 electrolyte. The JF carbon sample exhibits a higher capacitance retention of 93% for upto 5000 cycles. We found that the JF derived porous carbon sample shows higher recycling capacity by Galvano static charge-discharge analysis. The effect of current density and scan rate on specific capacitance property are analyzed in detailed by cyclic-voltammetry , Galvano static charge-discharge method and electrochemical impedance spectroscopy analysis.

Catalytic Synthesis and Study of Carbon–Graphene Structures

The optimum conditions of production, structure, and features of the formation of carbon–graphene composites on nickel–graphene catalysts are determined. A mechanism is proposed for the formation of nickel–carbon–graphene composites that consists of several stages: reduction of graphite oxide and nickel ions; the formation and growth of Ni clusters on reduced graphite oxide; catalytic pyrolysis of ethylene on Ni single crystals attached to a graphene-like support; and the formation and growth of carbon nanostructures on the surface of graphene-like material.

Hydrogen production by catalytic decomposition of methane over Fe based bi-metallic catalysts supported on CeO2–ZrO2

Methane decomposition to produce hydrogen was studied over iron based bimetallic catalysts supported on cerium-zirconium oxide in a continuous flow fixed bed reactor at 700 °C. 15 wt% Fe/CeZrO2 was prepared by wetness impregnation and the promoted Fe catalysts (15 Fe-5 Co/CeZrO2 and 15 Fe-5 Mo/CeZrO2) were prepared by co-impregnation technique. Mo promoted Fe catalyst exhibited the maximum surface area of 24.08 m2/g. X-ray diffraction studies revealed that Fe2O3, Co3O4 and MoO3 were the phases present in freshly calcined catalysts, while the reduced catalysts consisted of phases including elemental Fe, Mo and Fe–Co alloys. Both X-ray diffraction and temperature programmed reduction studies confirmed the complete reduction of metal oxide species under H2 at 700 °C. The catalytic activity of Fe/CeZrO2 was enhanced upon addition of Co and Mo as promoters. The initial hydrogen yield on 15 Fe-5 Mo/CeZrO2 was ~90% and it decreased with increase in time on stream (TOS), and finally stabilized around ~50% after 125 min of TOS. The Co promoted catalyst exhibited similar activity while the initial hydrogen yield on 15 Fe/CeZrO2 was ~83% and dropped to ~33% after 125 min of TOS. Graphitic carbon, Fe3C and Mo2C phases were observed in the XRD patterns of spent catalysts along with elemental Fe and Fe–Co alloy. It was evident from temperature programmed oxidation results that coke formation which deactivates the catalyst was dominant in 15 Fe/CeZrO2 when compared to the promoted (Co and Mo) Fe catalysts where carbon nanostructures were dominant. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the formation of carbon nanostructures on the surface of spent catalysts. The Fe based catalysts supported both tip and base-growth mechanisms for the growth of carbon nanostructures.

Study of the ITO sublayer influence on the tubular carbon nanostructures formation

The study of the formation of catalytic centers and the growth of CNT-based TCN was carried out on the Ni (10 nm)/ITO (100 nm)/Si (370 μm) structure. Shown that the temperature at the stage of heating and growth has a significant impact on the parameters of the formed TCN. Promising for instrumental use, the TCN were formed at a temperature of 750 °C, a heating time of 20 minutes, an activation time of 3 minutes. The effect of plasma ions at the stages of «activation» and growth was also demonstrated.

Algorithms of new methods for material wear resistance estimation

Subject of Research. We consider а new mathematical modeling method for synthesis processes of carbon nanostructures in plasma. The method is characterized by the use of the Boltzmann kinetic equation and particle distribution functions taking into account the paired elastic and inelastic collisions. The widespread use of nanotubes, fullerenes in modern industry is limited by the high cost and low productivity of synthesis methods due to insufficient theoretical study of their formation processes. The aim of the work is to build a model of the processes for obtaining various carbon nanostructures in arc discharge plasma andthe development of effective numerical methods for calculating the conditions improving the synthesis efficiency. Method. The paper presents a method of numerical solution of the considered multidimensional nonlinear problem with the use of nVidia CUDA technology in combination with the parallelization technology on the central and graphic processors. The method gives the possibility to obtain cost-effective solution by applying limited computing resources on a personal computer. Main Results. The developed model makes it possible to describe adequately the processes of formation and growth of cluster groups, which are the basis for the formation of carbon nanostructures in arc discharge plasma, and also to take into account the effect of synthesis conditions on the final product output. Practical Relevance. The developed mathematical model and its elements can be used in the design of plants for the synthesis of carbon nanostructures by thermal evaporation of graphite.

Kinetic approach of plasma processes modeling for synthesis of carbon nanostructures

Subject of Research. We consider а new mathematical modeling method for synthesis processes of carbon nanostructures in plasma. The method is characterized by the use of the Boltzmann kinetic equation and particle distribution functions taking into account the paired elastic and inelastic collisions. The widespread use of nanotubes, fullerenes in modern industry is limited by the high cost and low productivity of synthesis methods due to insufficient theoretical study of their formation processes. The aim of the work is to build a model of the processes for obtaining various carbon nanostructures in arc discharge plasma and the development of effective numerical methods for calculating the conditions improving the synthesis efficiency. Method. The paper presents a method of numerical solution of the considered multidimensional nonlinear problem with the use of nVidia CUDA technology in combination with the parallelization technology on the central and graphic processors. The method gives the possibility to obtain cost-effective solution by applying limited computing resources on a personal computer. Main Results. The developed model makes it possible to describe adequately the processes of formation and growth of cluster groups, which are the basis for the formation of carbon nanostructures in arc discharge plasma, and also to take into account the effect of synthesis conditions on the final product output. Practical Relevance. The developed mathematical model and its elements can be used in the design of plants for the synthesis of carbon nanostructures by thermal evaporation of graphite

Composite multilayer films based on polyelectrolytes and in situ‐formed carbon nanostructures with enhanced photoluminescence and conductivity properties

ABSTRACTWe report a facile route for the fabrication of thin composite films based on polyelectrolytes and carbon nanostructures. Composite films were made by layer‐by‐layer assembly of polyelectrolyte multilayers utilizing embedded dextran sulfate (Dex) solution as a carbon source. Raman measurements indicate the formation of carbon nanostructures from the Dex precursor over the whole film. Formation of these nanostructures results in enhanced photoluminescence and an increase in conductivity by two orders of magnitude to about 0.055 S cm−1. The latter corresponds to the level of wide‐gap semiconductors, in contrast to the initial insulating polyelectrolyte film. A distinct peak of photoluminescence of the films is found in the blue region at the wavelength of 450 nm. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47718.

Formation of carbon nanostructures in nuclear graphite under high-temperature in situ electron-irradiation

Defect evolution in nuclear graphite has been studied in real time using high-temperature in situ transmission electron microscopy. In situ electron-irradiation was conducted at 800 °C on a 200 kV transmission electron microscope with a dose rate, given in terms of displacements per atom per second, of approximately 1.46 × 10−3 dpa/s. Defect domains consisting of ordered arrangements of pentagons, hexagons, and heptagons exist intrinsically in nuclear graphite and in addition are readily produced via electron-irradiation; however, at elevated temperatures these defect domains undergo atomic rearrangements resulting in the formation of carbon nanostructures via curling and closure of the basal planes. The formation of fullerenes and other structures due to thermal annealing or high-temperature electron-irradiation has been observed in disordered regions of the microstructure and interstitially between basal planes. These defect structures result in localized swelling and expansion of crystallites along the c axis; thus, it is proposed as one of the many atomic mechanisms involved in the dimensional change of nuclear graphite subjected to high-temperature irradiation.

On-surface synthesis of carbon nanostructures by dehalogenative and dehydrogenative homocoupling reactions

Because of its diversity in nature, research on carbon materials has always been a hot topic. With the continuous development of nanotechnology, especially the application of scanning probe microscopy (SPM), surface chemistry has become one of the hot research areas. Recently, many researchers, including our group, have used scanning probe microscopy to fabricate a variety of novel carbon nanostructures through surface activation of hydrocarbons and carbon-halogen bonds under ultra-high vacuum (UHV) conditions. In this review, combined with the recent research work of this group, we focus on the study of the formation of carbon nanostructures on the metal surface through the activation of hydrocarbons and carbon halides, and explore the reactivity of the precursor molecules on the surface.

Effects of wavelength and fluence on the graphene nanosheets produced by pulsed laser ablation

In this work, graphene nanosheets and carbon nanoparticles were synthesized by nanosecond pulsed laser ablation in liquid nitrogen using Q-switched Nd:YAG laser. The aim is to investigate the wavelength dependence of carbon nanostructures formation mechanisms using fundamental and second harmonic of Nd:YAG laser irradiations at different laser fluence. Carbon nanoparticles and graphene nanosheets fabricated by pulsed laser ablation show the spherical and transparent sheets morphology, respectively, whereas, those due to the fundamental and second harmonic of Nd:YAG laser undergo fragmental shapes. Furthermore, the production rate of carbon nanoparticles produced at 532 nm is noticeably greater than that at 1064 nm wavelength and it can be due to the strong inverse Bremsstrahlung process at IR region. Raman spectra indicate that the graphene nanosheets produced at 532 nm are multilayer while by increasing the laser fluence and wavelength (1064 nm), bilayer graphene nanosheets are formed.

Growth Mechanism and Origin of High sp^{3} Content in Tetrahedral Amorphous Carbon.

We study the deposition of tetrahedral amorphous carbon (ta-C) films from molecular dynamics simulations based on a machine-learned interatomic potential trained from density-functional theory data. For the first time, the high sp^{3} fractions in excess of 85% observed experimentally are reproduced by means of computational simulation, and the deposition energy dependence of the film's characteristics is also accurately described. High confidence in the potential and direct access to the atomic interactions allow us to infer the microscopic growth mechanism in this material. While the widespread view is that ta-C grows by "subplantation," we show that the so-called "peening" model is actually the dominant mechanism responsible for the high sp^{3} content. We show that pressure waves lead to bond rearrangement away from the impact site of the incident ion, and high sp^{3} fractions arise from a delicate balance of transitions between three- and fourfold coordinated carbon atoms. These results open the door for a microscopic understanding of carbon nanostructure formation with an unprecedented level of predictive power.

Enhancing the pyrolysis of scrap rubber for carbon nanotubes/graphene production via chemical vapor deposition

ABSTRACTCarbon nanostructures are considered nowadays as very important materials for both fundamental research and industrial applications because of their well-defined morphologies, which leads to excellent performance in various fields. This study presents the preparation of carbon nanostructures starting from cheap source represented by scrap rubber after pursuing optimized pyrolysis of scrap rubber at 500oC as deduced from thermal gravimetric analysis (TGA). The resulting cracked hydrocarbons from pyrolysis were collected over a well-designed Fe-Ni-Cu/MgO as catalyst via chemical vapor deposition (CVD), in which a growth temperature of 750oC was undertaken for 60 min. A further attempt was elaborated where the scrap rubber was exposed to thermal aging at 90oC for 14 days prior to CVD of its pyrolysis products in order to enhance the cracking process and increase the yield of the lighter hydrocarbons produced which leads to formation of well-defined carbon nanostructures. Characterizations on the produced carbon nanostructures were achieved using transmission electron microscopy (TEM) and Raman spectroscopy. The adsorption of methylene blue on the carbon nanostructures was also studied. The characterizations confirmed that the morphology of the resulting carbon nanostructures derived from scrap rubber without prior thermal aging composed of graphene sheets wrapping carbon nanotubes (CNTs-A). After thermal aging of scrap rubber prior to pyrolysis and CVD, the produced carbon nanostructures composed principally of CNTs (CNTs-B) in a well-defined form in higher yield. The Langmuir model appeared to be best-fitting the adsorption of MB on both samples. High monolayer adsorption capacity of 95 mg MB/g was accomplished in case of CNTs-A versus 60 mg MB/g in case of CNTs-B, respectively. Ultraviolet-Visible (UV-Vis.) spectroscopic study revealed that the presence of MB molecules on the surface of CNTs may enhance the electronic properties of the prepared samples.

Formation of carbon nanostructures by the plasma jets: synthesis, characterization, application

Carbon nanostructures were synthesized without the use of catalysts by the conversion of hydrocarbons in the DC plasma jet system. The samples of carbon nanotubes, nanofibers, graphene, onion like structures have been characterized by electron microscopy, thermal analysis, Raman spectroscopy. An experimental study of the composition of the gas phase with variation of the type of the plasma-forming gas and the type of carbon source was carried out. The synthesized samples have been used in the composition of the functional ceramic and in electrochemical systems.

Microwave plasma enabled synthesis of free standing carbon nanostructures at atmospheric pressure conditions.

An experimental and theoretical study on microwave (2.45 GHz) plasma enabled assembly of carbon nanostructures, such as multilayer graphene sheets and nanoparticles, was performed. The carbon nanostructures were fabricated at different Ar-CH4 gas mixture composition and flows at atmospheric pressure conditions. The synthesis method is based on decomposition of the carbon-containing precursor (CH4) in the "hot" microwave plasma environment into carbon atoms and molecules, which are further converted into solid carbon nuclei in the "colder" plasma zones. By tailoring of the plasma environment, a controlled synthesis of graphene sheets and diamond-like nanoparticles was achieved. Selective synthesis of graphene flakes was achieved at a microwave power of 1 kW, Ar and methane flow rates of 600 sccm and 2 sccm respectively, while the predominant synthesis of diamond-like nanoparticles was obtained at the same power, but with higher flow rates, i.e. 1000 and 7.5 sccm, respectively. Optical emission spectroscopy was applied to detect the plasma emission related to carbon species from the 'hot' plasma zone and to determine the main plasma parameters. Raman spectroscopy and scanning electron microscopy have been applied to characterize the synthesized nanostructures. A previously developed theoretical model was further updated and employed to understand the mechanism of CH4 decomposition and formation of the main building units, i.e. C and C2, of the carbon nanostructures. An insight into the physical chemistry of carbon nanostructure formation in a high energy density microwave plasma environment is presented.

One step synthesis of porous graphene by laser ablation: A new and facile approach

Porous graphene (PG) was obtained using one step laser process. Synthesis was carried out by laser ablation of nickel-graphite target under ultra-high flow of argon gas. The field emission scanning electron microscopy (FE-SEM) results showed the formation of a porous structure and the transmission electron microscopy (TEM) revealed that the porosity of PGs increase under intense laser irradiation. Structural characterization study using Raman spectroscopy, X-ray powder diffraction (XRD) and selected area electron diffraction (SAED) technique showed that the obtained PGs display high crystalline structure in the form of few layer rhombohedral graphitic arrangement that can be interpreted as the phase prior to the formation of other carbon nanostructures.

Reactivity and structural evolution of urchin-like Co nanostructures under controlled environments.

In situ transmission electron microscopy (TEM) of samples in a controlled gas environment allows for the real time study of the dynamical changes in nanomaterials at high temperatures and pressures up to the ambient pressure (105 Pa) with a spatial resolution close to the atomic scale. In the field of catalysis, the implementation and quantitative use of in situ procedures are fundamental for a better understanding of the behaviour of catalysts in their environments and operating conditions. By using a microelectromechanical systems (MEMS)-based atmospheric gas cell, we have studied the thermal stability and the reactivity of crystalline cobalt nanostructures with initial 'urchin-like' morphologies sustained by native surface ligands that result from their synthesis reaction. We have evidenced various behaviors of the Co nanostructures that depend on the environment used during the observations. At high temperature under vacuum or in an inert atmosphere, the migration of Co atoms towards the core of the particles is activated and leads to the formation of carbon nanostructures using as a template the initial multipods morphology. In the case of reactive environments, for example, pure oxygen, our investigation allowed to directly monitor the voids formation through the Kirkendall effect. Once the nanostructures were oxidised, it was possible to reduce them back to the metallic phase using a dihydrogen flux. Under a pure hydrogen atmosphere, the sintering of the whole structure occurred, which illustrates the high reactivity of such structures as well as the fundamental role of the present ligands as morphology stabilisers. The last type of environmental study under pure CO and syngas (i.e. a mixture of H2 :CO = 2:1) revealed the metal particles carburisation at high temperature.

Synthesis of carbon nanostructures from high density polyethylene (HDPE) and polyethylene terephthalate (PET) waste by chemical vapour deposition

In this study, carbon nanostructures were synthesized from High Density Polyethylene (HDPE) and Polyethylene terephthalate (PET) waste by single-stage chemical vapour deposition (CVD) method. In CVD, iron was used as catalyst and pyrolitic of carbon source was conducted at temperature 700, 800 and 900°C for 30 minutes. Argon gas was used as carrier gas with flow at 90 sccm. The synthesized carbon nanostructures were characterized by FESEM, EDS and calculation of carbon yield (%). FESEM micrograph shows that the carbon nanostructures were only grown as nanofilament when synthesized from PET waste. The synthesization of carbon nanostructure at 700°C was produced smooth and the smallest diameter nanofilament compared to others. The carbon yield of synthesized carbon nanostructures from PET was lower from HDPE. Furthermore, the carbon yield is recorded to increase with increasing of reaction temperature for all samples. Elemental study by EDS analysis were carried out and the formation of carbon nanostructures was confirmed after CVD process. Utilization of polymer waste to produce carbon nanostructures is beneficial to ensure that the carbon nanotechnology will be sustained in future.