Different Kinds Of Carbon Research Articles

Effective adsorption of basic dye onto different carbon kinds prepared from date stones based on Taguchi design method, kinetic and thermodynamic

Different kinds of carbon (Raw date stone, baked date stone and activated carbon) were prepared and characterized as inexpensive, high surface area, large micropore volume and Effective adsorbents. Material characterization was done using XRD, SEM-EDAX, FTIR and UV-Vis spectroscopy. The activated carbon (AC) possesses a surface area of 571 cm2.g−1. The micropore volume and total pore volume of AC were found to be 0.4785 cm3.g−1 and 0.7267 cm3.g−1 respectively. The effect of backing temperature and activation treatment on surface area and micropore volume were studied. Taguchi factorial design method was used to get the maximum MB dye adsorption onto the surface of AC sorbent. Contact time (60 min), initial dye concentration (10 mmol), adsorbent dosage (0.25g) and solution temperature (293°K) were found to be the best conditions for the more effective absorption process.

Effect of polybrominated diphenyl ethers on the formation of disinfection byproducts in the water system

Disinfection byproducts (DBPs) can be formed from many different kinds of carbon- and nitrogen-based organic materials. This study investigated DBP formation in the presence of two types of polybrominated diphenyl ethers (PBDEs), 2,2′,4,4′-tetrabromodiphenyl ether (BDE 47) and 2,2′,3,3′,4,4′,5,5′,6,6′-decabromodiphenyl ether (BDE 209). The effects of PBDEs on the formation of DBPs upon the chlorination (or chloramination) of Suwannee River humic acid (SRHA) were also evaluated. Results indicated that the chlorination of BDE 47 and BDE 209 resulted in the formation of DBPs, with 1,1,1-trichloro-2-propanone (1,1,1-TCP) being the major DBP type formed. When PBDEs were present in the SRHA solution, a lower amount of CHCl3 was formed, and more 1,1,1-TCP was produced. However, the effects of PBDEs on the formation of DBPs in the real surface water were insignificant because of the complicated water chemistry.

Potential use of different kinds of carbon in production of decayed wood plastic composite

This study investigated the mechanical, chemical structure and thermal properties of hot press molded wood plastic composite (WPC) panels produced from different amounts (30, 40, or 50% weight) of decayed Pinus massoniana Lamb. and polypropylene with chitosan (3 wt%) and different kind of carbon (2 wt%). The results were compared with the properties of WPC produced without carbon. The mechanical, chemical structure and thermal data showed that WPC with carbon was better than WPC without carbon, and the best condition to produce decayed wood plastic composite was hot pressing temperature at 170 °C for12 min, Carbon Nanotubes (CNT) and chitosan (CS) accounting for 2% and 3% of total mass, and the proportion of decayed wood and PVC is 40% and 60%.

Physicochemical properties and catalytic activity of metal–carbon carrier composite materials

Composite metal–carbon materials are created on the basis of different kinds of carbon (multiwall carbon nanotubes, carbon black, Sibunit carbon–carbon material) and metals (Ag, Ni, Co), and their physicochemical and catalytic properties are investigated. It is shown that interaction between metals and carbon carriers proceeds not only with the functional groups on the surfaces of the carriers, but also through a system of–C–C–conjugated bonds. Silver deposited on the surface of a carbon carrier has a crystalline structure (d cr = 10–15 nm), while nickel has an amorphous lamellar structure. Based on quantum-chemical calculations using the density functional theory, it is shown that cumene oxidation occurs via a homogeneous–heterogeneous mechanism.

Importance of constructing synergistic protective layers in Si-reduced graphene oxide-amorphous carbon ternary composite as anode for lithium-ion batteries

Si is regarded as a promising anode candidate for lithium-ion batteries (LIBs) due to its high theoretical capacity and appropriate Li+ ions insertion voltage (<0.4 V vs Li+/Li). However, its intrinsic inferior electronic conductivity and huge volume changes during cycling lead to poor cyclic performance. Integrating Si with carbon materials has been proved to be an efficient route to improve its electrochemical performance. In this report, we successfully synthesized Si-reduced graphene oxide-amorphous carbon (Si-rGO-C) composite assisted with a facile guar gum hydrogel method and studied the protective effect of different kinds of carbon. In the Si-rGO-C ternary composite, the Si nanoparticles (NPs) are embedded in amorphous carbon and tightly anchored to rGO sheets. The amorphous carbon and rGO serve as synergistic protective layers. The Si-rGO-C composite possesses good structural integrity accompanied by enhanced conductive framework. The resulting Si-rGO-C composite exhibits much improved electrochemical performance (a high capacity of 913 mAh g−1 can be maintained after 100 cycles at 0.5 A g−1 with almost no capacity decay) compared with the Si-rGO and Si-C composites with only single protective layer, indicating the importance of constructing synergistic carbon layers in Si-rGO-C ternary composite for LIB anodes.

An Insight into the Convenience and Efficiency of the Freeze-Drying Route to Construct 3D Graphene-Based Hybrids for Lithium-Ion Batteries

Constructing hybrids of transition metal oxides with different kinds of carbon based materials has attracted a lot of attention recently. However, scalable synthesis of homogeneous hybrids with active controllable of microstructure remains great challenge. Here, we proposed a convenient and efficient strategy named freeze-drying process for scalable production of 3D NiO/graphene hybrids. With a controllable procedure, NiO microflowers and graphene layers could preserve uniform configuration from fully mixed solvent to final hybrids materials. The mechanical stability and electrical conductivity of NiO microflowers was increased by graphene. NiO microflowers as spacers intercalated into graphene layers and effectively prevented it from aggregation or restacking, leading to a high specific surface area in hybrids. The NiO/graphene exhibited enhanced cycle stability and rate performance when evaluated as an anode for lithium ion batteries. It rendered high specific capacities about 1000mA h g−1 after 70 cycles, and 770mA h g−1 after 100 cycles at 300mAg−1. Excellent electrochemical properties were probably ascribed to the synergistic effect of NiO microflowers and graphene layers, as a result of smart structure design by a freeze-drying route. This strategy with merits of rational construction and scalable production could establish new aspects for diverse hybrid towards industrialization.

Characterization of Nanocarbon Copper Composites Manufactured in Metallurgical Synthesis Process

Abstract Currently, there is a worldwide search for new forms of materials with properties that are significantly improved in comparison to materials currently in use. One promising research direction lies in the synthesis of metals containing modern carbon materials (e.g., graphene, nanotubes). In this article, the research results of metallurgical synthesis of a mixture of copper and two different kinds of carbon (activated carbon and multiwall carbon nanotubes) are shown. Samples of copper–carbon nanocomposite were synthesized by simultaneously exposing molten copper to an electrical current while vigorously stirring and adding carbon while under an inert gas atmosphere. The article contains research results of density, hardness, electrical conductivity, structure (TEM), and carbon decomposition (SIMS method) for the obtained materials.

Performance and durability of Pt/C cathode catalysts with different kinds of carbons for polymer electrolyte fuel cells characterized by electrochemical and in situ XAFS techniques

The electrochemical activity and durability of Pt nanoparticles on different kinds of carbon supports in oxygen reduction reactions (ORR) were investigated using rotating disc electrodes (RDE) and the membrane electrode assemblies (MEA) of polymer electrolyte fuel cells (PEFC). The mass activity of Pt/C catalysts (ORR activity per 1 mg of Pt) at the RDE decreased, according to the type of carbon support, in the following order; Ketjenblack (KB) > acetylene black (AB) > graphene > multiwall carbon nanotube (MW-CNT) > carbon black (CB), whereas the average size of the Pt nanoparticles and the surface specific activity (ORR activity per electrochemical surface area) did not vary significantly between these carbon supports. These results indicate that the different mass activities of the Pt/C catalysts may originate from the differences in the fraction of Pt on the carbon supports which is available for utilization. The durability of the MEAs of the top two active catalysts Pt/KB and Pt/AB among the five catalysts was examined based on ORR performance, TEM and in situ XAFS. It was found that the performance of the Pt/KB cathode catalyst in PEFC MEA decreased significantly over 500 accelerated durability test (ADT) cycles, whereas the performance of the Pt/AB cathode catalyst in PEFC MEA did not decrease significantly during 500 ADT cycles, it was also found that the Pt/AB possesses 8 times higher durability compared with the Pt/KB. In situ Pt LIII-edge XAFS data in the ADT cycles and stepwise potential operations revealed the different oxidation-reduction behaviors of the Pt nanoparticles on the KB and AB supports. The Pt/KB was oxidized to form surface PtO layers more easily than the Pt/AB in the increasing potential operation from 0.4 VRHE to 1.4 VRHE, and the surface PtO layers of the Pt/AB were reduced to the metallic Pt state more readily than those of the Pt/KB in the decreasing potential operation from 1.4 VRHE to 0.4 VRHE. The XAFS analysis for the Pt valences and the coordination numbers of Pt-O and Pt-Pt demonstrated that the Pt/AB catalyst is more durable than the Pt/KB catalyst in PEFC MEAs.

Hydrogen storage of the Mg–C composites

The effect of different kinds of carbon on the hydrogen sorption kinetics by magnesium–carbon composites was analyzed. To prepare magnesium-based composites by ball milling, graphite and carbon nanomaterials (hereinafter CNM) obtained by the electroexplosion technique were used. Phase composition and structure state of the as-milled and hydrogenated magnesium–carbon and magnesium–nickel–carbon composites have been investigated. It was found the crystallite size in the Mg–CNM composite is smaller in comparison with the magnesium–graphite and magnesium–graphite–nickel mixtures. The CNM additives to magnesium essentially improve the hydrogen sorption kinetics. It results in a reduction of hydrogen sorption temperature. The noticeable hydrogen absorption took place already at a temperature of 363K. The hydrogen capacity was about 5wt% for magnesium ball milled with CNM additives.

Spectromicroscopy of soil colloids

A soil with a high organic content, a calcaric phaeozem, has been imaged in a hydrated state using the Stony Brook scanning transmission X-ray microscope at the NSLS, Brookhaven, USA. This experiment has been performed at the carbon K absorption edge to determine the distribution of organic matter within this soil. Spectromicroscopic methods using the known spectra of humics are helping to distinguish between different kinds of carbon in the sample. In addition, a marsh soil from Northern Germany has been analyzed at the sulfur K-absorption edge with the scanning X-ray microscope at the ESRF (ID 21), Grenoble, France. This soil contains a variety of sulfur containing components, which are attached to the soil colloids. A major source of these components is the microbial activity. In this soil it is possible to identify spectroscopically amino acids like methionin and cysteine and proteins, which are built up from those molecules, and inorganic components like sulfates and sulfides.

Purification of single walled carbon nanotubes by thermal gas phase oxidation

Single walled carbon nanotubes (SWNT) have been produced in an electric arc discharge by using a graphite rod as anode which is filled with a powder mixture of graphite and metallic catalysts like nickel and yttrium. The soot material containing approximately a third of SWNT was collected from the cathode region as a soft, voluminous material. The main by-products in this process are amorphous carbon and graphitic nanoparticles which have to be removed by an appropriate purification process. The as-produced soot material was purified by gas phase oxidation in air at 355 °C. The oxidation of amorphous carbon in air is advantageous against wet chemical methods because it is better controllable. Thermogravimetric analysis and electron microscopy were used to investigate the oxidation behavior of the different kinds of carbon. Oxidation of SWNT and amorphous carbon occurs simultaneously even at moderate temperatures, whereas amorphous carbon is more rapidly oxidized than SWNT. For optimizing the purification procedure by gas phase oxidation, kinetic studies were used to determine the oxidation time for each component in the soot at a given temperature. So it is possible to remove the amorphous carbon quantitatively with minimal losses of SWNT. But it was found that graphitic nanoparticles have the highest stability against oxidation and could therefore not be quantitatively removed by this method without the complete destruction of SWNT. Therefore, the electric arc discharge process has to be a controlled process for minimum production of graphitic nanoparticles to obtain a material with a high content of SWNT.

Dehalogenation potential of municipal waste incineration fly ash. I. General principles.

It is well known that the fly ash from filters of municipal waste incinerators (MWI-FA) shows dehalogenation properties after heating it to 240-450 degrees C. However, this property is not general, and fly ash samples do not possess dehalogenation ability at all in many cases. Fly ash has a very variable composition, and the state of the fly ash matter therefore plays the decisive role. In the present paper, the function of important components responsible for the dehalogenation activity of MWI-FA is analysed and compared with the model fly ash. With the aim of accounting for the dehalogenation activity of MWI-FA, the following studies of hexachlorobenzene (HCB) dechlorination were performed: The role of copper in dehalogenation experiments was evaluated for five types of metallic copper. The gasification of carbon in MWI-FA was studied in the 250-350 degrees C temperature range. Five different kinds of carbon were used, combined with conventional Cu(o) and activated nanosize copper powder. The dechlorination experiments were also carried out with Cu(II) compounds such as CuO, Cu(OH)2, CuCl2 and CuSO4. The results were discussed from the standpoint of thermodynamics of potential reactions. Based on these results, the model of fly ash was proposed, containing silica gel, metallic copper and carbon. The dechlorination ability of MWI-FA and the model fly ash are compared under oxygen-deficient atmosphere. The results show that, under given experimental conditions, copper acts in the dechlorination as a stoichiometric agent rather than as a catalyst. The increased surface activity of copper enhances its dechlorination activity. It was found further that the presence of copper leads to a decrease in the temperature of carbon gasification. The cyclic valence change from Cu(o) to Cu+ or Cu2+ is a prerequisite for the dehalogenation to take place. Thermodynamic analysis of the dechlorination effect, as well as the comparison of dechlorination pathways on MWI-FA and model fly ash, can provide a deeper understanding of the studied reaction.

Reactivity of different kinds of carbon during oxidative purification of catalytically prepared carbon nanotubes

In the purification procedure of catalytically prepared carbon nanotube samples, the oxidative removal of amorphous carbon was investigated. Oxidation was carried out by KMnO4, H2O2, O3 or HClO4. The selectivity of the amorphous carbon burning reaction was studied as a function of the reaction temperature by transmission electron microscopy. The advantages of the different methods are as follows: although oxidation by KMnO4 in an acidic suspension provides nanotubes free of amorphous carbon, and can easily be controlled, it must be followed by filtration and cc HCl treatment in order to dissolve the MnO2 formed during the reaction. Oxidation with hydrogen peroxide does not give undissolved residue on the surface of the tubes. Ozone treatment produces gaseous by-products, but requires higher reaction temperature. This method is more difficult to control. During oxidation, competitive oxidation always takes place: carbon nanotubes and amorphous carbon react simultaneously. While amorphous carbon can be attacked from any direction, carbon nanotubes can be oxidized only from the ends.

Determination of the chemical diffusion coefficient of lithium in multiwall carbon nanotubes

Electrochemical intercalation of lithium into multiwall carbon nanotubes produced by the arc-electric technique has been carried out in button cells to estimate the solid state diffusion coefficients of lithium. An extension of the Galvanostatic Intermittent Titration Technique (G.I.T.T.) of Weppner and Huggins and further developed by Honders is employed. The results are interpreted providing that the lithium species enter the nanotubes perpendicularly to their walls and thus give rise to a necklace structure as observed by Transmission Electron Microscopy (TEM). Finally, the results are compared with the data obtained for different kinds of carbon: carbon fiber, petroleum coke and graphite.

Analysis of cosmic materials: Results on carbon and silicate laboratory analogues

Carbon and silicates are two of the main components of cosmic dust. They change nature through different evolutionary phases, according to the cosmic environment and the experienced processing. To understand the evolution of cosmic materials the study of “laboratory analogues” represents a powerful tool. In this context, systematic analyses are performed at the cosmic physics laboratory of Naples on solid particles, synthesised and processed under carefull controlled conditions. Different kinds of carbon and silicate samples are produced under various environmental conditions and exposed to processes (e.g. thermal annealing, UV irradiation and ion bombardment). The comparative analysis of the results allows us to link intrinsic properties (such as chemical composition and structure) to the optical behaviour of grains. This study offers the opportunity to interpret observations concerning the composition of small bodies in the Solar System, such as spectroscopic results obtained for comets by the Infrared Space Observatory (ISO). Several open questions remain, however, unsolved and await results from new laboratory experiments.

Mechanism of Lithium Insertion in Different Kinds of Carbons

Effects of microtexture were analyzed using mesocarbon microbeads (MCMB) and two reference cokes heat-treated at 1000°C, a mesoporous saccharose coke and a lamellar anthracene coke. The electrochemical performance of MCMB heat-treated at 900°C (340mAh/g for the reversible capacity) are attributed to the specific microtexture of the beads, which are both lamellar (inner part) and mesoporous (outer part). The disorganised phase present at the surface of MCMB favors lithium sorption and further intercalation in the bulk. The electrochemical characteristics of saccharose coke were drastically changed by a mild oxidation at 450°C. The presence of oxygen at the surface plays an important role by enhancing lithium adsorption on surface sites prior to diffusion into the grains.

Reflection of low energy hydrogen from carbon at oblique incidence

The particle reflection coefficient is determined experimentally and by computer simulation for the bombardment of two different kinds of carbon with deuterium at normal and oblique incidence in the energy range from 1 keV down to 33 eV. Highly oriented pyrolytic graphite (HOPG) and EK98 graphites served as targets, the former as an example with a relatively flat surface, the latter with a rough surface topography. The experimental technique is based on the measurement of the trapped amount by nuclear reaction analysis using the reaction d(3He,p)α; protons are detected with a surface barrier detector. It is found that the usual assumption of complete trapping at low fluences is not fulfilled at low energies (≤100 eV). This is demonstrated by measuring the decrease of the implanted amount of deuterium with further bombardment of protons at the same energy. This loss of implanted atoms can be described by an exponential function which can be used to determine the correct trapping coefficient and from this the correct particle reflection coefficient. The experimentally determined particle reflection coefficients for HOPG agree reasonably well with data calculated with the Monte Carlo program TRIM.SP (version TRVMC); only at the lowest energy of 50 eV the experimental values are somewhat higher at intermediate angles of incidence than the calculated ones. The rough surface of EK98 is investigated with a scanning tunneling microscope. It is found that this surface can be described by a fractal surface of dimension 2.05. For this surface agreement of the experimental values with those calculated with the program VFTRIM (based on TRIM.SP, assuming a fractal surface) is found.

Determination of carbon, hydrogen and nitrogen in inorganic compounds by means of an automatic organic elemental microanalyzer

The Hewlett Packard Model 185 CHN Analyzer, which is based on an automated modified Dumas combustion technique and was designed for the analysis of organic materials, has been applied to the determination of carbon, nitrogen and hydrogen in inorganic compounds. With minor modifications to the procedure routinely used for the organic analysis, the instrument has proved to be able to broaden its original application field giving in general good performances in the inorganic domain. A particular emphasis has been put in testing nitrates, carbonates, ammonium salts and different kinds of carbon. Till now it appears that the only materials really difficult to analyze are the refractory nitrides, carbides and carbonitrides. Finally some considerations have been made in respect of the determination of the percent weight composition of mixtures through their carbon, nitrogen and hydrogen content.