Types Of Carbonaceous Materials Research Articles

Kinetics and Mechanism of the Simultaneous Carbothermic Reduction of FeO and MnO from High-Carbon Ferromanganese Slag

The carbothermic reduction of 38.7 pct MnO-12.1 pct CaO-5.4 pct MgO-9.3 pct Al2O3-24.1 pct SiO2-10.4 pct FeO slag in Ar at 1600 °C was studied using the sessile drop wettability technique. Pure graphite, coke, and charcoal were used as the carbon material substrates. The reduction rates were evaluated by sampling at different reduction times and by analyzing the chemical compositions of the reduced slag and the produced metal. The carbothermic FeO reduction from slag is initially fast followed by a much slower reduction rate. However, the rate of the MnO reduction is slow in the fast FeO reduction stage, and it starts to increase significantly during the slow FeO reduction stage. The kinetics of FeO and MnO reduction are affected by the type of carbonaceous materials. Moreover, the rate of the carbon dissolution/transfer into the produced metal phase and the amount of the transferred manganese to the metal phase depend on the type of carbon. Based on the experimental observations and the thermodynamic calculations, a mechanism for MnO reduction was proposed. According to this mechanism, MnO is mainly reduced through a metallothermic reduction by Fe and the rate of MnO reduction is controlled by the rate of the consumption of FeO from the slag, which takes place simultaneously. In contrast, the rate of FeO reduction in the fast initial reduction stage is controlled by the rate of the carbon dissolution/transfer into the metal phase. However, at the second slow FeO reduction stage, it is reduced mainly by the solid carbon.

Carbon Nanotube Electrode Materials for Li-air Cells

In this paper, carbon nanotubes (CNTs) have been investigated as oxygen cathode materials used for Li-oxygen/air cells and compared with carbon black (CB), graphite (G), and active carbon (AC). Both multi wall nanotube (MWNT) and single wall nanotube (SWNT) showed advantage when compared with other types of carbonaceous materials. The higher discharge capacity of CNTs than AC is explained by the exposed surface area surface area. SWNT is very promising as a cathode material in terms of higher capacity and energy density for Li-oxygen/air cells, while MWNT has low cost advantages. CNT based high energy density Li-oxygen/air cells have the potential to be developed into high next generation specific energy power sources.

Irreversible processes during the lithium intercalation into graphite: the passive film formation

Comparative studies of three type of carbonaceous materials—the modified oxidized graphite, thermoexpanded graphite, and carbon paper—prior to and after galvanostatic cycling in 1 M LiClO4 solution in propylene carbonate-dimethoxyethane mixture are carried out using standard porosimetry. It was shown that the mean (effective) thickness of the passive film [solid electrolyte interface (SEI)] at the electrodes of the modified oxidized graphite and thermoexpanded graphite equals a few nanometers. The comparison of porosimetric and electrochemical data shows that the passive film comprises both lithium carbonate and alkylcarbonates. Additionally, this comparison allows corroborating the concept on the formation of polymer (or oligomer) component of the passive film at least at the thermoexpanded graphite electrodes.

Silver-Carbon Nanocapsule Electrocatalyst for Oxygen Reduction Reaction

The types of carbonaceous material and electrocatalyst are the critical components in fabrication of gas diffusion electrodes for fuel cells and metal-air batteries. In this study, carbon nanocapsule and Ag-carbon nanocapsule powders were synthesized and characterized for their electrochemical performances as oxygen reduction electrocatalyst in alkaline electrolyte using commercial noncatalyzed gas diffusion electrode as substrate. The polarization response of the carbon nanocapsule demonstrated enhanced electrocatalytic capability over those of XC-72R and vapor growth carbon fiber, delivering at . In addition, Ag-carbon nanocapsule powders exhibited a value of at , surpassing commercially available Mn-catalyzed, and MnCo-catalyzed gas diffusion electrodes. Galvanostatic discharge of these Ag-carbon nanocapsule powders from confirmed their stability and sustainability. This report identified a class of carbon material that not only exhibits electrocatalytic capability itself but also provides opportunity as substrate for known electrocatalysts.

Corrosion of steel reinforcement in structural concrete with carbon material addition

Different types of carbonaceous materials have been added to concrete mixes and their effect on the corrosion of embedded steel has been studied. Using a constant water/cement ratio of 0.42 and different amounts of carbonaceous materials and different curing periods the evolution of the corrosion process in the embedded reinforced bars has been determined. The addition of small quantities of carbonaceous materials to the mixture produces a reduction of the concrete permeability. Tests demonstrate that a decrease of the corrosion level occurs when the content ratio of carbon material addition is increased.

Carbonaceous materials in the acid residue from the Orgueil carbonaceous chondrite meteorite

Abstract— Insoluble organic matter (IOM) dominates the HF/HCl residue of the Orgueil (CI) carbonaceous chondrite meteorite. The IOM is composed primarily of two C‐rich particle types. The first has a fluffy texture similar to crumpled tissue paper, and the second type occurs as solid or hollow nanospheres. High‐resolution transmission electron microscope (HRTEM) images of the fluffy material show it is poorly ordered, with small, irregularly shaped regions having fringes with 0.34–0.38 nm spacings and locally 0.21 nm cross‐fringes. Nanodiamonds occur in the fluffy material. The rounded C‐rich particles are common in the residue and their HRTEM images show neither fringes nor nanodiamonds. Both types of carbonaceous materials have a high aromatic component, as revealed by electron energy‐loss spectroscopy (EELS), with up to 10 at% substitution by S, N, and O. The average compositions of the fluffy material and nanospheres are C100S1.9N3.7O4.9 and C100S2.4N5.0O3.9, respectively. The structural and chemical heterogeneity of the carbonaceous materials may represent material from multiple sources.

Evaluation of Methods To Obtain Geosorbent Fractions Enriched in Carbonaceous Materials That Affect Hydrophobic Organic Chemical Sorption

To better understand sorption, separation methods are needed to enrich soils and sediments in one or more types of carbonaceous materials (CM), especially in fine grain materials where physical separation is not possible. We evaluated a series of chemical and thermal treatment methods by applying them to four different CMs prepared in our laboratory: a humic acid (HA), a char, a soot, and a heat-treated soot (HN-soot). Before and after each treatment step, CM properties were evaluated including aqueous phase sorption with trichloroethene (TCE). Results indicate that treatment with hydrofluoric (HF) and hydrochloric acid (HCI) to remove silicate minerals, and with trifluoroacetic acid (TFA) to remove easily hydrolyzable organic matter, has relatively little effect on the humic acid mass (<19% change) and TCE sorption to this material. Subsequent treatment with NaOH to extract fulvic and humic acids results in almost complete removal of the humic acid mass (>92%) and has little to no effect on the masses of the char and two soots (<8% change) and TCE sorption to these materials. Treatment with acid dichromate to remove kerogen and humin also has little effect on masses of the char and soots (<16% change), but TCE sorption to these materials is significantly altered (by >10x in some cases), and there is strong evidence of surface oxidation based on X-ray photoelectron and diffuse reflectance Fourier transform infrared spectroscopy results. The last step, thermal treatment, which targets char removal, also destroys >96% of the soots pretreated with acid dichromate. However, when thermal treatment is applied to the original soots, <32% of these materials are destroyed. Thermal oxidation also affects sorption to one of the soots (by approximately 2x at low concentration), and surface oxidation is evident. These results suggest that treatment with HCl, HCl/HF, TFA, and NaOH can be applied to soils and sediments to obtain CM enrichment fractions for sorption evaluation, but that acid dichromate and heat treatment may not be appropriate for these purposes.

High‐temperature reduction of iron oxides by solid carbon or carbon dissolved in liquid iron–carbon alloy

The reaction between iron oxides and carbon was experimentally studied at temperatures higher than 1473 K employing solid carbon or carbon dissolved in liquid iron as a reducing agent. Iron oxides–carbon composite pellets were submitted to thermogravimetric analysis under inert gas in the range 1473–1623 K; the carbon was in the form of graphite, coke fines and charcoal. It has been determined that the type of carbonaceous material has little effect in the reaction rate at high temperatures. The activation energies obtained varied from 46 to 120 kJ/mol, well below the ones obtained at lower temperature ranges, and it is proposed that at high temperatures the controlling mechanism of the reaction is heat transfer. Composite pellets and fired or cold bonded iron oxide pellets were also added to iron–carbon baths in the temperature range 1573–1912 K. It has been found that up to 1711 K the composite pellets present reaction times significantly shorter than the pure oxide pellets, whereas at higher temperatures the reaction times of both pellets are similar.

Hot Gas Cleaning of Producer Gas from Biomass Gasification Using Carbonaceous Materials as a Bed Additive

In the hot gas cleaning of producer gas generated from biomass gasification at 1173K, the ability of tar removal was investigated using various carbonaceous materials as a bed additive at the temperatures of 473 to 673K. Activated carbon, charcoal, and charcoal derived from feedstock were employed. The ability of tar removal was evaluated based on the difference in weights of the carbonaceous materials, before and after gasification. Carbonaceous materials had the ability of tar removal at the temperatures of 473 to 673K. It was largely dependent on the type of carbonaceous materials used and gas cleaning temperature. The spe-cific surface area and average pore diameter of activated carbon would influence the ability of tar removal, and the activated carbon with a large specific surface area and a large average pore diameter was the most effective for tar removal at 573 K. In charcoal derived from feedstock, the ability of tar removal was similar to that in inactive ceramic balls.

Structural characteristics of carbon nanorods and nanotubes grown using electron cyclotron resonance chemical vapor deposition

Different types of carbonaceous materials were synthesized by electron cyclotron resonance chemical vapor deposition on Ni-coated glass substrates with radio-frequency (rf) self-biasing using a gas mixture of CH4 and Ar. Vertically aligned carbon nanorods and multiwalled carbon nanotubes (MWNTs) were obtained at the rf bias voltages of −100 and −200 V, respectively. High-resolution transmission electron microscopy indicated that the distance between two graphene layers of carbon nanorods is much larger than that of well-graphitized MWNTs having a typical value of graphite. Structural characteristics of carbon nanorods and well-graphitized MWNTs were investigated by electron-energy-loss spectra, in which the energy of π+σ plasmon peak obtained from carbon nanorods shifts to a lower value of 23.8 eV, compared to 25.5 eV from well-graphitized MWNT. Low-energy loss plasmon due to π electrons at 6 eV was not observed in carbon nanorods, but clearly defined for well-graphitized MWNTs. In addition, x-ray photoelectron spectroscopy showed that the delocalization of π electrons becomes more pronounced as the structure of carbonaceous films evolves into more crystalline phase from carbon nanowalls to well-graphitized MWNTs with increasing rf bias voltages. These results can suggest that ionic bombardment energy at high rf bias voltages provides sufficient internal energy for dehydrogenation from hydrocarbon molecules, and thus well-graphitized MWNTs can be synthesized even at low temperatures.

Gold losses from cyanide solutions part II: The influence of the carbonaceous materials present in the shale material

Gold was found to be mainly adsorbed onto the carbonaceous particles in the Beatrix shale material with possible minor loss of gold due to co-precipitation of gold with Mg(OH) 2 and Fe(OH) 3. Two types of carbonaceous material were present in low concentrations in the Beatrix shale and resembled kerogen. The one type can be described as filamentous particles and the other as roundish particles. Rank measurements done on the carbonaceous particles in the shales showed that they fall in the anthracite range. Adsorption of gold on carbonaceous material of similar rank showed that anthracite has the highest propensity to adsorb gold. This suggests that the carbonaceous particles would have similar gold adsorption properties as anthracite. The lack of an obvious correlation between the propensity of a shale to adsorb gold and its carbon content is probably due to the fact that not all the carbonaceous particles are liberated during milling so that they can be brought into contact with' the gold cyanide solution.

Nitrous oxide decomposition and reduction over copper catalysts supported on various types of carbonaceous materials

Copper supported on three different allotropic forms of carbon materials have been prepared and evaluated as catalysts for the N2O decomposition and reduction reactions. It was found that all the catalysts underwent severe deactivation during the N2O decomposition reaction due to the gasification of carbon substrates. This behavior was particularly evident when activated carbon was used as the support medium. The chemical identity of the active entity involved in the carbon gasification process is believed to consist of a mixture of Cu+ and Cu2+ species and, according to the well established mechanism, the reaction proceeds in such a manner so that the surface of the catalyst undergoes a redox cycle at the gas/solid carbon interface. The introduction of CO into the system was shown to result not only in an enhancement in the activity of the desired N2O decomposition reaction, but also served to inhibit the deleterious carbon gasification process. In addition, this procedure stabilized the copper particles in the metallic state, which is the active species responsible for the dissociation of N2O. Copper dispersed on a diamond substrate appeared to attain the highest activity for the N2O reduction reaction, a feature that is associated with the ability of the metal to undergo a wetting and spreading action on the support surface, possibly resulting in an epitaxial relationship between the two components.

Commercial Cokes and Graphites as Anode Materials for Lithium - Ion Cells

AbstractSeveral types of carbonaceous materials from Superior Graphite Co. were investigated for lithium ion intercalation. These commercially available cokes, graphitized cokes and graphites have a wide range of physical and chemical properties. The coke materials were investigated in propylene carbonate based electrolytes and the graphitic materials were studied in ethylene carbonate / dimethyl solutions to prevent exfoliation. The reversible capacities of disordered cokes are below 230 mAh / g and those for many highly ordered synthetic (artificial) and natural graphites approached 372 mAh / g (LiC6). The irreversible capacity losses vary between 15 to as much as 200 % of reversible capacities for various types of carbon. Heat treated cokes with the average particle size of 10 microns showed marked improvements in reversible capacity for lithium intercalation. The electrochemical characteristics are correlated with data obtained from scanning electron microscopy (SEM), high resolution transmission electron microscopy (TAM), X - ray diffraction (XRD) and BET surface area analysis. The electrochemical performance, availability, cost and manufacturability of these commercial carbons will be discussed.

The Carbon-Lithium Negative Electrode for Lithium-Ion Batteries in Polymer Electrolyte

AbstractSeveral types of carbonaceous materials are evaluated as negative electrodes for lithium storage in polymer electrolyte based cells operated at 100ºC. The corresponding faradaic efficiencies of the spherical cycle and the achieved reversible first capacity and rate capacity will be given. A meso carbon yielded a higher capacity than the theoretical 372 mAh/g. This is tentatively explained by the necessary enhancement of the carbon/polymer interfacial properties through the formation of C-Li-O bonding at the carbon surface and by the possible formation of multilayers of lithium on the external a,b planes of disordered carbons. The formation of the passivating layer on the carbon surface will be described.A lithium-ion type battery using coke and LiNiO2 as the negative and positive leads and POE-LiCIO4 was operated at 100ºC and cycled galvanostatically. Good reversible capacity was attained with the LiNiO2 electrode.

Heterogeneous reactions of SO2 and NO2 on carbonaceous surfaces

Four different types of carbonaceous material (active carbon, graphitized carbon black, source samples from a power plant and from an urban heating boiler) were exposed to synthetic gas mixtures of SO2 and SO2 + NO2 in sub-ppm ranges at two different relative humidities (60 and 90% r.h.). The interaction of SO2 and NO2 with the carbonaceous materials led to sulfate and to three other products: NO, HONO and NO2−. Formation of NO and NO2− was observed only on active carbon while the other three materials yielded HONO. It was also found that NO2 enhances the deposition of SO2 only on the source sample from the power plant at 60% r.h., whereas the material from the urban heating boiler had no effect both at low and high r.h. The results obtained show that no general statements on the effect of NO2 on the heterogeneous reaction of SO2 on these carbonaceous materials can be made and also that NO2 reactions in the presence of SO2 on carbon-containing surfaces should be considered as a source for the production of HONO in the urban environment.

Metamorphism of carbonaceous material in the Tono contact aureole, Kitakami Mountains, Japan

Abstract Optical and X‐ray studies of carbonaceous material in the Tono contact metamorphic aureole, Kitakami Mountains, northeast Japan, have revealed that metamorphic graphitization proceeded through two discontinuous changes: first, optically anisotropic domains develop within the coaly phytoclast, forming transitional material, and then, ordered graphite crystallizes by the decomposition of pre‐existing carbonaceous materials. Coaly material disappears in the uppermost chlorite zone. Transitional material appears in the middle of the lower chlorite zone. Graphite appears in the upper chlorite zone and its modal abundance increases across the andalusite iso‐grad to the cordierite isograd where all the carbonaceous materials have converted to graphite. The apparently continuous variation in the crystallographic parameters of the bulk carbonaceous material during graphitization is largely due to variation in the modal proportions of three types of carbonaceous materials. The temperature of graphitization in the present area is at least 100°C higher than the temperature in the Sanbagawa and New Caledonia high‐pressure metamorphic terrains, probably due to the slow reaction rate of metamorphic graphitization and to the short duration of contact metamorphism.

A novel method of examining carbonaceous deposits on spent catalyst surfaces

Xenon ion-bombardment used in conjunction with Auger electron spectroscopy was able to discriminate two types of carbonaceous materials accumulated on the surfaces of iron oxide and rhenium/iron-oxide catalysts spent for CO hydrogenation at 250°C and 2.1 MPa. One of the carbonaceous materials was easily eliminated from the surfaces by ion bombardment or by heat-treatment in vacuo at 150°C. On iron oxide only this “soft” carbonaceous material was present. On rhenium/iron oxide, bombardment-resistant “hard” carbonaceous material was also found. The presence of this hard carbonaceous material had little effect on the level of CO hydrogenation activity or the deactivation behavior of this catalytic system.

Reactivity of carbonaceous species deposited on precipitated iron catalyst by carbon monoxide and synthesis gas

The types of carbonaceous species formed on a precipitated iron catalyst by interaction with carbon monoxide and synthesis gas have been studied by isothermal and temperature programmed reduction of the deposited species with hydrogen. It has been found that by (dissociative) adsorption of carbon monoxide on a freshly reduced catalyst, a type of carbonaceous material is formed that is located in subsurface layers. By CO adsorption on a catalyst that has been used previously in a deposition/reduction experiment, a very reactive carbon species is formed. Upon hydrogenation, this species not only forms methane but also ethane. Hydrogenation of carbonaceous species deposited during the synthesis shows that the same highly reactive species is present on the active catalyst, indicating that this species is the active surface species in the synthesis.

Studies of hydrothermal gold deposition - (pt.) 1, carlin gold deposit, nevada, the role of carbonaceous materials in gold deposition

Studies of fresh carbonate host rocks and unoxidized gold ores of the Carlin mine indicate that gold, quartz, barite, pyrite, and other sulfides were introduced into the Roberts Mountains Formation by acid hydrothermal solutions. Laboratory investigations on the carbonaceous materials in the host rocks and ores and studies of reactions between carbonaceous materials and gold-bearing solutions show that the rocks contain: (1) An activated carbon component capable of adsorbing gold chloride or gold cyanide complexes from solution; (2) A mixture of high-molecular-weight hydrocarbons usually associated with the activated carbon components; and (3) An organic similar to humic acid, containing functional groups capable of interacting with gold complexes to form gold organic compounds. Although the exact structure of the gold organic compound(s) is not known, the most attractive possibility is chelation, where ligands such as N, S, or O in organic acids would easily displace the chloride ion from aurous chloride complexes and form stable gold chelates. Subsequent oxidation of the gold organic compounds destroys the organic component and leads to the formation of metallic gold. The relative amounts and types of carbonaceous materials are of principal importance in determining the chemical state and amount of gold deposited in carbonaceous limestone, although such factors as temperature, pH, and the oxidation state of the system are also involved.Although most of the gold ores at the Carlin mine are in the Silurian Roberts Mountains Formation and are at least several hundred feet stratigraphically below the Roberts Mountains thrust fault, disseminated replacement-type gold deposits could form in the lower-plate Devonian limestones (designated the Popovich Formation at the Carlin mine) and in carbonate and shale units of the upper-plate Ordovician Vinini Formation. In a structural setting that would provide satisfactory channels for movement of gold-bearing solutions, physical characteristics and chemical and mineralogical compositions, including the presence of organic materials, indicate that all three formations are favorable for replacement and deposition of gold.

Extraction of uranium from aqueous solution by coal and some other materials

Uranium in nature is commonly associated with carbonaceous material. Laboratory studies were therefore conducted to determine the relative ability of various types of carbonaceous material and some other substances to remove uranium from solution. The results of these experiments indicate that the low-rank coals are more effective in extracting uranium than any of the other materials used. A chemical determination shows that nearly 100 percent of the available uranium in solution is removed by subbituminous coal. The uranium is apparently retained in the coal by an irreversible process. The notable affinity of uranium for coalified plant remains suggests that some uranium deposits may have been formed over a long period of time by the extraction of uranium from dilute ground-water solutions. A possible application of the results of this work may be the extraction of uranium by coal from natural water or from waste solutions from uranium-processing industrial plants.