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Type AU carbon fibres were electrolytically oxidised in aqueous ammonium bicarbonate and were analysed by time-of-flight secondary ion mass spectrometry (TOF SIMS) and, after derivatisation, by X-ray photoelectron spectroscopy (XPS). The reaction of trifluoroacetic anhydride vapour with model polymers and carbon fibre surfaces were examined to enable the surface hydroxyl group concentration [OH]...
The carbonization of an industrial coal-tar pitch was studied by using a tube bomb, as a function of carbonization temperature (550°C-580°C) and inert gas pressure (1-20 bar), and resultant green cokes were evaluated according to electrical resistivity determined using the Van der Pauw method. At 550°C, the carbonization pressure increase leads to an uniaxial arrangement of the produced green coke...
Vapor-grown carbon-fiber (VGCF) reinforced carbon (VGCF-C) composites were studied for thermal and physical properties. Effect of fiber volume fraction and final density of composite on thermal conductivity was investigated. The fiber volume fractions range from 25 v/o to 36% and the final densities range from 1.15 g/cc to 1.59 g/cc. A composite with a fiber volume fraction of 36% and a density...
A method based on the decomposition of phenylacetylene and thiophene on a Ni-powder catalyst has been used to produce nanotubes, circular hollow structures, and other interesting graphitic morphologies. The structures obtained are analyzed using HREM. The stability of bent graphite sheets is studied.
Nitric acid oxidation effectively created acidic functional groups on PAN-based high-strength carbon fibers. The acidic capacities of carbon fibers increased with oxidation time. Typically, 60 minutes of oxidation created 60 μeq acidic functional groups on each gram of carbon fibers. Nitric acid oxidation also caused tensile strength decreases and fiber weight losses. By treating fibers in refluxing...
A petroleum pitch was heat treated using nitrogen sparging or vacuum, and the constitution of samples was investigated as a function of heat-treatment time with microscopy, solid state 13 C NMR, and ESR spectroscopy. The samples were extracted with methylene chloride, and the soluble fractions were characterized by number-average molecular weight, 1 H and 13 C NMR,...
An anthracite coal (Romax = 5.27%, fixed carbon = 95.5%) was deformed in the steady state at various pressures, temperatures, and experimental configurations to assess the effects of stress, strain, and strain energy on graphitization. In simple shear tests, graphite first appears at temperatures as low as 600°C and samples tested at 900°C are predominately graphitized, as evident from optical microscopy,...
Activated carbons with degrees of burn-off between 20% and 80% have been prepared from a semianthracite char by gasification in steam at 1123 K. The adsorption isotherms of nitrogen at 77 K and CO 2 at 273 K have been determined. The pore size distribution has been calculated from t plots, and helium and mercury densities. The ungasified char has a narrow pore size distribution and mainly...
Carbonaceous gel beads were prepared by addition of polymers using ammonia water of amphiphilic carbonaceous material through water-in-oil emulsion. By addition of poly(vinylalcohol), carbonaceous gel beads having dimples were obtained, where the number and size of dimples were dependent on the additive amount and molecular weight of poly(vinylalcohol). However, only beads with smooth surfaces were...
The structures and morphologies of manganese-filled carbon nanotubes and nanoparticles, produced by an arc-discharge method by using a composite anode, were examined with high-resolution transmission electron microscopy, selected-area electron diffraction, and electron nanodiffraction techniques. The HRTEM images and corresponding diffraction patterns show that various manganese carbides (Mn ...
Stability of new graphite-uranyl-sulfate intercalation compounds was studied experimentally as a function of temperature and concentration. The action of uranyl-sulfuric acid aqueous solution leads to the formation of two mixed-phase intercalation products: the usual sulfate phase (d i = 798 pm) and a new uranyl-sulfate phase (d i = 855 pm). This latter phase is obtained alone after...
Fibrous activated carbons were prepared from Nomex [poly(m-phenylene isophthalamide)], in the form of a commercially available woven textile. After carbonisation in nitrogen and activation in either carbon dioxide or steam to varying burn-offs at 1123 K, the resultant activated chars were characterised by nitrogen adsorption, water sorption, and elemental analysis. It appears that the carbonisation...
An investigation has been made of the synthesis of formed (extruded) activated carbons from a bituminous coal by KOH activation. The coal was first pretreated by oxidation with nitric acid, at different levels of oxidation severity, in an attempt to introduce properties similar to those possessed by low-rank coals that can be directly processed in this way. It is found that hard, high-surface-area...
The surfaces of carbon fibers were treated by allylcyanide and xylene/air/argon plasma polymers. The surfaces of untreated and treated fibers were examined by scanning electron microscopy. Electron micrographs of the surface of carbon fibers showed that the surface striations and surface roughness were changed increasingly on the fiber surface after plasma treatment. Surface energy determinations...
Poly(vinylacetylene) obtained by the selective polymerization of monovinylacetylene through the vinyl group has been investigated for its use as an alternative precursor for carbon fibers. The low yield of char obtained on pyrolysis of the polymer in an inert atmosphere was improved dramatically by subjecting its fibers to an oxidative treatment before the carbonization step. Optimization of this...
The release of nitrogen and sulfur during the combustion of coal chars is a major environmental problem. Model coal chars, prepared by the high-pressure carbonisation of polynuclear aromatic precursors to 873 K and subsequent calcination at atmospheric pressure to 1273 K, were studied using temperature-programmed combustion (TPC) in 20% O 2 . These carbons, which are derived from pure organic...
Adsorption at 298 K of phenol, p-cresol, m-chlorophenol, m-aminophenol, and p-nitrophenol from aqueous solutions on activated carbons obtained from an original and a demineralized bituminous coal has been studied. The adsorption capacity of the activated carbons depended on the surface area and porosity of the carbon, the solubility of the phenolic compound, and the hydrophobicity of the substituent...
The shrinkage stress of the precursor polyacrylonitrile (PAN) fibers during oxidation was measured under various conditions, and was found to decrease with cooling the fibers from certain oxidation temperatures, depending strongly on the degree of oxidation, and to become constant below 180°C. Here, the stabilization index, SI, was proposed to be a measure of the oxidation of the PAN fibers, which...
A transmission electron microscope study of experimental shock metamorphism in natural pregraphitic carbon simulates the response of the most common natural carbons to increased shock pressure. Thed -spacings of this carbon are insensitive to the shock pressure and have no apparent diagnostic value, but progressive comminution occurs in response to increased shock pressure up to 59.6 GPa. The function,P...
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