The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The formation of diamond surface radicals and their destruction has been investigated using electron paramagnetic resonance (EPR) spectroscopy. The similarity in behavior of diamond paramagnetic susceptibility and thermodesorption with heat-treatment temperature indicates that the formation of paramagnetic centers is a result of the desorption of oxy-functional groups in connection with the simultaneous...
Amino groups react rapidly with both isocyanates and epoxides. Thus, to prepare carbon fibers which might exhibit enhanced adhesion to both polyurethanes and epoxy resin matrices, attempts were made to introduce a high surface amine concentration onto high-strength carbon fibers (derived from PAN) by nitric acid oxidation followed by reaction with excess tetraethylenepentamine (TEPA). Fibers were...
Temperature programmed desorption/reduction techniques have been applied to an investigation of the interaction of hydrogen with oxygen surface complexes and reactive sites on the surface of a resin char during thermal desorption. It is shown that the presence of hydrogen has a number of significant effects on the evolution patterns of the oxides of carbon and water vapor. A number of conclusions...
A model detailing the development of morphology in copolymer PAN (polyacrylonitrile) fibers during oxidative stabilization was recently proposed (Gupta and Harrison, Carbon, 1996, 34, 1427). Some of the main features of this model are: (a) a two-step oxidative stabilization process wherein reactions initiate in the amorphous phase, and progress to the crystalline phase at high temperatures; (b) intramolecular...
The reactivity between a petroleum pitch (Ashland A 240) and oxygen was studied at 1 MPa oxygen pressure and temperatures between 200 and 280°C using thin pitch films. After oxidation the pitch was analyzed by FT-IR and XPS with respect to the formation of oxygen-containing functional groups. A green mix shaped into cylindrical bodies was treated with oxygen for various times for the determination...
A green mix composed of 65% pitch coke powder and 35% petroleum pitch (Ashland A 240) was shaped into cylindrical bodies, 30 mm in diameter and 30 mm in height. The bodies were treated with flowing pure oxygen at 200°C and pressures of 0.1 MPa and 1 MPa. The kinetics of oxidation were analyzed by measuring the oxygen uptake, radial temperature gradients in the body, formations of CO 2 and...
Carbon nanotube-containing carbonaceous materials were gasified in a thermo-balance. The gasification was carried out in 1 vol% oxygen stream at 1023 and 823 K. The gasification behavior of nanotubes was observed using an unique technique, a fixed-point observation technique with a transmission electron microscope. The gasification behavior of carbon nanotubes strongly depended on the gasification...
The purpose of this study is to evaluate the effects of burn-off on thermal shock resistances and thermal shock fracture toughnesses of a carbon fiber reinforced carbon composite (C/C composite) and three fine-grained isotropic graphites. These thermal shock resistances and thermal shock fracture toughnesses were degraded slightly by air oxidation at 500°C. The extents of degradations of the thermal...
Electrochemical formation of graphite intercalation compounds (GICs) has been studied in the electrolyte with mixed sulfuric acid and acetic acid. The results show that, with addition of acetic acid, GICs can be synthesized in the electrolyte with sulfuric acid concentration as low as 3.6M, even though no GIC is formed in pure acetic acid. The stage structure of the synthesized GICs varies with the...
Cellulose based activated carbon cloth has been oxidized by air, nitric acid, hydrogen peroxide and iron nitrate cristallohydrate melt treatments. Thermogravimetric analysis, selective neutralization, X-ray photoelectron spectroscopy and electrical resistance measurements have been applied to characterize the products. The amount and type of oxygen surface groups have been determined for the different...
Gas-phase oxidation of hydrogen sulphide catalysed by the activated carbons of different origin and formation of SO x in this process was studied. Using XPS, it was shown that H 2 S adsorption from an inert atmosphere on activated carbons resulted in the formation of surface oxygen-containing complexes and elemental sulphur. It is suggested that carbon surface functional groups contribute...
Studies were undertaken to determine the role of surface oxygen complexes and metals on activated carbon on adsorption of selected aromatics. Three kinds of activated carbons (F400, MP and Darco G60) were used in the study. The F400 carbon was treated by oxygenation, deoxygenation and HCl-washing processes. Batch adsorption tests were used to evaluate the effects of surface oxygen complexes and...
Various surface treatments were performed previously to modify the surface condition of vapor grown carbon fibers (VGCF). However, by these surface treatments, in addition to the surface chemistry, the bulk chemistry and structure of the VGCF was influenced as well. Raman spectroscopy and nitrogen adsorption were used to study the changes in bulk chemistry and structure, and surface morphology,...
The electronic structures of pure and boron-doped graphene layers have been investigated using the semi-empirical Molecular Orbital Package (MOPAC) and large clusters of carbon atoms. It is shown that boron-doping on the edge and internal lattice sites of the graphene layer produces very different effects on the electronic structure around the edges. It is found that the substitutional boron atoms...
Two activated carbons with different degree of activation, 20 and 46% burn-off, were obtained from olive stones by steam activation. These samples were oxidized with a concentrated solution of (NH 4 ) 2 S 2 O 8 for different periods of time, up to a maximum of 24 hours, studying the variation in surface area, pore texture and surface chemistry during the oxidation...
A novel silicon-containing carbon precursor was synthesised by reacting a petroleum pitch fraction and polydimethysilane. The precursor containing about 26 wt% Si was melt spun into fibres and then oxidatively cured in air to render the fibres infusible. The cured fibres were pyrolysed at 1200°C under inert atmosphere to produce carbon-silicon alloy (CSA) fibres. The oxidation behaviour is improved...
Naphthalene-based mesophase ribbon fibres were studied in the present work. The fibres were surface treated in a plasma reactor and their mechanical and surface characteristics determined before and after the surface oxidation. The dispersive and non-dispersive components of the surface energy were obtained by contact angle measurements using a tensiometric method, and the surface oxygen content...
Sterling FT carbon black was oxidized in a cool oxygen plasma to various burn-off degrees ranging between 6 and 84%. Plasma-treated samples were characterized by nitrogen and carbon dioxide adsorption, scanning electron microscopy and contact angle measurements. Following the oxygen plasma treatment no changes in BET surface area or porosity were detected. SEM examinations evidenced an absence...
Furnace and acetylene blacks were oxidized with nitric acid in order to obtain some insight into the mechanism of oxidative degradation of carbon blacks. Changes in the pore and crystallographic structures of the carbon blacks in the course of oxidation were examined by nitrogen adsorption, X-ray diffraction, scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). A furnace...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.