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Submicronic powders containing carbon, boron and nitrogen have been prepared by thermal chemical vapour deposition. The precursors of carbon, boron and nitrogen are acetylene, boron trichloride and ammonia, respectively. Hydrogen is the carrier gas. The conditions of preparation of these powders are rather different from those of thin films containing the same elements. Using X-ray photoelectron spectroscopy...
In order to characterize C/C composites during consumption and to document a carbon–carbon oxidation model, specific oxidation experimental facilities were developed. Two different devices of a BLOx (Bench Laser for Oxidation) feature were designed according to the atmosphere (molecular air, oxygen, water vapor). These facilities enable high-temperature material characterization to be performed in...
It was shown that the low weight loss makes the polyimide resins based on acetyl derivatives of aromatic diamines a promising candidate for carbon–carbon composites. The weight loss of this polyimide resin can reach about 30% in the composite, which is 1.5 times lower than that of the phenol-formaldehyde resin. It is suggested that the lower weight loss of the matrix in carbon fiber reinforced polyimide...
Activated carbons with degrees of burn-off ranging from 12 wt.% to 60 wt.% have been prepared from toluene-insoluble (T.I.) fractions of a heat-treated A240 petroleum pitch. After toluene fractionation, the resulting pitches have been stabilized, carbonized and then activated using carbon dioxide at 1173 K. Characterization by high pressure carbon dioxide adsorption has been performed in order to...
The purpose of the work reported here is to give carbon black with a high functional surface, especially for use in fuel cell oxygen electrodes. The authors have investigated the surface properties, such as wettability, rate constant of H 2 O 2 decomposition, and surface functional groups, of surface modified carbon black by low temperature oxygen plasma. This work also describes the...
In order to clarify the reason why boron-substituted disordered carbons can store more Li atoms than pristine carbons, we employed several polyaromatic hydrocarbons as model clusters for disordered carbons and investigated the effect of boron and nitrogen substitutions on the stable structures and electronic properties of model clusters, by using a semiempirical molecular orbital method. Boron substitution...
In this part a numerical model for the oxidation of C/C composites is developed. It takes into account the morphological and the reactivity results determined in part I and II, respectively. The prediction ability of this model has been checked for different types of composites oxidized in different atmospheres and generally the trends of the experimental reaction curves are relatively well followed...
The role played by surfactant molecular architecture in determining its effectiveness as a dispersant for carbonaceous solid substrates in hydrocarbon solvents is investigated using simple analytic theory and adsorption experiments carried out with model and commercial succinimides on activated carbon. We show by both of these approaches that the length and backbone structure of the hydrophobic tail...
A technique is presented for semi-quantitative digital analysis of 002 lattice fringe images of carbon materials. The automated technique yields statistics on fringe length and tortuosity, as well as new quantitative parameters describing the mode, degree, and length scale of orientational order among graphene layers. The technique is applied to combustion-derived carbons with special emphasis on...
Thin films of carbon were deposited on single crystal silicon and quartz substrates by simple ion beam sputtering of camphoric carbon target, obtained from camphor: a natural source, at room temperature. The as-deposited films were heat treated at different temperatures and the effects of heat treatment on structural modifications were studied in detail by Raman spectroscopy through the evolution...
We investigate here a modification of the discrete random pore model [Bhatia SK, Vartak BJ, Carbon 1996;34:1383], by including an additional rate constant which takes into account the different reactivity of the initial pore surface having attached functional groups and hydrogens, relative to the subsequently exposed surface. It is observed that the relative initial reactivity has a significant effect...
A new method was presented to prepare activated carbon fiber with high bulk density (HD-ACF) without using any binders. The method consists of the hot briquetting of stabilized fiber and subsequent carbonization and activation of the fiber. The stabilization level of the stabilized fiber usable in this method must be higher than that of ordinary stabilized fibers, but neither any other processes like...
A new type of carbon nanotubes prepared by catalytic decomposition of CH 4 (CH 4 -CNT) was studied and compared with carbon nanotubes derived from CO-disproportionation (CO-CNT) and graphite. HRTEM observation reveals that the structural graphene sheets are in a conical hollow shape for CH 4 -CNT but in a cylindrical shape for CO-CNT. The valence band structure of CH 4...
A model of the oxidation behaviour of C/C composites was developed. The purpose of the model is to predict the carbon loss that occurs at the outer surface and within the porosity of the composite. It takes into account the transport of species in the material, chemical gas–gas and gas–solid reactions, the interaction of both transport phenomena and chemistry, the morphological parameters of the unoxidized...
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