Carbon
Nanometric graphitic structures (fullerenes, nanotubes, bucky-onions, etc.) form in different harsh environments (electric arc, electron irradiation, plasma torch). In particular, the onion-like graphitic particles may display a wide range of structures, going from polyhedral to nearly spherical. High-resolution electron microscopy is the primary tool for studying these systems. On the basis of...
Encapsulation of foreign materials within a hollow graphitic cage was carried out for rare-earth and iron-group metals by using an electric arc discharge. The rare-earth metals with low vapor pressures, Sc, Y, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, and Lu, were encapsulated in the form of carbides, whereas volatile Sm, Eu, and Yb metals were not. For iron-group metals, particles in metallic phases...
Graphite intercalation compounds were prepared from flakes of natural graphite and Thornel P-120 carbon fibers. Stage 2 compounds were obtained with TaCl 5 at 400°C, and stage 4 compounds with NbCl 5 at 200 C. The compounds with TaCl 5 were stable in ambient air or under water at 25°C. At 90°C with water or dilute hydrochloric acid small quantities of the stage 3 compound appeared...
The mechanical properties of binderless carbon moulds produced from the preheat-treated mesophase pitch of controlled grain sizes were investigated. The particular mesophase pitch catalytically synthesized from pure naphthalene with HF/BF 3 was properly preheat-treated at 753 K for 2 hours and then ground by a jet-mill into grains of different sizes. These grains were moulded at room temperature...
Non-planar morphologies observed in the reaction front of carbon fibers or interphases receding into a ceramic matrix have been analyzed. A numerical simulation was used to evaluate the parameters which control the morphology of the receding carbon reaction front. The study has indicated that in addition to influencing the recession kinetics, the morphology of the reaction front contains information...
The influence of structural characteristics, in particular heteroatom content, on the ammoniatreatment of carbon-13 materials has been studied. The resulting carbon-13 materials were investigated for their temperature-programmed combustion characteristics by thermogravimetric analysis-mass spectrometry (TG-MS). The use of ca 99% isotopically pure carbon-13 allowed the analysis of N 2 O and...
This paper is concerned with the role of carbon fibre coatings in the production of carbon fibre-reinforced carbons from high tenacity (HT) carbon fibres and phenolic resin as a matrix precursor. In order to reduce the adhesion of the matrix to the carbon fibre surface, various HT carbon fibres were coated with polyldimethylsiloxane) and poly(methylphenylsiloxane) using solutions of these materials...
Commercially surface-treated HT carbon fibres were coated with phenolic resin in order to reduce the adhesion of the phenolic resin matrix to the fibre surface. Unidirectional (UD) composites were fabricated using uncoated and coated fibres and a standard phenolic resin as matrix: the fibre volume fraction of the green composites was 60 vol%. The composites were carbonized at 1000 C and treated at...
Ceramic coatings were prepared on the surface of carbon composites, using a process simpler than the ones presently known. The solid precursor is deposited on the substrate from a suspension, then submitted to heat treatment under controlled atmosphere.Owing to their good thermomechanical properties, β′-SiAlONs have been chosen as the coating agent. They were prepared by a low temperature process...
Isotopic steady-state and step-response (SR) experiments have been performed with calcium containing carbon samples with different metal content and sintering degree. The SR results: (i) rule out the CaO 2 /CaO mechanism; (ii) support the mechanism for the CO 2 -carbon gasification catalyzed by calcium previously proposed, confirming that CaCO 3 is the active species; (iii)...
Micro-coiled carbon libers were vapor phase prepared using the catalytic pyrolysis of acetylene in the presence of a metal powder catalyst and a small amount of phosphorus impurity. Growth conditions and morphology of the obtained coiled carbon Obers were examined. Among the transition metal powders used, nickel was the most effective lor the growth of the coiled carbon fibers and the maximum coil...
Preparation of an activated carbon fiber containing mesopores was attempted by catalytic activation using cobalt. Phenolic resin and cobalt-acetylacetonate were mixed intimately, spun, cured, carbonized at 900 C in nitrogen and finally activated at 750 900 C in steam. The carbon fibers with the cobalt contents of 38 ppm and 100 ppm were prepared together with a fiber without cobalt as a reference...
Yield, structure, and properties of nitrogen containing pitches prepared catalytically from isoquinoline by the use of AlCl 3 -co-catalyst(nitroethane. nitobenzene) system were studied to increase the yield and nitrogen content of such pitches as a precursor for speciality carbon. Nitroethane(NE) and nitrobenzene(NB) as the co-catalyst increased the yield of the pitch up to 52% compared to...
The NO x were adsorbed into a char bed and then reduced by the microwaves to nitrogen and carbon oxides. High removal rates of NO X -near 98% were observed in laboratory tests. A series of experiments were conducted to find the effect that microwave-induced regeneration of NO X saturated char had on the NO X adsorption capacity of char and the resulting adsorption rate...
For the first time. lattice imperfections in a range of Du Pont mesophase pitch-based fibres have been determined quantitatively from TEM micrographs by the techniques of image analysis. Following the analysis of dark-field and lattice-fringe images, new parameters which quantify lattice imperfections have been introduced, namely a crystallite imperfection factor (I c ) and lattice tortuosity...
Three series of activated carbon have been prepared by heat treatment of peach stones impregnated with solutions of phosphoric acid, in order to analyze the effect of phosphoric acid on the yield, bulk density and porosity of the resultant activated carbons. The analysis of the adsorption isotherms of N 2 at 77 K. CO 2 at 273 K and n-C 4 H 10 , at 273 K shows that the...