Activation de la tourbe de sphaigne par le dioxyde de carbone et agglomération du charbon actif produit

The physical activation of peat moss using CO₂ has been investigated with respect to the operational variables and the characteristics of the active carbon produced. Peat coke is produced during carbonisation with a 30% yield. The activated carbon accounts for 25% of the initial air dried peat moss. Analysis of the active carbon has revealed a surface area up to 600 m²/g and a chemical reactivity similar to commercial active carbon as measured by the iodine, phenazone and phenol indexes. The active carbon thus produced is a powdered material, with a weak abrasive resistance. Agglomeration of the carbon and subsequent pelletization has been done with ammonium ligno-sulfonate, water, and the application of pressure. Resistant pellets can be obtained using 15–20% lignosulfonate and 3000 psi.     

Activation de la tourbe de sphaigne par le dioxyde de carbone et agglomération du charbon actif produit

The physical activation of peat moss using CO₂ has been investigated with respect to the operational variables and the characteristics of the active carbon produced. Peat coke is produced during carbonisation with a 30% yield. The activated carbon accounts for 25% of the initial air dried peat moss. Analysis of the active carbon has revealed a surface area up to 600 m²/g and a chemical reactivity similar to commercial active carbon as measured by the iodine, phenazone and phenol indexes. The active carbon thus produced is a powdered material, with a weak abrasive resistance. Agglomeration of the carbon and subsequent pelletization has been done with ammonium ligno-sulfonate, water, and the application of pressure. Resistant pellets can be obtained using 15-20% lignosulfonate and 3000 psi.     

Etude de la reaction du gaz carbonique avec le carbone aux temperatures elevees et sous de basses pressions

In order to complete and to determine more precisely previous data a new investigation on the kinetics of the C + CO₂ reaction has been carried out over a broader range of temperature (800–2000°C) and pressure (between 10^?4 and 10^?1Torr) with an improved apparatus and using more varied carbon samples. All types of carbons exhibit the same peculiarities in kinetics related to changes in the intrinsic reactivity of the surface. The general features of the kinetics are more similar than hitherto believed to those of the C + O₂ reaction. Indeed, the two reactions differ only in their absolute rates. This difference is discussed on the basis of the mechanism previously proposed by Duval.     

Theory of “Cohesive” vs “Adhesive” Separation in an Adhering System

It is shown that there is limited validitity to the doctrine that true interfacial separation, in an adhering system, is highly improbable. An analysis employing the Griffith-Irwin crack theory yields these results: The important parameters are, difference in elastic moduli, ΔE; differences in g, the energy dissipation per unit crack extension; thickness, Δ₁ or δ₂, of the region where dissipation occurs; and the presence or absence of strong interfacial bonds. If the forces across the interface are appreciably weaker than the cohesive forces in either phase, there is a strong minimum in g at the interface. For flaws of equal size, an interfacial flaw will be the site of initiation of failure. If strong interfacial bonds are present, then if Δg and ΔE have the same sign, failure is most probable, deep within one phase. If Δg and ΔE have opposite signs, failure may be initiated, and may propagate, at a distance δ from the interface, in the phase with lower g. This may be mistaken for weak-boundary layer failure.     

“HETEROGENIZING” HOMOGENEOUS CATALYSTS

For many years, it has been customary to classify catalysts as “homogeneous” or “heterogeneous.” The former commonly operate through the formation of “intermediate compounds,” and the latter, by adsorption of the reactants on the catalyst surface. The line between the two is a fine one, for the distinction between adsorption and compound formation is not at all clear, and seems to be becoming less and less clear as we learn more about adsorption. In recent years, several writers [l-7] have stressed the point that there is a good deal of overlap between homogeneous and heterogeneous catalysis. Experimental evidence supporting this point of view is accumulating, and while we are not prepared to say that there is no distinction, we can say with certainty that many homogeneous catalysts can be converted into heterogeneous ones, retaining the advantages of great activity and selectivity inherent in homogeneity and, at the same time, assuming the ready recovery which is the great advantage of heterogenity. In practice, of course, the matter is not quite that simple, for other factors must be considered. On the whole, however, many advantages have been found in the use of heterogenized homogeneous catalysts.     

Toward “Rubbery” nanoparticles

The synthesis of electrically Conducting Natural Rubber (CNR) nanoparticles from natural rubber (cis 1, 4 polyisoprene) by a simple chemical doping technique is reported for the first time. Much before the establishment of conjugation as a precondition for polymers to be conducting a typical nonconjugated polymer like cis 1,4 polyisoprene was shown to develop intrinsic conductivity on doping. However, the possibility of developing conducting nanoparticles of natural rubber by doping has never been explored. Doping of natural rubber solution with Antimony pentchloride is found to lead to the formation of nanosized rubber particles with improved thermal stability and lower degradation characteristics than that of pristine rubber. Transmission electron microscopy and Dynamic Light Scattering experiments revealed a highly uniform dispersion of the particles with sizes in the range of 4 nm. The doped nanoparticles are found to retain “rubbery” properties of natural rubber and therefore these can be rightly termed as Rubber Nano particles. The development of nanoparticles of rubber assumes great significance in that it would lead to hitherto unknown applications for natural rubber in micro applications‐like sensors, and optoelectronics devices to macro applications such as compatible reinforcing fillers for elastomers and plastics to replace conventional fillers like carbon particles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Corréation entre la stabilité colloïdale de la matière première et le degré de dispersion du noir de carbone

The evolution of carbon black technology allows, at present, various hydrocarbon products as fillers in complex mixtures. The fillers investigated in this work are made of a blend of five products from different origins. The objective of this work is the study of the correlation between the colloidal stability of the filler and the quality of the carbon black, as well as the relation between the degree of dispersity of the carbon black and the resin tensile strength.