Microstructure of Carbon Blacks

Mechanisms of carbon black formation must account for the experimental observations of the unique morphology and microstructure of carbon black. These include the presence of nodules, or particles, multiple growth centers within some nodules, the fusion of nodules into large aggregates, and the paracrystalline or concentric layer plane structure of the aggregates. It is generally accepted that the mechanism of formation involves a series of stages as follows ... 

Carbon blacks are promising electrode materials due to their relatively high activities and long lifetimes in contrast to the lower activity or rapid deactivation of the other carbonaceous materials [16-20]. These catalytic characteristics of carbon blacks are attributed to their microstructure that has many active sites consisting of edges and defects in nanosized graphitic layers [19-21]. 

The electrical conductivity of two-phase, incompatible polymer blends containing carbon black has been shown to depend on the relative affinity of the conductive particles to each of the polymer components in the blend, the concentration of carbon black in the filler-rich phase, and the structural continuity of this phase [82]. Hence, by judicious manipulation of the phase microstructure, these three-phase filled composites can exhibit double percolation behaviour. 

The Brunaurer Emmett Teller specific surface area (BET SSA) of carbon black is influenced by the size, the porosity, and the surface microstructure of the primary particles. Surface heterogeneities given by graphitic planes at the surface, amorphous carbon, crystallite edges, and slit-shaped cavities representing adsorption sites of different energies describe the surface microstructure. 

Other recent work (Hess and Herd, 1993) on the microstructure of carbon blac] confirmed earlier findings (Medalia and Rivin, 1976) that the particles of some pa graphitized blacks are composed of hollow graphitic shells. Thus, voids are fom the interior of the particles and agglomerates as a result of localized densificatioi... 

This work investigates the behaviour of elastomeric chains (polybutadienes of identical molecular weight but different microstructures) in the close vicinity of carbon black surfaces in order to attain a better understanding of the structure and properties of interphases. Elastomer-filler interactions are assessed through the study of the thermal properties and NMR relaxation characteristics of the corresponding materials. MAS solid-state NMR provides information on the effect exerted by polymer-filler interactions on the mobility of the various constitutive species of the macromolecular backbone. 

Studies of carbon blacks by high resolution electron microscopy have also provided new insight into their microstructure, i.e., the internal morphology of the primary particles (6). The original view, developed... 

Another aspect of microstructure in carbon black is microporosity. Microporosity can be detected by a number of surface chemical techniques which discriminate against small pores (26-28). It is normally not an important factor in commercial furnace blacks. De Boer and associates have suggested that the pores in carbon black are slits arising from missing layer planes (29, 3i). Their width, therefore, is given by... 

Ban, L. L., Hess, VV. M. Current progress in the study of carbon black microstructure and general morphology. In Renforcement des elastomeres (J.-B. Donnet, ed.) p. 81, Paris. CNRS 1975... 

Carbon Black is formed from the burning of gaseous or liquid hydrocarbons under conditions of restricted air access. According to electron micrographs taken with a phase contrast microscope, carbon black has a graphitelike microstructure with lattice distances of 0.35 nm. The layers lie parallel to the particle surface. Since discrete crystalline regions cannot be observed, the structure of carbon black is better described in terms of a paracrystalline state rather than a random distribution of graphite crystals. 

The behavior of carbon black-filled rubber in relation to quasi-static and dynamic responses is examined in detail. In particular, the main feamres of the microstructure of the material and their influence on the macro-mechanical response are highlighted. The effects of strain, strain-rate and temperature on the constitutive response are discussed. Mullins and Pa5me effects, which are peculiar in the behavior of filled elastomers, are reviewed and new results are shown. 

P.A. Marsh, A. Voet, T.J. Mullens, L.D. Price. Quantitiative micrography of carbon black microstructure. Carbon, 9, 797-805,1971. 

Table 2.7 lists techniques used to characterise carbon-blacks. Analysis of CB in rubber vulcanisates requires recovery of CB by digestion of the matrix followed by filtration, or by nonoxidative pyrolysis. Dispersion of CB within rubber products is usually assessed by the Cabot dispersion test, or by means of TEM. Kruse [46] has reviewed rubber microscopy, including the determination of the microstructure of CB in rubber compounds and vulcanisates and their qualitative and quantitative determination. Analysis of free CB features measurements of (i) particulate and aggregate size (SEM, TEM, XRD, AFM, STM) (ii) total surface area according to the BET method (ISO 4652), iodine adsorption (ISO 1304) or cetyltrimethylammonium bromide (CTAB) adsorption (ASTM D 3765) and (iii) external surface area, according to the dibutylphthalate (DBP) test (ASTM D 2414). TGA is an excellent technique for the quantification of CB in rubbers. However, it is very limited in being able to distinguish the different types of... 

The enormous importance of carbon in such diverse fields as inorganic and organic chemistry and biology is well known however, only the aspects of carbon relevant to catalysis will be described here. The main topics we are concerned with are porous activated carbons, carbon black as catalyst supports and forms of coking. Carbon is also currently used as storage for natural gas and to clean up radioactive contamination. Carbon is available at low cost and a vast literature exists on its uses. Coal-derived carbon is made from biomass, wood or fossil plants and its microstructure differs from carbon made from industrial coke. Activated carbons are synthesized by thermal activation or by chemical activation to provide desirable properties like high surface area. 

---