Structure Of Carbon Black Particles Research Articles

High pressure Raman and neutron scattering study on structure of carbon black particles

High pressure Raman and neutron scattering study of carbon blacks and highly oriented pyrolytic graphite is reported. It is found that carbon black particles are composed of graphitic nanocrystallites and amorphous carbon. Pressure-induced order in inter-atomic distances within nanocrystallites is completely reversible. Relative concentration of amorphous carbon decreases slightly with increased pressure. This process differs from temperature induced transformation of amorphous carbon into ordered carbon. Post-production treatment at high temperatures results in lateral and vertical growth of graphitic crystallites, and at sufficiently high temperatures almost all amorphous carbon is transformed into graphitic structures. Within the pressure range under study, 5 GPa, only a small fraction of amorphous carbon is transformed into ordered structures. Pressure induced frequency shift of the E 2g bands of various carbon blacks is explained in terms of a modified intermolecular potential.

Spectral properties of carbon black

The internal structure of carbon black particles considerably influences the optical behavior of the material, apart from the shape and agglomeration state of the primary particles. In this paper the correlation between internal structure and spectral behavior of carbon black is investigated experimentally. The carbon blacks were produced by resistive heating of graphite electrodes and condensation in a cooling gas atmosphere. The internal structure of the primary carbon black particles was investigated by high-resolution transmission electron microscopy, electron energy loss spectroscopy, 13 C NMR spectroscopy, and Raman spectroscopy. The primary particles were found to consist of bent or plane structural subunits. The UV π−π * absorption feature of the produced carbon blacks varies in position between 196 and 265 nm depending on the state of bending of the graphene layers in the subunits of particles and/or the dimensions of the plane graphitic microcrystallites and the incorporation of hydrogen. The different curvature radii of the graphene layers or the sizes of microcrystallites can be summarized by an integral dimension like the ratio of sp 2/sp 3 hybridized carbon atoms. In the mid-infrared spectral region, the absolute value of the absorption coefficient κ is dominated by a continuous absorption due to free charge carriers which are also influenced by the ratio of sp 2/sp 3 hybridized carbon in the primary particles. The appearance of prominent bands is related to the existence of functional groups, like C–H n , CO and/or C–O–C.

The Effects of Heating and Cooling Rates on the Structure of Carbon Black Particles

Abstract The effects of heating and cooling rates on the structure of N660 and N299 carbon black particles have been investigated using Raman spectroscopy, X-ray scattering, and the BET technique. Carbon blacks were kept at 2700 K for various lengths of time and next cooled down at different rates. The size of crystallites and the surface roughness of the particles have been determined for these different treatment schedules. The fractal dimension decreases from 2.2 for untreated samples to 2.0 for samples heat treated to 1300 K. Cooling rates do not affect the surface roughness. However, rapid cooling reduces crystallite sizes. We postulate that the surface of carbon particles is composed of crystallites and amorphous carbon. The amount of amorphous carbon depends on the thermal treatment. The role of amorphous carbon in determining reinforcing properties of carbon blacks in tires is discussed.

Surface fractal dimension of graphitized carbon black particles

Fractal analysis of adsorption isotherms is used to study the surface roughness of carbon blacks graphitized at 3000 K. Gases of various molecular sizes (nitrogen, argon, ethane, propane, and butane) are adsorbed on different grades of carbon black. Using the molecular yardstick method, it is found that the surface fractal dimension of graphitized carbon black is 2.0 ± 0.1 and is independent of carbon black grade. Another approach, the FHH method, was also used. But the slopes of the FHH plots are sensitive to the forces responsible for adsorption and thus they cannot give the fractal dimension of carbon blacks. Direct imaging of surface structure of carbon black particles carried out using atomic force microscopy (AFM) confirmed that the surface of graphitized carbon black particles exhibits a low degree of irregularity on the atomic scale.