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The microstructure and morphology of carbon black: A study using small angle neutron scattering and contrast variation

Published online by Cambridge University Press:  03 March 2011

Rex P. Hjelm Jr.*
Affiliation:
Los Alamos Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545-1663
Wesley A. Wampler
Affiliation:
Sid Richardson Carbon Company, 4825 North Freeway, Fort Worth, Texas 76106
Philip A. Seeger
Affiliation:
Los Alamos Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545-1663
Michel Gerspacher
Affiliation:
Sid Richardson Carbon Company, 4825 North Freeway, Fort Worth, Texas 76106
*
a)Address all correspondence to this author.
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Abstract

This is a study of the form and structure of particles and particle aggregates of an experimental high surface area carbon black (HSA) using small-angle neutron scattering and the method of contrast variation. Contrast variation was effected by studying suspensions of the carbon black in cyclohexane containing different fractions of deuterocyclohexane. We find that the approximately 29 nm diameter USA particles are arranged as small, linear aggregates with an average aggregation number between 4 and 6. The structure averaged over the particle population is best represented by a prolate ellipsoid of revolution with semiaxes 14.5 and 76.4 nm. The surface of the aggregates appears smooth over length scales larger than 1 nm, which places an upper limit on the surface roughness observed by other methods. The internal structure of the aggregates is described by a shell-core model, with the shell density being consistent with a graphitic structure and the core being of lower density, more like amorphous carbon. Some fraction of the core volume (0.1 to 0.2) is taken up by voids that are not accessible to the solvent. An estimate of the shell thickness gives 1 to 2 nm along the ellipsoid minor axis and 6 to 10 nm along the major axis. The particles of the aggregate appear to be fused so that the less dense amorphous core is continuous through the inner parts of the aggregate. The information that can be obtained on the internal structure using contrast variation is limited by heterogeneity in the chemical composition of carbon black aggregates.

Type
Articles
Copyright
Copyright © Materials Research Society 1994

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References

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