A small-angle neutron scattering study of the structure of graphitized carbon black aggregates in Triton X-100/water solutions

Abstract

The structure of graphitized carbon black (CB) aggregates dispersed in water solutions with a non-ionic surfactant are studied by small-angle neutron scattering using contrast variation by heavy/light water mixing. The addition of CB to Triton X-100/water mixtures shifts the critical micelle concentration to a lower value. The CB aggregates have a fractal structure and the apparent fractal dimension is lower near the match point (75% heavy water). The scattering data are modelled using fractal-like aggregates (CB + surfactant), and voids in the CB particles and micelles. The data are fitted simultaneously for three different contrasts. The fractal dimension is found to be larger than 3 with the maximum size of the fractal aggregate being around 150–200Å. The primary CB particles have a broad size distribution with an average size of about 30–80Å. The surfactant coverage of the CB particles is 8% and is constant with varying CB and surfactant concentration. The volume fraction of the voids does not exceed 1% of the CB. The micelle structure is found to be the same as in surfactant/water solutions.