Peering into the structural evolution of glass-like carbons derived from phenolic resin by combining small-angle neutron scattering with an advanced evaluation method for wide-angle X-ray scattering

Abstract

The structural evolution of two non-graphitizing glass-like carbons derived from a liquid resole and a solid novolac-type phenolic resin was quantitatively characterized by combining small-angle neutron scattering (SANS) with an advanced evaluation for wide-angle X-ray scattering (WAXS) data. Utilizing these two methods allowed for studying the microstructure on the Ångstrom level (graphene stacks, WAXS) and the inaccessible microporosity (SANS). The applied WAXS analysis provided quantitative structural parameters for both, size and disorder in the polyaromatic sp2 microstructure. Hence, the combined SANS-WAXS analysis yielded comprehensive insights into the relation between the graphene microstructure and the inaccessible porosity upon heat treatment for glass-like carbons, i.e. a non-graphitizing class of carbon. In particular, the analogue investigation of a graphitizing mesophase pitch demonstrates the major impact of the chemical composition of the utilized carbon precursor. For the glass-like carbons the results revealed different growth rates for the lateral extent of the basic structural units (La) depending on the temperature range, finally reaching 12 nm, whereas the stack height (Lc) exhibiting 2.2 nm is hardly affected by the thermal processing up to 3000 °C. As a major finding our study thus relates the evolution of microstructure and porosity to changes in chemical composition.