Local structure analysis and modeling of lignin-based carbon composites through the hierarchical decomposition of the radial distribution function

Authors: KIZZIRE, DAYTON - University Of Tennessee; Garcia-Negron, Valerie; HARPER, DAVID - University Of Tennessee; KEFFER, DAVID - University Of Tennessee

Submitted to: ChemistryOpen
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2021
Publication Date: 2/17/2022
Citation: Kizzire, D.G., Garcia-Negron, V., Harper, D.P., Keffer, D.J. 2022. Local structure analysis and modeling of lignin-based carbon composites through the hierarchical decomposition of the radial distribution function. ChemistryOpen. https://doi.org/10.1002/open.202100220.
DOI: https://doi.org/10.1002/open.202100220

Interpretive Summary: Lignin, a complex polymer that comes from woody plants and grasses, was heat treated to produce carbonaceous materials. The structure of these materials can be tuned for carbon-based applications via carbonization temperatures. Due to the variability of lignins' composition, the Processing-Structure-Property-Performance relationships are difficult to define. This work compares the structure of different lignin-based carbon composites treated at different temperatures and creates a physic-based model to estimate composite density, crystalline volume fraction, and crystallite size. The HDRDF software was developed for rapid modeling and understanding of the local structure of complex composite materials of arbitrary domain geometries. HDRDF requires a low computational cost reducing runtimes up to five orders of magnitude compared to molecular dynamics simulations of lignin-based carbon composites.

Technical Abstract: Carbonized lignin has been proposed as a sustainable and domestic source of amorphous, graphitic, and nanostructured carbon for many research and industrial applications since the nanostructure can be tuned through carbonization temperature. However, due to the variability of lignin and its monomeric units, Process-Structure-Property-Performance (PSPP) relationships are often hard to define. In this work, radial distribution functions from synchrotron x-ray and neutron scattering of lignin-based carbon composites (LBCCs) are investigated to characterize the local atomic environment and develop PSPP relationships. Analysis of the radial distribution functions (RDFs) and development of PSPP relationships are aided by modeling with the Hierarchical Decomposition of the Radial Distribution Function (HDRDF) where the RDF is modeled through a combination of static atomic structures and continuous mesoscale objects. PSPP relationships for LBCCs defined by this work and HDRDF include increasing crystalline volume fraction, nanoscale composite density, and crystallite size with increasing reduction temperature.