Technical Report 241, c4e-Preprint Series, Cambridge

Authors: Laura Pascazio, Jacob W. Martin, Kimberly L. Bowal, Jethro Akroyd, and Markus Kraft*

Reference: Technical Report 241, c4e-Preprint Series, Cambridge, 2019

Associated Themes:
 

• Mechanical properties of crosslinked soot are simulated using reactive MD.
• Soot particles are described as 3D networks of crosslinked PAHs.
• Hardness depends primarily on the degree of crosslinking (CL) and core-shell structure.
• Mature soot must contain CL>2 to be consistent with experimental hardness.

The nanoindentation of soot particles is simulated using reactive molecular dynamics to investigate the relationship between the observed mechanical properties and the internal structure of the particles. The particles that are provided as inputs to the simulations are generated using reactive molecular dynamics to create 3D networks of crosslinked coronene, circumanthracene and core-shell mixtures of coronene and circumanthracene. The results of the simulated nanoindentation experiments are analysed as a function of the degree of crosslinking (defined as the number of crosslinks per monomer in the particles), the size and the core-shell structure of the particles. In the case of homogeneous particles (i.e. those without a core-shell structure), the simulations show a unique relationship between the degree of crosslinking (CL) and the simulated hardness, Young's modulus and deformation ratio. In the case of particles with a core-shell structure, a unique relationship was only found by considering the core-shell ratio and the degree of crosslinking in both the core and the shell. Our results coupled with nanoindentation experiments can be used to estimate the degree of crosslinking in soot particles and they show that mature soot must contain crosslinks between its aromatic constituents (CL>2) to be consistent with experimental hardness values.

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