Atomistic Scale Analysis of the Formation of Multi-Member Rings for Pan-Based Carbon Fibers Manufacturing with Reaxff

Abstract

It is crucial to understand the production process of carbon fiber at the atomic scale, including polymerization, oxidation, carbonization, and graphitization. In particular, the polymerization of acrylonitrile (AN) has always been a challenging point, because of the absence of appropriate theoretical guidance, and the experimental trial and error method is employed to determine the best copolymerization reagent. Herein, a ReaxFF potential called CHONSi-2024 appropriate to carbon fiber production process was firstly developed. On the basis of verifying the reliability of the potential, we used the CHONSi-2024 to simulate the low-temperature polymerization reaction of AN and its high-temperature carbonization process, explored different connection modes of AN, explored the formation process of 5-membered rings, 6-membered rings and 7-membered rings, and explored the removal process of some oxygen atoms and nitrogen atoms, and analyzed the final carbon fiber structure. The results reveal that the CHONSi-2024 potential can accurately replicate the complete process of carbon fiber manufacturing, which will provide atomic-level understanding for the upcycling of high-performance carbon fibers.

Keywords: carbon fiber, PAN, ReaxFF, DFT, Gaussian