Strengthened PAN-based carbon fibers obtained by slow heating rate carbonization.

Min-A Kim,Rodolfo Cruz-Silva,Han-Ik Joh,Morinobu Endo,Syogo Tejima,Dawon Jang,Hwan Chul Kim,Sungho Lee

doi:10.1038/srep22988

Abstract

Large efforts have been made over the last 40 years to increase the mechanical strength of polyacrylonitrile (PAN)-based carbon fibers (CFs) using a variety of chemical or physical protocols. In this paper, we report a new method to increase CFs mechanical strength using a slow heating rate during the carbonization process. This new approach increases both the carbon sp3 bonding and the number of nitrogen atoms with quaternary bonding in the hexagonal carbon network. Theoretical calculations support a crosslinking model promoted by the interstitial carbon atoms located in the graphitic interlayer spaces. The improvement in mechanical performance by a controlled crosslinking between the carbon hexagonal layers of the PAN based CFs is a new concept that can contribute further in the tailoring of CFs performance based on the understanding of their microstructure down to the atomic scale.

Highlights

Extensive research of PAN-based carbon fibers (CFs) has focused on developing new precursors and modifying the process of stabilization and carbonization in order to control and to maximize their mechanical performance[1,2,3,4]
The structural information shows that different ultimate carbonization temperatures and heating rates did not affect the microstructure of the resulting CFs
We found that nitrogen atoms with quaternary bonding in the hexagonal carbon networks and sp[3] bonding clearly increased the tensile strength performance of the CFs

Summary

Introduction

Extensive research of PAN-based carbon fibers (CFs) has focused on developing new precursors and modifying the process of stabilization and carbonization in order to control and to maximize their mechanical performance[1,2,3,4]. We carried out MD simulations to understand the role of nitrogen species and modeled the carbon sp[3] structure We found that both the sp[3] hybridized carbon and especially the quaternary nitrogen atoms have a strong effect on the tensile strength of the fibers. Interstitial sp[3] carbons with the aid of the interlayer forces, which are enhanced by the neighboring quaternary nitrogen at the bonding site This model of carbon microstructure is a new concept in the high-strength CF research field. This research is expected to contribute significantly to the production of carbon fiber for high performance products

Methods

Results

Conclusion