Characterization of Thermally Heat-treated Polyacrylonitrile Carbon Fibers

Abstract

This study investigates the graphitization process of polyacrylonitrile (PAN) carbon fibers by subjecting commercial fibers to thermal heat treatment at temperatures ranging from 1400 to 2100 °C in 100 °C increments, using either argon or nitrogen gas atmospheres. Changes in crystallinity, surface morphology, and lattice parameters were analyzed for two commercial carbon fibers using X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. Results indicated minimal changes in surface morphology with increasing heat-treatment temperature; however, crystallinity significantly increased. Crystallinity changes were more strongly dependent on temperature rather than gas atmosphere or fiber type. At intermediate heat-treatment temperatures (1600–1800 °C), fibers treated in argon showed a slight preference for graphitization. The highest level of graphitization was measured at 2100 °C. Crystallite size increased as the intensity ratio of the D1 to G Raman peaks increased, reaching a peak around ~1800 °C, after which the ratio started to decrease. This behavior aligns with Ferrari's three-stage model of carbon crystallization and is consistent with both the Marie-Mering degree of graphitization and Brubaker's Integrated Absolute Differential models, all of which describe the transformation from an amorphous to a more graphitic structure. At the higher heat-treatment temperatures, the changes between atmospheres and fiber types were measured to converge to similar levels of graphitization. This study evaluates the progressive change in commercial grade carbon fibers when heat-treated.

Department(s)

Materials Science and Engineering

Keywords and Phrases

Characterization; Graphitization; Heat-treatment; PAN carbon fibers

International Standard Serial Number (ISSN)

0925-9635

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2025 Elsevier, All rights reserved.

Publication Date

01 Nov 2025

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