Graphitization of a high-sulfur mesophase pitch-based fiber

• Published in: Carbon (New York) 1993, Vol.31 (2), p.303-313
• Main Authors: Rogers, D.K., Jones, S.P., Fain, C.C., Edie, D.D.
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic and carbon fibers; Ceramic industries; Chemical industry and chemicals; Exact sciences and technology; fiber; Graphitiziation; mesophase; puffing; sulfur; Technical ceramics
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/0008-6223(93)90035-9

Graphitization of high-sulfur content mesophase pitch fibers is complicated by the evolution of sulfur-bearing gases at high temperatures. Removal of these gases leads to appreciable strain and crystal misorientation if large structural units are present. The most obvious result of gas removal is “puffing,” an increase in the fiber cross-sectional area, accompanied by a decrease in lattice-dependent properties such as elastic modulus and conductivity. In this study, the effect of sulfur removal on fiber crystal structure is addressed. X-ray diffraction and differential scanning calorimetry are used to characterize the structure resulting from various heating rates, maximum temperatures, and dwell times. High heating rates during the sulfur removal period (from 1600 to 2000°C) were found to lessen the severity of fiber damage. When followed with a slow, high-temperature annealing treatment, a well-ordered graphitic structure was produced. Finally, a heat treatment strategy is outlined to improve the elastic properties of fibers produced from a high sulfur content mesophase.