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SKIN-CORE STRUCTURE IN MESOPHASE PITCH-BASED CARBON FIBERS: CAUSES AND PREVENTION

ע⣺ՓCarbon, Vol. 36, No. 12, pp. 1719C1724, 1998l
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YONG-GEN LU() ,a,* DONG WU,b QING-FANG ZHA,a LANG LIU a and
CHANG-LING YANGa
aInstitute of Coal Chemistry, Chinese Academy of Sciences, Shanxi, 030001 Taiyuan,
People's Republic of China
bDepartment of Chemical Engineering, Taiyuan University of Science and Technology, Shanxi,
030001 Taiyuan, People's Republic of China


Abstract:To prohibit skin-core structure from appearing in mesophase pitch based carbon fiber (CF) with a large diameter (30C50 mm), measures such as decreasing oxidation temperature, prolonging holding time and increasing the oxygen partial pressure in the oxidative atmosphere were taken. EPMA (electron probe X-ray micro-analyzer) was utilized to detect the oxygen content distribution along the diameter of oxidized pitch fiber (OF). The transverse structure of OFs and CFs was observed under a scanning electron microscope (SEM). It was found with certainty that the skin-core structure in CFs is caused by steep oxygen content gradient along the diameter of their OFs. The oxygen distribution in
OFs was controlled by the oxidative stabilization conditions. In this work, the CF whose precursor fiber had been oxidized at 240C in a flow of pure oxygen for 10 hours exhibits no skin-core structure and possesses a high tensile strength. The kinetics of stabilization was also studied. It can be concluded that those factors which increase oxygen diffusion or depress oxidative reaction are effective in overcoming skin-core structure in CFs. ? 1998 Elsevier Science Ltd. All rights reserved.
Key words:A. Carbon fibers, mesphase, B. EPMA, D. Diffusion.

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