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Preparation and Characterization of PAN-Based High Strengh and High Modulus Carbon Fibers

Author: HanZan
Tutor: ZhangXueJun
School: Beijing University of Chemical Technology
Course: Materials Science and Engineering
Keywords: PAN-based carbon fiber The degree of graphitization Degree of orientation Microstructure parameters
CLC: TQ342.742
Type: Master's thesis
Year: 2011
Downloads: 163
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Abstract

Polyacrylonitrile (PAN)-based high strength and high modulus fiber is an anisotropic reinforcing material. In the graphitization process, the carbon atoms in the carbon fiber rearrangement occurs in the effect of high-temperature field, microscopic structure by the two-dimensional turbostratic structure is converted to the three-dimensional graphite-like structure. The carbon fibers are stacked hexagonal graphite crystallites, the crystallites in the fiber stacking direction first with the fiber axis perpendicular to the graphite level preferential orientation along the fiber axis the orientation degree determines the size of the modulus of the fiber, and therefore the study of carbon fiber a crystallite size, crystallinity and degree of orientation to improve the carbon fiber mechanical properties is essential. This paper by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM). Raman (Raman) spectroscopy and X-ray diffraction (XRD), four characterization methods to study the surface morphology and microstructure of the five kinds of home-made high-strength and high modulus carbon fiber, compared with MJ series carbon fiber Toray T800 carbon fiber. And Japan's Toray T800 carbon fiber as raw material, the performance of different high-strength and high modulus carbon fibers by the different conditions of continuous graphitization treatment, and study the graphitization temperature, graphitization time and drawing rate of graphitization of carbon fiber structure of impact, and graphitization conditions on the mechanical properties and density to determine the optimal process parameters. The results showed that of the SEM and HRTEM, T800, MJ, and home-made surface of the high strength and high modulus carbon fibers are along the fiber axis direction of the trench, in the preparation process of the carbon fibers in less mechanical damage and is not found significant voids, cracks, scratches and other defects. The high strength and high modulus carbon fiber is composed of crystalline and amorphous regions, the the graphite layer arrangement Tacticity order HMCF-5 gt; HMCF-4 gt; HMCF-3 gt; HMCF-gt; HMCF-1. XRD and Raman spectroscopy results showed that larger T800 graphite microcrystalline layer spacing (d002), microcrystalline stuffing thickness (Lc) and a graphite network plane size (La) is the smallest. From HMCF-1 gradually increases to HMCF-5 carbon fibers microcrystalline stuffing thickness and a graphite mesh size of the crystal plane, and the graphite the microcrystalline layer spacing and orientation angle decreases gradually, to gradually increase the degree of orientation and crystallinity. Compared with MJ carbon fibers, the homemade HMCF-4 and HMCF-5 carbon fiber crystallinity, the crystallite size and the degree of preferred orientation greater than M55J, the graphite crystallite interlayer spacing of less than M55J. With the the graphitization temperature rise, peak D and G peaks FWHM decreases, R value is reduced, the degree of graphitization increases. When the the graphitization temperature rises, the size, degree of crystallinity and degree of orientation of graphite crystallites are gradually increased and gradually decreases, while the graphite crystallite interlayer spacing and orientation angle. Draw ratio increases help graphite crystallites along the fiber axis, the orientation angle is reduced, the increase in the degree of preferred orientation, and therefore makes the graphite crystallite interlayer spacing decreases, while the graphite network plane network size in the drafting force. along the fiber axis under the action of stretching. Extended graphitization time graphite net increase in the plane size of the graphite crystallite interlayer spacing decreases. The performance analysis shows that with increasing graphitization temperature of the carbon fibers, the tensile strength were decreased, while the elastic modulus is increased successively. Extended the graphitizing time and raise the temperature of the graphitized carbon fibers will become densified leaving diameter and linear density decreases. The increase of the draw ratio is bound to make the diameter and the line density of the carbon fibers is reduced.

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