Microscopy characterization and evaluation method of homogeneity of carbon fibers

Abstract

The invention aims to provide a microscopy characterization and evaluation method of homogeneity of carbon fibers. The method has the advantages that the homogeneity of a carbon fiber structure can be systematically evaluated, the method is not limited by the structures of the carbon fiber products of different diameters, different densities, different batches and different corporations, meanwhile, a condition that the carbon fibers are high modulus or high strength carbon fibers is not distinguished, and a simple, convenient and feasible evaluation standard is provided for evaluating the homogeneity of the carbon fiber structure in a qualitative manner. The evaluation method comprises the following specific steps of collecting an axially horizontal slice sample of carbon fibers, and collecting a series of continuous selected area electron diffraction (SAED) patterns on slices the sizes of which are same with the longitudinal sections of the carbon fibers by using a transmission electron microscope; respectively reading diffracted intensity values of the positions (0002) of the periphery along each diffraction arc to obtain a preferred orientation angle OA map, wherein the preferred orientation angle directly corresponds to the arrangement orientation degree of a (0002) carbon atom layer of the carbon fibers; accurately and quantitatively characterizing a texture degree of the carbon fibers by using the orientation angle.

Description

technical field [0001] The invention relates to a method for characterizing and evaluating the radial structural uniformity of carbon fibers, which is suitable for polyacrylonitrile (PAN)-based carbon fibers of any different precursors, and can qualitatively represent the change of structural uniformity along the radial direction of the fiber. Background technique [0002] Carbon fiber is a fibrous carbon material with a carbon content of more than 90%. It is made by pyrolysis of other organic fibers. It has low density, high strength, high modulus, fatigue resistance, high temperature resistance, corrosion resistance, and good conductivity. It is widely used in fiber-reinforced resin-based composite materials due to its small thermal expansion coefficient. PAN-based carbon fiber is the most important and absolute type of high-performance carbon fiber. It plays an irreplaceable role in aerospace, weapons, ships and other national defense fields. It is a strategic basic mater...

AI Technical Summary

Problems solved by technology

Since the scanning electron microscope is limited by its own resolution, it is difficult to give fine structural information

Although there are reports in the literature that FE-SEM is used to observe polyacrylonitrile carbon fibers of different systems and obtain different surface morphology features, such as granular and granular, the concept is too macroscopic to give qualitative information on structural changes.

Although it is also possible to observe cracks, inclusions and holes on the surface of carbon fibers, these are product defects and cannot be used for comparison with products from other manufacturers. In short, the information obtained by SEM lacks standard quantifiable operability

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