Application of Image Analysis to High Resolution SEM Pictures on Pitch-based Carbon Fibers

Abstract

Microstructure of mesophase pitch-based carbon fibers with high strength and high modulus has been studied by using scanning electron microscope. It has been shown that there is a qualitative correlaion between the texture of the fiber cross-section and the tensile strength of the fibers. And it is difficult to estimate the cross-section morphology quantitatively, although the electron microscopy pictures include many information. In the present paper, image analyzing process has been applies to the high resoultion scanning electron microscopy (SEM) pictures on the newly developed high strength pitch-based carbon fibers. It has been suggested that the cross-section morphology of the fibers has important contribution to the tensile strength of the fibers, and many effort has been paid to characterize the cross-section morphology of the fibers. The work station based image analyzer is applied to characterize and evaluate the cross-section structure of the fiber which has correlation with the strength. The digitization method of the SEM pictures of two mesophase pitch-based carbon fibers and computer analysis of the digitized pictures are demonstrated. Front operations of emphasis of contrast, noise reduction binary operaion and thinning, gave a vivid description of the folded structure of carbon layers so-called fibril in the cross-section of the fibers. The structures of the fibers can be characterized quantitatively with tree methods, the measure of the radius of curvature of the fibril, the 2-dimensional fast Fourier transform (FFT) analysis and fractal analysis of the cross-section structure. The results agree well with the tensile strength of the fibers.