Application of image processing techniques for analysis of nano- and micro-spaces in carbon materials

Transmission electron microscopy (TEM) is one of the most useful methods to clarify the structure in carbon materials. We developed quantitative analysis methods for the texture and structure of carbon materials containing the micro- and nano-spaces by using electron microscopy combined with image processing technique. The relations between phase transfer functions and TEM images of amorphous carbon films which consist of random arrangement of carbon layers were investigated using image processing. The similar patterns as the laser diffraction are obtained by the two-dimensional (2D) fast Fourier transform (FFT) of the digitized TEM images. The details of frequency distribution can be analyzed by integration around the central point of the power spectrum images. We applied this new technique to the study of microtexture and structure of graphite intercalation compounds (GICs). As a result of application of the frequency analysis using 2D FFT to the CuCl₂-GIC, a characteristic power spectrum pattern called streak, which was similar to the electron diffraction pattern, was obtained. The images corresponding to the specific frequencies were reconstructed by 2D inverse FFT (IFFT). The stage structure of CuCl₂-GICs was discussed by using this technique.